Fluid-structural coupling occurs when microcantilever sensors vibrate in a fluid. Due to the complexity of the mechanical characteristics of microcantilevers and lack of high-precision microscopic mechanical testing instruments, effective methods for studying the fluid-structural coupling of microcantilevers are lacking, especially for non-rectangular microcantilevers. Here, we report fluid-structure interactions (FSI) of the cable-membrane structure via a macroscopic study. The simplified aeroelastic model was introduced into the microscopic field to establish a fluid-structure coupling vibration model for microcantilever sensors. We used the finite element method to solve the coupled FSI system. Based on the simplified aeroelastic model, simulation analysis of the effects of the air environment on the vibration of the commonly used rectangular microcantilever was also performed. The obtained results are consistent with the literature. The proposed model can also be applied to the auxiliary design of rectangular and non-rectangular sensors used in fluid environments. Most mechanical measurements using atomic force microscopy (AFM) have been conducted in fluid environments, such as the the non-destructive calibration method for spring constants of microcantilevers based on its frequency response immersed in air–5. It waet al  is equiffluid is the interaction between the fluid and the solid, kfluid is the stiffness of the equivalent spring of the fluid (the added stiffness), cfluid is the equivalent damping coefficient of the fluid (the added damping), mfluid is the equivalent mass of the equivalent dampened spring-mass system (the added mass), x is the boundary displacement, v is the velocity of the solid, and a is the acceleration of the solid.Where kfluid, cfluid, and mfluid parameters according to the procedures described below.To solve the added stiffness, damping, and mass, we establish a fluid model using the dynamic mesh model in Fluent ] can be expressed as a0t2/2. Thus, we can obtain the changing curve for the fluid force (ffluid) relative to the displacement of the solid (x). Because the initial velocity is zero  = 0), the intercept of this curve is b = mfluida0, which can be divided by a0 to derive the added mass [Eq  = 260 μm, width (W) = 51 μm, and thickness (h) = 1.69 μm. The properties of the material were as follows: young's modulus (E) = 169 GPa, Poisson's ratio (μ) = 0.3, and density (ρ) = 2330 kg/m3. Because the density of air is much lower than the density of the micro-cantilever, the added mass was negligible.Using the rectangular micro-cantilever as an example, we investigated the effects of air environments on the vibrations of a micro-cantilever as described above. The dimensions of the rectangular micro-cantilever that was used in the simulation test were as follows: length (ca. The fluid model was established using the Fluent software when the boundary velocity was 0.1 m/s ~ 1 m/s (step speed 0.1 m/s) , and the–8 Ns/m and the added stiffness was 2.8×10–9 N/m. According to the principles of vibrational mechanics, the equivalent concentrated mass of the rectangular micro-cantilever is M = 0.24 m, where m is the actual mass of the micro-cantilever and M is 1.22×10-11kg. Using the finite element analysis (FEA) method, the natural frequency of the micro-cantilever (ω0) was calculated as 35kHz, and based on Eq  is calculated as 35.2 kHz and based on Eq (d/ω0 = 98.4%. Although there are certain deviations, the trend is consistent. Compared with the vacuum environment, the frequency drift always exists in the fluid environment, which is more noticeable. Compared with the simplified one-dimensional method, these results are closer to the actual measurements. However, due to excessive assumptions and simplifications, certain discrepancies occurred between the derived and the experimentally measured results. Nevertheless, the proposed method is significant for solving the FSI problems of micro-cantilevers. In particular, Eq (According to ed on Eq , ωd/ω0ed on Eq , ωd/ω0 =ular, Eq  providesHere, we proposed a simplified one-dimensional method for analyzing the frequency response problems of micro-cantilevers in fluid environments. This method simplifies the vibration model of micro-cantilevers in a fluid environment into a damped vibration model for the spring-mass system. In addition, this method deduces a relationship equation for the natural vibration frequency of micro-cantilevers in fluid and vacuum environments. According to our results, an equivalent aeroelastic model was proposed to analyze the FSI problem of micro-cantilevers. In addition, a simulation analysis was conducted. The simulation results indicate that the frequency response model for micro-cantilevers that was developed based on the aeroelastic model can accurately reflect the vibration problem of micro-cantilevers in the air.


Twitter, a popular communications platform, is identified as contributing to improved mortality and morbidity outcomes resulting from the 2013 Hattiesburg, Mississippi EF-4 Tornado. This study describes the methodology by which Twitter was investigated as a potential disaster risk reduction and management tool at the community level and the process by which the at-risk population was identified from the broader Twitter user population. By understanding how various factors contribute to the superspreading of messages, one can better optimize Twitter as an essential communications and risk reduction tool. This study introduces Parts II, III and IV which further define the technological and scientific knowledge base necessary for developing future competency base curriculum and content for Twitter assisted disaster management education and training at the community level.  With the advent of new technologies, our ability to communicate with one another has evolved significantly. No longer are societies solely dependent on traditional media outlets, newspapers, radio, and TV for the news. With rapidly evolving smartphone technologies, societies are just an ‘app’ away from being able to deliver or receive information within milliseconds. Popular social media platforms such as Twitter, Facebook, and YouTube, have supplanted the traditional media outlets for accessing and responding to information. Every day millions of users worldwide are connected and receive their news via online social networks warranting researchers to study the mechanisms behind human interactions.––,––Recently, Twitter has been used for spreading news and updates around the world and has been shown to have application in emergency situations,,What has not been explored adequately is whether these new platforms can be recognized as vital resources to improve response to disaster and crisis events by targeting a specific geographic location that is susceptible to a disaster. The inability to reach geographically targeted populations remain some of the main reason for inadequacies in disaster response, especially where critical information needs to reach and be disseminated rapidly to the most ‘at-risk and vulnerable populations’.Disaster managers constantly work to discover ways to mitigate morbidity and mortality throughout the entire disaster cycle: prevention, preparedness, response and recovery. This capacity is largely dependent on community empowerment and community level mobilization and health promotion efforts.Twitter has become an immensely valuable tool worldwide, particularly in disseminating and conversing about issues in everyday life. Despite a limited 140 character maximum and the consequential pithy form of text used, it remains an extremely popular means of communication. It is estimated that there are over 517 million Twitter users worldwide with approximately 142 million that reside in the U.S. alone.There has been a growing list of peer-reviewed publications on the use of Twitter for emergency situations, however there is a glaring lack of understanding of the technological base and science behind Twitter usage at the operational and practical application level. This study has a two-fold goal, one to introduce Twitter as a viable communications tool at the community level during crisis events with potential for disaster risk reduction and management, and two to establish an evidence-based technological science and knowledge base necessary for community-level replication and education and training of this communications tool.BASICS OF TWITTER USE Figure 1, Table 1). On any one day over 500 million tweets, or messages, are made.Twitter, as have other commonly used programs, has acquired its jargon or specialized language using slang terms that may not be readily understood by the uninitiated reader .Figure 2, Table 1). The original Twitter “handle” may be mentioned in any subsequent tweets, so it is easily traceable back to the original message .An average Twitter user or sender has 208 followers; once a tweet is sent it becomes immediately visible to all followers  and the total geographic population of all users (the population denominator) are necessary. Only then can one begin to identify the characteristics and qualities of individuals that are retweeted by the haystack. This process will then allow disaster managers to better identify the most modifiable variables that could influence the required “superspreading” of the vital disaster messages to the at-risk populations which, in this analogy, becomes the ‘needle in the haystack.’By identifying these essential qualities and characteristics of the population, one can purposefully employ Twitter in a targeted and directed manner during any crisis. The apparent benefit of such a process is to rapidly warn and direct the population to immediately seek safety and to assist disaster managers in resourcing those areas and individuals most vulnerable and in need. A critical goal of this study is to provide a means for other investigators and disaster managers to utilize Twitter as a prevention tool for their communities. The authors offer two additional studies (Parts II and III) to describe the technological process by which one can identify both the ‘haystack and the needle populations at-risk’. In doing so, the study utilized as a working template the 2013 Hattiesburg, Mississippi tornado, a large and violent EF4 multiple vortex tornado that devastated wide portions of West Hattiesburg and surrounding communities.TWITTER DATA ANALYSIS: PREVIOUS METHODOLOGICAL APPROACHES,A recent exhaustive review of existing methodological approaches for Twitter data analysis including public health and disaster practice demonstrated inadequate methods for sampling, particularly for regional locations.The challenge with GPS is that while it is excellent at identifying targeted geolocation tweets, most people prefer anonymity and do not turn the feature on. An advanced approach often utilizes real-time filtering of the Twitter ‘firehose’ through Twitter’s publicly available interface, but this only represents 1% of current activity on Twitter.Figure 3).A novel two-step method is proposed to overcome these challenges. The first step includes data extraction of all tweets utilizing PowerTrack rules from GNIP (an authorized reseller of Twitter data) that include broad-based tornado disaster centric filters.TRIANGULATION OF REGIONAL TWITTER USERS: IDENTIFYING THE DENOMINATORFigure 3). The likelihood of a retweet of a regional news media outlet  would be a strong proxy for someone with ties to the area. The Pew Research Center study recently showed that 50% of Twitter users use the tool primarily for news.Figure 2). The categories were then evaluated to determine the contribution of each of the filters.Triangulating essentially means using three publically accessible variables, the tweet itself, the Twitter profile location metadata, and the Twitter profile biography metadata as a proxy for geolocation—to best identify that a Twitter user is from the geographically at risk region .The study received an IRB exemption for human subject research from the William Carey University IRB Committee.We developed a novel methodological framework for identifying geographically located twitter users using geographically unique regionally specific metadata parameters. This