The rotational spectra, potential function, Born-Oppenheimer breakdown, and magnetic shielding of SnSe and SnTe

The pure rotational spectra of 27 isotopic species of SnSe and SnTe have been measured in the frequency range of 5-24 GHz using a Fabry-Perot-type resonator pulsed-jet Fourier-transform microwave spectrometer. Gaseous samples of both chalcogenides were prepared by laser ablation of suitable target rods and were stabilized in supersonic jets of Ar. Global multi-isotopolog analyses of all available high-resolution data produced spectroscopic Dunham parameters Y01, Y11, Y21, Y31, Y02, and Y12 for both species, as well as Born-Oppenheimer breakdown (BOB) coefficients delta01 for Sn, Se, and Te. A direct fit of the same data sets to an appropriate radial Hamiltonian yielded analytic potential energy functions and BOB radial functions for the X 1Sigma+ electronic state of both SnSe and SnTe. Additionally, the magnetic hyperfine interaction produced by the dipolar nuclei 119Sn, 117Sn, 77Se, and 125Te was observed, yielding first determinations of the corresponding spin-rotation coupling constants.     

Potassium Concentration Alters Calibration Sensitivities of Dopamine but not Serotonin

The use of carbon fibre microelectrodes and amperometric techniques for measurement of biological molecules has been widely studied. The use of calibrations to translate biological data is common practice between labs. Tris buffer is commonly used for conducting calibrations, where potassium ion concentrations are varied in buffers. However, little is known about how changes in this ion alter the calibration sensitivity of neurotransmitters. This work showcases that dopamine calibrations are highly dependent on the concentration of potassium ions, whilst serotonin is less affected. Our findings have implications on interpretation and comparison of measurements between different studies.     

Novel Experimental Method to Determine the Cutting Effectiveness of Grinding Grits

This work presents a novel experimental apparatus to determine the cutting effectiveness of grinding grits. The apparatus consists of a custom high-speed scratch tester, a force measurement system, and an offline 3D optical profilometer. Preliminary results based on a spherical tool are presented to demonstrate the usefulness of the system. Experiments were performed at depths of cut ranging from 0.3 μm to 7.5 μm at cutting speeds of 5 m/s to 30 m/s in 5 m/s increments. High resolution scans of the scratch profiles provided insight into the change in the cutting mechanics as the depth of cut and cutting speed were increased. In general, lower cutting speeds produced higher pile-up heights while higher cutting speeds produced lower pile-up heights. The force measurements indicated that the normal forces increased with cutting speed due to strain rate hardening of the workpiece material while the tangential forces decreased with cutting speed due to a reduction in the coefficient of friction and a change in the cutting mechanics. The force ratio data and the specific energy data both demonstrated high slopes at low depths of cut due to asperity contact between the tool and the workpiece. The modular nature of the developed system allows different grit geometries to be investigated.     

Gluten fragment detection with a competitive ELISA

The second generation of a competitive ELISA for prolamin quantification based on the R5 antibody was studied for method performance and suitability to detect partially hydrolyzed prolamins in food. To be able to convert signal intensities to gluten concentrations, as required by the Codex Alimentarius Standard, a new calibrator consisting of a peptic-tryptic digest of wheat, rye, and barley prolamins was used for the first time. LOD and LOQ of the assay were 1.36 and 5.0 mg prolamin/kg food, respectively. Analysis of beer samples and a hydrolyzed wheat product showed that the assay provided significantly higher prolamin concentrations, compared to the sandwich ELISA based on the same antibody, which is only suitable for the detection of intact prolamins. Spiking experiments with defined concentrations of partially hydrolyzed prolamins gave recoveries ranging from 92 to 136%.     

Centrifugal precipitation chromatography,a powerful technique for the isolation of active enzymes from tea leaves (Camellia sinensis)

Centrifugal precipitation chromatography was developed approximately 10 years ago. In contrast to other counter-current chromatographic techniques, the centrifugal precipitation chromatography system is operated with two mutually miscible solutions separated by a cut-off membrane. Centrifugal precipitation chromatography was firstly introduced for the separation of proteins using an ammonium sulfate gradient. In this study we describe a novel approach using solvent-based protein precipitation for the isolation of active plant enzymes from tea leaves (Camellia sinensis) by centrifugal precipitation chromatography. We developed a gradient based on acetone and Tris-buffer, because the biological activity of carotenases in tea leaves cannot be preserved in the presence of ammonium sulfate. Parameters such as the critical solvent concentration, flow rate, buffer concentration, and sample load were determined and/or optimized. Subsequently, the newly developed separation protocol was successfully used for the isolation of active carotenoid cleavage enzymes from tea leaves. The isolated enzymes showed high enzymatic activities and purities and could be directly used for enzymatic assays and structure elucidation.     

