bluuebunny/crossref_metadata_2025_split huggingface dataset:
Physiological and molecular genetic evaluation of the dechlorination agent, pyridine‐2,6‐bis(monothiocarboxylic acid) (PDTC) as a secondary siderophore of Pseudomonas
Authors: Lewis Thomas A. , Leach Lynne , Morales Sergio , Austin Paula R. , Hartwell Hadley J. , Kaplan Benjamin , Forker Cynthia , Meyer Jean‐Marie 
Published: December 2004

SummaryThe bacterial metabolite and transition metal chelator pyridine‐2,6‐dithiocarboxylic acid (PDTC), promotes a novel and effective means of dechlorination of the toxic and carcinogenic pollutant, carbon tetrachloride. Pyridine‐2,6‐dithiocarboxylic acid has been presumed to act as a siderophore in the Pseudomonas strains known to produce it. To explore further the physiological function of PDTC production, we have examined its regulation, the phenotype of PDTC‐negative (pdt) mutants, and envelope proteins associated with PDTC in P. putida strain DSM 3601. Aspects of the regulation of PDTC production and outer membrane protein composition were consistent with siderophore function. Pyridine‐2,6‐dithiocarboxylic acid production was coordinated with production of the well‐characterized siderophore pyoverdine; exogenously added pyoverdine led to decreased PDTC production, and added PDTC led to decreased pyoverdine production. Positive regulation of a chromosomal pdtI‐xylE transcriptional fusion, and of a 66 kDa outer membrane protein (IROMP), was seen in response to exogenous PDTC. Tests with transition metal chelators indicated that PDTC could provide a benefit under conditions of metal limitation; the loss of PDTC biosynthetic capacity caused by a pdtI transposon insertion resulted in increased sensitivity to 1,10‐phenanthroline, a chelator that has high affinity for a range of divalent transition metals (e.g. Fe2+, Cu2+, Zn2+). Exogenously added PDTC could also suppress a phenotype of pyoverdine‐negative (Pvd–) mutants, that of sensitivity to EDDHA, a chelator with higher affinity and specificity for Fe3+. Measurement of 59Fe incorporation showed uptake from 59Fe:PDTC by DSM 3601 grown in low‐iron medium, but not by cells grown in high iron medium, or by the pdtI mutant, which did not show expression of the 66 kDa envelope protein. These data verified a siderophore function for PDTC, and have implicated it in the uptake of transition metals in addition to iron.
Interactions Between Oxcarbazepine and Conventional Antiepileptic Drugs in the Maximal Electroshock Test in Mice: An Isobolographic Analysis
Authors: Luszczki Jarogniew J. , Borowicz Kinga K. , Swiader Mariusz , Czuczwar Stanislaw J. 
Published: December 2004

Summary:  Purpose: The aim of this study was to determine the types of interactions between oxcarbazepine (OCBZ) and conventional antiepileptic drugs (AEDs) against maximal electroshock‐induced seizures (MES test) in mice, by using a method of isobolographic analysis.Methods: Adverse effects of combinations were evaluated in the chimney test (motor performance), also using the isobolographic method, which allowed determination of the median toxic dose (TD50) values for individual combinations; thus the protective indices could be determined.Results: OCBZ and phenytoin (PHT) at the fixed‐ratio combination of 1:1 were significantly infraadditive (antagonistic) with respect to the antiseizure protection against MES and simultaneously additive in terms of side effects in the chimney test. Interestingly, combinations between OCBZ and clonazepam (CZP) in the MES test proved antagonistic or synergistic, depending on the proportion of both AEDs in the mixture. Low doses of OCBZ with high doses of CZP exerted antagonism. Conversely, high doses of OCBZ combined with low doses of CZP resulted in a synergistic interaction. Remaining combinations between OCBZ and phenobarbital, valproate, or carbamazepine were purely additive, either as regards the anticonvulsant activity against MES or in terms of motor impairment in the chimney test.Conclusions: The results of this study indicate that interaction of OCBZ and CZP at fixed‐ratio combination of 1:1 might be profitable from a clinical point of view. Conversely, combinations of OCBZ with PHT may not be clinically efficient.
Pentylenetetrazol‐induced Seizures in Immature Rats Provoke Long‐term Changes in Adult Hippocampal Cholinergic Excitability
Authors: Meilleur Sébastien , Aznavour Nicolas , Descarries Laurent , Carmant Lionel , Mamer Orval A. , Psarropoulou Caterina 
Published: December 2004