approach essentially allows us to identify twitter users in the region that do not have their GPS turned on. Table 2 summarizes the research questions and the methodology used to address these essential issues.II and III further define the specific technical aspects of the proposed methodology using the 2013 Hattiesburg Tornado template and serves as a follow-up to an earlier study that confirmed a decreased morbidity and mortality rate as compared to prior storms of similar tornado risk.Paper II describes the detailed methodological efforts used to discover the haystack of tweets transmitted during the 2013 Hattiesburg Tornado among those captured from the over 2 billion tweets in the 96 hour window of the storm that were emitted by the Twitter system.Part III describes ‘the needle in the haystack’ by identifying the Top 100 Twitter Users that were retweeted 48 hours pre- and post- tornado and analyzing the significant statistical relationship between metadata variables and in particular hashtags of the users themselves.Part IV) necessary for standards-based education and training at the community level.Parts Traditional disaster communication technologies exist for tornado response but possess inherent limitations (Table 3). While all modern technologies require a device and internet, Twitter is uniquely designed for effective and efficient two way communication. Twitter is also cost effective, used daily by the community, and allows for broad dissemination. Twitter can also be used in all phases of tornado preparedness and response and is the simplest and most redundant communications tool. Twitter can, along with traditional communication approaches, ensure that every community is a prepared community.,Currently, there are limited studies providing an easily accessible methodology to determine the effectiveness of Twitter for risk communications in a disaster.,,A recent Congressional Service Report on the use of social media in disasters identifies best practices for risk communication during disasters consist of identifying the target audience, and in disseminating accurate and appropriate types of information.,,Only by providing a usable methodology for a local population or subset of a population can one best realize Twitter’s potential. Unfortunately, local communities have taken the short stick when it comes to effective disaster planning and prevention. Studies of influenza response over the last decade show that whereas tactical and strategic plans worked well there were significant operational “gaps, weaknesses, inconsistencies and failures” at the local community level.A major limitation resides in concerns over Twitter spread of misinformation which could lead to tragic consequence before, during, and after a disaster. While this possibility exists with any form of communication, effective communicating and crowd sourcing has already demonstrated its contributions to legitimizing Twitter as a disaster response mechanism. Indiana University’s “truthy database”, created by researchers, is designed to detect misinformation and other social pollution that would corrupt vital information and its reliability as an effective disaster risk reduction communications tool.II, III, and IV of this study further detail the technological and scientific base necessary for the community development of the tool for competency based Twitter assisted disaster management education and training.Twitter is but one of many electronic communication tools available today and used by a worldwide population. This study describes the methodology by which Twitter was investigated as a possible communications tool for disasters and as an essential disaster risk reduction and management tool at the community level. By understanding how these various factors contribute to superspreading of messages, one can better optimize Twitter as a potential risk communication and disaster risk reduction tool. Parts The authors have declared that no competing interests exist.


Objective. Adropin is a newly identified regulatory protein encoded by the Enho gene and is critically involved in energy homeostasis and insulin sensitivity. This study aims to determine the correlation of serum adropin concentrations with diabetic nephropathy (DN). Methods. This study consisted of 245 patients with type 2 diabetes mellitus (T2DM) and 81 healthy subjects. Then T2DM patients were divided into normoalbuminuria, microalbuminuria, and macroalbuminuria subgroups based on urine albumin to creatinine ratio (ACR). Results. T2DM patients showed significantly lower serum adropin concentrations than those in the controls. T2DM patients with macroalbuminuria had significantly decreased serum adropin concentrations compared with the other three groups. In addition, T2DM patients with microalbuminuria showed lower serum adropin concentrations than those in patients with normoalbuminuria. Logistic regression analysis showed that serum adropin was correlated with decreased risk of developing T2DM and DN. Pearson correlation analysis indicated that serum adropin was negatively correlated with body mass index (BMI), blood urea nitrogen, creatinine, and ACR and positively correlated with glomerular filtration rate. Furthermore, multiple linear regression analysis showed that BMI and ACR were negatively correlated with serum adropin levels. Conclusion. Serum adropin concentrations are negatively associated with renal function. Adropin may be implicated in the pathogenesis of DN development.  Diabetic nephropathy (DN), which is the leading cause of end-stage kidney disease, occurs in about 20–40% of diabetic patients . TraditiAdropin is a newly identified metabolic hormone expressed in the liver and brain of mice . AdropinThis study aims to determine the association of serum adropin with the development and progression of DN.n = 110), microalbuminuria group , and macroalbuminuria group . Subjects were excluded if they had severe cardiovascular diseases, malignant tumor, acute infection, or endocrine diseases. All patients received antidiabetic drug to control glycemia and were responsive to their respective therapies. The control group consisted of 81 healthy subjects who visited the general health check-up center of our hospital. None received medication or dietary supplements. And all the control subjects had no history of diabetes.A total of 245 patients with T2DM were enrolled in this study. The patients were all diagnosed with T2DM in accordance with the American Diabetic Association criteria. T2DM patients were divided into three groups based on urine albumin to creatinine ratio (ACR): normoalbuminuria group  (coefficients of variations (CVs) for intra-assay: 5–7%; CVs for interassay: 12–15%; sensitivity: 0.3 ng/mL, detection limit range: 0.01–100 ng/mL). Metabolic syndrome (MetS) was defined using the criteria established in the third report of the National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment in Asian population (Adult Treatment Panel III) [α of 0.05 (two-tailed) and power of 90%. A minimum of 11 subjects in the three T2DM subgroup and control group allowed the detection of difference in serum adropin concentrations. Data were expressed as means ± standard deviation or median (interquartile range). The differences of characteristics between three groups of T2DM patients and control subjects were compared using Chi-square tests, one-way ANOVA, or Kruskal-Wallis test. Logistic regression analysis was used to determine the risk factors for developing T2DM and DN. The correlations between serum adropin and other parameters were analyzed by Pearson correlation analysis. Multiple linear regression analysis was used to determine the contribution of various factors to serum adropin. P values less than 0.05 were considered statistically significant.Sample size was determined through power analysis using preliminary data obtained in our laboratory with the following assumptions: The clinical parameters of T2DM patients and healthy controls are displayed in As shown in P < 0.001). As presented in P < 0.001). After adjusting for age and gender, serum adropin was associated with a decreased risk of developing T2DM . Simple logistic regression analysis showed that SBP, diastolic blood pressure (DBP), HDL-C, low-density lipoprotein cholesterol (LDL-C), BUN, the prevalence of MetS, and serum adropin showed a trend (P < 0.05) toward an association with T2DM. All of these variables were then entered into a backward stepwise multivariate logistic regression model. Multivariate logistic regression revealed that serum adropin remained a significant predictor of T2DM .T2DM patients showed decreased serum adropin concentrations compared with healthy controls (2.88 (2.43–3.41) ng/mL versus 3.71 (2.82–4.56) ng/mL, P < 0.001). As shown in P < 0.001). After adjusting for age and gender, serum adropin was still negatively correlated with the risk of developing DN . Simple logistic regression analysis showed that SBP, DBP, total cholesterol (TC), LDL-C, BUN, Cr, GFR, and serum adropin showed a trend (P < 0.05) toward an association with T2DM. All of these variables were then entered into a backward stepwise multivariate logistic regression model. Serum adropin remained a significant predictor of DN after the multivariate logistic regression .T2DM patients with microalbuminuria and macroalbuminuria were considered to have DN. Lower serum adropin concentrations were found in T2DM patients with DN compared with those without DN (2.73 (2.24–3.10) ng/mL versus 3.17 (2.63–3.68) ng/mL, r = −0.215, P = 0.001), BUN , Cr , ACR , and GFR . Then a significant correlation of serum adropin with BMI , BUN , Cr , ACR , and GFR  was observed after adjusting for age and gender. Then we performed a multiple linear regression analysis. It showed that BMI  and ACR  were still negatively correlated with the serum adropin.As presented in Adropin is a newly discovered peptide correlated with energy regulation and obesity. Adropin also plays an important role in glucose metabolism and diabetes. Treatment with adropin could reduce blood glucose levels and insulin resistance and improve insulin sensitivity in a rat model of T2DM . AdropinThis study showed that decreased serum adropin concentrations were correlated with the development and progression of DN. Previous studies determined the role of adropin in DN. Adropin expression was detected in the kidney tissue of rats, including the glomerulus, peritubular interstitial cells, and peritubular capillary endothelial cells . AdropinThe present study showed that serum adropin was correlated with renal function parameters such as BUN, Cr, and GFR. Adropin may be involved in the pathogenesis of kidney disease, not only DN. Future studies performed in patients with other kidney disease are needed to explain the precise role of adropin in kidney disease.α) and interleukin 6 (IL-6) in the pancreas tissue of diabetic rats [α level in women with polycystic ovarian syndrome [The precise role of adropin in DN mechanism remains unclear. Inflammation plays an important role in the development of DN. Adropin significantly decreased the mRNA expression levels of tumor necrosis factor-alpha (TNF-tic rats . Circulasyndrome . TherefoWe also evaluate the correlation of adropin with MetS. We found that serum adropin was correlated with BMI which is a parameter for obesity. However, no significant correlation of serum adropin with dyslipidemia, blood glucose, or blood pressure was found in the present study. Moreover, we defined MetS in the control and case groups and found that there is no correlation of serum adropin with MetS. Hence, adropin may be closely correlated with obesity. However, there is not enough evidence to conclude a correlation of adropin with MetS.This study presents several limitations. First, the sample size was not sufficiently large to achieve definitive conclusions. Further studies with large populations are thus warranted. Second, our study utilized a cross-sectional design. Hence, the causative relation must be confirmed by future longitudinal studies.In conclusion, serum adropin concentrations are negatively associated with renal function. Adropin may be implicated in the pathogenesis of DN development.


