Access to Stereoblock Polyesters via Irreversible Chain-Transfer Ring-Opening Polymerization (ICT-ROP).

Precise control over polymer microstructure can enable the molecular tunability of material properties and represents a significant challenge in polymer chemistry. Stereoblock copolymers are some of the simplest stereosequenced polymers, yet the synthesis of stereoblock polyesters from prochiral or racemic monomers outside of "simple" isotactic stereoblocks remains limited. Herein, we report the development of irreversible chain-transfer ring-opening polymerization (ICT-ROP), which overcomes the fundamental limitations of single catalyst approaches by using transmetalation (e.g., alkoxide-chloride exchange) between two catalysts with distinct stereoselectivities as a means to embed temporally controlled multicatalysis in ROP. Our combined small-molecule model and catalytic polymerization studies lay out a clear molecular basis for ICT-ROP and are exploited to access the first examples of atactic-syndiotactic stereoblock (at-sb-st) polyesters, at-sb-st polyhydroxyalkanoates (PHAs). We achieve high levels of control over molecular weight, tacticity, monomer composition, and block structures in a temporally controlled manner and demonstrate that stereosequence control leads to polymer tensile properties that are independent of thermal properties.

Halogen Bond via an Electrophilic π-Hole on Halogen in Molecules: Does It Exist?

This study reveals a new non-covalent interaction called a π-hole halogen bond, which is directional and potentially non-linear compared to its sister analog (σ-hole halogen bond). A π-hole is shown here to be observed on the surface of halogen in halogenated molecules, which can be tempered to display the aptness to form a π-hole halogen bond with a series of electron density-rich sites (Lewis bases) hosted individually by 32 other partner molecules. The [MP2/aug-cc-pVTZ] level characteristics of the π-hole halogen bonds in 33 binary complexes obtained from the charge density approaches (quantum theory of intramolecular atoms, molecular electrostatic surface potential, independent gradient model (IGM-δginter)), intermolecular geometries and energies, and second-order hyperconjugative charge transfer analyses are discussed, which are similar to other non-covalent interactions. That a π-hole can be observed on halogen in halogenated molecules is substantiated by experimentally reported crystals documented in the Cambridge Crystal Structure Database. The importance of the π-hole halogen bond in the design and growth of chemical systems in synthetic chemistry, crystallography, and crystal engineering is yet to be fully explicated.

Magnitude and determinants of psychological morbidities among pregnant women: Results from a pregnancy cohort in rural Central India.

Background: Psychological morbidities are one of the emerging global health problems. It affects a considerable number of ante-natal women leading to consequences during the postnatal period as well. We conducted this research to study the magnitude and determinants of psychological morbidities during pregnancy. Methods: In this study, we included 650 pregnant women from an established cohort of 2500 pregnant women and assessed the psychological morbidities among them using the GMHAT/PC tool. Results: The overall prevalence of psychological morbidities during pregnancy was 14.6%, with anxiety and depression being the leading ones. Low education levels, lower socio-economic status, unintended pregnancy, complicated previous pregnancy, lack of family and social support, and domestic violence increased the odds of psychological morbidity. On Multivariate logistic regression, Low education levels increased the odds to more than twice [illiterate/primary schooling OR: 4.00, p = 0.026; secondary schooling OR: 2.64, p = 0.034; high school OR: 2.60, p = 0.033] unintended pregnancy [OR: 1.91, p = 0.043] and lack of family support [OR: 7.19, p < 0.001] increased the odds of psychological morbidity among pregnant women. Conclusion: Bringing these issues to the mainstream and addressing them by developing interventions to address them during the lifecycle of a female will help to prevent episodes of psychological stress and morbidity among pregnant females.

Probing multiple algorithms to calculate brain age: Examining reliability, relations with demographics, and predictive power.

