Measurement of the ratio of B+ and B0 meson lifetimes

The ratio of the B+ and B0 meson lifetimes was measured using data collected in 2002-2004 by the D0 experiment in Run II of the Fermilab Tevatron Collider. These mesons were reconstructed in B-->mu(+)nuD(*-)X decays, which are dominated by B0 and B-->mu(+)nuD 0X decays, which are dominated by B+. The ratio of lifetimes is measured to be tau(+)/tau(0)=1.080+/-0.016(stat)+/-0.014(syst).     

Search for anomalous heavy-flavor quark production in association with W bosons

We search for anomalous production of heavy-flavor quark jets in association with W bosons at the Fermilab Tevatron pp Collider in final states in which the heavy-flavor quark content is enhanced by requiring at least one tagged jet in an event. Jets are tagged using one algorithm based on semileptonic decays of b/c hadrons, and another on their lifetimes. We compare e+jets (164 pb(-1)) and mu+jets (145 pb(-1)) channels collected with the D0 detector at sqrt[s]=1.96 TeV to expectations from the standard model and set upper limits on anomalous production of such events.     

Length and substituent-scrambling energies of parent and halogen-substituted conjugated polyynes

Conjugated polyynes are a class of species of diverse and increasing interest. Length-scrambling and substituent scrambling reaction energies were examined using ab initio quantum chemistry calculations to investigate issues concerning the energetic effects of the molecular ends (substituent communication). Computations were performed for the parent, monohalogenated, and dihalogenated (F, Cl, Br, I) polyynes of up to 60 carbon atoms. A study of resonance effects using natural resonance theory and bond lengths demonstrates lone-pair-donating effects that increase in the series F < Cl < Br < I, but run counter to the halogen inductive effects which decrease in this series and dominate energetic effects.     

Wedge cutting of mild steel by CO2 laser and cut-quality assessment in relation to normal cutting

In some applications, laser cutting of wedge surfaces cannot be avoided in sheet metal processing and the quality of the end product defines the applicability of the laser-cutting process in such situations. In the present study, CO₂ laser cutting of the wedge surfaces as well as normal surfaces (normal to laser beam axis) is considered and the end product quality is assessed using the international standards for thermal cutting. The cut surfaces are examined by the optical microscopy and geometric features of the cut edges such as out of flatness and dross height are measured from the micrographs. A neural network is introduced to classify the striation patterns of the cut surfaces. It is found that the dross height and out of flatness are influenced significantly by the laser output power, particularly for wedge-cutting situation. Moreover, the cut quality improves at certain value of the laser power intensity.     

Cemented carbide cutting tool: Laser processing and thermal stress analysis

Laser treatment of cemented carbide tool surface consisting of W, C, TiC, TaC is examined and thermal stress developed due to temperature gradients in the laser treated region is predicted numerically. Temperature rise in the substrate material is computed numerically using the Fourier heating model. Experiment is carried out to treat the tool surfaces using a CO₂ laser while SEM, XRD and EDS are carried out for morphological and structural characterization of the treated surface. Laser parameters were selected include the laser output power, duty cycle, assisting gas pressure, scanning speed, and nominal focus setting of the focusing lens. It is found that temperature gradient attains significantly high values below the surface particularly for titanium and tantalum carbides, which in turn, results in high thermal stress generation in this region. SEM examination of laser treated surface and its cross section reveals that crack initiation below the surface occurs and crack extends over the depth of the laser treated region.     

