The threshold bias model: a mathematical model for the nomothetic approach of suicide

Background

Comparative and predictive analyses of suicide data from different countries are difficult to perform due to varying approaches and the lack of comparative parameters.

Methodology/Principal Findings

A simple model (the Threshold Bias Model) was tested for comparative and predictive analyses of suicide rates by age. The model comprises of a six parameter distribution that was applied to the USA suicide rates by age for the years 2001 and 2002. Posteriorly, linear extrapolations are performed of the parameter values previously obtained for these years in order to estimate the values corresponding to the year 2003. The calculated distributions agreed reasonably well with the aggregate data. The model was also used to determine the age above which suicide rates become statistically observable in USA, Brazil and Sri Lanka.

Conclusions/Significance

The Threshold Bias Model has considerable potential applications in demographic studies of suicide. Moreover, since the model can be used to predict the evolution of suicide rates based on information extracted from past data, it will be of great interest to suicidologists and other researchers in the field of mental health.     

Geomagnetic disturbances may be environmental risk factor for multiple sclerosis: an ecological study of 111 locations in 24 countries

Background

We noticed that a hypothesis based on the effect of geomagnetic disturbances (GMD) has the ability to explain special features of multiple sclerosis (MS). Areas around geomagnetic 60 degree latitude (GM60L) experience the greatest amount of GMD. The easiest way to evaluate our hypothesis was to test the association of MS prevalence (MSP) with angular distance to geomagnetic 60 degree latitude (AMAG60) and compare it with the known association of MS with geographical latitude (GL). We did the same with angular distance to geographic 60 degree latitude (AGRAPH60) as a control.

Methods

English written papers with MSP keywords, done in Europe (EUR), North America (NA) or Australasia (AUS) were retrieved from the PubMed. Geomagnetic coordinates were determined for each location and AMAG60 was calculated as absolute value of numerical difference between its geomagnetic latitude from GM60L. By an ecological study with using meta-regression analyses, the relationship of MSP with GL, AMAG60 and AGRAPH60 were evaluated separately. MSP data were weighted by square root of number of prevalent cases. Models were compared by their adjusted R square (AR²) and standard error of estimate (SEE).

Results

111 MSP data were entered in the study. In each continent, AMAG60 had the best correlation with MSP, the largest AR² (0.47, 0.42 and 0.84 for EUR, NA and AUS, respectively) and the least SEE. Merging both hemispheres data, AMAG60 explained 56% of MSP variations with the least SEE (R?=?0.75, AR²?=?0.56, SEE?=?57), while GL explained 17% (R?=?0.41, AR²?=?0.17, SEE?=?78.5) and AGRAPH60 explained 12% of that variations with the highest SEE (R?=?0.35, AR²?=?0.12, SEE?=?80.5).

Conclusions

Our results confirmed that AMAG60 is the best describer of MSP variations and has the strongest association with MSP distribution. They clarified that the well-known latitudinal gradient of MSP may be actually a gradient related to GM60L. Moreover, the location of GM60L can elucidate why MSP has parabolic and linear gradient in the north and south hemisphere, respectively. This preliminary evaluation supported that GMD can be the mysterious environmental risk factor for MS. We believe that this hypothesis deserves to be considered for further validation studies.     

Impact of vaccination and birth rate on the epidemiology of pertussis: a comparative study in 64 countries

Bordetella pertussis infection remains an important public health problem worldwide despite decades of routine vaccination. A key indicator of the impact of vaccination programmes is the inter-epidemic period, which is expected to increase with vaccine uptake if there is significant herd immunity. Based on empirical data from 64 countries across the five continents over the past 30–70 years, we document the observed relationship between the average inter-epidemic period, birth rate and vaccine coverage. We then use a mathematical model to explore the range of scenarios for duration of immunity and transmission resulting from repeat infections that are consistent with empirical evidence. Estimates of pertussis periodicity ranged between 2 and 4.6 years, with a strong association with susceptible recruitment rate, defined as birth rate × (1 − vaccine coverage). Periodicity increased by 1.27 years on average after the introduction of national vaccination programmes (95% CI: 1.13, 1.41 years), indicative of increased herd immunity. Mathematical models suggest that the observed patterns of pertussis periodicity are equally consistent with loss of immunity that is not as rapid as currently thought, or with negligible transmission generated by repeat infections. We conclude that both vaccine coverage and birth rate drive pertussis periodicity globally and that vaccination induces strong herd immunity effects. A better understanding of the role of repeat infections in pertussis transmission is critical to refine existing control strategies.     

