Modelling the non-radiative singlet excited state isomerization of diphenyl-acetylene: A vibronic coupling model

Tolane (diphenyl-acetylene) is the smallest component of macromolecular arrays known as dendrimers that have interesting energy transport properties after photo-excitation. In this paper, a vibronic coupling Hamiltonian is set up to describe the initial isomerization of this molecule. The calculated absorption spectrum is in good agreement with experiment, with the ordering of states and energies from MRCI-DFT calculation. The focus of the study is the pathway for photo-excited isomerisation from the linear geometry at the Frank-Condon point to a trans-structure. The model shows that the origin of the excited-state minimum for the trans-isomer is due to stabilisation of a high lying state. Quantum dynamics calculations using the MCTDH algorithm show the model agrees with experiment that isomerisation only occurs at high temperature. It also suggests that internal conversion to the S1 global minima happens via second order coupling terms, which can explain the observed picosecond timescales

Severe EBV Infection In Primary Immunodeficiency And The Normal Host

Epstein–Barr virus (EBV) infection is ubiquitous in humans, but the majority of infections have an asymptomatic or self-limiting clinical course. Rarely, individuals may develop a pathological EBV infection with a variety of life threatening complications (including haemophagocytosis and malignancy) and others develop asymptomatic chronic EBV viraemia. Although an impaired ability to control EBV infection has long been recognised as a hallmark of severe T-cell immunodeficiency, the advent of next generation sequencing has identified a series of Primary Immunodeficiencies in which EBV-related pathology is the dominant feature. Chronic active EBV infection is defined as chronic EBV viraemia associated with systemic lymphoproliferative disease, in the absence of immunodeficiency. Descriptions of larger cohorts of patients with chronic active EBV in recent years have significantly advanced our understanding of this clinical syndrome. In this review we summarise the current understanding of the pathophysiology and natural history of these diseases and clinical syndromes, and discuss approaches to the investigation and treatment of severe or atypical EBV infection

Synchronous neural oscillations in Parkinson’s disease: Variability and its potential network mechanisms

poster abstractRecent studies indicate that patterns of oscillatory synchronous activity in Basal Ganglia (BG) may be relevant to BG physiology and disorders, including Parkinson’s disease (PD). Oscillations in BG, in particular, in relation to motor control, are observed in different species, different conditions and different dopaminergic states (e.g., PD vs. normal). The rich membrane properties of BG neurons easily support oscillatory behavior. Correlations of oscillatory activity between different BG locations depend on the brain state and are dynamically organized. A general feature of BG oscillations is strong power and correlations of the β-band activity when no movement is performed and replacement of β with γ-band activity during movement. Dopamine-depleted state, such as PD, is marked by increase of oscillatory and synchronous activity, in particular in the β-band. This study explores the dynamical nature of these oscillations on short time-scales

Synchronous neural oscillations in Parkinson’s disease: Variability and its potential network mechanisms

poster abstractRecent studies indicate that patterns of oscillatory synchronous activity in Basal Ganglia (BG) may be relevant to BG physiology and disorders, including Parkinson’s disease (PD). Oscillations in BG, in particular, in relation to motor control, are observed in different species, different conditions and different dopaminergic states (e.g., PD vs. normal). The rich membrane properties of BG neurons easily support oscillatory behavior. Correlations of oscillatory activity between different BG locations depend on the brain state and are dynamically organized. A general feature of BG oscillations is strong power and correlations of the β-band activity when no movement is performed and replacement of β with γ-band activity during movement. Dopamine-depleted state, such as PD, is marked by increase of oscillatory and synchronous activity, in particular in the β-band. This study explores the dynamical nature of these oscillations on short time-scales

Neural Dynamics in Parkinsonian Brain:The Boundary Between Synchronized and Nonsynchronized Dynamics

Synchronous oscillatory dynamics is frequently observed in the human brain. We analyze the fine temporal structure of phase-locking in a realistic network model and match it with the experimental data from parkinsonian patients. We show that the experimentally observed intermittent synchrony can be generated just by moderately increased coupling strength in the basal ganglia circuits due to the lack of dopamine. Comparison of the experimental and modeling data suggest that brain activity in Parkinson's disease resides in the large boundary region between synchronized and nonsynchronized dynamics. Being on the edge of synchrony may allow for easy formation of transient neuronal assemblies

