Growth and optical investigations of high quality individual CdTe/(Cd,Mg)Te core/shell nanowires.

CdTe nanowires with the average diameter of only 40 nm coated with (Cd,Mg)Te shells are grown using Au-catalyzed vapor-liquid-solid growth mechanism in a system for molecular beam epitaxy. High optical quality of individual nanowires is revealed by means of low temperature cathodoluminescence and micro-luminescence. It is found that, the optical emission spectrum consists mostly of the near band edge emission without any significant contribution of defect related luminescence. Moreover, the importance of surface passivation with (Cd,Mg)Te coating shells is demonstrated.

Production of arabitol by yeasts: current status and future prospects.

Arabitol belongs to the pentitol family and is used in the food industry as a sweetener and in the production of human therapeutics as an anticariogenic agent and an adipose tissue reducer. It can also be utilized as a substrate for chemical products such as arabinoic and xylonic acids, propylene, ethylene glycol, xylitol and others. It is included on the list of 12 building block C3-C6 compounds, designated for further biotechnological research. This polyol can be produced by yeasts in the processes of bioconversion or biotransformation of waste materials from agriculture, the forest industry (l-arabinose, glucose) and the biodiesel industry (glycerol). The present review discusses research on native yeasts from the genera Candida, Pichia, Debaryomyces and Zygosaccharomyces as well as genetically modified strains of Saccharomyces cerevisiae which are able to utilize biomass hydrolysates to effectively produce L- or D-arabitol. The metabolic pathways of these yeasts leading from sugars and glycerol to arabitol are presented. Although the number of reports concerning microbial production of arabitol is rather limited, the research on this topic has been growing for the last several years, with researchers looking for new micro-organisms, substrates and technologies.

Coherent coupling of excitons and trions in a photoexcited CdTe/CdMgTe quantum well.

We present zero-, one-, and two-quantum two-dimensional coherent spectra of excitons and trions in a CdTe/(Cd,Mg)Te quantum well. The set of spectra provides a unique and comprehensive picture of the coherent nonlinear optical response. Distinct peaks in the spectra are manifestations of exciton-exciton and exciton-trion coherent coupling. Excellent agreement using density matrix calculations highlights the essential role of many-body effects on the coupling. Strong exciton-trion coherent interactions open up the possibility for novel conditional control schemes in coherent optoelectronics.

Activation of an intense near band edge emission from ZnTe/ZnMgTe core/shell nanowires grown on silicon.

The absence of luminescence in the near band edge energy region of Te-anion based semiconductor nanowires grown by gold catalyst assisted molecular beam epitaxy has strongly limited their applications in the field of photonics. In this paper, an enhancement of the near band edge emission intensity from ZnTe/ZnMgTe core/shell nanowires grown on Si substrates is reported. A special role of the use of Si substrates instead of GaAs substrates is emphasized, which results in an increase of the near band edge emission intensity by at least one order of magnitude accompanied by a simultaneous reduction of the defect related luminescence. A possible explanation of this effect relies on the presence of Ga-related deep level defects in structures grown on GaAs substrates, which are absent when Si substrates are used. Monochromatic mapping of the cathodoluminescence clearly confirms that the observed emission originates, indeed, from the ZnTe/ZnMgTe core/shell nanowires, whereas individual objects are studied by means of microphotoluminescence.

Circadian integration of sleep-wake and feeding requires NPY receptor-expressing neurons in the mediobasal hypothalamus.

