EGF receptor (EGFR) frequently result in hypomagnesemia in human patients. In contrast, EGFR tyrosine kinase inhibitors do not affect Mg2+ balance in patients and only have a mild effect on Mg2+ homeostasis in rodents at elevated doses. EGF has also been shown to affect phosphate (Pi) transport in rat and rabbit proximal convoluted tubules (PCT), but evidence from studies targeting EGFR and looking at Pi excretion in whole animals is still missing. Thus, the role of EGF in regulating reabsorption of Mg2+ and/or Pi in the kidney remains controversial. Here, we inject mice with the anti‐EGFR monoclonal antibody ME‐1 for 2 weeks and observe a significant increase in serum Pi and mild hypomagnesemia, but no changes in Pi or Mg2+ excretion. In contrast, a single injection of ME‐1 resulted in hyperphosphatemia and a significant reduction in Pi excretion 2 days after treatment, while no changes in serum Mg2+ or Mg2+ excretion were observed. Dietary Mg2+ deprivation is known to trigger a rapid Mg2+ conservation response in addition to hyperphosphatemia and hyperphosphaturia. Interestingly, one dose of ME‐1 did not significantly modify the response of mice to 2 days of Mg2+ deprivation. These data show that EGFR plays a significant role in regulating Pi reabsorption in the kidney PCT, but suggest only a minor role in long‐term regulation of Mg2+ transport in the distal convoluted tubule.Monoclonal antibody therapies targeting the  Within hours of Mg2+ deprivation, animals maintained on a Mg2+‐deficient diet present hypomagnesemia despite development of a rapid Mg2+ conservation response. These animals also show disturbed Pi, Ca2+, K+, and Na+ balance  pointed at EGF as a significant factor in the regulation of Mg2+ homeostasis , regulated Mg2+ reabsorption is mostly concentrated at the distal convoluted tubule (DCT) via the apical Mg2+ channel TRPM6. In the kidney, the EGF receptor (EGFR) is expressed in the TAL and DCT , with further reduction in plasma Mg2+ taking place as treatment continued for up to 9 weeks . Six doses of ME‐1 or control rat IgG (40 mg/kg) were administered intraperitoneally at regular intervals for a period of 2 weeks. On the last day of the experiment, mice were individually housed in metabolic cages, food and water consumption were measured and 24 h urine was collected under mineral oil to prevent evaporation. At the end of the experiment, mice were anesthetized using AvertinTM  and approximately 800 μL of blood was collected using cardiac puncture. To produce serum, blood was allowed to clot at room temperature for 30 min and centrifuged for 20 min at 3500 g. For the experiment studying the effect of ME‐1 on the Mg2+‐saving response triggered by Mg2+ deprivation, deionized drinking water and experimental diets were provided ad libitum. Both Mg2+‐deficient experimental diet  and Mg2+‐control diet  contained 0.45% w/w phosphorus, 0.6% w/w Ca2+ and 2200 IU/kg vitamin D. Prior to the experiment, all mice were maintained in Mg2+‐control diet for 6 days. Next, mice were injected with one dose of ME‐1 (40 mg/kg) or control IgG and allocated to their respective experimental groups and diets (Mg2+‐deficient or Mg2+‐control). Next day, mice were housed in metabolic cages, food and water consumption were measured, and 24 h urine was collected. At the end of the experiment, mice were anesthetized and serum was obtained as before. All experimental procedures were approved by the institutional animal care and use committee of The College at Brockport, State University of New York.Ten‐week‐old C57BL/6J male mice  were maintained in a temperature‐controlled room under a 12 h light‐dark cycle. For the 2‐week ME‐1 treatment, mice were maintained on standard diet  and tap water ad libitum. ME‐1  was kindly provided by ImClone (Eli Lilly). Control rat IgG  was depyrogenated using a Detoxi‐GelμL of serum was added to 150 μL of working solution and incubated for 5 min. Absorbance of samples was read at 590 nm  and the concentration in samples was calculated from a standard curve prepared using known amounts of bilirubin. Bilirubin standards were produced by dilution of a bilirubin stock solution in 5% BSA/phosphate‐buffered saline (PBS). A bilirubin stock solution was prepared by diluting 14.6 mg of bilirubin in 1 mL of 0.1 N NaOH, and then diluting 20 μL of the resulting solution in 980 μL of 5% BSA/PBS. Colorimetric assays for determination of Mg2+  and inorganic phosphorus  in serum and urine, and Ca2+ in urine  have been described before . Total Ca2+ in serum was analyzed using flame photometry following precipitation as calcium oxalate according to the manufacturer's instructions as described before . Results from different experimental groups were compared using an independent sample Patients receiving EGFR antibody therapy often experience skin rashes in areas rich in pilosebaceous units. SCID mice treated with ME‐1 display inflammatory skin changes that result in a characteristic wavy hair pattern , showing that at the dose used, ME‐1 induced no adverse effects. As shown in Table i in ME‐1‐treated animals increased to a level bordering hyperphosphatemia. Other electrolytes, including Ca2+, Na+, and K+, remained unchanged. No differences were observed in urine output or electrolyte excretion between treated and untreated animals.After 2 weeks of ME‐1 administration, mice were placed in metabolic cages and 24‐h urine was collected. Mice were then sacrificed and serum was obtained. No significant changes in body weight or water and food intake were observed between experimental and control groups (data not shown). EGFR‐targeted anti‐tumor therapies have been shown to occasionally disrupt bilirubin metabolism and produce hepatotoxicity . These results are in line with previous studies, thus indicating that treatment with a EGFR‐targeted monoclonal antibody has a similar effect on mice Mg2+ metabolism as treatment with the EGFR tyrosine kinase inhibitor erlotinib.Previous studies on the ability of the EGFR inhibitor erlotinib to induce hypomagnesemia in rodents showed no effect after 10 days of treatment, and only a moderate effect (10–14%) after 3 weeks of treatment , potentially increasing Pi excretion ‐1  in HEK293 cells (Choi et al. 2+ balance. Furthermore, sustained ME‐1 administration resulted in a modest effect on serum Mg2+ without visibly affecting Mg2+ excretion. In contrast, ME‐1 had a profound effect on Pi metabolism that became apparent from the first dose of ME‐1. Thus, in mice, EGFR appears to be more involved in the regulation of Pi balance than in Mg2+ metabolism.In summary, our study shows that inhibition of EGFR with a single dose of ME‐1 had no effects on MgNone declared.