The calculation of so-called "brain age" from structural MRIs has been an emerging biomarker in aging research. Data suggests that discrepancies between chronological age and the predicted age of the brain may be predictive of mortality and morbidity (for review, see Cole, Marioni, Harris, & Deary, 2019). However, with these promising results come technical complexities of how to calculate brain age. Various groups have deployed methods leveraging different statistical approaches, often crafting novel algorithms for assessing this biomarker derived from structural MRIs. There remain many open questions about the reliability, collinearity, and predictive power of different algorithms. Here, we complete a rigorous systematic comparison of three commonly used, previously published brain age algorithms (XGBoost, brainageR, and DeepBrainNet) to serve as a foundation for future applied research. First, using multiple datasets with repeated structural MRI scans, we calculated two metrics of reliability (intraclass correlations and Bland-Altman bias). We then considered correlations between brain age variables, chronological age, biological sex, and image quality. We also calculated the magnitude of collinearity between approaches. Finally, we used machine learning approaches to identify significant predictors across brain age algorithms related to clinical diagnoses of cognitive impairment. Using a large sample (N = 2557), we find all three commonly used brain age algorithms demonstrate excellent reliability (r > .9). We also note that brainageR and DeepBrainNet are reasonably correlated with one another, and that the XGBoost brain age is strongly related to image quality. Finally, and notably, we find that XGBoost brain age calculations were more sensitive to the detection of clinical diagnoses of cognitive impairment. We close this work with recommendations for future research studies focused on brain age.

Effectiveness of Japanese encephalitis vaccination among children in central India.

Japanese encephalitis (JE) disease among children continues in central India despite vaccination implemented in the routine immunization program. Therefore, we planned to estimate the JE vaccination effectiveness among children by undertaking a 1:2 individually-matched population-based case-control study from August 2018 to October 2020. The laboratory-confirmed JE cases aged 1-15 years were enrolled along with neighborhood controls without fever and encephalitis matched on the residence area, age and sex. The JE vaccination history was enquired from parents and verified independently from the vaccination cards available at home and records at health facilities. We enrolled 35 JE cases and 70 matched controls. The vaccination effectiveness of 86.7% (95% confidence interval [CI]: 30.8-94.7) was estimated on the per-protocol analysis of 31 case-control sets. The screening method provided an effectiveness of 89.5% (CI: 78.9-94.7) on using the population vaccination coverage of 90% reported earlier in the same area. In conclusion, JE vaccination offered a moderate level of protection among children in JE medium-endemic central India, similar to reports from high-endemic areas in India. The operational aspects of vaccination program implementation need to be evaluated to assess the impact of vaccination on the disease burden of JE in medium-endemic regions of India.

Boosting of stable synchronization in coupled non-identical counter-rotating chaotic systems.

Achieving synchronization in coupled non-identical chaotic systems has been a difficult endeavor, and improving the stability of synchronization in such systems poses additional challenges. This research work addresses these challenges by identifying stable synchronization in coupled non-identical chaotic systems and enhancing its stability. The study explores chaotic attractors that arise from various system parameters to provide generalized results. Furthermore, the impact of the transient uncoupling factor on improving synchronization stability in coupled non-identical counter-rotating chaotic oscillators is discussed. By investigating these aspects, the research aims to contribute to the understanding and advancement of synchronization in coupled non-identical chaotic systems.

Methylammonium Tetrel Halide Perovskite Ion Pairs and Their Dimers: The Interplay between the Hydrogen-, Pnictogen- and Tetrel-Bonding Interactions.

The structural stability of the extensively studied organic-inorganic hybrid methylammonium tetrel halide perovskite semiconductors, MATtX3 (MA = CH3NH3+; Tt = Ge, Sn, Pb; X = Cl, Br, I), arises as a result of non-covalent interactions between an organic cation (CH3NH3+) and an inorganic anion (TtX3-). However, the basic understanding of the underlying chemical bonding interactions in these systems that link the ionic moieties together in complex configurations is still limited. In this study, ion pair models constituting the organic and inorganic ions were regarded as the repeating units of periodic crystal systems and density functional theory simulations were performed to elucidate the nature of the non-covalent interactions between them. It is demonstrated that not only the charge-assisted N-H···X and C-H···X hydrogen bonds but also the C-N···X pnictogen bonds interact to stabilize the ion pairs and to define their geometries in the gas phase. Similar interactions are also responsible for the formation of crystalline MATtX3 in the low-temperature phase, some of which have been delineated in previous studies. In contrast, the Tt···X tetrel bonding interactions, which are hidden as coordinate bonds in the crystals, play a vital role in holding the inorganic anionic moieties (TtX3-) together. We have demonstrated that each Tt in each [CH3NH3+•TtX3-] ion pair has the capacity to donate three tetrel (σ-hole) bonds to the halides of three nearest neighbor TtX3- units, thus causing the emergence of an infinite array of 3D TtX64- octahedra in the crystalline phase. The TtX44- octahedra are corner-shared to form cage-like inorganic frameworks that host the organic cation, leading to the formation of functional tetrel halide perovskite materials that have outstanding optoelectronic properties in the solid state. We harnessed the results using the quantum theory of atoms in molecules, natural bond orbital, molecular electrostatic surface potential and independent gradient models to validate these conclusions.