Sleep and feeding rhythms are highly coordinated across the circadian cycle, but the brain sites responsible for this coordination are unknown. We examined the role of neuropeptide Y (NPY) receptor-expressing neurons in the mediobasal hypothalamus (MBH) in this process by injecting the targeted toxin, NPY-saporin (NPY-SAP), into the arcuate nucleus (Arc). NPY-SAP-lesioned rats were initially hyperphagic, became obese, exhibited sustained disruption of circadian feeding patterns, and had abnormal circadian distribution of sleep-wake patterns. Total amounts of rapid eye movement sleep (REMS) and non-REMS (NREMS) were not altered by NPY-SAP lesions, but a peak amount of REMS was permanently displaced to the dark period, and circadian variation in NREMS was eliminated. The phase reversal of REMS to the dark period by the lesion suggests that REMS timing is independently linked to the function of MBH NPY receptor-expressing neurons and is not dependent on NREMS pattern, which was altered but not phase reversed by the lesion. Sleep-wake patterns were altered in controls by restricting feeding to the light period, but were not altered in NPY-SAP rats by restricting feeding to either the light or dark period, indicating that disturbed sleep-wake patterns in lesioned rats were not secondary to changes in food intake. Sleep abnormalities persisted even after hyperphagia abated during the static phase of the lesion. Results suggest that the MBH is required for the essential task of integrating sleep-wake and feeding rhythms, a function that allows animals to accommodate changeable patterns of food availability. NPY receptor-expressing neurons are key components of this integrative function.

Spirulina enhances the viability of Lactobacillus rhamnosus E/N after freeze-drying in a protective medium of sucrose and lactulose.

AIMS: Response surface methodology (RSM) was used to optimize a protective medium for enhancing the viability of Lactobacillus rhamnosus E/N cells during lyophilization. METHODS AND RESULTS: Spirulina, sucrose and lactulose were selected, on the basis of a Plackett-Burman factorial design, as important protectants having the following protective effects on cell viability: 102.025, 36.885 and -34.42, respectively. A full-factorial central composite design was applied to determine optimal levels of three used agents. CONCLUSION: The optimal protective medium composition was determined to be: Spirulina 1.304% (w/v), lactulose 5.48% (w/v), and sucrose 13.04% (w/v) (Polish Patent P-393189). The predictive value of cell viability in this medium was 89.619%, and experimental viability obtained during freeze-drying was 87.5%. SIGNIFICANCE AND IMPACT OF THE STUDY: In this study, Spirulina was used for the first time as the protective agent in freeze-drying medium, significantly increasing lactobacilli viability and giving synbiotic character of the final product.

Polarimetry of photon echo on charged and neutral excitons in semiconductor quantum wells.

Coherent optical spectroscopy such as four-wave mixing and photon echo generation deliver rich information on the energy levels involved in optical transitions through the analysis of polarization of the coherent response. In semiconductors, it can be applied to distinguish between different exciton complexes, which is a highly non-trivial problem in optical spectroscopy. We develop a simple approach based on photon echo polarimetry, in which polar plots of the photon echo amplitude are measured as function of the angle φ between the linear polarizations of the two exciting pulses. The rosette-like polar plots reveal a distinct difference between the neutral and charged exciton (trion) optical transitions in semiconductor nanostructures. We demonstrate this experimentally by photon echo polarimetry of a CdTe/(Cd, Mg)Te quantum well. The echoes of the trion and donor-bound exciton are linearly polarized at the angle 2φ with respect to the first pulse polarization and their amplitudes are weakly dependent on φ. While on the exciton the photon echo is co-polarized with the second exciting pulse and its amplitude scales as cosφ.

Low voltage control of exchange coupling in a ferromagnet-semiconductor quantum well hybrid structure.

Voltage control of ferromagnetism on the nanometer scale is highly appealing for the development of novel electronic devices with low power consumption, high operation speed, reliable reversibility and compatibility with semiconductor technology. Hybrid structures based on the assembly of ferromagnetic and semiconducting building blocks are expected to show magnetic order as a ferromagnet and to be electrically tunable as a semiconductor. Here, we demonstrate the electrical control of the exchange coupling in a hybrid consisting of a ferromagnetic Co layer and a semiconductor CdTe quantum well, separated by a thin non-magnetic (Cd,Mg)Te barrier. The electric field controls the phononic ac Stark effect-the indirect exchange mechanism that is mediated by elliptically polarized phonons emitted from the ferromagnet. The effective magnetic field of the exchange interaction reaches up to 2.5 Tesla and can be turned on and off by application of 1V bias across the heterostructure.

