Instability criteria for steady flows of a perfect fluid

An instability criterion based on the positivity of a Lyapunov-type exponent is used to study the stability of the Euler equations governing the motion of an inviscid incompressible fluid. It is proved that any flow with exponential stretching of the fluid particles is unstable. In the case of an arbitrary axisymmetric steady integrable flow, a sufficient condition for instability is exhibited in terms of the curvature and the geodesic torsion of a stream line and the helicity of the flow.     

Two new standard reference materials for the determination of drugs of abuse in human hair

Two new standard reference materials (SRM) for drugs of abuse in human hair have been developed. SRM 2379 consists of hair spiked with cocaine, benzoylecgonine, cocaethylene, phencyclidine, amphetamine, and methamphetamine. SRM 2380 consists of hair spiked with codeine, morphine, monoacetylmorphine, and tetrahydrocannabinol (THC). The SRMs were prepared by soaking the hair in a solution of the target analytes in water-dimethylsulfoxide. The concentration of each analyte was determined using two methods, one based upon gas chromatography/mass spectrometry (GC/MS) and one based upon liquid chromatography/mass spectrometry (LC/MS). Both methods used 0.1 M HCl for extraction of all the analytes from the hair, except for THC, which was extracted with 1 M NaOH. For isolation of the analytes from the extracts, the GC/MS-based methods used different clean-up procedures from those used for the LC/MS-based methods. The results from the two methods were in good agreement with mean differences for the analytes ranging from 4% to 16%. These materials will enable laboratories performing analyses of hair for drugs of abuse to test the accuracy of their methods.     

α-CGRP disrupts amylin fibrillization and regulates insulin secretion: implications on diabetes and migraine

Despite being relatively benign and not an indicative signature of toxicity, fibril formation and fibrillar structures continue to be key factors in assessing the structure–function relationship in protein aggregation diseases. The inability to capture molecular cross-talk among key players at the tissue level before fibril formation greatly accounts for the missing link toward the development of an efficacious therapeutic intervention for Type II diabetes mellitus (T2DM). We show that human α-calcitonin gene-related peptide (α-CGRP) remodeled amylin fibrillization. Furthermore, while CGRP and/or amylin monomers reduce the secretion of both mouse Ins1 and Ins2 proteins, CGRP oligomers have a reverse effect on Ins1. Genetically reduced Ins2, the orthologous version of human insulin, has been shown to enhance insulin sensitivity and extend the life-span in old female mice. Beyond the mechanistic insights, our data suggest that CGRP regulates insulin secretion and lowers the risk of T2DM. Our result rationalizes how migraine might be protective against T2DM. We envision the new paradigm of CGRP : amylin interactions as a pivotal aspect for T2DM diagnostics and therapeutics. Maintaining a low level of amylin while increasing the level of CGRP could become a viable approach toward T2DM prevention and treatment.

CGRP concentration is elevated in migraine conditions. The protective effect of migraine against type 2 diabetes is attributed to the ability of CGRP to remodel human amylin aggregation and to suppress the secretion of mouse insulin 2 (the orthologue of human insulin).     

Determination of ochratoxin A in currants, raisins, sultanas, mixed dried fruit, and dried figs by immunoaffinity column cleanup with liquid chromatography: interlaboratory study

An interlaboratory study was performed on behalf of the Food Standards Agency to evaluate the effectiveness of an affinity column cleanup liquid chromatographic (LC) method for the determination of ochratoxin A in a variety of dried fruit at European regulatory limits. To ensure homogeneity before analysis, laboratory samples are normally slurried with water in the ratio of 5 parts fruit to 4 parts water, and test materials in this form were used in the study. The test portion was extracted with acidified methanol. The extract was filtered, diluted with phosphate-buffered saline, and applied to an affinity column. The column was washed and ochratoxin A was eluted with methanol. Ochratoxin A was quantified by reversed-phase LC. The use of post-column pH shift to enhance the fluorescence of ochratoxin A by the addition of 1.1 M ammonia solution to the column eluant is optional. Determination was by fluorescence. Currants, sultanas, raisins, figs, and mixed fruit (comprising dried pineapple, papaya, sultanas, prunes, dates, and banana chips), both naturally contaminated and blank (very low level), were sent to 24 collaborators in 7 European countries. Participants were asked to spike test portions of all test samples at a level equivalent to 5 ng/g ochratoxin A. Average recoveries ranged from 69 to 74%. Based on results for 5 naturally contaminated test samples (blind duplicates) the relative standard deviation for repeatability (RSDr) ranged from 4.9 to 8.7%, and the relative standard deviation for reproducibility (RSDR) ranged from 14 to 28%. The method showed acceptable within- and between-laboratory precision for all 5 matrixes, as evidenced by HORRAT values <1.3.     

