Interplay of Tetrel, Hydrogen, and Halogen Bonds in FGeOCl and HCN Complexes: A Comprehensive Theoretical Study of Dimers, Trimers, and Tetramers.

This study investigates the nature and interplay of noncovalent interactions (NCIs)─tetrel bonds (TB), hydrogen bonds (HB), and halogen bonds (XB)─in molecular assemblies formed between trifluorogermyl hypochlorite (FGeOCl) and hydrogen cyanide (HCN). Using a combination of high-level computational methods, we explored the geometric, energetic, and electronic properties of dimers, trimers, and tetramers formed in different molar ratios of interacting reagents. Various analyses reveal a significant cooperativity between TB and HB, which mutually reinforce each other, while XB interactions are diminished in the presence of TB and HB.

Synthesis of tetrazoles through a domino reaction: A molecular electron density theory study of energetics, selectivities, and molecular mechanistic aspects.

This study corresponds to a molecular electron density theory (MEDT) investigation to shed light on the energetics, selectivities, and molecular mechanistic aspects of an experimental domino reaction. Theoretical evidences at the M06-2X/6-31G(d) level indicates that this domino reaction includes three different successive steps and is initialized by a stepwise HCl elimination from precursor chlorohydrazone NPCH to yield nitrile imine NI-2. A subsequent stepwise and highly regioselective [3 + 2] cycloaddition (32CA) reaction of NI-2 toward tetramethylguanidine TMG-3 affords corresponding formal [3 + 2] cycloadduct CA-1 as the sole product.

X-ray Emission Spectroscopy of Single Protein Crystals Yields Insights into Heme Enzyme Intermediates.

Enzyme reactivity is often enhanced by changes in oxidation state, spin state, and metal-ligand covalency of associated metallocofactors. The development of spectroscopic methods for studying these processes coincidentally with structural rearrangements is essential for elucidating metalloenzyme mechanisms. Herein, we demonstrate the feasibility of collecting X-ray emission spectra of metalloenzyme crystals at a third-generation synchrotron source.

A molecular electron density theory study on the Chichibabin reaction: The origin of regioselectivity.

A Molecular Electron Density Theory (MEDT) study was performed on the nucleophilic amination of pyridine and benzene to elucidate the observed regioselectivity in the Chichibabin reaction. For this purpose, three possible reaction paths were considered between NaNH and the 2-, 3- and 4-positions of pyridine. The reaction of NaNH and benzene was also investigated.

Intelligent modeling and optimization of titanium surface etching for dental implant application.

Acid-etching is one of the most popular processes for the surface treatment of dental implants. In this paper, acid-etching of commercially pure titanium (cpTi) in a 48% HSO solution is investigated. The etching process time (0-8 h) and solution temperature (25-90 °C) are assumed to be the most effective operational conditions to affect the surface roughness parameters such as arithmetical mean deviation of the assessed profile on the surface (R) and average of maximum peak to valley height of the surface over considered length profile (R), as well as weight loss (WL) of the dental implants in etching process.

On Pause: How a Group of Medical Students Engaged with Their Community During the COVID-19 Pandemic.

During academic clinical suspensions related to the COVID-19 pandemic, a group of medical students in Washington, D.C. collaborated with a local federally qualified health center to launch a free COVID-19 testing site to increase access to testing in the community.

Exploring Nature and Predicting Strength of Hydrogen Bonds: A Correlation Analysis Between Atoms-in-Molecules Descriptors, Binding Energies, and Energy Components of Symmetry-Adapted Perturbation Theory.

This work studies the underlying nature of H-bonds (HBs) of different types and strengths and tries to predict binding energies (BEs) based on the properties derived from wave function analysis. A total of 42 HB complexes constructed from 28 neutral and 14 charged monomers were considered. This set was designed to sample a wide range of HB strengths to obtain a complete view about HBs.

Spinal blastomycosis: unusual musculoskeletal presentation with literature review.

We report a case of a 41-year-old male who presented to our institution with a large groin mass. CT, MRI and PET imaging was performed and was concerning for a soft tissue abscess likely originating in the lumbar spine. Differential considerations included infection, with atypical infections such as tuberculosis strongly considered.

Understanding the molecular mechanism and regioselectivity in the synthesis of celecoxib via a domino reaction: A DFT study.

The molecular mechanism and energetic of the domino reaction involved in the synthesis of celecoxib, a well-known anti-inflammatory drug, were theoretically studied at the DFT-B3LYP/6-31G(*) level. The first reaction in this domino process, which is also the rate-determining step, is a complete regioselective [3+2] cycloaddition (32CA) reaction associated with the nucleophilic attack of C5 carbon atom of enamine 7 on the C3 carbon atom of nitrile imine 6, leading to cycloadduct 8. The second reaction is a rapid acid/base catalysed stepwise elimination reaction of the morpholine 9 from cycloadduct 8 affording celecoxibe 3.

Understanding the domino reaction between 3-chloroindoles and methyl coumalate yielding carbazoles. A DFT study.

