Computational infrared and Raman spectra by hybrid QM/MM techniques: a study on molecular and catalytic material systems.

Vibrational spectroscopy is one of the most well-established and important techniques for characterizing chemical systems. To aid the interpretation of experimental infrared and Raman spectra, we report on recent theoretical developments in the ChemShell computational chemistry environment for modelling vibrational signatures. The hybrid quantum mechanical and molecular mechanical approach is employed, using density functional theory for the electronic structure calculations and classical forcefields for the environment. Computational vibrational intensities at chemical active sites are reported using electrostatic and fully polarizable embedding environments to achieve more realistic vibrational signatures for materials and molecular systems, including solvated molecules, proteins, zeolites and metal oxide surfaces, providing useful insight into the effect of the chemical environment on the signatures obtained from experiment. This work has been enabled by the efficient task-farming parallelism implemented in ChemShell for high-performance computing platforms.  This article is part of a discussion meeting issue 'Supercomputing simulations of advanced materials'.

Gastroparesis-Related Symptoms in Patients With Type 2 Diabetes Mellitus: Early Detection, Risk Factors, and Prevalence.

Background The symptoms of gastroparesis, such as bloating, postprandial fullness, early satiety, nausea, and abdominal discomfort, progressively worsen the quality of life of the affected individuals. The diagnosis is established on the assessment of gastric function that confirms delayed gastric emptying in the absence of structural etiologies. This study aimed to detect gastroparesis-related clinical symptoms early in patients with type 2 diabetes mellitus (T2DM), investigate the concomitant risk factors, and evaluate the prevalence. Methodology This study was conducted at the Department of Medicine and Diabetes Outdoor Clinic of Sheikh Zayed Hospital, Rahim Yar Khan from February 13, 2022, to February 11, 2023. The study involved 175 patients with T2DM who reported gastroparesis-related symptoms. The demographic and clinical characteristics, symptom severity, complications, related risk factors, duration of disease, medications, body mass index (BMI), fasting plasma glucose, and glycated hemoglobin (HbA1C) levels were assessed. The severity of diabetic gastroparesis was established using the disease-specific Patient Assessment of Gastrointestinal Disorders-Symptom Severity Index (PAGI-SYM) and the Gastroparesis Cardinal Symptom Index (GCSI). The five-point scale of the PAGI-SYM and the four-degree severity scores of GCSI were assessed. Neuropathy disability scores and motor evacuation functions were analyzed. Data were analyzed from these questionnaires, special proforma, and patient interviews. Results The clinical features of diabetic gastroparesis were observed in 44% of T2DM patients with mild-grade gastroparesis in 38 (21.7%), moderate in 30 (17.1%), and severe-grade gastroparesis-related symptoms in nine (5.2%) patients. The main manifestations were early satiety (45.1%), stomach fullness (44.5%), bloating (38.3%), and nausea (33.1%). Diabetic gastroparesis symptoms were considerably linked to disease duration of more than 10 years (p = 0.02), high HbA1c (p = 0.001), increased fasting blood glucose (p = 0.003), polyneuropathy, cigarette smoking, and history of comorbid conditions (p = 0.009). Obesity and the female gender were the forecasters of the manifestation of at least one cardinal gastroparesis symptom. Conclusions Gastric emptying is significant in the pathogenesis of gastroparesis-related symptoms. Disease duration of more than 10 years, poor glycemic control with hyperglycemia, high HbA1C, polyneuropathy, and cigarette smoking must be considered as predictors for early detection and risk factors for the advancement of gastroparesis in T2DM. Gastroparesis-related common symptoms of early satiety, bloating, and stomach fullness were considerably linked to the additional risk factors of hypercholesteremia, chronic microvascular complications, concomitant cardiovascular diseases, and a positive family history of diabetes mellitus. There was no relationship between BMI, age, types of treatment, and the degree of gastroparesis severity. The prevalence and severity of gastroparesis symptoms were particularly high among obese females with poor glycemic control and longer disease duration.

Multiscale QM/MM modelling of catalytic systems with ChemShell.

