Glassy relaxation in a de Vries smectic liquid crystal consisting of bent-core molecules.

We report experimental investigations of a liquid crystal comprising thiophene-based achiral bent-core banana shaped molecules. The compound exhibits the following phase sequence on cooling: Isotropic (517.4 K), N (514.9 K), de Vries SmA (402 K), SmC. Practically no layer contraction was observed across the SmA to SmC transition, confirming the "de Vries" nature of the SmA phase. Interestingly, the crystallization does not occur on cooling the sample, unlike most other liquid crystals. Instead, the SmC phase undergoes a glass transition at 271 K even at a slow cooling rate. The dielectric spectroscopy studies carried out on the sample reveal the presence of a dielectric mode whose relaxation process is of the Cole-Cole type. The relaxation frequency of the mode was found to drop rapidly with decreasing temperature, confirming the glassy behavior. The variation of relaxation frequency with temperature follows the Vogel-Fulcher-Tammann equation, indicating the fragile glassy nature of the sample. This report identifies a bent-core liquid crystal exhibiting a "de Vries" SmA phase and glassy behavior at lower temperatures.

Simple model for self-propulsion of microdroplets in surfactant solution.

We propose a simple active hydrodynamic model for the self-propulsion of a liquid droplet suspended in micellar solutions. The self-propulsion of the droplet occurs by spontaneous breaking of isotropic symmetry and is studied using both analytical and numerical methods. The emergence of self-propulsion arises from the slow dissolution of the inner fluid into the outer micellar solution as filled micelles. We propose that the surface generation of filled micelles is the dominant reason for the self-propulsion of the droplet. The flow instability is due to the Marangoni stress generated by the nonuniform distribution of the surfactant molecules on the droplet interface. In our model, the driving parameter of the instability is the excess surfactant concentration above the critical micellar concentration, which directly correlates with the experimental observations. We consider various low-order modes of flow instability and show that the first mode becomes unstable through a supercritical bifurcation and is the only mode contributing to the swimming of the droplet. The flow fields around the droplet for these modes and their combined effects are also discussed.

Age-related changes in the gut melatonin levels and its possible role in the regulation of feeding and digestibility, with the development of the gut from fingerling to adult stages of carp, Catla catla.

The present study aims to understand the feeding-related age-bound changes in gut histoarchitecture and its response to gut melatonin (GM) titer regulating major digestive enzymes in carp, Catla catla. Therefore, gut samples were collected from different growth stages of carp, viz. (i) fingerling (FL), body weight (BW) ≥ 3 g to ≤ 20 g; (ii) advanced fingerling (AFL), BW > 20 g to ≤ 40 g; (iii) early juvenile (EJv), BW > 40 g to ≤ 70 g; (iv) juvenile (Jv), BW > 70 g to ≤ 200 g; (v) late juvenile (LJv), BW > 200 g to ≤ 300 g; (vi) preadult (PA), BW > 300 g to ≤ 500 g; (vii) subadult (SA), BW > 500 g to ≤ 1.00 kg; and (viii) adult (AD), BW > 1 kg to ≤ 2.5 kg. Data analysis revealed that the highest titer of GM was noted in FL, moderate in AFL, Jv, and PA, lower in EJv, SA, and AD, and lowest in LJv. Results depicted a negative correlation between the development of the gut and its melatonin content. Moreover, GM was positively associated with feeding intensity and gastro-somatic index (GaSI) and negatively related to ovarian onset and development. Following correlation and principal component analysis, several pieces of evidence were recorded on the role of gut melatonin in regulating digestive physiology. Finally, it indicates that gut melatonin has a progressively influential role in improving digestion, particularly protein and microbial digestion, with the development of an adult gut from the fingerling stage.

Clinical Characteristics and Treatment Outcome of Eosinophilic Meningoencephalitis in South Indian Children: Experience From a Prospective Registry.