Synergy between leptin and cholecystokinin (CCK) to control daily caloric intake.

Both cholecystokinin (CCK), a short-term meal-related satiety signal, and the ob protein leptin, a postulated long-term adiposity hormone, are thought to be important signals in the multiple interacting systems that control appetite and adiposity. We hypothesized that these hormones may synergistically interact to suppress feeding. Following IP administration of leptin (two doses of 50 micrograms each) and CCK (2, 4, 8, or 16 micrograms) total daily caloric intake was significantly reduced by leptin and CCK compared to leptin alone. These results support the hypothesis that CCK and leptin may synergistically interact to control long-term feeding.

Locomotion induces changes in Trk B receptors in small diameter cells of the spinal cord.

INTRODUCTION AND METHODS: Locomotor training leads to improvement of stepping ability in animals after spinal cord transection (1). Recent data point to neurotrophins as possible factors involved in this improvement. Motoneurones synthesising BDNF, NT-4 and NT-3 are a potent source of neurotrophins for the spinal network (2, 3). Physical exercise increases BDNF neurotrophin gene expression in the rat hippocampus (4). If exercise enhances BDNF expression also in the spinal cord, upregulation of its receptor Trk B may occur. To verify this hypothesis we tested whether exercise influences TrkB receptor system in the spinal cord. Six adult, male Wistar rats walked on the treadmill five days a week, 1,000 m daily with the speed of 20 to 25 cm/s. After 4 weeks of training animals were anaesthetised with pentobarbital sodium (80 mg/kg b.w.) and perfused with 0.01 M PBS followed by 2% paraformaldehyde and 0.2% parabenzoquinone in 0.1 M PB. Three non-trained animals were used as controls. Cryostat 40 microns sections were processed free-floating with TrkB polyclonal antibody (1:1,000, Santa Cruz) and ABC Vectastain detection system. Sections were examined under Nikon light microscope and analysed with Image-Pro Plus 4 software. RESULTS AND DISCUSSION: TrkB immunoreactivity (IR) was detected in number of spinal cells at the lumbar level in non-trained animals (Fig. 1A). The strongest IR appeared in the perikarya and processes of small diameter cells rarely scattered in the grey and white matter. The average area of these cells was 50 micron 2 (+/- 10). Exercise increased by over 50% the number of TrkB immunostained small cells (Fig. 1B). An enhancement of perikaryonal immunostaining of these cells was also observed (Fig. 1B, inset). Testing the identity of Trk B IR small diameter cells did not prove their astroglial (GFAP IR) and gabaergic (GAD IR) phenotype in the grey matter. Some of TrkB IR cells in the white matter were astrocytes. Our data point to physical exercise as a potent method to make spinal cells more receptive to neurotrophic stimuli.

[Effect of obesity on the ventilatory capacity of the respiratory system. I. Relation between basic spirometric indicators: vital capacity (VC) and forced expiratory volume (FEV1) and obesity]. / Wplyw otylosci na sprawnosc wentylacyjna ukladu oddechowego. Czesc I. Zwiazek pomiedzy podstawowymi wskaznikami spirometrycznymi: pojemnoscia zyciowa (VC) i natezona objetoscia wydechowa 1 s (FEV1) a otyloscia.

The following procedures have been applied for evaluation of obesity of 1087 men, steel mill workers: all examined men have been divided into intervals of relative body weight (after Lorentz), indices including measurements of the current body weight and height, indices including measurements of the current body weight, height and skinfolds thickness. All examined persons have undergone measurements of spirometric parameters. The strongest correlation with spirometric values was that of the index of obesity including, apart from the body weight and height, also skinfolds thickness. This index of obesity provides good estimation of respiratory efficiency, which diminishes as obesity intensifies.

[Characteristics of glycosylated hemoglobin distribution]. / Charakterystyka rozkladu stezenia glikozylowanej hemoglobiny.

