While there is an increasing pool of literature documenting the benefits of near-peer tutoring programme, little is known about the benefits for junior and senior peer tutors. Knowledge of the peer tutors’ perceived benefits at different levels of seniority will aid in the development of a near-peer tutoring programme that will better fulfil both curricula and personal aspirations of near-peer tutors. We, therefore, investigated the perceived benefits of participation in a near-peer tutoring programme for junior as well as senior near-peer tutors.Pre- and post-participation questionnaires were distributed to near-peer tutors after their clinical skills teaching sessions with Phase I undergraduate medical students. The Peer Tutor Assessment Instrument questionnaires were distributed to the 1) students, and to the 2) near-peer tutors (junior and senior) after each teaching and learning session for self-evaluation.p=0.03). As a whole, the near-peer tutors were more motivated  to participate in future teaching sessions but did not expect that having teaching experiences would make teaching as their major career path in the future . The senior near-peer tutors were evaluated significantly higher by the students (p=0.0001). Students’ evaluations of near-peer tutors on the domain of critical analysis was higher than self-evaluations (p=0.003).The senior near-peer tutors felt that their participation in the programme had enhanced their skills (Generally, the near-peer tutors perceived that they have benefited most in their skills enhancement and these near-peer tutors were scored highly by the students. However, senior near-peer tutors do not perceive that the programme has a lasting impact on their choice of career path. The emphasis of the General Medical Council (GMC) of the United Kingdom on the need for training medical students with teaching and learning skills encourages future doctors to become better teachers. The medical graduates must be able to ‘demonstrate appropriate teaching skills’, and as future physicians, they would need to understand the principles of medical education, be able to apply the various methods of teaching and learning, and be responsible to teach their colleagues . The iroMany studies reported that near-peer tutoring is effective, cost efficient, and is a popular educational intervention tool where students themselves are involved in imparting educational principles and knowledge. However, the capability of students to teach each other and junior students successfully relied heavily on the training of these students as tutors –10. The Literature on the effect of near-peer tutoring on the near-peer tutors themselves suggested that the programme could increase the development of self-esteem, with near-peers becoming more effective communicators and having a better understanding of learning and teaching principles –19. WhilThis study was conducted over a course of 8 months (September 2013 to May 2014) at the Clinical Skills and Simulation Centre, International Medical University (IMU), Kuala Lumpur, Malaysia.All the Year 1 and 2, Phase I, undergraduate medical students who were taught by the near-peer tutors were recruited for this study. The study population is made up of 35 junior and 16 senior near-peer tutors. For the junior near-peer tutors, a minimum of 19 students would need to be recruited as participants from the pool of near-peer tutors in the programme to achieve a 95% confidence level with an allowable error margin of ±7%. For the senior near-peer tutors, a minimum total of 15 students would need to be recruited as participants to achieve a 95% confidence level with an allowable error margin of ±0.1%.All the post-Year 3 medical students who have sat and passed their first Professional Examination were included in this study and categorised as the junior near-peer tutors. All medical students who have sat and passed their final year, newly graduated doctors waiting for their housemanship  at government hospitals, were included in this study and categorised as senior near-peer tutors. Participation was voluntary. All the junior and senior near-peers who gave informed consent were recruited for the study, and all those who did not give informed written consent were excluded.All post-Semester 5 and post-Semester 10 medical students were invited to apply for the near-peer tutoring programme. The potential near-peer tutors were invited to attend a compulsory 1 day training workshop where they were taught on adult learning and clinical skills learning. After the workshop, the potential near-peer tutors were assessed on their clinical skills teaching. They were to teach two junior medical students on a selected clinical skills, and their teaching skills were evaluated by the clinical skills lecturers. The acceptance rate of these medical students for the near-peer tutoring programme after clinical skills lecturers’ evaluation was about 80%.The near-peer tutors (junior and senior) were given pre-participation questionnaires to fill prior to their teaching experiences at the clinical skills and simulation centre. The near-peer tutors were given four clinical skills sessions each, and each teaching session lasted 2 hours. The skills taught were either physical examination skills or procedural skills. At the end of the fourth session, the near-peer tutors were given post-participation questionnaires to fill.The pre- and post-participation questionnaires (Peer Tutors Own Assessment) used in the assessment of the near-peer tutors were the adapted version of questionnaires developed by Buckley and Zamora . The queAll the Year 1 and 2, Phase I, undergraduate medical students who were taught by the near-peer tutors were given the Peer Tutor Assessment Instrument questionnaire to fill. The questionnaires were distributed to the medical students at the Clinical Skills and Simulation Centre at the end of every class taught by the near-peer tutors. The adapted version of the Peer Tutor Assessment Instrument  developeThe purpose of the study was explained to the students and consents were sought before the distribution of the hard copies of the questionnaires. The students were given 15 min each to complete the questionnaire.The study protocol was approved by the Joint Ethics Committee of the International Medical University in compliance with the Helsinki Declaration (Project Number: IMU 281/2013).t-test. The questionnaire completed by the students which assessed their acceptability of the teaching by the near-peer tutors (Peer Tutor Assessment Instrument) were evaluated using the independent t-test. In this study, a P-value of less than 0.05 was considered as statistically significant.Statistical Package for Social Sciences (SPSS) version 17.0 was used to analyse the data collected. The completed pre- and post-teaching questionnaires (Peer Tutors Own Assessment) by the near-peer tutors were evaluated using the independent as well as the paired n=34). Nineteen junior and 15 senior near-peer tutors were recruited for the study. The overall mean age ±SD of the participants was 21±2.75 years. An equal number of male and female participants were recruited (50%). Majority of the near-peer tutors did not have any previous teaching experiences (76.5%).n=19), as analysed from the post-participation scores, indicated that the near-peer tutor programme had the most impact on their motivation to do more teaching sessions in the future and to help their junior peers (5.53±0.48). The senior near-peer tutors (n=15) initially reported lesser expectation on the skills enhancement (5.07±0.80) and have shown less motivation (5.27±0.58) compared with their junior counterparts prior to joining the near-peer tutoring programme. However, in the post-participation questionnaires, the senior near-peer tutors were more inclined to report that the participation in this programme had enhanced their skills the most (p=0.03). Prior to participation, the senior near-peer tutors expected that participation in this programme were more likely to help to enhance their curriculum vitae (CV) and indicated that teaching would be a major component in their career path (4.93±1.02) when compared with the responses from the junior near-peer tutors (4.39±1.07). Post-participation, the senior near-peer tutors reported a lesser degree of agreement than previously stated: that the programme had helped to boost their career prospects (4.67±0.75).The male near-peer tutors in the pre-participation questionnaire responded that they were more likely to expect this programme to benefit them through skills enhancement (5.31±5.79) and to boost their career prospects (4.90±0.90) compared with the female near-peer tutors.n=1,053) of Phase I medical students (Year 1 to Year 3) participated and gave their evaluations on their near-peer tutors’ teaching sessions (n=34) using the Peer Tutor Assessment Instrument. Of all the near-peer tutors recruited for the study , only 13 senior near-peer tutors responded and completed the Peer Tutor Assessment Instrument after they had completed their teaching sessions. Therefore, the students’ evaluation of the two senior near-peer tutors who did not complete the self-evaluations were removed. The Phase I medical students’ (Year 1 to Year 3) respondents’ data (n=985) was analysed for this study.p=0.003) was seen in the scores given by the students compared with the near-peer tutors’ (junior and senior) self-evaluations on critical analysis.The senior near-peer tutors were evaluated significantly higher in all the domains assessed  when compared with their junior counterparts. There were no significant differences in the comparison of the self-evaluation scores of the senior and the junior near-peer tutors in all the domains assessed. Both groups scored lowest for the domain on critical analysis although the senior near-peers scored themselves slightly higher than the junior near-peers. Significant difference . Previous reports have identified that participation in a teaching programme such as this was perceived by near-peer tutors to be beneficial in the revision of their knowledge and provided them with an opportunity to reflect on their shortcomings, especially with regards to their knowledge depth. Additionally, participation in the programme helped to substantially provide them with a deeper level of understanding concerning the content of the knowledge taught , 26. AnoAlthough in general the near-peer tutors did see the importance of teaching and were more motivated to take up future teaching sessions, the senior near-peers did not feel that the programme had any effect on their choice of career paths or have any impact on the enhancement of their CV. It is therefore important to create more awareness of this career option by encouraging medical students to interact with more clinical teachers, introduce more formal teaching posts, and to expose them to this career path –29.The near-peer tutors’ scores on the pre- and post-participation questionnaires were on the higher end of the Likert scale with an average mean of five out of six points. The voluntary nature of the recruitment of near-peer tutors for this programme would have drawn in near-peer tutors that were highly motivated to teach when they first participated. Similarly, Wadoodi and Crosby did highlight in their article that voluntary recruitment processes rather than selecting those who are academically sound would draw and create opportunities for participation from potential near-peer tutors who could be academically weak but truly motivated to improve their clinical skills . There wAlthough the students scored their near-peer tutors very highly on the critical thinking skills, the near-peer tutors did not score themselves as high. This finding suggests that either some of the near-peer tutors have set possibly higher standards for themselves or some did not perform the teaching steps related to the domain of critical thinking. Although not reported in relation to near-peer teaching, there are contradicting reports from the literature on students’ ability to critically think. These reports suggest that in higher education, critical thinking skills either improve as the students increase in seniority –34 or thn=985) in the evaluation of their near-peer tutors and the consistency of high scores across the various near-peer tutoring sessions also suggested that students benefited from learning clinical skills from their near-peer tutors. Likewise, the high self-evaluation scores of their own teaching reflected that the near-peer tutors also have much confidence in the delivery of their teaching sessions. In fact, in some studies, it had been shown that near-peer tutors benefited more academically and cognitively when compared with their students (In the overall results, the students evaluated their near-peer tutors highly, indicating that students accept and recognise the teaching skills of the near-peer tutors. The large number of students’ response (students , 14, 38.students –41. Thisstudents , 43, in students .The limitations of this study are the relatively small sample sizes of near-peer tutors and the subjectivity of scorings of the questionnaires given due to the probable differences in the interpretation of the test items by the near-peer tutors as well as the students. Therefore, the results should be interpreted within these limitations. However, the results do imply that the near-peer tutoring programmes benefited the near-peer tutors equally regardless of their seniority but had not changed their perceptions of incorporating teaching as a long-term career consideration in the future. Efforts should be taken to optimise the exposure to teaching in medical schools to create awareness and interest to this career path. Although the near-peer tutors reported that the near-peer tutoring programme have enhanced their skills and the students’ responses stated likewise, there is a need to prove the effectiveness of this programme where their actual performance may need to be formally evaluated by faculty members and further analysed.Both groups of near-peer tutors equally benefited from the near-peer tutoring programme regardless of their seniority. Near-peer tutoring enhanced the skills domain of the near-peer tutor but formal analyses of their performances are needed to prove its effectiveness. The teaching skills of the near-peer tutors were evaluated highly by the students; however, the senior near-peer tutors were rated significantly higher. Although near-peer tutors did see the importance of teaching, the programme did not have any influence on their choice of future career paths for the senior near-peer tutors. Future studies on junior doctors’ perceptions of teaching would be useful to determine if there is a need to nurture the passion for teaching at an early stage in medical school.


