Oscillatory Carreau flows in straight channels.

The present paper studies the oscillatory flow of Carreau fluid in a channel at different Womersley and Carreau numbers. At high and low Womersley numbers, asymptotic expansions in small parameters, connected with the Womersley number, are developed. For the intermediate Womersley numbers, theoretical bounds for the velocity solution and its gradient, depending on the problem parameters, are proven and explicitly given. It is shown that the Carreau number changes the type of the flow velocity to be closer to the Newtonian velocity corresponding to low or high shear or to have a transitional character between both Newtonian velocities. Some numerical examples for the velocity at different Carreau and Womersley numbers are presented for illustration with respect to the similar Newtonian flow velocity.

On the solidification of a supercooled liquid droplet lying on a surface.

We model the solidification and subsequent cooling of a supercooled liquid droplet that is lying on a cold solid substrate after impact. It is assumed that solidification occurs for a given fixed droplet shape. The shapes used by the model are a sphere, truncated spheres, and an experimentally registered droplet shape. The freezing process is conduction-dominant and is modeled as a one-phase Stefan problem. This moving boundary problem is reformulated with the enthalpy method and then solved numerically with an implicit finite-difference technique. The numerical results for the simple case of a spherical droplet touching a surface are similar to those of a freely freezing spherical droplet and are well confirmed by the 1D asymptotic analytical model of Feuillebois et al. (J. Colloid Interface Sci. 169 (1995) 90). A freezing water droplet is considered as an example. The numerical results for full freezing time, subsequent cooling time, and last freezing point coordinate for the various droplets shapes are fitted by analytical functions depending on supercooling, thermal resistance of the target surface (expressed by Biot number), and spreading parameter. These functions are proposed for direct application, thus avoiding the need to solve the full freezing and cooling problem.

Synthesis and biological activity of canavanine hydrazide derivatives.

The canavanine derivatives L-canavanine hydrazide (CH), L-canavanine-bis-(2-chloroethyl)hydrazide (CBCH) and L-canavanine phenylhydrazide (CPH) were synthesized and evaluated for biological activity in microorganisms, plants and tumor cells using canavanine as a positive control. (1) In microbial systems, the compounds exerted activity, as assessed in 14 bacterial strains. The effect of canavanine was easily removed by equimolar concentrations of arginine or ornithine, while the effect of CBCH or CPH was abolished by 10-fold excess of arginine or 10- to 100-fold excess of ornithine. (2) In plants, the activity of CH and CBCH were relatively low, whereas the inhibitory potential of CPH was comparable or even superior to that of canavanine, resulting at 1 mM concentration in a nearly complete block of tomato cell growth, and reducing by up to 80% the length of radicles of cress, amaranth, cabbage and pumpkin. (3) In pumpkin seeds, CPH or canavanine induced the synthesis of four small heat shock proteins of hsp-17 family in the pH range of 6 to 7.5. The proteins exhibited in both cases a similar profile, but differed in the timing of their expression and/or accumulation. With canavanine, the highest hsp-17 expression was found after 48 h of drug treatment, while with CPH this maximum was shifted to 24 h. (4) CPH proved to be highly cytotoxic against Friend leukemia cells in culture, exceeding by one order of magnitude the cytotoxicity of canavanine. The effect of canavanine was completely removed in the presence of equimolar amounts of arginine, while a 20-fold excess of arginine failed to abolish the cytotoxicity of CPH. Thus, a proper hydrazide modification of canavanine may lead to a significant increase in its growth-inhibitory activity and to a change in the mode of action of the parent compound.

Synthesis and antimicrobial activity in vitro of new amino acids and peptides containing thiazole and oxazole moieties.