武陵源风景名胜区旅游生态环境演变趋势与阈值分析

武陵源旅游业迅速发展的同时。景区生态环境质量逐年下降引起联合国教科文组织世界遗产委员会的关注：武陵源风景名胜区核心景区较突出的生态环境问题,主要表现在大气环境质量逐年降低;金鞭溪水质明显恶化;生物多样性受到威胁;景区城镇化、工商业比速度加快等。通过实地监测并全面分析武陵源风景名胜区环境演变趋势。发现住宿设施对环境的影响。比其他游乐设施更为明显,是武陵源风景名胜区旅游生态环境的关键影响因子。景区水质监测值的变化最大,表明水体是景区生态环境中最为脆弱的环境因子：随着游客的逐年增多。旅游生态环境呈现出加速恶化的趋势。通过建立基于环境脆弱因子的阈值模型,计算得出在不超出武陵源风景名胜区景区最为脆弱的环境因子——景区水质标准：总磷≤0．02(mg/L)前提下。景区上游接待区旅游生态阈值是春季宾馆可使用面积容限为29650m^2。夏季为76425m^2。秋季为13625m^2。冬季为8325m^2。不同类型的风景区。生态环境脆弱因子不同。宾馆建筑面积容限位也不同。沿着本文思路。可计算出其他类型风景区阈值。     

Medical journals,impact and social media: an ecological study of the Twittersphere

Background:

Twitter is an increasingly popular means of research dissemination. I sought to examine the relation between scientific merit and mainstream popularity of general medical journals.

Methods:

I extracted impact factors and citations for 2014 for all general medical journals listed in the Thomson Reuters InCites Journal Citation Reports. I collected Twitter statistics (number of followers, number following, number of tweets) between July 25 and 27, 2015 from the Twitter profiles of journals that had Twitter accounts. I calculated the ratio of observed to expected Twitter followers according to citations via the Kardashian Index. I created the (Fifty Shades of) Grey Scale to calculate the analogous ratio according to impact factor.

Results:

Only 28% (43/153) of journals had Twitter profiles. The scientific and social media impact of journals were correlated: in adjusted models, Twitter followers increased by 0.78% (95% confidence interval [CI] 0.38%–1.18%) for every 1% increase in impact factor and by 0.62% (95% CI 0.34%–0.90%) for every 1% increase in citations. Kardashian Index scores above the 99% CI were obsverved in 16% (7/43) of journals, including 6 of the 7 highest ranked journals by impact factor, whereas 58% (25/43) had scores below this interval. For the Grey Scale, 12% (5/43) of journals had scores above and 35% (15/43) had scores below the 99% CI.

Interpretation:

The size of a general medical journal’s Twitter following is strongly linked to its impact factor and citations, suggesting that higher quality research received more mainstream attention. Many journals have not capitalized on this dissemination method, although others have used it to their advantage.Social media has reached near ubiquity; medical research, researchers and journals are no exception to its pervasiveness.^1–7 One of the most popular social media platforms is Twitter, with an estimated 302 million monthly active users sending 500 million tweets per day.⁸ Twitter differs from other social media platforms in that posts are limited to 140 or fewer characters. With an emphasis on brevity, Twitter provides a unique opportunity for medical knowledge to be disseminated to the general public.^9,10 However, people with questionable medical research pedigrees are the stars of Twitter.With more than 65 million followers, Canadian @justinbieber is one of the most popular Twitter celebrities, narrowly edging out the most popular physician (@bengoldacre) by a margin of 64.5 million followers. Despite widespread distaste among non-Beliebers, it can be argued that The Biebs does display a modicum of musical talent (assuming multiplatinum albums and chart-topping singles¹¹ are a proxy for talent). Conversely, the woefully popular @KimKardashian, who trumps top scientists by more than 33 million followers, falls into the “famous for being famous” trope, alongside fellow Glitterati Paris Hilton and Nicole Richie. The notion that people with dubious levels of talent and questionable means of attaining celebrity can become immensely popular is worrisome. This notion has sparked debate within the scientific community. Do these self-perpetuated self-promoters exist in academia? Are any scientists “renowned for being renowned”?¹²There has been increasing use of alternative means of quantifying journals’ impact, notably using the Altmetric statistic, which conglomerates an article’s social media presence through blogs, news outlets, Facebook and Twitter. In response to the meteoric unmeritocratic rise of social media celebrities via Twitter, @neilhall_uk developed the playfully dubbed Kardashian Index (K-index) to address these issues in an academic context.¹² The K-index quantifies the discrepancy between mainstream popularity and scientific merit by examining one’s social media profile in relation to one’s citations in peer reviewed works.Continuing in this vein, I propose the (Fifty Shades of) Grey Scale for use with medical journals (in reference to the book, which has sold more than 125 million copies to date, despite being critically lambasted).¹³ Using a similar equation to the K-index, the Grey Scale calculates the ratio of the number of actual to expected followers using journal impact factor (rather than citations, as in the K-index) as the predictor variable. Journal impact factor and total citations are closely related. Impact factor is the ratio of total citations to the number of articles published by the journal, which adjusts for journals that have many more, or fewer, citable publications (e.g., weekly or bimonthly journals).¹⁴Unpacking the mechanisms of Twitter celebrity is difficult. Personal Twitter profiles often include humour, wit and other attributes not normally attributed to the reporting of a new paper, as per general medical journal Tweets. By eliminating the individuality of the Tweet, looking only at medical journals’ Twitter profiles rather than individual researchers’, a more direct examination of the relation between Twitter celebrity and scientific merit is possible. Although Tweets linking to papers have been associated with greater citations than non-Tweeted papers,¹⁵ whether or not this translates into greater Twitter followings for the authors and the journal in which the paper was published has yet to explored. The relation between the number of Twitter followers and impact factor scores has recently been investigated in urology journals, where nonsignificant correlations between the number of Twitter followers and the impact factor of the journal were found.¹⁶The current study seeks to examine whether scientific merit (captured by journal impact factor and citations) translates into Twitter celebrity (i.e., number of followers) in general medical journals.     

The photobioluminometer,an instrument for the study of ecological factors affecting photosynthesis

An instrument for measurement of bioluminescence and photosynthesis is described. It may be used to detect chemicals toxic to luminous bacteria or to measure photosynthetic oxygen production of algae in mixed culture with bacteria. The latter technique has been used to study the effect on algal photosynthesis of environmental factors such as light quality, temperature, and salinity, and to study the factors affecting chlorophyll synthesis. The technique is ideal for rapid detection of photosynthesis-inhibiting herbicides and other toxic substances in water.     

为什么自然保护区的生态移民要回迁:以广西十万大山保护区为例

正十万大山是我国南部近海的著名大山,是广西南部最高的山地。广西十万大山国家级自然保护区位于十万大山地区的核心位置,总面积达5.8万ha,尚保存有大面积的常绿阔叶林,特别是具有全球保护意义的热带季雨林,如沟谷雨林的狭叶坡垒(Hopea chinensis)林、海南风吹楠(Horsfieldia hainanensis)林等。这些季雨林(或标志种)在海拔900     

Towards the use of ecological heterogeneity to design reserve networks: a case study from Dadia National Park,Greece