We describe a complex congenital pelvic AVM with multiple feeding arteries arising from the side branches of the right internal iliac artery and a single draining vein in a male patient. Concomitant transarterial and transvenous embolization with a new liquid embolic agent Squid-12 and metallic coils enabled a complete embolization at a single session. Squid-12 is composed of ethylene vinyl alcohol copolymers and its lower viscosity makes it a promising agent for the treatment of AVMs. The patient showed prompt resolution of the symptoms and complete devascularization of the AVM lesion was persisted on the 1-month control angiography. The patient was asymptomatic on the 6th month follow-up. Pelvic arteriovenous malformations (AVMs) are rare vascular lesions, which are characterized by multiple abnormal communications between the arterial and venous systems without an intervening capillary network –3. In thSurgical treatment of pelvic AVMs either by ligation of the afferent arteries or by excision of the nidus has been reported to carry the risks of massive intraoperative hemorrhage, surrounding organ injury with high rates of recurrence and incomplete removal of the AVM nidus , 7. FurtA 46-year-old man with no significant medical history presented with progressively increasing pelvic pain for 1 year and exacerbation for 1 month. Physical examination was normal. Laboratory data showed no abnormality. Ultrasonography of the pelvic region revealed a hypoechogenic mass in the right lower quadrant. Pelvic magnetic resonance imaging (MRI) revealed asymmetric multiple fine striations in the right pelvic cavity and dilation of the right internal iliac vein and artery. Computed tomography angiography (CTA) demonstrated a large pelvic AVM with multiple feeding arteries arising from the side branches of the right internal iliac artery especially from the anterior trunk which were draining into right internal iliac vein through a large venous pouch . BecauseThe procedure was performed after obtaining a written informed consent of the patient and under general anesthesia. Left common femoral artery and left common femoral vein were punctured simultaneously using the Seldinger technique and 6 F long introducer sheaths  were positioned. 5 F cobra catheters  were inserted to access the right internal iliac artery and vein. A pelvic digital subtraction angiography (DSA) was performed. DSA confirmed the findings of the CTA and revealed a large pelvic AVM with multiple feeding arteries originating from the side branches of the right internal iliac artery especially from the anterior trunk. Multiple feeding arteries shunted a single large venous pouch and drainage occurred via the right internal iliac vein .Feeding arteries, suitable to microcatheter insertion were superselectively catheterized using a 2.7 F microcatheter . These feeding branches were embolized by injection of a total of 10.5 mL Squid-12 Figures . InjectiNext, a 2.7 F microcatheter was positioned in the venous pouch through the cobra catheter placed via the venous access. Contrast injection confirmed the position of the microcatheter in the venous pouch of the AVM . SubsequA follow-up DSA was performed 1 month after the procedure and complete devascularization and thrombosis of the AVM lesion were confirmed . The cliCongenital AVMs of the pelvis are rare and challenging lesions. The natural history of pelvic AVMs is variable; they can remain asymptomatic for years and once they become symptomatic they may demonstrate rapid enlargement , 6. PresSurgical treatment of AVMs has been reported to be unsuccessful as surgical eradication of the nidus of an AVM is rarely possible. Surgical treatment options include ligation of the feeding arteries and excision of the lesion. Many authors agree that simple ligation of afferent arteries has no value, since new collaterals develop rapidly to bypass the ligatured vessels . SurgicaBecause of the rarity of the pathology there is not a consensus on a standardized endovascular treatment strategy of these lesions. Embolization of the feeding arteries for the treatment of pelvic AVM lesions has been reported as case reports and series; relatively high clinical and radiological recurrence have been observed after transarterial embolization alone using various embolic materials , 10, 11.It is a topic of debate that transarterial or transvenous embolization should be performed first. We did not prefer transvenous embolization as a first procedure because, first of all, stagnated arterial flow after transvenous occlusion impairs nidal penetration of liquid embolic agent. Secondly, transvenous embolization has a theoretical risk of increased pressure in the nidus during the time which passed till the arterial embolization has been completed which may provoke nidus rupture especially for large AVM lesions with high volume flow.Various embolic materials such as metallic coils, polyvinyl alcohol (PVA) foam particles, rapidly polymerizing acrylic adhesives, absolute ethanol, and ethylene vinyl alcohol copolymers have been used for the treatment of AVM lesions , 10, 12.Liquid embolic agents have been reported to be useful for AVM treatment , 12, 13.Safety and efficacy of EVOH for the treatment of extracranial AVMs have previously been described in literature , 10. It We performed a follow-up DSA one month after the procedure. CTA has been used for follow-up after treatment of such lesions by many authors. CTA has the advantage of being a noninvasive modality; however CT artefacts of metallic coils and Squid may prevent visualizing minimal residual AVM vascularization. Therefore, a follow-up DSA was decided to be sure of complete devascularization of the AVM. Furthermore, high radiation exposure is another disadvantage of the CTA. All AVM lesions should be followed up for long periods and we planned annual clinical and iliac Doppler follow-ups to avoid radiation exposure.In conclusion, pelvic AVM is a rare form of congenital vascular malformations with serious complications and variable hemodynamics. We performed transarterial and transvenous embolization concomitantly using Squid-12 and detachable metallic coils for embolization of a pelvic AVM and achieved complete cure with a single session. This technique may be an effective option when the AVM lesion consists of a single draining vein and multiple feeding arteries, and it may minimize the need for subsequent procedures. The ease of use and good penetration capability of this new liquid embolic agent make it a promising agent and it merits further clinical study.


