Stress-energy connection and cosmological constant problem

We study gravitational properties of vacuum energy by erecting a geometry on the stress-energy tensor of vacuum, matter and radiation. Postulating that the gravitational effects of matter and radiation can be formulated by an appropriate modification of the spacetime connection, we obtain varied geometrodynamical equations which properly comprise the usual gravitational field equations with, however, Planck-suppressed, non-local, higher-dimensional additional terms. The prime novelty brought about by the formalism is that, the vacuum energy does act not as the cosmological constant but as the source of the gravitational constant. The formalism thus deafens the cosmological constant problem by channeling vacuum energy to gravitational constant. Nevertheless, quantum gravitational effects, if any, restore the problem via the graviton and graviton-matter loops, and the mechanism proposed here falls short of taming such contributions to cosmological constant.     

Isothermal crystallization of P3HT:PCBM blends studied by RHC

Defining appropriate annealing temperatures and times is vitally important for increasing the efficiency of bulk heterojunction solar cells by favoring the crystallinity of the polymer-fullerene blend components. In order to better understand the annealing process, the isothermal crystallization of poly(3-hexyl thiophene) (P3HT) and [6,6]-phenyl C₆₁-butyric acid methyl ester (PCBM) blend investigated by means of rapid heating cooling calorimetry (RHC). Isothermal crystallization experiments at temperatures in between the glass transition and melting, within the temperature range of 70–150 °C, can successfully be performed since RHC permits cooling at a sufficiently high rate in order to prevent crystallization during cooling. Crystallization isotherms were determined from the subsequent melting behavior of the blend. They were measured for a wide set of annealing temperatures and times, and the evolution of the crystallization rate with temperature is compared for annealing from the glassy state and from the melt state.     

Experimental and theoretical study on the structure and vibrational spectra of β-2-aminopyridinium dihydrogenphosphate

Experimental and theoretical vibrational spectra of β-2-aminopyridinium dihydrogenphosphate (β-2APDP) have been investigated. The FT-IR spectrum of β-2APDP was recorded in the region 4000-400 cm(-1). The optimized molecular structure and theoretical vibrational frequencies of β-2APDP have been investigated using ab initio Hartree-Fock (HF) and density functional B3LYP method with 6-311++G(d,p) basis set. The optimized geometric parameters (bond lengths and bond angles) and theoretical frequencies have been compared with the corresponding experimental data and it is found that they agree well with each other. All the assignments of the theoretical frequencies were performed by potential energy distributions using VEDA 4 program. Furthermore, the used scale factors were obtained from the ratio of the frequency values of the strongest peaks in the experimental and theoretical IR spectra. From the results it was concluded that the B3LYP method is superior to the HF method for the vibrational frequencies.     

An Efficient Synthesis of Substituted 2H-Pyran-2-one Derivatives via the Conjugated Addition of the Enolates of Carbonyl Compounds to Enaminoesters

Short simple synthesis of alkenoic acid esters and their intramolecular cyclization products, 2H-Pyran-2-ones from enolates of carbonyl compounds and enaminoesters are described.     

Synthesis of a Novel m-Substituted Poly(phenoxy-imine) and Investigation of its Fluorescence and Some Properties

Oxidative polycondensation of 3-((2-phenylhydrazono)methyl)phenol (3-PHMP), a new m-substituted poly(phenoxy-imine), was studied using oxidants such as sodium hypochlorite, air (O₂) and hydrogen peroxide in an aqueous alkaline medium under various polymerization conditions. The macromolecular structure and optical properties of the polymer were characterized with elemental analysis, Size Exclusion Chromatography (SEC), Fourier Transform Infrared (FTIR), Nuclear Magnetic Resonance (NMR), absorption and fluorescence spectroscopy techniques. As a result of fluorescence measurement, the fluorescence lifetime of poly(3-PHMP) in DMF was calculated as 2.88 ns (χ²= 1.12). An electrochemical property the monomer and polymer were also studied using Cyclic Voltammetry (CV) technology. According to the CV measurements, the electrochemical band gaps (E_g′) of 3-PHMP and poly(3-PHMP) were found to be 2.64 and 1.94 eV, respectively. Electrical conductivity of the polymer was measured by the four-point probe technique. The electrical conductivity of poly(3-PHMP) was found to be ～3.2 × 10^?2S/cm. Thermo Gravimetric Analysis (TGA) revealed poly(3-PHMP) to be stable against thermo-oxidative decomposition. In addition, the in vitro antimicrobial activities of the synthesized compounds were tested on various microorganisms.     

