The variation of PbTiO3 bandgap at ferroelectric phase transition.

Optical properties of the PbTiO3 thin films fabricated by chemical solution deposition have been measured with variable angle spectroscopic ellipsometry in the spectral range of 1-6 eV and in the temperature interval from room temperature to 950 K. The optical response functions and band gap energy were determined in the whole temperature range. The direct band gap varies from the value 3.88 eV at room temperature to the value 3.67 eV just above the phase transition. The temperature dependence of the film lattice parameters was also measured by x-ray and it shows a strong correlation with the band gap. The comparison of experimental data with ab initio electronic structure calculations simulating the temperature development of dielectric function and band gap is also presented.

Relativistic Néel-order fields induced by electrical current in antiferromagnets.

We predict that a lateral electrical current in antiferromagnets can induce nonequilibrium Néel-order fields, i.e., fields whose sign alternates between the spin sublattices, which can trigger ultrafast spin-axis reorientation. Based on microscopic transport theory calculations we identify staggered current-induced fields analogous to the intraband and to the intrinsic interband spin-orbit fields previously reported in ferromagnets with a broken inversion-symmetry crystal. To illustrate their rich physics and utility, we consider bulk Mn(2)Au with the two spin sublattices forming inversion partners, and a 2D square-lattice antiferromagnet with broken structural inversion symmetry modeled by a Rashba spin-orbit coupling. We propose an antiferromagnetic memory device with electrical writing and reading.

Electric control of the spin Hall effect by intervalley transitions.

Controlling spin-related material properties by electronic means is a key step towards future spintronic technologies. The spin Hall effect (SHE) has become increasingly important for generating, detecting and using spin currents, but its strength--quantified in terms of the SHE angle--is ultimately fixed by the magnitude of the spin-orbit coupling (SOC) present for any given material system. However, if the electrons generating the SHE can be controlled by populating different areas (valleys) of the electronic structure with different SOC characteristic the SHE angle can be tuned directly within a single sample. Here we report the manipulation of the SHE in bulk GaAs at room temperature by means of an electrical intervalley transition induced in the conduction band. The spin Hall angle was determined by measuring an electromotive force driven by photoexcited spin-polarized electrons drifting through GaAs Hall bars. By controlling electron populations in different (Γ and L) valleys, we manipulated the angle from 0.0005 to 0.02. This change by a factor of 40 is unprecedented in GaAs and the highest value achieved is comparable to that of the heavy metal Pt.

Tetragonal phase of epitaxial room-temperature antiferromagnet CuMnAs.

Recent studies have demonstrated the potential of antiferromagnets as the active component in spintronic devices. This is in contrast to their current passive role as pinning layers in hard disk read heads and magnetic memories. Here we report the epitaxial growth of a new high-temperature antiferromagnetic material, tetragonal CuMnAs, which exhibits excellent crystal quality, chemical order and compatibility with existing semiconductor technologies. We demonstrate its growth on the III-V semiconductors GaAs and GaP, and show that the structure is also lattice matched to Si. Neutron diffraction shows collinear antiferromagnetic order with a high Néel temperature. Combined with our demonstration of room-temperature-exchange coupling in a CuMnAs/Fe bilayer, we conclude that tetragonal CuMnAs films are suitable candidate materials for antiferromagnetic spintronics.

Systematic study of Mn-doping trends in optical properties of (Ga,Mn)As.

We report on a systematic study of optical properties of (Ga,Mn)As epilayers spanning the wide range of accessible Mn(Ga) dopings. The material synthesis was optimized for each nominal Mn doping in order to obtain films which are as close as possible to uniform uncompensated (Ga,Mn)As mixed crystals. We observe a broad maximum in the mid-infrared absorption spectra whose position exhibits a prevailing blueshift for increasing Mn doping. In the visible range, a peak in the magnetic circular dichroism also shifts with increasing Mn doping. The results are consistent with the description of ferromagnetic (Ga,Mn)As based on the microscopic valence band theory. They also imply that opposite trends seen previously in the optical data on a limited number of samples are not generic and cannot serve as an experimental basis for postulating the impurity band model of ferromagnetic (Ga,Mn)As.

Microscopic analysis of the valence band and impurity band theories of (Ga,Mn)As.

