Level Of Stratification Research Articles

Serum neuron-specific enolase levels are upregulated in patients with acute lymphoblastic leukemia and are predictive of prognosis.

We explored the relationship between neuron-specific enolase (NSE) levels and the clinical features of acute lymphoblastic leukemia (ALL). Seventy ALL patients and forty-two healthy controls were enrolled in this study, and their serum NSE levels were measured using an electrochemiluminescence assay. The serum NSE concentration was higher in ALL patients than in healthy controls. In ALL patients, the mean serum NSE level declined after complete remission (CR) but increased with relapse. In addition, the mean serum NSE level was lower in the CR group than in the non-CR group. High NSE levels were associated with poorer progression-free and overall survival than low NSE levels. Serum NSE levels closely correlated with several clinical features, including the immunophenotype, risk stratification and serum lactate dehydrogenase levels. Multivariate analysis revealed that high NSE expression was an independent prognostic factor in adult ALL patients. NSE mRNA levels were also higher in ALL cell lines and bone marrow mononuclear cells from ALL patients than in control cells. These results suggested that NSE could be a clinical prognostic factor and a potential therapeutic target in ALL.

Education as a Resource of Social Innovation

Focusing on the Italian context, this research aims to analyze the relationship between investment in education and economic development through a critical exam of the human capital theory. This paradigm is compared with the social investment paradigm, particularly the Esping-Andersen’s thesis, which seems more useful to unfold the link between social stratification and education level as a resource of social innovation. From this standpoint, our hypothesis is that educational policies have positive effects on the economic system if they are oriented to reduce socio-economic inequalities increasing the rate of social inclusion, which can promote a wider social innovation.

Analysis of the genetic diversity and structure across a wide range of germplasm reveals prominent gene flow in apple at the European level.

BackgroundThe amount and structure of genetic diversity in dessert apple germplasm conserved at a European level is mostly unknown, since all diversity studies conducted in Europe until now have been performed on regional or national collections. Here, we applied a common set of 16 SSR markers to genotype more than 2,400 accessions across 14 collections representing three broad European geographic regions (North + East, West and South) with the aim to analyze the extent, distribution and structure of variation in the apple genetic resources in Europe.ResultsA Bayesian model-based clustering approach showed that diversity was organized in three groups, although these were only moderately differentiated (FST = 0.031). A nested Bayesian clustering approach allowed identification of subgroups which revealed internal patterns of substructure within the groups, allowing a finer delineation of the variation into eight subgroups (FST = 0.044). The first level of stratification revealed an asymmetric division of the germplasm among the three groups, and a clear association was found with the geographical regions of origin of the cultivars. The substructure revealed clear partitioning of genetic groups among countries, but also interesting associations between subgroups and breeding purposes of recent cultivars or particular usage such as cider production. Additional parentage analyses allowed us to identify both putative parents of more than 40 old and/or local cultivars giving interesting insights in the pedigree of some emblematic cultivars.ConclusionsThe variation found at group and subgroup levels may reflect a combination of historical processes of migration/selection and adaptive factors to diverse agricultural environments that, together with genetic drift, have resulted in extensive genetic variation but limited population structure. The European dessert apple germplasm represents an important source of genetic diversity with a strong historical and patrimonial value. The present work thus constitutes a decisive step in the field of conservation genetics. Moreover, the obtained data can be used for defining a European apple core collection useful for further identification of genomic regions associated with commercially important horticultural traits in apple through genome-wide association studies.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0818-0) contains supplementary material, which is available to authorized users.

Protocol and methodology of Study epidemiological mental health in Andalusia: PISMA-ep.

