79 research outputs found
Critical phenomena soft modes and negative Poisson’s ratio
The article phenomena, soft modes and negative Poisson’ ratio are considered on bases at statistical theory
Simultaneous calculation of the helical pitch and the twist elastic constant in chiral liquid crystals from intermolecular torques
We present a molecular simulation method that yields simultaneously the equilibrium pitch wave number q and the twist elastic constant K2 of a chiral nematic liquid crystal by sampling the torque density. A simulation of an untwisted system in periodic boundary conditions gives the product K2q; a further simulation with a uniform twist applied provides enough information to separately determine the two factors. We test our new method for a model potential, comparing the results with K2q from a thermodynamic integration route, and with K2 from an order fluctuation analysis. We also present a thermodynamic perturbation theory analysis valid in the limit of weak chirality
Strain fluctuational theory of elastic constants of nematic elastomers
In this communication some aspects of strain fluctuation theory of linear elasticity of nematic elastomers are represented
Identification of regions in multiple sequence alignments thermodynamically suitable for targeting by consensus oligonucleotides: application to HIV genome
BACKGROUND: Computer programs for the generation of multiple sequence alignments such as "Clustal W" allow detection of regions that are most conserved among many sequence variants. However, even for regions that are equally conserved, their potential utility as hybridization targets varies. Mismatches in sequence variants are more disruptive in some duplexes than in others. Additionally, the propensity for self-interactions amongst oligonucleotides targeting conserved regions differs and the structure of target regions themselves can also influence hybridization efficiency. There is a need to develop software that will employ thermodynamic selection criteria for finding optimal hybridization targets in related sequences. RESULTS: A new scheme and new software for optimal detection of oligonucleotide hybridization targets common to families of aligned sequences is suggested and applied to aligned sequence variants of the complete HIV-1 genome. The scheme employs sequential filtering procedures with experimentally determined thermodynamic cut off points: 1) creation of a consensus sequence of RNA or DNA from aligned sequence variants with specification of the lengths of fragments to be used as oligonucleotide targets in the analyses; 2) selection of DNA oligonucleotides that have pairing potential, greater than a defined threshold, with all variants of aligned RNA sequences; 3) elimination of DNA oligonucleotides that have self-pairing potentials for intra- and inter-molecular interactions greater than defined thresholds. This scheme has been applied to the HIV-1 genome with experimentally determined thermodynamic cut off points. Theoretically optimal RNA target regions for consensus oligonucleotides were found. They can be further used for improvement of oligo-probe based HIV detection techniques. CONCLUSIONS: A selection scheme with thermodynamic thresholds and software is presented in this study. The package can be used for any purpose where there is a need to design optimal consensus oligonucleotides capable of interacting efficiently with hybridization targets common to families of aligned RNA or DNA sequences. Our thermodynamic approach can be helpful in designing consensus oligonucleotides with consistently high affinity to target variants in evolutionary related genes or genomes
Нулевое цитирование в российской медицинской науке, 1990–2017 гг.
