Stability of the chiral crystal phase and breakdown of the cholesteric phase in mixtures of active-passive chiral rods

In this study, we aim to explore the effect of chirality on the phase behavior of active helical particles driven by two-temperature scalar activity. We first calculate the equation of state of soft helical particles of various intrinsic chiralities using molecular dynamics (MD) simulation. In equilibrium, the emergence of various liquid crystal (LC) phases such as nematic (N), cholesteric , smectic (Sm) and crystal (K) crucially depends on the presence of walls that induce planar alignment. Next, we introduce activity through the two-temperature model: keep increasing the temperature of half of the helical particles (labeled as 'hot' particles) while maintaining the temperature of the other half at a lower value (labeled as 'cold' particles). Starting from a homogeneous isotropic (I) phase, we find the emergence of 2-TIPS: two temperature-induced phase separations between the hot and cold particles. We also observe that the cold particles undergo an ordering transition to various LC phases even in the absence of a wall. This observation reveals that the hot-cold interface in the active system plays the role of a wall in the equilibrium system by inducing an alignment direction for the cold particles. However, in the case of a cholesteric phase, we observe that activity destabilizes the phase by inducing smectic ordering in the cold zone while an isotropic structure in the hot zone. The smectic ordering in the cold zone eventually transforms to a chiral crystal phase with high enough activity.

Effect of confinement and topology: 2-TIPS vs. MIPS

2-TIPS (two temperature induced phase separation) refers to the phase separation phenomenon observed in mixtures of active and passive particles which are modelled using scalar activity. The active particles are connected to a thermostat at high temperature while the passive particles are connected to the thermostat at low temperature and the relative temperature difference between "hot" and "cold" particles is taken as the measure of the activity χ of the non-equilibrium system. The study of such binary mixtures of hot and cold particles under various kinds of confinement is an important problem in many physical and biological processes. The nature and extent of phase separation are heavily influenced by the geometry of confinement, activity, and density of the non-equilibrium binary mixture. Investigating such 3D binary mixtures confined by parallel walls, we observe that the active and passive particles phase separate, but the extent of phase separation is reduced compared to bulk phase separation at high densities and enhanced at low densities. However, when the binary mixture of active and passive particles is confined inside a spherical cavity, the phase separation is radial for small radii of the confining sphere and the extent of phase separation is higher compared to their bulk counterparts. Confinement leads to interesting properties in the passive (cold) region like enhanced layering and high compression in the direction parallel to the confining wall. In 2D, both the bulk and confined systems of the binary mixture show a significant decrement in the extent of phase separation at higher densities. This observation is attributed to the trapping of active particles inside the passive cluster, which increases with density. Thus the 2D systems show structures more akin to dense-dilute phase co-existence, which is observed in motility induced phase separation in 2D active systems. The binary mixture constrained on the spherical surface also shows similar phase co-existence. Our analyses reveal that the coexistent densities observed in 2-TIPS on the spherical surface agree with the findings of previous studies on MIPS in active systems on a sphere.

Packing and emergence of the ordering of rods in a spherical monolayer

Spatially ordered systems confined to surfaces such as spheres exhibit interesting topological structures because of curvature induced frustration in orientational and translational order. The study of these structures is important for investigating the interplay between the geometry, topology, and elasticity, and for their potential applications in materials science, such as engineering directionally binding particles. In this work, we numerically simulate a spherical monolayer of soft repulsive spherocylinders (SRSs) and study the packing of rods and their ordering transition as a function of the packing fraction. In the model that we study, the centers of mass of the spherocylinders (situated at their geometric centers) are constrained to move on a spherical surface. The spherocylinders are free to rotate about any axis that passes through their respective centers of mass. We show that, up to moderate packing fractions, a two dimensional liquid crystalline phase is formed whose orientational ordering increases continuously with increasing density. This monolayer of orientationally ordered SRS particles at medium densities resembles a hedgehog-long axes of the SRS particles are aligned along the local normal to the sphere. At higher packing fractions, the system undergoes a transition to the solid phase, which is riddled with topological point defects (disclinations) and grain boundaries that divide the whole surface into several domains.