The Tetrel Bond and Tetrel Halide Perovskite Semiconductors.

The ion pairs [Cs+•TtX3-] (Tt = Pb, Sn, Ge; X = I, Br, Cl) are the building blocks of all-inorganic cesium tetrel halide perovskites in 3D, CsTtX3, that are widely regarded as blockbuster materials for optoelectronic applications such as in solar cells. The 3D structures consist of an anionic inorganic tetrel halide framework stabilized by the cesium cations (Cs+). We use computational methods to show that the geometrical connectivity between the inorganic monoanions, [TtX3-]∞, that leads to the formation of the TtX64- octahedra and the 3D inorganic perovskite architecture is the result of the joint effect of polarization and coulombic forces driven by alkali and tetrel bonds. Depending on the nature and temperature phase of these perovskite systems, the Tt···X tetrel bonds are either indistinguishable or somehow distinguishable from Tt-X coordinate bonds. The calculation of the potential on the electrostatic surface of the Tt atom in molecular [Cs+•TtX3-] provides physical insight into why the negative anions [TtX3-] attract each other when in close proximity, leading to the formation of the CsTtX3 tetrel halide perovskites in the solid state. The inter-molecular (and inter-ionic) geometries, binding energies, and charge density-based topological properties of sixteen [Cs+•TtX3-] ion pairs, as well as some selected oligomers [Cs+•PbI3-]n (n = 2, 3, 4), are discussed.

Machine learning in the detection of dental cyst, tumor, and abscess lesions.

BACKGROUND AND OBJECTIVE: Dental panoramic radiographs are utilized in computer-aided image analysis, which detects abnormal tissue masses by analyzing the produced image capacity to recognize patterns of intensity fluctuations. This is done to reduce the need for invasive biopsies for arriving to a diagnosis. The aim of the current study was to examine and compare the accuracy of several texture analysis techniques, such as Grey Level Run Length Matrix (GLRLM), Grey Level Co-occurrence Matrix (GLCM), and wavelet analysis in recognizing dental cyst, tumor, and abscess lesions. MATERIALS & METHODS: The current retrospective study retrieved a total of 172 dental panoramic radiographs with lesion including dental cysts, tumors, or abscess. Radiographs that failed to meet technical criteria for diagnostic quality (such as significant overlap of teeth, a diffuse image, or distortion) were excluded from the sample. The methodology adopted in the study comprised of five stages. At first, the radiographs are improved, and the area of interest was segmented manually. A variety of feature extraction techniques, such GLCM, GLRLM, and the wavelet analysis were used to gather information from the area of interest. Later, the lesions were classified as a cyst, tumor, abscess, or using a support vector machine (SVM) classifier. Eventually, the data was transferred into a Microsoft Excel spreadsheet and statistical package for social sciences (SPSS) (version 21) was used to conduct the statistical analysis. Initially descriptive statistics were computed. For inferential analysis, statistical significance was determined by a p value < 0.05. The sensitivity, specificity, and accuracy were used to find the significant difference between assessed and actual diagnosis. RESULTS: The findings demonstrate that 98% accuracy was achieved using GLCM, 91% accuracy using Wavelet analysis & 95% accuracy using GLRLM in distinguishing between dental cyst, tumor, and abscess lesions. The area under curve (AUC) number indicates that GLCM achieves a high degree of accuracy. The results achieved excellent accuracy (98%) using GLCM. CONCLUSION: The GLCM features can be used for further research. After improving the performance and training, it can support routine histological diagnosis and can assist the clinicians in arriving at accurate and spontaneous treatment plans.

Coverage of Japanese encephalitis routine vaccination among children in Central India.