Microcirculatory alterations are frequently observed in critically ill patients undergoing major surgery and those who suffer from trauma or sepsis. Despite the need for adequate fluid administration to restore microcirculation, there is no consensus regarding optimal fluid therapy for these patients. The recent recognition of the importance of the endothelial glycocalyx layer in capillary fluid and solute exchange has largely changed our views on fluid therapy in critical illness. Given that disease status largely differs among critically ill patients, fluid therapy must not be considered generally, but rather tailored to the clinical condition of each patient. This review outlines the current understanding of context-sensitive volume expansion by fluid solutions and considers its clinical implications for critically ill patients. The modulation of capillary hydrostatic pressure through the appropriate use of vasopressors may increase the effectiveness of fluid infusion and thereby reduce detrimental effects resulting from excessive fluid administration. In critically ill patients, including high-risk patients undergoing major surgery and patients with trauma or sepsis, adequate fluid administration is essential for the maintenance of tissue perfusion. Nevertheless, there is no consensus regarding the optimal fluid therapy  for these patients . HydroxyKey features of fluid therapy in critical illness are vascular content , vascular tone , and capillary permeability determined by endothelial integrity . SurgicaCritically ill patients show a wide variety of pathophysiological conditions, severity of disease, and phase of progress. Thus, consideration of the context-sensitive volume effects of fluids may shed light on the long-standing controversy surrounding fluid therapy in critically ill patients.The endothelium is covered with a gel-like layer of endothelial glycocalyx (EG), which is a luminal coat of biopolymers forming a negatively charged meshwork –10. The The EG layer is in a dynamic equilibrium with plasma proteins, forming a flexible gel-like structure called the endothelial surface layer (ESL) . The ESLPC) lies between hydrostatic pressure in the arteriole (PA) and that in the venule (PV) [PA–PC]/RA, where RA is hydraulic resistance in arterioles) is equal to the blood flow from mid-capillaries to venules  in the steady state, PC can be described by an equation (Pappenheimer-Soto Rivera) that includes PA, PV, and the ratio of precapillary arteriolar resistance to post-capillary venular resistance [RA/RV]  under normal conditions, PC is more sensitive to PV than PA and is more similar to PV than PA  to 26 mmHg, whereas nitroglycerin decreased PC from 22 mmHg  to 17 mmHg. Given that both drugs decreased RA by 80 % compared to the baseline, the difference was explained by the contrasting effects of these drugs on RV in that sodium nitroprusside increased RV by 40 % whereas nitroglycerin decreased RV by 40 % compared to the baseline.Due to capillary hydraulic resistance, blood pressure falls along a capillary from the arterial end  to the venous end , and thus, capillary hydrostatic pressure (ule (PV) . As bloo context . For exaferently . When MAAccording to the revised Starling equation, transendothelial pressure differences and plasma-subglycocalyx colloid osmotic pressure (COP) differences are central to fluid filtration, with interstitial COP being negligible , 17.PC (approximately 25 cmH2O) and filtration rate, COP in the subglycocalyx space may be 70–90 % of that in the interstitium. However, at a low filtration rate, plasma proteins entering the interstitium via the large pore accumulate there, raising the interstitial protein concentration. Accumulated plasma protein diffuses more easily up the cleft, raising the concentration of subglycocalyx protein . In contrast, a high filtration rate dilutes subglycocalyx protein via downstream washout, leading to a decrease in subglycocalyx protein concentration  in fenestrated capillaries . Fenestrated capillaries are at least an order of magnitude more permeable to water and small hydrophilic solutes than continuous capillaries  . Subglycion Fig. .Fig. 2aPC, transcapillary flow approaches zero with a minimal COP difference [PC, the COP difference is maximal, and thus, fluid movement depends on the transendothelial pressure difference  occurs at low PC, whereas albumin convection flux  increases at high PC [PC from 15 cmH2O to 30 cmH2O doubles albumin permeability across the EG layer through a convection mechanism. Increases in macromolecule permeability across the EG layer at high PC is also observed with neutral macromolecules  [PC has on permeability across the EG layer. These findings suggest that PC plays a crucial role in volume expansion by colloid solutions via the control of fluid filtration and permeation of colloid molecules across the EG layer. high PC . Chen an high PC  developeg., HES) . The larPC is high in well-perfused dilated capillaries in the conditions such as after fluid volume loading at the induction of anesthesia and early sepsis after fluid volume loading, volume effect of colloid solution is reduced −1 Ringerovolemic , 25, spiovolemic , and epiovolemic .Fig. 4TiThe context-sensitive volume effect also applies to colloid solutions.−1 over 15 min) at the induction of general anesthesia. Plasma volumes were measured before and 30 min after the end of fluid infusion by the dilution technique using indocyanine green and hematocrit changes. Increases of blood volume after volume loading of HES 200/0.5 and 5 % albumin solutions were 43 and 38 % of the infused fluid volume, respectively. These volume effects were much smaller compared to those during isovolemic hemodilution  in that approximately 90 % of infused HES 200/0.5 and albumin solutions were retained in the intravascular space [Rehm et al.  measuredar space , 27.−1 over 15 min) increased release of atrial natriuretic peptide (by 100 %) and increased serum concentrations of hyaluronic acid and syndecan-1 (both by 80 %), both of which are constituents of the ESL [The most remarkable finding in that study  was that the ESL . Consist the ESL , 30.Fig.Clinically, perturbations of the EG layer and ESL can range from deterioration of the ESL  to destruction of the EG layer  . Septic PC augments capillary leakage of fluid and colloids from the intravascular space to the interstitium, and thus reduces the volume expansion effects of colloid solutions. This hypothesis was supported for albumin, gelatin, and HES 130/0.4  in a septic rat model [−1 over 15 min) increased MAP but decreased plasma volume expansion at 3 h after the initiation of fluid infusion compared to slow infusion of these solutions (12 ml kg−1 over 3 h) .Under conditions that cause capillary leakage, such as sepsis, the infusion rate of colloid solution influences the volume expansion effects of colloid solutions. Rapid infusion of colloid solutions can transiently increase arterial and venous pressures. The resultant increase in at model , and forat model . In the PC via arteriole vasoconstriction . Therefore, these findings suggest that the increase in PC resulting from a norepinephrine-mediated increase in MAP augments transcapillary fluid extravasation, leading to plasma volume loss.The dependence of plasma volume on MAP was demonstrated in post-cardiac surgery patients who required norepinephrine to treat vasodilatory shock . The infion Fig.  but can PC due to hypovolemia results in the retention of more fluid in the intravascular space, thereby attenuating the plasma-reducing effect of norepinephrine compared to the normovolemic state.These effects of norepinephrine on plasma volume changes depend on intravascular volume. In one study using rats with increased capillary permeability due to anaphylactic reaction, plasma volume changes following the infusion of 5 % albumin solution were measured with the albumin tracer technique . The norThe restoration of microcirculation is essential for the improvement of outcomes in critically ill patients. Nevertheless, as the assessment of microcirculation at the bedside is difficult, more readily measureable macro-hemodynamic parameters, such as arterial pressure and cardiac output, are used as surrogates, with the assumption that microcirculatory perfusion is coupled to macro-hemodynamics. However, in shock states arising from sepsis and hemorrhage, the relationship is disrupted such that microcirculatory organ perfusion may be abnormal despite restoration of seemingly adequate macro-hemodynamic parameters .In traumatic hemorrhage shock patients, despite restoration of