This is the general methods describing paper of a cross-sectional study that aims to detect the prevalence of major mental disorders in Andalusia (Southern Spain), and their correlates or potential risk factors, using a large representative sample of community-dwelling adults. This is a cross-sectional study. We undertook a multistage sampling using different standard stratification levels and aimed to interview 4,518 randomly selected participants living in all 8 provinces of the Andalusian region utilizing a door-knocking approach. The Spanish version of the MINI International Neuropsychiatric Interview, a valid screening instrument ascertaining ICD-10/DSM-IV compatible mental disorder diagnoses was used as our main diagnostic tool. A large battery of other instruments was used to explore global functionality, medical comorbidity, personality traits, cognitive function and exposure to psychosocial potential risk factors. A saliva sample for DNA extraction was also obtained for a sub-genetic study. The interviews were administered and completed by fully trained interviewers, despite most tools used are compatible with lay interviewer use. A total of 3,892 (70.8%) of 5,496 initially attempted households had to be substituted for equivalent ones due to either no response (37.7%) or not fulfilling the required participant quota (33%). Thence, out of 5,496 eligible participants finally approached, 4,507 (83.7%) agreed to take part in the study, completed the interview and were finally included in the study (n=4,507) and 4,286 (78%) participants also agreed and consented to provide a saliva sample for DNA study. On the other hand, 989 (16.3%) approached potential participants refused to take part in the study. This is the largest mental health epidemiological study developed in the region of Spain (Andalusia). The response rates and representativeness of the sample obtained are fairly high. The method is particularly comprehensive for this sort of studies and includes both, personality and cognitive assessments, as well as a large array of bio-psycho-social risk measures.

Spatio-temporal disruption of thermocline by successive laminar vortex pairs in a single tank thermal energy storage

The stratification efficiency of single tank thermal energy storage is affected by the internal mixing processes, especially in the thermocline region due to disturbances of different kinds. To study the mixing dynamics at the interface, we have conducted detailed numerical and supporting experimental studies for different Atwood numbers (stratification levels). Numerical experiments were conducted with two successive vortex pairs with three different time-lags (short, medium and long). For the short time-lag case, the preliminary vortex pair merges with the ensuing vortex pair. The merged single vortex pair peels back the thermocline layer causing mixing of the hot and cold fluids. The thermocline thickness increases as a result of the entrainment of the cold fluid into the hot fluid. The peeling process continues until buoyant forces leads to plume like structures that penetrate into the lighter fluid. For the medium and large time-lag cases, such merging of vortices was not observed. The vortex pair interacts separately with the thermocline region. The plume structure created by the first vortex pair interacts with the ensuing vortex pair. The altered interface (thermocline) thickness strongly depends on the nature of the vortex–thermocline interaction mechanisms. The thermocline effectiveness decreases consequent to such interactions and have been quantified in details in the current work.

Cost-Effectiveness of HIV Preexposure Prophylaxis for People Who Inject Drugs in the United States.

The total population health benefits and costs of HIV preexposure prophylaxis (PrEP) for people who inject drugs (PWID) in the United States are unclear. To evaluate the cost-effectiveness and optimal delivery conditions of PrEP for PWID. Empirically calibrated dynamic compartmental model. Published literature and expert opinion. Adult U.S. PWID. 20 years and lifetime. PrEP alone, PrEP with frequent screening (PrEP+screen), and PrEP+screen with enhanced provision of antiretroviral therapy (ART) for individuals who become infected (PrEP+screen+ART). All scenarios are considered at 25% coverage. Infections averted, deaths averted, change in HIV prevalence, discounted costs (in 2015 U.S. dollars), discounted quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratios. PrEP+screen+ART dominates other strategies, averting 26700 infections and reducing HIV prevalence among PWID by 14% compared with the status quo. Achieving these benefits costs $253000 per QALY gained. At current drug prices, total expenditures for PrEP+screen+ART could be as high as $44 billion over 20 years. Cost-effectiveness of the intervention is linear in the annual cost of PrEP and is dependent on PrEP drug adherence, individual transmission risks, and community HIV prevalence. Data on risk stratification and achievable PrEP efficacy levels for U.S. PWID are limited. PrEP with frequent screening and prompt treatment for those who become infected can reduce HIV burden among PWID and provide health benefits for the entire U.S. population, but, at current drug prices, it remains an expensive intervention both in absolute terms and in cost per QALY gained. National Institute on Drug Abuse.

