A biologically motivated solution to the cocktail party problem.

We present a new approach to the cocktail party problem that uses a cortronic artificial neural network architecture (Hecht-Nielsen, 1998) as the front end of a speech processing system. Our approach is novel in three important respects. First, our method assumes and exploits detailed knowledge of the signals we wish to attend to in the cocktail party environment. Second, our goal is to provide preprocessing in advance of a pattern recognition system rather than to separate one or more of the mixed sources explicitly. Third, the neural network model we employ is more biologically feasible than are most other approaches to the cocktail party problem. Although the focus here is on the cocktail party problem, the method presented in this study can be applied to other areas of information processing.     

Functional beta-cell mass after transplantation of human fetal pancreatic cells: differentiation or proliferation?

The absolute wavenumbers for 36 lines of the 3-0 band of 12C16O are measured from P(17) at 6271 cm-1 to R(19) at 6405 cm-1, with an uncertainty of about +/-3 x 10(-5) cm-1 (about +/-1 MHz). The experimental positions are compared with the best predicted positions from recent Dunham coefficients. Self-induced pressure lineshifts are determined and reach, at most, about -8 x 10(-3) cm-1 atm-1. Copyright 1997 Academic Press. Copyright 1997Academic Press     

Catalytic Oxidation of Ethene on Polycrystalline Palladium: Influence of the Oxidation State of the Surface

¹³C DEPT-MRI is used to provide the first spatial mapping of alkene isomerisation and hydrogenation during an alkene hydrogenation reaction occurring within a trickle-bed reactor. The implementation of a pulse sequence combining the spatial resolution of a magnetic resonance imaging (MRI) pulse sequence with a ¹³C DEPT magnetic resonance spectroscopy pulse sequence enables spatially resolved ¹³C spectra to be recorded of natural abundance ¹³C species. Observation of the ¹³C nucleus, which has a much larger chemical shift range than the ¹H nucleus, provides spectra from which direct identification of the products of isomerisation and hydrogenation is achieved. This technique is illustrated with respect to the hydrogenation of 1-octene over a 1 wt% Pd/Al₂O₃ catalyst. In this preliminary study we demonstrate the ability of this technique to identify the effect of changing the hydrogen flow rate on the evolution of isomerisation and hydrogenation processes occurring along the length of the bed.     

Reduced progression of atherosclerosis in apolipoprotein E-deficient mice following consumption of red wine, or its polyphenols quercetin or catechin, is associated with reduced susceptibility of LDL to oxidation and aggregation

The effect of consuming red wine, or its major polyphenol constituents catechin or quercetin, on the development of atherosclerotic lesions, in relation to the susceptibility of plasma LDL to oxidation and to aggregation, was studied in atherosclerotic apolipoprotein E deficient (E degree) mice. Forty E degree mice at the age of 4 weeks were divided into four groups, 10 mice in each group, and were supplemented for up to 6 weeks in their drinking water with placebo (1.1% alcohol); catechin or quercetin (50 micrograms/d per mouse), or red wine (0.5 mL/d per mouse). Consumption of catechin, quercetin, or red wine had no effect on plasma LDL or HDL cholesterol levels. The atherosclerotic lesion area was smaller in the treated mice by 39%, 46%, and 48%, respectively, in comparison with E degree mice that were treated with placebo. In accordance with these findings, cellular uptake of LDL derived after catechin, quercetin, or red wine consumption was found to be reduced by 31%, 40%, and 52%, respectively. These results were associated with reduced susceptibility to oxidation (induced by different modes such as copper ions, free radical generator, or macrophages) of LDL isolated after red wine or quercetin and, to a lesser extent after catechin consumption, in comparison with LDL isolated from the placebo group. Similar results were obtained when LDL was preincubated in vitro with red wine or with the polyphenols prior to its oxidation. Even in the basal oxidative state (not induced oxidation), LDL isolated from E degree mice that consumed catechin, quercetin, or red wine for 2 weeks was found to be less oxidized in comparison with LDL isolated from E degree mice that received placebo, as evidenced by 39%, 48%, and 49% reduced content of LDL-associated lipid peroxides, respectively. This effect could be related to enhanced serum paraoxonase activity in the polyphenol-treated mice. LDL oxidation was previously shown to lead to its aggregation. The present study demonstrated that the susceptibility of LDL to aggregation was reduced in comparison with placebo-treated mice, by 63%, 48%, or 50% by catechin, quercetin, and red wine consumption, respectively, and this effect could be shown also in vitro. The inhibition of LDL oxidation by polyphenols could be related, at least in part, to a direct effect of the polyphenols on the LDL, since both quercetin and catechin were found to bind to the LDL particle via the formation of an ether bond. We thus conclude that dietary consumption by E degree mice of red wine or its polyphenolic flavonoids quercetin and, to a lesser extent, catechin leads to attenuation in the development of the atherosclerotic lesion, and this effect is associated with reduced susceptibility of their LDL to oxidation and aggregation.     

