Mechanism of action of pulsed high electric field (PHEF) on the membranes of food-poisoning bacteria is an 'all-or-nothing' effect

Salmonella typhimurium (CRA 1005) was more sensitive than Listeria monocytogenes (NCTC 11994) to pulsed high electric field (PHEF) treatment in distilled water (10, 15 and 20 kV/cm), 10 mM tris-maleate buffer pH 7.4 (15 kV/cm) and model beef broth (0.75% w/v: 15 kV/cm). Sublethal injury could not be detected using a selective medium plating technique, indicating that bacterial inactivation by PHEF may be an 'all-or-nothing' event. PHEF-induced membrane permeabilization resulted in increased UV-leakage and a decreased ability of L. monocytogenes to maintain a pH gradient.     

Point-tracked quantitative analysis of left ventricular surface motion from 3-D image sequences

We propose and validate the hypothesis that we can use differential shape properties of the myocardial surfaces to recover dense field motion from standard three-dimensional (3-D) image sequences (MRI and CT). Quantitative measures of left ventricular regional function can be further inferred from the point correspondence maps. The noninvasive, algorithm-derived results are validated on two levels. First, the motion trajectories are compared to those of implanted imaging-opaque markers of a canine model in two imaging modalities, where subpixel accuracy is achieved. Second, the validity of using motion parameters (path length and thickness changes) for detecting myocardial injury area is tested by comparing algorithms derived results to postmortem analysis TTC staining of myocardial tissue, where the achieved Pearson product-moment correlation value is 0.968.     

The effects of phase control materials on hand skin temperature within gloves of soccer goalkeepers

In soccer, goalkeepers routinely wear gloves that may restrict heat loss from the hands and cause thermal discomfort. In order to alleviate this problem phase control materials (PCMs) have been incorporated into gloves to reduce heat load inside the glove, thereby maintaining a comfortable temperature. The aim of this study was to assess the efficacy of these materials during a simulation of goalkeeping activities. Seven subjects carried out two sessions of goalkeeper-specific exercise on a non-motorized treadmill, one session with a PCM glove and one session with a normal foam material glove (NFM). All sites of skin temperature measurement, except mean whole-body skin temperature, showed uniformly that the PCM glove caused a greater increase in skin temperature of the hand compared to the NFM glove. These results suggest that this particular specification of PCM promotes heat gain rather than heat loss and is therefore inappropriate to enhance thermal comfort in this setting.     

New support vector algorithms

We propose a new class of support vector algorithms for regression and classification. In these algorithms, a parameter nu lets one effectively control the number of support vectors. While this can be useful in its own right, the parameterization has the additional benefit of enabling us to eliminate one of the other free parameters of the algorithm: the accuracy parameter epsilon in the regression case, and the regularization constant C in the classification case. We describe the algorithms, give some theoretical results concerning the meaning and the choice of nu, and report experimental results.     

Hydroquinone as a buffer additive for suppression of bubbles formed by electrochemical oxidation of the CE buffer at the outlet electrode in capillary electrophoresis/electrospray ionization-mass spectrometry

Hydroquinone was found to suppress bubble formation at the outlet electrode of a sheathless capillary electrophoresis/electrospray ionization-mass spectrometer by replacing the oxidation of water (2H2O(1)<-->O2(g) + 4H+ + 4e) with that of more easily oxidized hydroquinone (hydroquinone<-->p-benzoquinone + 2H+ + 2e). Formation of p-benzoquinone replaces the formation of oxygen gas, effectively suppressing gas bubble formation. Several electrode materials, including platinum, gold-coated stainless steel, and stainless steel wires, were tested. However, hydroquinone suppressed bubbles only at the platinum electrode. Combination of the in-capillary electrode sheathless interface using platinum wire, hydroquinone as a buffer additive, and pressure programming at the inlet of the capillary electrophoresis provided a rugged high efficiency interface for analysis of protein digests using CE/ESI-MS.     

Characteristics of acoustic plate modes on rotated Y-cuts of quartz utilized for biosensing applications

Acoustic plate modes (APM) on various quartz substrates have been investigated in order to determine their usefulness for liquid-sensing applications. The modes have been characterized in terms of their mass sensitivity, mode separation, temperature sensitivity, and reproducibility of the experimental results. Promising characteristics are found for rotated Y-cuts of quartz with the direction of acoustic mode propagation being perpendicular to the X-axis of the quartz crystal. Experiments on the detection of immunochemical reactions are performed using different quartz APM sensors, and the results are compared to similar experiments utilizing APM devices on ZX-LiNbO3.     

