A new methodology for studying the performance of products against ruminal acidosis

This paper describes a new and convenient methodology for studying the performance of products used in the treatment of ruminal acidosis. The method is based on potentiometric titration of the increase in buffer capacity and acid consuming capacity after the addition of products to a suitable medium at physiological rumen pH values. The testing medium is a mixture of buffer substances (phosphate, maleate and volatile fatty acids) that mimics real ruminal fluid in chemical composition, pH and temperature, providing useful experimental results allowing easy testing of antacids. This methodology was applied to the testing of four raw materials (sodium bicarbonate, two calcium carbonates and magnesium oxide). Results in good agreement with theoretical predictions and field experience were obtained. Copyright © 2003 Society of Chemical Industry     

Colistin Resistance in Aeromonas spp.

The increase in the use of antimicrobials such as colistin for the treatment of infectious diseases has led to the appearance of Aeromonas strains resistant to this drug. However, resistance to colistin not only occurs in the clinical area but has also been determined in Aeromonas isolates from the environment or animals, which has been determined by the detection of mcr genes that confer a resistance mechanism to colistin. The variants mcr-1, mcr-3, and mcr-5 have been detected in the genus Aeromonas in animal, environmental, and human fluids samples. In this article, an overview of the resistance to colistin in Aeromonas is shown, as well as the generalities of this molecule and the recommended methods to determine colistin resistance to be used in some of the genus Aeromonas.     

Relationseips Between Drug Dissolution Profile and Gelling Agent Viscosity in Tablets Prepared with Hydroxypropylmethylcellulose (HPMC) and Sodium Carboxymethylcellulose (NaCMC) Mixtures

Two varieties of HPMC, two varieties of NaCMC and various HPMC/NaCMC mixtures were characterized with the aim of providing a sound basis for the selection of appropriate mixtures to use as gelling agents in controlled-release tablets for hydrosoluble drugs. For both HPMC and NaCMC, one variety was of high and the other of low nominal viscosity. We also investigated possible relationships between the rheological properties of HPMC/NaCMC mixtures and atenolol release from tablets prepared with such mixtures. The mean molecular weights of each polymer variety were estimated on the basis of determination of their intrinsic viscosities in aqueous dispersions. Rotational viscosimetry of 2% aqueous dispersions of the polymers and polymer mixtures revealed rheological synergism in some mixtures. Drug dissolution trials were carried out in water and 0.1 N HCl. Dissolution medium, gelling agent composition and proportion of gelling agent in the tablet all affected dissolution profiles. Fitting of Korsmeyer et al.'s equation to the data for dissolution in water indicated zero-order dissolution kinetics for all formulations. For tablets prepared with the most viscous HPMC variety, %hour dissolution efficiency was closely correlated with the apparent viscosity (shear rate 0.5 s^-1) of the aqueous dispersion of the polymer mixture used as gelling agent. Assays of tablet erosion rates indicated that the erosion mechanism may contribute to the observed zero-order dissolution kinetics, but that other factors are probably also involved.     

Differences in the UV-crosslinking patterns of the poliovirus 5''-untranslated region with cell proteins from poliovirus-susceptible and -resistant tissues

Specific polyclonal antibody was raised against D-aspartate (D-Asp) which had been conjugated to glutaraldehyde and was purified by affinity chromatography. Immunohistochemical staining of rat pineal gland with the antibody demonstrated the presence of D-Asp in the cytoplasm of pinealocytes, the predominant cell type in this gland. D-Asp immunoreactivity was more evident in the distal region than in the proximal region of the gland. Pinealocytes in the distal region are presumably involved in the synthesis and secretion of the pineal hormone, melatonin, and the results of staining may indicate some yet unknown role of D-Asp in the regulation of melatonin secretion.     

Collisional Probing of the Transition-State Structure of a Bimolecular Reaction

The total cross section σ_B(E) for the Ca(¹D) + HBr → CaBr(B²Σ⁺) + H reaction as a function of collision energy has been measured using crossed atomic and molecular beams. The maxima exhibited by σ_B(E) with increasing energy are attributed to the opening of successive bending vibrational reaction channels that proceed via a [Ca(¹D) ⃛ Br ⃛ H]^‡ transition state. A dynamical model for the reaction may be constructed in terms of Landau-Zener probabilities for curve crossing at two locations on the reaction path, coupled with a preference for consumption of transition-state vibrational energy.     

Evaluation of ACE inhibitory activity of dipeptides generated by the action of porcine muscle dipeptidyl peptidases

Dipeptidyl peptidases (DPP) constitute a group of proteolytic enzymes able to release a good number of dipeptides from the N-terminus of both synthetic substrates and natural polypeptides. Specific sequences generated by the action of DPP purified from porcine skeletal muscle have been assayed to evaluate their capacity to inhibit the activity of angiotensin-I converting enzyme (ACE; EC 3.4.15.1). A fluorimetric assay based on the hydrolysis of the internally quenched fluorescent substrate o-aminobenzoylglycyl-p-nitrophenylalanylproline by the action of ACE was used for this purpose. The generated fluorescence of the product (the o-aminobenzoylglycine group) was continuously monitored in a microtiter-plate multiscan fluorometer.     

Low Temperature Direct of Graphene onto Metal Nano‐Spindt Tip with Applications in Electron Emission

Graphene has been known for its superior electronic properties ever since its discovery in 2004. The high aspect ratio and ballistic transport properties exhibited by this one‐dimensional material are especially useful for electron emission applications. However, they are typically grown horizontally and excess efforts, such as the use of transfer techniques, is required to orientate them before effective electron emission from the graphene edges can occur. These transfer techniques have been shown to lead to additional defects to the as‐grown graphene structure, thereby degrading its properties. Here, we present an approach to directly fabricate graphene onto metal nano‐sized spindt tips (or nanocones) using the solid‐state transformation of carbon deposited from a pulsed laser system at low temperature. Besides providing a layer of chemical and mechanical protection for the metal nanocones, the graphene‐on‐metal nanocones gave enhanced emission properties compared to bare metal nanocones. This was due to the reduction of effective field emission tunneling barrier, which was a result of graphene‐metal charge transfer interactions. Controlling the metal nanocones density was also an important factor in determining the field emission performance, as electron screening from neighboring cones should be minimized.     

Inductive modeling of lithium-ion cells

Sandia National Laboratories has conducted a sequence of studies on the performance of lithium ion and other types of electrochemical cells using inductive models. The objectives of some of these investigations are: (1) to develop procedures to rapidly determine performance degradation rates while these cells undergo life tests; (2) to model cell voltage and capacity in order to simulate cell output under variable load and temperature conditions; (3) to model rechargeable battery degradation under conditions of cyclic charge/discharge, and many others. Among the uses for the models are: (1) to enable efficient predictions of battery life; (2) to characterize system behavior.

Inductive models seek to characterize system behavior using experimentally or analytically obtained data in an efficient and robust framework that does not require phenomenological development. There are certain advantages to this. Among these advantages is the ability to avoid making measurements of hard to determine physical parameters or having to understand cell processes sufficiently to write mathematical functions describing their behavior. We have used artificial neural networks (ANNs) for inductive modeling, along with ancillary mathematical tools to improve their accuracy.

This paper summarizes efforts to use inductive tools for cell and battery modeling. Examples of numerical results are presented.