In this paper, we present a novel approach for using ecological heterogeneity in reserve design. We measured five ecological heterogeneity indices (EHI) and we used a database of six biological groups (woody plants, orchids, orthopterans, aquatic and terrestrial herpetofauna and passerine birds) across 30 sites in a Mediterranean reserve (Greece). We found that all the five EHI were significantly related to the overall species richness and to the species richness of woody plants and birds. Two indices, measuring vertical vegetation complexity (1/D) and horizontal heterogeneity of landcover types (SIDI) in terms of Simpson’s index, predicted well overall species richness and had significantly higher values inside the complementary reserve networks designed after five of the six biological groups. We compared five methods of forming reserve networks. The method of ecological heterogeneity (selecting those sites with the greatest 1/D and then SIDI) was less efficient (non-significantly) than the species-based methods (scoring and complementary networks) but significantly more efficient than the random method (randomly selected network). We also found that the method of complementary ecological heterogeneity (selecting those sites where each EHI had its maximum value) was not that efficient, as it did not differ significantly from the random method. These results underline the potential of the ecological heterogeneity method as an alternative tool in reserve design.     

Relation between biochemical severity and intelligence in early treated congenital hypothyroidism: a threshold effect.

OBJECTIVES--To assess whether early treatment of congenital hypothyroidism fully prevents intellectual impairment. DESIGN--A national register of children with congenital hypothyroidism who were compared with unaffected children from the same school classes and matched for age, sex, social class, and first language. SETTING--First three years (1982-4) of a neonatal screening programme in England, Wales, and Northern Ireland. SUBJECTS--361 children with congenital hypothyroidism given early treatment and 315 control children. MAIN OUTCOME MEASURES--Intelligence quotient (IQ) measured at school entry at 5 years of age with the Wechsler preschool and primary scale of intelligence. RESULTS--There was a discontinuous relation between IQ and plasma thyroxine concentration at diagnosis, with a threshold at 42.8 nmol/l (95% confidence interval 35.2 to 47.1 nmol/l). Hypothyroid children with thyroxine values below 42.8 nmol/l had a mean IQ 10.3 points (6.9 to 13.7 points) lower than those with higher values and than controls. None of the measures of quality of treatment (age at start of treatment (range 1-173 days), average thyroxine dose (12-76 micrograms in the first year), average thyroxine concentration during treatment (79-234 nmol/l in the first year), and thyroxine concentration less than 103 nmol/l at least once during the first year) influenced IQ at age 5. CONCLUSIONS--Despite early treatment in congenital hypothyroidism the disease severity has a threshold effect on brain development, probably determined prenatally. The 55% of infants with more severe disease continue to show clinically significant intellectual impairment; infants with milder disease show no such impairment. The findings predict that 10% of early treated infants with severe hypothyroidism, compared with around 40% of those who presented with symptoms in the period before screening began, are likely to require special education.     

生态保护修复对碳酸盐岩溶蚀速率的影响——以重庆市为例

岩溶区矿山生态修复、石漠化治理等生态保护修复工程,不仅改善了区内生态环境,而且有利于促进土壤、岩溶固碳增汇,对实现"双碳"目标具有重要意义。以重庆主城北碚矿山生态修复、渝东北巫山石漠化治理区等为例,通过野外标准溶蚀试片实验法和土壤取样测试分析法,研究不同生态保护修复措施下土壤碳库、碳酸盐岩溶蚀速率等变化特征,探讨不同生态修复方式对碳酸盐岩溶蚀速率的影响。结果表明:灰岩矿山修复区、石漠化治理区,土壤无机碳(SIC)含量较高,约为土壤有机碳(SOC)的4.5倍,且对碳酸盐岩溶蚀速率有一定的抑制作用;修复时间越长,土壤有机碳(SOC)含量越高,但SOC含量与碳酸盐岩溶蚀速率的相关性不显著;从夏季(监测期7、8月遭受极端高温干旱)至秋、冬、春季,土下及地表试片溶蚀速率明显增大;不同生态保护修复方式或植被恢复类型,碳酸盐岩溶蚀速率明显不同,北碚矿山修复区月桂林＞草灌从(橘树)＞草灌从(桃树)＞花椒树＞李子树,巫山生态修复区石漠化治理林地＞封山育林林地＞石漠化治理果园。     