Rapid turnover of effector-memory CD4(+) T cells in healthy humans

Memory T cells can be divided into central-memory (T(CM)) and effector-memory (T(EM)) cells, which differ in their functional properties. Although both subpopulations can persist long term, it is not known whether they are maintained by similar mechanisms. We used in vivo labeling with deuterated glucose to measure the turnover of CD4(+) T cells in healthy humans. The CD45R0(+)CCR7(-) T(EM) subpopulation was shown to have a rapid proliferation rate of 4.7% per day compared with 1.5% per day for CD45R0(+)CCR7(+) T(CM) cells; these values are equivalent to average intermitotic (doubling) times of 15 and 48 d, respectively. In contrast, the CD45RA(+)CCR7(+) naive CD4(+) T cell population was found to be much longer lived, being labeled at a rate of only 0.2% per day (corresponding to an intermitotic time of approximately 1 yr). These data indicate that human CD4(+) T(EM) cells constitute a short-lived cell population that requires continuous replenishment in vivo

Rapid turnover of T cells in acute infectious mononucleosis.

During acute infectious mononucleosis (AIM), large clones of Epstein-Barr virus-specific T lymphocytes are produced. To investigate the dynamics of clonal expansion, we measured cell proliferation during AIM using deuterated glucose to label DNA of dividing cells in vivo, analyzing cells according to CD4, CD8 and CD45 phenotype. The proportion of labeled CD8(+)CD45R0(+) T lymphocytes was dramatically increased in AIM subjects compared to controls (mean 17.5 versus 2.8%/day; p<0.005), indicating very rapid proliferation. Labeling was also increased in CD4(+)CD45R0(+) cells (7.1 versus 2.1%/day; p<0.01), but less so in CD45RA(+) cells. Mathematical modeling, accounting for death of labeled cells and changing pool sizes, gave estimated proliferation rates in CD8(+)CD45R0(+) cells of 11-130% of cells proliferating per day (mean 47%/day), equivalent to a doubling time of 1.5 days and an appearance rate in blood of about 5 x 10(9) cells/day (versus 7 x 10(7) cells/day in controls). Very rapid death rates were also observed amongst labeled cells (range 28-124, mean 57%/day),indicating very short survival times in the circulation. Thus, we have shown direct evidence for massive proliferation of CD8(+)CD45R0(+) T lymphocytes in AIM and demonstrated that rapid cell division continues concurrently with greatly accelerated rates of cell disappearance

Enstatite (MgSiO\u3csub\u3e3\u3c/sub\u3e) and forsterite (Mg\u3csub\u3e2\u3c/sub\u3eSiO\u3csub\u3e4\u3c/sub\u3e) monomers and dimers: Highly detectable infrared and radioastronomical molecular building blocks

© 2019 The Author(s). Isolated MgSiO3 and Mg2SiO4 molecules are shown here to exhibit bright infrared (IR) features that fall close to unattributed astronomical lines observed toward objects known to possess crystalline enstatite and forsterite, minerals of the same respective empirical formulae. These molecules are therefore tantalizing candidates for explaining the origin of such features. Furthermore, the C2v monomer minima of each formula set have dipole moments on the order of 10.0 D or larger making them desirable candidates for radioastronomical observation as enabled through rotational spectroscopic data further provided in this high-level CCSD(T)- F12/cc-pVTZ-F12 quantum chemical study. Astrophysical detection of these molecules could inform the build-up pathways for creating nanocrystals from smallmolecules in protoplanetary discs or could showthe opposite in explaining the destruction of enstatite and forsterite minerals in supernovae events or other high-energy stellar processes. This work also shows that the lowest energy isomers for molecules containing the geologically necessary elements Mg and Si have oxygen bonded between any of the other heavier elements making oxygen the glue for pre-mineralogic chemistry