BACKGROUND: We aimed to estimate the coverage of Japanese encephalitis (JE) vaccination in central India to help explain the continued occurrence of JE disease despite routine vaccination. METHODS: We implemented a 30-cluster survey for estimating the coverage of JE vaccination in the medium-endemic areas implemented with JE vaccination in central India. The parents were enquired about the uptake of the JE vaccine by their children aged 2 to 6 years, followed by verification of the immunization cards at home along with reasons for non-vaccination. Vaccination coverage was reported as a percentage with 95% confidence intervals. RESULTS: We estimated high coverage of live-attenuated SA 14-14-2 JE vaccination in Maharashtra (94.8%, 95% CI 92.7-96.3) and Telangana (92.8%, 90.0-94.9). The vaccination card retention was 90.3% in Maharashtra and 70.4% in Telangana state. There were no gender differences in coverage in both states. A similar level of JE vaccination coverage was observed during the year 2013 to 2021 in both states. In Maharashtra, the maximum age-wise coverage was 96.6% in the >60 months age category, whereas in Telangana it was in the <24 months age category (97.2%). The timeliness of JE vaccination was appropriate and similar in both states. We found very good agreement between JE and Measles-Rubella vaccinations administered simultaneously. The reasons for non-vaccination were the shortage of vaccines and the parental migration for work. CONCLUSIONS: The coverage of Japanese encephalitis vaccination was high in medium-endemic regions in central India. Vaccination effectiveness studies may help further explain the continued incidence of Japanese encephalitis. This article is protected by copyright. All rights reserved.

Collaborative care compared to enhanced standard treatment of depression with co-morbid medical conditions among patients from rural South India: a cluster randomized controlled trial (HOPE Study).

BACKGROUND: Depression is common among primary care patients in LMIC but treatments are largely ineffective. In this cluster-randomized controlled trial, we tested whether depression outcomes are different among recipients of a collaborative care model compared to enhanced standard treatment in patients with co-morbid chronic medical conditions. METHODS: We conducted a cluster randomized controlled trial among participants 30 years or older seeking care at 49 primary health centers (PHCs) in rural Karnataka, diagnosed with major depressive disorder, dysthymia, generalized anxiety disorder, or panic disorder on the MINI-International Neuropsychiatric Interview plus either hypertension, diabetes, or ischemic heart disease. From a list of all PHCs in the district, 24 PHCs were randomized a priori to deliver collaborative care and 25 PHCs enhanced standard treatment. The collaborative care model consisted of a clinic-based and a community-based component. Study assessment staff was blinded to treatment arm allocation. The primary outcome was the individual-level PHQ-9 score over time. RESULTS: Between May 2015 and Nov 2018, 2486 participants were enrolled, 1264 in the control arm, and 1222 in the intervention arm. They were assessed at baseline, 3, 6 and 12 months. The mean PHQ-9 depression score was around 8.5 at baseline. At each follow-up PHQ-9 scores were significantly lower in the intervention (5.24, 4.81 and 4.22 at respective follow-ups) than in the control group (6.69, 6.13, 5.23, respectively). A significant time-by-treatment interaction (p < 0.001) in a multi-level model over all waves, nested within individuals who were nested within PHCs, confirmed that the decrease in depression score from baseline was larger for collaborative care than enhanced standard care throughout follow-up. CONCLUSIONS: The collaborative care intervention resulted in significantly lower depression scores compared to enhanced standard care among participants with co-morbid physical conditions. The findings have potential implications for integrating mental health and chronic disease treatment in resource constrained settings. TRIAL REGISTRATION: ClinicalTrials.gov NCT02310932 , registered on December 8, 2014, and Clinical Trials Registry India CTRI/2018/04/013001 , registered on April 4, 2018. Retrospectively registered.

Impact of Covid-19 on gastrointestinal cancer surgery: A National Survey.

PURPOSE: To understand the actual impact of the Covid-19 pandemic and frame the future strategies, we conducted a pan India survey to study the impact on the surgical management of gastrointestinal cancers. METHODS: A national multicentre survey in the form of a questionnaire from 16 tertiary care gastrointestinal oncology centres across India was conducted from January 2019 to June 2021 that was divided into a 15-month pre-Covid era and a similar period of active Covid pandemic era. RESULTS: There was significant disruption of services; 13 (81%) centres worked as dedicated Covid care centres and 43% reported suspension of essential care for more than 6 months. In active Covid phase, there was a 14.5% decrease in registrations and proportion of decrease was highest in the centres from South zone (22%). There was decrease in resections across all organ systems; maximum reduction was noted in hepatic resections (33%) followed by oesophageal and gastric resections (31 and 25% respectively). There was minimal decrease in colorectal resections (5%). A total of 584 (7.1%) patients had either active Covid-19 infection or developed infection in the post-operative period or had recovered from Covid-19 infection. Only 3 (18%) centres reported higher morbidity, while the rest of the centres reported similar or lower morbidity rates when compared to pre-Covid phase; however, 6 (37%) centres reported slightly higher mortality in the active Covid phase. CONCLUSION: Covid-19 pandemic resulted in significant reduction in new cancer registrations and elective gastrointestinal cancer surgeries. Perioperative morbidity remained similar despite 7.1% perioperative Covid 19 exposure.