2-(Pyrrolidinyl)thiazole-4-carboxylic acid 5d, 2-(1-aminoalkyl)thiazole-4-carboxamides and hydrazides 8, 10 have been synthesized using alanine, valine, and proline as educts. In addition oxazole amino acids derived from leucine 20a and alanine 20b and some peptides 13, 14, 16 containing the 5-ring heterocyclic backbone modifications have been prepared. The thiazole and oxazole containing amino acids and peptides showed moderate antibacterial activity in vitro against various Gram-positive (Staphylococcus aureus, Bacillus cereus, etc.) and Gram-negative (Escherichia coli, Protens vulgaris, etc.) bacteria, fungi (Candida albicans), and yeast (Saccharomyces cerevisae, etc.).

Anticandidial effect of phenylbutene derivatives and their interaction with ergosterol.

This paper reports the effect of phenylbut-3-en-2-one, of its analogues, bearing 3-nitro, 4-nitro, 4-chloro- and 4-dimethylamino substituents at the phenyl moiety, and of the hydrazide, phenylhydrazide and oxime of 4-nitrophenylbut-3-en-2-one on the growth and germ-tube formation of Candida spp., as well as their ability to interact with ergosterol in water/dimethylformamide (DMF) solution and their acute toxicity for mice. 3-Nitro-, 4-nitro- and 4-chlorophenylbut-3-en-2-ones inhibit candidial growth in vitro in concentrations ranging from 0.01 to > 0.4 mM and their activity is comparable to that of ketoconazole (in mg/l) and lower than that of amphotericin B. The rest of the compounds are inactive at > 0.4 mM. Germ-tube formation of C.albicans is inhibited at 0.04 mM 4-nitrophenylbut-3-en-2-one and at 0.005 mM of the 3-nitro isomer. A decrease in the absorption maxima in ergosterol mixtures with 4-dimethylamino, 3-nitrophenylbut-3-en-2-one and the oxime of the 4-nitrophenylbut-3-en-2-one was observed, indicative of interaction in water/DMF solutions, while no changes in the UV spectra of the remaining compounds were detectable. That suggests that the growth inhibiting effect is not in correlation with their ability to interact with ergosterol, despite the resemblance to polyenes. LD50 for mice is 367 mg/kg for 4-nitrophenylbut-3-en-2-one and 398 mg/kg for the 3-nitro isomer.

Antimicrobial effect of tetramethyldithiooxamide and its application as a biocide.

Tetramethyldithiooxamide (TMDTOA) is a stable and effective inhibitor of metal corrosion. The antimicrobial effects of TMDTOA and its metal compounds were investigated with regard to their use as biocides for water treatment. Growth of a variety of strains of bacteria and yeasts was completely inhibited at 400 mumol l-1 TMDTOA or its metal complexes. At 100 mg l-1 there was a 99.99% reduction in the number of viable micro-organisms; this activity persisted for 1-3 months. TMDTOA can be produced cheaply at 98% purity by a novel method, representing an alternative cost-effective water treatment agent combining corrosion-inhibiting and biocide characteristics.

Effect of platinum (II) complexes of 4-methoxy- and 4-chlorobenzoic acid hydrazides on Saccharomyces cerevisiae.

This study reports the anti-yeast effect of the 4-methoxybenzoic acid hydrazide (pmbah), 4-chlorobenzoic acid hydrazide (pcbah) and their Pt(II) complexes: cis- [PtL2X2] and cis- [PtL(NH3)Cl2] where L is either pcbah or pmbah and X is Cl, Br or I. MICs of the 4- substituted analogues (20,000-625 microM) are much lower than those of the previously reported benzoic acid hydrazide and 3-methoxybenzoic acid hydrazide. Complex formation results in significant increase of potency which may be due to a change in the mechanism of action, but the MIC (> 400-50 microM) and the IC50 (> 400-1 microM) values show that higher activity of the ligands in the free state does not result in enhanced complex activity. Differences in the potency of iodo-, chloro- and bromo complexes suggest MIC and IC50 values may be in correlation with the stability of the complex, rather than with the activity of the free ligands. Osmotically unstable mutants were more susceptible to the compounds than their parent strains, but differences among the parent strains, but differences among the parent strains were greater.