Freezing has become the predominant measure used in rodent studies of conditioned fear, but conditioned suppression of reward-seeking behavior may provide a measure that is more relevant to human anxiety disorders; that is, a measure of how fear interferes with the enjoyment of pleasurable activities. Previous work has found that an isolated presentation of a fear conditioned stimulus (CS) prior to extinction training  results in a more robust and longer-lasting reduction in fear. The objective of this study was to assess whether the retrieval + extinction effect is evident using conditioned suppression of reward seeking, operationalized as a reduction in baseline licking (without prior water deprivation) for a 10% sucrose solution. We found that, compared to freezing, conditioned suppression of reward seeking was much more sensitive to fear conditioning and far less responsive to extinction training. As in previous work, we found that retrieval + extinction reduced post-extinction fear reinstatement when measured as freezing, but it did not reduce fear reinstatement when measured as conditioned suppression. This suggests that there is still residual fear following retrieval + extinction, or that this procedure only modifies memory traces in neural circuits relevant to the expression of freezing, but not to the suppression of reward seeking. Freezing, or becoming motionless in the presence of fear-evoking stimuli, is one of the innate defensive reactions of rats and other rodents, and it has become the predominant measure—often the only behavioral measure—used in studies of conditioned fear/threat. However, historically this was not always the case. For several decades following its introduction by Estes and Skinner , conditiEventually, the numerous advantages offered by conditioned freezing led to its dominant use in studies of Pavlovian fear conditioning. Namely, freezing behavior can be directly observed without the need for extensive prior operant training or the accompanying states of physiological deprivation required to elicit robust operant responding. Such a simplified preparation is especially appealing for uncovering the neurobiological mechanisms specific to fear learning because one does not need to control for the neural effects of altered motivational states or concurrent appetitive learning. However, in recent years, there has been increasing interest in translating findings from Pavlovian fear conditioning to the treatment of human anxiety disorders. For this objective, conditioned suppression may be more relevant than freezing to the way that human beings experience fear, i.e., as something that interferes with the enjoyment of pleasurable activities , resulted in a persistent attenuation of fear memories, leaving them less susceptible to return of fear as evidenced by several measures, including resistance to fear reinstatement following unsignaled shock presentations  arrived in our animal facility at approximately 50 days of age and were pair-housed (2 per cage). Rooms were maintained at steady temperature (21 ± 1°C) and a 12-12 light-dark cycle (lights on at 7:00 and off at 19:00). Except for one 24-h period of water deprivation as described below, food and water were provided https://github.com/jashu/graphic-state-munging.Rats were conditioned and tested in a Habitest Modular System (Coulbourn Instruments) equipped with metal rod flooring connected to a shock generator, a speaker connected to a tone generator, and an optical lickometer that continuously monitored licking of an attached water bottle. Rats were videoed by overhead cameras. Graphic state software controlled stimulus presentations and recorded lickometer data. Raw data files from these sessions were exported as text files, and stimulus-dependent changes in licking behavior were quantified using a custom-written R package, “lickometer,” which can be downloaded from A schematic of the experimental design is shown in Figure Following 1 week of acclimation after arrival at our facility, rats underwent 3 daily sessions of habituation to the conditioning chamber to establish a baseline rate of drinking Figure , each sen = 16 per group) were made based on cage-wise matching of baseline drinking behavior: after calculating the mean baseline drinking for each cage pair, cages were matched according to these means. This was done in order to assign cage mates to the same experimental condition while minimizing differences in baseline drinking motivation between the Ext and Ret + Ext groups.On Day 4 (the day following the last habituation session), rats underwent fear conditioning. Rats received 3 conditioning trials of a tone (5 kHz for 20 s) co-terminating with a foot shock (0.7 mA for 0.5 s) separated by a variable intertrial interval (ITI) of 1–5 min. This was followed by 2 days of extinction , rats were returned to the acquisition context for 4 min, during which time the Ret + Ext group (but not the Ext group) received a single 20 s tone. Rats were then returned to their home cages for 1 h and then reintroduced to the same context for extinction training, consisting of tone-alone presentations of the same duration and ITI as experienced in acquisition until both Ext and Ret + Ext groups had heard a total of 18 tones. On Day 7  repeated measures ANOVA, with Group (Ext vs. Ret + Ext) as the between-subjects measure and Session, Trial, and CS as within-subject measures. Session was included to evaluate between-session extinction, operationalized as increased drinking between the first and second extinction sessions. Trial was included to evaluate within-session extinction, operationalized as increased drinking over the 18 trials. CS was included to evaluate the specificity of fear acquisition and extinction to the tone CS vs. contextual cues. For the above ANOVA, the effect of CS was operationalized as a difference between drinking during the tone vs. the 20 s preceding the tone, in order to match the CS and pre-CS in terms of temporal proximity and duration. However, one limitation of pleasure-motivated (as opposed to thirst-motivated) drinking is that it is more erratic, i.e., characterized by many spontaneous starts and stops. Thus, aggregating over longer intervals may provide a more reliable index of fear by averaging out this source of noise. Therefore, we also conducted a separate 2 × 2 × 18  repeated measures ANOVA of contextual extinction alone, in which drinking was averaged over each ITI.Based on previous work, we did not expect the Ret + Ext manipulation to result in significant group differences In addition, we used LOESS  to fit separate extinction curves  within each Group × Session × CS cell. This nonparametric method constructs a nonlinear “smooth” of the drinking data over time, using local polynomial regression fitting (which requires no prior assumptions about the distribution of the data or the shape of the curve to be fit) to extract signal (systematic variation) from noise (random variation). Plots of these LOESS smooths provide an elegant way to visually compare differences in extinction curves. Moreover, confidence intervals can be constructed for the curve fits themselves, providing a gauge for when a curve significantly diverges from a reference point  or from another curve without the need for multiple statistical tests at multiple time points.Long-term changes in fear expression caused by fear conditioning, Ext vs. Ret + Ext, and reinstatement were assessed using data from the first tone presentation 24 h after the end of each of these training protocols. Separate but parallel ANOVAs were applied to the drinking and freezing data using a 2 × 3 × 2 design (Group × Session × CS), with group as a between-subject variable and session (post-acquisition vs. post-extinction vs. post-reisntatement) and CS (context vs. tone) as within-subject variables. Note that we also performed an analysis that included repeated measures of trial, which did not result in any substantive insights beyond the analysis of just the first trials. Moreover, our experimental manipulation was introduced following the first post-acquisition trial , and the first trial of an LTM session following extinction or reinstatement training is the most likely to show spontaneous recovery or savings, respectively. For all these reasons, we chose to confine our analysis of LTM to the first trial.F statistic to calculate p-values ; rather, we used random permutations to generate an empirical F distribution as described by Manly /(n + 1), where r is the number of permutations that resulted in an F statistic greater than or equal to the original F statistic, and n is the total number of permutations.As can be seen in Figures by Manly . The obsp-values for these data as well. Both theoretical and empirical p-values are given in the ANOVA summary tables (Tables 4). In the case of significant interactions involving group, simple effects of group were calculated using analogous permutation tests for group-mean differences within each level of the interacting variables (Table 5). Likewise, for consistency, we calculated the 95% confidence intervals surrounding the LOESS curves in Figure Although the freezing data were not characterized by such severely skewed distributions, for consistency, we calculated empirical s Tables –4. In thFigures were generated using the ggplot2 package for R Wickham, . Data weF statistic used to calculate p-values. Therefore, we generated an empirical distribution of the F statistic using unrestricted permutation of the raw data within subjects and permutation of the group labels (Ext vs. Ret + Ext) between subjects. For consistency across analyses, we did the same for the freezing data as well. Both types of p-values, theoretical and empirical, are given in Tables 5. As expected, the two methods yielded highly consistent p-value estimates for the freezing data, to within rounding error of the hundredth decimal place. To our surprise, the two methods were also highly consistent for the drinking data. We caution that this result should not be taken as evidence that one can always ignore the presence of many zero values, which have the potential to exaggerate or diminish statistical effects depending on the proportion of zeros in each group and the direction of mean differences  = 6.5, p < 0.001. However, approximately 60% of rats were drinking at a baseline rate within the range shown by rats after water deprivation (not counting one rat that showed zero drinking under water restriction). Figure t(31) = 4.9, p < 0.001. Recall that water restriction was implemented only during the first exposure to the apparatus, so this result does not reflect an effect of water restriction so much as an effect of extensive habituation to the apparatus; in other words, we do not know whether water deprivation would have resulted in higher maximum drinking rates had it been implemented for the entire experiment. However, the important point here is that most rats were spontaneously motivated to drink a sweetened solution at a substantial rate without the need for water restriction. Note that there was no significant group difference in the maximum drinking rate using a Welch two sample t-test, t(29.4) = 0.2, p = 0.82, and no significant group difference in the latency to reach maximum drinking, t(29.3) = 0.6, p = 0.58.Figure p < 0.001), indicating that drinking during the 20 s preceding the CS showed a significantly greater between-session increase than did drinking during the tone CS. Plots of extinction curves show that while there was a slight between-session increase in drinking during the tone CS . Plots of extinction curves show a gradual increase from an initially complete suppression of drinking during the first extinction session , indicating that the relative difference in drinking time during tone vs. context changes as a function of training. Both tone and context showed complete conditioned suppression following acquisition . The Ret + Ext group showed a greater reduction in freezing between post-acquisition . Simple effects tests of the interactions (Table p < 0.05) was only evident for the tone CS following reinstatement. Note that, based on previous findings, this was the only condition in this experiment under which the Ret + Ext group was hypothesized to show less post-reinstatement freezing.Table n Figure  and postn Figure  and postn Figure . This efWe previously reported that an isolated presentation of a fear CS