Nanoscience and Nanotechnology became the trend of the 21st century, influencing many areas such as electronics, biology, medicine, aerospace, agriculture, and the engineering of novel materials. Recently a new aspect of nanoscience and nanotechnology appeared and has been rising rapidly ever since: functional nanostructures, intelligent nanostructures for targeted applications. In the present Thematic Series a bright spectrum of such targeted functional nanostructures is presented demonstrating the unique possibilities of engineering at the nanometer scale. The self-organization of nanoparticles, nanowires or nanotubes and the introduction of those structures into various materials made it possible to solve long-standing problems. Examples presented in this Thematic Series are:the problem of treatment of multidrug-resistant tuberculosis, which can be resolved using the invented nano-encapsulated medicines penetrating through the cell membrane of the tuberculosis bacilli ,new applications of graphene-based nanostructures –4,smart nanoparticles with antitumor activity ,photonic crystals and flexible membranes –7 for viA lot of other unusual applications of functional nanostructures are presented in over 40 articles of this Thematic Series, giving the possibility to gain new knowledge about the rapidly developing area of nanoscience and nanotechnology.The idea to this Thematic Series appeared during the international conference “NANO-2016: Ethical, Ecological and Social Problems of Nanoscience and Nanotechnologies”, which took place in May 2016 in Chisinau, Moldova. It presented new technological approaches for assembling of functional nanostructures and nanomaterials with special properties. As the guest editor of this Thematic Series I would like to thank all colleagues and highly experienced experts who submitted their manuscripts with novel results, new ideas, and technological approaches. I believe that this Thematic Series will attract attention of scientists, technologists, engineers and will find many readers. The professional and friendly editorial support by the Production Team of the Beilstein-Institut is greatly acknowledged.Anatolie SidorenkoChisinau, January 2017


Arteriovenous malformation (AVM) is a congenital lesion commonly associated withintracranial hemorrhage. We describe a woman with an AVM (Spetzler-Martin grade V)and presenile progressive dementia. The association between AVM and cognition isdiscussed. Arteriovenous malformation (AVM) has a congenital origin and is composed of a tangle ofarteries and veins connected by fistulae, where the central part is a nidus. The mostcommon symptom is hemorrhage, but other symptoms include headache, seizures, stroke-likesymptoms, and ischemic stroke. Cognitive findings are rarely reported in the literature,with some descriptions of a progressive course among case series reports.,We described a 63-year-old illiterate housewife with a history of right motor partialseizures and generalization since the age of 23 years. In July of 2013 she soughtmedical care at the Emergency Room due to acute right hemiparesis; during theinvestigation a predominantly left temporoparietal AVM was disclosed . Atthe time, the treatment elected was conservative with no indication for surgery,endovascular embolization or radiosurgery.The husband reported she had a three-year history of progressive difficulties ininstrumental activities of daily living, such as cooking and housekeeping, shopping andfinancial control. Concomitantly, he observed that she presented difficulties in theacquisition of new information, and exhibited topographic and temporal disorientation.Cognition and functioning progressively declined with partial dependency for basicactivities of daily living ; apathy was the predominantneuropsychiatric symptom . Therewas no family history of dementia. She was in use of medication for seizure control. Neurological examination revealed right hemiparesis, right tactile and painhypoesthesia, poor fluency, temporal and spatial disorientation, and a Mini-Mental StateExamination score of 5 points .The MRI performed in 2016 showed a massive AVM in the left hemisphere of thefrontotemporoparietal region (9.2 × 6.0 cm) with parenchymal compression andmicroangiopathy. There were many low-signal spots within or around the mass on T1, T2,and fluid-attenuated inversion recovery (FLAIR) sequences: the "flow voids" of feedingarteries with ectasia  and draining veins . There was no sign of hemorrhage .Her EEG showed diffuse disorganization and acute waves in the left temporal region. Adiagnosis of dementia caused by AVM was defined (chronic hypoperfusion andspace-occupying lesion). In the literature there are scant data on cognitive deficits observed in AVM patients.Cognition is described in terms of neurological deficit or using a weak definition ofdementia. We used a well-defined criteria of dementia based on multiple cognitiveimpairments, behavioral disturbance, and difficulties in activities of daily living. Cognitive impairment was observed in a case series of 43 patients by Olivecrona &Riives in 1948; where they had reported "mental impairment/deterioration" or "memorydeterioration" in 11 individuals.AVMs cause neurological dysfunction through several mechanisms such as hemorrhage insubarachnoid space, intraventricular or intralobar hematoma, seizures, and progressiveneurological deficit.In our case, tangles of arteries and veins caused major compromise of the left cerebralhemisphere, involving the thalamus, hippocampus, posterior cingulate gyrus, precuneusand temporo-parietal junction. These areas are part of the limbic system and defaultmode network, both heavily involved in cognition. ,,Focal neurological deficit can be the first sign in 5% to 15% of AVM in hospital-basedstudies but are relatively rare. In a large sample, 7% of 735 untreated AVM presentedwith focal neurological deficit; with four possible outcomes: stable, progressive,fluctuating or reversible. Among these focal deficits, cognition was compromised in 10out of 53 cases and progressive in four patients.,There are more reported cases associating cognitive impairment to dural arteriovenousfistula, as part of AVMs; these cases have shown frontal lobe dysfunction; temporal,spatial and personal disorientation and in calculus, with rapidly progressive cognitivesymptoms and partial recuperation after endovascular treatment.Our patient may have had a low pre-morbid cognitive level since AVM developed throughouther life and she is illiterate with an undemanding activity. Functional decline was onlynoted in the past few years, evolving to overt dementia. Although her history reflects adegenerative condition with chronic and progressive involvement of cognition andfunction, we observed a consistent cause of disability with no hippocampal atrophy,presenile onset with no family history, and a previous poor background. The patientpresented a rare manifestation (dementia) of a massive AVM, where focal motor andsensory deficits are relatively scarce in reported series.


Although alcohol is socially accepted in most Western societies, studies are clear about its associated negative consequences, especially among university and college students. Studies on the relationship between alcohol-related consequences and both beverage type and drinking onset, however, are scarce, especially in a European context. The aim of this research was, therefore, twofold: (1) What is the relationship between beverage type and the negative consequences experienced by students? and (2) Are these consequences determined by early drinking onset? We will examine these questions within the context of a wide range of alcohol-related consequences.The analyses are based on data collected by the inter-university project ‘Head in the clouds?’, measuring alcohol use among students in Flanders (Belgium). In total, a large dataset consisting of information from 19,253 anonymously participating students was available. Negative consequences were measured using a shortened version of the Core Alcohol and Drug Survey (CADS_D). Data were analysed using negative binomial regression.Results vary depending on the type of alcohol-related consequences: Personal negative consequences occur frequently among daily beer drinkers. However, a high rate of social negative consequences was recorded for both daily beer drinkers and daily spirits drinkers. Finally, early drinking onset was significantly associated with both personal and social negative consequences, and this association was especially strong between beer and spirits drinking onset and social negative consequences.Numerous negative consequences, both personal and social, are related to frequent beer and spirits drinking. Our findings indicate a close association between drinking beer and personal negative consequences as well as between drinking beer and/or spirits and social negative consequences. Similarly, early drinking onset has a major influence on the rates of both personal and social negative consequences. The earlier students started drinking, the more negative consequences they experienced during college or university. Several (policy) interventions are discussed. This study is the first to incorporate detailed information on both beverage type and drinking onset, and its associated negative consequences, as measured by the CADS_D, in a large student population.The online version of this article (10.1186/s12889-018-5120-7) contains supplementary material, which is available to authorized users. Despite the fact that alcohol is a socially accepted drug in most Western societies, there is widespread empirical evidence of its associated negative consequences . AccordiAlcohol-related negative consequences should not be underestimated. First of all, alcohol consumption can lead to a number of immediate health consequences affecting the drinker, such as (short term) physical discomfort , but also (long term) health conditions such as neuropsychiatric conditions, gastrointestinal diseases, and cancers . In addiBesides consequences for the individual, alcohol use can also harm other people in cases of aggression, assault, car accidents, or property damage. A study by Hingson et al.  estimateDespite the widespread empirical evidence on the negative consequences of alcohol misuse, the available studies do have some shortcomings. First of all, both beverage type and drinking onset seem to be important predictors. Indeed, some studies have indicated that beer or spirits drinking, as well as starting to drink at a younger age, are associated with alcohol-related problems or injuries –20. HoweThe primary aim of this research is to investigate two key questions: 1) What is the relationship between beverage type and the negative consequences experienced by students? and 2) Are these consequences determined by early drinking onset? Based on the available studies, we would expect beer and spirits drinking to be associated with alcohol-related consequences. Moreover, we hypothesize that the younger students start drinking, the more consequences they will experience as a student. This research thus expands on current literature by thoroughly investigating the association between beverage types  and early drinking onset; and a range of negative consequences experienced by students, as measured by the CADS_D. To the best of our knowledge, this study is the first to examine the negative consequences of alcohol use with this amount of detail in a large student population. By obtaining more detailed results, we hope these can be of particular importance to both micro-level health care workers and macro-level policy makers in order to prevent alcohol-related negative consequences among students.This retrospective study is based on a substance use data collection among university and college students in Flanders (Belgium) in 2013, entitled ‘Head in the clouds?’