macro-hemodynamics, sublingual microcirculation was impaired for at least 72 h . Given trescue, optimization, stabilization, and de-escalation. The “rescue” phase involves aggressive administration of fluid solution for the immediate management of life-threatening conditions associated with impaired tissue perfusion, such as septic shock and major trauma. The “optimization” phase involves adjusting the fluid type, rate, and amount based on clinical condition in order to optimize tissue perfusion, such as during major surgery. The “stabilization” phase aims for a zero or negative fluid balance by minimal maintenance infusion, such as during stays at the intensive care unit (ICU) after major surgery. The “de-escalation” phase involves minimization of fluid administration and mobilization of extra fluids to optimize fluid balance, such as during the recovery phase.Critically ill patients largely differ not only by a type of insult but also by disease phase. Hoste et al.  proposedPC is increased by vasodilation and fluid volume loading at the induction of anesthesia , the infusion of norepinephrine to increase MAP to 65 mmHg (0.04 μg kg−1 min−1) and 75 mmHg (0.12 μg kg−1 min−1) did not adversely affect microcirculatory blood flow or tissue oxygen in the intestinal tract [Vasopressors, such as norepinephrine, increase tissue perfusion pressure, but there remains a potential risk that the resulting vasoconstriction impairs microcirculatory blood flow in vulnerable organs, such as the intestinal tract and kidneys, to hypovolemia. In a pig model of abdominal surgery  with low volume replacement , which is routine practice for major abdominal surgery, does not contribute to the recovery of plasma volume but enhances interstitial edema [−1 h−1 for a 2-h surgery), whereas it was narrow for long-duration surgery (5–8 ml kg−1 h−1 for a 6-h surgery) [Ongoing hemorrhage and fluid shifts from the intravascular space to the interstitium due to surgical trauma cause hypovolemia during major abdominal surgery. However, a higher infusion rate of crystalloid solution  .PC , unstressed blood volume is already reduced by an increase in sympathetic discharge as compensation to the decreased circulating blood volume. In this context, aggressive use of vasopressor is detrimental given that it does not induce further recruiting of blood from the unstressed volume and thus impairs microcirculation by further lowering PC [Hypovolemia resulting from major abdominal surgery decreases ering PC .−1) over a short time (5–10 min) should be repeated while observing hemodynamic responses to the infusion. Many recent clinical studies have shown that goal-directed fluid therapy according to fluid responsiveness  enables the stabilization of intraoperative hemodynamics and improvement of postoperative outcomes following major abdominal surgery [However, aggressive fluid infusion transiently causes hypervolemia, leading to a decrease in the volume expanding effects of the aforementioned fluid solution . Therefo surgery –52. In f surgery , 54. How surgery . For exa surgery .−1 h−1 of Ringer’s acetate + bolus of 250 ml of 6 % HES 130/0.4) significantly increased microcirculatory blood flow in healthy and injured colon compared to goal-directed crystalloid administration  or restrictive crystalloid fluid therapy . As the cardiac index for goal-directed colloid administration was higher than those for other fluid therapies, it is difficult to separate the effects of systemic and regional hemodynamics on the improvement of microcirculatory blood flow in the colon for goal-directed colloid administration. Nevertheless, given that the splanchnic organs are at risk of hypoperfusion from hypovolemic insults, this finding confirms the scenario that improvements in microcirculatory blood flow in the gastrointestinal tract and colon contribute to the improvement of outcomes after major abdominal surgery by goal-directed fluid therapy using colloid solutions [Anastomotic leakage is a frequent complication of major abdominal surgery. Given that inadequate tissue perfusion can lead to anastomotic leakage, maintenance of tissue perfusion by adequate fluid administration may reduce the incidence of this complication. Kimberger et al.  demonstrolutions .−1 h−1 of balanced Ringer’s solution) and a group in which restrictive hydration  was combined with preemptive norepinephrine infusion to maintain MAP >60 mmHg (0.03–0.3 μg kg−1 min−1) [−1 h−1) and reduced the rates of gastrointestinal and cardiac complications compared to the control (26 vs. 85 %).Norepinephrine infusion can reduce the total volume of fluid solution administered during major surgery. A randomized clinical study of radical cystectomy compared total fluid volume and the incidence of postoperative complications between a control group (6 ml kg1 min−1) . NorepinIntravenous fluid administration is a first treatment for traumatic hemorrhage shock. However, as long as hemorrhage is not controlled, the full restoration of blood pressure by aggressive crystalloid volume loading may increase the risk of bleeding . This isAccording to the volume kinetic analysis, in normotensive adult male volunteers who had 900 ml of blood removed within 10–15 min, crystalloid infusion of 2700 ml over 30 min resulted in hypervolemia by 600 ml . The cryUncontrolled hemorrhage shock model in mice compared fluid requirements, blood loss, and intestinal microcirculation between fluid  resuscitation with or without norepinephrine to target MAP at 50 and 60 mmHg [PC despite vasodilation , resultant fluid overload causes increased use of fluid-related medical interventions such as diuresis and increased hospital mortality [The benefit  of early goal-directed therapy for septic shock that was originally proposed by Rivers et al.  has not ortality .PC is normalized by fluid administration, further fluid infusion may cause hypervolemia. The resultant increase in PC enhances fluid leakage from the intravascular space to the interstitium due to degradation of the EG layer and ESL [Once  and ESL . Therefo and ESL . The admPA, but low MAP does not necessarily imply low PC because PC is determined also by PV and RA/RV. Given that PC plays a key role for the volume expanding effect of fluid administration, strategy of fluid therapy differs by PC .Most frequent trigger for fluid volume loading in critical illness is hypotension. Indeed, low MAP may decrease PC Table . HoweverThe increase of MAP following fluid challenge may be a surrogate for detecting fluid responsiveness in clinical practice, but only 44 % of fluid responders  in one study for septic shock patients showed an increase in MAP of more than 10 % from pre-infusion levels . Fluid-iPC [PC increases volume expanding effect of fluid solutions.ICU patients with a low sublingual microvascular flow index  exhibited an increase in MFI after fluid challenge , whereas those with a high sublingual MFI (≥2.6) showed no significant change . HoweverPC , the finPC with vasoconstriction, they are expected to show fluid responsiveness  with large decrease of SVV after fluid challenge. In this context, fluid volume loading is effective to restore PC via a large volume expansion effect and thus increases venous return and cardiac output.Fluid challenge that monitors flow-related dynamic parameters following fluid bolus infusion is a useful tool for decision-making in fluid therapy . For exaNevertheless, frequent fluid challenges result in excessive fluid administration causing tissue edema . A recenCommon to critically ill patients who undergo major surgery or suffer from trauma or sepsis are microcirculatory disturbances from capillary leakage due to inflammation. Although fluid administration is useful for restoring microcirculation by correcting hypovolemia, the volume expanding effects of the fluid solution is context-sensitive. A key element of these volume expanding effects may be capillary hydrostatic pressure, which depends on arterial pressure and vascular tone. The modulation of capillary hydrostatic pressure through the appropriate use of vasopressors might improve microcirculation and thus patient outcomes by increasing the volume effectiveness of fluid infusion and reducing the adverse effects of excessive fluid infusion. There remains a large gap between fluid pathophysiology based on the revised Starling equation and fluid therapy in critical illness because of difficulties in measuring capillary hydrostatic pressure in clinical settings. Nevertheless, clinicians should be aware of possible involvement of capillary hydrostatic pressure in a complexity of fluid therapy in critical illness.