Slurry sampling electrothermal atomic absorption spectrometric determination of chromium after separation/enrichment by mercaptoundecanoic acid modified gold coated TiO2 nanoparticles

In this study, a novel preconcentration/separation technique based on the slurry analysis of chromium loaded on mercaptoundecanoic acid modified TiO₂ core-Au shell nanoparticles prior to its determination by electrothermal atomic absorption spectrometry was described. For this purpose, at first, TiO₂ nanoparticles were coated with gold shell and then modified with mercaptoundecanoic acid (MUA). Cr (III) was collected on the prepared sorbent by conventional batch technique. After separation of liquid phase, slurry of the sorbent was prepared and directly introduced into graphite furnace of atomic absorption spectrometry. By this way, all drawbacks due to elution procedure were eliminated. Optimum conditions for quantitative sorption and preparation of the slurry were investigated. The chromium in certificated sea-water and spiked drinking water was recovered in the range of 95% confidence level. The proposed technique was fast and simple as well as the risks of contamination and loss during elution were low. The limit of detection (3σ, N = 10) was 0.34 μg L^{− 1}.     

Effects of Green Tea Powder,Pomegranate Peel Powder,Epicatechin and Punicalagin Additives on Antimicrobial,Antioxidant Potential and Quality Properties of Raw Meatballs

Alternative technologies, which have been developed in order to meet the consumers’ demand for nourishing and healthy meat and meat products, are followed by the food industry. In the present study, it was determined, using the HPLC method, that green tea contains a high level of epicatechin (EP) under optimal conditions and that pomegranate peel contains a high level of punicalagin (PN). Green tea, pomegranate peel, EP and PN were added to meatballs at different concentrations in eight groups. The antioxidant capacities of extracts were measured. The antimicrobial activity was examined for 72 h using three different food pathogens. The highest level of antimicrobial activity was achieved in the 1% punicalagin group, whereas the minimum inhibition concentration (L. monocytogenes, S. typhimurium) was found to be 1.87 mg/mL. A statistically significant decrease was found in FFA, POV and TBARS levels of meatballs on different days of storage (p < 0.05). When compared to the control group, the bioactive compounds preserved the microbiological and chemical properties of meatballs during storage at +4 °C (14 days). It was concluded that the extracts with high EP and PN concentrations can be used as bio-preservative agents for meat and meat products.     

Inflation with non-minimal coupling: Metric vs. Palatini formulations

We analyze non-minimally coupled scalar field theories in metric (second-order) and Palatini (first-order) formalisms in a comparative fashion. After contrasting them in a general setup, we specialize to inflation and find that the two formalisms differ in their predictions for various cosmological parameters. The main reason is that dependencies on the non-minimal coupling parameter are different in the two formalisms. For successful inflation, the Palatini approach prefers a much larger value for the non-minimal coupling parameter than the Metric approach. Unlike the Metric formalism, in Palatini, the inflaton stays well below the Planck scale whereby providing a natural inflationary epoch.     

Simulations of grazing-incidence pumped Ni-like Sn X-ray laser at 11.9 nm

Grazing-incidence pumped Ni-like Sn X-ray laser media at 11.9 nm (4d-4p, J = 0-1) is modelled using code EHYBRID and a post-processor code. The required atomic data are obtained using the Cowan code. In this study the pre-formed plasma is pumped on longitudinal direction with a grazing angle. Detailed simulations were performed to optimize the driving laser configurations. Relatively high gain is produced for the Ni-like Sn X-ray laser at 11.9 nm with long pre-pulse and short main pulse drive energy of only 100 mJ on 4 mm slab targets. Using low intensity pre-pulse prior to long pulse decreases the electron density gradient. X-ray resonance lines between 13 and 25 Å emitted from tin plasma have been simulated using post-processor coupled with EHYBRID. The ratio of these resonance lines can be used to measure electron temperature of the laser produced Sn plasma.     

Large Spin‐Relaxation Barriers for the Low‐Symmetry Organolanthanide Complexes [Cp*2Ln(BPh4)] (Cp*=pentamethylcyclopentadienyl; Ln=Tb,Dy)

Single‐molecule magnets comprising one spin center represent a fundamental size limit for spin‐based information storage. Such an application hinges upon the realization of molecules possessing substantial barriers to spin inversion. Axially symmetric complexes of lanthanides hold the most promise for this due to their inherently high magnetic anisotropies and low tunneling probabilities. Herein, we demonstrate that strikingly large spin reversal barriers of 216 and 331 cm^?1 can also be realized in low‐symmetry lanthanide tetraphenylborate complexes of the type [Cp*₂Ln(BPh₄)] (Cp*=pentamethylcyclopentadienyl; Ln=Tb ( 1 ) and Dy ( 2 )). The dysprosium congener showed hysteretic magnetization data up to 5.3 K. Further studies of the magnetic relaxation processes of 1 and 2 under applied dc fields and upon dilution within a matrix of [Cp*₂Y(BPh₄)] revealed considerable suppression of the tunneling pathway, emphasizing the strong influence of dipolar interactions on the low‐temperature magnetization dynamics in these systems.