. The survey was made available for four to six weeks in eleven participating universities and colleges between February and April 2013. Students were invited by e-mail and other methods  to participate anonymously. No reminder was sent [n = 6867) and 64.33% women (n = 12.386). Mean age of participants was 21.12 years (SD = 3.25). We compared sex and institution distributions between our sample and the total student population enrolled in the six participating institutions [χ2 = 673.07, p <  0.001) and students from the university of Ghent, ‘KHLimburg’ College and ‘Group T’ College .Five colleges were excluded from the sample because of their low response rate (< 3.5%). The remaining six institutions were located in different regions of Flanders . In total 19,253 college students (22.1% response rate) were included in the sample. This response rate is similar to other large-scale online surveys among college students , 36. Theitutions . As showDemographic information: sex , age (in years), living situation ; attending university/college.Frequency of alcohol use. This variable was measured for each beverage type separately. Respondents were asked how often they drink beer, wine, other non-distilled beverages such as Martini and sherry, and spirits during the academic year, the exam period and holidays. Response categories were 1 = never, 2 = less than or once a month, 3 = less than once a week but more than once a month, 4 = once a week, 5 = more than once a week but less than daily, 6 = daily. As a categorical variable, multiple dummy codes were created to include in the model. Since the intention of this research is to give a representative image of alcohol use among students during the academic year, we use the variable ‘frequency of alcohol use during the academic year’. Both exam and holiday periods are outside of our scope of interest since drinking behaviour can differ in these periods.Drinking onset. Respondents needed to indicate at what age they drank alcohol for the first time (either a sip or a whole drink). This open-ended question was asked for each beverage type. During analysis, responses were coded in six categories: less than 15 years old, 15, 16, 17, 18 and more than 18 years old. Similar to the previous variable, multiple dummy codes were created.Negative consequences of alcohol use were measured using the CADS [the CADS . Particithe CADS . The comthe CADS , we inveThe two factors , each measured as the sum of the underlying items, were used as dependent variables in the regression models. The complete list of consequences is thus only used for descriptive purposes. The independent variables of interest consisted of drinking frequency and drinking onset. Both variables were measured for different beverage types. We controlled for age, sex, institution and living situation. Frequency of other substance use  were also used as control variables to ensure that consequences of alcohol use were not related to other drugs.We used negative binomial regression to test whether drinking frequency and drinking onset for several beverage types were associated with the personal and social drinking consequences. Prior research has shown that the use of negative binomial regression is the best method for analysing these overdispersed count data , 42. SinNegative binomial regression analyses were conducted with IBM SPSS Statistics 22.n = 9111) indicated drinking beer regularly . With regard to wine, non-distilled beverages and spirits, regular drinking was less prevalent than beer . One third  indicated drinking one beverage type regularly, 17.89% (n = 3085) two beverage types, 5.71% (n = 985) three beverage types and 1.35% (n = 233) all four beverage types. The majority of participants who ever drank alcohol and started drinking beer before the legal age limit of 16 years, also started drinking wine  before the legal age of 16 years, and/or non-distilled beverages  before 18 years and/or spirits  before 18 years.In total, 96.05% of the participants stated that they had used alcohol before, of which 97.04% had used alcohol in the past 12 months. Half of these students , “became nauseated or vomited” (56.53%) and “missed a class” (43.95%). Driving while intoxicated or under the influence was also reported by 8.21% of the participants. Moreover, 23.42% of the participants had not experienced any of the stated consequences during the past year. However, 19.51% of the students had encountered six or more different consequences. Participants experienced a mean number of 3.15 different types of consequences in the past year (SD = 2.82).The top three most frequently encountered consequences of the CADS were: “The two variables ‘Personal negative consequences’ and ‘Social negative consequences’ served as dependent variables in our regression models, shown in Tables p <  0.001) as well as daily beer drinkers  experience strongly increased rates, as indicated in Table p < 0.001 and IRR = 1.11; p < 0.05, respectively), and drinking non-distilled beverages less than once a week but more than once a month, indicating a lower rate of social negative consequences .Negative binomial regression indicates a high incident rate ratio (IRR) of personal negative consequences for beer drinkers. As shown in Table The age at which students started drinking alcohol is also related to negative consequences experienced. The association was especially strong between the onset of beer and spirits drinking and social negative consequences. Compared with < 15 year drinking onset, the rates for beer drinking were as follows: 0.88 (15 year olds), 0.67 (16 year olds), 0.61 (17 year olds), 0.52 (18 year olds), 0.56 (> 18 year olds). These results were all significant. Regarding spirits intake, the data were as follows: 0.90 (15 year olds), 0.75 (16 year olds), 0.66 (17 year olds), 0.62 (18 year olds), 0.61(> 18 year olds). This means that a student who started drinking spirits at the age of 19 will encounter approximately 40% lower rates of social negative consequences compared with those who started drinking spirits before the age of 15. All results were significant, except for the age category of 15 year olds. For almost all age categories, wine and non-distilled beverage drinking onset were significantly associated with rates of social negative consequences, but the associations were less strong compared to those for beer and spirits.The aim of the current research was to examine the association between beverage type and early drinking onset, and the negative consequences experienced by students. Research on this topic is particularly relevant among young people and more specifically university and college students, since the university or college experience is often characterized by high levels of problematic alcohol use , 3.Our analyses were based on data from the ‘Head in the clouds?’ survey, in which nearly 20,000 students from several universities and colleges in Flanders (Belgium) participated in 2013 [The descriptive statistics make clear that 8.2% of the respondents in this sample drink/take drugs and drive . Although this percentage is lower than in the US , it stilSecondly, our study findings indicate that beer and spirits drinking frequency is closely related to rates of both personal and social negative consequences, with a strong association between daily beer drinking and personal negative consequences as well as between daily beer and/or spirits drinking and social negative consequences. Although more research is needed to disentangle the reasons why specific beverage types are associated with alcohol-related negative consequences, several possible explanations can be given. Firstly, previous research has indicated that beer and spirits drinkers exhibit riskier drinking patterns compared to people who drink other alcoholic beverages , 46–49. Thirdly, our results show that the earlier students start drinking, the more negative consequences they will experience during college or university. This is especially true for young beer drinkers. This association could partly be explained by the fact that students who start drinking at an early age are more likely to be involved in frequent heavy drinking later in life, which increases the risk of negative alcohol-related consequences . AnotherPreventing alcohol misuse and negative consequences during college or university requires a comprehensive approach in which multiple parties  need to be involved and which needs to start early in life, especially during adolescence. On a micro- and meso-level these research results are of particular importance to health care workers who work with adolescents and/or students as the results draw attention to the numerous risks related to excessive beer and spirits drinking, as well as to early drinking onset. Questioning patients about their drinking onset age and educating them on the alcohol-related negative consequences would be an important step in this respect . MoreoveDespite the widespread empirical evidence of alcohol-related negative consequences, alcohol regulation policies often have a relatively low priority on the public policy agenda . ChangesThere are some limitations present in this study. Firstly, longitudinal data are not available, so the results cannot be compared over time and thus causal relationship cannot be determined. However, the negative consequences of alcohol use were measured with the question ‘How often have you experienced the following consequences as a result of your drinking during the last year’. The question thus already involves the causality we were investigating. Moreover, the association between drinking onset and alcohol-related consequences could not be interpreted in the other direction, because of the inherent chronological order of the two variables. Secondly, a significant number of negative consequences were excluded from the analyses since these were either encountered by less than 5% of participants or had loading difficulties in the factor analysis. Nonetheless, these items remain important for future studies. Thirdly, although not mentioned in the article, we also did some additional analyses in which we included the quantity of alcohol consumed on drinking days and problematic drinking behaviour such as frequency of binge drinking as control variables. However, because of the high correlation between these additional control variables and some of the other predicting factors  as well as the high robustness of the initial model, we have not included these additional control variables in the model. For future studies it might be interesting to search for other factors that are associated with the dependent variable. Finally, the response rate for our sample was rather low. Although it is similar to other large-scale online surveys , 36, carThe results of this study draw attention to the numerous risks related to excessive beer and spirits drinking as well as early drinking onset. To the best of our knowledge, this study is the first to incorporate detailed information on both beverage type and drinking onset and its associated negative consequences in a large student population in a European (Flemish) context. These results are especially important for both micro-  and macro-level (e.g. legislative) interventions which should focus on reducing alcohol intake and delaying drinking onset age among young people as these factors are significantly related to both personal and social negative alcohol-related consequences.Additional file 1: Table S1.Core Alcohol and Drug Survey – Consequences scale. This table represents the complete CADS scale, consisting of 19 negative consequences of alcohol use. (DOCX 12 kb)