Development and Optimization of Methylcellulose-Based Nanoemulgel Loaded with Nigella sativa Oil for Oral Health Management: Quadratic Model Approach

The present study aimed to develop a local dental nanoemulgel formulation of Nigella sativa oil (NSO) for the treatment of periodontal diseases. NSO purchased from a local market was characterized using a GC–MS technique. A nanoemulsion containing NSO was prepared and incorporated into a methylcellulose gel base to develop the nanoemulgel formulation. The developed formulation was optimized using a Box–Behnken statistical design (quadratic model) with 17 runs. The effects of independent factors, such as water, oil, and polymer concentrations, were studied on two dependent responses, pH and viscosity. The optimized formulation was further evaluated for droplet size, drug release, stability, and antimicrobial efficacy. The developed formulation had a pH of 7.37, viscosity of 2343 cp, and droplet size of 342 ± 36.6 nm. Sustained release of the drug from the gel for up to 8 h was observed, which followed Higuchi release kinetics with non-Fickian diffusion. The developed nanoemulgel formulation showed improved antimicrobial activity compared to the plain NSO. Given the increasing emergence of periodontal diseases and antimicrobial resistance, an effective formulation based on a natural antibacterial agent is warranted as a dental therapeutic agent.     

Potential Therapeutic Benefits of Honey in Neurological Disorders: The Role of Polyphenols

Honey is the principal premier product of beekeeping familiar to Homo for centuries. In every geological era and culture, evidence can be traced to the potential usefulness of honey in several ailments. With the advent of recent scientific approaches, honey has been proclaimed as a potent complementary and alternative medicine for the management and treatment of several maladies including various neurological disorders such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, and multiple sclerosis, etc. In the literature archive, oxidative stress and the deprivation of antioxidants are believed to be the paramount cause of many of these neuropathies. Since different types of honey are abundant with certain antioxidants, primarily in the form of diverse polyphenols, honey is undoubtedly a strong pharmaceutic candidate against multiple neurological diseases. In this review, we have indexed and comprehended the involved mechanisms of various constituent polyphenols including different phenolic acids, flavonoids, and other phytochemicals that manifest multiple antioxidant effects in various neurological disorders. All these mechanistic interpretations of the nutritious components of honey explain and justify the potential recommendation of sweet nectar in ameliorating the burden of neurological disorders that have significantly increased across the world in the last few decades.     

Recent progress in EPR study of spin labeled polymers and spin probed polymer systems

The EPR technique is commonly used for the detection and characterization of paramagnetic centers in chemical science. This method can provides a lot of information, such as identity, structure, dynamics, interaction, orientation, glass transition temperature, adsorption behavior, functionality, phase behavior, nano-inhomogeneities, and conformation of the free-radical portion of the polymer chain. Most polymers intrinsically possess diamagnetic properties, so in order to study polymers with EPR, paramagnetic centers need to be incorporated into the polymer systems. Spin labeling and spin probing are main methods of covalently attaching paramagnetic centers to polymer chains or embedding them in polymer matrices through non-covalent interactions, respectively. Spin labeling and spin probing techniques for polymers and polymer systems (especially with nitroxide radicals) have also been studied, which have a profound impact on polymer science. This review focuses on the continuous wave EPR technique and introduces the recent advances in spin labeled polymers and spin probed polymer systems in EPR research.     

Electronic excitation dynamics in multichromophoric systems described via a polaron-representation master equation

We derive a many-site version of the non-Markovian time-convolutionless polaron master equation [Jang et al., J. Chem Phys. 129, 101104 (2008)] to describe electronic excitation dynamics in multichromophoric systems. By treating electronic and vibrational degrees of freedom in a combined frame (polaron frame), this theory is capable of interpolating between weak and strong exciton-phonon coupling and is able to account for initial non-equilibrium bath states and spatially correlated environments. Besides outlining a general expression for the expected value of any electronic system observable in the original frame, we also discuss implications of the Markovian and Secular approximations highlighting that they need not hold in the untransformed frame despite being strictly satisfied in the polaron frame. The key features of the theory are illustrated using as an example a four-site subsystem of the Fenna-Mathews-Olson light-harvesting complex. For a spectral density including a localised mode, we show that oscillations of site populations may only be observed when non-equilibrium bath effects are taken into account. Furthermore, we illustrate how this formalism allows us to identify the electronic and vibrational components of the oscillatory dynamics.