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At least 55 records · Page 3Linked to original sources
PubMed1991

Lymphocyte transformation test with nickel in hard metal asthma: another sensitizing component of hard metal.

To determine cell-mediated immunity to nickel, another matrix in hard metal besides cobalt, lymphocyte transformation tests (LTT) with nickel were carried out in seven hard metal asthma patients all of who had reacted to cobalt chloride in the bronchial provocation tests (BPT). Immunoallergic studies prior to the present study revealed that three of the seven generated a simultaneous positive reaction in the BPT with nickel and the allergosorbent test with nickel-conjugated human serum albumin (Ni-HSA). A stimulation index in LTT indicating a positive response was defined on the basis of results from the studies in the controls. Data revealed that two of the three who showed a combination of positive bronchial and immunological reactions with nickel had a positive LTT with nickel. In the other five, peripheral lymphocytes did not proliferate in response to nickel. Thus it is suggested that cell-mediated immunity to nickel as well as cobalt is implicated in some cases associated with hard metal asthma.

Asthma↗
PubMed1997

Biological control studies of soft and hard ticks in Egypt. I. The effect of Bacillus thuringiensis varieties on soft and hard ticks (ixodidae).

The potential activity of three varieties of Bacillus thuringiensis (kurstaki, israeliensis, and thuringiensis) against the soft tick Argas persicus and the hard tick Hyalomma dromedarii was investigated. Soft ticks succumbed within a period ranging from 36 h to 5 days and hard ticks died at between 48 h and 10 days posttreatment, depending on the dose. Concentrations lethal to 50% of tick populations (LC50 values) indicated that Dipel 2x (B. thuringiensis var. kurstaki) was the most potent, followed by Vectobac (B. thuringiensis var. israeliensis), then HD 703 (B. thuringiensis var. thuringiensis). A. persicus was more affected than H. dromedarii by B: thuringiensis varieties. Eggs were mostly affected at 16 and 25 days after deposition for A. persicus and H. dromedarii, respectively.

Animals↗
PubMed2004

Polydisperse hard spheres at a hard wall.

The structural properties of polydisperse hard spheres in the presence of a hard wall are investigated via Monte Carlo simulation and density functional theory (DFT). Attention is focused on the local density distribution rho(sigma,z), measuring the number density of particles of diameter sigma at a distance z from the wall. Estimates of rho(sigma,z) are obtained for bulk volume fractions eta(b)=0.2 and eta(b)=0.4, and for two choices of the bulk parent distribution: a top-hat form, which we study for degrees of polydispersity delta=11.5% and delta=40.4%, and a truncated Schulz form having delta=40.7%. Excellent overall agreement is found between the DFT and simulation results, particularly at eta(b)=0.2. A detailed analysis of rho(sigma,z) confirms the presence of oscillatory size segregation effects, as observed in a previous DFT study [I. Pagonabarraga, M. E. Cates, and G. J. Ackland, Phys. Rev. Lett. 84, 911 (2000)]. For large delta, the character of these oscillation is observed to depend strongly on the shape of the parent distribution. In the vicinity of the wall, attractive sigma-dependent depletion interactions are found to greatly enhance the density of the largest particles. The local degree of polydispersity delta(z) is suppressed in this region, while further from the wall it exhibits oscillations.

Journal Article↗
PubMed1999

Interfacial free energy of hard-sphere fluids and solids near a hard wall.

A hard-sphere system near a planar structureless hard wall is considered in thermodynamic equilibrium. The associated interfacial free energies are calculated both for a bulk fluid and a bulk face-centered-cubic crystal along (111), (110), and (100) orientation. Combining Monte Carlo simulations and thermodynamic integration, we obtain the wall-fluid and the wall-solid interfacial free energy over the whole range of possible bulk densities. The "exact" computer simulation data are compared to theoretical approximations. For moderate bulk densities, the wall-fluid interfacial free energies compare reasonably well with scaled-particle theory and density functional results. For the wall-crystal interface, we propose a simple analytical cell theory which yields good agreement with our simulation data over the whole range of bulk crystal densities.

Journal Article↗
PubMed2000

Binary hard-sphere fluids near a hard wall

By using the Rosenfeld density functional, we determine the number density profiles of both components of binary hard-sphere fluids close to a planar hard wall as well as the corresponding excess coverage and surface tension. The comparison with published simulation data demonstrates that the Rosenfeld functional, both its original version and sophistications thereof, is superior to previous approaches, and exhibits the same excellent accuracy as known from studies of the corresponding one-component system.