prior to extinction training  results in a more robust and longer-lasting reduction in fear as measured by conditioned freezing after reinstatement. In the present study, we assessed whether the retrieval + extinction effect is evident when conditioned suppression is used to measure fear. Freezing has become the predominant measure used in rodent studies of conditioned fear, but conditioned suppression may provide a measure that is more relevant to human anxiety disorders; that is, a measure of how fear interferes with the enjoyment of pleasurable activities. As in previous work, we found that retrieval + extinction reduced fear reinstatement after extinction when measured as freezing, but it did not reduce fear reinstatement when measured as conditioned suppression. Our results suggest that there is still residual fear following retrieval + extinction, or that this procedure is only modifying memory traces in neural circuits relevant to the expression of freezing but not the expression of conditioned suppression.Bouton and Bolles  reportedOur results show that, not surprisingly, rats consume sweetened water at a higher rate when they have been water deprived, but most were still motivated to drink without prior deprivation because presumably the sweet solution was rewarding in itself. When the survival imperative associated with thirst was no longer a factor, we observed a sharp dissociation between freezing levels and drinking behavior. Whereas fear acquisition levels in terms of freezing were highly variable, acquisition of conditioned suppression was both absolute and invariant. Two extinction sessions were required before some rats began to drink during the tone CS. However, most responded to the extinction session by drinking substantially during the ITI and drinking minimally during the CS. This behavior may have more translational relevance to fear-related psychopathology, reflecting that fear-associated stimuli can continue to elicit sufficient wariness and vigilance to disrupt normal life. The complete extinction of these fear memories would seem to pose a much greater challenge than the extinction of freezing, which may represent only a diminution of fear.To this end, we were interested to see if the Ret + Ext paradigm, which has been proposed to lead to a disruption in the reconsolidation of fear memories  has been reported to play a minimal role in conditioned suppression , fear conditioning appears to cause far more indelible behavioral changes. All of the rats resumed drinking by the end of the second extinction session, but they confined their drinking almost entirely to the time between tones .The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Patients who died had an increased sequential organ failure assessment score and need for vasopressors. Bacillus anthracis infection among persons who inject drugs resulted in a 28% death rate. To compare nonsurvivors and survivors, we obtained data on 11 nonsurvivors and 16 survivors. Time from B. anthracis exposure to symptoms or hospitalization and skin and limb findings at presentation did not differ between nonsurvivors and survivors. Proportionately more nonsurvivors had histories of excessive alcohol use (p = 0.05) and required vasopressors and/or mechanical ventilation . Nonsurvivors also had higher sequential organ failure assessment scores (mean + SEM) . Antibacterial drug administration, surgery, and anthrax polyclonal immune globulin treatments did not differ between nonsurvivors and survivors. Of the 14 patients who required vasopressors during hospitalization, 11 died. Sequential organ failure assessment score or vasopressor requirement during hospitalization might identify patients with injectional anthrax for whom limited adjunctive therapies might be beneficial.In Scotland, the 2009 outbreak of  Medscape, LLC is pleased to provide online continuing medical education (CME) for this journal article, allowing clinicians the opportunity to earn CME credit. This activity has been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education through the joint providership of Medscape, LLC and Emerging Infectious Diseases. Medscape, LLC is accredited by the ACCME to provide continuing medical education for physicians.TMAMA PRA Category 1 Credit(s). Physicians should claim only the credit commensurate with the extent of their participation in the activity.Medscape, LLC designates this Journal-based CME activity for a maximum of 1.0 http://www.medscape.org/journal/eid; (4) view/print certificate.All other clinicians completing this activity will be issued a certificate of participation. To participate in this journal CME activity: (1) review the learning objectives and author disclosures; (2) study the education content; (3) take the post-test with a 75% minimum passing score and complete the evaluation at Release date: August 15, 2014; Expiration date: August 15, 2015Upon completion of this activity, participants will be able to:Distinguish patient factors associated with a higher risk for mortality from injection anthraxEvaluate variables at patient presentation associated with a higher risk for death from injection anthraxAssess medical treatment variables associated with a higher risk for death from injection anthraxAnalyze hospital events associated with a higher risk for mortality from injection anthrax.Karen L. Foster, Technical Writer/Editor, Emerging Infectious Diseases. Disclosure: Karen L. Foster has disclosed no relevant financial relationships.Charles P. Vega, MD, Clinical Professor of Family Medicine, University of California, Irvine. Disclosure: Charles P. Vega, MD, has disclosed the following financial relationships: served as an advisor or consultant for McNeil Pharmaceuticals.Disclosures: Malcolm Booth, MBChB, FRCA, MPhil, FFICM; Lindsay Donaldson, MB ChB, FRCA, FFICM; Xizhong Cui, MD, PhD; Junfeng Sun, PhD; Stephen Cole, BSc(Hons), MBChB, FRCA, FFICM, FRCP; Susan Dailsey, MBChB; Andrew Hart, BSc, MBChB, MD, PhD, MRCS, AFRCS, FRCS(plast); Neil Johns, MBBS, BSc; Paul McConnell, MBChB(Hons), FRCA, EDIC, FFICM; Tina McLennan, MBChB, FRCA; Benjamin Parcell, MBChB, FRCPath; Henry Robb, MBChB, FRCA, MS, FFICM; Charles Wallis, MBChB, FRCA, FFICM; and Peter Q. Eichacker, MD, have disclosed no relevant financial relationships. Benjamin Shippey, FRCPE, FFICM, FRCA, BM, BS, BMedSci, has disclosed the following relevant financial relationships: served as an advisor or consultant for and received grants for clinical research from Aircraft Medical. Malcolm Sim, BSc(Hons), MBChB, FRCA, FRCP, FFICM, EDIC, has disclosed the following relevant financial relationships: received grants for clinical research from Roche/Wyeth Pharmaceuticals Inc. Bacillus anthracis infection in humans has typically been classified as cutaneous, gastrointestinal, or inhalational on the basis of the bacterium’s route of entry   has published epidemiologic analyses of the 2009–2010 outbreak  and the Office of Human Subjects Research from the Clinical Center at the National Institutes of Health  exempted the study from formal review.We developed an electronic questionnaire that requested information in several areas. These were: general information ; current illness; data at the time the patient sought care, including skin and limb findings, vital signs, laboratory findings, and diagnosis ; medical and surgical treatments at the time the patient sought care or later  score; and outcomes, including survival, time in the intensive care unit (ICU), and total time in hospital.During this anthrax outbreak, HPS identified 13 hospitals to which the 47 patients with confirmed anthrax were admitted (>14) of questionnaires provided definitive data. SOFA score was calculated as previously described for each patient for whom data were obtained within the initial 24 hours after they sought care  were examined with 1-way ANOVA .A variable was reported on only if >50%  times (days) from exposure to onset of symptoms and from onset of symptoms to hospital admission were 1 (0–4) and 2 (2–4), respectively, and these did not differ significantly between survivors (1 [0–4.5] and 3 [2–5] days) and nonsurvivors (1 (0–2] and 2 [2– 2] days)  .+ SEM) age of patients was 34.5 + 1.7 years. Nonsurvivors tended to be older than survivors . The proportion who were male did not differ significantly . Although history of excessive alcohol use was higher in nonsurvivors than in survivors , tobacco use and suspected injection sites  and routes (intravenous or intramuscular) of contaminated drug injection did not differ significantly . HIV infection status was available for only 10 patients (4 nonsurvivors), and hepatitis C infection status was available for only 12 patients (5 nonsurvivors). One survivor was HIV positive, and 4 survivors and 5 nonsurvivors had histories of hepatitis C virus infection. Although the questionnaire requested other medical history , these data were not provided in sufficient numbers for analysis.Mean (Eleven (69%) survivors and 2 (18%) nonsurvivors had only localized skin or limb symptoms ; 5 (31%) survivors and 4 (36%) nonsurvivors had both localized and generalized symptoms , and 0 survivors and 5 (45%) nonsurvivors had only generalized symptom . The pro<0.01) (+ SEM), including diastolic blood pressure (68 + 4 vs. 61 + 5 mm Hg), heart rate (111 + 5 vs. 118 + 8 beats per minute), and capillary refill (2.6 + 0.4 vs. 3.6 + 0.5 seconds) did not differ significantly. Four nonsurvivors, but only 1 survivor, had a temperature <36°C when they sought care, whereas 1 nonsurvivor and 7 survivors had temperatures >38°C. Also, whereas 4 nonsurvivors had systolic blood pressures <90 mm Hg, no survivor did. The Glasgow coma score recorded during the initial 24 hours was lower for nonsurvivors than for survivors (p = 0.008)   , but oth= 0.008) . The profor all) .<0.05) . All patients were initially treated with at least 1 antibacterial drug  of antibacterial drugs received differed significantly between survivors and nonsurvivors (p>0.06). Among survivors, 75% received ciprofloxacin and 88% received clindamycin; among nonsurvivors, 55% and 64% received these drugs, respectively. More nonsurvivors than survivors received vasopressors, oxygen support, mechanical ventilation, and corticosteroids  (<0.003) , but ial drug . Neitherp<0.002)  but not p<0.002) . SOFA sc(<0.003) .B. anthracis for the 47 confirmed anthrax cases has been published   . We had Proportionately more nonsurvivors than survivors received ICU care  . The medWe found no significant difference in the proportions of survivors and nonsurvivors who required surgery during hospitalization  or who required >1 surgery (7 [64%] vs. 4 (80%); p = 0.52) or in the median (IQR) time (days) to initial surgery  . Even whB. anthracis sepsis, 2 patients; necrotizing fasciitis related to B. anthracis, 1; sepsis and hemorrhagic meningitis with B. anthracis infection, 2; subarachnoid hemorrhage, 1; and myocardial infarction, 1.Receipt of packed erythrocytes, fresh frozen plasma, cryoglobulin, and platelets; renal replacement therapy; and pleural or peritoneal drainage did not differ significantly between survivors and nonsurvivors . For 9  and C-reactive protein; higher international normalized ratio; and lower sodium and albumin levels and platelet counts. During hospitalization, all nonsurvivors required vasopressor and ICU support, whereas only 3 and 7 survivors, respectively, required these. SOFA scores were substantially higher in nonsurvivors than survivors. Thus, assessing the need for aggressive cardiopulmonary support or determining a score like SOFA for patients with injectional anthrax can help identify those for whom prognosis is particularly poor and more aggressive therapy is needed.Our review of 27 confirmed cases of B. anthracis infection in PWID, we found a higher incidence of excessive alcohol use among nonsurvivors than survivors  might have been informative as well. Third, although 1 survivor and 1 nonsurvivor described headache, using the Glasgow coma scale to assess neurologic status might not have captured other patients with this symptom, a possible manifestation of underlying meningeal infection. Fourth, comparisons of therapies administered to survivors and nonsurvivors later than when they initially sought care might have been confounded by patients’ length of hospitalization; however, data were insufficient to analyze the influence of this variable. Finally, autopsy findings were available only for 