Effect of platinum(II) complexes of benzoic and 3-methoxybenzoic acid hydrazides on Saccharomyces cerevisiae.

The inhibitory effect of benzoic acid hydrazide (bah) and 3-methoxybenzoic acid hydrazide (mbah) on Saccharomyces cerevisiae strains has been compared to that of their platinum(II) complexes: cis-[Pt(mbah)2X2], cis-[Pt(NH3)(mbah)Cl2].0.5 H2O, cis-[Pt(mbah)2X2] and cis[Pt(NH3)(mbah)Cl2] (mean = Cl, Br = I), and cis-[Pt(NH3)2Cl2]. The minimal inhibitory concentrations for bah and mbah were 5000-20,000 microM whereas for their Pt(II) complexes they were much less (25-800 microM) and did not exceed these of cisplatin (100-800 microM). The activity of the Pt(II) complexes of bah and mbah varied in wide ranges for the different yeast strains tested. Osmotically unstable mutants were found to be more susceptible. The most active complexes were [Pt(NH3)(bah)Cl2].0.5 H2O and [Pt(NH3)(mbah)Cl2].

Synthesis and antibacterial activity of 7 beta-[3-(un)substituted-2-aminopropionamido]-3-vinylcephalosporin s and related compounds.

A series of new 7 beta-[3-(un)substituted-alanyl]-3-vinylcephalosporins and some related compounds, 4a-l is described. They incorporate residues of proteinogenic L-alpha-aminocarboxylic acids, their antimetabolites and enantiomers as well as a dipeptide in the 7 beta-acylamido side chain. The acylation of diphenyl-methyl 7-amino-3-vinyl-3-cephem-4-carboxylate (2: R2 = DPM) with various protected alpha-aminocarboxylic acids 1a-k and the dipeptide 1l is carried out using TBTU as coupling reagent. The compounds, except 4f, are active in vitro against S. aureus and S. lutea, but only 4a, 4k, and 4l inhibit some of the Gram-negative strains.

[The direct health effects of air pollution in Vratsa in 1991]. / Neposredstveni zdravni efekti ot zamursiavaneto na vuzdukha vuv Vratsa prez 1991 g.

The effect of air pollution in the town of Vratsa on the daily morbidity of the population has been studied during the first half of 1991. Studies are performed on the correlation between the daily dynamics in the pollution according to specific for the town indices ammonia, hydrogen sulfide, sulphur dioxide, nitric oxides, dust, meteorological parameters temperature of the air, relative humidity, air velocity, barometric pressure and some respiratory and allergic diseases among the population. It is already established that the level of the air pollution in the town of Vratsa, among which dominate ammonia and hydrogen sulfide, have a direct effect on the acute respiratory morbidity, more expressed among the children. This influence is traced both in episodes of increased pollution, and in the course of several days afterwards and is conductive by the combination of unfavourable meteorological conditions, hindering the dispersion of the atmospheric pollutants.

[Atmospheric pollution in the city of Ruse and its effect on the health of the population]. / Zamursiavane na atmosferniia vuzdukh v gr. Ruse i negoviiat efekt vurkhu zdraveto na naselenieto.

The atmospheric air pollution in the town of Ruse and the related with that changes in the health status of the population has been studied. As a result of the transference from Giurgiu (Romania) hydrogen chloride pollution is observed. Immediate changes in the morbidity of respiratory diseases is determined on the days of pollution. There is also a durable tendency for deterioration of the health status of children and adults, as well as lag behind in the physical development of schoolchildren and aggravated functional lung indices.

[The effect of atmospheric pollution in the city of Srednogorie on the health of the population]. / Vliianie na atmosfernoto zamursiavane v gr. Srednogorie vurkhu zdraveto na naselenieto.

