Strength of π-Stacking, from Neutral to Cation: Precision Measurement of Binding Energies in an Isolated π-Stacked Dimer

π-Stacking interactions are ubiquitious across chemistry and biochemistry, impacting areas from organic materials and photovoltaics to biochemistry and DNA. However, experimental data is lacking regarding the strength of π-stacking forces—an issue not settled even for the simplest model system, the isolated benzene dimer. Here, we use two-color appearance potential measurements to determine the binding energies of the isolated, π-stacked dimer of fluorene (C13H10) in ground, excited, and ionic states. Our measurements provide the first precise values for π-stacking interaction energies in these states, which are key benchmarks for theory. Indeed, theoretical predictions using ab initio and carefully benchmarked DFT methods are in excellent agreement with experiment

The Role of Torsional Dynamics on Hole and Exciton Stabilization in π‐Stacked Assemblies: Design of Rigid Torsionomers of a Cofacial Bifluorene

Exciton and charge delocalization across π‐stacked assemblies is of importance in biological systems and functional polymeric materials. To examine the requirements for exciton and hole stabilization, cofacial bifluorene (F2) torsionomers were designed, synthesized, and characterized: unhindered (model) MeF2, sterically hindered tBuF2, and cyclophane‐like CF2, where fluorenes are locked in a perfect sandwich orientation via two methylene linkers. This set of bichromophores with varied torsional rigidity and orbital overlap shows that exciton stabilization requires a perfect sandwich‐like arrangement, as seen by strong excimeric‐like emission only in CF2 and MeF2. In contrast, hole delocalization is less geometrically restrictive and occurs even in sterically hindered tBuF2, as judged by 160 mV hole stabilization and a near‐IR band in the spectrum of its cation radical. These findings underscore the diverse requirements for charge and energy delocalization across π‐stacked assemblies

A Semiparametrically Efficient Estimator of the Time‐Varying Effects for Survival Data with Time‐Dependent Treatment

The timing of a time‐dependent treatment—for example, when to perform a kidney transplantation—is an important factor for evaluating treatment efficacy. A naïve comparison between the treated and untreated groups, while ignoring the timing of treatment, typically yields biased results that might favour the treated group because only patients who survive long enough will get treated. On the other hand, studying the effect of a time‐dependent treatment is often complex, as it involves modelling treatment history and accounting for the possible time‐varying nature of the treatment effect. We propose a varying‐coefficient Cox model that investigates the efficacy of a time‐dependent treatment by utilizing a global partial likelihood, which renders appealing statistical properties, including consistency, asymptotic normality and semiparametric efficiency. Extensive simulations verify the finite sample performance, and we apply the proposed method to study the efficacy of kidney transplantation for end‐stage renal disease patients in the US Scientific Registry of Transplant Recipients.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134221/1/sjos12196_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/134221/2/sjos12196.pd

Electronic Structures and Optical Properties of Phenyl C 71

Phenyl C71 butyric acid methyl ester (PC71BM) has been adopted as electron acceptor materials in bulk heterojunction solar cells with relatively higher power conversion efficiency. The understanding of the mechanism and performance for the devices based upon PC71BM requires the information of conformations, electronic structures, optical properties, and so forth. Here, the geometries, IR and Raman, electronic structures, polarizabilities, and hyperpolarizabilities of PC71BM isomers are studied by using density functional theory (DFT); the absorption and excitation properties are investigated via time-dependent DFT with B3LYP, PBE0, and CAM-B3LYP functionals. The calculated results show that [6,6]PC71BM is more stable than [5,6]PC71BM due to the lower total energy. The vibrational modes of the isomers at IR and Raman peaks are quite similar. As to absorption properties, CAM-B3LYP functional is the suitable functional for describing the excitations of PC71BM because the calculated results with CAM-B3LYP functional agree well with that of the experiment. The analysis of transition configurations and molecular orbitals demonstrated that the transitions at the absorption maxima in UV/Vis region are localized π-π* transitions in fullerenes cages. Furthermore, the larger isotropic polarizability of PC71BM indicates that the response of PC71BM to applied external electric field is stronger than that of PC61BM, and therefore resulting into better nonlinear optical properties