Summary:  Purpose: We previously demonstrated that the anticholinesterase eserine provokes interictal‐like discharges in the CA3 area of hippocampal slices from rats in which generalized seizures had been induced by pentylenetetrazol (PTZ) when immature. In this study, we investigated several factors as the possible mechanism for this effect, including age at convulsions.Methods: Rats were injected with PTZ on postnatal day (P) 18–20 or >P60, and neuronal activity was recorded intra‐ and extracellularly from CA3 5–10 or >40 days later. In additional experiments, convulsions were triggered by kainate or were blocked by pentobarbital. Hippocampal (a) acetylcholine (ACh) innervation density was measured by immunocytochemistry, and ACh and γ‐aminobutyric acid (GABA) contents were determined by high‐performance liquid chromatography (HPLC)‐electrospray ionization.Results: The excitatory effect of eserine was the most consistent in slices from rats PTZ‐treated when immature and after the long interval, whereas the reverse was true in rats treated as adults. This effect was dependent on the occurrence of a seizure and was less prevalent when the seizure had been provoked by kainate. Adult animals PTZ‐treated at P20 did not differ from control in (a) poly‐ or monosynaptic GABAA and GABAB CA3 inhibitory postsynaptic potentials (IPSPs); (b) density of ACh innervation; or (c) tissue content of ACh and GABA.Conclusions: A PTZ‐induced generalized seizure in immature rat provokes endogenous ACh‐induced interictal‐like discharges in adult hippocampal CA3. This effect is only transiently observed if the seizure was induced in adult. It does not appear to be related to a change in GABAergic inhibition, in density of ACh innervation, or in ACh or GABA content.
Tooth loss and caries prevalence in very old Swedish people: the relationship to cognitive function and functional ability
Authors: Avlund Kirsten , Holm‐Pedersen Poul , Morse Douglas E. , Viitanen Matti , Winblad Bengt 
Published: December 2004

Objective:  To analyse whether cognitive function and functional ability are related to oral health among community‐dwelling older people over the age of 80 years.Background:  This cross‐sectional study is based on the Kungsholmen Elders Oral Health Survey (KEOHS). The study included oral examinations carried out in two local clinics by standardised examiners and interviews using structured questionnaires.Materials and Methods:  Altogether 159 individuals were included in this study. Coronal caries and root caries were assessed using the National Institute of Dental and Craniofacial Research (NIDCR) diagnostic criteria. Cognitive function was assessed by the Mini‐Mental State Examination (MMSE) index and functional ability was assessed by a global measure of self‐reported changes.Results:  Older adults with a low MMSE score (≤23) tended to have a higher risk of coronal caries than those with higher scores. Participants with mild cognitive decline (MMSE = 24–26) and with a decrease in functional ability had a significantly higher risk of root caries. These associations changed little when adjusted by the covariates. In addition, people with a low MMSE (0–23) had a four times higher risk of not using dental services regularly. This result was unchanged after adjusting for the variables studied.Conclusions:  This study revealed associations between the cognitive and functional status of the individual and aspects of oral health, that may contribute to a deeper understanding of the background of oral health status in older adults.
On the Inertial-Electrostatic Confinement of a Plasma
Authors: Elmore William C. , Tuck James L. , Watson Kenneth M. 
Published: December 2004

A system in which electrons are projected radially inwards from a spherical surface, has been proposed for the confinement of a plasma at thermonuclear temperatures. The equilibrium, economics, and stability of such a system are discussed theoretically.
Although we conclude that it is of doubtful utility as a thermonuclear reactor, it may be possible to produce in this way small regions of thermonuclear plasma for study. The device appears to be unstable at economic densities. The stability is discussed in terms of a virial, which turns out to be mathematically tractable in this geometry.
Thermodynamics of Electrically Conducting Fluids
Authors: Chu Boa-Teh 
Published: December 2004