7 patients.This study has limitations. First, data were collected B. anthracis infection among PWID in Scotland was considered over at the end of 2010  credits are accepted in the US as evidence of participation in CME activities. For further information on this award, please refer to http://www.ama-assn.org/ama/pub/about-ama/awards/ama-physicians-recognition-award.page. The AMA has determined that physicians not licensed in the US who participate in this CME activity are eligible for AMA PRA Category 1 Credits™. Through agreements that the AMA has made with agencies in some countries, AMA PRA credit may be acceptable as evidence of participation in CME activities. If you are not licensed in the US, please complete the questions online, print the certificate and present it to your national medical association for review.To obtain credit, you should first read the journal article. After reading the article, you should be able to answer the following, related, multiple-choice questions. To complete the questions (with a minimum 75% passing score) and earn continuing medical education (CME) credit, please go to 1. You are seeing a 33-year-old man in the emergency department. He complains of severe pain and redness on his left upper extremity after injecting heroin into an antecubital vein yesterday. A brief examination of the area reveals 8 cm of erythema, induration, and calor, with a central necrotic area. You consider whether this patient has injection anthrax; you also consider his prognosis. Which one of the following patient factors was most associated with a higher risk for mortality related to injection anthrax in the current study?A. Younger ageB. Male sexC. Excessive alcohol useD. Cigarette smoking2. Which one of the following variables at patient presentation was most associated with a higher risk for mortality in the current study of patients with injection anthrax?A. Temperature less than 36˚CB. Heart rate greater than 115 beats per minuteC. Respiratory rate less than 12 breaths per minuteD. Skin lesions on the upper extremity vs lower extremity3. Which one of the following statements regarding treatment and mortality outcomes related to injection anthrax in the current study is most accurate?A. Rates of initial diagnosis with Bacillus anthracis infection were similar among nonsurvivors and survivorsB. Compared with survivors, nonsurvivors were less likely to receive antibiotics at hospital admissionC. Compared with survivors, nonsurvivors were less likely to receive ciprofloxacin D. Nonsurvivors and survivors were equally likely to require surgery4. Which one of the following hospital events was more common among nonsurvivors vs survivors in the current study?A. Application of anthrax immune globulinB. Excessive bleeding during surgeryC. Longer duration until initial surgeryD. Initiation of renal replacement therapy


Annealing S-hyperdoped Sireduces the sub-band gap absorptance and the concentration ofS2− species, but significantly increases theconcentration of larger S clusters [polysulfides]. The Si K-edge XANES spectra show thatS hyperdoping in Si increases (decreased) the occupied (unoccupied) electronicdensity of states at/above the conduction-band-minimum. VB-PES spectra evidentlyreveal that the S-dopants not only form an impurity band deep within the band gap,giving rise to the sub-band gap absorption, but also cause the insulator-to-metaltransition in S-hyperdoped Si samples. Based on the experimental results and thecalculations by density functional theory, the chemical state of the S species andthe formation of the S-dopant states in the band gap of Si are critical indetermining the sub-band gap absorptance of hyperdoped Si samples.The correlation between sub-band gap absorption and the chemical states andelectronic and atomic structures of S-hyperdoped Si have been extensively studied,using synchrotron-based x-ray photoelectron spectroscopy (XPS), x-ray absorptionnear-edge spectroscopy (XANES), extended x-ray absorption fine structure (EXAFS),valence-band photoemission spectroscopy (VB-PES) and first-principles calculation. S2 Eg = 1.12 eV)that is hyperdoped with chalcogens  beyond the equilibrium solubility limitexhibits sub-band gap light absorption, making it a suitable material for Si-basedinfrared (IR) and photovoltaic applications1234366et al.K-edge extended x-ray absorptionfine structure (EXAFS) studies of Se-hyperdoped Si samples and found that duringannealing, the Se precipitated at grain boundaries and formed non-IR absorbing silicondiselenide (SiSe2) precipitates, reducing the sub-band gap absorption. Theresults of an EXAFS study revealed that thermal treatment facilitated the return ofSe-hyperdoped Si samples to equilibrium atomic structural order with a reduction of thesub-band gap optical absorption. An Si L3,2 x-ray emissionspectroscopic (XES) study of S-doped Si samples [up to 0.7 atomic percentage(at.%)]EVBM), which scaled linearly with Sconcentration associated with the S-dopant, and the line-shape of the S-dopant featurechanged across the IMT. The annealing of the S-doped Si samples reduced the inducedemission intensity, which was associated with the quenching of sub-band gapabsorption45Silicon  species, in an absorbing sample with ahigh (~87%) sub-band gap and thermal annealing, increases the formation ofnon-IR absorbing larger S clusters [polysulfides].The results of XANES and VB-PES reveal that doping with S modifies the electronicstructures of the hyperdoped Si samples. A Si K-edge EXAFS study further showsthat S-hyperdoping induces high structural disorder around Si atoms. However, thenearest-neighbor (NN) bond length of Si-Si remains constant as the doping concentrationof S is varied. There is no clear evidence that thermal annealing at500 °C and 700 °C yields Si-Sprecipitates, presumably owing to the decrease in the sub-band gap absorption inchalcogen hyperdoped Si samples. Based on our experimental measurements, the chemicalstate of the S species and the S-dopant states in the band gap of Si are critical indetermining the sub-band gap absorption of hyperdoped Si samples. A first-principlescalculations using DFT method supports experimental results as well as the occurrence ofthe IMT at/above a critical concentration of S dopants in the hyperdoped Si samples. Ourstudy provides clear evidence of the active chemical state of S species on the surfaceof Si and S-dopant states deep in the band gap of Si, are responsible for the sub-bandgap absorption in the hyperdoped Si samples.This study investigates S-hyperdoped Si samples using synchrotron-based techniques suchas x-ray photoelectron spectroscopy (XPS), x-ray absorption near-edge spectroscopy(XANES), EXAFS, valence-band photoemission spectroscopy (VB-PES) and first-principlesDFT calculations. The XPS reveals that a high concentration of S, particularly asS6 gas increased. The needle-like microstructure of thesamples prepared with a gas pressure of 500 Torr became increasinglyporous as the annealing temperature increased from 500 °C to700 °C. 679126 gas pressure and annealing temperature, can be foundelsewhere12131415p core-level XPS spectra ofS-hyperdoped Si samples prepared at 100 Torr and 500 Torr,and the 500 Torr sample that was further annealed at500 °C and 700 °C, respectively. TheS 2p core-level XPS spectrum of powder S is included for comparison. The XPSspectra of all the samples were deconvoluted into several features and 2− (monosulfide),S22− (disulfide),Sn2− and S0 are located at ~161.2 eV,162.3 eV, 163.3 eV and 164.4 eV,respectively1718192032− (sulfite) and/orSO42− (sulfate)p spectrum of the S-hyperdoped Si samples is shifted to a higher BE(0.3–0.5 eV) than that of pure S and their characteristicfeatures are broader, owing to a change in the chemical environment of the S-dopantin the Si matrix. Also, S species in the sample have more chemically inequivalentatoms than the reference S2−(monosulfide) feature as compared to the 100 Torr sample. On the otherhand, the annealed 500 Torr samples  have barelyvisible S2− (monosulfide) feature p core-level XPS results[2− and S22−species are 9.1% and 15.4%, respectively and that of theSn2− species is 36.0%. Notably, thatS0 andSO32−/SO42−species generally do not absorb energy in the IR range232−, 21.8%S22− and 24.6%Sn2− species. Annealing of the500 Torr sample at 500 °C(700 °C) reduced the concentrations of theS2− and S22−species to 4.6% (2.3%) and 20.8% (22.7%), respectively, but increased theconcentration of Sn2− to 34.5% (36.6%).Interestingly, the difference between the percentages ofS2− and Sn2−species is ~10% in 500 Torr, 17% in 100 Torr andmuch larger ~30% in the annealed samples. The percentage ofS2− species is higher in the 500 Torrsample than in the other S-hyperdoped Si samples. However, annealing the500 Torr sample at 500 °C or700 °C considerably increases the number of larger Sclusters (Sn2−) in relative to that of500 Torr sample. However, annealing does not affect much theS22− species concentration. Mo etal.n2−(n > 2), changing the optical properties as thegeometry and coordination of S atoms get modified in the clusters. The results ofthe S 2p core-level XPS spectra provide clear evidence that the500 Torr sample with the largest (~87%) sub-band gapabsorption contains the highest concentration of S-dopant, especiallyS2− species, and that thermal annealing increases thepercentage of larger clusters Sn2− relative tothat of S22− (Tab. SI), reducing the sub-bandgap absorptance to 23% and 7% for the 500 °C and700 °C samples, respectively. Therefore, a clearrelationship is obtained between the chemical states of the S species and thesub-band gap absorptance of the S-hyperdoped Si. The classification of theIR-absorbing S species reveals that S2− are the opticallyactive species and thermal annealing increases the number of non-IR absorbing largerS clusters  in S-hyperdoped Si samples. TheS22− species remain optically absorbingand concentration of these species does not change much after thermal annealingTo obtain a correlation between the optical properties and the concentration of theS-dopant in the S-hyperdoped Si samples we have plotted the average sub-band gapabsorption and the S at.% of the S-hyperdoped Si samples, shown in 6 results, the 500p core-level XPS spectra of S-hyperdoped Si samples. The Si2p core-level XPS spectra of all the samples are deconvoluted, and therelated parameters are presented in detail in 252627282O (Si1+), Si2O3(Si3+) and SiO2 (Si4+), were observedas presented in Fig. S2 and Tab. SIII. The Si 2p3/2 features ofthe 100 Torr and 500 Torr samples were shifted to a lower BE(at 99.3–99.4 eV) than that of the reference Si(100) (at99.6 eV) and the shift was reversed by annealing. The observed featureshift (0.2–0.3 eV) is attributed to the structuraldisordering by presence of amorphous Si at the surface29K-edge XANES of theS-hyperdoped Si samples and pure S as a reference. According to the dipole-selectiontransition rule, the S K-edge XANES spectrum arise from the transitions of S1s core electrons to unoccupied density of states (DOSs) with 3pcharacter above the Fermi level. The line-shape of the S K-edge XANES spectrain the region 2472–2480 eV (denoted as A1) isbroadened and the feature of the S-hyperdoped Si samples reduce gradually withincident photon energy, varying quite differently from that of pure S, which wassharp and intense. The lower panel in K near-edge absorption spectra of S-hyperdoped Sisamples and reference pure S. The intensity of feature A1 of the100 Torr, 500 Torr and annealed samples (that are at500 °C or 700 °C) is lower than thatof reference pure S. The chemical states of the S species in S-hyperdoped Si samplesare responsible for the broad and declining feature, which is unlike that of pure S.K-edge XANES spectra ofS-hyperdoped Si samples and the reference undoped Si(100) sample. The spectra arenormalized to have the same area in the energy region between 1855 and1865 eV [not fully shown in the K-edge XANES spectra of theS-hyperdoped Si samples are similar to that of the reference Si(100). Thecharacteristic double-peak feature  of S-hyperdoped Si samples and reference Si(100) above thethreshold and its approximate 1.1 eV energy separation are consistentwith earlier studies323334et al.2) at~1840 eV at the Si K-edge as associated with theexcitation from Si 1s to the unoccupied Si 3p above theconduction-band-minimum (ECBM), based on crystal symmetry.Clearly, the doublet Si K-edge near-edge feature of reference