N = 3389). Results showed there were 1.4 % addicted gamers, 7.3 % problem gamers, 3.9 % engaged gamers, and 87.4 % normal gamers. Gender  and age group (being young) were positively associated with addicted-, problem-, and engaged gamers. Place of birth  were positively associated with addicted- and problem gamers. Video game addiction was negatively associated with conscientiousness and positively associated with neuroticism. Poor psychosomatic health was positively associated with problem- and engaged gaming. These factors provide insight into the field of video game addiction, and may help to provide guidance as to how individuals that are at risk of becoming addicted gamers can be identified.Video gaming has become a popular leisure activity in many parts of the world, and an increasing number of empirical studies examine the small minority that appears to develop problems as a result of excessive gaming. This study investigated prevalence rates and predictors of video game addiction in a sample of gamers, randomly selected from the National Population Registry of Norway ( Video gaming is one of the most popular contemporary recreational activities. It has been shown that 59 % of all Americans play video games . Thus, a total of 10,081 valid answers were received, resulting in a response rate of 43.6 %. A subset of 3389 respondents, aged 16–74 years  reported playing video games during the last 6 months.N = 10,081) and one including active gamers only. Furthermore, prevalence rates are reported using Charlton’s  were calculated in four different ways. Two different samples were used, one including all participants .General questions about participants’ background included gender, age, marital status (married/cohabiting or single/separated/divorced/widowed/widower), number of children they had care responsibilities for (from zero to five or more), highest completed education (from not ended primary school to completed PhD), personal income before taxes in the last year in bulks of 100 000 NOK , employment status , and birthplace .strongly disagree to 5 = strongly agree). Internal consistency  for the scale in the current study was 0.80 for extraversion, 0.75 for agreeableness, 0.68 for conscientiousness, 0.70 for neuroticism, and 0.66 for intellect/imagination (n = 3622).Personality traits were assessed using the Mini International Item Pool . A total score of all eight items was divided by eight and used in the analysis.An eight-item scale to assess psychosomatic health symptoms were constructed  based on previous scales developed for psychosomatic symptoms . Internal consistency  for the scale was 0.84 (n = 3622).The seven-item version of the Game Addiction Scale for Adolescents , three age groups were constructed , marital status was dichotomized , place of birth was categorized into three groups , level of education was categorized into three groups , employment status was dichotomized (1 = unemployed and 2 = employed).The demographic variables were recoded in the following manner: gender was dichotomized  and below (2) the median for the personality traits, and creating groups scoring above (2) and below (1) the median for psychosomatic health.Descriptive statistics of nominal variables were calculated in terms of distribution. Pearson product–moment correlation coefficients were calculated in order to investigate the interrelationship between the predictor variables in the study. Using the sample that reported playing video games during the last 6 months, crude and adjusted multinomial regression analyses were conducted with the categorical video gaming variable  as the dependent variable. “Normal gamer” was used as the reference category. Gender, age, place of birth, marital status, education level and employment status were entered in step one, personality was included in step two, and psychosomatic health were entered in step three. The prerequisites for conducting this type of analysis were fulfilled. The statistical analyses were conducted using N = 3389). Table Table Table r = 0.35), marital status and education (r = 0.38), and older age group and marital status (r = 0.38).Table Table Table In both the crude and adjusted analyses, being addicted-, problem- or engaged gamer was significantly and negatively associated with gender, indicating that male respondents were more likely than female respondents to belong to all of these categories.Being 31–50 years old was significantly and negatively associated with being an addicted- or problem gamer compared to the contrast group (16–30 years) in both the crude and adjusted analysis. Being 51–80 years was negatively associated with being an addicted gamer, problem gamer or an engaged gamer compared to the contrast group in the crude analysis. The effect was still significant when adjusting for personality traits, but the association with being an engaged gamer did not remain significant when adjusting for psychosomatic health.Being born in Africa, Asia, South- or Middle America was positively and significantly related to being an addicted- or problem gamer in both the crude and adjusted analysis. In the crude analysis, a high score on extraversion was significantly and negatively associated with being an addicted- or engaged gamer compared to those having a low score. In the adjusted analysis, none of the associations remained significant. In the crude analysis, agreeableness was significantly and negatively associated with being an addicted-, problem-, or engaged gamer. In the adjusted analysis only, the negative association with being a problem gamer remained. For conscientiousness there was a significant and negative association with being an addicted-, problem- or engaged gamer both in the crude- and adjusted analyses. In the crude analysis, neuroticism was positively and significantly associated with being an addicted-, problem- or engaged gamer. However, in the adjusted model, the association with being an engaged gamer did not remain significant. In the crude and adjusted analysis, intellect/imagination was significantly and positively associated with being a problem gamer.Having a low score on the psychosomatic health scale was negatively associated with being an addicted-, problem- or engaged gamer in the crude analysis. In the adjusted model, the association with being an addicted gamer did not remain significant.χ2 = 358.24, df = 45, p < .01). Furthermore, the model as a whole explained between 10.6 % (Cox and Snell R square) and 17.3 % (Nagelkerke R squared) of the variance in video game addiction and correctly classified 88.3 % of all the cases.The full model containing all predictors  was statistically significant  and the prevalence of problem gamers (3.0 %), were lower than a previous Norwegian study , problem (7.3 %) and engaged (3.9 %). However, the prevalence of addicted gamers was lower than what has been found worldwide (Ferguson et al. The results of the present study are in line with previous research stating that males report more problems with gaming than females (Brunborg et al. Respondents that were born in Africa, Asia, South America or Central America were 4.9 times more likely to belong to the group of addicted gamers, and 3.1 times more likely to belong to the group of problem gamers, compared to respondents born in Norway. The present authors have not been able to identify previous research investigating video game addiction among immigrants. Previous findings are mixed as to whether immigrants are in the risk group for mental health problems in general (e.g., Bhugra and Jones Video game addiction was independent of level of education, and is in accordance with previous research (Rehbein et al. Previous studies have found an association between unemployment and problematic video game and internet use (Elliot et al. In contrast to Peters and Malesky , no signUnlike previous studies (Rehbein et al. By using a sample randomly selected from the national population registry, the results can be generalized across the video gaming population. There is a need for further population-based studies given the lack of such studies to date (Wenzel et al. Everquest (Williams et al. One shortcoming of the present study is that it did not differentiate between different types of games. Studies have shown that characteristics of games can be of importance in the development of video game addiction (King et al. The present study showed the prevalence of addicted gamers to be 1.4 %, problem gamers to be 7.3 % and engaged gamers to be 3.9 %. The results identified the following factors to be associated with video game addiction: being of male gender, being young in age, living alone, being born in Africa, Asia, South America or Central America, scoring low on conscientiousness, scoring high on neuroticism, and having poor psychosomatic health. These factors provide insight into the field of video game addiction, and may help to provide guidance as to how one can identify people that are in risk of becoming addicted gamers.


We examined the relationship between dog walking and physical activity within and between four US cities and Australia and investigated if dog walking is associated with higher perceived safety in US and Australian cities.n = 1113) in the Pet Connections Study completed a cross-sectional survey. Data were collected across four study sites; three in the US  and a fourth in Australia (Perth). Physical activity, local walking, dog walking, and individual and community perceptions of safety were analysed for dog walkers and non-dog walkers for each study site. Between-city comparisons were examined for dog walkers.Dog owners (p ≤ 0.01). Compared with Perth, significantly fewer dog walkers walked in their local park in the three US study sites. San Diego dog walkers walked more often in their neighborhood/week compared with Perth dog walkers .Across all study sites, dog walkers walked with their dog 5–6 times/week for a total of 93–109 min/week and achieved ≥30mins of physical activity on more days/week and walked in their neighbourhood more often/week, compared with non-dog walkers . Among dog walkers, females were more likely than males to feel safer walking with their dog in their neighborhood . Compared with dog walkers in Perth, dog walkers from each of the US study sites felt safer in their neighborhood and perceived there was more neighborhood surveillance .In Portland, dog walkers perceived significantly more neighborhood problems and in Nashville dog walkers perceived a significantly higher level of neighborhood natural surveillance , compared with non-dog walkers  contains supplementary material, which is available to authorized users. Globally, physical inactivity is a significant health issue. Physical inactivity is the fourth leading risk factor for mortality behind high blood pressure, tobacco use and high blood glucose and a significant factor in rising obesity rates . Cost-efA large proportion of the community own dogs . In the One of the main mechanisms through which dogs facilitate increased physical activity is through the social support provided whilst dog walking , 8, 13. The aim of the study was: 1) to examine the relationship between dog walking and physical activity within and between four cities across the US and Australia; and 2) to investigate if dog walking is associated with greater perceived safety in those cities. We hypothesised that the relationship between dog walking and physical activity would be consistent across cities; that dog owners who are out and about in their local neighborhood walking with their dog have more positive perceptions of their local neighborhood; and that they perceive there to be higher levels of natural surveillance (‘eyes on the street’), fewer neighborhood problems and feel