By consideration of the equations of motion and the electromagnetic theory of a moving medium, the reversible work done on a fluid, per unit mass, in a small change of state is shown to be −pd(1/ρ) + E · d(D/ρ) + H · d(B/ρ), where p is the pressure due to the joint action of the mechanical and electromagnetic changes; ρ is the density; E and B are, respectively, the electric field strength and magnetic induction; D and H are, respectively, the electric and magnetic excitation. Only the nonrelativistic version of Minkowski's theory has been used in this derivation. This formula provides the basis for a complete study of the thermodynamics of fluid medium under the action of both electromagnetic and mechanical changes.
As an application, basic formulas which may be used to calculate the electrocaloric effect, the magnetocaloric effect, and electro- and magnetostriction effects are deduced. In particular, the additional pressure and pondermotive force due to these effects are obtained in a simple manner which, from the thermodynamic point of view, is better than Kortweg and Helmholtz' derivation given in the classical electromagnetic theory. As a second application, the energy equation of magnetohydromechanics is derived. The derivation is more general than previous derivations in that it does not presuppose the form of the electromagnetic constitutive equations (e.g., D = εE, B = μH) which the medium satisfies.
On Certain Properties of Hydromagnetic Shocks
Authors: Ericson W. B. , Bazer J. 
Published: December 2004

Proofs of four basic properties of stationary, planar, nonrelativistic hydromagnetic shocks are presented. These properties are: (P1) the specific entropy behind a hydromagnetic shock exceeds that ahead, if and only if, the shock is compressive; (P2) the specific entropy behind a compressive shock varies in the same sense as the mass flux; (P3) in the region behind (compressive) fast shocks, the fast disturbance speed is greater than the normally directed fluid velocity relative to the shock; (P4) in the region behind (compressive) slow shocks, the slow disturbance speed may be less than, equal to, or greater than the normally directed fluid velocity relative to the shock. The equality holds when the specific entropy and the mass flux assume their maximum values.
In these statements the state in front is assumed fixed and attention is focused on the variation of the state behind with an appropriate shock strength parameter. The proof of P1 is designed especially to cover the case of the slow shock where the dependence of the state behind on the ``natural'' shock-strength parameters is nonmonotonic. Our proofs of P3 and P4 require the medium to be a polytropic ideal gas; however, a less stringent assumption suffices for P1 and P2.
Instability of a Plasma Column in a Longitudinal Magnetic Field
Authors: Johnson Roy R. , Jerde David A. 
Published: December 2004

The stability of a positive column in a longitudinal magnetic field is investigated by linearization of the macroscopic equations of motion and continuity for ions and electrons. The treatment is more general than similar calculations by Kadomtsev and Nedospasov and Hoh, in that diffusion and magnetic field interaction terms are included in the ion equation of motion, and also in that the equations are solved in a rigorous manner without any a priori assumptions regarding the form of the radial dependence of the perturbations of density and potential.
In the one example calculated, for the helical instability, an important result is the existence of a finite perturbed potential at the wall radius. The boundary between stability and instability as a function of longitudinal electric and magnetic fields is shown graphically, along with the wavelength and frequency of the helical mode at the critical value of the magnetic field.
Shock and Hot Spot Initiation of Homogeneous Explosives
Authors: Mader Charles L. 
Published: December 2004

The shock initiation of detonation in nitromethane, liquid TNT, and single-crystal PETN has been studied using a numerical method for solving the reactive fluid-dynamic equations. Agreement was obtained with previously reported experimental results.
Studies were made which explain in detail the mechanism of initiation of detonation at hot spots created by the interaction of a shock with an inhomogeneity. Energy transfer is accomplished by shocks and rarefactions. It is shown how experimentally observed criticality in bubble size can be related to the divergence rate of the shock, and to other features of the fluid flow. The relation of these results to initiation of detonation in inhomogeneous explosives is discussed.
Pitch Angle Diffusion in a Magnetic Mirror Geometry
Authors: Wentworth R. C. 
Published: December 2004