BACKGROUND: To describe the clinical features and therapeutic outcomes of a prospective cohort of children with eosinophilic meningoencephalitis. METHODS: Children admitted with clinical features suggestive of meningitis along with cerebrospinal fluid (CSF) eosinophilia during the period of 14 years (2008 to 2021) were included. Their baseline characteristics, epidemiologic associations, and treatment outcomes were analyzed and compared with the previous studies. RESULTS: We identified 25 children (13 males) satisfying the inclusion criteria. The median age at presentation was 3.9 years (range 0.8 to 17 years); 68% were aged less than two years. Fourteen (56%) children had a history of exposure to snails. Most of them presented with fever, headache, irritability, lateral rectus palsy, and early papilledema. Symptoms started three to 42 days (median duration: 14 days) before admission to our center. All children had peripheral eosinophilia, which ranged from 9% to 41%. The mean CSF white blood cell count was 416/mm3 (range 50 to 1245 cells/mm3) with CSF eosinophilia ranging from 11% to 80%. Brain magnetic resonance imaging was done in 24 children and was normal in 15 (62.5%). Leptomeningeal enhancement was seen in two (8.3%) children, and other nonspecific changes were noted in seven (29.1%) children. All children recovered without any neurological deficits with a standard treatment regimen of albendazole and oral steroids. All were asymptomatic at the last follow-up. None of them had any recurrence during the follow-up period. CONCLUSION: We report one of the largest clinical series of children with eosinophilic meningoencephalitis from an endemic area of South India.

13C Nuclear Magnetic Resonance Investigations of Molecular Mesogens with a Terminal Phenyl Ring Linked via a Spacer: Odd-Even Effect.

A set of mesogens considered as model molecules to the technologically important twist-bend (NTB) nematogens are investigated. They consist of a three-ring core connected to a phenyl ring via a flexible spacer and displayed enantiotropic nematic and smectic C mesophases. In such systems, odd or even number of atoms present in the spacer could influence the orientation of the terminal phenyl ring and thus have a bearing on designing the NTB phase, considered as intermediate between the nematic and the cholesteric phases. One-dimensional (1D) and two-dimensional (2D) 13C NMR spectra have been recorded in the liquid crystalline phases and the alignment-induced chemical shifts (AIS) and the 13C-1H dipolar couplings obtained. The order parameters of the phenyl rings reveal features relatable to the odd/even number of atoms of the flexible spacer and the type of linkage. The AIS plots of the phenyl rings of the even spacer-based mesogen showed the usual behavior for all of the phenyl rings with a decrease in AIS with increasing temperature. However, for the odd-spacer mesogens, unusual behaviors are noted for the terminal phenyl ring. Thus, two of the mesogens showed an increase of AIS in the smectic C phase that continued till the middle of the nematic phase temperature range, followed by a decrease. The other two odd-spacer mesogens also showed different behaviors. These observations indicate that the terminal phenyl ring is oriented at an angle with respect to the long molecular axis for the odd-spacer mesogens that changes as a function of temperature. The angles have been found to depend on the nature of the atom/group connecting the spacer to the terminal ring and the spacer length. Thus, the present study provides critical information on the design of the odd dimers that are recognized to generate fascinating NTB mesophases.

Optical Anisotropy and Dimple Formation on Films Formed after Drying of Gelatinized Starch Solution Droplets.

We study the microstructures in the drying droplets of gelatinized starch solutions on a flat substrate. Cryogenic scanning electron microscopy studies on the vertical cross-section of these drying droplets for the first time reveal a relatively thinner solid elastic crust of uniform thickness at the free surface, an intermediate mesh region below the crust, and an inner core of a cellular network structure made of starch nanoparticles. We find that the deposited circular films formed after drying are birefringent and azimuthally symmetric with a dimple at their center. We propose that the dimple formation in our sample occurs due to the evaporation-induced stress on the gel network structure in the drying droplet. The polarizing optical microscopic studies show that these films are optically uniaxial at their center and increasingly biaxial away from the center.