An ecological study of small rodents in the thicket-clump savanna of Lengwe National Park, Malawi

A community of small rodents was studied in thicket-clump and grassland savanna of Lengwe National Park, Malawi, from September 1984 to June 1985. Nine species were recorded on a 1·1 ha grid and five assessment lines, using a capture-mark-release technique. The three commonest species (and their percentage proportions) were Mastomys natalensis (47%), Acomys spinosissimus (24%) and Saccostomus campestris (11%). Population numbers on the grid fluctuated from–30 individuals/ha, and the numbers on the assessment lines fluctuated from–57 individuals. There were two peaks of population numbers during the year: the first was in the early wet season (when individuals emigrated from dry season refugia and there was limited reproduction) and the second was in the mid dry season (when young born at the end of the wet season entered the trappable population). The population was comprised mainly of subadults in the late dry season, adults and some young in the wet season, and young and subadults in the early and mid dry seasons. Population survival rates were low with only 30–50% of individuals surviving to the following month. The magnitude of population fluctuations are related to the strong seasonality of climate, flooding and grass characteristics; in this respect, the community of small mammals in Lengwe National Park shows similarities to those of the Kafue Valley in Zambia and the Chobe Valley in Botswana.     

新疆生态足迹与环境压力的时空分异

提高生态现代化总体水平是改善区域生态环境承载力的核心和关键。利用生态环境质量指数和生态现代化指数(EM I)对我国西部生态环境脆弱区的新疆维吾尔自治区生态足迹和环境压力的变动态势进行了系统分析。结果表明:2004年新疆生态现代化指数在全国排名为27位,仍然为我国生态现代化水平落后的地区之一。1980—2005年,新疆综合现代化水平远低于高收入国家、世界平均水平和中等发达国家。1998年新疆人均生态足迹由25957hm2增加到2007年的40551hm2,人均生态承载力由3.1270hm2减少到2.8266 hm2。区域环境水平呈下降趋势。资源转化率、生态保护指数呈明显上升态势。环境治理指数呈剧烈变动,1996-2003年呈"N"型变动态势,区域生态脆弱性没有明显逆转。     

An ecological study of small rodents in the woodland savanna of Liwonde National Park, Malawi

A community of small rodents was studied in the woodland savanna of Liwonde National Park, Malawi from September 1984 to June 1985. Seven species were recorded on two 11 ha grids, using a capture-mark-release technique. Three species ( Aelhomys chrysophilus, Acomys spinosissimus and Tatera leucogasler ) comprised 78% of all trapped individuals. Average population numbers fluctuated from 3 to 17 individuals/ha. The grid with the densest vegetation supported the greatest number of individuals. Highest population numbers occurred in the mid-dry season (when the grids appeared to act as refugia) and in the early wet season (due to recruitment of young animals). Areas which had been burned during the dry season did not support as many individuals as unburnt areas. Population survival rates were low, with only about 50% of individuals surviving to the following month. The number of individuals/ha in Liwonde NP was lower than in similar habitats in other parts of eastern Africa, probably because of the shorter rainfall season and the consequent strong seasonal fluctuations in food resources, reduced opportunity for reproduction, and overall low productivity of the ecosystem.     