The diffusion in pitch angle produced by Coulomb scattering of charged particles in a magnetic mirror is derived by geometrical arguments neglecting energy loss. The resultant diffusion equation in particle pitch angle and time agrees with the more fundamental Fokker-Planck equation when energy loss is neglected.
The diffusion coefficient may be defined as the inverse of a ``lifetime'' and for particles in the Van Allen radiation belt it is compared to the energy loss time neglecting pitch angle diffusion. It is shown that both energy loss and pitch angle diffusion must, in general, be considered simultaneously. However, the special problem of the early diffusion of mirror points of a monoenergetic group of electrons injected at very low pitch angle is discussed, and it is shown that significant changes in mirror altitude take place before energy loss is appreciable. Thus the present analysis has a limited but potentially important application to such problems of low injection as the Argus experiment.
Investigation of the Chapman-Jouguet Hypothesis by the ``Inverse Method''
Authors: Wood W. W. , Fickett Wildon 
Published: December 2004

Generalizing a particular case studied by Jones, Stanyukovich, and Manson have given general equations connecting (1) the Chapman-Jouguet detonation pressure; (2) the derivative α = p(∂v/∂E)p of the equation of state E(p, v) of the product gases; (3) the derivatives of the detonation velocity D with respect to the thermodynamic variables defining the initial state of the explosive, such as the initial density ρ0; (4) the variables D and ρ0 themselves.
After presenting a careful derivation of this result, it is pointed out that in conjunction with experimental observations of (a) the unsupported detonation-wave pressure p and velocity D and (b) the derivatives of D with respect to two independent initial variables (e.g., ρ0 and E0), it permits an experimental test of the basic assumptions of detonation theory, namely the assumption of laminar flow and the Chapman-Jouguet hypothesis. Several experimental possibilities are suggested for condensed explosives, where direct experimental observations (such as White's interferometric detection of apparent turbulent flow in gaseous detonations) are difficult. An erroneous criticism, by Pujol and Manson, of Jones' relation as applied to the density dependence of the detonation velocity in low-density solid explosives is also corrected.
Gravitational Resistive Instabilities in Plasma with Finite Larmor Radius
Authors: Jukes J. D. 
Published: December 2004

The linearized equations of a gravity driven, resistive instability of a plasma supported by a planar, sheared magnetic field are shown to be characterized by a variational principle from which an eigenvalue corresponding to a periodic growth is obtained. The effect of a finite ion Larmor radius is included through off-diagonal terms in the pressure tensor in the momentum fluid equation.
When the Larmor radius is zero a numerical solution for the growth rate is found using a one parameter trial function which indicates that the correct function maximizes this rate. When the Larmor radius becomes significant, viz., with decreasing wavelength, the instability becomes an overstability with a reduced growth rate becoming proportional to the square root of the ratio of the resistivity to the wavelength. Whilst numerical results are given beyond this transition, the Larmor radius has become comparable with the thickness of an internal resistive layer and the equations cease to be reliable.
Approximations to the Pair Correlation Function for a Hard-Sphere Fluid
Authors: Klein Max 
Published: December 2004

The equation of state for hard spheres as predicted by the chain, watermelon, convolution-hypernetted chain (CHNC), Percus-Yevick, and two new approximations to the pair correlation function are compared with each other and with a reference isotherm.
The equations of state of the chain and watermelon approximations have been found to be only slight improvements over the linear correction to the ideal gas law. The Percus-Yevick theory has been found to be an improvement over the CHNC approximation for hard spheres in agreement with the results of Hoover and Poirier for hard cubes and of Broyles for several densities of the Lennard-Jones (12,6) gas. The new approximations are designated n = 1 and n = 2. They make use of the solutions to the CHNC integral equation but do not include all the diagrams for the pressure. The approximation n = 2 was found to yield an equation of state in excellent quantitative agreement with the reference isotherm for densities up to 0.707 times the close packed density.
Both the nearest and next nearest neighbors were computed as a function of density in each approximation. Only the CHNC and Percus-Yevick results extrapolate to the proper value at the density of close packing. Both of these approximations, furthermore, indicate the existence of a singularity at densities less than or equal to that of close packing. The approximations considered seem to form part of a uniform approach to the reference isotherm. At the same time, the representations of the known virial coefficients associated with each do not approach the correct virial coefficients in a uniform fashion. Therefore, an understanding of this sequence of approximations cannot be had from the usual examination of virial coefficients.
Ionization Rates and Power Loss from θ-Pinches by Impurity Radiation
Authors: Kolb Alan C. , McWhirter R. W. P. 
Published: December 2004