Journal Article↗
PubMed2005

Virial coefficients of hard spheres and hard disks up to the ninth.

A technique for topological analysis of the Ree-Hoover diagrams is developed with the aim to calculate the Ree-Hoover weights up to the ninth order with moderate demands on computer storage and CPU time. The ninth virial coefficients of hard spheres and disks are calculated, and the lower virial coefficients are accurately recalculated. The calculations require several spanning diagrams; the most important spanning chains are generated by reptation, other spanning diagrams by the standard Metropolis Monte Carlo algorithm. The tenth and eleventh virial coefficients for hard spheres are estimated.

Journal Article↗
PubMed2006

Efficiency of rejection-free dynamic Monte Carlo methods for homogeneous spin models, hard disk systems, and hard sphere systems.

We construct asymptotic arguments for the relative efficiency of rejection-free Monte Carlo (MC) methods compared to the standard MC method. We find that the efficiency is proportional to exp(constbeta) in the Ising, sqrt[beta] in the classical XY, and beta in the classical Heisenberg spin systems with inverse temperature beta, regardless of the dimension. The efficiency in hard particle systems is also obtained, and found to be proportional to (rho(cp)-rho)(-d) with the closest packing density rho(cp), density rho, and dimension d of the systems. We construct and implement a rejection-free Monte Carlo method for the hard-disk system. The RFMC has a greater computational efficiency at high densities, and the density dependence of the efficiency is as predicted by our arguments.

Journal Article↗
PubMed2005

Hard-sphere-like dynamics in a non-hard-sphere liquid.

The collective dynamics of liquid gallium close to the melting point has been studied using inelastic x-ray scattering to probe length scales smaller than the size of the first coordination shell. Although the structural properties of this partially covalent liquid strongly deviate from a simple hard-sphere model, the dynamics, as reflected in the quasielastic scattering, are beautifully described within the framework of the extended heat mode approximation of Enskog's kinetic theory, analytically derived for a hard-sphere system. The present work demonstrates, therefore, the applicability of Enskog's theory beyond simple liquids.

Journal Article↗
PubMed1977

[Hard-x-ray therapy. The position between orthovolt- and ultra hard ray therapy (author's transl)].

The special position of "hard-ray therapy" (RT 305, 300 kV) between the orthovolt-therapy and the ultra-hard-ray therapy is described in physical respect and clinical practicability. In comparison with the orthovolt-therapy there is an advantage in better skin tolerance, the absence of bone shadows and the possibility to increase the depth-dose up to 50%. The main indications are given in the intermediate therapy and the short distance therapy of greater tumors. The palliative deep therapy is administered under better conditions as with the conventional x-ray irradiation.

Bone Neoplasms↗
PubMed2002

A new deformation model of hard alpha-keratin fibers at the nanometer scale: implications for hard alpha-keratin intermediate filament mechanical properties.

The mechanical behavior of human hair fibers is determined by the interactions between keratin proteins structured into microfibrils (hard alpha-keratin intermediate filaments), a protein sulfur-rich matrix (intermediate filaments associated proteins), and water molecules. The structure of the microfibril-matrix assembly has already been fully characterized using electron microscopy and small-angle x-ray scattering on unstressed fibers. However, these results give only a static image of this assembly. To observe and characterize the deformation of the microfibrils and of the matrix, we have carried out time-resolved small-angle x-ray microdiffraction experiments on human hair fibers stretched at 45% relative humidity and in water. Three structural parameters were monitored and quantified: the 6.7-nm meridian arc, which is related to an axial separation between groups of molecules along the microfibrils, the microfibril's radius, and the packing distance between microfibrils. Using a surface lattice model of the microfibril, we have described its deformation as a combination of a sliding process and a molecular stretching process. The radial contraction of the matrix is also emphasized, reinforcing the hydrophilic gel nature hypothesis.