We analyze microscopically the valence and impurity band models of ferromagnetic (Ga,Mn)As. We find that the tight-binding Anderson approach with conventional parametrization and the full potential local-density approximation+U calculations give a very similar band structure whose microscopic spectral character is consistent with the physical premise of the k·p kinetic-exchange model. On the other hand, the various models with a band structure comprising an impurity band detached from the valence band assume mutually incompatible microscopic spectral character. By adapting the tight-binding Anderson calculations individually to each of the impurity band pictures in the single Mn impurity limit and then by exploring the entire doping range, we find that a detached impurity band does not persist in any of these models in ferromagnetic (Ga,Mn)As.

Dilute moment n-type ferromagnetic semiconductor Li(Zn,Mn)As.

We propose to replace Ga in (Ga,Mn)As with Li and Zn as a route to high Curie temperature, carrier mediated ferromagnetism in a dilute moment n-type semiconductor. Superior material characteristics, rendering Li(Zn,Mn)As a realistic candidate for such a system, include high solubility of the isovalent substitutional Mn impurity and carrier concentration controlled independently of Mn doping by adjusting Li-(Zn,Mn) stoichiometry. Our predictions are anchored by ab initio calculations and comparisons with the familiar and directly related (Ga,Mn)As, by the physical picture we provide for the exchange interaction between Mn local moments and electrons in the conduction band, and by analysis of prospects for the controlled growth of Li(Zn,Mn)As materials.

[Successful indirect cardiac massage as a cause of thoracic wall instability and respiratory insufficiency]. / Ucinná neprímá srdecní masáz jako prícina nestability hrudní steny a dechové nedostatecnosti.

The authors in their two cases describe unusual complication after successful indirect cardiac massage which was carried out in terrain. Both patients were then transferred to Dept. of gerontology and metabolic care. However the resuscitation was in both cases successful it caused in these two cachectic oseoporotic patients sternal and costal en block fractures. This iatrogenic trauma of thoracic wall showed up in further cause as a major problem. The patients could not have been disconnected from artificial support of ventilation and therefore their thoracic cage had to be surgically stabilized.

[Adhesion molecules and cytokines in vasculitides]. / Adhezní molekuly a cytokiny u vaskulitíd.

Renal vasculitis syndromes include particular characteristic changes in concentrations of some cytokines in plasma or urine. Preliminary results suggest that the systemic lupus erythematodes with affliction of the kidneys is specifically concomitted by the increase in IL-8, both in plasma and urine. ANCA-positive renal vasculitis syndromes appear to coincide with a typical increase in the synthesis of interleukin-6 in the kidneys. We suggest that the monitoring of individual cytokine levels in plasma and urine will enable to study in greater detail the immunopathogenesis of renal vasculitis syndromes and the extent of local production of cytokines which may cause further progression of renal lesions. (Fig. 4, Tab. 1, Ref. 10.).

[Angiotensin converting enzyme inhibitors in controlled hypotension during spinal surgery]. / Inhibitory angiotenzin konvertujícího enzymu v rízené hypotenzi behem spondylochirurgických výkonu.

BACKGROUND: Controlled hypotension is an advantage during spondylosurgical operations: the objective is to achieve a mean arteriae pressure of 8 kPa (60 mm Hg). The most frequently used 0.01% solution of sodium nitroprusside must be increased in some patients to amounts which involve the risk of intoxication. This applies to patients with an increased sympathoadrenal activity and ready mobilization of the renin-angiotensin system. The objective of the present investigation was to test the inhibitor of the angiotensin converting enzyme in hypotension controlled by nitroprusside. METHODS AND RESULTS: To twenty patients before a spondylosurgical operation as premedication angiotensin converting enzyme inhibitor (ACE)--captopril--was administered, 25 mg by the oral route. The control group was formed by 20 patients with spondylosurgery under controlled hypotension with nitroprusside administration. The effect of captopril was manifested by a reduced amount of nitroprusside needed to maintain the median pressure of 8 kPa; in the captopril group 1.073 +/- 0.52 microgram.kg-1.min-1 was used, as compared with 1.786 +/- 1.04 micrograms.min-1 in the control group (p < 0.01). Concurrently monitored values of plasma renin activity were higher in the patients given captopril: 7.352 +/- 5.75 nmol.l-1, as compared with 5.583 +/- 3.73 nmol.l-1 (p < 0.05). CONCLUSIONS: Premedication with ACE inhibitor (captopril), even when administered in small doses via p. o., reduced the sodium nitroprusside consumption by as much as 60%. The elevated plasma renin values were objective evidence of the effect of captopril.

