Nonorthogonal configuration interaction to study electron and excitation energy transfer

A theoretical study of electron transfer (ET) and excitation energy transfer (EET) processes can yield a more nuanced understanding of the underlying physics that is not always accessible through experiments. The focus of this thesis is the development of nonorthogonal configuration interaction (NOCI) - Fragments, an electronic structure method that has shown promise for the study of ET and EET phenomena. The main aspects of NOCI fragments are: the ability to maintain the diabatic nature of the molecular states involved, a compact extension of the NOCI wave function in terms of many electron base functions (MEBFs) that spin-adapted antisymmetric products of molecular (multiconfiguration) wave functions, direct accessibility of electronic coupling between diabatic states and the inclusion of static correlation effects. NOCI is therefore a viable option to provide an unbiased description of the ground and excited state wavefunctions in a molecular cluster. Singlet fission (SF) is a widely studied EET process for its promise to improve organic photovoltaic efficiency and was chosen as a suitable application to investigate using NOCI fragments. The work done in the thesis enables NOCI-Fragments to: study large molecular systems relevant to ET and EET processes, using multiconfiguration wavefunctions with moderately large active spaces as the initial molecular wavefunctions, dynamic correlation effects within each molecule, and environmental effects. The advances made in this thesis will be helpful to get a clearer and more realistic picture of some photophysical phenomena

Association between symptom profile of schizophrenia and the perceived wellbeing in their caregivers

Background: The chronic nature of Schizophrenia has a devastating impact not only on the patients but also in their caregivers. The burden experienced by the caregivers can seriously affect the psychological wellbeing and caregivers take up multiple coping strategies to tackle the burden. This study was undertaken to find the association between symptom profile of Schizophrenia patients and the perceived wellbeing of their caregivers.Methods: 30 patients with schizophrenia and their caregivers (parents or spouses), who were actively involved in care of the patient for at least 6 months prior to assessment, were included in the study. Patients were evaluated by socio demographic data sheet and Positive and negative syndrome scale (PANSS) while their caregivers were evaluated using Caregiver socio demographic data sheet, Burden Assessment Schedule (BAS), Coping Checklist (CCL) and Psychological Well Being Questionnaire (PWBQ). Statistical analysis was done using Chi square test and Fischer exact test for categorical variables, Pearson correlation to find correlation between data and Analysis of variance (ANOVA) to find significance of study parameters between groups. p < 0.05 was considered significant.Results: Burden experienced by caregivers was more with a severe symptom profile. Moderate correlation is found between patient’s positive symptom profile, negative symptom profile and burden. There was a weak correlation between patient`s symptom profile and care givers coping strategies. The total PANSS scores did not influence the pattern of coping. There was no statistically significant difference in coping strategies in positive and negative symptom of schizophrenia. There was a moderate negative correlation between patient`s symptom profile (positive and total PANSS score) and psychological wellbeing in caregivers. However, there was a weak correlation between patient negative symptom profile and psychological wellbeing in caregivers.Conclusions: Burden and wellbeing of the care givers of schizophrenic patients are closely inter related. These parameters are in turn related to patient’s symptoms profile namely, the overall psychopathology and more with the positive symptoms of schizophrenia. Though all care givers used different coping strategies, there did not appear to be any interrelation between strategies and the perceived burden, well-being and patient’s psychopathology