Si(100) arisesfrom long-range ordering. In S-hyperdoped Si samples, a very slight blurring of thedoublet as the SF6 gas pressure increases was observed, implying thedegradation of the long-range order of sample surface and possible formation ofamorphous Si34K-edge XANES further supports the Si2p XPS and micro-Raman measurements revealing the pressure-inducedformation of amorphous Si and/or Si polymorphs on the surface of the S-hyperdoped Sisamples. Annealing the 500 Torr sample at 700 °Ccauses the relatively clear splitting of the feature again, suggesting that theS-hyperdoped Si sample that was annealed at a high temperature exhibited astructurally ordered surface that reverted closely to that of the reference Si(100).The lower panel in K near-edge absorption spectra of S-hyperdoped Si samples and referenceSi(100). Notably, the overall net intensity of various spectra (obtained byintegrating the feature area in the energy range of1837–1842 eV) is negative, and the intensity of featureA2 of the 100 Torr, 500 Torr and annealedsamples (that are at 500 °C or700 °C) is lower than that of reference Si(100), indicatingan increase (or decrease) in the number of the occupied (unoccupied) DOSs of Si3p in the conduction band of the S-hyperdoped Si samples relative to thatof Si(100). This phenomenon can be associated with the partially S-dopant stateswithin the band gap of Si, located close to ECBM; these merge withthe conduction bands of Si and act as electron donors, as proposed by severalstudies45102almost to disappear, suggesting that annealing the sample to700 °C made the DOSs of Si 3p in the hyperdoped Sivery close to that of pure Si(100). Evidently, the fact that Si K-edge XANESexhibit variations in the DOSs of Si 3p at/above ECBMdemonstrate that S hyperdoping modifies the electronic structure of Si and createstructural disordering in the samples. However, annealing the 500 Torrsample to 700 °C caused the DOSs of the Si 3p orbitalto revert to one similar to that of reference Si(100). It also indicates that a hightemperature annealing reduces structural disorder in S-hyperdoped Si and exhibited astructurally ordered surface that reverted closely to that of the reference undopedSi(100).K-edge EXAFS spectra, and corresponding k3χdata (inset) for the S-hyperdoped Si samples and the reference Si(100), furtherconfirming the structural ordering of Si atoms in the S-hyperdoped Si samples. Thefirst main feature in the FT spectra of the S-hyperdoped Si samples  is at ~2.3 Å andcorresponds to the NN Si-Si bond length (without phase correction); this position isalmost the same as that of the feature of reference undoped Si(100)25K-edgeXANES spectra that are shown in et al.K-edge EXAFSrevealed that the NN Se-Si bond distance increased with the sub-band gapabsorptance. Newman et al. also observed that annealing the samples reducesthe Se-Si bond length and the sub-band gap absorptance, owing to the formation ofthe SiSe2 precipitate. In Si K-edge EXAFS spectra that are shownin K-edge XANES and EXAFS results showed thatthe sample annealed at the high temperature of 700 °C andthe undoped Si(100) reference have similar near-edge absorption feature andstructural ordering, illustrating that the sub-band gap absorption of theS-hyperdoped Si samples is clearly related to their electronic states and atomicstructural ordering, which are also influenced by the concentration of S-dopant andthermal annealing.erence Si0, furthe3-C3. The VB-PES spectra of the S-hyperdoped Si samplesand reference Si(100) differ strikingly. Strong S-dopant states, featureA3 (at ~3.5 eV), were clearly observed in theS-hyperdoped Si samples and the 100 Torr sample had the most intensefeature A3. Notably, the SEM images of S-hyperdoped Si samples [3 with theconcentration of S. Although the 500 Torr sample has the highestconcentration of S, it does not have the most intense feature A3 in p is nearly four times that of Si 3p at an excitation photonenergy of hν = 150 eV3 of S-hyperdoped Si samples can be assigned mainly to theS-dopant states at/near EVBM or below zero energy (correspondingto 0 eV)41423 and C3, respectively,attributed to the Si 3s-3p and 3s-like bands25434445EVBM of theS-hyperdoped Si samples was closer to zero energy than that of the referenceSi(100). Typically, the EVBM of the samples is preciselydetermined by extrapolating the leading edge of the spectrum to the baseline at itslargest slope474849EVBM of theS-hyperdoped Si samples is at ~0.7 eV, which is0.7 eV shifted above in relative to that of the reference Si(100) whichhas EVBM at ~1.4 eV. The shift in theEVBM of the S-hyperdoped Si samples from that of referenceSi(100) reveals that S dopants induced formation of electron states or an impurityband at ~0.7 eV above the EVBM of pure Sias shown in 4251EVBM/ECBM of Si. Earlier studies havesuggested that chalcogen dopants, which can introduce various electron states deepin the band gap of Si, act as electron donors and may form an impurity band253255et al.EVBM of pure Si, not only forming an impurity band deep insidethe band gap of Si that gives rise to strong sub-band gap absorption, but alsocausing an IMT when the S dopant is at/above a critical concentration419 cm−3220 cm−3, the S donorswere at/above the critical density for a Mott transition; the induced deep S-dopantstates presumably behaved in a manner that was similar to metallic-like conductionowing to a delocalized electron wave-function inside the band gap of Si, and theS-dopant states, assumed to be delocalized states, formed an impurity band, whichwas responsible for the metallic-like conduction inside the band gap of thehyperdoped Si samples4251 samples  reveal tA3 at ~3. eV, wereab initio simulation package (VASP)packagek-grid to carry out thetotal energy calculation and defect-induced structural optimization. The atomicpositions have been relaxed until all of the residual forces were converged tobetter than 0.001 eV/Å−1. Tosimulate various concentrations of S doping in Si, the electronic DOSs forsupercells of size n×n×n for a two-atomprimitive cell  and an eight-atomcubic cell (n = 2 and 3) were calculated. Thissampling corresponds to systems of S1:SiN−1, for N = 16,54, 64, 128, 216 and 250 in which the defect spacing increases uniformly from onesupercell to the next. The calculated total DOSs in 20 cm−3).This result is consistent with previous measurements of the IMT in S-doped Si(1.8 × 1020 < n < 4.3 × 1020 cm−3)0W0approximationEVBM. Thecalculated total DOSs are similar to the observed VB-PES data, showing the yield ofthe S-dopant states near EVBM. According to a partial DOSsanalysis [p orbital clearly dominates the DOSsnear EVBM. However, a non-negligible contribution by thep-orbital of the S dopant is also evident in the region ofEVBM. Like that of Se-hyperdoped SiECBM (EVBM) isassociated with the S-dopant states that are created by the S hyperdoping of the Sisamples. The calculations also reveal the onset of the IMT in S-doped Si samples ata dopant concentration of lower than 0.5%. The XANES spectra, VB-PES data andtheoretical calculations demonstrate that the S hyperdoping changes the electronicstructure of Si by forming S-dopant states in the band gap of Si, which is closelyassociated with the sub-band gap absorptance.The S dopants introduced electron states, forming an impurity band within the bandgap of the hyperdoped Si, and an IMT was observed at a critical concentration of Sdopant. Related theoretical calculations were performed by means of thefirst-principles full-potential projector augmented wave (PAW) methodet al.0) form states ~0.75 eV above thevalence band edge. The shallow S level resides 0.45 eV above the valenceband. The other S states have an energy that is close to the conduction band of Si.However, our S-hyperdoped Si absorptance spectra do not show any featurecorresponding to sulfur related energy states in the band gap. In the future, wewill plan to probe sulfur related deep states in the band gap at low temperature andat far-IR wavelength in an attempt to reduce thermal broadening as well asdeep-level transient spectroscopy measurements could be useful to learn more aboutthe specific transition energy for infrared absorption3Janzén 2− species. Annealingthe 500 Torr sample at 700 °C forms largeclusters of Sn2−(n > 2) and reduces the sub-band gap absorpatnce to~7%. According to the VB-PES spectra and theoretical calculations, theS-dopant forms an impurity band at ~0.7 eV above theEVBM of pure Si(100), giving rise to the sub-band gapabsorptance that was measured herein. Despite the fact that the larger S clusters may also form deep levels above the valenceband, the high concentration of larger S clusters in the annealed samples may have beenresponsible for the drop in the sub-band absorptance2 is negative [as presented inthe lower panel of p orbitals is related tothe S-dopant states, because these merge with the conduction band and act aselectron donors in the S-hyperdoped Si samples.Based on experimental and theoretical studies above, we have proposed explanation forthe sub-band gap absorptance in the S-hyperdoped Si samples. In the present study,the observed changes in the sub-band gap absorptance of the S-hyperdoped Si sampleswere clearly related to the chemical state of the S species and the S-dopant statesin the band gap of Si. The XPS study indicated that the maximum (~87%)sub-band gap absorbing sample (500 Torr sample) contains a highconcentration of S, and especially Sn2−,n > 2), reducing the sub-band gap absorption. Ourtheoretical calculations based on the DFT method are consistent with experimentalresults and the IMT of S-doped Si is predicted to occur at an S concentration at acritical value of 0.46%(~2.3 × 1020 cm−3).In summary, the formation of S-dopant states in the band gap of Si that containsat/above critical concentration of S leads to high sub-band gap absorption inS-hyperdoped Si samples. The annealing of S-hyperdoped Si sample at700 °C returns back to the electronic and atomic structuresas that of reference Si(100), and cause S species to form larger clusters wafer hashigh resistivity (3–10 kΩ · cm) to minimize other effects of dopants.Before irradiation, the wafer was cleaned by the RCA (Radio Corporation ofAmerica) method to remove possible contamination from the surface. The laserpulses were focused to 150 μm and the surface wasraster-scanned at 8 kJ/m2 and 50 shots/area. Eachsample had a size of 1 cm2. The SF6pressure was varied to fabricate hyperdoped Si samples with a range ofconcentrations of S1320 cm−3.2Si can typically be hyperdoped with S by either ion implantation plus pulse laserannealing or fs-laser doping2K-edge XANES, Si K-edge XANES, EXAFS and VB-PES experiments wereperformed at the 16A- and 09A-beamline, at the National Synchrotron RadiationResearch Center (NSRRC) in Hsinchu, Taiwan. The XANES and EXAFS measurements atthe S and Si K-edge were performed in total electron yield modes. TheVB-PES spectra were obtained by SPEM. The SPEM measurements were made using aflexure scanning stage and a hemispherical electron-analyzer system. Ahemispherical analyzer with a 16-channel multichannel detector was used tocollect photoelectrons. The VB-PES spectra were calibrated with reference to thezero energy of clean gold metal, and the energy of the incident X-ray was fixedat 150 eV with the energy resolution set to better than0.1 eV. The zero energy is the threshold of the emission spectrum.The S and Si core-level XPS spectra of hyperdoped Si samples were also obtainedat the 09A-beamline at NSRRC. Before the synchrotron-related measurements wereconducted, hydrofluoric (HF) acid solution (1%) was utilized to eliminate thepossibility of the presence of native oxides on the sample surface, and thesamples were immediately transferred to a vacuum chamber. The core-level XPSspectra were feature-fitted using XPSPEAK41 software after a Shirley-typebackground had been subtracted from them. The IR absorption of hyperdoped Sisamples was measured using an ultraviolet-visible-near IR spectrophotometer thatwas equipped with an integrating sphere to calculate the absorptance,A = 1-R-T (R = reflectance andT = transmittance). The surface morphology of thehyperdoped Si samples was also characterized using a field-emission SEM.S How to cite this article: Limaye, M. V. et al. Understanding ofsub-band gap absorption of femtosecond-laser sulfur hyperdoped silicon usingsynchrotron-based techniques. Sci. Rep. 5, 11466; doi:10.1038/srep11466 (2015).