Routine fluid prescription is common practice amongst anesthesiologists caring for patients undergoing colonoscopy. However there is limited information about routine procedural fluid prescription practices of anesthesiologists in this setting. Routine fluid administration may also have important pharmaco-economic implications for the health care budget. Therefore we performed a prospective observational study assessing the fluid prescription practices of anesthesiologists caring for patients undergoing elective colonoscopy.With Institutional Review Board approval, adult patients receiving procedural fluid intervention during elective colonoscopy were included. Data collected: size of intravenous cannula inserted, volumes of fluid administered, adverse events, procedure duration, and pharmaco-economic costs associated with fluid prescription. Anesthesiologists and gastroenterologists were blinded to the study.We collected data on 289 patients who received fluid prescription by their attending anesthesiologist. Median patient age: 48 yrs (range 18–83), gender: 174 (60%) female; median duration of procedure: 24 minutes (range 12–48). Cannula size: 181 (63%) patients received a 22G cannula or smaller. Median volume of fluid administered during the colonoscopy was 325 ml (range 0 to 1000 ml). Median duration of the procedure: 25 minutes (range 12 to 48 minutes). Median volume of fluid administered in the post anaesthesia recovery unit: 450 ml (range 0 to 1000 ml). Fifteen patients (5%) became hypotensive during the procedure and two patients (<1%) developed hypotension in the PACU. There was no difference in the median fluid requirements between patients with hypotension and those without. Fluid volumes were strongly associated with increasing cannula diameter (p = 0.0001), however there was no association between fluid volumes administered and vasopressor use, peri-procedural adverse events, or procedure duration. At our institution fluid therapy currently cost about AUD$4.90 per patient: 1 L crystalloid $1.18 and fluid delivery set $3.77 Our institution performs over 9000 endoscopic procedures annually with fluid therapy costing about $45,000/year.Routine fluid prescription by anesthesiologists managing patients undergoing colonoscopy was ineffective with low actual fluid volumes delivered during the procedure. There was no association between volumes of fluid delivered and procedural hypotension, adverse events, or procedure duration. Anesthesiologists should question the clinical and pharmaco-economic value of routine fluid administration for patients undergoing elective endoscopy. Colon cancer screening programs worldwide are adding to greatly increased demand for colonoscopy, making it one of the most common procedures performed-3. IntraWith approval from the Human Research Ethics Committee at Austin Health (H2013/05078), we conducted a prospective, blinded observational study of patients undergoing elective colonoscopy at the Austin Hospital. Austin Hospital is a university hospital in Australia with tertiary level services in cardiothoracics, major hepatobiliary surgery including liver transplantation and spinal injury. In addition to all major surgical specialties, the hospital provides services for over 9,000 endoscopic procedures annually. All adult patients undergoing elective colonoscopy who received peri-procedural IV fluids as part of standard anesthesiology care were included. Patients undergoing combined gastroscopy and colonoscopy, emergency colonoscopies, and colonoscopies performed without IV fluid being prescribed were excluded. In accordance with the requirements of the NHMRC National Statement on Ethical Conduct in Human Research 2007, Austin Health's Research Ethics Committee waived the requirement for patient consent.We collected data on timing fluid administration , the size of the peripheral cannula through which fluid was delivered, and volumes of fluid administered both during the procedure and in the post anesthesia recovery unit (PACU). Other data collected included procedure duration, incidence of hypotension, nausea, vomiting, and the use of vasopressors to treat or prevent hypotension. Hypotension was defined as any documented systolic blood pressure less than 20% of the pre-procedural value. Nausea was defined as any patient reporting a feeling of sickness in the stomach with an urge to vomit, or the use of any antiemetic drug during the colonoscopy procedure admission. If a patient received an antiemetic drug they were considered to have experienced nausea during the admission. Vomiting was defined as the ejection of any contents of the stomach through the mouth at any point once the procedure was completed. Finally pharmaco-economic costs associated with peri-procedural fluid intervention were calculated, taking into consideration the number of IV giving sets prepared by the nursing staff per list and the total amount of time taken to prepare these fluids. All procedural anesthesiologists and gastroenterologists, as well as the recovery nurses were blinded to the study.As per our institution’s protocol for elective colonoscopy, all patients received a standardized bowel preparation regime that included a modified diet 3 days before the procedure, then 3 sachets of PicoPrep  the day before the procedure with 250–500 ml water, then free clear fluids up until four hours before the procedure. Small sips of water on the morning of surgery were allowed for all medications, except for oral hypoglycemics, which were stopped the night before. All patients were admitted to hospital on the day of the procedure. Trained anesthesia nurses were responsible for the preparation of the IV fluid and giving sets. As per our institution’s protocol for elective colonoscopy, all patients require a 30 minute recovery period in PACU before being discharged back to the departure lounge for a light snack and drink before being discharged home.All patients had an IV cannula  inserted by the attending anesthesiologist. The size of the IV cannula was at the discretion of each attending anesthesiologist. As per hospital protocol, the type of fluid used was a 1000 ml balanced crystalloid solution flask, , but the amount of fluid delivered was again entirely at the discretion of the attending anesthesiologist. Patients were placed in a left lateral position with their knees flexed. Consultant anesthesiologists performed the procedural sedation and consultant gastroenterologist performed all the endoscopy procedures. As per hospital protocol, routine monitoring consisted of 3 lead electrocardiography, oxygen saturation, and non-invasive blood pressure measurements taken from the left upper arm every 3 minutes. Oxygen was delivered via facemask at 6 L/min with the option of attaching capnography to these masks if clinically indicated. All patients underwent a standardised conscious sedation technique using propofol IV   and fentanyl IV  (0.5 to 1 ug/kg boluses) titrated to effect. As per hospital guidelines, the management of peri-procedural hypotension consisted of boluses of metaraminol IV 0.5 mg  or ephedrine 5 to 10 mg IV . The use of all other emergency drugs including atropine or adrenalin was permitted if clinically indicated. After the procedure patients were transferred to the PACU for a 15-minute observation period, and if clinically stable were discharged back to the day admission unit for a light diet and free fluids before being discharged home. The treatment of hypotension in recovery was at the discretion of the attending anesthesiologist and consisted of further fluid boluses, or with the same pharmacological intervention described above. All data collected were transcribed onto a data collection form and then entered into a de-identified electronic database.A statistical software package  was used for statistical analysis. Results were expressed as either a median (range), or in the form of frequencies and proportions unless otherwise stated. Multivariate analysis was undertaken using a backward stepwise logistic regression model to identify factors independently associated with fluid intervention including all factors where the p-value was less than 0.1 on univariate analysis. The 95% confidence intervals (CI) were reported where appropriate. A p-value < 0.05 was considered significant. We reported this study using the STROBE guidelines for reporting observational studies.We collected detailed fluid prescription practices of anesthesiologists for 289 patients undergoing elective day case colonoscopy procedure over a 3-month period. Median patient age was 48 years (range 18–83 years); 174 (60%) were female. One-hundred and eighty one patients (63%) received a cannula size 22 gauge  or smaller; and 108 patients (37%) received a 20 gauge cannula  or larger  became hypotensive during the procedure and two patients <1%) developed hypotension in the PACU. There was no difference in the median fluid requirements between patients with hypotension and those without hypotension . Three patients (1%) experienced nausea in the PACU. All patients responded to simple pharmacological intervention. Patient groupings for statistical comparison were created about the median volume of fluid administered. The associations of patient demographics, intra-procedural data and fluid administration were evaluated using both univariate and multivariate analyses , routine use of intravenous fluid prescription for elective colonoscopy has considerable pharmaco-economic implications.The findings of our study are comparable to the finding of Leslie et al.. In theiAs expected, the volumes of fluid delivered to patients in our study correlated strongly with the IV cannula size, where patients with a larger cannula received a larger volume of fluid. However the volumes of fluid delivered in this study fall well short of the maximum possible volumes delivered through the cannulas Table . The aveAt our institution, the cost of IV fluid therapy, in Australian Dollars  is approximately $4.90 per patient: 1 L crystalloid $1.18 and fluid delivery set $3.77. Our institution performs over 9,000 endoscopic procedures annually and if every patient received IV fluid therapy it would cost the hospital approximately $45,000/year. In addition, on average 4 fluids sets are prepared by nursing staff with an average time taken per list to be 4.8minutes. We have approximately 20 endoscopy lists per week resulting in roughly 95minutes of nursing time spent on preparing fluids every week. For 1year this would roughly equate to 82 nurse hours. As IV fluids are typically prepared at the start of each list, the additional 5minutes saved from not preparing fluids may translate into earlier start times and increased patient turnover.There are several limitations to our study. Although this is one of the largest prospective studies to report of detailed standard of care fluid intervention practices of anesthesiologists, only 289 patients were reviewed. However, this is the first study to report on routine peri-operative fluid prescription practices in a tertiary care hospital, reflecting actual anesthesia practices in this setting. It was possible that not all complications were properly recorded, or there were inaccuracies in the recording of fluid prescription data. However, all patient records were checked by two independent study investigators, and we consider the influence of inaccuracy to be insignificant. In addition, two investigators reviewed all anesthesia and PACU charts to ensure a thorough and accurate tally of fluid prescription and complications were documented. This is a single-centre study, which limits the external validity of our findings. However, our hospital shares similar characteristics with other tertiary hospitals in Australia. We did not calculate the cost of treating hypotension with the use of the pharmacological agents described above. Routine use of ephedrine or metaraminol for the treatment of hypotension also has pharmaco-economic considerations. At present, a single 10 mg/ml metaraminol ampoule  costs our institution Au$28.39, and the cost of a single 30 mg/ml ephedrine ampoule  is Au$15.38. Similarly we have not recorded the pharmaco-economic implications of post-operative nausea and vomiting, or evaluated the effects of these adverse events on discharge times. This may also have direct pharmaco-economic implications, however the primary objective of this study was to document real-life and accurate fluid intervention practices, and determine if these would influence haemodynamic parameters such as hypotension. Finally, we have not made any economic assessment of stay in the PACU or day procedure unit. However, these circumstances in no way affect the validity of the results or the objectives of this study.There are various strengths in this study. The quality of treatment that the patients receive is in keeping with the current best standard of care with specialist anesthesiologists, gastroenterologists and nursing staff who are adequately trained in caring for patients undergoing routine colonoscopy in this setting. Patient management in our endoscopy suite and PACU follows the Australia and New Zealand College of Anesthetists guidelines for management and monitoring of sedated patients and post anesthetic care,16, whicIn conclusion, we observed that despite routine IV fluids being prescribed for patients undergoing elective colonoscopy, on average only 325 ml was actually delivered during each procedure. As expected, fluid volumes were strongly associated with increasing cannula diameter, however there was no association between fluid volumes administered and vasopressor use, peri-procedural adverse events, or procedure duration. At our institution fluid therapy currently costs about au$4.90 per patient. We think anesthesiologists should question the clinical and pharmaco-economic value of routinely administering intravenous fluids to adult patients undergoing elective endoscopy.No external funding and no competing interests declared.LW: Principle Investigator who designed the study as part of an “Austin by Design” initiative. He was responsible for the ethics submission, analysis of data, and writing of the manuscript. COT: responsible for acquisition of data, literature review and writing of manuscript. MF, DL & ST: participated in data collection, entry of data from the medical records, checking of electronic medical records, and collation of final database. PP & DS: analyses of data and writing of manuscript. All authors read and approved the final manuscript.