The Stibium Bond or the Antimony-Centered Pnictogen Bond: The Covalently Bound Antimony Atom in Molecular Entities in Crystal Lattices as a Pnictogen Bond Donor.

A stibium bond, i.e., a non-covalent interaction formed by covalently or coordinately bound antimony, occurs in chemical systems when there is evidence of a net attractive interaction between the electrophilic region associated with an antimony atom and a nucleophile in another, or the same molecular entity. This is a pnictogen bond and are likely formed by the elements of the pnictogen family, Group 15, of the periodic table, and is an inter- or intra-molecular non-covalent interaction. This overview describes a set of illustrative crystal systems that were stabilized (at least partially) by means of stibium bonds, together with other non-covalent interactions (such as hydrogen bonds and halogen bonds), retrieved from either the Cambridge Structure Database (CSD) or the Inorganic Crystal Structure Database (ICSD). We demonstrate that these databases contain hundreds of crystal structures of various dimensions in which covalently or coordinately bound antimony atoms in molecular entities feature positive sites that productively interact with various Lewis bases containing O, N, F, Cl, Br, and I atoms in the same or different molecular entities, leading to the formation of stibium bonds, and hence, being partially responsible for the stability of the crystals. The geometric features, pro-molecular charge density isosurface topologies, and extrema of the molecular electrostatic potential model were collectively examined in some instances to illustrate the presence of Sb-centered pnictogen bonding in the representative crystal systems considered.

Chalcogen Bonding in the Molecular Dimers of WCh2 (Ch = S, Se, Te): On the Basic Understanding of the Local Interfacial and Interlayer Bonding Environment in 2D Layered Tungsten Dichalcogenides.

Layered two-dimensional transition metal dichalcogenides and their heterostructures are of current interest, owing to the diversity of their applications in many areas of materials nanoscience and technologies. With this in mind, we have examined the three molecular dimers of the tungsten dichalcogenide series, (WCh2)2 (Ch = S, Se, Te), using density functional theory to provide insight into which interactions, and their specific characteristics, are responsible for the interfacial/interlayer region in the room temperature 2H phase of WCh2 crystals. Our calculations at various levels of theory suggested that the Te···Te chalcogen bonding in (WTe2)2 is weak, whereas the Se···Se and S···S bonding interactions in (WSe2)2 and (WS2)2, respectively, are of the van der Waals type. The presence and character of Ch···Ch chalcogen bonding interactions in the dimers of (WCh2)2 are examined with a number of theoretical approaches and discussed, including charge-density-based approaches, such as the quantum theory of atoms in molecules, interaction region indicator, independent gradient model, and reduced density gradient non-covalent index approaches. The charge-density-based topological features are shown to be concordant with the results that originate from the extrema of potential on the electrostatic surfaces of WCh2 monomers. A natural bond orbital analysis has enabled us to suggest a number of weak hyperconjugative charge transfer interactions between the interacting monomers that are responsible for the geometry of the (WCh2)2 dimers at equilibrium. In addition to other features, we demonstrate that there is no so-called van der Waals gap between the monolayers in two-dimensional layered transition metal tungsten dichalcogenides, which are gapless, and that the (WCh2)2 dimers may be prototypes for a basic understanding of the physical chemistry of the chemical bonding environments associated with the local interfacial/interlayer regions in layered 2H-WCh2 nanoscale systems.

The Pnictogen Bond, Together with Other Non-Covalent Interactions, in the Rational Design of One-, Two- and Three-Dimensional Organic-Inorganic Hybrid Metal Halide Perovskite Semiconducting Materials, and Beyond.