The town of Srednogorie is one of the ecologically endangered districts of Bulgaria because of environmental pollution by the copper works. The morbidity of the population is studied in relation to the atmospheric air pollution. Basic pollutants are: sulphuric compounds (sulphur dioxide and sulphuric acid) and to a lower rate--lead and arsenic. The tendencies of air pollution are favourable, save lead pollution, the concentration of which increases during the last years. The structure of the morbidity of the population point out that there is an increase of the relative part of diseases, which could be related to the systematic effect of heavy metals and arsenic (malignant neoplasms, diseases of the nervous and cardiovascular system, diseases of the kidney). More frequently are observed acute and chronic cases of diseases of the respiratory tract.

[The health problems related to atmospheric pollution in large industrial regions of Bulgaria]. / Zdravni problemi, svurzani s atmosfernoto zamursiavane v krupni promishleni raioni na Bulgariia.

Epidemiological studies are performed in some towns and large industrial regions of the country, in order to establish the changes in the health state of the population, due to atmospheric pollutants. The attention is directed to regions with national industrial branches, most intensively polluting the atmospheric air (metallurgy, chemistry, petroleum-chemistry, cellulose-paper industry) and such, where the air pollution is related first of all to transport across the border-line. The unfavourable effect of the atmospheric pollution on the exposed population is proved. It is however, the reason for increased morbidity according to a number of nozologics and on first place--of respiratory and allergic diseases. Parallel to that are interpreted the results of the performed inquiries and paraclinical studies, revealing the presence of prior to the disease changes in the population of the examined regions.

[Health effects of atmospheric pollution in areas of paper-cellulose production and fodder yeast manufacture]. / Zdravni efekti na zamursiavaneto na atmosferniia vuzdukh v raioni s khartieno-tselulozna promishlenost i furazhni drozhdi.

In one of the studied towns with a large plant for cellulose and paper and another for fodder yeasts the ambient air was polluted by specific contaminants--hydrogen sulfide and mercaptans considerably higher in town R than in town B after data of the Principle Hydrological and Meteorological Administration. A higher incidence was established both in the general morbidity and the nosological units, probably etiologically determined by the defined pollutants in town R. Both the allergic reactivity and the clinico-laboratory indices, which characterise the functional state of the exposed pollution, were raised. The results give grounds to believe, that the ambient air pollution in town R is a risk factor for the health of the population.

[Comparative data on the glutathione and methemoglobin levels in the blood of pregnant and nonpregnant white rats inhaling NO2]. / Sravnitelni danni za nivoto na glutation i metkhemoglobin v kruvta na bremenni i nebremenni beli plukhove, inkhalirani s NO2.

Nitrogen dioxide /NO2/, is one of the basic photochemical atmospheric pollutants possessing both direct and indirect toxic effects. When inhaled NO2 affects directly the blood hemoglobin forming methemoglobin. The rate of effect depends on the level of the intra-erythrocyte redox systems and in the first place on the reduced glutathione. The systemic toxic effects of NO2 and is easy penetration through the hemato-alveolar barrier are well known. However the effects of NO2 on the organism during pregnancy have nor been studied. The present study has been designed to evaluate the effect of NO2 on the reduced oxidized glutathione and the level of methemoglobin in the blood of pregnant and nonpregnant female rats. Inhalation exposure of pregnant albino rats to NO2 in concentration of 10 and 1 mg/m3, 5 hours daily, throughout gestation /21 days/, induces an increased synthesis of glutathione and shifting towards the reduced form, which could be taken as a sign of adaptive mechanisms. The nonpregnant animals show no such effect, as they more easily compensate the oxidizing effect of NO2. At the age of 1 month the progeny of the NO2-exposed mothers show the same tendency to an elevated synthesis of glutathione and increase of its reduced form. When treated again with NO2 at the same dose levels during gestation, the F1 females show no changes in blood glutathione, but the level of methemoglobin is raised--an effect not observed in the parental generation.