Hybrid quantum mechanical/molecular mechanical (QM/MM) methods are a powerful computational tool for the investigation of all forms of catalysis, as they allow for an accurate description of reactions occurring at catalytic sites in the context of a complicated electrostatic environment. The scriptable computational chemistry environment ChemShell is a leading software package for QM/MM calculations, providing a flexible, high performance framework for modelling both biomolecular and materials catalysis. We present an overview of recent applications of ChemShell to problems in catalysis and review new functionality introduced into the redeveloped Python-based version of ChemShell to support catalytic modelling. These include a fully guided workflow for biomolecular QM/MM modelling, starting from an experimental structure, a periodic QM/MM embedding scheme to support modelling of metallic materials, and a comprehensive set of tutorials for biomolecular and materials modelling.

Influence of Solvent on Selective Catalytic Reduction of Nitrogen Oxides with Ammonia over Cu-CHA Zeolite.

The copper-exchanged zeolite Cu-CHA has received considerable attention in recent years, owing to its application in the selective catalytic reduction (SCR) of NOx species. Here, we study the NH3-SCR reaction mechanism on Cu-CHA using the hybrid quantum mechanical/molecular mechanical (QM/MM) technique and investigate the effects of solvent on the reactivity of active Cu species. To this end, a comparison is made between water- and ammonia-solvated and bare Cu species. The results show the promoting effect of solvent on the oxidation component of the NH3-SCR cycle since the formation of important nitrate species is found to be energetically more favorable on the solvated Cu sites than in the absence of solvent molecules. Conversely, both solvent molecules are predicted to inhibit the reduction component of the NH3-SCR cycle. Diffuse reflectance infrared fourier-transform spectroscopy (DRIFTS) experiments exploiting (concentration) modulation excitation spectroscopy (MES) and phase-sensitive detection (PSD) identified spectroscopic signatures of Cu-nitrate and Cu-nitrosamine (H2NNO), important species which had not been previously observed experimentally. This is further supported by the QM/MM-calculated harmonic vibrational analysis. Additional insights are provided into the reactivity of solvated active sites and the formation of key intermediates including their formation energies and vibrational spectroscopic signatures, allowing the development of a detailed understanding of the reaction mechanism. We demonstrate the role of solvated active sites and their influence on the energetics of important species that must be explicitly considered for an accurate understanding of NH3-SCR kinetics.

Copper sulfide nanostructures: synthesis and biological applications.

Over the past few years, considerable attention has been paid to biomedical applications of copper sulfide nanostructures owing to their enhanced physiochemical and pharmacokinetics characteristics in comparison to gold, silver, and carbon nanomaterials. The small-sized Cu x S y nanoparticles have the advantage to absorb efficiently in the near-infrared region (NIR) above 700 nm and the absorption can be tuned by altering their stoichiometries. Moreover, their easy removal through the kidneys overpowers the issue of toxicity caused by many inorganic substances. The low cost and selectivity further add to the advantages of Cu x S y nanostructures as electrode materials in comparison to relatively expensive materials such as silver and gold nanoparticles. This review is mainly focused on the synthesis and biomedical applications of Cu x S y nanostructures. The first part summarizes the various synthetic routes used to produce Cu x S y nanostructures with varying morphologies, while the second part targets the recent progress made in the application of small-sized Cu x S y nanostructures as biosensors, and their analysis and uses in the cure of cancer. Photoacoustic imaging and other cancer treatment applications are discussed. Research on Cu x S y nanostructures will continue to increase over the next few decades, and great opportunities lie ahead for potential biomedical applications of Cu x S y nanostructures.

Photocatalytic Z-Scheme Overall Water Splitting: Recent Advances in Theory and Experiments.

Photocatalytic water splitting is considered one of the most important and appealing approaches for the production of green H2 to address the global energy demand. The utmost possible form of artificial photosynthesis is a two-step photoexcitation known as "Z-scheme", which mimics the natural photosystem. This process solely relies on the effective coupling and suitable band positions of semiconductors (SCs) and redox mediators for the purpose to catalyze the surface chemical reactions and significantly deter the backward reaction. In recent years, the Z-scheme strategies and their key role have been studied progressively through experimental approaches. In addition, theoretical studies based on density functional theory have provided detailed insight into the mechanistic aspects of some breathtakingly complex problems associated with hydrogen evolution reaction and oxygen evolution reaction. In this context, this critical review gives an overview of the fundamentals of Z-scheme photocatalysis, including both theoretical and experimental advancements in the field of photocatalytic water splitting, and suggests future perspectives.