Vitamin D deficiency in patients with tuberculous meningitis and its relationship with treatment outcome

SETTING

Data on vitamin D deficiency in tuberculous meningitis (TBM) and its relationship with treatment outcomes are limited. Some of the beneficial effects of vitamin D might be mediated through interleukin-1β (IL-1β).

OBJECTIVE

To assess the frequency of vitamin D deficiency among TBM patients, its association with treatment outcomes and correlation between vitamin D and IL-1β levels in cerebrospinal fluid (CSF).

DESIGN

We prospectively studied a consecutive sample of human immunodeficiency virus-negative patients with TBM treated at a hospital in southern India. We defined good outcome as survival without severe neurological disability. Serum total 25-hydroxy vitamin D (25[OH]D) and IL-1β levels in CSF were estimated on pretreatment samples.

RESULTS

We studied 40 patients with TBM; 22 (55%) patients had stage 3 disease. Treatment outcome was poor in 21 (53%) patients: 15 (38%) patients died and 6 (15%) had severe neurological disability. The overall mean serum 25(OH)D level was 32.30 ± 16.38 ng/ml. Ten (25%) patients had vitamin D deficiency (<20 ng/ml), and 12 (30%) patients had vitamin D insufficiency (20-30 ng/ml). However, pretreatment serum 25(OH)D levels did not differ significantly by outcome (good vs. poor outcome: 28.30 ± 14.96 vs. 35.92 ± 17.11 ng/ml, P = 0.141). Moreover, IL-1β levels in CSF did not correlate with serum 25(OH)D levels (Spearman's ρ 0.083, P = 0.609).

CONCLUSION

Vitamin D deficiency/insufficiency is common among patients with TBM. However, serum 25(OH)D levels are not associated with IL-1β levels in CSF or treatment outcome.

Novel strain of Shigella dysenteriae serotype 7 from India

We describe a strain of Shigella dysenteriae serotype 7 which had novel biochemical and genetic characters. Unlike other S. dysenteriae, it produced gas, fermented mannitol, was a late-lactose fermenter and harboured the set 1A and set 1B genes. The significance of such atypical strains is that they are difficult to identify. If such strains are missed, they could prove to be a serious public health problem because the infectious dose is very low and they may harbour integrons contributing to drug resistance.

Evaluation of ELISA and dot blots for the serodiagnosis of neurocysticercosis, in children found to have single or multiple enhancing lesions in computerized tomographic scans of the brain

Although human neurocysticercosis (NCC) is being increasingly recognized in children, diagnosis of the disease can be difficult, and the 'gold standard' criteria that indicate an unambiguous case have still to be established. In the present study, the performances of an ELISA and dot-blot assay, for the detection of antibodies against antigens from larval Taenia solium, were investigated and compared, using sera, from children aged 5-12 years, that were diluted to at least 1:400. Eighty of the subjects (20 aged 5-<8 years and 60 older children) each had the signs and symptoms of NCC, including one brain lesion (N=69) or multiple brain lesions (N=11) that were visible by computed tomography. Another 100 sera, from children who had tubercular meningitis (N=20) or a parasitic disease other than taeniasis/cysticercosis (N=20) or, apart from a minor respiratory-tract infection, appeared healthy (N=60), were also investigated. Most (86%) of the cases of NCC had presented with focal seizures. Analysis of antibody response indicated that the optimum threshold titres for seropositivity were 1:800 for the ELISA and 1:6400 for the dot-blot assays. When used with these thresholds, the ELISA gave a sensitivity, specificity, positive and negative predictive values and diagnostic efficacy of 89%, 81%, 79%, 90%, 85%, respectively. The corresponding values for the dot-blot assay were similar, at 89%, 73%, 72.5%, 89%, 82%, respectively. Both assays were more sensitive, in the detection of the specific antibody response, when used among the paediatric cases of NCC who had multiple brain lesions (100%) than when used among the single-lesion cases (87%). As the ELISA gave higher specificity and diagnostic efficacy than the dot-blot assay, it should be considered the better method for the serological confirmation of NCC in children.