Column performance and stability for high-speed vacuum-outlet GC of volatile organic compounds using atmospheric pressure air as carrier gas

The development of lightweight, portable GC instrumentation is handicapped by the need for compressed carrier gas to drive the separation. The use of air as carrier gas eliminates the need for compressed gas tanks. If a vacuum pump is used to pull carrier gas and injected samples through the column, atmospheric pressure air can be used as carrier gas. Vacuum outlet operation also improves performance for high-speed separations by reducing detector dead time and by shifting optimal carrier gas velocity to higher values. Under vacuum outlet conditions using atmospheric pressure air as carrier gas, a 6-m-long, 0.25-mm-i.d. capillary column can generate approximately 12,500 theoretical plates, and a 12-m-long column can generate approximately 44,000 plates but with a 3-4-fold increase in separation time. The principal issues in column selection for high-speed GC with air as a carrier gas are efficiency and stability. Several bonded and nonbonded stationary phases were evaluated for use with air as carrier gas in the analysis of volatile organic compounds of interest in airmonitoring applications. These include dimethylpolysiloxane, 50% phenyl-50% methyl polysiloxane, 50% cycanopropylphenyl-50% methyl polysiloxane, trifluoropropyl polysiloxane, poly(ethylene glycol), and dicyanoallyl polysiloxane (nonbonded). The dimethyl polysiloxane and the trifluoropropyl polysiloxane columns showed good efficiency and no significant deterioration after 5 days of continuous operation with air as carrier gas. The 50% phenyl-50% methyl polysiloxane and the 50% cycanopropylphenyl-50% methyl polysiloxane columns showed poorer efficiency, and the poly(ethylene glycol) and dicyanoallyl polysiloxane columns showed excessive deterioration in air.     

Influence of melting and rheological properties of fatty binders on the melt granulation process in a high-shear mixer

The preparation of granules by melt granulation was investigated using a laboratory-scale high-shear mixer (Pellmix PL 1/8) and binary mixtures containing lactose and different lipidic binders, namely, Compritol® 888, Cutina® HR, or Precirol® ATO5. During the process, the product temperature and the impeller motor power consumption were monitored. On the other hand, the melting behavior (thermal analysis) and the rheological properties (controlled stress capillary rheometer) of the different lipophilic binders were also determined. The granule formation was shown to be quite effective at product temperatures even below the melting point of the lipidic binder, that is, when the binder is sufficiently softened to be deformed by the very high shearing forces developed in the high-shear mixer. On the other hand, the performance of lipidic binders during the melt granulation process was shown to be closely dependent on their melting and rheological properties. The granule growth rate was shown to be higher when the binder melting range is narrow and the influence of temperature on the viscosity of the unmelted product is high.     

Interfacial bond strength of electrophoretically deposited hydroxyapatite coatings on metals

Hydroxyapatite (HAp) coatings were deposited onto substrates of metal biomaterials (Ti, Ti6Al4V, and 316L stainless steel) by electrophoretic deposition (EPD). Only ultra-high surface area HAp powder, prepared by the metathesis method 10Ca(NO₃)₂ + 6(NH₄)₂HPO₄ + 8NH₄OH), could produce dense coatings when sintered at 875–1000°C. Single EPD coatings cracked during sintering owing to the 15–18% sintering shrinkage, but the HAp did not decompose. The use of dual coatings (coat, sinter, coat, sinter) resolved the cracking problem. Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) inspection revealed that the second coating filled in the valleys in the cracks of the first coating. The interfacial shear strength of the dual coatings was found, by ASTM F1044-87, to be 12 MPa on a titanium substrate and 22 MPa on 316L stainless steel, comparing quite favorably with the 34 MPa benchmark (the shear strength of bovine cortical bone was found to be 34 MPa). Stainless steel gave the better result since -316L (20.5 m mK^-1) > -HAp (14 m mK^-1), resulting in residual compressive stresses in the coating, whereas -titanium (10.3 m mK^-1) < -HAp, resulting in residual tensile stresses in the coating. © 1999 Kluwer Academic Publishers