205 research outputs found
Unified molecular field theory of nematic, smectic-A, and smectic-C phases
A unified mean-field molecular theory of nematic (NU), smectic A (SmA), and smectic C (SmC) liquid crystal phases, composed of uniaxial nonpolar molecules, is developed taking into account the variation of all orientational and translational order parameters in these phases. Numerical results, obtained by direct global minimization of the free energy, are presented in the form of three typical phase diagrams of different topology. Temperature variation of the relevant order parameters in different sequences of phases is analyzed for various cross sections of the phase diagrams. The present model enables one to reproduce all possible sequences of phase transitions between the given phases including isotropic (Iso)-NU-SmA-SmC, Iso-NU-SmC, Iso-SmA-SmC, and Iso-SmC. The properties of the NAC point, where the NU, SmA, and SmC structures coexist, are considered in detail and the shape of the phase diagram in the vicinity of the NAC point is compared with existing experimental data
Polar interactions between bentâcore molecules as a stabilising factor for inhomogeneous nematic phases with spontaneous bend deformations
It is generally accepted that the transition into the twistâbend nematic phase (NTB) is driven by an elastic instability related to the reduction of the bend elastic constant. Here we use a molecularâstatistical theory to show that sufficiently strong polar interactions between bentâshaped molecules may lead to experimentally observed reduction of the bend elastic constant in the nematic phase even if electrostatic dipole-dipole interactions are not taken into account. We propose a simple model of bentâcore particles and derive explicit analytical expressions which enable one to understand how polar molecular shape affects the elastic constants, and, in particular, the important role of the bend angle. Numerical graphs showing temperature variations of all elastic constants are also presented including the variation of the bend and splay elastic constants before and after the renormalization determined by local polar order of molecular steric dipoles and the corresponding polar correction to the oneâparticle distribution function
Stability of Biaxial Nematic Phase for Systems with Variable Molecular Shape Anisotropy
We study the influence of fluctuations in molecular shape on the stability of
the biaxial nematic phase by generalizing the mean field model of Mulder and
Ruijgrok [Physica A {\bf 113}, 145 (1982)]. We limit ourselves to the case when
the molecular shape anisotropy, represented by the alignment tensor, is a
random variable of an annealed type. A prototype of such behavior can be found
in lyotropic systems - a mixture of potassium laurate, 1-decanol, and ,
where distribution of the micellar shape adjusts to actual equilibrium
conditions. Further examples of materials with the biaxial nematic phase, where
molecular shape is subject to fluctuations, are thermotropic materials composed
of flexible trimeric- or tetrapod-like molecular units. Our calculations show
that the Gaussian equilibrium distribution of the variables describing
molecular shape (dispersion force) anisotropy gives rise to new classes of the
phase diagrams, absent in the original model. Depending on properties of the
shape fluctuations, the stability of the biaxial nematic phase can be either
enhanced or depressed, relative to the uniaxial nematic phases. In the former
case the splitting of the Landau point into two triple points with a direct
phase transition line from isotropic to biaxial phase is observed.Comment: 18 pages containing 6 figure
Trajectories in physical functioning at older age in relation to childhood and adulthood SES and social mobility: a population-based cohort study
INTRODUCTION: Older age is associated with the deterioration of physical functioning (PF), and low PF is strongly related to poor quality of life among older people. We conducted a study to examine the trajectories of PF between middle and old age, considering sex differences as well as the association between socioeconomic status (SES) at different life stages and changes in PF. METHODS: We analyzed data from the Polish arm of the HAPIEE (Health, Alcohol and Psychosocial factors In Eastern Europe) study, including 1,116 men and 1,178 women aged 45â64âyears at baseline. Adult and childhood SES and social mobility were assessed using a retrospectively focused questionnaire. PF was assessed using the 10-question SF-36 scale at baseline examination, face-to-face re-examination, and three postal surveys, covering up to 20âyears (on average, 18âyears). We employed Generalized Estimating Equations models to assess changes in PF scores over time and compare PF trajectories across different SES categories. RESULTS: After adjusting for age and other covariates, we found that, in both sexes, participants with always middle or high SES, as well as those who reported upward mobility, had higher PF scores at baseline compared to those with always low SES. A decline in PF between middle and old age was observed in all SES groups; however, the decline was slower in participants with always middle or high SES compared to those with always low SES. CONCLUSION: This cohort study revealed that lower SES and downward social mobility were cross-sectionally associated with poorer PF, while upward social mobility seemed to largely reverse the effect of low childhood SES. In addition to the cross-sectional associations observed at baseline, advantaged SES was also significantly associated with a slower decline in PF over an 18-year follow-up period