Risk stratification by endocrinologists of patients with type 2 diabetes in a Danish specialised outpatient clinic: a cross-sectional study.

BackgroundTo target optimised medical care the Danish guidelines for diabetes recommend stratification of patients with type 2 diabetes (T2D) into three levels according to risk and complexity of treatment. The aim was to describe the T2D population in an outpatient clinic, measure the compliance of the endocrinologists’ to perform risk stratification, and investigate the level of concordance between stratification performed by the endocrinologists and objective assessments.MethodsA cross-sectional study with data collected from medical records and laboratory databases. The Danish risk stratification model contained the following criteria: HbA1c, blood pressure, metabolic complications, microvascular and macrovascular complications. Stratification levels encompassed: level 1 (uncomplicated), level 2 (intermediate risk) and level 3 (high risk). Objective assessments were conducted independently by two health professionals, and compared with the endocrinologists’ assessments. In order to test the degree of concordance, we conducted Cohen's kappa, McNemar’s test for marginal homogeneity, and Bowker’s test for symmetry.ResultsOf 245 newly referred patients, 209 (85 %) were stratified by the endocrinologists to level 1 (16 %), level 2 (55 %) and level 3 (29 %). By objective assessments, 4 % were stratified to level 1, 51 % to level 2 and 45 % to level 3. Of 419 long-term follow-up patients, 380 (91 %) were stratified by the endocrinologists to level 1 (5 %), level 2 (57 %), level 3 (38 %). By objective assessments, 3 % were stratified to level 1, 58 % to level 2 and 39 % to level 3. The concordance rate between endocrinologists’ and objective assessments was 63 % among newly referred (kappa 0.39; fair agreement) and 67 % for long-term follow-up (kappa 0.45; moderate agreement). Among newly referred patients, the endocrinologists stratified less patients at level 3 compared to objective assessments (p < 0.0001). There were no significant differences in marginal distribution within long-term follow-up patients.ConclusionType 2 diabetes patients, newly referred to or allocated for long-term follow-up in the out-patient clinic, were mainly intermediate and high-risk, complicated patients (96 % and 95 %, respectively). Compliance of stratification by endocrinologists was high. The concordance between endocrinologists’ and objective assessments was not strong. Our data suggest that clinician-support for stratification level categorisation might be needed.

E25 stratified torch ignition engine performance, CO2 emission and combustion analysis

Vehicular emissions significantly increase atmospheric air pollution and the greenhouse effect. This fact associated with the fast growth of the global motor vehicle fleet demands technological solutions from the scientific community in order to achieve a decrease in fuel consumption and CO2 emission, especially of fossil fuels to comply with future legislation. To meet this goal, a prototype stratified torch ignition engine was designed from a commercial baseline engine. In this system, the combustion starts in a pre-combustion chamber where the pressure increase pushes the combustion jet flames through a calibrated nozzle to be precisely targeted into the main chamber. These combustion jet flames are endowed with high thermal and kinetic energy being able to promote a stable lean combustion process. The high kinetic and thermal energy of the combustion jet flame results from the load stratification. This is carried out through direct fuel injection in the pre-combustion chamber by means of a prototype gasoline direct injector (GDI) developed for low fuel flow rate. During the compression stroke, lean mixture coming from the main chamber is forced into the pre-combustion chamber and, a few degrees before the spark timing, fuel is injected into the pre-combustion chamber aiming at forming a slightly rich mixture cloud around the spark plug which is suitable for the ignition and kernel development. The performance of the torch ignition engine running with E25 is presented for different mixture stratification levels, engine speed and load. The performance data such as combustion phasing, specific fuel consumption, thermal efficiency and the specific emissions of CO2 are carefully analyzed and discussed in this paper. The results obtained in this work show a significant increase in the torch ignition engine’s performance in comparison with the baseline engine which was used as a workhorse for the prototype engine construction.