Spatial and temporal distribution of γH2AX fluorescence in human cell cultures following synchrotron‐generated X‐ray microbeams: lack of correlation between persistent γH2AX foci and apoptosis

Formation of γH2AX foci (a marker of DNA double‐strand breaks), rates of foci clearance and apoptosis were investigated in cultured normal human fibroblasts and p53 wild‐type malignant glioma cells after exposure to high‐dose synchrotron‐generated microbeams. Doses up to 283 Gy were delivered using beam geometries that included a microbeam array (50 µm wide, 400 µm spacing), single microbeams (60–570 µm wide) and a broad beam (32 mm wide). The two cell types exhibited similar trends with respect to the initial formation and time‐dependent clearance of γH2AX foci after irradiation. High levels of γH2AX foci persisted as late as 72 h post‐irradiation in the majority of cells within cultures of both cell types. Levels of persistent foci after irradiation via the 570 µm microbeam or broad beam were higher when compared with those observed after exposure to the 60 µm microbeam or microbeam array. Despite persistence of γH2AX foci, these irradiation conditions triggered apoptosis in only a small proportion (<5%) of cells within cultures of both cell types. These results contribute to the understanding of the fundamental biological consequences of high‐dose microbeam irradiations, and implicate the importance of non‐apoptotic responses such as p53‐mediated growth arrest (premature senescence).     

Synthesis and thermolysis of tetrasubstituted cyclopropenes

Photolysis of 5-benzyl-2-methoxy-2,5-dimethyl-³-1, 3,4-oxadiazoline and of the 5,5-dibenzyl analogue with 300-nm light afforded 1-phenyl-2-diazopropane and 1,3-diphenyl-2-diazopropane, respectively. The diazoalkanes were intercepted, in situ, with dimethyl acetylenedicarboxylate to afford 3-benzyl-4,5-bis(methoxycarbonyl)-3-methyl-3H-pyrazole and 3,3-dibenzyl-4,5-bis(methoxycarbonyl)-3H-pyrazole, respectively. Those pyrazoles are short-lived under the reaction conditions and undergo two major reactions. Photolysis prior to rearrangement affords the corresponding 3,3-dialkyI-1,2-bis(methoxycarbonyl)-cyclopropenes. Thermal 1,5-benzyl migration converts the two 3H-pyrazoles in part into the corresponding 4H-pyrazoles, which undergo photolysis to 2,3-dialkyl-1,3-bis(methoxycarbonyl)cyclopropenes.Thermolysis of the 3,3-dialkyl-1,2-bis(methoxycarbonyl) cyclopropenes affords conjugated dienes, presumably through the sequence cyclopropene vinyl carbene diene. The stereochemistry of the dienes was determined and a mechanism consistent with that stereochemistry is proposed.The 2,3-dialkyl-1,3-bis(methoxycarbonyl)cyclopropanes are very stable under conditions that convert isomeric 3,3-dialkyl-1,2-bis(methoxycarbonyl)cyclopropenes to conjugated dienes. It is proposed that the effect of substitution pattern on the thermolysis rate constants is the result of combined ground state and transition state factors.     

Cellular Response to Reagent‐Free Electron‐Irradiated Gelatin Hydrogels

As a biomaterial, it is well established that gelatin exhibits low cytotoxicity and can promote cellular growth. However, to circumvent the potential toxicity of chemical crosslinkers, reagent‐free crosslinking methods such as electron irradiation are highly desirable. While high energy irradiation has been shown to exhibit precise control over the degree of crosslinking, these hydrogels have not been thoroughly investigated for biocompatibility and degradability. Here, NIH 3T3 murine fibroblasts are seeded onto irradiated gelatin hydrogels to examine the hydrogel's influence on cellular viability and morphology. The average projected area of cells seeded onto the hydrogels increases with irradiation dose, which correlates with an increase in the hydrogel's shear modulus up to 10 kPa. Cells on these hydrogels are highly viable and exhibits normal cell cycles, particularly when compared to those grown on glutaraldehyde crosslinked gelatin hydrogels. However, proliferation is reduced on both types of crosslinked samples. To mimic the response of the hydrogels in physiological conditions, degradability is monitored in simulated body fluid to reveal strongly dose‐dependent degradation times. Overall, given the low cytotoxicity, influence on cellular morphology and variability in degradation times of the electron irradiated gelatin hydrogels, there is significant potential for application in areas ranging from regenerative medicine to mechanobiology.

     

Scaling of polymers in aligned rods

We study the behavior of self-avoiding polymers in a background of infinitely long vertically aligned rods that are either frozen in random positions or free to move horizontally. We find that in both cases the polymer chains are highly elongated, with vertical and horizontal size exponents that differ by a factor of 3. Though these results are different than previous predictions, our results are confirmed by detailed computer simulations.