[Ecotoxicologic relations on a large pig-fattening farm located in a lignite mining area and near and solid-fuel electical power plant]. / Ekotoxikologické vztahy ve velkovýkrmne prasat lokalizované v oblasti tezby lignitu a tepelné elektrárny.

Major contaminants identified in 1983-1984 on a pig fattening farm with an output of 60,000 pigs per annum, located in a lignite mining area and near a solid fuel power plant, were mercury, cadmium, lead, chromium and aflatoxin B1 (Tab. I, II, III, IV). Feed samples were collected from througs to assess the contamination load at feed uptake. Permissible concentrations of mercury, chromium, cadmium, aflatoxin B1, lead and atrazin in the feed were exceeded in 56, 50, 31, 19, 6 and 6% samples, respectively (Tab. I). Stable dust deposits, in which the contaminants concentrate, (Tab. I) proved to be a suitable material for assessing the type and level of environmental contamination. Permissible concentrations of mercury, cadmium and lead in porcine muscles were exceeded in 65, 51 and 24% samples, respectively (Tab. III). Corresponding values of mercury, cadmium, lead and aflatoxin B1 in the liver were 27, 27, 16 and 3%, respectively (Tab. III) and those of mercury, lead and chromium in kidneys 24, 22 and 5%, respectively (Tab. III). Rather surprisingly, elevated pancreatic concentrations of aflatoxin B1 were found (Tab. IV). Pigs fattened in the contaminated environment (i.e. fed contaminated feed mixtures, inspiring contaminated dust and absorbing percutaneously contaminants form dust deposits on the body surface) showed: 1) Impairment of the genetic apparatus (percentage of aberrant peripheral leucocytes elevated to 6.2%); 2) a certain degree of immunosuppression (concentrations of IgG, IgM and IgA reduced by 16.9, 45.1 and 45.0%, respectively); 3) higher feed consumption per 1 kg weight gain (4 kg) and lower average daily weight gain (0.57 kg); 4) increased incidence of health disorders (dermatitis in 25%, pancreatopathy in 13%, liver dystrophy in 8% and femoral fracture in 6% of the pigs). Unfortunately, the authors were not allowed to analyse ash and solid emissions from the power plant. Therefore the share of the emissions in the overall environmental contamination on the fattening farm could not be quantified. The personnel, working in the contaminated environment for a prolonged period, is endangered most of all by stable dust, being exposed to its mechanical, chemical, allergic and infectious effects (Tab. I). In addition to the chemical contaminants, 21 mould genera and species, six mite species and numerous saprophytic and some pathogenic bacteria were demonstrated in stable dust samples in our earlier experiments. Consumption of meat and organs from pigs fattened in a contaminated environment is associated with the risk of an increased uptake of various contaminants.(ABSTRACT TRUNCATED AT 400 WORDS)

[Experimental chronic phenylmercuric chloride poisoning in pigs]. / Experimentální chronická intoxikace prasat fenylmerkurichloridem.

Four gilts, sisters from one litter, aged 70 days and weighing 20-24 kg, were used for a trial. Two experimental gilts (P) were administered an experimental feed mixture containing phenylmercury chloride (40 mg/kg). Two control gilts (K) were fed the same mixture but without phenylmercury chloride. P gilts began to lag behind in their growth from day 60 of the experiment, they manifested nonphysiological postures (dog's sitting posture), paresis of hind limbs and uncoordinated movements. P gilts had cloudy, orange-brown urine from day 70 and from day 75 they began to suffer from diarrhoea. Mercury (Hg) contents in urine and blood serum of P gilts were irregularly variable: urine 0.58-2.15 mg/l, blood serum 0.02-0.37 mg/l. Hg content in excrements of P gilts fluctuated from 23 to 26 mg/kg. Vitamin A concentrations in blood serum and liver decreased in P gilts. Phenylmercury chloride feeding caused mutagenic changes in peripheral lymphocytes of P gilts (an increase in the number of aberrant cells from 2-3% to 8-9%) and reduced IgA, IgM and IgG immunoglobulin levels in blood serum. Pathological lesions were observed in the colon, kidneys and liver. None of the above-mentioned changes were observed in K gilts. Increased resistance to the negative effects of Hg was found in one experimental gilt. In comparison with K gilts, Hg concentrations in P gilts after 130 days of the experiment increased as follows: 427 times in kidneys, 333 times in liver, 106 times in guts, 71 times in pancreas, 53 times in ovaries, 50 times in muscles, 47 times in bristles and 16 times in the brain.(ABSTRACT TRUNCATED AT 250 WORDS)

[Reoperation for recurrent carcinoma of the large intestine and rectum]. / Reoperace pro recidívu karcinomu tlustého streva a konecníku.