safer.n = 1113; 41.3 %) participating in the Pet Connections Study. Pet Connections is a cross-sectional study designed to examine the relationship between pet ownership and social capital, including between and within country  differences, and to identify pet-related factors that precipitate and maintain social connectedness in neighborhoods. The methodology is reported elsewhere [n = 690, Response Rate (RR) = 45.8 %; Nashville, US n = 664, RR = 44.1 %; Portland, US n = 634, RR = 42.1 %; Perth, Australia n = 704; RR = 60.2 %), yielding an overall response rate of 47.3 %. Study site samples were representative of the wider population in terms of sex, age group, neighborhood socio-economic status and pet ownership rates [The sample included all dog owners , ethnicity , country of birth , number of dependents <18 living at home, number of years lived in neighborhood and type of residence . Participants were also asked whether they owned a dog .Number of days per week participants reported ≥30 min of moderate-vigorous physical activity were recorded . ParticiGeneral neighbourhood perceptions of safety were based on existing scales. The ‘Feel Safe In Neighborhood’ scale was based on four items  (Cronbach’s α = 0.78) , 25. TheThe perceived potential ‘Neighborhood Problems’ scale measured graffiti and/or vandalism, crime, traffic, neighborhood maintenance  and social incivilities  –28. All Two items measured neighborhood perceptions specifically in relation to dog walking. Owners reported whether being with a dog helped them to feel safer when out walking or jogging and whether walking or jogging with their dog enabled them to get to know their neighborhood  .N = 1113). Chi-square tests were used to examine socio-demographic differences between dog walkers and non-dog walkers for each study site and overall. Linear regression was used to examine the relationship between dog walking status (independent variable) and days/week of ≥30mins of moderate-vigorous physical activity and frequency of walking in the neighbourhood/week (dependent variables). Logistic regression was used to examine the relationship between dog walking status (independent variable) and if participants walked to their local park in a usual week (dependent variable). Two models were run for each physical activity-related dependent variable; unadjusted and then adjusted for age group, sex, highest education level, ethnicity (US), country of birth , number of children in household, housing type, and time lived in neighborhood. Descriptive analyses (mean and standard error) were conducted for frequency and duration of dog walking/week. All analyses were conducted separately for each study site with non-dog walkers as the reference group. Between city comparisons were performed for dog walkers only (reference site = Perth), using the Bonferroni correction procedure for hypothesis testing involving multiple comparisons.Analyses were restricted to dog owners only  and perceptions of safety dependent variables . All models were adjusted for age group, sex, highest education level, ethnicity (US), country of birth , number of children in household, housing type, and time lived in neighborhood. All analyses were conducted separately for each study site with non-dog walkers as the reference group. Between city comparisons were examined for dog walkers only (reference site = Perth) using Bonferroni correction of p-values for multiple comparisons using the Bonferroni procedure.Finally, descriptive analyses were conducted by study site and overall to examine the percentage of dog walkers who reported that they ‘Feel safer walking with dog’ and ‘Got to know neighborhood through walking dog’. Non-dog walkers were excluded from analyses as our analyses were focused on dog walking only. Logistic regression was used to examine the relationship between gender  and the proportion of participants reporting they ‘Feel safer walking with dog’ and ‘Got to know neighborhood through walking dog’ (dependent variables). All models adjusted for age group, highest education level, ethnicity (US), country of birth , number of children in household, housing type, and time lived in neighborhood. All analyses were conducted separately for dog walkers from study site and overall. Between city comparisons were performed for a) all dog walkers (reference site = Perth) and b) female dog walkers only (reference site = Perth) correcting our Overall, 47 % of dog owners were male, 22 % were 40–49 years, 40 % had a bachelor degree or higher, 39 % had one or more children living at home and 56 % of dog owners were classified as ‘dog walkers’.p ≤ 0.05).Overall, there were no significant associations between age group, sex, education level, ethnicity, country of birth, number of children living in household, time lived in current neighbourhood or housing type by dog walking status Table . The majp ≤ 0.05). These findings were consistent across all four study sites. Similarly, across all four study sites a greater proportion of dog walkers compared with non-dog walkers walked in their local park . Compared with Perth, significantly fewer dog walkers walked in their local park in the three US study sites . Moreover, San Diego dog walkers walked more often in their neighborhood each week  4.0) compared with Perth dog walkers . Models remained significant after adjustment for socio-demographic factors  (Table p ≤ 0.001). Moreover, dog walkers in Nashville perceived there to be significantly fewer neighborhood problems compared with dog walkers in Perth (p ≤ 0.05).Among dog walkers, those in the US study sites, compared with those in Perth, felt safer in their neighborhood, perceived that there was more neighborhood surveillance and perceived that they would feel safer if there were neighborhood surveillance . When stratified by gender, female dog walkers in Portland compared with Perth were more likely to have got to know their neighborhood through walking their dog (p ≤ 0.05).Dog walkers were asked about feelings of safety whilst dog walking and whether they had got to know their neighborhood through dog walking Table . OverallA recent review of the evidence and meta-analysis called for international studies of the relationship between dog walking and physical activity . Our stuFurthermore, the frequency and duration of dog walking was consistent between and within the two countries. Regardless of country or city of residence, dog walkers reported walking their dog 5–6 times per week (for approximately 93–109 min/week). In comparison, a review of the evidence reported a weekly median frequency and duration of dog walking of 4 walks and 160 min, respectively . These vInternational studies provide an opportunity to determine how robust the evidence base is across countries. They also allow a deeper understanding of the cultural and social and physical environment influences on the relationship between dog walking and physical activity. Differences between dog walkers and non-dog walkers were observed but were not consistent across all four study sites. Nashville dog walkers perceived a significantly higher level of neighborhood natural surveillance and Portland dog walkers perceived significantly more neighborhood problems, compared with non-dog walkers. It is possible that as a result of dog walkers being out in the community walking their dog they notice more about the neighborhood they live in and are able to more accurately recall the features of their neighborhoods whether they be positive or negative attributes. A similar relationship has been observed in studies of the influence of neighborhood perceptions on physical activity behavior. For example, physical activity levels were higher in people who perceived their neighborhoods as unclean and untidy compared with those who perceived a high level of neighborhood cleanliness , 30. OurDog walking itself may provide an important source of ‘eyes on the street’. Dog owners who exercise their dog are out and about in their neighborhood on a near daily basis, as reflected in the mean frequency of dog walking per week  found in this study and a review . Dog walYet, we found no differences between dog walkers and non-dog walkers for how safe they felt in their neighborhood. However, when dog walkers were asked about how safe they felt when walking with their dog, significant gender differences emerged. Across all study sites a greater proportion of female than male dog walkers reported feeling safer when walking with their dog. This finding is consistent with a recent review of the correlates of dog walking which identified that perceived personal safety was positively associated with dog walking in females but not males . MoreoveThis study observed a number of between city differences in dog walkers’ neighborhood perceptions. In particular, compared with dog walkers in Perth, dog walkers from each of the US study sites felt safer in their neighborhood, perceived that there was more neighborhood surveillance and perceived that they would feel safer if there was neighborhood surveillance. We also observed that a significantly higher proportion of Perth dog walkers 80 %) compared with dog walkers from the US study sites (range 28–45 %) walked in their local park. It is possible that if Perth dog walkers spend more time walking in their local park and less time walking the streets in their neighborhood, they may perceive lower overall levels of neighborhood safety and natural surveillance. These between city differences in dog walkers neighborhood perceptions may in part also be explained by social and cultural differences in dog-keeping (and exercising) practices as well as differences in the local physical and policy environment surrounding walking dogs in public , 35. For0 % compaThis study was limited by its cross-sectional design and thus causal relationships between dog walking, physical activity and owner’s perceptions of safety cannot be inferred. However, it involved a large representative sample from four cities in the US and Australia and provided a unique opportunity to investigate between and within country differences in a relatively new area of enquiry. This study was also limited by its use of self-report measures and did not examine gender differences in the relationship between dog walking status and neighborhood-level perceptions of safety. Moreover, the internal consistency (as measure by Cronbach’s α) for the scales measuring ‘Natural Surveillance’ were questionable thus, is it possible that these items measure unique aspects of natural surveillance related to safety. Future studies should explore the relationship between different constructs of natural surveillance and the relationship with dog walking and owner’s perceived safety.This multi-site international study provides further support of the potential for dog walking to increase the proportion of the community who engage in daily physical activity. Innovative strategies  to increase physical activity levels are needed in developed countries where the burden of disease from insufficient adult physical activity is large . Individ


