Samples of chernozem and brown soils were irradiated with gamma rays using doses of 1.5 to 4.5 Mrad, or fractionally autoclaved at 1 and 2 kp/cm2. Consumption of oxygen by cellular suspensions of bacteria added to suspensions of sterilized soils was higher than in untreated samples. The increased oxygen consumption indicated an increase in the quantity of a biologically oxidizable substrate which could be released during the irradiation or autoclaving of soils. The amount of oxygen consumed was proportional to the radiation dose or autoclaving time and the pressure used, and was dependent also on the type of soil. The accessible substrate could be immediately, without a lag phase, oxidized by the added microorganism. The extent and rate of oxygen consumption in the sterilized soil samples varied in different microorganisms. It was observed that decomposition of vanillie acid by a cell suspension ofCellulomonas sp. was stimulated in the soil sterilized by radiation. The significance of these findings for the soil metabolic studies is discussed.

The retention behavior of the unmodified phosphodiester oligonucleotide sequence isomers was investigated on two different anion exchange columns: Biospher GMB 1000Q (based on DEAE-modified glycidyl methacrylate) and PolyWAX LP (based on silica with a crosslinked coating of linear polyethyleneimine). There was a notable difference in retention of oligonucleotides of the same composition but differing in the position of a single base. The most pronounced difference was observed between the oligonucleotides with the variable base in the end and in the center of the sequence. The use of either acetonitrile or 2-propanol as a mobile phase organic modifier did not markedly affect the retention time patterns. Prediction of the retention times of oligonucleotides must take into account the base position as well as identity. This is the first report of such a "same composition different sequence" effect, described for the short peptides, for synthetic oligonucleotides.

The retention behavior of unmodified phosphodiester mixed-sequence oligonucleotides has been investigated under different conditions on a glycidyl methacrylate-based, DEAE-modified anion-exchange Biospher GMB 1000Q column. It was verified that separation is based not only on an anion-exchange mechanism but also on secondary interactions of the bases with the stationary phase. Notably different retention was observed for oligonucleotides differing only in the position of one base in the sequence. The nature of these secondary interactions and the effect of sequence on retention is discussed. The effect on retention of the type and concentration of organic mobile phase modifier, mobile phase pH, sample molecular weight, and the bases in the sample was investigated. A linear relationship was found between retention and the molecular weight of mixed-sequence oligonucleotides with lengths from 15 to 40. Resolution of N − 1 synthetic by-products from the full-length product was also evaluated.

Textured thin film of PbTiO 3 on glass and both textured and stressed films of TiB 2 on iron substrate were investigated by two-dimensional reciprocal space mapping. The texture and residual stress parameters were found by fitting of the measured intensity in the reciprocal space map by the simulated data. Two different types of texture were found in TiB 2 for different values of residual stress. The relevance of resulting parameters was checked using different models. Simulation of the data involved a proper empirical texture correction, the Pearson VII profile function, the irradiated volume correction giving a possibility of the film thickness determination, the background, and other correction factors (Lorentz, polarisation).

A critical analysis is presented of the measurement by microindentation of the hardness of superhard films with hardness, H, exceeding 50 GPa. This analysis shows that a very high hardness of the Ti–Si–N nanocomposite film reaching a value of 105 GPa, which was recently reported, is hardly a correct value and so till now, very probably, no material harder than diamond has been prepared.

The article reports on structure and mechanical properties of TiB alloy films sputter deposited from a sintered TiB2 target using an unbalanced dc magnetron. We present results of a systematic investigation of the effect of negative substrate bias, Us, substrate ion current density is, and substrate temperature, Ts, on properties of TiB films. The X-ray diffraction (XRD) analysis shows that the TiB films consist of the hexagonal TiB2 phase with the typical (0001) texture only. The TiBx films are over-stoichiometric with the ratio x=B/Ti≈2.4. All TiB films sputter ion plated in argon magnetron discharge are superhard films with hardness H>40 GPa and exhibit high values of (i) effective Young's modulus E*=E/(1−ν2) up to approximately 600 GPa and (ii) elastic recovery, We, up to approximately 82%; here E and ν are the Young's modulus and the Poisson's ratio, respectively. Besides, it was found that the value of the Bragg's angle 2θ of the (0001) reflection line can be easily controlled by the energy delivered to the film during its growth by (1) the substrate heating Ts and (2) ion bombardment (Us, is). The angle 2θ of the (0001) reflection increases with increasing Ts from 300 to 550 °C and decreasing Us from −150 to −50 V. In this range of process parameters, the energy Ep delivered to the growing film per condensing atom by ion bombardment can be adjusted to a value, at which the (0001) reflection from sputtered films is close to that of the TiB2(0001) powder standard. These films exhibit a low macrostress, which approaches to zero. It enables to sputter thick (up to 8 μm) superhard (H>40 GPa) TiB films. The optimum value of Ep is achieved when the TiB film is sputtered at Us=−50 V, is=1 mA/cm2, Ts=550 °C with a deposition rate aD=52 nm/min. The TiB film prepared under these conditions exhibits a maximum hardness of H≈77 GPa, measured using a computer controlled microhardness tester Fischerscope H100 at the Vickers diamond indenter load L=50 mN.