Direct method to grasp molecular topology of mesogens through 13C-1H dipolar couplings.

A prime factor in determining liquid crystalline phase formation is the overall molecular shape since molecules undergo rotational motion about the long axis. Molecular topology deals with the connectivity of atomic centers in a given molecular architecture, ultimately giving rise to the gross molecular shape. 13C NMR has emerged as the most important technique in establishing the molecular topology of mesogens in the liquid crystalline phase. In this work, we demonstrate the utility of 13C-1H dipolar couplings determined from 2D separated local field NMR for finding the topology of three different mesogens in the liquid crystalline phase. The core unit of the investigated mesogens fundamentally differs, which may be categorized as rod-like, laterally substituted, and bent-core shapes. 1D and 2D 13C NMR measurements in the liquid crystalline phase revealed fascinating information. The 13C-1H dipolar couplings extracted from 2D NMR are found to be sensitive to topologically variant core units. This permitted us to establish the molecular topology just by looking at the 13C-1H dipolar couplings of the protonated carbons of the constituent phenyl rings. By considering the dipolar couplings of rod-like mesogens as a reference, the large variation in the magnitude of 13C-1H dipolar couplings of the laterally substituted and bent-core mesogens is attributed to changes in the topology of their core units. The order parameters estimated from 13C-1H dipolar couplings enabled visualization of the ordering array of phenyl rings of the mesogens. Interestingly large 13C-1H dipolar couplings are observed for mesogens in which (a) laterally located phenyl ring and (b) central phenyl ring of bent-core mesogens exhibited different trends as revealed by the orientational order parameters.

Spontaneous breaking of chiral symmetry in achiral bent-core liquid crystals: Excluded volume effect.

Bent-Core banana-shaped molecules exhibit tilted polar smectic phases with macroscopically chiral layer order even though the constituent molecules are achiral in nature. Here, we show that the excluded volume interactions between the bent-core molecules account for this spontaneous breaking of chiral symmetry in the layer. We have numerically computed excluded volume between two rigid bent-core molecules in a layer using two types of model structures of them and explored the different possible symmetries of the layer that are favored by the excluded volume effect. For both model structures of the molecule, the C_{2} symmetric layer structure is favored for most values of tilt and bending angle. However, the C_{s} and C_{1} point symmetries of the layer are also possible for one of the model structures of the molecules. We have also developed a coupled XY-Ising model and performed Monte Carlo simulation to explain the statistical origin of spontaneous chiral symmetry breaking in this system. The coupled XY-Ising model accounts for the experimentally observed phase transitions as a function of temperature and electric field.

Benzopyrano-Fused Phenanthridine-Based Columnar Mesogens: Synthesis, Self-organization and Charge-Transport Properties.

Columnar mesogens constitute a fascinating class of supramolecular nano-architectures owing to the exceptional properties induced by their self-assembling behavior. Extending the π-conjugated core in such systems by incorporating heteroatoms extensively influences their mesomorphic, photophysical properties, etc., presenting them as potential candidates for optoelectronic applications. In the present work, a series of novel nitrogen and oxygen-incorporated chromenonaphthophenanthridine-based elliptical dimers have been synthesized through tandem Pictet-Spengler cyclization followed by ipso-aromatic substitution in one-pot. Mesophase characterization has been carried out by employing POM, DSC, and X-ray diffraction studies. Photophysical properties were investigated using UV-vis and emission spectroscopy. Furthermore, the charge transport properties were analyzed by time-of-flight measurements, and the observed ambipolar mobilities were found to be of the order of 10-3  cm2 V-1 s-1 . The high solubility, excellent thermal stability, self-organizing properties, and ambipolar charge transport characteristics make them promising candidates for applications in organic electronics.

Leaning induced layer undulated tilted smectic phase of asymmetric bent-core liquid crystals.