On the basis of 1518 values of concentration of glycosylated Hb in blood of workers responsible for safety in railroad transportation authors tried to calculate the range of normal values of this parameter. It was assumed that distribution of GHb in a healthy part of population is normal. From the primary set of data, values most distant from the arithmetic mean were gradually discarded until distribution of values was as close to the normal distribution as attainable. The best fit to the normal distribution was obtained for 1486 values. The normal range was then 4.6 to 8.6% (mean +/- 2 SD). The normal range was in a good agreement with published data as well as with own analytical experience.

[Effect of obesity on the ventilatory capacity of the respiratory system. II. Reference spirometry values of VC and FEV1 for overweight males]. / Wplyw otylosci na sprawnosc wentylacyjna ukladu oddechowego. Cz. II. Nalezne wartosci spirometryczne VC i FEV1 dla mezczyzn nadmiernie otylych.

642 persons without respiratory and circulatory diseases were selected from 1087 steel mill workers. The examined persons were classified according to the intervals of relative body mass. The relations between spirometric parameters (VC and FEV1) and degree of obesity were studied. For each interval the equations of multiple regression were calculated, taking into account the dependence of VC and FEV1 on age, height and present body mass. The numeric factor from the equation of multiple regression of coefficient describing the dependence of VC on the present body mass was positive in 90-114% and 115-124% intervals but negative in 125-134% and 135% of body mass. In case of FEV1 the negative factor of the same coefficient was not negative until 135% of body mass. A positive correlation of VC and FEV1 with the present body mass in the whole population was shown. If the group of obese persons was formed on the basis of Wot anthropometric index (which included skinfolds thickness, present body mass and height), significantly lower values of VC and FEV1 were found in comparison to non-obese counterparts. For the persons with morbid obesity a new method of calculation of predicted VC and FEV1 values was presented. The equation of multiple regression used for this purpose takes into account the dependence of spirometric values on age and Wot index.

[Evaluation of health status in inhabitants of the protected zone near a steel mill. II. Overweight and obesity]. / Ocena stanu zdrowia mieszkanców strefy ochronnej kombinatu metalurgicznego. II. Nadwaga i otylosc.

In the group of 232 inhabitants of the protective zone of Nowa Huta the Steel-Mill (181 women and 51 men) incidence of overweight and obesity was estimated using the Quetelet and Wot indices. The results were compared with appropriate data obtained for 37 men and 100 women, matched with age and occupation, inhabitants of Tokarnia village, known by favorable microclimate, rarely encountered in polluted areas of southern Poland. It was found that overweight and obesity was present in the group of the protective zone statistically more often than in Tokarnia. The differences were more pronounced for women than for men. Concentrations of serum cholesterol and triglycerides were also compared. Distribution of cholesterol in examined groups was similar to the distribution of the Quetelet index, differences of arithmetic means being statistically significant, whereas concentration of triglycerides was remarkably similar in all groups under investigation. In this paper rarely used method of data presentation was applied. From histograms of given parameter normalised curves were derived and served as a representation of parameter distribution in the studied population. This method grossly alleviated task of comparison and evaluation of obtained data.

[Risk of coronary heart disease in metallurgy employees in light of prospective examinations]. / Ryzyko choroby niedokrwiennej serca u hutników w swietle badania prospektywnego.

The group of physical workers of metallurgic plant (average period of employment was 12.4 +/- 6.4 years) consisting of 1100 men aged from 20 to 59 years, was underwent double medical examination in 5 years interval in standard clinical conditions. The 8 risk factors of coronary heart disease (CHD): aged, sex, family history, systolic blood pressure, cholesterol blood concentration, body weight, cigarette smoking and professional physical activity were analysed. Each factor was graded from "0" to "8" points. To evaluate individual risk of CHD all points were summed to give the total score. It was found, in both examinations, that most of examined persons showed an average risk of CHD. The second examination (5 years after the first) demonstrated an increase of percent the workers with higher risk of CHD. The smoking habit and overweight were the most important among risk factors in the population studied.