The molecular mechanism of the reaction between N-methyl-3-chloroindole and methyl coumalate yielding carbazole has been studied using DFT methods at the MPWB1K/6-311G(d,p) level in toluene. This reaction is a domino process that comprises three consecutive reactions: (i) a polar Diels-Alder (P-DA) reaction between indole and methyl coumalate yielding two stereoisomeric [2 + 4] cycloadducts (CAs); (ii) the elimination of HCl from these CAs affording two stereoisomeric intermediates; and (iii) the extrusion of CO2 in these intermediates, finally yielding the carbazole. This P-DA reaction proceeds in a completely regioselective and slightly exo selective fashion.

Tautomerism in pyridazin-3(2H)-one: a theoretical study using implicit/explicit solvation models.

The tautomeric conversion of pyridazin-3(2H)-one 1 into pyridazin-3-ol 2 has been theoretically studied using density functional theory (DFT) methods at the B3LYP/6-311++G** level. Two mechanisms have been considered for this process: (i) one in which the hydrogen is directly transferred through TS12; and (ii) another one in which a double hydrogen transfer takes place via TS1122 upon formation of the corresponding dimer. The former requires a very high activation energy of 42.

Learning impairment caused by intra-CA1 microinjection of testosterone increases the number of astrocytes.

The hippocampus is essentially involved in learning and memory, and is known to be a target for androgen actions. As neuron-astrocyte interactions play a crucial role during development and in the adult brain, it is thought that astrocytes support learning and memory through specific mechanisms. In this study, the effect of testosterone-induced impairment of acquisition and retrieval of long-term memory, on the number of astrocytes was studied.

Head & neck vascular and cystic lesions of infancy and early childhood: challenges in diagnosis and management--update.

A variety of vascular and cystic lesions exist in the head and neck area of infants and little children. The mode of evaluating these entities is evolving and new treatment modalities are added now and then. An updated knowledge of these lesions and their management is crucial to provide the best care for these patients.

CT scout films: don't forget to look!

Background: A lateral scout view of the head is always obtained when performing head computed tomography (CT). It is common knowledge that viewing the lateral scout view may provide additional information. For a variety of reasons, however, a careful review may not be performed routinely.

Congenital middle ear cholesteatoma: need for early recognition--role of computed tomography scan.

Background: Congenital cholesteatoma (CC) of middle ear is a rare entity that may go undiagnosed for years. Patients with CC who are diagnosed at a later stage of disease have poor outcome. There is controversy regarding the best way to delineate CC preoperatively.

Fetal MRI evaluation of an intracranial mass: in utero evolution of hemorrhage.

The role of MRI in the evaluation of fetal abnormalities is still under evaluation. We describe a case of an intracranial mass that was initially identified by prenatal ultrasound and was further evaluated by MRI. Ultimately, the findings were most consistent with hematoma secondary to an underlying dural malformation with spontaneous involution.

The spectrum of heterotopic gastric mucosa in children detected by Tc-99m pertechnetate scintigraphy.

Meckel's diverticulum is the most common site of heterotopic gastric mucosa (HGM). Other sites include intestinal duplication and the small bowel proper. Tc-99m pertechnetate abdominal scintigraphy is used commonly to detect HGM.

Significant association between simple renal cysts and arterial blood pressure.

Objective: To test the hypothesis that there is an association between simple renal cysts and arterial blood pressure (BP).

Patients And Methods: The study comprised a review of the case-notes of 115 patients (mean age 67.7 years, range 31-91) in whom renal cyst(s) was an incidental ultrasonographic finding, and 115 age- and sex-matched control patients.

Accuracy of the diagnosis of pleural effusion on supine chest X-ray.

Diagnosis of pleural effusion (PE) on supine chest X-ray (SCXR) is considered difficult. This study aimed at evaluating the accuracy of the diagnosis of PE on SCXR and was performed in two phases. At phase 1, a formula for the sonographic estimation of the volume of PE was established by correlating 24 measurements (in 7 patients in whom complete drainage was achieved) with the drained volumes.

Can dipstick screening for hematuria identify individuals with structural renal abnormalities? A sonographic evaluation.

The present study presents data from a population study of 659 randomly selected adult volunteers. All participants had a renal sonographic examination and at the same time had their urine tested for hematuria by dipstick. Thirty participants (5%) had dipstick hematuria.

Intraobserver and interobserver variations in sonographic measurements of kidney size in adult volunteers. A comparison of linear measurements and volumetric estimates.

Estimation of renal size by sonography can be performed by measuring renal length, volume, cortical volume or cortical thickness. Observer variation in these measurements is an important factor, especially when repeated measurements are compared. This study was performed to examine the magnitude of intraobserver and interobserver variations for each of the above-mentioned measurements, and to find the measurement with the lowest observer variation.

Sonographic evaluation of renal appearance in 665 adult volunteers. Correlation with age and obesity.

The purpose of this study was to investigate the sonographic appearance of the normal adult kidney. Parenchymal echogenicity, pyramid visibility, and transverse pelvis diameter of the kidneys were prospectively determined in an age- and sex-stratified random sample of 665 volunteers 30, 40, 50, 60, and 70 years old. Furthermore, incidences of kidney stones and split sinus echo were determined.

Simple renal cyst: relations to age and arterial blood pressure.

Simple renal cysts are increasingly common with increasing age, as is elevated arterial blood pressure. We studied the natural history of simple renal cysts, and their possible association with arterial hypertension. Renal sonography was performed in an age- and sex-stratified random sample of 686 healthy volunteers aged 30-70 years.