Skills and Inequality: Partisan Politics and the Political Economy of Education Reforms in Western Welfare StatesBusemeyer, MariusCambridge, Cambridge University Press (2015), 309 p., ISBN 978‐1‐107‐06293‐1

Skills and Inequality: Partisan Politics and the Political Economy of Education Reforms in Western Welfare StatesBusemeyer, MariusCambridge, Cambridge University Press (2015), 309 p., ISBN 978‐1‐107‐06293‐1

Incidence of register-based diabetes 10 years after a stepwise diabetes screening programme: the ADDITION-Denmark study.

Screening programmes for type 2 diabetes inevitably find more people at high risk of developing diabetes than people with undiagnosed prevalent diabetes. We describe the incidence of diabetes for risk groups according to advancement in a screening process. In 2001-2006, a diabetes screening programme based on the Danish diabetes risk score and measures of HbA1c and glucose was carried out in Danish general practices. The present study includes 13,249 individuals with low diabetes risk scores and 22,726 with high diabetes risk scores but no diabetes according to WHO 1999 criteria. Seven incremental levels of diabetes risk were defined and followed for incident diabetes recorded in the Danish National Diabetes Register until December 2012. For each group, cumulative diabetes incidence was calculated. Incidence rates and rate ratios were estimated by Poisson regression analyses. After 10 years of follow-up 1,164 new diabetes cases were registered. Incidence rates were 1.0, 4.2, 14.5, 28.8 and 52.6 per 1,000 person-years in individuals at low risk and in those with normal glucose tolerance, impaired fasting glucose, impaired glucose tolerance and one diabetic glucose value, respectively. For each step in the screening algorithm, the risk of developing diabetes was higher than in the previous step. The risk of developing clinical diabetes in people who screen negative for diabetes depends on the level of risk stratification at screening, even at lower risk levels. This risk increases markedly in the presence of impaired glucose regulation. These results can inform policy recommendations concerning prevention strategies following screening.

Cross-sectional investigation of nursing managers′ expectations towards nurses′ energy level stratification and promotion requirements level three class A hospitals in Beijing

Objective To understand nursing managers′ expectations towards nurses′ energy level stratification so as to provide the basis for the establishment of a scientific nurses′ level stratification. Methods Questionnaires were used to investigate 148 nursing managers who were randomly selected from level three class A 10 hospitals in Beijing. Results A total of 55 nursing managers (37.2%) thought that nurses′ stratification could be divided into four levels, 29 (19.6%) for five levels and 37 (25.0%) for six levels among 148 nursing managers. A total of 148 nursing managers believed that nurses′ education background, professional title, working experiences, ability of nursing clinical, teaching ability, scientific research ability and so on should be considered as indicators of nurses′ level stratification and expressed their expectations towards nurses′ energy level stratification. Conclusions It is appropriate to divide nurses′ stratification into four to six levels. Many indicators should be fully considered in the specific stratification to reflect the professional value of all nurses in maximum extent. Expectations of the managers towards nurses′ energy level stratification provide a good foundation for building a scientific and objective nurses′ level stratification and a sustained development career path for nurses. Key words: Nurse administrators; Nurses; Energy level stratification; Promotion; Expectation

Numerical Analysis of Thermal Stratification in Large Horizontal Thermal Energy Storage Tanks

This paper presents the results of a numerical study on the thermal performance of large horizontal thermal energy storage tanks. The numerical model was validated using measurements obtained from Drake Landing Solar Community (DLSC), which is located in Alberta, Canada. A total of seven different baffle configurations were assessed for a range of operating conditions. Characterization of the tank performance was done by monitoring the tank outlet temperature and computing the Huhn efficiency, which is a characterization index based on the second law of thermodynamics. Results show that the current tanks at DLSC experience excessive mixing due to fluid entrainment from the inlet jet. A newly introduced design that confines the inlet jet mixing shows the potential to enhance the level of stratification during charging or discharging at a constant temperature. In addition, most designs tested have a relatively high level of stratification during charging, discharging, and simultaneous charging and discharging, but fail to sustain the level of stratification when a positive buoyant jet is introduced.