Based on their own experience with reoperations of relapses of colorectal carcinoma the authors draw attention to the very poor results of these operations; even in case of early detection of a relapse of the tumour in the majority only a palliative operation could be performed and only in 10% patients a radical operation. Therefore the authors emphasize prevention of relapses.

Amino acid composition of meat, fatty acid composition of fat and content of some chemical elements in the tissues of male lambs fed monensin or lasalocid.

Tissues of slaughtered male lambs fed for 56 days on a feed mixture, supplemented with either monensin or lasalocid, were analysed and compared with tissues of control lambs fed similarly but without ionophore supplement. The analyses carried out were for the amino acid composition of meat, fatty acid composition of intramuscular and perirenal fat, and for some chemical elements in meat, liver and kidneys. In meat of both supplemented groups of lambs a significant increase in tyrosine was observed. In the fat tissues of monensin-fed lambs a higher proportion of odd-carbon acid (heptadecanoic acid) was observed; differences in some other fatty acids among the groups were also found. Some significant differences in the chemical elements analysed were observed, particularly in liver, few in kidneys and none in the muscle of ionophore-fed groups. The quality of meat, as judged by the analyses for the substances mentioned, was little changed by supplementation of monensin or lasalocid in the feed of male lambs.

[Monitoring chromosome mutations in large-scale breeding operations]. / Monitorování chromozomálních mutací ve velkochovech.

The frequency of chromosomal aberrations and exchanges of sister chromatids (SCEs) in peripheral lymphocytes was studied in 65 pigs from five large breeding herds. Four groups comprised fattened pigs and the fifth group consisted of sows from a large multiplier breeding herd. During the investigation, the dust from the sites was analyzed for the presence of zinc, lead, cadmium, mercury, aflatoxin B1, PCB, DDT, and lindane. The average frequency of aberrant cells (AB.B) in the pigs of group I was 3.85 +/- 1.60%, in group II 2.10 +/- 1.52%, in group III 5.01 +/- 2.1%, in group IV 3.50 +/- 1.58%, and in group V 6.20 +/- 3.21%. The cytogenetic finding corresponded to the differences in the amount of foreign substances found in the dust on the premises where the animals of all groups were kept. The average frequency of the SCEs was 7.00 +/- 1.10 (I), 6.51 +/- 0.89 (II), 6.92 +/- 0.72 (III), 7.10 +/- 0.85 (IV) and 7.06 +/- 1.47 (V) per one cell. Statistically significant differences in the numbers of AB.B. were recorded between groups II and I, II and IV, I and III, IV and V (p less than 0.05) and between groups II and III, II and V (p less than 0.01). There was no statistically significant difference in the frequency of SCEs. The determination of the frequency of chromosomal aberrations can be used for the hygienic control of the degree of exposure of pigs to mutagens.

[Foreign substances in the meat and organs of bulls and pigs fed with pastes made from household and food industry waste in addition to pastes made from poultry droppings]. / Cizorodé látky v mase a orgánech býku a prasat po zkrmování pasty z kuchynských a potravinárských odpadu vcetne pasty s drubezím trusem.

The residues of antimicrobial substances, some chlorinated and organophosphate pesticides and chemical elements were studied in the meat and organs of a group of bulls fed food-waste paste for 240 days and a group of bulls fed the same paste with an addition of poultry waste. These residues were also studied in the tissues of pigs fed the food-waste paste for 135 and 151 days until slaughter. The feed ingredients were also examined during the feeding trials. Although some of the residues under study were found in the tissues of the test animals at increased amounts, their concentrations were diluted in the tissues in the majority of cases when the feed pastes were administered. All residue contents recorded in the tissues remained below the permissible limits as given in valid instructions and directives so that the products, i. e. meat and organs, could be deemed digestible on the basis of hygienic evaluation. Hence, from the point of view of the occurrence of residues of foreign substances in edible tissues, the administration of food-waste pastes to farm animals can be considered as admissible.