Bufei Huoxue Capsule Attenuates PM2.5-Induced Pulmonary Inflammation in Mice

Atmospheric fine particulate matter 2.5 (PM 2.5) may carry many toxic substances on its surface and this may pose a public health threat. Epidemiological research indicates that cumulative ambient PM2.5 is correlated to morbidity and mortality due to pulmonary and cardiovascular diseases and cancer. Mitigating the toxic effects of PM2.5 is therefore highly desired. Bufei Huoxue (BFHX) capsules have been used in China to treat pulmonary heart disease (cor pulmonale). Thus, we assessed the effects of BFHX capsules on PM2.5-induced pulmonary inflammation and the underlying mechanisms of action. Using Polysearch and Cytoscape 3.2.1 software, pharmacological targets of BFHX capsules in atmospheric PM2.5-related respiratory disorders were predicted and found to be related to biological pathways of inflammation and immune function. In a mouse model of PM2.5-induced inflammation established with intranasal instillation of PM2.5 suspension, BFHX significantly reduced pathological response and inflammatory mediators including IL-4, IL-6, IL-10, IL-8, TNF-α, and IL-1β. BFHX also reduced keratinocyte growth factor (KGF), secretory immunoglobulin A (sIgA), and collagen fibers deposition in lung and improved lung function. Thus, BFHX reduced pathological responses induced by PM2.5, possibly via regulation of inflammatory mediators in mouse lungs

Modulation of Ca2+ Signals by Epigallocatechin-3-gallate(EGCG) in Cultured Rat Hippocampal Neurons

Green tea has been receiving considerable attention as a possible neuroprotective agent against neurodegenerative disease. Epigallocatechin-3-gallate (EGCG) is the major compound of green tea. Calcium signaling has profound effects on almost all aspects of neuronal function. Using digital calcium imaging and patch-clamp technique, we determined the effects of EGCG on Ca2+ signals in hippocampal neurons. The results indicated that EGCG caused a dose-dependent increase in intracellular Ca2+ ([Ca2+]i). This [Ca2+]i increase was blocked by depleting intracellular Ca2+ stores with the endoplasmic reticulum Ca2+ pump inhibitor thapsigargin and cyclopiazonic acid. Furthermore, EGCG-stimulated increase in [Ca2+]i was abolished following treatment with a PLC inhibitor. However, EGCG inhibited high-voltage activated Ca2+ currents (IHVA) and NMDA-induced inward currents (INMDA). These data suggest that EGCG triggers a cascade of events: it activates phospholipase C (PLC), mobilizes intracellular Ca2+ stores, raises the cytosolic Ca2+ levels, and inhibits the VGCC and NMDA receptors-mediated Ca2+ influx through a process that remains to be determined

Mechanical, Toughness and Thermal properties of 2D Material- Reinforced Epoxy Composites

Developing epoxy composites with high thermal conductivity and excellent mechanical properties becomes imperative in electronic and aerospace industries. This study investigates and compares the effect of adding boron nitride (BN) sheets and graphene platelets (GnPs) on the mechanical properties and thermal conductivity of epoxy resin. The study shows that incorporation of BN or GnPs into epoxy matrix significantly enhanced both mechanical properties and thermal conductivity of epoxy composites. At fractions ranging 1–4 wt%, GnPs/epoxy composites provide higher Young’s modulus, fracture toughness (K1c) and critical stress energy release rate (G1c) compared to BN/epoxy composites. The thermal conductivity of the epoxy composites is up to the maximum of 0.33 Wm 1 K 1 at 4 wt% of GnP loading, which is much higher than that of the composites filled with the same loading of BN (0.23 Wm 1 K 1 ). The study emphasizes the importance of adding thin nanosheets (thickness 3–5 nm) at low loadings in developing epoxy composites to achieve desired mechanical and thermal properties

Search for the Rare Decays J/Psi --> Ds- e+ nu_e, J/Psi --> D- e+ nu_e, and J/Psi --> D0bar e+ e-

We report on a search for the decays J/Psi --> Ds- e+ nu_e + c.c., J/Psi --> D- e+ nu_e + c.c., and J/Psi --> D0bar e+ e- + c.c. in a sample of 5.8 * 10^7 J/Psi events collected with the BESII detector at the BEPC. No excess of signal above background is observed, and 90% confidence level upper limits on the branching fractions are set: B(J/Psi --> Ds- e+ nu_e + c.c.)<4.8*10^-5, B(J/Psi --> D- e+ nu_e + c.c.) D0bar e+ e- + c.c.)<1.1*10^-5Comment: 10 pages, 4 figure