Body Mass Index and the Risk of Cardiovascular and All-Cause Mortality Among Patients With Hypertension: A Population-Based Prospective Cohort Study Among Adults in Beijing, China.

BackgroundStudies on the association between body mass index (BMI) and death risk among patients with hypertension are limited, and the results are inconsistent. We investigated the association between BMI and cardiovascular disease (CVD) and all-cause mortality among hypertensive patients in a population of Beijing, China.MethodsWe conducted a prospective cohort study of 2535 patients with hypertension aged 40 to 91 years from Beijing, China. Participants with a history of CVD at baseline were excluded from analysis. Cox proportional hazards regression models were used to estimate the association of different levels of BMI stratification with CVD and all-cause mortality.ResultsDuring a mean follow-up of 8.1 years, 486 deaths were identified, including 233 cases of CVD death. The multivariable-adjusted hazards ratios for all-cause mortality associated with BMI levels (<20, 20–22, 22–24, 24–26 [reference group], 26–28, 28–30, and ≥30 kg/m2) were 2.03 (95% confidence interval [CI], 1.48–2.78), 1.61 (95% CI, 1.18–2.20), 1.30 (95% CI, 0.95–1.78), 1.00 (reference), 1.12 (95% CI, 0.77–1.64), 1.33 (95% CI, 0.90–1.95), and 1.66 (95% CI, 1.10–2.49), respectively. When stratified by age, sex, or smoking status, the U-shaped association was still present in each subgroup (P > 0.05 for all interactions). Regarding the association of BMI with CVD mortality, a U-shaped trend was also observed.ConclusionsThe present study showed a U-shaped association of BMI with CVD and all-cause mortality among patients with hypertension. A lowest risk of all-cause mortality was found among hypertensive patients with BMI between 24 and 26 kg/m2.

Performance of CO2 enrich CNG in direct injection engine

This paper investigates the potential of utilizing the undeveloped natural gas fields in Malaysia with high carbon dioxide (CO2) content ranging from 28% to 87%. For this experiment, various CO2 proportions by volume were added to pure natural gas as a way of simulating raw natural gas compositions in these fields. The experimental tests were carried out using a 4-stroke single cylinder spark ignition (SI) direct injection (DI) compressed natural gas (CNG) engine. The tests were carried out at 180° and 300° before top dead centre (BTDC) injection timing at 3000 rpm, to establish the effects on the engine performance. The results show that CO2 is suppressing the combustion of CNG while on the other hand CNG combustion is causing CO2 dissociation shown by decreasing CO2 emission with the increase in CO2 content. Results for 180° BTDC injection timing shows higher performance compared to 300° BTDC because of two possible reasons, higher volumetric efficiency and higher stratification level. The results also showed the possibility of increasing the CO2 content by injection strategy.

The prognostic value of admission red cell distribution width-to-platelet ratio in patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention

ObjectiveRed cell distribution width (RDW) is a measure of variation in the size of circulating red blood cells. Recent studies have reported a strong independent relation between elevated RDW and short- and long-term prognosis in various disorders.The aim of the present study was to investigate the relationship between admission RDW-to-platelet ratio (RPR) and in-hospital and long-term prognosis in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI). MethodsA total of 470 consecutive patients with a diagnosis of STEMI who underwent primary PCI were included in this prospective study. The patients were divided into two groups based on their admission RPR: high (>0.061) RPR group and low (≤0.061) RPR group. The patients were followed for adverse clinical outcomes in-hospital and for up to one year after discharge. ResultsIn-hospital cardiovascular mortality, major adverse cardiovascular events (MACE), advanced heart failure and cardiogenic shock were significantly higher in the high RPR group (p<0.05). All-cause and cardiovascular mortality, MACE, fatal reinfarction, advanced heart failure, and rehospitalization for cardiac cause were more frequent in the high RPR group in one-year follow-up (p<0.05). High RPR was found to be a significant independent predictor of one-year cardiovascular mortality in multivariate analysis (p=0.003, OR: 3.106, 95% CI: 1.456–6.623). ConclusionRPR is an inexpensive and readily available biomarker that provides an additional level of risk stratification beyond that provided by conventional risk parameters in predicting long-term MACE and cardiovascular mortality in STEMI.