Changes in Socioeconomic Status as Predictors of Cardiovascular Disease Incidence and Mortality: A 10-Year Follow-Up of a Polish-Population-Based HAPIEE Cohort
Although the inverse association between socioeconomic status (SES) and cardiovascular disease (CVD) is well established, research on the effect of changes in the SES throughout life on CVD risk in populations with different social backgrounds remains scarce. This study aimed to assess the relationship between childhood SES, adulthood SES, and changes in SES over time, and CVD incidence and mortality in a Polish urban population. In addition, the predictive performance of the SES index was compared with education alone. A cohort study with a 10-year follow-up was conducted, in which a random sample of 10,728 residents in KrakĂłw aged 45â69 years were examined. The SES was assessed at baseline using data on education, parentsâ education, housing standard at the age of 10 years, professional activity, household amenities, and difficulties in paying bills and buying food. SES categories (low, middle, and high) were extracted using cluster analyses. Information on new CVD cases was obtained from questionnaires in subsequent phases of the study and confirmed by reviewing clinical records. Data on deaths and causes were obtained from the residentsâ registry, Central Statistical Office, and the participantsâ families. The effect of the SES index on the risk of CVD was assessed using Cox proportional hazard models. In male and female participants, the CVD incidence and mortality were observed to be 27,703 and 32,956 person-years (384 and 175 new CVD cases) and 36,219 and 40,048 person-years (159 and 92 CVD deaths), respectively. Childhood SES was not associated with CVD incidence and mortality. A protective effect of high adulthood SES against CVD mortality was observed in men and women (HR = 0.59, 95% CI = 0.31â0.97; HR = 0.33, 95% CI = 0.14â0.75, respectively). In women, downward social mobility was related to 2.24 and 3.75 times higher CVD incidence and mortality, respectively. In men, a protective effect against mortality was observed in upward mobility (HR = 0.50, 95% CI = 0.29â0.84). Model discrimination was similar for the SES index and education alone for the association with CVD incidence. In women, the SES index was a slightly better predictor of CVD mortality than education alone (C-index = 0.759, SE = 0.0282 vs. C-index = 0.783, SE = 0.0272; p = 0.041). In conclusion, high adulthood SES, but not childhood SES, may be considered to be a protective factor against CVD in urban populations in high-CVD-risk regions. No effects of critical periods in early life were observed on CVD risk. In later life, social mobility was found to affect CVD mortality in both men and women. In men, a protective effect of upward mobility was confirmed, whereas in women, an increased CVD risk was related to downward mobility. It can be concluded that CVD prevention may be beneficial if socioeconomic potentials are strengthened in later life
A Mediterranean-type diet is associated with better metabolic profile in urban Polish adults: Results from the HAPIEE study
The aim of this study was to evaluate the relationship between adherence to a Mediterranean-type diet and metabolic syndrome (MetS) in the Polish arm of the Health, Alcohol and Psychosocial factors In Eastern Europe (HAPIEE) cohort study
Accumulation of psychosocial risk factors and incidence of cardiovascular disease: a prospective observation of the Polish HAPIEE cohort
BACKGROUND: Psychosocial risk factors for cardiovascular disease (CVD) are known to cluster in individuals, but the effect of cumulative exposure has not been thoroughly described in terms of CVD risk. AIMS: The aim of the study was to assess the relationship between accumulation of psychosocial risk factors such as low education, material deprivation, depressive symptoms, and low perceived control and the risk of incident CVD. METHODS: This cohort study with 11âyear followâup included a random population sample (age, 45-69 years). Psychosocial factors were assessed using standard tools. Accumulation of psychosocial risk factors was determined by summing up the number of psychosocial factors experienced. The risk of incident CVD depending on the number of psychosocial factors was estimated (reference, no psychosocial factors). Cox proportional hazards models were fitted. RESULTS: In total, 43 572 and 51 772 personâyears were analyzed. There were 479 and 291 new CVD cases in men and women, respectively. An ageâadjusted model showed an increase in CVD risk in men exposed to 3 and 4 psychosocial risk factors by nearly 60% and 125%, respectively (P <0.05). Further adjustment waved the association in individual strata, but a significant linear trend was observed. In women, in a fully adjusted model, the second and subsequent risk factors increased the risk of CVD by nearly 70% up to over 2âfold (P <0.001). The total population attributable risk associated with exposure to psychosocial risk factors in women was 34.1%. CONCLUSIONS: The accumulation of psychosocial risk factors was associated with increased risk of CVD. In men, the relation was substantially explained by classic risk factors. In women, about one-third of incident CVD cases could be attributed to psychosocial risk factors
Treatment goal attainment for secondary prevention in coronary patients with or without diabetes mellitus : Polish multicenter study POLASPIRE
Introduction:
Cardiovascular disease is still a leading cause of death in Poland and across Europe. The aim of this study was to assess the attainment of the main treatment goals for secondary cardiovascular prevention in coronary patients with or without diabetes mellitus (DM) in Poland.