We present a first-principles derivation of the main results of the Kerr/CFT correspondence and its extensions using only tools from gravity and quantum field theory. Firstly, we review properties of extremal black holes with in particular the construction of an asymptotic Virasoro symmetry in the near-horizon limit. The entropy of extremal spinning or charged black holes is shown to match with a chiral half of Cardy’s formula. Secondly, we show how a thermal 2-dimensional conformal field theory (CFT) is relevant to reproduce the dynamics of near-superradiant probes around near-extremal black holes in the semi-classical limit. Thirdly, we review the hidden conformal symmetries of asymptotically-flat black holes away from extremality and present how the non-extremal entropy can be matched with Cardy’s formula. We follow an effective field theory approach and consider the Kerr–Newman black hole and its generalizations in various supergravity theories. The interpretation of these results by deformed dual conformal field theories is discussed and contrasted with properties of standard 2-dimensional CFTs. We conclude with a list of open problems. It is known since the work of Bekenstein , BardeenSince the advent of string theory, several black holes enjoying supersymmetry have been understood microscopically. In such cases, supersymmetry and its non-renormalization theorems allow to map the black hole states to dual states in a weakly-coupled description in terms of elementary strings and D-branes, which also provides a method to microscopically reproduce Hawking radiation slightly away from extremality  fiber. The self-dual orbifold is sometimes called the “very near-horizon limit” of the original extremal black hole  rotational Killing symmetry. The entropy in the very near-horizon geometry is then reproduced by a chiral half of Cardy’s formula, which is inherited from the 2D CFT.A special limit of J where J is the angular momentum  axial symmetry. The matching extends to the Kerr–Newman black hole but also to large classes of black holes in gravity coupled to matter, with anti-de Sitter asymptotic regions, with higher curvature corrections or in higher dimensions as extensively detailed later on. Moreover, a non-trivial matching can be done with a standard thermal 2D CFT correlation function slightly away from extremality for a limited number of gravitational observables which explore the near-horizon region  electromagnetic field can be promoted to be a Kaluza–Klein vector of a higher-dimensional spacetime. The U(1) electric charge is then uplifted as a U(1) axial angular momentum in the higher dimensional spacetime. Both angular momenta are then treated on an equal footing by the higher-dimensional version of the Kerr/CFT correspondence. This construction strengthen the strong parallel between the physics of static charged black holes and rotating black holes. Our point of view is that a proper understanding of the concepts behind the Kerr/CFT correspondence is facilitated by studying in parallel static charged black holes and rotating black holes. The relevance of the Kaluza–Klein construction also motivates to consider the Kerr/CFT correspondence in higher dimensions.Another notable extension of the thermal chiral Cardy relation exists for the Reissner–Nordström black hole  cycle . Experimental constraints on such scenarios can be set from bounds on the deviation of Newton’s law at small scales (Long and Price U(1) Kaluza–Klein circle. We then defineU(1) gauge field five-dimensional gravity coupled to matter fields.In more detail, the Reissner–Nordström/CFT arguments apply if our spacetime mentclass2pt{minimm et al. .4 TherefWe already motivated the study of the Kerr/CFT correspondence in the Einstein-matter system in 4 and higher dimensions. Embedding this correspondence in string theory has the potential to give microscopic realizations of these correspondences. Efforts in that direction include Nakayama , AzeyanaD supergravity on Instead we will focus in this review on the effective field theory approach. Since all relevant physics is well below the Planck scale, all arguments of the Kerr/CFT correspondence can be formulated using semi-classical gravity. We will limit our arguments to the actionmentclass2pt{minimOne additional motivation for studying this general class of theories comes from the AdS/CFT correspondence  symmetry of the black hole. Following semi-classical quantization rules, the operators, which define quantum gravity in the near-horizon region, form a representation of the Virasoro algebra. We will also review the arguments that the thermodynamical potential associated with the U(1) symmetry could be interpreted as a limiting temperature of the density matrix dual to the black hole. This leads to considering matching the black hole entropy with the thermal chiral Cardy formula. In Sect. After this introductory material, we will discuss the core of the Kerr/CFT correspondence starting from the Cardy matching of the entropy of extremal black holes in Sect. This review complements the lectures on the Kerr black hole presented in Bredberg et al.  by proviIn this section, we review some key properties of extremal black holes in the context of four-dimensional theories of gravity coupled to matter. We first contrast how to decouple from the asymptotic region the near-horizon region of static and rotating black holes. We then derive the thermodynamic properties of black holes at extremality. We then discuss near-horizon geometries close to extremality and emphasize their lack of local bulk dynamics.For simplicity, we will strictly concentrate our analysis on stationary black holes. Since we are concerned with the region close to the horizon, one could only require that the near-horizon region is stationary, while radiation would be allowed far enough from the horizon. Such a situation could be treated in the framework of isolated horizons  very close to the horizon  which we will use in the following. We refer the reader to the excellent lecture notes Townsend  for the We will define the near-horizon limit of static and rotating black holes at extremality and describe in detail their properties. We will also present some explicit examples of general interest. The extension of the near-horizon limit for near-extremal geometries will be described in Sect. SO(3) rotational symmetry. Since the horizon generator is null at the horizon, the coordinate t diverges there. The near-horizon limit is then defined asAs a warm-up, let us first review the near-horizon limit of static 4D extremal black holes. In that case, the generator of the horizon  symmetry generators. Furthermore, using the kinematical properties of the near-horizon limit, one can deduce the existence of either an iso symmetry which extends to the entire near-horizon geometry. Assuming the strong energy condition, the geometry It is important to note that one is free to redefine the near-horizon limit parameter i et al.  and the i et al.  for a descalar moduli. This is the attractor mechanism  coordinates are analogous to Poincaré coordinates on The geometry  is a warnditions  derived nditions . Note thGeodesic completeness of these geometries has not been shown in general, even though it is expected that they are geodesically complete. For the case of the near-horizon geometry of Kerr, geodesic completeness has been proven explicitly in Bardeen and Horowitz  after wo3D warped anti-de Sitter geometries; see Anninos et al. . Note that there is still a global time function for each near-horizon geometry. Constant global time The geometries enjoy a global timelike Killing vector  symmetries One can generalize the construction of near-horizon extremal geometries to higher dimensions. In five dimensions, there are two independent planes of rotation since the rotation group is a direct product ) \sim SO \times Smentclass2pt{minimLet us now present explicit examples of near-horizon geometries of interest. We will discuss the cases of the 4D extremal Kerr and Reissner–Nordström black holes as well as the 4D extremal Kerr–Newman and Kerr–Newman–AdS black holes. We will also present the 3D extremal BTZ black hole since it is quite universal. Other near-horizon geometries of interest can be found, e.g., in Clément and Gal’tsov , Dias etThe near-horizon geometry of extremal Kerr with angular momentum Horowitz  as well Horowitz , BredberHorowitz . The resHorowitz  without Q. We use the normalization of the gauge field such that the Lagrangian is proportional to The extremal Reissner–Nordström black hole is determined by only one parameter: the electric charge the form . We haveIt is useful to collect the different functions characterizing the near-horizon limit of the extremal Kerr–Newman black hole. The black hole has mass unctions  are recoack hole . The limM for e given here). The result isAs a last example of near-horizon geometry, let us discuss the extremal spinning charged black hole in AdS or Kerr–Newman–AdS black hole in short. The Lagrangian is given by n et al. , Chen etn et al.  , we, we\docuNow, as noted in Amsel et al. , there iThe condition for having a global timelike Killing vector was spelled out in . This coThe extremal Frolov–Thorne temperatures should also be directly encoded in the metric . More praring in  as71\doc between . The forSimilarly, one can work out the thermodynamics of five-dimensional rotating black holes. Since there are two independent angular momenta solution .When considering the uplift  of the gfinition  to definfined in .Balance equation: The entropy at extremality obeys the balance equation Zero law: The angular chemical potential Entropy function law: The entropy at extremality is the extremum of the entropy function the form  where \dLet us comment on these laws. The balance equation relates the variation of charges at extremality. It can be deduced from the first law of thermodynamics at leading order in the extremal limit, assuming analyticity and smoothness of thermodynamical quantities in the extremal limit. The balance equation can be generalized in two ways. First, instead of assuming extremal variations, one can take arbitrary parametric variations of the black hole, including non-extremal ones. It was shown in Johnstone et al. . On. OnBalak and e are constant. Since no dynamical processes outside equilibrium are allowed in the near-horizon geometries as we will discuss in Sect. The zero law is a consequence of both the zero law of thermodynamics for non-extremal black holes and the presence of The entropy function law is a statement about the dynamics of gravity among the class of near-horizon geometries and it has no obvious analogue away from extremality since it depends upon the existence of the near-horizon limit. It provides with the ground state entropy at extremality as a function of the other dynamical quantities in the system. The generalization to lower and higher dimensions is straightforward.The entropy of the extremal Kerr black hole is egrating  or usingegrating , we findThe entropy of the extremal Reissner–Nordström black hole is egrating , we obtaFor the electrically-charged Kerr–Newman black hole, the extremal entropy reads as finition  and re-e}Tϕ from  and the }Tϕ from . \documeent with .For the extremal Kerr–Newman–AdS black hole, the simplest way to obtain the thermodynamics at extremality is to compute –64). Us. Us64). initions . The magide with –71). Th. Th81\doide with  in the lAn important question about near-horizon geometries is the following: how much dynamics of gravity coupled to matter fields is left in a near-horizon limit such as ? We alreLet us first study infinitesimal perturbations of the near-horizon geometry . As a cototes to  will havows from  will corM in Boyer–Lindquist coordinates, we perform the near-horizon scaling limit \documentities as .17 SinceIn this section, we will review arguments pointing to the absence of local degrees of freedom in the near-horizon geometries  or 85),,85), folPropagating degrees of freedom have finite energy. If near-horizon geometries contain propagating modes, one expects that a highly-symmetric solution would exist which has a non-trivial spectrum of energy. Such solution would then approximate the late-time thermalized state after dissipation has occurred. However, in the case of 4D Einstein gravity, one can prove that the NHEK  is the unique (up to diffeomorphisms) regular stationary and axisymmetric