Risk Factors of Perioperative Cardiac Events in Elderly Patients with Coronary Heart Disease Undergoing Non-cardiac Surgery

To identify the incidence and risk factors of perioperative major adverse cardiac events (MACE) in elderly patients with coronary heart disease (CHD) undergoing non-cardiac surgery. We prospectively analyzed the clinical data of 360 CHD patients who aged 75 years or older undergoing elective intermediate-to high-risk surgery in five medical centers across China from January 2008 to January 2010. The clinical variables included the 12-lead ECG and Troponin I levels after surgery. The combined outcome was defined as all the perioperative MACE in hospital. The risk factors of MACE and their indexes were analyzed with univariate analysis and multivariable logistic regression in SPSS software,together with a risk scoring and stratification system established. Perioperative MACE occurred in 11.94% of elderly CHD patients undergoing non-cardiac surgery. Seven independent risk factors of perioperative MACE for this population were identified,which included angina within 6 months (P=0.001), hypertension(P=0.014), preoperative haematocrit (HCT) <40% (P=0.050), serum creatinine (Scr)>150 mmol/L (P=0.014), ejection fraction(EF) <50% (P=0.019), intraoperative hyoxemia (P=0.019), and operative time>150 min (P=0.001). The risk indexes of these factors were 4,3,3,6,4,5, and 4, respectively. The rate of perioperative MACE increased significantly as the level of risk stratification elevated. Elderly CHD patients undergoing non-cardiac surgery are at high risk of perioperative MACE. Angina within 6 months,hypertension, preoperative HCT<40%, Scr>150 mmol/L, EF<50%, intraoperative hyoxemia, and operative time>150 min can increase the risk of MACE. The risk scoring and stratification system based on the risk factor index can be a valuable parameter for assessing the perioperative cardiac risk of noncardiac surgery for elderly CHD patients.

The prognostic value of admission red cell distribution width-to-platelet ratio in patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention

ObjectiveRed cell distribution width (RDW) is a measure of variation in the size of circulating red blood cells. Recent studies have reported a strong independent relation between elevated RDW and short- and long-term prognosis in various disorders.The aim of the present study was to investigate the relationship between admission RDW-to-platelet ratio (RPR) and in-hospital and long-term prognosis in patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI). MethodsA total of 470 consecutive patients with a diagnosis of STEMI who underwent primary PCI were included in this prospective study. The patients were divided into two groups based on their admission RPR: high (>0.061) RPR group and low (≤0.061) RPR group. The patients were followed for adverse clinical outcomes in-hospital and for up to one year after discharge. ResultsIn-hospital cardiovascular mortality, major adverse cardiovascular events (MACE), advanced heart failure and cardiogenic shock were significantly higher in the high RPR group (p<0.05). All-cause and cardiovascular mortality, MACE, fatal reinfarction, advanced heart failure, and rehospitalization for cardiac cause were more frequent in the high RPR group in one-year follow-up (p<0.05). High RPR was found to be a significant independent predictor of one-year cardiovascular mortality in multivariate analysis (p=0.003, OR: 3.106, 95% CI: 1.456–6.623). ConclusionRPR is an inexpensive and readily available biomarker that provides an additional level of risk stratification beyond that provided by conventional risk parameters in predicting long-term MACE and cardiovascular mortality in STEMI.

Environmental factors associated with phytoplankton succession in a Mediterranean reservoir with a highly fluctuating water level.