Prevalence of asthma symptoms in schoolchildren, and climate in west European countries: an ecologic study

The aim of the present study was to estimate the associations between the prevalence of asthma symptoms in schoolchildren and meteorological variables in west European countries that participated in the International Study of Asthma and Allergies in Children (ISAAC), Phase III 1997–2003. An ecologic study was carried out. The prevalence of asthma was obtained from this study from 48 centers in 14 countries, and meteorological variables from those stations closest to ISAAC centers, together with other socioeconomic and health care variables. Multilevel mixed-effects linear regression models were used. For schoolchildren aged 6–7 years, the prevalence rate of asthma decreased with an increase in mean annual sunshine hours, showed a positive association with rainy weather, and warm temperature, and a negative one with relative humidity and physician density (PD). Current wheeze prevalence was stronger in autumn/winter seasons and decreased with increasing PD. Severe current wheeze decreased with PD. For schoolchildren aged 13–14 years, the prevalence rates of asthma and current wheeze increased with rainy weather, and these rates decreased with increased PD. Current wheeze, as measured by a video questionnaire, was inversely associated with sunny weather, and nurse density. Severe current wheeze prevalence was stronger during autumn/winter seasons, decreased with PD, and indoor chlorinated public swimming pool density, and increased with rainy weather. Meteorological factors, including sunny and rainy weather, and PD may have some effect on the prevalence rates of asthma symptoms in children from west European countries.     

Hospital delivery and neonatal mortality in 37 countries in sub-Saharan Africa and South Asia: An ecological study

BackgroundWidespread increases in facility delivery have not substantially reduced neonatal mortality in sub-Saharan Africa and South Asia over the past 2 decades. This may be due to poor quality care available in widely used primary care clinics. In this study, we examine the association between hospital delivery and neonatal mortality.Methods and findingsWe used an ecological study design to assess cross-sectional associations between the share of hospital delivery and neonatal mortality across country regions. Data were from the Demographic and Health Surveys from 2009 to 2018, covering 682,239 births across all regions. We assess the association between the share of facility births in a region that occurred in hospitals (versus lower-level clinics) and early (0 to 7 days) neonatal mortality per 1,000 births, controlling for potential confounders including the share of facility births, small at birth, maternal age, maternal education, urbanicity, antenatal care visits, income, region, and survey year. We examined changes in this association in different contexts of country income, global region, and urbanicity using interaction models.Across the 1,143 regions from 37 countries in sub-Saharan Africa and South Asia, 42%, 29%, and 28% of births took place in a hospital, clinic, and at home, respectively. A 10-percentage point higher share of facility deliveries occurring in hospitals was associated with 1.2 per 1,000 fewer deaths (p-value < 0.01; 95% CI: 0.82 to 1.60), relative to mean mortality of 22. Associations were strongest in South Asian countries, middle-income countries, and urban regions. The study’s limitations include the inability to control for all confounding factors given the ecological and cross-sectional design and potential misclassification of facility levels in our data.ConclusionsRegions with more hospital deliveries than clinic deliveries have reduced neonatal mortality. Increasing delivery in hospitals while improving quality across the health system may help to reduce high neonatal mortality.

In an ecological study, Anna D Gage and colleagues examine the association between hospital delivery and neonatal mortality in 37 countries in sub-Saharan Africa and South Asia.     

Herb-rich spruce forests in W Nordland, N Norway: an ecological and methodological study

The vegetation of herb-rich spruce forests in three localities in Brønnøy municipality, W Nordland, N Norway, has been analysed using 120 sample plots, each 25 m², distributed by a restricted random method. In connection with every sample plot a set of ecological variables have been measured. The most important gradients for the differentiation of the vegetation were identified by DCA ordination and statistical analysis of the vegetational and the ecological data sets. The gradients were: (1) the nutrient gradient, (2) the soil moisture gradient and (3) the microclimate gradient. The importance of choice of ordination technique (DCA or LNMDS) relative to the importance of the choice of some parameters in DCA and LNMDS has been evaluated. Indicating from this evaluation were (1) the choice of weighting function prior to DCA ordination can be as important as the choice of ordination technique when the data set is small; (2) choice of dimensionality in LNMDS is normally not as decisive for the ordination result as the choice of ordination technique and (3) when the data set is larger, the choice of scale range is less decisive for the ordination result than the choice of dimensionality in LNMDS.