Relationship between psychological distress and resilience in rescue workers.

OBJECTIVES: To assess the relationship between psychological distress and resilience in rescue workers. Following hypothesis was formulated; there would be negative correlation between psychological distress and resilience in rescue workers.  METHOD: A correlational study was conducted from June-August 2015 in Rahim Yar Khan, Punjab, Pakistan. The sample of the present study consisted of 100 rescue workers. The age of the participants ranged from 23 to 40 year old with the mean age of 27.4±3.9 years. Demographic information form, Kessler psychological distress scale and adult resilience measure were administered on the participants to assess the level of psychological distress and resilience.   RESULTS: Pearson product moment coefficient of correlation was applied to analyze the relationship of psychological distress and resilience. Analysis of the result indicated that there is negative relationship between psychological distress and resilience (r= -0.203, p less than 0.01) in rescue workers. Further, contextual factors (r= -0.292, p less than 0.05) and its subcomponents including spiritual beliefs (r= -0.239, p less than 0.05) and cultural resources (r= -0.287, p less than 0.01) were also found to be inversely correlated with psychological distress.  CONCLUSION: The research evidenced that rescue workers were experiencing psychological distress Resilience factors should be considered while designing trainings to preserve mental health and to enhance the psychological well-being of rescue workers.

Contraceptive attitude and behaviour among university men: a study from Punjab, Pakistan.

BACKGROUND: The men's attitudes towards family planning and on the use of family planning method may affect not only their wives intention to use contraception but also the choice of a particular family planning method. This focus of this study is to assess the educated men's role, belief, practice and their participation in family planning. METHODS: A cross-sectional data on 150 university male employees was taken. The logistic regression in connection with stepwise procedures is used to find the most significant variables that influence the men's current use of contraception status. RESULTS: About 42 percent of the married male employees were users of family planning methods. Among family planning methods, condom was the most used method (about 71%) followed by traditional methods (14%). The mean age at first marriage of the respondents was 23 years and for the spouses it was 19 years. CONCLUSION: The knowledge of men in family planning methods is quite universal and general; but the attitude on the use of contraceptives and the family planning method is much different between the employees who had the awareness of contraception and those who had no awareness.

Modelling survival data of thalassaemia patients in Pakistan.

BACKGROUND: Fatimid Foundation with its centers serves as a charitable organization for millions of blood disease carriers in Pakistan. This retrospective survival study is an analysis of the Thalassaemia patients registered in Multan centre who are followed up to nine years to assess the gender risk of death. METHODS: Data on 120 patients of Thalassaemia during 1994-2002 was analyzed. The standard Kaplan-Meier and Nelson-Aalen procedures were used to compare the survival function of the male and female patients of Thalassaemia. The statistical significance was also assessed using log rank test. The Cox Proportional Hazards (PH) model using a forward selection procedure was used to identify the potential factors associated with the increase risk of death. RESULTS: By ignoring the censoring, the average survival time of males and females were calculated to be 1308.1 and 1574.7 days respectively. The average hazard rate for the female group was 0.00033 and for the male group it was 0.00061. The median survival time was estimated from the Kaplan-Meier survival curves (Males: 1400 days, Females: 1785 days). Under the censoring mechanism, the mean survival time for males was calculated to be 1465.82 days with standard error of 146 days, where as for females it was calculated to be 1855.26 with standard error of 151.82 days. When considering death as event of interest Under the Cox modelling approach, we found a male patient of Thalassaemia was 1.484 times more likely to die when compared to his female counterpart. When considering the iron over load as the event of interest, we found a male patient of Thalassaemia was 1.753 fold more likely to reach excessive Haemochromatosis level compared to female patient. CONCLUSION: The analysis reinforces that female group prognosis is better than the male group. Further, our analysis of real survival data set shows that the high status of Haemochromatosis level is associated with the increased risk of death in patients with Thalassaemia with other possible confounders.