solution asymptotic to the NHEK geometry with a smooth horizon , it is useful to describe some of their key properties. An important caveat is that, as discussed in the Introduction , there iA 2D CFT is defined as a local quantum field theory with local conformal invariance. Background material can be found, e.g., in Di Francesco et al. , Ginsparoperator product expansions between all operators. Since we will only be concerned with universal properties of CFTs here, such detailed data of individual CFTs will not be important for our considerations.A 2D CFT can be uniquely characterized by a list of (primary) operators We will describe in the next short sections some properties of CFTs that are most relevant to the Kerr/CFT correspondence and its extensions: the Cardy formula and its range of validity, some properties of the discrete light-cone quantization (DLCQ), another closely related class of conformally invariant theories namely the warped conformal field theories, and some classes of irrelevant deformations. The material in this section is far too preliminary to formulate concrete proposals for dual theories to black holes but it contains some ingredients which are expected to play a role in such a holographic correspondence.In any unitary and modular invariant CFT, the asymptotic growth of states in the microcanonical ensemble is determined only by the left and right central charge and the left and right eigenvalues in Cardy  and Blötin Cardy  using moin Cardy . TransfoThe origin of Cardy’s formula lies in an IR/UV connection implied by modular invariance. The spectrum of states at high energies is dictated by the spectrum of states at small energies. As we will discuss in Sect. c limit. The energy of the vacuum is We only consider CFTs which have identical left and right central charges With these assumptions, it was shown in Hartman et al.  assumingN identical copies of the target space N objects. The symmetric orbifold CFT has central charge c. The symmetric product orbifold with target space An important class of CFTs which obey the bounds –104) ar ar104) aIt was shown in Hartman et al.  that symAn older argument for the extension of Cardy’s formula goes as follows. Given a set of Virasoro generators N is very large, Cardy’s formula  Kač–Moody algebra  black holes is far from clear. A DLCQ is necessary in order to match the extremal limit on the gravitational side. The occurence of complex weights in near-horizon geometries without global timelike Killing vector such as NHEK also indicates that the putative dual theory will not be standard. The common properties of warped conformal field theories and near-horizon extremal geometries are the exact ra Guica  or the wra Guica  and it ira Guica , El-Showra Guica , Song anra Guica , Song anra Guica , Bena etra Guica  for propThe description of non-extremal black holes with an asymptotically flat or AdS region requires to consider 2D CFTs with irrelevant deformations in both left and right sectors. One issue with such a description is that the IR cutoff set by the temperature will in general be of the same order of magnitude as the UV cutoff set by the mass scale associated with irrelevant perturbations  gauge transformations U(1) gauge transformations. Therefore, the asymptotic symmetries form an algebra,well-defined charge and the charges are said to be integrable.After these general consideration, let us discuss the existence and the construction of a consistent set of boundary conditions that would define “the set of solutions in the near-horizon region of extremal black holes” and their associated asymptotic symmetry algebra. One has to propose boundary conditions from first principles. We will use the Lagrangian methods  asymptotic symmetry algebra for As an illustration, asymptotically anti-de Sitter spacetimes in spacetime dimensions Let us now motivate boundary conditions for the near-horizon geometry of extremal black holes. There are two boundaries at a et al.  and Harta et al.  to buildvated in . The subfined in .S is a codimension 2 surface of integration and Finding consistent boundary conditions that admit finite, conserved and integrable Virasoro charges and that are preserved by the action of the Virasoro generators is a non-trivial task. The details of these boundary conditions depend on the specific theory at hand because the expression for the conserved charges depend on the theory. For the action , the conand Wald  and haveand Wald . Such teand Wald  but are and Wald , Compèreand Wald . In the and Wald , it was and Wald  and Hartand Wald  that \doLet us first specialize to the case of the extremal Kerr black hole in Einstein gravity. The original approach followed in Guica et al.  see als was to pnditions , by \docenerator  (as poinenerator  and sublenerator ). It wasenerator  that theenerator  that theenerator , up to tenerator . Therefot, r surfaces admit singularities which complicates the definition of surface charges, as also discussed in Amsel et al. 136\docuenerator –125). I. I\documJ given in (U(1) symmetry along In three dimensions, a Virasoro algebra can also be found in the near-horizon limit of the BTZ black hole  circles form a torus invariant under Since two U(1) symmetries raises the question of whether or not the (AdS)–Reissner–Nördstrom black hole admits interesting boundary conditions where the U(1) gauge symmetry  plays the prominent role. One can also ask these questions for the general class of (AdS)–Kerr–Newman black holes.The occurrence of multiple choices of boundary conditions in the presence of multiple U(1) gauge field can be promoted to be a Kaluza–Klein direction of a higher-dimensional spacetime, or at least when such an effective description captures the physics. Denoting the additional direction by It was argued in Hartman et al.  and Lü enerators  would thThe boundary conditions discussed so far do not admit solutions with non-trivial charges under the nt}ζ0,±1 . In factFirst, we saw in Sect. enerator , one obtenerator  with \doolutions  and the Second, as far as extremal geometries are concerned, there is no need for a non-trivial Let us now assume in the context of the general theory  that a ct}Yμν in , see Comt}Yμν in  for discup to a central term, which commutes with each element of the algebra. Namely, one hasLet us define the Dirac bracket between two charges asent}Q as . From geent}Q as , the Dirfined in  and \docc and A. The general result has the formA is a trivial central extension that can be set to 1 by shifting the background value of the charge c is a number that is called the central charge of the Virasoro algebra. From the theorems , o, o\documtituting , one fintituting 148\documo ansatz –(125) arfined in .When higher-derivative corrections are considered, the central charge can still be computed exactly, using as crucial ingredients the i et al. 150\documfined in  in Sect.fined in  is obtaifined in  that thefined in  and Barnfined in  applied fined in , Barnichfined in , Compèrefined in  is not ifined in , this amfined in . Adding fined in  and modifined in . Therefofined in  to inclufined in  with thafined in .U(1) gauge fields and scalars, the central charge associated with the Virasoro generators along the direction Q and mass Q. First, the central charge is inversely proportional to the scale In five-dimensional Einstein gravity coupled to nsion of   as , \documegeometry . Then, tgeometry  is giveno ansatz  for the  formula , it thenUsing the simple embedding of the metric and the gauge fields in a higher-dimensional spacetime , as discentclass1pt{minimaect that   gauge field can be uplifted to a Kaluza–Klein direction, we can also formulate the Virasoro algebra (U(1) gauge field. Rather, one can uplift to eleven dimensions along a seven-sphere. One can then argue, as in Lü et al. (U(1) circle in the seven-sphere.Similarly, we can uplift the Kerr–Newman black hole to five-dimensions, using the uplift –2) and  and 2) a algebra  and assorelation  we obtaiü et al. , that thü et al. . Applyinü et al.  accountiü et al.  as , , 149), , 151), , 151), , 154), , 154), , 156) a a156) arIn Sect. nditions , 136), , \documenditions  form a rextremal BTZ black holes  symmetries are present, one can apply a modular transformation mixing the two U(1) and one obtains a different description for each choice of Finally, when two nerators  obeys thnerators . After pd limit  si siJ and 1implies –(166), sondition , and notNear-extremal black holes are characterized by an approximative near-horizon geometry, which controls the behavior of probe fields in the window . Upon tam and Probes will penetrate the near-horizon region close to the superradiant bound . When \dn as a natural coefficient defined near extremality. It will have a role to play in later Sects. The conclusion of this section is that the geometries  control The problem of scattering of a general spin field from a Kerr black hole was solved in a series of classic papers by Starobinskii , StarobiA is the real separation constant present in both equations for R(r). The underlying Killing–Yano tensor structure also leads to the separability of the Dirac equation for a probe fermionic field. For simplicity, we will not discuss further fermionic fields here and we refer the interested reader to the original reference , the scalar field can be extended at infinity into an incoming wave and an outgoing wave. The absorption probability For each frequency mentclasspt{minimaThe Sturm–Liouville problem  cannot bNear-horizon region: Far region: Overlap region: The overlap region is guaranteed to exist thanks to  electric field twisted along the fiber spanned by U(1) twist in the four-dimensional geometry, and one coming from the original U(1) gauge field. By a, b, c are related to In the near-horizon region, the radial equation reduces to a much simpler hypergeometric equation. One can in fact directly obtain the same equation from solving for a probe in a near-extremal near-horizon geometry of the type , which iring Eq. , where trequency  near extfined in .n  current algebra, whose zero eigenmode We will now assume that quantum gravity states form a representation of both a left and a right-moving Virasoro algebra with generators perature . We takefined in  associatressions , we findg et al. , we alsoU(1) current and a Virasoro algebra in both sectors,Therefore, under these assumptions, the symmetry group of the CFT dual to the near-extremal Kerr–Newman black hole is given by the product of a U(1) charges of the probe,The conformal weight =t∂t-r∂r  in the oy Witten , this beondition . We don’s of the Kerr black hole, the conformal weight  ar ar213) a rewrite  in the afined in  and \docU(1) symmetries are present) of part of the dynamics of near-extremal black holes. We expect that a general scattering theory around any near-extremal black-hole solution of . I. I219). Let us discuss general features of the massless Klein–Gordon equation in non-extremal black holes geometries. We restrict our discussions to four dimensions for simplicity. An essential property of all known black holes solutions is the existence of a conformal Killing–Stäckel tensor which implies that the massless Klein–Gordon equation is separable. A rank-2 conformal Killing–Stäckel tensor is a symmetric tensor r while u. The parameter A general class of asymptotically flat or AdS metrics which admits a conformal Killing–Stäckel tensor can be written in the following form (Chow and Compère SO(8) gauged supergravity in Chow and Compère  were also written down in  is given byIn the case of the Kerr–Newman black hole, the charged analogue of Eqs.  can be wIn the case of the Kerr–Newman–AdS black hole, the charged analogue of Eqs.  can be wr; see . T. T\documn r; see  in additIt has been suggested that all these poles have a role to play in the microscopic description of the AdS black hole  defined in . Eqs.  and ..