We report the synthesis and experimental studies on the liquid crystalline phase of a homologous series of compounds comprised of strongly asymmetric bent-core banana shaped molecules. Our x-ray diffraction studies clearly indicate that the compounds exhibit a frustrated tilted smectic phase with layer undulated structure. The low value of the dielectric constant as well as switching current measurements indicate the absence of polarization in this layer undulated phase. In spite of the absence of polarization, a planar aligned sample can be transformed irreversibly to a higher birefringent texture on the application of a high electric field. The zero field texture can only be retrieved by heating the sample to the isotropic phase and cooling it subsequently to the mesophase. We propose a double tilted smectic structure having layer undulation to account for the experimental observations with the layer undulation arising due to the leaning of the molecules in the layer.

Novel biallelic variants expand the SLC5A6-related phenotypic spectrum.

The sodium (Na+):multivitamin transporter (SMVT), encoded by SLC5A6, belongs to the sodium:solute symporter family and is required for the Na+-dependent uptake of biotin (vitamin B7), pantothenic acid (vitamin B5), the vitamin-like substance α-lipoic acid, and iodide. Compound heterozygous SLC5A6 variants have been reported in individuals with variable multisystemic disorder, including failure to thrive, developmental delay, seizures, cerebral palsy, brain atrophy, gastrointestinal problems, immunodeficiency, and/or osteopenia. We expand the phenotypic spectrum associated with biallelic SLC5A6 variants affecting function by reporting five individuals from three families with motor neuropathies. We identified the homozygous variant c.1285 A > G [p.(Ser429Gly)] in three affected siblings and a simplex patient and the maternally inherited c.280 C > T [p.(Arg94*)] variant and the paternally inherited c.485 A > G [p.(Tyr162Cys)] variant in the simplex patient of the third family. Both missense variants were predicted to affect function by in silico tools. 3D homology modeling of the human SMVT revealed 13 transmembrane helices (TMs) and Tyr162 and Ser429 to be located at the cytoplasmic facing region of TM4 and within TM11, respectively. The SLC5A6 missense variants p.(Tyr162Cys) and p.(Ser429Gly) did not affect plasma membrane localization of the ectopically expressed multivitamin transporter suggesting reduced but not abolished function, such as lower catalytic activity. Targeted therapeutic intervention yielded clinical improvement in four of the five patients. Early molecular diagnosis by exome sequencing is essential for timely replacement therapy in affected individuals.

Eosinophilic Meningitis and Intraocular Infection Caused by Dirofilaria sp. Genotype Hongkong.

Eosinophilic meningitis caused by human diroflarial infection is rare. We report a case of eosinophilic meningitis and concomitant intraocular dirofilarial infection in India. Sequencing of the mitochondrial genome identified the worm as Dirofilaria sp. genotype Hongkong, a close relative of D. repens nematodes.

Crystal polymorphism of 8OCB liquid crystal consisting of strongly polar rod-like molecules.

We report detailed experimental studies on the different crystal polymorphs of 8OCB (4'-octyloxy-4-cyanobiphenyl) obtained by cooling the sample from its melt. The 8OCB liquid crystal has a stable crystal phase which is known as commercial powder (CP) phase. In addition, it also exhibits various metastable crystal phases such as square-plate, needle phase and long parallelepiped (PP) phase. We identify the metastable crystal state often found on cooling the sample from its melt as PP phase which transforms to stable CP phase on aging at room temperature or by heating it above 312 K. Based on our experimental results, we find that the stable CP crystal phase of 8OCB is not a single homogeneous phase but is the coexistence of fibrillar nano-crystallites embedded in an amorphous phase. The heterogeneous nature of its stable crystal state is an intriguing feature of this pure compound consisting of relatively small rod-like molecules with a strong dipole moment along their long axis.

New Onset Focal Seizure Clusters in Children: Expanding the Spectrum of Anti NMDAR Encephalitis.