The paper is devoted to an assessment of the mechanical behavior of hard and superhard nanocomposite coatings from loading/unloading curves measured by a computer-controlled Fischerscope H 100 microhardness tester and a maximum depth dmax of the diamond indenter impression into the coating at a given load L. It is shown that: (1) the area between the loading/unloading curve and the value of dmax decreases with increasing (i) hardness H, (ii) effective Young's modulus E*=E/(1−ν2) and (iii) universal hardness HU, where E and ν are the Young's modulus and the Poisson ratio, respectively; and (2) there is no simple relation between the mechanical response of the coating and H or E* alone; however, this response is strongly dependent on the ratio H/E*. The last fact gives a possibility of tailoring the mechanical properties of a coating for a given application, e.g. to prepare coatings with high hardness H, high resistance to plastic deformation (∼H3/E*2), high elastic recovery We, but with low E* and high dmax. Special attention is also given to the analysis of problems in accurately measuring the hardness of superhard (≥60 GPa) coatings. It is shown that a high elastic recovery We≥80% of superhard films with H≥60 GPa (1) strongly decreases the gradient dH/dL and (2) shifts the region L, where H(L)≈constant and the hardness H is correctly measured, to higher values of L. This means that the lowest load L used in the hardness measurement must be higher than L used in measurements of coatings with H<60 GPa to prevent the value of H measured from being significantly higher than the real hardness of the coating.

Magnetron sputtering is a very efficient method for a production of nanocomposite films. The nanocomposite films are formed in consequence of a combined action of four processes: (1) low-energy ion bombardment, (2) element mixing, (3) substrate heating and (4) energy released or consumed during the film formation. This article reviews the present state of the art in the field of sputtered hard and superhard nanocomposite films. Special attention is devoted to mechanical properties of hard nanocomposite coatings and open problems in their formation and characterization. Two problems are discussed in detail: (i) the correlation between hardness, grain size and microstrain and (ii) the correctness of the evaluation of mechanical quantities from microindentation measurements. Trends of next development of hard and superhard nanocomposite coatings are outlined.

Titanium nitride (TiN) coatings were deposited by unbalanced D.C. magnetron sputtering via the non-reactive and reactive technique using a TiN or Ti target, respectively. The differences of these sputter techniques have been studied in detail. Main emphasis was laid on the characterization of the ion bombardment parameters for both techniques. The ion energy and the ion/atom flux ratio was varied in the range between 30 and 120 eV and 0.1 and 10, respectively. Coating characterization was done with respect to morphology, chemical composition, crystallographic structure, hardness, and macrostresses during thermal cycling. The use of an ion energy of 30 eV combined with an ion/atom flux ratio of 8.6 and 10 results in a microhardness of approximately 47 GPa for non-reactive and reactive TiN coatings, respectively. Their biaxial stresses and grain sizes also show comparable values for both techniques of approximately −2 GPa and 23 nm, respectively. The similar properties of TiN coatings deposited using non-reactive or reactive sputtering are, however, only valid for an intense ion bombardment. The transition from porous columnar to dense fibrous structures requires a more pronounced activation of film growth by ion bombardment in the case of reactive deposition as compared to non-reactive sputtering. Mainly, this is a result of the higher energy of the N atoms and the three times higher deposition rate in the non-reactive process compared to the reactive one. Moreover, during reactive sputtering, energy is also needed to dissociate the molecular nitrogen gas. The results obtained should serve as a fundamental basis for the understanding of the differences in growth conditions for non-reactive and reactive sputter techniques. Furthermore, an explanation of the high hardness values of the coatings is given and the influence of thermal annealing on the defect density, grain size and microhardness of the coatings is presented and discussed in detail.

3-Chloropyrocatechol is formed as a result of oxidation of 2-chlorobenzoate by Pseudomonas stutzeri. 2-Chloro-cis,cis-muconic acid is the product of oxidation of 3-chloropyrocatechol. A catabolic pathway for the degradation of 2-chlorobenzoate by a newly isolated strain of P. stutzeri is proposed.

The heterocontinuous flow cultivation technique was used for the study of 2-chlorobenzoic and 2,5-dichlorobenzoic acid degradation in soil columns inoculated with Pseudomonas stutzeri. 2-Chlorobenzoic and 2,5-dichlorobenzoic acids disappeared from the soil columns within 8 and 12 d, respectively. The presence of the haloaromatics increased the survival of strain KS25 in soil. Viable cell numbers in the soil columns flushed with 2-chlorobenzoic and 2,5-dichlorobenzoic acids were 1.3 and 2 times higher, respectively, than those without the chlorobenzoic acids after 30 d of incubation.

