Communication: Predictive partial linearized path integral simulation of condensed phase electron transfer dynamics

A partial linearized path integral approach is used to calculate the condensed phase electron transfer (ET) rate by directly evaluating the flux-flux/flux-side quantum time correlation functions. We demonstrate for a simple ET model that this approach can reliably capture the transition between non-adiabatic and adiabatic regimes as the electronic coupling is varied, while other commonly used semi-classical methods are less accurate over the broad range of electronic couplings considered. Further, we show that the approach reliably recovers the Marcus turnover as a function of thermodynamic driving force, giving highly accurate rates over four orders of magnitude from the normal to the inverted regimes. We also demonstrate that the approach yields accurate rate estimates over five orders of magnitude of inverse temperature. Finally, the approach outlined here accurately captures the electronic coherence in the flux-flux correlation function that is responsible for the decreased rate in the inverted regime

Breaking the Correlation between Energy Costs and Kinetic Barriers in Hydrogen Evolution via a Cobalt Pyridine-Diimine-Dioxime Catalyst

A central challenge in the development of inorganic hydrogen evolution catalysts is to avoid deleterious coupling between the energetics of metal site reduction and the kinetics of metal hydride formation. In this work, we combine theoretical and experimental methods to investigate cobalt diimine-dioxime catalysts that show promise for achieving this aim by introducing an intramolecular proton shuttle via a pyridyl pendant group. Using over 200 coupled-cluster-level electronic structure calculations of the Co-based catalyst with a variety of pyridyl substituents, the energetic and kinetic barriers to hydrogen formation are investigated, revealing nearly complete decoupling of the energetics of Co reduction and the kinetics of intramolecular Co hydride formation. These calculations employ recently developed quantum embedding methods that allow for local regions of a molecule to be described using high-accuracy wavefunction methods (such as CCSD(T)), thus overcoming significant errors in the DFT-level description of transition-metal complexes. Experimental synthesis and cyclic voltammetry of the methyl-substituted form of the catalyst indicate that protonation of the pendant group leaves the Co reduction potential unchanged, which is consistent with the theoretical prediction that these catalysts can successfully decouple the electronic structures of the transition-metal and ligand-protonation sites. Additional computational analysis indicates that introduction of the pyridyl pendant group enhances the favorability of intramolecular proton shuttling in these catalysts by significantly reducing the energetic barrier for metal hydride formation relative to previously studied cobalt diimine-dioxime catalysts. These results demonstrate a promising proof of principle for achieving uncoupled and locally tunable intramolecular charge-transfer events in the context of homogeneous transition-metal catalysts

The Schwinger Variational Method

Variational methods have proven invaluable in theoretical physics and chemistry, both for bound state problems and for the study of collision phenomena. For collisional problems they can be grouped into two types: those based on the Schroedinger equation and those based on the Lippmann-Schwinger equation. The application of the Schwinger variational (SV) method to e-molecule collisions and photoionization has been reviewed previously. The present chapter discusses the implementation of the SV method as applied to e-molecule collisions

The correlation between lateralization of intracerebral hemorrhage in basal ganglia and handedness 1

ABSTRACT PURPOSE: To investigate the correlation between lateralization of cerebral basal ganglia hemorrhage and handedness. METHODS: Medical records and computed tomography (CT) scans for 84 patients with primary hypertensive intracerebral hemorrhage (ICH) in basal ganglia were reviewed. Data of gender, age, handedness, and location of basal ganglia hematoma were statistically analyzed. Data of age, gender, handedness, health condition, and mean blood flow velocity (BFV) in middle cerebral arteries (MCAs) and anterior cerebral arteries (ACAs) on both sides of 114 healthy individuals were statistically analyzed. RESULTS: We found out that the patients with right basal ganglia hemorrhage were mostly left-handed, while patients with left basal ganglia hemorrhage were mostly right handed (p=0.021, r=0.251). And the mean BFV in the right MCAs of left-handed ones are relatively higher, the mean BFV in the left MCAs of right-handers are relatively higher (p=0.008, r=0.248). CONCLUSION: There's a correlation between lateralization of cerebral basal ganglia hemorrhage and handedness

Human RNA Polymerase II-Association Factor 1 (hPaf1/PD2) Regulates Histone Methylation and Chromatin Remodeling in Pancreatic Cancer