Clinical correlates of first episode schizophrenia-a comparative study

Background: Schizophrenia is a major mental disorder which has to be assessed early and managed actively even though long term functional outcome remains relatively poor. The aim of the study is to analyze negative symptoms, suicidal risk and substance use in first episode schizophrenics in comparison with multi-episode schizophrenics.Methods: 30 patients with drug naive first episode schizophrenia and 30 patients with multi episode schizophrenia, who attended the outpatient department of Psychiatry, Government Stanley Medical College, Chennai, Tamilnadu, India were studied to compare predisposing factors and spectrum of symptoms for Schizophrenia for a period of one year (January 2010-December 2010). Psychiatric questionnaire by Michael C. Hilton, DAST by Harvey A. Skinner, AUDIT by WHO, Suicide risk scale by National Health and Medical Research Council, PANSS by SR Kay were used to assess patients.Results: Unemployment and family history of suicide attempts were observed more in drug naive first episode schizophrenics. 90% of these patients had completed their primary education while 47% of multi-episode schizophrenics were illiterates. Positive symptoms (delusions, hallucinatory behaviour and suspiciousness) and negative symptoms (blunted affect, emotional withdrawal and social withdrawal) were observed more in first episode schizophrenics while PANSS, DAST, AUDIT scores did not find any differences between both the groups.Conclusions: In our study, the first episode schizophrenia patients were more educated, more unemployed and had more family history of suicide, elevated sub score of positive symptoms as measured by PANSS. Relative assessment of violence and serious behavior problems that are related to positive symptoms must be done and managed with anti psychotics

Electronic couplings for singlet fission : orbital choice and extrapolation to the complete basis set limit

For the search for promising singlet fission candidates, the calculation of the effective electronic coupling, which is required to estimate the singlet fission rate between the initially excited state (S0S1) and the multiexcitonic state ((TT)-T-1, two triplets on neighboring molecules, coupled into a singlet), should be sufficiently reliable and fast enough to explore the configuration space. We propose here to modify the calculation of the effective electronic coupling using a nonorthogonal configuration interaction approach by: (a) using only one set of orbitals, optimized for the triplet state of the molecules, to describe all molecular electronic states, and (b) only taking the leading configurations into consideration. Furthermore, we also studied the basis set convergence of the electronic coupling, and we found, by comparison to the complete basis set limit obtained using the cc-pVnZ series of basis sets, that both the aug-cc-pVDZ and 6-311++G** basis sets are a good compromise between accuracy and computational feasibility. The proposed approach enables future work on larger clusters of molecules than dimers

Electronic couplings for singlet fission:Orbital choice and extrapolation to the complete basis set limit

For the search for promising singlet fission candidates, the calculation of the effective electronic coupling, which is required to estimate the singlet fission rate between the initially excited state (S 0S 1) and the multiexcitonic state ( 1TT, two triplets on neighboring molecules, coupled into a singlet), should be sufficiently reliable and fast enough to explore the configuration space. We propose here to modify the calculation of the effective electronic coupling using a nonorthogonal configuration interaction approach by: (a) using only one set of orbitals, optimized for the triplet state of the molecules, to describe all molecular electronic states, and (b) only taking the leading configurations into consideration. Furthermore, we also studied the basis set convergence of the electronic coupling, and we found, by comparison to the complete basis set limit obtained using the cc-pVnZ series of basis sets, that both the aug-cc-pVDZ and 6–311++G** basis sets are a good compromise between accuracy and computational feasibility. The proposed approach enables future work on larger clusters of molecules than dimers

GronOR:Massively parallel and GPU-accelerated non-orthogonal configuration interaction for large molecular systems

GronOR is a program package for non-orthogonal configuration interaction calculations for an electronic wave function built in terms of anti-symmetrized products of multi-configuration molecular fragment wave functions. The two-electron integrals that have to be processed may be expressed in terms of atomic orbitals or in terms of an orbital basis determined from the molecular orbitals of the fragments. The code has been specifically designed for execution on distributed memory massively parallel and Graphics Processing Unit (GPU)-accelerated computer architectures, using an MPI+OpenACC/OpenMP programming approach. The task-based execution model used in the implementation allows for linear scaling with the number of nodes on the largest pre-exascale architectures available, provides hardware fault resiliency, and enables effective execution on systems with distinct central processing unit-only and GPU-accelerated partitions. The code interfaces with existing multi-configuration electronic structure codes that provide optimized molecular fragment orbitals, configuration interaction coefficients, and the required integrals. Algorithm and implementation details, parallel and accelerated performance benchmarks, and an analysis of the sensitivity of the accuracy of results and computational performance to thresholds used in the calculations are presented

Location of F plasmid transfer operon genes traC and traW and identification of the traW product.

