Solubilization of silica: synthesis, characterization and study of penta-coordinated pyridine N-oxide silicon complexes

In an effort to design agents that could solubilize silica in water, under ambient conditions and pH, as takes place in nature, novel zwitterionic, penta-oxo-coordinated silicon compounds with siliconate cores have been prepared from 4-substituted pyridine N-oxides (H, OMe, morpholino, NO2) as donor ligands, their structures established by 1H, 13C and MS, and the coordination number of silicon, by 29Si NMR. The formation of complexes from pyridine N-oxides is noteworthy since they arise from interaction with a weakly nucleophilic oxygen centre. The ability of the pyridine N-oxides to enhance the solubilization of silica in water has been experimentally demonstrated. Possible rationalization of this observation on the basis of O → Si coordination via the oxygen atom of pyridine N-oxide is suggested

Psychological morbidity, sources of stress and coping strategies among undergraduate medical students of Nepal

<p>Abstract</p> <p>Background</p> <p>In recent years there has been a growing appreciation of the issues of quality of life and stresses involved medical training as this may affect their learning and academic performance. However, such studies are lacking in medical schools of Nepal. Therefore, we carried out this study to assess the prevalence of psychological morbidity, sources and severity of stress and coping strategies among medical students in our integrated problem-stimulated undergraduate medical curriculum.</p> <p>Methods</p> <p>A cross-sectional, questionnaire-based survey was carried out among the undergraduate medical students of Manipal College of Medical Sciences, Pokhara, Nepal during the time period August, 2005 to December, 2006. The psychological morbidity was assessed using General Health Questionnaire. A 24-item questionnaire was used to assess sources of stress and their severity. Coping strategies adopted was assessed using brief COPE inventory.</p> <p>Results</p> <p>The overall response rate was 75.8% (407 out of 525 students). The overall prevalence of psychological morbidity was 20.9% and was higher among students of basic sciences, Indian nationality and whose parents were medical doctors. By logistic regression analysis, GHQ-caseness was associated with occurrence of academic and health-related stressors. The most common sources of stress were related to academic and psychosocial concerns. The most important and severe sources of stress were staying in hostel, high parental expectations, vastness of syllabus, tests/exams, lack of time and facilities for entertainment. The students generally used active coping strategies and alcohol/drug was a least used coping strategy. The coping strategies commonly used by students in our institution were positive reframing, planning, acceptance, active coping, self-distraction and emotional support. The coping strategies showed variation by GHQ-caseness, year of study, gender and parents' occupation.</p> <p>Conclusion</p> <p>The higher level of psychological morbidity warrants need for interventions like social and psychological support to improve the quality of life for these medical students. Student advisors and counselors may train students about stress management. There is also need to bring about academic changes in quality of teaching and evaluation system. A prospective study is necessary to study the association of psychological morbidity with demographic variables, sources of stress and coping strategies.</p

Prevalence, distribution and correlates of tobacco smoking and chewing in Nepal: a secondary data analysis of Nepal Demographic and Health Survey-2006

<p>Abstract</p> <p>Background</p> <p>Nearly four-fifths of estimated 1.1 million smokers live in low or middle-income countries. We aimed to provide national estimates for Nepal on tobacco use prevalence, its distribution across demographic, socio-economic and spatial variables and correlates of tobacco use.</p> <p>Methods</p> <p>A secondary data analysis of 2006 Nepal Demographic and Health Survey (DHS) was done. A representative sample of 9,036 households was selected by two-stage stratified, probability proportional to size (PPS) technique. We constructed three outcome variables 'tobacco smoke', 'tobacco chewer' and 'any tobacco use' based on four questions about tobacco use that were asked in DHS questionnaires. Socio-economic, demographic and spatial predictor variables were used. We computed overall prevalence for 'tobacco smoking', 'tobacco chewing' and 'any tobacco use' i.e. point estimates of prevalence rates, 95% confidence intervals (CIs) after adjustment for strata and clustering at primary sampling unit (PSU) level. For correlates of tobacco use, we used multivariate analysis to calculate adjusted odds ratios (AORs) and their 95% CIs. A p-value < 0.05 was considered as significant.</p> <p>Results</p> <p>Total number of households, eligible women and men interviewed was 8707, 10793 and 4397 respectively. The overall prevalence for 'any tobacco use', 'tobacco smoking' and 'tobacco chewing' were 30.3% (95% CI 28.9, 31.7), 20.7% (95% CI 19.5, 22.0) and 14.6% (95% CI 13.5, 15.7) respectively. Prevalence among men was significantly higher than women for 'any tobacco use' (56.5% versus 19.6%), 'tobacco smoking' (32.8% versus 15.8%) and 'tobacco chewing' (38.0% versus 5.0%). By multivariate analysis, older adults, men, lesser educated and those with lower wealth quintiles were more likely to be using all forms of tobacco. Divorced, separated, and widowed were more likely to smoke (OR 1.49, 95% CI 1.14, 1.94) and chew tobacco (OR 1.36, 95% CI 0.97, 1.93) as compared to those who were currently married. Prevalence of 'tobacco chewing' was higher in eastern region (19.7%) and terai/plains (16.2%). 'Tobacco smoking' and 'any tobacco use' were higher in rural areas, mid-western and far western and mountainous areas.</p> <p>Conclusions</p> <p>Prevalence of tobacco use is considerably high among Nepalese people. Demographic and socioeconomic determinants and spatial distribution should be considered while planning tobacco control interventions.</p

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Unique assemblies of alternating positively and negatively charged layers, directed by hydrogen bonds, ionic interactions, and Π-stacking in the crystal structures of complexes between mellitic acid (benzenehexacarboxylic acid) and five planar aromatic bases

Benzenehexacarboxylic acid, mellitic acid (MA), has been used as a core motif to study possible radial self-assembly using complementary aromatic bases. By mixing water solutions of the components, crystals of the salts of MA with 4-aminopyridine (AP), 4-dimethylamino-pyridine (DM), 2,2P̅1 , a =8.257(2)Å, b =8.986(2)Å, c =9.383(1)Å, α=98.60(1)°, β=96.38(2)°, γ=117.07(1)°

One-step transformation of tricyclopentabenzene (trindane, C<SUB>15</SUB>H<SUB>18</SUB>) to bicyclo(10.3.0)pentadec-1(12)ene- 2,6,7,11-tetrone (C<SUB>15</SUB>H<SUB>18</SUB>O<SUB>4</SUB>) and its aldol product, 12-hydroxy-16-oxatetracyclo(10.3.1.0.<SUP>1,5</SUP>0<SUP>7</SUP>,<SUP>11</SUP>)hexadec-7(11)ene-2,6-dione (C<SUB>15</SUB>H<SUB>18</SUB>O<SUB>4</SUB>)

Ozonolysis of 1 largely results in 2 and 3, having features similar to several classes of natural products. The retention of the C15 pericycle suggests preference for the cleavage of &#8719;-bonds endo to the cyclopentane ring. This unique property of trindane offers opportunities for synthesis of complex natural products from this hydrocarbon that can be made in quantity by acid-catalyzed trimerizatiion of cyclopentanone