A scientometric study of 51 research institutes of the Ministry of Health of the Russian Federation was carried out. 139,342 publications registered in the Russian Science Citation Index in 1950-2017, were the material of the study. We studied the distribution of publications by year of publication and the number of citations. The publications were divided into two groups: 1) cited one or more times (n = 65395 or 46.9%) and 2) with zero citation (n = 73946 or 53.1%). In 2001-2016 the total number of publications increases linearly (regression coefficient 721 publications or 10% per year). At the same time, the share of cited publications decreased from 72% in 2001 to 46% in 2014, and later, to 4% in 2017. During the period of the highest publication activity (2000-2013), the proportion of cited publications ranged from 17 % to 81% in different institutions (median 61%). The proportion of cited publications may be an indicator of the effectiveness of institutions.Проведено наукометрическое исследование 51 научно-исследовательского института Министерства здравоохранения РФ. Материал исследования составил 139 342 публикации, зарегистрированные в Российском индексе научного цитирования в 1950–2017 гг. Авторы исследовали распределение публикации по году публикации и количеству цитирований. Публикации были разделены на две группы: 1) цитированные один и более раз (n = 65395 или 46,9%) и 2) с нулевым цитированием (n=73946 или 53,1%). В 2001–2016 гг. общее количество публикаций линейно нарастало (коэффициент регрессии 721 публикация или 10% в год). При этом произошло снижение доли цитированных публикаций с 72% в 2001 г. до 46% в 2014 г., а позже, до 4% в 2017 г. В период наибольшей публикационной активности (2000–2013 гг.) доля цитированных публикаций колебалась от 17% до 81% в разных институтах (медиана 61%). Доля цитированных публикаций может быть показателем эффективности работы институтов
Drinking in transition: trends in alcohol consumption in Russia 1994-2004
BACKGROUND: Heavy alcohol consumption is widespread in Russia, but studying changes in drinking during the transition from Communism has been hampered previously by the lack of frequent data. This paper uses 1-2 yearly panel data, comparing consumption trends with the rapid concurrent changes in economic variables (notably around the "Rouble crisis", shortly preceding the 1998 survey round), and mortality. METHODS: Data were from 9 rounds (1994-2004) of the 38-centre Russia Longitudinal Monitoring Survey. Respondents aged over 18 were included (>7,000 per round). Trends were measured in alcohol frequency, quantity per occasion (by beverage type) and 2 measures of potentially hazardous consumption: (i) frequent, heavy spirit drinking (≥80 g per occasion of vodka or samogon and >weekly) (ii) consuming samogon (cheap home-distilled spirit). Trends in consumption, mean household income and national mortality rates (in the same and subsequent 2 years) were compared. Finally, in a subsample of individual male respondents present in both the 1996 and 1998 rounds (before and after the financial crash), determinants of changes in harmful consumption were studied using logistic regression. RESULTS: Frequent, heavy spirit drinking (>80 g each time, ≥weekly) was widespread amongst men (12-17%) throughout, especially in the middle aged and less educated; with the exception of a significant, temporary drop to 10% in 1998. From 1996-2000, samogon drinking more than doubled, from 6% to 16% of males; despite a decline, levels were significantly higher in 2004 than 1996 in both sexes. Amongst women, frequent heavy spirit drinking rose non-significantly to more than 1% during the study. Heavy frequent male drinking and mortality in the same year were correlated in lower educated males, but not in women. Individual logistic regression in a male subsample showed that between 1996 and1998, those who lost their employment were more likely to cease frequent, heavy drinking; however, men who commenced drinking samogon in 1998 were more likely to be rural residents, materially poor, very heavy drinkers or pessimistic about their finances. These changes were unexplained by losses to follow-up. CONCLUSIONS: Sudden economic decline in late 1990s Russia was associated with a sharp, temporary fall in heavy drinking, and a gradual and persistent increase in home distilled spirit consumption, with the latter more common amongst disadvantaged groups. The correlation between heavy drinking and national mortality in lower educated men is interesting, but the timing of RLMS surveys late in the calendar year, and the absence of any correlation between drinking and the subsequent year's mortality, makes these data hard to interpret. Potential study limitations include difficulty in measuring multiple beverages consumed per occasion, and not specifically recording "surrogate" (non-beverage) alcohols
Unrecorded alcohol consumption in Russia: toxic denaturants and disinfectants pose additional risks