Underwater video services could be a key application in the better scientific knowledge of the vast oceanic resources in our planet. However, limitations in the capacity of current available technology for underwater networks (UWSNs) raise the question of the feasibility of these services. When transmitting video, the main constraints are the limited bandwidth and the high propagation delays. At the same time the service performance depends on the needs of the target group. This paper considers the problems of estimations for the Mean Opinion Score  in UWSNs based on objective methods and addresses the topic of quality assessment in potential underwater video services from a subjective point of view. The experimental design and the results of a test planned according standardized psychometric methods are presented. The subjects used in the quality assessment test were ocean scientists. Video sequences were recorded in actual exploration expeditions and were processed to simulate conditions similar to those that might be found in UWSNs. Our experimental results show how videos are considered to be useful for scientific purposes even in very low bitrate conditions. Underwater imagery is an essential tool in the research and study of the oceans since it provides invaluable information about the mostly unknown contents of the seabed and the water column. Beyond the scientific utility, other applications in the fields of defense, tourism or fishery can also be envisioned. The gathering of scientific underwater video footage is currently very expensive since it involves exploration expeditions with vessels in which divers  or robots are submerged for limited recording sessions.In this context, the deployment of wireless sensor networks capable of video capturing and transmission would be a major technological breakthrough allowing for continuous monitoring or cooperative exploration with autonomous underwater vehicles (AUVs). A video service with enough quality could lead to decisions about the re-planning of AUVs path even if instant remote controlling were not possible due to transmission delays. However, current underwater wireless networks experience limited capabilities which brings into question the feasibility of video services. The analysis of the perceived quality constitutes a very important aspect for service provisioning since it reveals which quality could be achieved under certain conditions. Moreover, if some of the attainable qualities are enough for the target applications intended by ocean scientists. Our initial hypothesis is that ocean scientists’ opinion will be influenced by the comparative advantages of the service: the possibility of a continuously available source of images and a vastly reduced delay, in spite of the limitations of the network capabilities and their impact in the achievable quality.Multimedia data acquisition is currently difficult in wireless underwater networks due to the low data rates available. Proposals in existing literature try to circumvent this obstacle with different solutions. In , pictureThe present paper is motivated by the need to have subjective QoS data for video services under the constraints of the underwater medium. The importance of subjective quality assessment is supported by similar studies already performed such as  for geneOther papers on this topic focus on general models for opinion-based quality estimation. A thorough compilation and comparison can be found in  along wiIntrusive monitoring: both transmitted and received signals are required as inputs.Non-intrusive monitoring: only the received signal is used as input.Network planning: no signal needed, estimation is based on network parameters for the transmission.According to existing standards and literature, quality for a network service can be assessed with two different kinds of approaches: subjective methods and objective methods. Both approaches usually aim to produce a standard quality metric known as Mean Opinion Score (MOS) which represents observed (for subjective methods) or estimated (for objective methods) quality in a numeric scale. The standard range is  (higher is better) although some other scales can be used for particular applications . The first group of techniques aims to get quality values directly from human evaluators. A group of viewers (in the case of video services) are presented a sequence of stimuli which they are asked to score on a quality scale. These scores are statistically processed to compute MOS values for different conditions of service provisioning. The second group of methods pursues the estimation of MOS values from a mathematical model. Objective methods are classified by ITU  in threeSubjective methods have a clear disadvantage in terms of the amount of resources needed, since time and people are required. Objective methods are faster and only necessitate an implementation of the algorithm for computing the MOS. The parametric scheme seems the most suitable option for the current scenario.The ITU G.1070 model is here taken as a reference since it is the only standardized one. Five coefficient groups are provided ; two of them have no constraints regarding bitrate range. However, full details for scene characterization, used for source subjective values, cannot be found in bibliographic references. Provided examples include no bitrates under 32 kbps, but this is the range under study due to technological limitations see . Figure An additional problem found in current parametric video quality models is the lack of an “advantage factor”. This factor characterizes the fact that users give higher scores if the service allows communication in situations with special access conditions. It is defined in the ITU standard for audio quality G.107 , which iVideo quality assessment through objective methods is difficult in UWSNs since monitoring is virtually unavailable and parametric estimation reliability needs to be checked. Therefore, a subjective study seems the most appropriate way to tackle the quality measurement task. The ITU standardized process specified in BT.500  recommenSubjective quality assessment in video services requires a careful planning accounting for all the different aspects of the experiment. The specific features of the target service in terms of video configuration parameters are detailed in Video services studied here could be provided in wireless sensor networks with anchored nodes for monitoring underwater ecosystems or with autonomous vehicles for visual exploration of seafloors. Current underwater networks are in an early stage of development and state of the art acoustic modems reach a peak data rate of 62.5 kbps with a 300 m operating range . Bitratei.e., a 10 fps video is not twice the size of the 5 fps equivalent.Nevertheless, underwater video as considered in this paper is not a service to be provided to a great number of heterogeneous users like other video services such as IPTV, videoconferencing or video-sharing streaming. Instead, it is considered as a tool for a very specific public and a particular use: scientific exploration and monitoring of areas that are otherwise very difficult and expensive to reach. We also need to consider the specific features of state-of-the-art differential video encoders which leverage intra-frame and inter-frame similarities. Because of this, a direct relation between parameters cannot be found, ○Bitrates: 8, 14, 20 kbps.○Frame rates: 1, 5, 10 fps.○Resolution: 320 × 240, 160 × 120 pixels.○Color depth: RGB (3 × 8 bits) and Grayscale (8 bits) video.Taking this into account, a sensible choice of video parameters  has been based on a previous study . In thisIn this previous work, the bitrate was found to be the main limiting factor. Below 8 kbps, video contents were difficult to distinguish, even in low resolutions. An effective data rate higher than 20 kbps is unrealistic due to protocol overheads and competition among several nodes. In these bitrate conditions, a standard 25 fps rate produced fuzzy images. For equivalent conditions, viewers preferred videos with lower smoothness with enhanced frame sharpness. This fact agrees with the behavior predicted by G.1070 model, which suggests that below a bitrate threshold, lower frame rates offer better quality. However, for two MOS vs bitrate curves plotted for different frame rates, the bitrate value for the crossing point depends on the particular frame rates being compared. Because of this, the selection of frame rates for the current experiment ranges from 1 to 10 fps.Concerning image size, only low resolutions  are suitable for these conditions since higher resolution pictures would appear hazy and suffer from artifacts. Finally, the impact of color/grayscale streams in quality will also be studied.Video sources for this experiment have been provided by the Spanish Institute of Oceanography  from real exploration expeditions in the scope of the project “Life+Indemares-Chimeneas de Cádiz” . Images Image contents range from almost static shoots of plain sea bottom to fast navigation of areas with complex layouts of irregular rocks and different kinds of underwater flora and fauna. As a representative sample of these conditions, a number of 56 scenes with a 12 s duration were chosen to be used as potential test sequences. All the video manipulations needed for the test have been made with Avidemux 2.6 software. This includes clipping, resampling, downscaling and re-encoding.H.264 differential compression produces a variable bitrate video. The average bitrate of a time window within the scene does not have to match the average bitrate for the whole scene. The bitrate for a set of frames depends on the previous frames, their bitrate and the adjusting bitrate algorithm. Every 12 s sequence is encoded at a random starting position within a longer 120 s clip. This way, we randomize the unwanted effects due to the variable bitrate coding. The 120 s segments have been processed to generate test sequences with all possible combinations of parameters mentioned in nF is the n-th frame represented as a pixel matrix containing this luminance information). The Sobel operator in Equation (1) is a convolutional kernel operator used for edge detection [space operator computes standard deviation of luminance values within a single pixel matrix. The maxtime operator selects the maximum value of the argument  over the set of all processed video frames in the clip:Two important attributes for scenes are the spatial and temporal perceptual information because high variation scenes will be further impaired when encoded. To measure the characteristics of the scenes in these two dimensions we have generated sequences with the largest evaluation resolution (320 × 240 pixels) and a very high bitrate (3000 kbps). This bitrate guarantees that there are no impairments in the clips aside from those due to the reduced resolution. The metrics for spatial perceptual information (SI) and temporal perceptual information (TI) are specified in Equations (1) and (2) . These metection , the resLearning effect: viewers can recognize