Hair↗
PubMed2000

Enhanced stability of layered phases in parallel hard spherocylinders due to addition of hard spheres

There is increasing evidence that entropy can induce microphase separation in binary fluid mixtures interacting through hard particle potentials. One such phase consists of alternating two-dimensional liquidlike layers of rods and spheres. We study the transition from a uniform miscible state to this ordered state using computer simulations, and compare results to experiments and theory. We conclude the following: (1) There is stable entropy driven microphase separation in mixtures of parallel rods and spheres. (2) Adding spheres smaller than the rod length decreases the total volume fraction needed for the formation of a layered phase, and therefore small spheres effectively stabilize the layered phase; the opposite is true for large spheres. (3) The degree of this stabilization increases with increasing rod length.

Journal Article↗
PubMed2004

When mixtures of hard-sphere-like colloids do not behave as mixtures of hard spheres.

The validity of the concept of "hard-sphere-like" particles for mixtures of colloids is questioned from a theoretical point of view. This concerns the class of pseudobinary mixtures in which the nonsteric interactions between the colloids are "residual" (with very small range and moderate strength). It is shown that contrary to common expectation, such interactions may have unexpected consequences on the theoretical phase diagram. The distinction between this situation and true solute-solvent mixtures is emphasized.

Journal Article↗
PubMed1993

Hard-of-hearing pupils in ordinary schools. An analysis based on interviews with integrated hard-of-hearing pupils and their parents and teachers.

The primary purpose of this investigation was to establish the extent to which health service and educational programs complied with Norwegian legislation for hard-of-hearing children integrated in ordinary schools, and to describe their communication skills, school performance and social network development. Nineteen hearing aid users between the ages of 8 and 16, their parents and their classroom teacher were interviewed. All the pupils came from the same area in south-eastern Norway. The results showed that many of the children had not benefited from the rights to which they were entitled by law. Despite this, the hearing aid users as a group seemed to have a satisfactory development, especially with regard to speech. They seemed content with their school and class situation, especially the younger pupils. Greater loss of hearing often led to earlier diagnosis and, therefore, earlier and more adequate help. Consequently, they felt happier at school. Pupils with a mild loss were mainly left alone without any special service.

Child↗
PubMed1990

[Effects of EDTPO on hard tissues in rats. 2. Changes of serum components and morphology of hard tissues due to various doses of EDTPO].

Dose dependent effects of EDTPO on morphology and mineralization of hard tissues as well as calcium (Ca), inorganic phosphorus (IP) and alkaline phosphatase (ALP) levels in serum were examined in growing rats. Five groups of male S.D. rats weighing 110-120g were received s.c. injections of 0 (control), 1, 2, 4, and 8mg P/kg body wt. of EDTPO once daily (at noon) for 10 days respectively. Tetracycline (Tc.) were i.p. injected three times, one day before drug treatment (1st), 5th (2nd) and 10th (3rd) day of experimental period. All rats were received i.p. injection of 185kBq (5 microCi) of 45Ca six hours after the 10th injection of EDTPO. On the next day, blood samples were taken from the carotid artery. Then the animals were killed and both tibias, submandibular teeth and right femur were removed. Serum Ca, IP and ALP were determined by spectrophotometry. Wet, dry and ash bone weight were measured and bone calcium was determined by atomic absorption method. 45Ca activity was counted by the liquid scintillation counter. Serum Ca levels revealed decreasing tendency at the dose of 1mg P/kg and 2mg P/kg of EDTPO but increasing tendency at 4mg P/kg and significant increase at the dose of 8mg P/kg. Specific activity of 45Ca in serum increased slightly at 2mg P/kg, but at the dose of 8mg P/kg increased five times compared to that of control. Decrease of IP and increase of ALP level were observed only at the dose level of 8mg P/kg. Wet, dry, and ash weight, and Ca content of femur and 45Ca activity were decreased dose-dependently. In histological examination, changes of tibia and teeth were observed at the dose of 2mg P/kg and following dose increase these changes were more significantly. Ultraviolet line of Tc. appeared three in proximal metaphysis of tibia and dentin at the dose of 1mg P/kg and 2mg P/kg, but at the dose of 4mg P/kg and 8mg P/kg 2nd and 3rd line could not be detected. These result indicated that the effects of EDTPO on serum ingredients, long bone and teeth are initiated at the dose of 2mg P/kg, appeared at the dose of 4mg P/kg significantly, and at the dose of 8 mg P/kg severely. In addition, increase of the ratio of 45Ca specific activity between serum and bone observed at the dose of 4mg P/kg and 8mg P/kg suggested that these effects of EDTPO would be due to inhibitory action on mineralization.

Alkaline Phosphatase↗