Calculations are presented for the influence of small impurity concentrations on the energy balance and electron temperature during the magnetic compression of a deuterium plasma. The rate equations which describe the ionization are based on the Corona Plasma Model in much the same way as has been done earlier for a plasma assumed to be homogeneous.
Despite the comparatively high electron densities (≳1016 cm−3) in these plasmas, this model should be applicable because of the high ionic charge at temperatures over ∼10 eV. The radial temperature and density distributions were obtained numerically by coupling the Hain-Roberts two-fluid, hydromagnetic equations to the Corona equations. The ionization of up to four different impurities, i.e., C, N, O, Ne, can be taken into account. Radiation losses were included in the electron energy-balance equation, but the influence of impurity ionization on the electron density and electrical conductivity was neglected. Therefore, only small impurity concentrations can be considered. However, only a few percent impurities have a drastic effect on the electron temperature so that the present calculations may be meaningful in the interpretation of certain experiments.
Nonadiabatic Motion of a Charged Particle in an Axisymmetric Magnetic Barrier
Authors: Roth J. Reece 
Published: December 2004

A study was made of the motion of a single charged particle in the magnetic induction generated by an axisymmetric current sheet, the current of which was sinusoidally modulated along the axis. Several adiabatically invariant quantities were investigated, and it was found that M4 = |v×B|2/|B|3 varied least along a given trajectory. A particle was considered to be adiabatic if M4 varied by less than 5% during a single interaction with the magnetic barrier. An averaging process was found which made it possible to predict the relations between particle mass and energy, and the magnetic induction strength and geometry, which cause M4 to vary by more than 5% during a single interaction with the magnetic barrier.
Experimental apparatus was constructed which made it possible to study a single interaction of a beam of charged particles with a magnetic barrier under steady-state conditions. An experimental procedure was developed which made it possible to detect the transition from adiabatic to nonadiabatic reflection of the ion beam, and the results were compared with the results of the numerical computation.
Microwave Attenuation by Shocked Heated Air
Authors: Dvir M. , Low W. 
Published: December 2004

The microwave attenuation of air in Mach range 8–12 is investigated at initial pressures of 5 mm Hg. It is shown (a) that the experimental peak attenuation is larger than given by conventional theory; (b) that the time dependence of the attenuation curve gives important information regarding the build-up of the ionization as a function of time, the contact surface and the zone behind it.
It is found that the microwave attenuation rises approximately linearly as a function of time to its peak value. The testing time is shorter than that predicted from ideal shock theory but sufficient to establish equilibrium. The electron density changes abruptly upon arrival of the driver gas. However, an appreciable electron density exists over a large region behind the contact surface indicating strong interface mixing. It is also shown that the nature of the surface of the shock tube influences the peak attenuation and the time dependence of this attenuation.
Some Properties of Shock Relaxation in Gas Flows Carrying Small Particles
Authors: Rudinger George 
Published: December 2004

Shock waves passing through uniform suspensions of droplets or solid particles in a gas upset the velocity and temperature equilibrium between the two phases, and a relaxation zone is created in which the equilibrium is gradually re-established. The effects of varying the shock strength or the properties of the mixture are investigated theoretically, and it is noted that some flow variables do not always change monotonically throughout the relaxation zone but may go through a maximum or minimum. The behavior of individual variables is discussed in some detail. A particularly interesting finding is that, for weak shock waves, the maximum particle drag and heat transfer may appear at some distance from, rather than immediately behind, the shock front. The behavior of the variables changes at critical conditions which depend on the thermodynamic properties of the materials involved, on the shock strength, and sometimes also on the assumptions made for the drag coefficient or the Nusselt number. For the gas velocity, these critical conditions can be expressed in simple analytical forms.
In all calculations some assumptions must be made for particle drag and heat transfer. Calculations based on plausible variations of the customarily used formulas show that the results are significantly affected by the assumption made for particle drag, but only to a minor extent by that for heat transfer. It is concluded that experimental determination of the drag coefficient by shock-tube techniques appears feasible.