As part of an analysis of the conjugative transfer genes associated with the expression of F pili by plasmid F, we have investigated the physical location of the traC and traW genes. We found that plasmid clones carrying a 2.95-kilobase EcoRI-EcoRV F transfer operon fragment were able to complement transfer of F lac traC mutants and expressed an approximately 92,000-dalton product that comigrates with TraC. We also found that traW-complementing activity was expressed from plasmids carrying a 900-base-pair SmaI-HincII fragment. The traW product was identified as an approximately 23,000-dalton protein. The two different F DNA fragments that expressed traC and traW activities do not overlap. Our data indicate that the traC gene is located in a more-tra operon promoter-proximal position than suggested on earlier maps and that traW is distal to traC. These results resolve a long-standing question concerning the relationship of traW to traC. The clones we have constructed are expected to be useful in elucidating the role of proteins TraC and TraW in F-pilus assembly

Global trends in opioid use for pain management in acute pancreatitis:A multicentre prospective observational study

BACKGROUND: Since there is no current international consensus on the optimal approach for pain management in acute pancreatitis (AP), analgesic practices may vary across different healthcare settings.OBJECTIVE: This study explored global disparities in analgesic use, in particular opioids, during admission and at discharge in hospitalised AP patients.METHODS: This was a post hoc analysis of the prospective PAINAP database, which included all admissions for AP between April and June 2022 with a 1-month follow-up. Demographic details, analgesic use, and clinical outcomes were recorded during admission and at discharge. Odds ratios (ORs) for opioid use during admission and at discharge were identified using multivariable regression analyses.RESULTS: Amongst the 1864 patients (52% males, median age 56 (interquartile range, 41-71)) across three different continents, simple analgesics were predominantly used as the primary analgesic (70%). Opioid use during admission was lowest in European centres (67%). Admission in Asian (OR, 2.53 (95% confidence interval (CI), 1.59-4.04), p &lt; 0.001), and Australian (OR, 5.81 (95% CI, 3.19-10.56), p &lt; 0.001) centres was associated with opioid administration during admission compared with European centres. Increased pain severity, longer pre-admission pain duration, organ failure, and longer length of admission increased opioid use during admission. At discharge, Asian (OR, 2.01 (95% CI, 1.40-2.88), p &lt; 0.001) and Australian (OR, 1.91 (95% CI, 1.28-2.85), p = 0.002) centres were associated with opioid prescription compared with European centres. Increased pain severity, longer pre-admission pain duration, acute necrotic collections, and walled-off necrosis also increased the likelihood of opioid prescription at discharge.CONCLUSION: There are substantial intercontinental differences in opioid use for AP pain. Accordingly, there is a need for international guidelines on pain management in AP.</p

Biofilm Induced Tolerance towards Antimicrobial Peptides

Increased tolerance to antimicrobial agents is thought to be an important feature of microbes growing in biofilms. We address the question of how biofilm organization affects antibiotic susceptibility. We established Escherichia coli biofilms with differential structural organization due to the presence of IncF plasmids expressing altered forms of the transfer pili in two different biofilm model systems. The mature biofilms were subsequently treated with two antibiotics with different molecular targets, the peptide antibiotic colistin and the fluoroquinolone ciprofloxacin. The dynamics of microbial killing were monitored by viable count determination, and confocal laser microscopy. Strains forming structurally organized biofilms show an increased bacterial survival when challenged with colistin, compared to strains forming unstructured biofilms. The increased survival is due to genetically regulated tolerant subpopulation formation and not caused by a general biofilm property. No significant difference in survival was detected when the strains were challenged with ciprofloxacin. Our data show that biofilm formation confers increased colistin tolerance to cells within the biofilm structure, but the protection is conditional being dependent on the structural organization of the biofilm, and the induction of specific tolerance mechanisms