Dear Editor,Five-aminolevulinic acid 5-ALA)-derived fluorescence is approved for fluorescence-guided resections of malignant gliomas, relying on selective synthesis and accumulation of protoporphyrin IX (PPIX) within malignant glioma cells -ALA-deri using flToday, fluorescein sodium is again under scrutiny , 4 usingLittle is known about the best timing of i.v. fluorescein application before resection. Injecting fluorescein too early might result in unspecific propagation with oedema, whereas acute injections might be useful for detecting abnormally perfused tumour tissue. Levels in the blood will be high, especially with acute injections, leading to fluorescence of all perfused brain tissue. To our knowledge, such time-resolved information on the specificity of fluorescein are not available. Therefore, we conducted a small pilot study using two timing regimes in four patients pre-treated with 5-ALA , comparing early  with acAn example of fluorescein application prior to opening of the dura is given in the Fig. In a second patient, a patient with recurrent low-grade glioma, in whom fluorescein was given before opening of the dura, fluorescence was found in the brain adjacent to the tumour and in the dura itself. However, fluorescence appeared patchy or missing in the macroscopically detectable tumour. The tumour was not positive for 5-ALA fluorescence. At the end of the resection, after tumour removal had been confirmed by intra-operative ultrasound, diffuse green fluorescence was observed along all resection margins. Biopsies taken from this area were devoid of tumour.In a third case, a patient with temporal glioblastoma, we attempted acute injection  to deterOverall, we observed no clear value of fluorescein in our small study, which we closed prematurely. Clearly, further work elucidating optimal timing and dosing of fluorescein is warranted.Supplementary videoAcute injection of fluorescein sodium with the aim of detecting abnormally perfused tumour tissue (as detected by co-administered ALA-induced PPIX fluorescence), relying on possible differential accumulation in the contrast-enhancing tumour positions. Fluorescein was extravasated markedly in the necrotic part of the tumour but only minimally in the tumour surrounding necrosis (verified by biopsy), which was clearly PPIX positive. (M4V 28035 kb)Below is the link to the electronic supplementary material.


With the scale expands, traditional deployment algorithms are becoming increasingly complicated than before, which are no longer fit for sensor networks. In order to reduce the complexity, we propose a node deployment algorithm based on viscous fluid model. In wireless sensor networks, sensor nodes are abstracted as fluid particles. Similar to the diffusion and self-propagation behavior of fluid particles, sensor nodes realize deployment in unknown region following the motion rules of fluid. Simulation results show that our algorithm archives good coverage rate and homogeneity in large-scale sensor networks. As one of the basic problems in wireless sensor networks, deployment algorithm has attracted scholars' wide attention, while a series of algorithms have been put forward in allusion to different deployment demand. In this paper, with regard to the problem of large-scale wireless sensor network deployment, a scheme based on viscous fluid model is proposed.A large number of researches have been done to solve various issues related to the deployment problem. There are practically three categories of methods: methods based on geometrical model, methods based on virtual potential field, and methods based on biological intelligence. Since fluid field is one kind of virtual potential field, the algorithm proposed in this paper belongs to methods based on virtual potential field.The most classical method based on virtual potential field is proposed by Howard et al. . They prAs we know, electrostatic field also is a kind of virtual potential field. In , ToumpisRecently, mobile sensor network node deployment based with virtual potential field is drawing researchers' more and more attentions. In , the autIn this paper, we present an adaptive deployment strategy that guarantees good coverage and uniformity, with only part of the deployment environment being given. Provided the approximate size of the deployment region, the algorithm can compute the number of nodes needed by setting appropriate parameters, thereby completing the deployment. The subsequent contents of this paper are arranged as follows: related works are introduced in There have been plenty of representative literatures –12 relatThe aforementioned literatures have made contributions to the deployment of mobile sensor network. Yet, they still need to be further strengthened, especially in allusion to large-scale sensor network. The deployment approach proposed in this paper is simple and pragmatic, leading to good adaptability in water, on the ground, and in the air. Literature , 12 provDeployment algorithms mentioned in the above literatures are all based on virtual potential field. They share something in common that the deployment of mobile sensor nodes are considered as a coverage process. Nodes are affected by virtual force and eventually reach equilibrium from the initial position (randomly or prematurely set), thereby finishing the deployment of the entire network. Although these algorithms assume the deployment environment is unknown, claim themselves adaptive, and can complete the task before knowing the environment, they all implicitly presume that the size of deployment region is known, so is the number of nodes that need to be deployed. However, if the size of the deployment environment is not known a priori, these algorithms can only provide coverage to the size extent of the area that is previously fixed by the number of nodes to be deployed. Thus, a certain quality of service could not be guaranteed with these approaches. Therefore, the adaptivity and scalability of the deployment algorithms are dramatically limited.Hydrodynamics is a branch discipline of mechanics, which takes fluid as the study object, so as to research the motion of fluid, as well as the relationship and rule between acting forces. The principle of hydrodynamics may be applied in sensor networks, building a wireless sensor network based on flow field theory.For continuous fluid, there are mainly four types of fluid models , where fdV, fluid micelle moves along filament line, while its velocity V is equal to the flow velocity along the filament line. Randomly selecting a spatial point M from the flow field, with the side length separately denoted by dx, dy, and dz, is shown in M at the moment is v, while vectors of velocity v along the three coordinate directions are separately vx, vy, and vz, and fluid density is ρ. In accordance with momentum conservation law, the accelerated velocity shall be a = dv/dt. Along the three coordinate directions, the accelerated velocities are separated and described as ax = dvx/dt, ay = dvy/dt, and az = dvz/dt.Randomly selecting an infinitesimal fluid micelle, and assuming that its volume microelement is ρ, f, dx, dy, and dz, as well as surface forces acting on the six surfaces. There is viscous effect between micelle and fluid around, so that the surface force is normally no longer perpendicular to their respective acting surface. Px, Py, and Pz are employed to separately describe surface forces on the three surfaces of MBDC, MCEA, and MAFB, so that Px = pxdydz, Py = pydydx, and Pz = pxdxdy. Decompose these surface forces as normal stress and shear stress, so thatExternal forces acting on the fluid micelle include mass force pxx, pyz,… separately stands for stress components, while the first subscript refers to the normal direction of acting surface and the second subscript refers to the acting direction of stress. As for this, pxx, pyy, and pzz separately represent normal stress components, while the rest pxy, pxz,… are shear stress components.In the equation, Px′ = px′dydz, Py′ = py′dzdx, and Pz′ = pz′dxdy, on the three surfaces of GEAF, GFBD, and GDCE. These surface forces may be decomposed into their respective normal and shear components. Compared with the aforementioned three surfaces, the three acting surfaces are slightly changed in aspect of coordinate, that is, dx, dy, and dz. Being expanded according to Taylor of function, and abandoning high-order small quantity, normal stress and shear stress on acting surface may be described asSurface forces acting on the micelle also include x shall beAccording to Newton's second law, motion equation of micelle along the three coordinate directions may be figured out, while the motion equation along axis The above equation may be simplified asPut the stress component in the above equation with generalized Newton's laws of internal friction, and simplify the expression:By expanding the second term on the right side of the equal sign, the following expression is figured out upon simplification:Expression  is viscoThe property of fluid resisting the relative motion between micelles is referred to as viscidity. Assuming that there is viscidity between nodes, such viscidity is utilized to control motion between nodes, so as to maintain the connectivity of network.du/dt stands for velocity derivative, that is, accelerated velocity; f refers to vector of unit acting force, ρ is fluid density, and p represents fluid pressure, while U stands for the velocity of an infinitesimal fluid element. In the end, v is motion viscosity of fluid, and v = μ/ρ.Navier-Stokes equation based on viscous flow is shown inu and v separately refer to velocity components of an infinitesimal fluid element along the respective direction, while fx and fy are component forces per unit along x and y direction. ConsiderIn this paper, we are only to study the motion of two-dimensional fluid. As for this, only two-dimensional vector form of Navier-Stokes equation is adopted. In rectangular coordinate system, related components may be described asPutting  in 8), , 8), difi and superscript t are applied to identify the values of parameters u, v, ρ, p, f, and ν of fluid element i at the moment of t.In , subscriRs to sense the position of obstruction, and so forth. Each sensor node has a communication radius with distance of R.When fluid model is applied to analyze the deployment process of wireless sensor network, nodes shall be assumed with some basic properties: nodes are able to move freely; each network node is able to acquire its position, velocity, and pressure; each sensor node has a sensing range with radius of In addition, it is also assumed that there is viscosity between nodes, while the viscosity is related to the distance between neighbor nodes. Larger distance leads to higher viscosity, and smaller distance leads to lower viscosity. Thus, in deployment process, overdispersion of nodes may be avoided, so as to ensure the connectivity of network.Counter definitions of the above fluid variables in mobile sensor network may be described as follows.1) Velocity Vector. Velocity vector of nodes is similar to velocity vector of viscous fluid element. The velocity of node i at the moment of t may be descried as Vit = .(2) Density. Local density of the position, where each node is located, may be described by ρi. The definition is shown by Intensity of Pressure. Intensity of pressure is the main driving entity in flowing of fluid. For ideal gas, the status equation is shown byρ refers to local density, R is specified constant, and T represents absolute temperature.(4) Spatial Derivative of Parameter. In , In , θij re5) Accelerated Velocity. In sensor networks, nodes are moving all the time. Yet, as in fluid models, the movement is not in constant velocity, which may also present accelerated velocity that is similar to fluid elements, that is, du/dt, dv/dt.