The pnictogen bond, a somewhat overlooked supramolecular chemical synthon known since the middle of the last century, is one of the promising types of non-covalent interactions yet to be fully understood by recognizing and exploiting its properties for the rational design of novel functional materials. Its bonding modes, energy profiles, vibrational structures and charge density topologies, among others, have yet to be comprehensively delineated, both theoretically and experimentally. In this overview, attention is largely centered on the nature of nitrogen-centered pnictogen bonds found in organic-inorganic hybrid metal halide perovskites and closely related structures deposited in the Cambridge Structural Database (CSD) and the Inorganic Chemistry Structural Database (ICSD). Focusing on well-characterized structures, it is shown that it is not merely charge-assisted hydrogen bonds that stabilize the inorganic frameworks, as widely assumed and well-documented, but simultaneously nitrogen-centered pnictogen bonding, and, depending on the atomic constituents of the organic cation, other non-covalent interactions such as halogen bonding and/or tetrel bonding, are also contributors to the stabilizing of a variety of materials in the solid state. We have shown that competition between pnictogen bonding and other interactions plays an important role in determining the tilting of the MX6 (X = a halogen) octahedra of metal halide perovskites in one, two and three-dimensions. The pnictogen interactions are identified to be directional even in zero-dimensional crystals, a structural feature in many engineered ordered materials; hence an interplay between them and other non-covalent interactions drives the structure and the functional properties of perovskite materials and enabling their application in, for example, photovoltaics and optoelectronics. We have demonstrated that nitrogen in ammonium and its derivatives in many chemical systems acts as a pnictogen bond donor and contributes to conferring stability, and hence functionality, to crystalline perovskite systems. The significance of these non-covalent interactions should not be overlooked, especially when the focus is centered on the rationale design and discovery of such highly-valued materials.

Tetrel Bonding in Anion Recognition: A First Principles Investigation.

Twenty-five molecule-anion complex systems [I4Tt···X-] (Tt = C, Si, Ge, Sn and Pb; X = F, Cl, Br, I and At) were examined using density functional theory (ωB97X-D) and ab initio (MP2 and CCSD) methods to demonstrate the ability of the tetrel atoms in molecular entities, I4Tt, to recognize the halide anions when in close proximity. The tetrel bond strength for the [I4C···X-] series and [I4Tt···X-] (Tt = Si, Sn; X = I, At), was weak-to-moderate, whereas that in the remaining 16 complexes was dative tetrel bond type with very large interaction energies and short Tt···X close contact distances. The basis set superposition error corrected interaction energies calculated with the highest-level theory applied, [CCSD(T)/def2-TZVPPD], ranged from -3.0 to -112.2 kcal mol-1. The significant variation in interaction energies was realized as a result of different levels of tetrel bonding environment between the interacting partners at the equilibrium geometries of the complex systems. Although the ωB97X-D computed intermolecular geometries and interaction energies of a majority of the [I4Tt···X-] complexes were close to those predicted by the highest level of theory, the MP2 results were shown to be misleading for some of these systems. To provide insight into the nature of the intermolecular chemical bonding environment in the 25 molecule-anion complexes investigated, we discussed the charge-density-based topological and isosurface features that emanated from the application of the quantum theory of atoms in molecules and independent gradient model approaches, respectively.

The Pnictogen Bond: The Covalently Bound Arsenic Atom in Molecular Entities in Crystals as a Pnictogen Bond Donor.

In chemical systems, the arsenic-centered pnictogen bond, or simply the arsenic bond, occurs when there is evidence of a net attractive interaction between the electrophilic region associated with a covalently or coordinately bound arsenic atom in a molecular entity and a nucleophile in another or the same molecular entity. It is the third member of the family of pnictogen bonds formed by the third atom of the pnictogen family, Group 15 of the periodic table, and is an inter- or intramolecular noncovalent interaction. In this overview, we present several illustrative crystal structures deposited into the Cambridge Structure Database (CSD) and the Inorganic Chemistry Structural Database (ICSD) during the last and current centuries to demonstrate that the arsenic atom in molecular entities has a significant ability to act as an electrophilic agent to make an attractive engagement with nucleophiles when in close vicinity, thereby forming σ-hole or π-hole interactions, and hence driving (in part, at least) the overall stability of the system's crystalline phase. This overview does not include results from theoretical simulations reported by others as none of them address the signatory details of As-centered pnictogen bonds. Rather, we aimed at highlighting the interaction modes of arsenic-centered σ- and π-holes in the rationale design of crystal lattices to demonstrate that such interactions are abundant in crystalline materials, but care has to be taken to identify them as is usually done with the much more widely known noncovalent interactions in chemical systems, halogen bonding and hydrogen bonding. We also demonstrate that As-centered pnictogen bonds are usually accompanied by other primary and secondary interactions, which reinforce their occurrence and strength in most of the crystal structures illustrated. A statistical analysis of structures deposited into the CSD was performed for each interaction type As···D (D = N, O, S, Se, Te, F, Cl, Br, I, arene's π system), thus providing insight into the typical nature of As···D interaction distances and ∠R-As···D bond angles of these interactions in crystals, where R is the remainder of the molecular entity.