In 2005, 30% of all alcohol consumption in Russia was unrecorded. This paper describes the chemical composition of unrecorded and low cost alcohol, including a toxicological evaluation. Alcohol products (n=22) from both recorded and unrecorded sources were obtained from three Russian cities (Saratov, Lipetsk and Irkutsk) and were chemically analyzed. Unrecorded alcohols included homemade samogons, medicinal alcohols and surrogate alcohols. Analysis included alcoholic strength, levels of volatile compounds (methanol, acetaldehyde, higher alcohols), ethyl carbamate, diethyl phthalate (DEP) and polyhexamethyleneguanidine hydrochloride (PHMG). Single samples showed contamination with DEP (275–1269 mg/l) and PHMG (515 mg/l) above levels of toxicological concern. Our detailed chemical analysis of Russian alcohols showed that the composition of vodka, samogon and medicinal alcohols generally did not raise major public health concerns other than for ethanol. It was shown, however, that concentration levels of DEP and PHMG in some surrogate alcohols make these samples unfit for human consumption as even moderate drinking would exceed acceptable daily intakes
Dipolar interactions, molecular flexibility, and flexoelectricity in bent-core liquid crystals
The effects of dipolar interactions and molecular flexibility on the
structure and phase behavior of bent-core molecular fluids are studied using
Monte Carlo computer simulations. Some calculations of flexoelectric
coefficients are also reported. The rigid cores of the model molecules consist
of either five or seven soft spheres arranged in a `V' shape with external bend
angle . With purely repulsive sphere-sphere interactions and
(linear molecules) the seven-sphere model exhibits isotropic,
uniaxial nematic, smectic-A, and tilted phases. With the
smectic-A phase disappears, while the system with shows
a direct tilted smectic--isotropic fluid transition. The addition of
electrostatic interactions between transverse dipole moments on the apical
spheres is generally seen to reduce the degree of tilt in the smectic and solid
phases, destabilize the nematic and smectic-A phases of linear molecules, and
destabilize the tilted smectic-B phase of bent-core molecules. The effects of
adding three-segment flexible tails to the ends of five-sphere bent-core
molecules are examined using configurational-bias Monte Carlo simulations. Only
isotropic and smectic phases are observed. On the one hand, molecular
flexibility gives rise to pronounced fluctuations in the smectic-layer
structure, bringing the simulated system in better correspondence with real
materials; on the other hand, the smectic phase shows almost no tilt. Lastly,
the flexoelectric coefficients of various nematic phases -- with and without
attractive sphere-sphere interactions -- are presented. The results are
encouraging, but the computational effort required is a drawback associated
with the use of fluctuation relations.Comment: 11 pages, 9 figure
The impact of alcohol consumption on patterns of union formation in Russia 1998–2010: An assessment using longitudinal data
Using data from the Russian Longitudinal Monitoring Survey, 1998–2010, we investigated the extent to which patterns of alcohol consumption in Russia are associated with the subsequent likelihood of entry into cohabitation and marriage. Using discrete-time event history analysis we estimated for 16–50 year olds the extent to which the probabilities of entry into the two types of union were affected by the amount of alcohol drunk and the pattern of drinking, adjusted to allow for social and demographic factors including income, employment, and health. The results show that individuals who did not drink alcohol were less likely to embark on either cohabitation or marriage, that frequent consumption of alcohol was associated with a greater chance of entering unmarried cohabitation than of entering into a marriage, and that heavy drinkers were less likely to convert their relationship from cohabitation to marriage
Особенности своеобразия проявлений бронхиальной астмы в гериатрическом возрасте
Results of clinical, laboratory and instrumental examinations of 883 patients with bronchial asthma are given. 347 of the patients were elderly or senile; 322 parameters for each patient were taken into account. The material was processed with a mathematical method of COMOD systemic modelling technology. A reliable correlation between the "Peculiarity of bronchial asthma" parameter and 40 parameters of the geriatric patients’ status was revealed. A complex of reliably interrelated parameters providing the particularities of bronchial asthma manifestations in elderly and senile patients was established. Based on these data conclusions about arising mechanisms of bronchial asthma peculiarities in elderly patients were made.Проведен анализ клинических и лабораторно-инструментальных исследований 883 больных бронхиальной астмой, из них 347 пожилого и старческого возраста (322 показателя состояния у одного больного). Материал обработан с помощью математического метода системного моделирования СОМОД-технологии. Выявлена достоверная связь показателя "особенности бронхиальной астмы" в гериатрическом возрасте с 40 показателями состояния больных. Установлена совокупность достоверно взаимосвязанных показателей, обусловливающих своеобразие проявлений бронхиальной астмы в пожилом и старческом возрасте. На основе полученных данных сделаны выводы о механизмах формирования особенностей бронхиальной астмы у гериатрических больных
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