\documenThe vector fields that generate the fined in , the ideced from . This caThe situation is similar to the BTZ black hole in 2+1 gravity that has a r, the relation between conformal coordinates r-dependent scaling,In the case of non-extremal black-hole geometries, one can similarly interpret the symmetry breaking using a CFT as follows  a a\documefined in  match wifined in . This isU(1) circle which defines the corresponding Virasoro algebra. For the Still assuming a CFT description of non-extremal black holes, one can then show that the temperatures M. This is a non-trivial feature of this Cardy matching which has no explanation so far.It turns out that in each case, the non-extremal black hole entropy matches Cardy’s formula with the temperatures  charges  with \doThe Kerr/CFT correspondence is a set of relations between the classical physics of spinning or charged black holes and representation of conformal symmetry (which depending on the context is either U(1) axial symmetry admits in its near-horizon geometry a Virasoro algebra with a non-trivial central charge. The black-hole entropy is reproduced by a chiral half of Cardy’s formula. This result is robust for any diffeomorphism-invariant theory and holds even including scalar and gauge field couplings and higher-derivative corrections. Moreover, if a U(1) gauge field can be geometrized into a Kaluza–Klein vector in a higher-dimensional spacetime, a Virasoro algebra can be defined along the Kaluza–Klein compact U(1) direction and all the analysis goes through in a similar fashion as for the axial U(1) symmetry. The deep similarity between the effects of rotation and electric charge can be understood from the fact that they are on a similar footing in the higher-dimensional geometry. When two U(1) symmetries are present, one can mix up the compact directions using a modular transformation and the construction of Virasoro algebras can still be made.We have reviewed that any extremal black hole containing a compact Independently of these constructions, the scattering probabilities of probes around the near-extremal Kerr–Newman black hole can be reproduced near the superradiant bound by manipulating near-chiral thermal two-point functions of a two-dimensional CFT. The result extends straightforwardly to other asymptotically-flat or AdS black holes in various gravity theories. Finally away from extremality, hidden A fair concluding remark would be that several new and intriguing properties of the Kerr–Newman black hole and their generalizations in string theory have been uncovered over the last years, but there is still a long road ahead to comprehend what these results are really telling us about the nature of quantum black holes.p-forms and non-abelian gauge fields. Are there new features?Near-horizon geometries of black-hole solutions of  have beeNon-extremal asymptotically flat black holes admit universal features such as the product of area formula and relationships among inner and outer horizon quantities. Investigate whether or not all black holes in string theory (with higher curvature corrections) admit these features. Either try to formulate a proof or find a counterexample. Extend the analysis to AdS black holes.A black hole in de Sitter spacetime can be extremal in the sense that its outer radius coincides with the cosmological horizon. The resulting geometry, called the rotating Narirai geometry, has many similarities with the near-horizon geometries of extremal black holes in flat spacetime or in AdS spacetime. The main difference is that the near-horizon geometry is a warped product of Formulate a general scattering theory around near-extremal black-hole solutions of . ClassifIn the analysis of near-extremal superradiant scattering for any spin, the modes that are below the Breitenlohner–Freedman bound were discarded. Such modes lead to non-conserved flux at the boundary, they lead to instabilities, and their interpretation by a CFT remains unclear. Clarify the match between these modes and CFT expectations for the Kerr–Newman black hole. Also, the match of near-extremal scattering waves with a CFT required to introduce a right-moving current algebra with the matching condition . ClarifyN super-Yang–Mills theory in an extremal thermal ensemble. Try to make this picture more precise.Understand how the extension of the Kerr/CFT correspondence to extremal AdS black holes fits within the AdS/CFT correspondence. As discussed in Lü et al. , the extBoundary conditions alternative to the Kerr/CFT boundary conditions have been proposed for higher dimensional extremal vacuum black holes  circle on the two torus spanned by the azimuthal direction and the Kaluza–Klein direction obtained by the uplift of the gauge field. This leads to a The hidden symmetry arguments for the non-extremal Kerr–Newman black hole rely on an choice of Provide with a procedure to compute the central charges Find the largest class of field theories and states such that Cardy’s formula applies.Find astrophysical observables in the near-horizon region of near-extremal Kerr which are constrained by Embed the extremal Kerr black hole in string theory and construct one exact holographic quantum field theory dual. Use this correspondence to precisely define the notion of a DLCQ of a warped deformation of a 2D CFT which is conjectured relevant to describe the microstates of the extremal Kerr black hole. In this model, compute the quantum corrections to the central charge d in Sen .We close this review with a list of open problems. We hope that the interested reader will tackle them with the aim of shedding more light on the Kerr/CFT correspondence. We ordered the list of problems such that they range from concrete problem sets to much more involved questions.


A computational investigation using a unique model and a solution algorithm was conducted, changing only the saturation pressure of one material artificially during nanopowder formation in thermal plasma fabrication, to highlight the effects of the saturation pressure difference between a metal and silicon. The model can not only express any profile of particle size–composition distribution for a metal–silicide nanopowder even with widely ranging sizes from sub-nanometers to a few hundred nanometers, but it can also simulate the entire growth process involving binary homogeneous nucleation, binary heterogeneous co-condensation, and coagulation among nanoparticles with different compositions. Greater differences in saturation pressures cause a greater time lag for co-condensation of two material vapors during the collective growth of the metal–silicide nanopowder. The greater time lag for co-condensation results in a wider range of composition of the mature nanopowder. Thermal plasmas have been used for effectual fabrication of nanopowders composed of nanometer-scale particles . NanopowThermal plasma fabrication of metal–silicide nanopowders involves the vaporization of raw materials and the subsequent conversion of the binary material vapors into numerous nanoparticles by virtue of the high enthalpy and high cooling rate of thermal plasma. However, the nanopowder growth is tremendously complicated because the nanopowder grows in a few tens of milliseconds through simultaneous and collective processes of binary homogeneous nucleation, binary heterogeneous co-condensation, and coagulation among nanoparticles with different compositions. Therefore, observing the growth process directly during experimentation is impossible. Only the characteristics of the final products have been evaluated ,10,11,12Computational studies based on theoretical modelling can reveal the growth mechanism and can enable prediction of the profile of the nanopowder to be synthesized. However, because of computational resource limitations, molecular dynamics (MD) calculation cannot comprehensively treat the entire growth process from nucleation until a nanopowder completes its growth . In placOnly a few aerosol-dynamics-based models have been developed for thermal plasma fabrication of nanopowders involving co-condensations of binary material vapors ,23,24. TThose computational results showed that the difference in saturation pressures between a metal and silicon was a crucial factor that determined the time lag of co-condensation and consequently affected the range of the silicon content in the synthesized nanopowder. Actually, an experimental study also reported that the saturation pressure difference affected the nanoparticle composition . The litEven though those studies indicated the importance of the saturation pressure difference between a metal and silicon, the effect remained unclear because the formation processes of nanopowders were also affected by material properties other than the saturation pressure. Data from the actual material properties were used for each material in those computations ,28,29. I4–105 K/s. Therefore, the present computation sets a constant cooling rate of 5.0 × 104 K/s to investigate the effect of saturation pressure difference under extremely simple conditions. The initial mole fraction of the material vapor to argon gas is set to be 0.5%. This can be regarded as a dilute condition in which the effect of the raw material on the flow field is negligible. This study particularly selects a titanium–silicon binary system because the saturation pressures of titanium and silicon are mutually close (Sp(Ti)/Sp(Si) = 10−1–100). The initial ratio of these materials is set fairly at Ti:Si = 1:1. These conditions suggest that the vapors of titanium and silicon co-condense almost simultaneously.In a typical condition of ITP discharge, the region downstream from the plasma offers a high cooling rate of 10S’p = ζ·Sp. Controlling only the value of ζ from 10−3 to 103, while using the other actual material properties [t of 2.0 μs, which provides sufficient resolution for the present condition.As a great benefit of computational investigation, the value of only one saturation pressure can be changed strategically, which cannot be done in experiments. Therefore, this study defines an artificial saturation pressure operties  with no Formation of binary metal-silicide nanopowder from the vapor phase can be computed using a unique model developed by the authors ,27,28. TW [monoNM), SN’M) is monomers of material M contained in a binary cluster and σM) = 50.0 atom %, which is identical to the initially given silicon fraction to the precursor. Particle diameters range widely from a few nanometers to 76 nm.3. This value means that the saturation pressure of silicon is artificially set to be 1,000 times larger than the actual saturation pressure. x(Si) = 50.0 atom %, the composition ranges widely from 25 atom % to 80 atom %.−3. These results imply that a wider range of composition is caused by a larger time lag of co-condensation that originally results from a larger difference of saturation pressures. Using our unique model and solution algorithm, which can simulate the entire growth process involving binary homogeneous nucleation, binary heterogeneous co-condensation, and coagulation among nanoparticles with different compositions, numerical experiments were carried out by changing only the saturation pressure of one material artificially to highlight the effect of the saturation pressure difference between a metal and silicon on the nanopowder formation in thermal plasma fabrication. A greater difference in saturation pressures causes a larger time lag of co-condensation of two material vapors during the collective growth of the metal–silicide nanopowder. The longer time lag of co-condensation results in a wider range of compositions for the mature nanopowder.