(6) Viscosity. Assuming that viscosity is variable, such viscosity is related to the average distance between a certain node and its neighbor nodes. Larger average distance leads to higher viscosity, while smaller distance leads to lower viscosity. As for this, viscosity may be defined as follows: [In the formula, cs (SPH) . By convμ refers to the viscosity, ε is shear stress rate in fluid, f stands for acting force, ρ is the density, p represents pressure intensity, the Greek letter superscripts α and β are designed to identify coordinate direction, and W refers to smoothness index, as is shown in the following equation:R = r/h = |x − x′|/h, r is the distance between two points or particles on x and x′, and h refers to the smooth distance, that is, communication radius. Moreover, ε approximate expression of particle i shall beIn , μ referdu/dt, dv/dt may be worked out. In the computation, du/dt, dv/dt, Vit, ρi, p, ∂ξit/∂x, ∂ξit/∂y may be put into  Initial Value. Time iteration method in ((ethod in  needs to2) Physical Boundary Condition. The velocity of nodes sticking closely to object surface is tangent to object surface; that is, flow on object surface is tangent to object surface. As is shown by d, the moving velocity of node is changed.(3) Constraint and Control Condition. Denoting the threshold value of velocity as Vth, the velocity of sensor node shall be controlled below the threshold., the coverage rate increases from below 1 to 1. In the meanwhile, uniformity is also sharply improved. All these consequences resulted from the disappearance of massif.After the redeployment (20 < time < 40), nodes reach the balance state again. The value of coverage increases to approximately 1, while the value of uniformity is stabilized around 0.2, which is slightly lower than the previous stable value −0.4. Thus, the disappearance of massif improves the uniformity.Based on the above researches on deployment algorithm, this algorithm is properly simplified based on predecessors' research findings, eliminating the complexity of previous similar algorithms while preserving the property of self-adaption.Deployment of large-scale sensor network is always a research hot spot in the field. How to save time and energy, to uniformly deploy nodes, so as to maximize service life of network? This is a goal pursued by all deployment algorithms. However, in practical application, problems and difficulties encountered are complicated and diversified. As for this, an extensible, self-adaptive, robust, and simple deployment algorithm is necessary.In this paper, viscous fluid model is applied in deployment of wireless sensor network, with an extensible sensor network deployment algorithm proposed. This algorithm abstracts sensor nodes as fluid particles, while the parties abide by the motion rules of fluid. Nodes simulate the diffusion and self-propagating behavior of particles in fluid, realizing effective and ideal coverage range, so as to complete network deployment in unknown area. Shown by the simulation test, the algorithm shows good performance in various situations. For completely unknown deployment area, the algorithm proposed in this paper may fully bring to play its superiority of self-adaption, so as to reach the expected deployment effect. Thus, it is a robust and self-adaptive deployment algorithm.


The conference was a Twitter-only conference, allowing researchers to upload academic posters as tweets, replacing a physical meeting. This paper reports the details of the event and discusses the outcomes, such as the potential for the use of social media to enhance scientific communication at conferences. In particular, the present work argues that social media outlets such as Twitter broaden audiences, speed up communication, and force clearer and more concise descriptions of a researcher’s work. The benefits of poster presentations are also discussed in terms of potential knowledge exchange and networking. This paper serves as a proof-of-concept approach for improving both the public opinion of the poster, and the enhancement of the poster through an innovative online format that some may feel more comfortable with, compared to face-to-face communication.The Royal Society of Chemistry held, to our knowledge, the world’s first Twitter conference at 9am on February 5 An academic conference should be a symposium where academics can report, share, discuss their work, and exchange ideas through a variety of different communication methods. A typical academic conference may consist of several oral presentations, including those from keynote or plenary speakers, in addition to a number of workshops, which offer a more interactive method of delivery. There is also the research poster, a somewhat maligned and misunderstood entity that in some instances feels like an afterthought. However, it could be argued that if knowledge exchange is the fundamental purpose of a conference, which it is, then posters and workshops are far more valuable than oral presentations ; in whicThe “all eyes on one” style of oral presentations is extremely limiting in terms of opportunities for the speaker to interact personally with members of the audience. Even in the post-talk questions, time constraints mean that not all questions can be asked, whilst some participants may be unable to comfortably relay their points to the author in that particular environment. Aside from this, the less intimidating nature of poster sessions may be preferable to a larger percentage of researchers, which might explain why the poster presentation saw large increases in the 1990s , who use a concept called PICO (Presenting Interactive COntent) to diversify the knowledge exchange process. The general idea of PICO is for researchers to orally advertise their work in a two-minute flash presentation, in order to encourage the audience to later join them at interactive touchscreen slides, where they can engage with the author personally, in a format similar to the traditional poster session . Such a American Geophysical Union (AGU), have piloted a virtual poster showcase, encouraging researchers to participate at conferences virtually through a digital link. This obviates the requirement for travel, and therefore extra funding for travel purposes. Furthermore, posters are becoming an ever more acceptable route into publication,via academic journals such as inF1000Research, which publishes posters and slides alongside more traditional articles, as a means of reference-worthy academic literature.With any conference, there are always academics wishing to participate, but who are unable to because of travel and funding restrictions. For some researchers, these restrictions can be detrimental for the dissemination of their research, and can ultimately have a negative effect on their career progression. To combat this, some organisations, like theAnother potential alternative is the use of social media to encourage poster engagement, and this route will form the focus of this paper. The ubiquity of social media is responsible for many of the social behaviours and patterns that have emerged as a result of online communication, and given the power of social media, it could potentially be harnessed to help ensure posters are more greatly discussed, thereby helping to improve ideas and knowledge exchange between academics. This paper presents findings from the world’s first Twitter poster conference, organised by the Royal Society of Chemistry, and discusses the potential impact of social media upon the academic poster.Analyst,Analytical Methods andJournal of Analytical Atomic Spectroscopy (JAAS). The ASTPC took place from 9am on 5th February 2015 to 9am on the 6th February 2015, giving researchers a period of 24 hours to tweet pictures of their poster using the hashtag #RSCAnalyticalPoster. The aim of the ASTPC was to create an opportunity for participants to showcase their research, meet new people, share ideas and learn about some of the latest developments in different areas of analytical science. The conference was open to anyone working in any area of analytical science whose research topic was within the scope ofAnalyst, Analytical Methods, orJAAS.The Analytical Science Twitter Poster Conference (ASTPC) was organised by the Royal Society of Chemistry (RSC) journalshttp://blogs.rsc.org/an/2014/12/19/rscanalyticalposter/). We have no way of knowing whether the competitive element skewed the participation of this conference, but feel that at most scientific conferences there are prizes awarded for the best posters, so in this regard assume that the competitive element does not increase nor decrease participation.Participants were encouraged to tweet their work, and to be available to answer any questions that interested academics  might have about their research. There were also prizes for the best Twitter poster, as judged by the scientific committee, with remuneration in the form of an iPod and RSC book vouchers. Furthermore, unlike a regular conference that charges fees to participate, this event was entirely free, and had no registration process other than an email to the journal to verify identity. A scientific committee consisting of 12 academics associated with the RSC were heavily involved in asking questions, generating discussions, and judging posters. Further information regarding the event can be found on the journal’s official blog  ethical guidelines for educational research, with all of the data in this study fully anonymised. All work was also carried out according to the terms of use as indicated by Twitter's policies.http://www.followthehashtag.com. The data sample was taken over a period of 63 days, from 9am on 19th December 2014 to 9am on 20th February 2015. The data was collected from such an early date because this is when the initial announcement of the hashtag was made and promotion of the event began, however the vast majority of tweets were sent during the 24-hour window of the competition itself. Data collection stopped shortly after the prize winners were announced. Only tweets with the hashtag #RSCAnalyticalPoster were considered for the analysis, and so any figures reported here are most likely an underestimate, precluding any tweets for which the hashtag was absent. All reported times are in Greenwich Meantime.The participants that took part in the ASTPC are now assessed in terms of the number of tweets, area of the world from which the tweet was sent, total number of followers, and potential viewing audience for the tweets. All data is sourced from an online data collection program, available atRaw data for 'Twittering About Research: A Case Study of the World's First Twitter Poster Competition'Data have been de-identified.Click here for additional data file.Copyright: © 2016 Randviir EP et al.2016Data associated with the article are available under the terms of the Creative Commons Zero "No rights reserved" data waiver (CC0 1.0 Public domain dedication).Given the nature of a Twitter discussion, it is perhaps more useful to present data relating to the number of contributions that users made as a whole, rather than as an average.Another important piece of information relates to the gender distribution at the Twitter conference. According to the RSC membership department, 27.7% of their members are female and 72.3% male, representing an uneven distribution of members by gender.The ASTPC was organised as a free event to encourage the sharing and exchange of knowledge through the use of social media. This pilot scheme saw a potential Twitter audience of over a quarter of a million people, demonstrating that posters can quite easily be shared using Twitter, to potentially reach thousands of times more people than