INTRODUCTION: Anti-N-methyl-d-aspartate receptor (Anti-NMDAR) Encephalitis classically presents with polysymptomatic presentation of behavioral or cognitive changes, seizures, and focal deficits. Large series in adults and children have described the above features. Monosymptomatic presentation of Anti NMDAR encephalitis is rare and in literature single case reports in adults and children are available. Here we report a series of 6 children presenting with seizure alone and thus expanding the clinical spectrum of Anti NMDAR encephalitis. MATERIALS AND METHODS: This is a a retrospective case series of 6 cases of anti NMDAR encephalitis treated in our institute, which is a tertiary referral center between 2010 and 2014. All the patients with NMDA encephalitis were initially included. The baseline demographics, clinical presentations, investigations (CSF, MRI and EEG), course in the hospital, details of treatment, short and long term outcomes were documented from the available medical records. Children presenting with monosymptomatic seizure clusters were only included in the final analysis. RESULTS: Twenty eight children were diagnosed with ant NMDA R encephalitis during the study period. 22 children had classical polysymptomatic presentations and were not included in this analysis. The remaining 6 children (5 girls and one boy), who presented with only acute seizure clusters were included in the study. All children presented with acute cluster of focal seizures. Four out of six had focal status epilepticus while 2 out of six had recurrent focal seizures. Commonest semiology was clonic seizure in 4/6 and one child had dystonic seizure and one had tonic seizure. All patients were started on steroids and antiepileptic drugs. No other immunomodulators or immunosuppressants were used. On discharge all patients where seizure free and with no focal deficits. CONCLUSION: This is the first series of Anti NMDAR encephalitis presenting as new onset seizure clusters in children. Unlike the existing literature, these children did not develop any other symptoms. We propose that focal encephalitis could be the reason for this monosymptomatic presentation.

Strikingly different molecular organization and molecular order of tetracatenar mesogens in columnar mesophases revealed by XRD and 13C NMR.

For a successful design of functional mesogens, it is paramount to understand factors that contribute to molecular organisation such as molecular shape, the non-covalent interactions of the constituent moieties as well as nanosegregation of incompatible molecular parts. In this study on four tetracatenar mesogens, we show that by a slight change in the length of the terminal chain, the molecular organization changes from lamellar to columnar phase and that the orientational order experiences profound change between the lamellar, the center rectangular columnar and the hexagonal columnar mesophases. We consider here, mesogens that exhibit lamellar and columnar mesophases with five phenyl rings in the central rod-like core which are subjected to XRD and high resolution solid state 13C NMR investigations in their mesophases. The XRD studies indicate that the lower homologs exhibit a lamellar mesophase while the higher homologs show either a centre rectangular columnar phase or a 2D hexagonal columnar mesophase. 13C NMR investigations reveal interesting and strikingly different molecular orientations in each of these phases. For example, values of order parameters of one of the phenyl rings in the core region of the mesogens vary from 0.75 and 0.77 for the lamellar mesogens to 0.45 and 0.17 for the centre rectangular columnar and the hexagonal columnar mesogens respectively. While these values indicate that the mesogenic molecules are oriented along the magnetic field as expected in the lamellar phases, the very low order parameter in the hexagonal columnar phase arises due to molecules distributed azimuthally in layers and undergoing motion about the columnar axis which itself is oriented orthogonal to the magnetic field. Such cutting edge information extracted from the combined use of XRD and 13C NMR studies on tetracatenar mesogens is expected to be of significant use for the study of π-conjugated polycatenar systems where functional properties depend on the molecular orientation and order.

Effectiveness of the 10-valent pneumococcal conjugate vaccine against radiographic pneumonia among children in rural Bangladesh: A case-control study.