Risk factors for hospital admissions associated with adverse drug events

STUDY OBJECTIVE

To identify predictors of hospital admissions associated with adverse drug events (ADEs) and to determine the preventability of ADEs in patients admitted to two hospitals.

DESIGN

Prospective observational study.

SETTING

Medical admission units at two British National Health Service hospitals in the United Kingdom.

PATIENTS

3904 adults age 16 years or older who were admitted to the two hospitals between June 2006 and November 2007.

MEASUREMENTS AND MAIN RESULTS

Clinical pharmacists identified hospital admissions associated with drug-related problems by using medical record review, supplemented by patient interview for those identified as having an ADE. The contribution of ADEs to hospital admission and the causality, severity, and preventability of the events were independently assessed by a multidisciplinary clinical team. Multivariate logistic regression was used to identify predictors of hospital admissions associated with ADEs, and a maximum-likelihood multinomial model was used to examine predictors of the preventability of ADEs. Of the 3904 patients included in the analysis, 439 (11.2%) were judged by the review panel to have experienced ADEs. Of these, 209 patients (47.6%) experienced preventable ADEs. Four independent variables were found to have significant relationships with ADE admissions and preventability of ADEs: patient age, length of time since starting new drug, total number of prescription drugs, and hospital site. Drug classes most commonly associated with preventable ADEs were antiplatelet drugs, anticoagulants, diuretics (loop and thiazide diuretics), angiotensin-converting enzyme inhibitors, and antiepileptic drugs.

CONCLUSION

Adverse drug events are an important cause of hospital admission. Better systems for health care practitioners to identify patients at high risk of preventable hospital admissions associated with ADEs (e.g., age > 65 years old, receiving more than five drugs, and starting new high-risk drugs) should be implemented in order to minimize the risks to patients and the burden on the health care system.

Aerobiological investigation and in vitro studies of pollen grains from 2 dominant avenue trees in Kolkata, India

BACKGROUND

Peltophorum pterocarpum and Delonix regia are dominant avenue trees in the city of Kolkata in India. They are well adapted to the humid tropical climate and also grow commonly in different parts of the country. Their pollen grains are reported to be airborne.

OBJECTIVE

The aim of this study was to conduct an aerobiological survey in Kolkata to determine the concentration and seasonal periodicity of pollen grains from P pterocarpum and D regia and to analyze the meteorological factors responsible for their levels in the atmosphere. In addition, we analyzed the prevalence of sensitization due to these grains among patients with seasonal respiratory allergy.

METHODS

An aerobiological survey was conducted with a volumetric Burkard sampler from 2004 to 2006. Correlations between meteorological parameters and pollen grain concentrations were assessed by Spearman correlation test. The protein profile of the pollen extracts was studied by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Finally, the allergenic potential of the pollen extracts was evaluated in patients with respiratory allergy by skin prick test, immunoglobulin (Ig) E enzyme-linked immunosorbent assay, and IgE immunoblotting.

RESULTS

P pterocarpum and D regia pollen grains occur from March to June and April to July, respectively. The pollen concentrations showed statistically significant positive correlations with maximum temperature and wind speed. Positive reactions to P pterocarpum and D regia were observed in 26% and 22% of the patients, respectively. Many protein bands were detected in the pollen extracts over a wide molecular weight range. A total of 5 (P pterocarpum pollen) and 8 (D regia pollen) protein fractions were detected by IgE immunoblotting.

CONCLUSION

P pterocarpum and D regia pollen grains are dominant in the atmosphere of south Kolkata and they are influenced by temperature. The pollen grains release proteins that may be responsible for immediate hypersensitivity reactions in sensitive patients.