Recoil energy distributions for dissociation of the van der Waals molecule p-difluorobenzene-Ar with 450-3000 cm(-1) excess energy

Velocity map imaging has been used to measure the distributions of translational energy released in the dissociation of p-difluorobenzene-Ar van der Waals complexes from the 5(1), 3(1), 5(2), 3(1)5(1), 5(3), 3(2), and 3(2)5(1) states. These states span 818-3317 cm(-1) of vibrational energy and correspond to a range of energies above dissociation of 451-2950 cm(-1). The translational energy release (recoil energy) distributions are remarkably similar, peaking at very low energy (10-20 cm(-1)) and decaying in an exponential fashion to approach zero near 300 cm(-1). The average translational energy released is small, shows no dependence on the initial vibrational energy, and spans the range 58-72 cm(-1) for the vibrational levels probed. The average value for the seven levels studied is 63 cm(-1). The low fraction of transfer to translation is qualitatively in accord with Ewing's momentum gap model [G. E. Ewing, Faraday Discuss. 73, 325 (1982)]. No evidence is found in the distributions for a high energy tail, although it is likely that the experiment is not sufficiently sensitive to detect a low fraction of transfer at high translational energies. The average translational energy released is lower than has been seen in comparable systems dissociating from triplet and cation states.     

A note on the numerical evaluation of finite integrals of oscillatory functions

A method is described for the numerical evaluation of integrals of the form ∫ _?1 ¹ f(x)K(m,x)dx, wheref(x) is smooth in [?1,1], whileK(m,x) is highly oscillatory for large values ofm.     

Wind-generated ambient noise in a topographically isolated basin: a pre-industrial era proxy

During the mid-1980s, calibrated measurements of ambient noise and wind speed were made in the Tongue of the Ocean in the Bahamas to quantify the spectra and statistics of wind-generated noise. This deep basin is topographically isolated from the Atlantic Ocean and, therefore, largely acoustically decoupled from the Atlantic Ocean deep sound channel. The quantitative effects of contaminating (non-surface wind-generated) noise sources within the basin were eliminated by careful measurement and robust statistical analysis methodologies. Above 500 Hz, the spectral slopes are approximately -5 dB per octave and independent of wind speed. Below 500 Hz, the ambient noise is no longer a linear function of wind speed. Below 100 Hz and for wind speeds greater than 18.5 knots (kt), the ambient noise is independent of frequency. The minimum observed ambient noise level falls 13 dB below Urick's "light shipping" level at 30 Hz and 2-5 dB below Wenz's sea state zero level through the wind-dominated portion of the spectrum. The basin's geographical isolation and the rigorous measurement and analysis methodologies employed make this two-decade-old data set a reasonable and justified proxy for pre-industrial era ocean noise levels in the 20 Hz to 20 kHz frequency band.     

Interfacial synthesis of bisphenol A tetrachlorocyclotriphosphazene from bisphenol A and hexachlorocyclotriphosphazene

The effect of solvent purity on the synthesis and yield of bisphenol A tetrachlorocyclotriphosphazene (BATCCP) has not been described in the literature. The purpose of this research was to synthesize BATCCP hybrid monomers and to evaluate the effect of solvent purity on the BATCCP production. BATCCP monomers were prepared by an interfacial procedure in a water/toluene system as a function of time with the assistance of a phase transfer catalyst, tetraoctylammonium bromide. ¹H and ³¹P NMR confirmed the production of BATCCP monomer by the appearance of chemical shifts at 7.18 and 5.35 ppm in the ¹H NMR and 23.4 and 13.9 ppm in the ³¹P NMR, respectively. Distillation of the toluene, not suggested in previous reports of HCCP hybrid synthesis, resulted in an improvement of actual % yield to 40% and stability of the product throughout the 1440 min reaction as confirmed by MALDI, compared with an 11% actual yield at 15 min, decaying to 2% over a 1440 min reaction when the synthesis was performed with ‘anhydrous toluene’ as provided commercially without further distillation.