The Phosphorus Bond, or the Phosphorus-Centered Pnictogen Bond: The Covalently Bound Phosphorus Atom in Molecular Entities and Crystals as a Pnictogen Bond Donor.

The phosphorus bond in chemical systems, which is an inter- or intramolecular noncovalent interaction, occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a covalently or coordinately bonded phosphorus atom in a molecular entity and a nucleophile in another, or the same, molecular entity. It is the second member of the family of pnictogen bonds, formed by the second member of the pnictogen family of the periodic table. In this overview, we provide the reader with a snapshot of the nature, and possible occurrences, of phosphorus-centered pnictogen bonding in illustrative chemical crystal systems drawn from the ICSD (Inorganic Crystal Structure Database) and CSD (Cambridge Structural Database) databases, some of which date back to the latter part of the last century. The illustrative systems discussed are expected to assist as a guide to researchers in rationalizing phosphorus-centered pnictogen bonding in the rational design of molecular complexes, crystals, and materials and their subsequent characterization.

Pickering Dry Emulsion System for Improved Oral Delivery of Fenofibrate.

The current study reports a Pickering dry emulsion (PDE) system for improved oral delivery of fenofibrate, a poorly water-soluble model drug. The silica nanoparticles were modified by surface modifiers and explored as a stabilizer for emulsion. The wetting property of modified silica nanoparticles was evaluated by contact angle study. Emulsion was spray-dried to obtain PDE. PDE was evaluated for particle size analysis, drug loading, TGA, DSC, XRPD, FEG-SEM, in vitro dissolution study, and in vivo pharmacodynamic study. The particle size of liquid emulsion was found within the range of 0.3-0.6 µm; after spray drying, the particles agglomerated and exhibited an increase in particle size (1.5 µm). The high drug loading (13% w/w) was found in PDE. DSC and XRD study confirmed the amorphous form of fenofibrate. SEM study showed the formation of a spherical porous microcapsule structure. In vitro dissolution exhibited significant enhancement in drug release for the PDE system as compared to plain fenofibrate. The PDE significantly lowered serum lipid level as compared to plain fenofibrate in a Triton-based hypercholesterolemia model in rats, which ultimately confirmed the enhancement in bioavailability. Thus, the PDE system has good potential in the drug delivery area.

Design and Development of Gastro-retentive Drug Delivery System for Trazodone Hydrochloride: a Promising Alternative to Innovator's Controlled-Release Tablet.

Trazodone hydrochloride (TZN) is a serotonin reuptake inhibitor that treats a major depressive disorder. It exhibits a short plasma half-life of 4.1 h and shows pH-dependent solubility. Above its pKa (6.74), solubility of TZN is very low, affecting its dissolution in the lower part of GIT. Hence, the present work aimed to develop gastro-retentive floating tablet of TZN. Central composite design was employed to optimize the formulation. Formulation variables like the concentration of HPMC-K100M, Polyox WSR 303 Leo, and sodium bicarbonate were evaluated for the responses like floating lag time and drug release. X-ray imaging study was performed on rabbits to determine the in vivo gastric retention of the optimized formulation. The accelerated stability study was conducted on optimized tablets as per ICH guidelines. Floating lag time and f2 value of the optimized formulation were found to be 2.51±0.02 min and 62.79, respectively. X-ray imaging studies in rabbits determined the in vivo gastro retention time. After 12 h of administration, tablet remained in the gastric region, indicating better retentive power. Accelerated stability studies showed sufficient formulation stability even after 3 months of storage. All these studies depict that the floating gastro-retentive system could be used as an alternative to the innovator formulation.