Deletion of amino acids 1641-2437 from the foot region of skeletal muscle ryanodine receptor alters the conduction properties of the Ca release channel

The ryanodine receptor (RyR) of skeletal muscle contains two functional domains: a carboxyl-terminal hydrophobic domain that forms the putative conduction pore of the calcium release channel, and a large cytoplasmic domain that corresponds to the "foot structure." To understand the contribution of the foot structure to the function of the calcium release channel, we studied a RyR deletion mutant, delta(1641-2437)-RyR, in which a region that is rich in glutamate and aspartate residues (a.a. 1641-2437) was removed. The wild-type and delta(1641-2437)-RyR proteins were expressed in a Chinese hamster ovary (CHO) cell line, and functions of single calcium release channels were measured in the lipid bilayer membrane. The wild-type RyR forms functional calcium release channels with a linear current-voltage relationship similar to that of the native channel identified in the sarcoplasmic reticulum membrane of skeletal muscle, whereas the channels formed by delta(1641-2437)-RyR exhibit significant inward rectification, i.e., currents moving from cytoplasm into SR lumen were approximately 20% less than that in the opposite direction. As in to the wt-RyR channel, opening of the delta(1641-2437)-RyR channel has a bell-shaped dependence on the cytoplasmic calcium, but the calcium-dependent activation and inactivation processes of the delta(1641-2437)-RyR channel are shifted to higher calcium concentrations. Our data show that deletion of a.a. 1641-2437 from the foot region of the skeletal muscle RyR results in changes in both ion conduction and calcium-dependent regulation of the calcium release channel.     

"Whiplash" injury of the cervical spine: value of modern diagnostic imaging

"Whiplash injuries" are frequent sequelae of motor vehicle accidents. While conventional imaging methods such as X-ray, including special and functional lateral projections, continue to be the first-choice evaluation methods, they frequently do not reveal injuries to the soft tissues. Cross-sectional methods such as CT and MRT may therefore be indicated for further workup in given clinical situations. In this paper the role of the entire spectrum of imaging methods is reviewed. Emphasis is placed on so-called functional CT, which allows detection of rotational instabilities of the upper cervical spine. These are difficult to evaluate clinically or by standard imaging studies, yet they may be a frequent cause of chronic whiplash syndrome. Furthermore, some results of morphologic studies of the alar ligaments by MRT are presented. Although experience to date is limited, it is likely that MRT of the occipitocervical junction region due to its potential to reveal exquisite anatomical detail, will gain in importance in the future.     

Behavior of blended cement mortars exposed to sulfate solutions cycling in relative humidity

In recent years, several cases of damage to concrete structures due to sulfate exposure have occurred essentially in the above ground parts of structures. Such distress, often characterized by white efflorescence and surface scaling, is driven by salt crystallization in pores and/or repeated reconversions of certain sulfates between their anhydrous and hydrated forms under cycling temperature and relative humidity (RH). However, the effect of the water/cementitious materials ratio (w/cm), pozzolanic additions, and other parameters on the durability of cement-based materials under such exposure conditions is still misunderstood. In this study, 12 cement mortars having different w/cm (0.30, 0.45, and 0.60) and made with ordinary portland cement (OPC) or OPC incorporating 8% silica fume, 25% class F fly ash, or 25% blast furnace slag were made. Standard bars from each of these mortars were submerged in both 10% magnesium sulfate (MgSO₄) and 10% sodium sulfate (Na₂SO₄) solutions; their expansion and surface degradation was monitored for up to 9 months. In addition, cylinders made from these 12 mortars were partially submerged in 50-mm-deep 10% MgSO₄ and 10% Na₂SO₄ solutions. Half of the cylinders were maintained under constant temperature and RH, whereas the others were subjected to cycling RH. The effect of the w/cm and mineral additions on the classic chemical sulfate attack and development of efflorescence was investigated, and the results are discussed in this article.