Eutrophication and harmful algal blooms have become a worldwide environmental problem. Understanding the mechanisms and processes that control algal blooms is of great concern. The phytoplankton community of Karaoun Reservoir, the largest water body in Lebanon, is poorly studied, as in many freshwater bodies around the Mediterranean Sea. Sampling campaigns were conducted semi-monthly between May 2012 and August 2013 to assess the dynamics of its phytoplankton community in response to changes in physical-chemical and hydrological conditions. Karaoun Reservoir is a monomictic waterbody and strongly stratifies between May and August. Changes in its phytoplankton community were found to be a result of the interplay between water temperature, stratification, irradiance, nutrient availability and water level. Thermal stratification established in spring reduced the growth of diatoms and resulted in their replacement by green algae species when nutrient availability was high and water temperatures lower than 22°C. At water temperature higher than 25°C and low nutrient concentrations in summer, blooms of the cyanobacterium Microcystis aeruginosa occurred. Despite different growth conditions in other lakes and reservoir, cyanobacterium Aphanizomenon ovalisporum dominated at temperatures lower than 23°C in weakly stratified conditions in early autumn and dinoflagellate Ceratium hirundinella dominated in mixed conditions, at low light intensity and a water temperature of 19°C in late autumn. We believe that the information presented in this paper will increase the knowledge about phytoplankton dynamics in the Mediterranean region and contribute to a safer usage of reservoir waters.

Male Homosexual Preference: Where, When, Why?

Male homosexual preference (MHP) has long been of interest to scholars studying the evolution of human sexuality. Indeed, MHP is partially heritable, induces a reproductive cost and is common. MHP has thus been considered a Darwinian paradox. Several questions arise when MHP is considered in an evolutionary context. At what point did MHP appear in the human evolutionary history? Is MHP present in all human groups? How has MHP evolved, given that MHP is a reproductively costly trait? These questions were addressed here, using data from the anthropological and archaeological literature. Our detailed analysis of the available data challenges the common view of MHP being a “virtually universal” trait present in humans since prehistory. The conditions under which it is possible to affirm that MHP was present in past societies are discussed. Furthermore, using anthropological reports, the presence or absence of MHP was documented for 107 societies, allowing us to conclude that evidence of the absence of MHP is available for some societies. A recent evolutionary hypothesis has argued that social stratification together with hypergyny (the hypergyny hypothesis) are necessary conditions for the evolution of MHP. Here, the link between the level of stratification and the probability of observing MHP was tested using an unprecedented large dataset. Furthermore, the test was performed for the first time by controlling for the phylogenetic non-independence between societies. A positive relationship was observed between the level of social stratification and the probability of observing MHP, supporting the hypergyny hypothesis.

Numerical investigation of spontaneous flame propagation under RCCI conditions

This paper presents results from one and two-dimensional direct numerical simulations under Reactivity Controlled Compression Ignition (RCCI) conditions of a primary reference fuel (PRF) mixture consisting of n-heptane and iso-octane. RCCI uses in-cylinder blending of two fuels with different autoignition characteristics to control combustion phasing and the rate of heat release. These simulations employ an improved model of compression heating through mass source/sink terms developed in a previous work by Bhagatwala et al. (2014), which incorporates feedback from the flow to follow a predetermined experimental pressure trace. Two-dimensional simulations explored parametric variations with respect to temperature stratification, pressure profiles and n-heptane concentration. Statistics derived from analysis of diffusion/reaction balances locally normal to the flame surface were used to elucidate combustion characteristics for the different cases. Both deflagration and spontaneous ignition fronts were observed to co-exist, however it was found that higher n-heptane concentration provided a greater degree of flame propagation, whereas lower n-heptane concentration (higher fraction of iso-octane) resulted in more spontaneous ignition fronts. A significant finding was that simulations initialized with a uniform initial temperature and a stratified n-heptane concentration field, resulted in a large fraction of combustion occurring through flame propagation. It was also found that the proportion of spontaneous ignition fronts increased at higher pressures due to shorter ignition delay when other factors were held constant. For the same pressure and fuel concentration, the contribution of flame propagation to the overall combustion was found to depend on the level of thermal stratification, with higher initial temperature gradients resulting in more deflagration and lower gradients generating more ignition fronts. Statistics of ignition delay are computed to assess the Zel’dovich (1980) theory for the mode of combustion propagation based on ignition delay gradients.