A strain of Pseudomonas stutzeri KS25 utilizing 2-chlorobenzoic and 2,5-dichlorobenzoic acids as the sole carbon and energy source was isolated from polychlorophenol-contaminated soil and sewage, using the method of enrichment cultures. This strain was also able to grow on 2-fluoro-, 2-iodo-, 2-bromo- and 2,5-dihydroxybenzoate, but did not utilize 3-, 4-chloro-, 2,4- and 2,6-dichlorobenzoates as the sole carbon and energy source, however, it cometabolized 3-chloro-, 2,4- and 2,6-dichlorobenzoates, but not 4-chlorobenzoate. The yield of released chlorine during utilization of 2-chloro- and 2,5-dichlorobenzoates amounted to 100% of the theoretical. The concentration of 2-chloro- and 2,5-dichlorobenzoates, not substantially inhibiting the isolated microorganism, was within the range 0.25-0.5 and 2.5-3.0 g/L, respectively.

ABSTRACT Kunc, F., 1991. Organic substrates and microbial conversion of herbicides in soil. Presence of organic compounds in soil is one of the main factors that determine the activity of microorganisms including their capability of conversion of xenobiotics. The effect manifests itself at various levels of the system's complexity: from the subcellular level (genetic, enzymatic) to that of microbial communities in natural environments. This review deals with final consequences of the effect of native and added organic substrates on the decomposition of herbicides and with some mechanisms involved in these processes. The role of organic compounds in the control of the synthesis and activity of degradation enzymes, in cometabolic processes and in the history of nutrition of microbial associations with respect to their adaptation is documented. Limitation of the decomposition due to adsorption and formation of complexes of the herbicides with the organic substrate as well as due to the effect of the conditions of soil environment are also described. Possibilities of using the knowledge to control the microbial degradative activity are suggested with the aim to stimulate the removal of undesirable xenobiotic residues from soil environment.

Biological conversion of the herbicide bromoxynil (3,5-dibromo-4-hydroxybenzonitrile) was studied in a batch culture ofPseudomonas putida by using HPLC. The process had a cometabolic character and proceeded only in the presence of another, simultaneously metabolizable, carbon and energy source. The intensity of degradation correlated with the growth rate, the degradation stopping when the cosubstrate becomes exhausted or the pH value of the medium falls below 6.5. In a medium with glucose, no lag phase longer than one day was observed concerning growth, sugar and herbicide consumption and formation of metabolic herbicide derivatives (3,5-dibromo-4-hydroxybenzamide and 3,5-dibromo-4-hydroxybenzoic acid). In a medium with ribose, the initial lag of the above processes took 2 d. No formation of other degradation products was detected. Growth inhibition was proportional to the concentration of bromoxynil.

Coagulase negative staphylococci (CoNS) are an emerging cause of native valve endocarditis in community and healthcare settings. We describe a case of a 28-year-old man with no significant risk factors who presented with Staphylococcus pettenkoferi native valve endocarditis. During our patient's initial hospitalization, he was treated for CoNS bacteraemia and subsequently discharged after a protracted hospital course with a transthoracic echocardiogram (TTE) showing no valvular vegetations. However, during the course of his second hospitalization, speciation identified S. pettenkoferi and transoesophageal echocardiogram (TEE) showed aortic valve perforations with new regurgitation raising concern for left sided endocarditis. We postulate that our patient may have been infected with the same CoNS species causing aortic valve endocarditis during his initial hospitalization. This case highlights the importance of recognizing CoNS as a possible causative bacterium in NVE, as well as the importance of obtaining a TEE when evaluating a patient for suspected endocarditis.

Rhizosphere conditions were simulated in a column of 30 g chernozem soil continuously supplied with a solution of synthetic root exudates. The flow rate corresponded to 580 /ug C and 51 /ug N per 1 hour. Nonrhizosphere soil was represented by variants perfused with water. A solution of 1-14C-2, 4-dichlorophenoxyacetic acid (22 /ug C and 7.2 kBq.h−1) was simultaneously continously supplied in both cases. The system was aerated by CO2-free air at 28 °C. Plate counts of bacteria in 1 g soil increased during 4 weeks of cultivation from 4.8 x 108 to 6 x 108 in the nonrhizosphere and to 3.9 x 109 in the rhizosphere variant. During this interval the proportion of bacterial decomposers of the herbicide (14CO2 producers) markedly increased from 9.4 % to 77.0 % in the nonrhizosphere and from 9.4 to 93.7 % in the rhizosphere soil. A steady state was attained after 2 weeks of cultivation. At this stage 16.4 % of the supplied herbicide was evolved in the form of 14CO2 from the nonrhizosphere variant while only 0.2 % was determined as 14CO2 from the rhizosphere soil. 79.1 and 96.3 % of the added radioactivity was trapped by the soil in the nonrhizosphere and rhizosphere variant respectively, or presumably escaped from the system in the form of unmeasured volatile products.