objects from a low quality scene if they have seen them previously in a better quality. Thus, their opinion could be biased.Boredom effect: even in short sessions (less than fifteen minutes) volunteer viewers get bored if the same contents are displayed repeatedly. This may cause a loss of interest and introduce unwanted factors in the test.Scenes in the same group are considered equivalent in terms of content variability. Instead of choosing a few representative scenes, repeated with every configuration, each evaluation condition is applied to a different video content. Thereby we avoid two important side effects observed in the previous study :LearninInitially, contents from the 56-sample scene database were intended to be randomly assigned to each viewing condition according to content variation required see . HoweverThe absolute category rating (ACR) method described in P.910 has been used to assess video quality. It employs a standard five-level scale: bad, poor, fair, good and excellent. This method requires a short explanation time and the single stimulus presentation is the most similar one to the typical use of the video sequences.Some viewers can feel unsure how to use the scale and change their evaluation criteria after some scenes. Taking this into account, some “dummy” scenes have been introduced at the beginning of the test to stabilize viewers’ ratings. Once the viewers had ended the scene scoring, they were asked to rate the scientific utility of the quality categories they had just used in the test. They were provided a five rank (ACR-like) scale with the following values: useless, barely useful, moderately useful, quite useful and very useful. This question was designed to go beyond the perceived quality as an abstract concept, linking it to another magnitude, also subjective but with a more specific meaning. After delivering the test form viewers went through a short interview in which they were asked to give a qualitative opinion about the images they have just seen.The playback system was an HTML5 application developed specifically for this purpose. The application starts with an instruction screen with a start button. Once the button is pressed, clips are presented in sequence see  and no fIllumination conditions were measured using a photometer (Sekonik L-758DR ) for botChromaticity was not measured since required D65 illuminant corresponds with daylight and the only source of light in the room was natural light shaded by adjustable panels. Illumination conditions were kept constant during the entire test.The viewing distance was approximately 50 cm or 8 H using the picture height as reference (as defined in P.910). This matches the conditions in which the images would be used in a real service (an application on an office computer).A minimum of four viewers are required for statistical processing, although P.910 suggests at least 15 viewers should participate in the experiment. They should not be directly involved in picture quality evaluation. A total of 21 viewers took part in the test, all of them ocean scientists, geologists and biologists, from the Oceanographic Málaga Center of the IEO. The group features a wide variety of research interests such as sedimentology, submarine morphology, plankton, taxonomy of small species, benthos, and fishery. Some of them were acquainted with the use of images in their everyday work although none of them had been involved in video quality assessment before. Therefore, this sample of viewers met the requirements.○Block 1: dummy conditions for score stabilization see . The opi○Block 2: conditions for measuring the impact of the three levels of bitrate and frame rate with low variation content. Resolution and color settings for this block are QVGA and RGB.○Block 3: conditions for measuring the impact of the two levels of resolution and color with low variation content. Bitrate and frame rate settings for this block are 20 kbps and 5 fps.○Block 4: conditions for measuring the impact of the three levels of bitrate and frame rate with high variation content. Resolution and color settings for this block are QVGA and RGB.○Block 5: conditions for measuring the impact of the two levels of resolution and color with high variation content. Bitrate and frame rate settings for this block are 20 kbps, 5 fps.Each evaluation condition is a combination of test variables which characterizes a scene to be scored by viewers. The test consisted of 31 evaluation conditions arranged in five blocks as follows:In this block set up, only two parameters are changing within a block. This configuration allows for a better statistical analysis of results see  which woBlocks are presented in the same order to all viewers but scenes within a block are randomly reordered for each test. This approach reduces the negative effects of specific ordering of scenes.Full detailed list of evaluation conditions is provided in This section describes the statistical processing of the data acquired in the experiment according to the guidelines given in P.910. The main statistic is the MOS, but other meaningful indicators have been also computed. Additionally, analysis of variance (ANOVA) tests have been performed to check the significance of the MOS differences across different blocks. i.e., we can attribute the differences between MOS values to changes in parameters (if we reject the hypothesis) or to other random effects in the sampling process (if we accept it). This acceptance or rejection is based on one of the results of the ANOVA test, the p-value, which represents a probability. A high p-value means the hypothesis under test may be accepted, while a low p-value means we should reject the hypothesis. In this experiment, two factors for each block have been defined  . A two-wined see . Three lp-value) of the Mauchly’s test is below 0.05. In this case, corrected p-values  for ANOp-value (under the “Sig.” column). For blocks testing bitrate and frame rate, the Mauchly’s sphericity test results are shown first. The hypothesis of sphericity should only be rejected for the interaction effect in block 2 (p = 0.006). The corrected value for significance, calculated using the Greenhouse-Geisser method, is shown in the within subjects effects table. The results of two multivariate tests (Pillai’s and Hotelling’s Traces) are also included to complete the comparison. Other multivariate tests offered by SPSS had consistent values. The computed significances allow rejecting the hypothesis of equal means for blocks 2 and 4 (p < 0.001) and state that changes in the MOS are due to changes in parameters. We can also say that changes for different levels of bitrate depend on the frame rate and vice versa (p < 0.001).A summarized version of the full analysis output is shown in p < 0.001), but not for the interaction (p = 0.232). The hypothesis of equal means cannot be rejected for any of the effects in the low variation group either .The blocks analyzing resolution and color have only two levels per factor so sphericity checking is not applicable. In this case, the null hypothesis can be rejected for single effects in the high content variation group  to 4 (very useful). The mean utilities for each value in the MOS scale have been computed and used as a dependent variable. The estimated regression line shown in Equation (3) has been obtained as a result:The qualitative opinions gathered in the interviews cannot be analyzed through statistical methods, but are very consistent with the quantitative results. Most viewers stated that they preferred sharp images even if the video smoothness was not high. Another frequent remark was that grayscale images were as useful as the RGB videos for typical tasks. Also participants often mentioned that, in spite of their low definition, images are still useful for common processes such as identification and counting of species or identification of seafloor morphology.The MOS results provided in this section show how analyzed video services achieve moderate quality scores. Even with the strong limitations in the encoding parameters, viewers in the test scored a good number of evaluation conditions in the fair category with some of them actually reaching the good category. These results notably differ from the G.1070 estimations for similar conditions. They allow planning of underwater video services with bitrates as low as 8 kbps at the application layer with an expected perceived quality of 3 out of 5 in the MOS scale and GOB between 20%–40%. When asked about the scientific utility of the samples, most of the scores fell in the moderately useful and quite useful categories. Finally, the viewers’ qualitative comments corroborate the quantitative analysis. This agreement supports the idea that MOS is being shifted because of the special access conditions.Quality assessment is an important aspect of video service provisioning, but it turns out to be critical in highly constrained environments. It allows identifying the configuration parameters which make the difference between a useless service and a valuable one. This is the case for prospective underwater networks with a low available data rate, but also with the promising possibility of dramatically reducing costs of collecting images for scientific purposes.Due to the problems associated with objective methods, this paper addresses the quality assessment issue from a subjective point of view. We have designed and performed an experiment under the guidelines of the ITU P.910 recommendation to gather quality data. The Spanish Institute of Oceanography has provided video sources from real underwater footage and a group of ocean scientist as evaluators.The perceptual information  analysis of the video material is the first one, to the best of the authors’ knowledge, for underwater content. Most of the previous studies were focused on more general broadcasting contents.The statistical processing of the collected data shows how the potential users of the video service rate conditions under test with grades between poor and good. A good number of conditions fall around the fair quality category, which supports the utility of this kind of video transmissions. Viewers often preferred 1 fps, grayscale sequences which obtained MOS > 3 (fair) with only one exception. Although considered higher bitrates also tended to produce better opinion values, these differences can be considered a marginal enhancement depending on the frame rates being compared. This can be seen for the high variation content samples with 1 fps, where there is an improvement of only 16% when bitrate is increased by 150%. Furthermore, MOS values are considerably higher than those predicted by the G.1070 parametric model for similar video conditions. These results confirm the initial hypothesis, and would justify a revision of the model in G.1070, which could benefit from taking into account additional factors. The results also lead to a better understating of video quality perception in underwater environments and could help to harness the existing technology to provide an effective instrument for oceanic research.