Material and methods:
The study group included 1026 patients (65.5 ±9 y.o.; males: 72%) included at least 6 months after the index hospitalisation for myocardial infarction, unstable angina, elective percutaneous coronary intervention or coronary artery bypass surgery. The target and treatment goals were defined according to the 2016 European Society of Cardiology guidelines on cardiovascular prevention.
Results:
Patients with DM (n = 332; 32%) were slightly older compared to non-diabetic (n = 694) individuals (67.2 ±7 vs. 64.6 ±9 years old; p < 0.0001). The DM goal was achieved in 196 patients (60%). The rate of primary (LDL: 51% vs. 35%; p < 0.0001) and secondary (non-HDL: 56% vs. 48%; p < 0.02) goal attainment was higher in DM(+) compared to DM(â) patients. The rate of target blood pressure was lower in DM(+) than in normoglycemic patients (52% vs. 61% at < 140/90 mm Hg, p < 0.01. As expected, goal achievement of normal weight (9.5% vs. 19%; p < 0.0001) and waist circumference (7% vs. 15%; p < 0.001) was lower in diabetic patients and the rate of regular physical activity was similar (DM+ 12% vs. DMâ 14%; p = ns). Finally, there was no difference in active smokers (DM+ 23% vs. DMâ 22%; p = ns).
Conclusions:
Great majority of Polish patients in secondary prevention do not achieve treatment goals. Although lipid goals attainment is better in DM and the rate of smokers is similar, the management of all risk factors needs to be improved
ATHLOS Healthy Aging Scale score as the predictor of all-cause mortality in Poland and Czechia
Background: The ATHLOS consortium (Aging Trajectories of Health-Longitudinal Opportunities and Synergies) used data from several aging cohorts to develop a novel scale measuring healthy aging comprehensively and globally (ATHLOS Healthy Aging Scale). In the present study, we assessed the predictive performance of the ATHLOS Healthy Aging Scale for all-cause mortality in middle-aged and older adults. Methods: Data from the Polish and Czech HAPIEE (Health Alcohol and Psychosocial factors In Eastern Europe) prospective cohorts were used. There were 10,728 Poles and 8,857 Czechs recruited. The ATHLOS Healthy Aging Scale score was calculated for all participants using data from the baseline examination carried out from 2002 to 2005. The follow-up for all-cause mortality was completed over 14 years. The associations between quintiles of the ATHLOS Healthy Aging Scale and all-cause mortality were estimated using Cox proportional hazards models. Results: A total of 9,922 Polish and 8,518 Czech participants contributed ATHLOS Healthy Aging Scale and mortality data with 1,828 and 1,700 deaths, respectively. After controlling for age, the ATHLOS Healthy Aging Scale score was strongly associated with mortality in a graded fashion for both genders and countries (hazard ratios for lowest vs. highest quintile were 2.98 and 1.96 for Czech and Polish women and 2.83 and 2.66 for Czech and Polish men, respectively). The associations were only modestly attenuated by controlling for education, economic activity, and smoking, and there was further modest attenuation after additional adjustment for self-rated health. Conclusion: The novel ATHLOS Healthy Aging Scale is a good predictor of all-cause mortality in Central European urban populations, suggesting that this comprehensive measure is a useful tool for the assessment of the future health trajectories of older persons
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