BACKGROUND: Pneumococcal conjugate vaccine (PCV) effectiveness against radiographic pneumonia in South Asia is unknown. Bangladesh introduced PCV10 in 2015 using a three dose primary series (3 + 0). We sought to measure PCV10 effectiveness for two or more vaccine doses on radiographic pneumonia among vaccine-eligible children in rural Bangladesh. METHODS: We conducted a matched case-control study over two years from 2015 to 2017 using clinic and community controls in three subdistricts of Sylhet, Bangladesh. Cases were vaccine eligible 3-35 month olds at Upazila Health Complex outpatient clinics with World Health Organization-defined radiographic primary endpoint pneumonia (radiographic pneumonia). Clinic controls were matched to cases within a one week time window by age, sex, and clinic and had an illness unlikely to be Streptococcus pneumoniae; community controls were healthy and similarly matched within a one week time window by age and sex, and distance from the clinic. We estimated adjusted vaccine effectiveness (aVE) using conditional logistic regression. RESULTS: We matched 1262 cases with 2707 clinic and 2461 community controls. Overall, aVE using clinic controls was 21.4% (95% confidence interval, -0.2%, 38.4%) for ≥2 PCV10 doses and among 3-11 month olds was 47.3% (10.5%, 69.0%) for three doses. aVE increased with higher numbers of doses in clinic control sets (p = 0.007). In contrast, aVE using community controls was 7.6% (95% confidence interval, -22.2%, 30.0%) for ≥2 doses. We found vaccine introduction in the study area faster and less variable than expected with 75% coverage on average, which reduced power. Information bias may also have affected community controls. CONCLUSIONS: Clinic control analyses show PCV10 prevented radiographic pneumonia in Bangladesh, especially among younger children receiving three doses. While both analyses were underpowered, community control enrollment - compared to clinic controls - was more difficult in a complex, pluralistic healthcare system. Future studies in comparable settings may consider alternative study designs.

Pseudopolar smectic-C phases of azo-substituted achiral bent-core hockey-stick-shaped molecules.

We report experimental studies on an azo-substituted compound consisting of bent-core hockey-stick-shaped molecules. The experimental results establish two pseudopolar tilted smectic phases, which are characterized by an in-plane axial-vector order parameter in addition to tilt order in the smectic layers. Electro-optical measurements in the mesophases indicate that the birefringence of the sample strongly depends on the applied electric field. We develop a theoretical model to account for this observation. The change in the birefringence of the sample arises from the field-induced reorientation of the tilt plane of the molecules in the layer above a threshold field. The effect is analogous to the field-induced Freedericksz transition which is quadratic in the applied electric field.

Training and standardization of general practitioners in the use of lung ultrasound for the diagnosis of pediatric pneumonia.

BACKGROUND: Pneumonia is a leading cause of death in children of low-resource settings. Barriers to care include an early and accurate diagnosis. Lung ultrasound is a novel tool for the identification of pediatric pneumonia; however, there is currently no standardized approach to train in image acquisition and interpretation of findings in epidemiological studies. We developed a training program for physicians with limited ultrasound experience on how to use ultrasound for the diagnosis of pediatric pneumonia and how to standardize image interpretation using a panel of readers. METHODS: Twenty-five physicians participating in the training program conducted lung ultrasounds in all children with suspected pneumonia, aged 3 to 35 months, presenting to three subdistrict hospitals in Sylhet, Bangladesh, between June 2015 and September 2017. RESULTS: A total of 9051 pediatric lung ultrasound assessments were conducted through 27 months of data collection. Study physicians underwent training and all were successfully standardized, achieving 91% agreement and maintained a sensitivity and specificity of 88% and 92%, respectively, when their diagnosis was compared with experts. Overall kappa between two readers was high (0.86, 95% confidence interval [CI], 0.84-0.87), and remained high when a third expert reader was included (0.80, 95% CI, 0.79-0.81). Agreement and kappa statistics were similarly high when stratified by age, sex, presence of danger signs, or hypoxemia. CONCLUSIONS: Lung ultrasound is a novel tool for the diagnosis of pediatric pneumonia with evidence supporting its validity and feasibility of implementation. Here we introduced a training program that resulted in a high level of inter-sonographer agreement.