they could at even the largest of international scientific conferences. Every day millions of people across the world access Twitter, new Twitter connections are being made, and opinion and discussion is stimulated as a result, while the introduction of hashtags has only served to group discussions together and augment the potential reach of a niche discussion. Even without an organised hashtag or event, a poster can have a larger potential audience than it would at a conference, where the audience will, at the very most, be a few hundred people. The number of useful exchanges between participants is less easy to enumerate, as one cannot quantify the level of interaction between academics in a given poster session and compare it to the number of tweets. A face-to-face conversation about a poster that is in front of two researchers will no doubt be more fulfilling in terms of knowledge exchange, because the conversation is not limited to a few characters. In the Twitter conference, there was an average of 4.5 tweets per person, suggesting that the level of academic discussion was somewhat limited. However, this is not to say that knowledge was not exchanged, but simply that the discussion part of the ASTPC may have been shorter than that of a standard poster session at a conference. This does not account for exchanges that may have been made in private, via emails or direct messaging facilities on Twitter.2 being produced, the majority of which came from the 1.25 million kilometres of air travel required for delegates to travel to the conference.As a concept, the Twitter poster conference has some definite advantages over a more traditional poster format, with the data analysed in this study supporting the notion that it is an extremely useful way of broadening the reach and potential audience of a poster. Another advantage is the ease of knowledge exchange for those who lack the confidence or interpersonal skills required for efficient face-to-face communications. It is also apparent that Twitter can decrease the cost of the poster to the researcher because it does not need to be carried as supplementary luggage during air travel; it also avoids potentially exorbitant printing fees at conferences for those who have lost or previously been unable to print their poster. Furthermore, the carbon footprint of a Twitter-only conference is extremely low (unquantified), whereas an international conference will exhibit a substantial carbon footprint, mainly due to air travel. Research by MMU  has recently found that an international conference of 178 delegates resulted in the equivalent of 177 tonnes of COPeriscope to live-stream the entire presentation. The Twitter format could also potentially be used as a hybrid with the PICO concept discussed in the introduction.The nature of Twitter means that more in-depth forms of communication are limited through online exchanges, which could be seen as a disadvantage of the format. However, after the initial exchanges the delegate has the opportunity to extend any interactions further. This can be achieved by the exchange of emails, phone numbers, and Skype IDs for example, or in private messaging facilities over Twitter, meaning that more in-depth chats about the research in question can still be facilitated. Future Twitter conferences should incorporate a feedback device for participants (presenters or otherwise) to understand what benefits the format has to the participant and whether they would participate again, with or without the element of competition. The lack of interpersonal communication is disadvantageous, but should not detract researchers from a Twitter conference. It could be used alongside the traditional poster session, or as a separate entity of its own if a researcher is unable, or prefers not, to travel. Given Twitter’s recent foray into video streaming, the concept could also be adapted to include oral communications, in which researchers could tweet short video vignettes of their work, or even useIn specific relation to the RSC, the results presented here indicate that whilst Twitter could be used as a tool to address the gender inequality, more needs to be done to encourage female participants to participate in the active Twitter discussions.The world’s first Twitter conference could be considered a success in terms of potential audience, ease of knowledge exchange and lack of travel requirement. The conference reached out to many researchers across the world, and created an opportunity for participants to share their work not only with academics, but also with other interested parties such as writers, industries, friends and family, and even policy makers. Over 80 posters were tweeted with the hashtag #RSCAnalyticalPoster, reaching an audience potentially as large as 375,000 people, and the format of a Twitter poster conference has the potential to allow for research to be shared more quickly and cheaply, and in a more environmentally friendly manner. Despite some potential issues relating to prolonged exchanges, there is no doubt that the hybridisation of the academic conference and social media is something that could and should be seen more regularly in the future. We expect the use of social media to significantly expand scientific conferences due to the advantages identified above, and also to be utilised alongside conferences where physical participation occurs. The benefits of social media can help researchers organise their poster viewings at large conferences, for example future ACS conferences, helping to potentially improve the poster session experience for all participating researchers. Such an improvement in engagement will enhance scientific communication and knowledge exchange, ultimately leading to more successful conferences. Future investigations will focus specifically upon detailed Twitter interactions in such an academic context and investigate whether the interactions can be classified as “meaningful”, in order to establish the true impact of a social media only conference.The data referenced by this article are under copyright with the following copyright statement: Copyright: © 2016 Randviir EP et al.Data associated with the article are available under the terms of the Creative Commons Zero "No rights reserved" data waiver (CC0 1.0 Public domain dedication).10.5256/f1000research.6992.d101516  and so do not reflect on the success or value of this activity.It may have been useful to solicit some feedback from participants, including the presenters, as to how they felt about the experience, the quality of the exchange, and the interest in doing again.I have read this submission. I believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard. While we understand the reviewer’s thought regarding the competitive element, we feel that most scientific conferences of this nature offer prizes for the best posters. With this in mind, we feel that the competitive element is no different to other conferences and assume that the participation does not change based upon this. We have noted this in the experimental section.The referee makes an excellent point regarding the nature of exchanges. We feel that with the information we have collected, we cannot extract enough quality data to report within this paper, but future work will focus more on a detailed analysis of Twitter interactions and develop a model for the level of meaning in each interaction. We have pointed this out within the updated manuscript in the conclusion, and have also discussed in the text that we feel further detail regarding exchanges would be useful.We agree that a feedback method should have been incorporated and this will be included in future works. The discussion section has been changed slightly to reflect the fact that this was an opportunity missed.We have removed the conclusion regarding lack or travel and carbon footprint, but remain optimistic that Twitter improves ease of knowledge exchange, if not directly then indirectly.We thank the reviewer for providing an insightful review that will not only help improve the manuscript, but will also affect our future work. This is an interesting paper that describes and evaluates a Twitter poster conference. The authors have clearly highlighted the potential reach that Twitter provides scientists wishing to engage others with their work and the ways in which Twitter as a medium has distinct advantages over traditional face to face interaction. In doing so this paper provides a useful starting point for a discussion about the use of social media as a conference format.The authors acknowledge the limitations of twitter (e.g. limited ability to have an in depth discussion) but from the presented data they are unable to discuss this in any detail. In my opinion this is an area that should be investigated further. As an initial foray into the field this is a (very necessary) descriptive rather than investigative piece. In order that I might fully evaluate the value of the model I would have like to have more information about the broader themes of the tweets themselves – what proportion of them asked/answered a relevant question? How many were simply an indication of approval or an acknowledgement of participation in the virtual meeting etc. I don’t think that this information needs to be added to the current paper  but I would encourage the authors to follow this work with such an analysis if that is possible.There is one minor change that I think would increase the initial readability of the paper. On first reading I found myself confused about the nature of the conference, perhaps revealing a prejudice based on prior experience and pre-conception I assumed that the Twitter poster conference was an adjunct to a physical meeting rather than a stand alone event. It may help readers to avoid this mistake if the authors explained that more clearly in the abstract?I have read this submission. I believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard. We are in agreement that this area should be investigated further, and have included some information as to how we will extend this work in the future, specifically relating to the nature of Twitter exchanges and in developing a level of meaning based upon the information within exchanges.The referee makes a valid point regarding the ambiguity surrounded this event as a standalone conference. The abstract has been changed to reflect the nature of the conference to make this less confusing.We thank the referee for their insightful comments and feel that they are of benefit to the manuscript both now and in the future.


Passive leg raising (PLR) has been suggested as a simple diagnostic tool to guide fluid administration in critically ill patients . AlthougIn this single-centre prospective study, mixed ICU patients equipped with a PiCCO system received fluid therapy on the basis of PLR test results in the first 48 hours of treatment, after careful introduction of a new PLR-driven protocol. Exclusion criteria were increased abdominal pressure, fracture of leg or pelvis, deep vein thrombosis, head trauma and pregnancy. The control group existed of patients admitted to the ICU 1 year prior to the introduction of the protocol.P = 0.11) and 48 hours . However, compliance with the protocol was poor (56%). After 2/11 positive tests, fluid was not administered; and after 21/39 tests, fluid was administered despite a negative test result (Figure We included 21 patients in each group. There was no significant differences in the fluid balance between the control and study group after 24 hours (5.0 ± 2.9 l vs. 3.6 ± 2.7 l, The implementation of a PLR-driven protocol of fluid administration did not change mean fluid balances after the first 48 hours. Noncompliance with the protocol was an important confounder.