Change in gene expression associated with pancreatic cancer could be attributed to the variation in histone posttranslational modifications leading to subsequent remodeling of the chromatin template during transcription. However, the interconnected network of molecules involved in regulating such processes remains elusive. hPaf1/PD2, a subunit of the human PAF-complex, involved in the regulation of transcriptional elongation has oncogenic potential. Our study explores the possibility that regulation of histone methylation by hPaf1 can contribute towards alteration in gene expression by nucleosomal rearrangement. Here, we show that knockdown of hPaf1/PD2 leads to decreased di- and tri-methylation at histone H3 lysine 4 residues in pancreatic cancer cells. Interestingly, hPaf1/PD2 colocalizes with MLL1 (Mixed Lineage Leukemia 1), a histone methyltransferase that methylates H3K4 residues. Also, a reduction in hPaf1 level resulted in reduced MLL1 expression and a corresponding decrease in the level of CHD1 (Chromohelicase DNA-binding protein 1), an ATPase dependent chromatin remodeling enzyme that specifically binds to H3K4 di and trimethyl marks. hPaf1/PD2 was also found to interact and colocalize with CHD1 in both cytoplasmic and nuclear extracts of pancreatic cancer cells. Further, reduced level of CHD1 localization in the nucleus in hPaf1/PD2 Knockdown cells could be rescued by ectopic expression of hPaf1/PD2. Micrococcal nuclease digestion showed an altered chromatin structure in hPaf1/PD2-KD cells. Overall, our results suggest that hPaf1/PD2 in association with MLL1 regulates methylation of H3K4 residues, as well as interacts and regulates nuclear shuttling of chromatin remodeling protein CHD1, facilitating its function in pancreatic cancer cells

Observation of Higgs boson production in association with a top quark pair at the LHC with the ATLAS detector

The observation of Higgs boson production in association with a top quark pair (tt H¯ ), based on the analysis of proton–proton collision data at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider, is presented. Using data corresponding to integrated luminosities of up to 79.8 fb−1, and considering Higgs boson decays into b¯ b, W W ∗, τ +τ −, γγ , and Z Z∗, the observed significance is 5.8 standard deviations, compared to an expectation of 4.9 standard deviations. Combined with the tt H¯ searches using a dataset corresponding to integrated luminosities of 4.5 fb−1 at 7 TeV and 20.3 fb−1 at 8 TeV, the observed (expected) significance is 6.3 (5.1) standard deviations. Assuming Standard Model branching fractions, the total tt H¯ production cross section at 13 TeV is measured to be 670 ± 90 (stat.) +110 −100 (syst.) fb, in agreement with the Standard Model prediction

Superhydrophobic Hexadecyltrimethoxysilane-Modified Fumed Silica Nanostructure/Poly(butyl methacrylate) Composite Thin Films via Aerosol-Assisted Deposition: Implications for Self-Cleaning Surfaces

Superhydrophobic coatings with their unique nanostructured surface properties have application in many industrially important technologies but are currently dominated by environmentally problematic fluorinated compounds. Here, we demonstrate the fabrication of fluorocarbon-free superhydrophobic coatings consisting of poly(butyl methacrylate) (PBMA) and nanostructured hexadecyltrimethoxysilane (HDTMS)-functionalized fumed SiO2/PBMA as self-cleaning surfaces via a facile ambient pressure aerosol deposition route. X-ray photoelectron and infrared spectroscopy measurements showed successful composite formation. The deposition temperature and HDTMS-SiO2:PBMA ratio was optimized to give films that had a water contact angle as high as 161 ± 1° and a sliding angle of 1°, owing to a hierarchical surface nano- and microstructure and a root-mean-square surface roughness of 592 nm. This work shows a high-throughput single-step route to environmentally friendly PBMA-based superhydrophobic coatings

Regioselective tetrametalation of ferrocene in a single reaction: Extension of s-block inverse crown chemistry to the d-block

s-Block metal inverse crowns constitute an emerging family of special compounds in which polymetallic amide cationic rings complex anionic guests. They are inverse crowns in the sense that their Lewis acidic/Lewis basic sites have been interchanged relative to those in conventional crown ether complexes, that is, here the metal atoms belong to the ring and not to the core. However, the chemistry controlling their formation goes far beyond that of simple macrocyclic host-guest combinations. It appears that a powerful ring template effect brings about the regioselective deprotonation of certain substrates to create and to encapsulate unusual anions, which are inaccessible through the use of mainstream bases. This field is currently being studied in the search for polymers with unusual properties (e.g., conductive, magnetic, electronic, optical). Also, following this first venture into organometallic chemistry the development prospects for inverse crown chemistry as a whole look decidedly bright with a vast pool of metallocenes now available as potential candidates for exploitation in this exciting new area