Study of sodium tellurite glass using the thermally stimulated depolarization current technique (TSDC)

In order to have a better understanding of the role of the structure and the defects involved in the polarization processes in an 85TeO(2)-15Na(2)O mol% glass, we used the thermally stimulated depolarization currents (TSDC technique). The TSDC of the non-irradiated sample presented a strong negative peak of current at the temperature of 340 K, preceded by a relatively weak positive peak at about 300 K. after different d.c. voltages of 1200, 1500 and 2000 V were applied. No response was obtained with 1000 V. but the peak intensity increased considerably for voltages above 1200 V. After gamma-irradiation of 25 and 50 KGy doses, a depolarization of the negative peak was observed in the sample submitted to 25 KGy, whereas for the sample irradiated with 50 KGy, six TSDC peaks appeared at regular intervals of 5 KGy, in the temperature range of 100 and 300 K. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.

Use of lithium niobate detector for measuring X-ray intensity in mammographic range

A detector system that can measure X-ray intensity in the mammographic range of 22 to 36 kVp (equivalent photon energies ofthe beam between 11 and 15 keV) is presented. It consists of a lithium mobate detector and a high-sensitivity current-to-voltage converter.

Evaluation of zona pellucida birefringence intensity during in vitro maturation of oocytes from stimulated cycles

Background: This study evaluated whether there is a relationship between the zona pellucida birefringence (ZP-BF) intensity and the nuclear (NM) and cytoplasmic (CM) in vitro maturation of human oocytes from stimulated cycles.Results: The ZP-BF was evaluated under an inverted microscope with a polarizing optical system and was scored as high/positive (when the ZP image presented a uniform and intense birefringence) or low/negative (when the image presented moderate and heterogeneous birefringence). CM was analyzed by evaluating the distribution of cortical granules (CGs) throughout the ooplasm by immunofluorescence staining. CM was classified as: complete, when CG was localized in the periphery; incomplete, when oocytes presented a cluster of CGs in the center; or in transition, when oocytes had both in clusters throughout cytoplasm and distributed in a layer in the cytoplasm periphery Nuclear maturation: From a total of 83 germinal vesicle (GV) stage oocytes, 58 of oocytes (69.9%) reached NM at the metaphase II stage. From these 58 oocytes matured in vitro, the high/positively scoring ZP-BF was presented in 82.7% of oocytes at the GV stage, in 75.8% of oocytes when at the metaphase I, and in 82.7% when oocytes reached MII. No relationship was observed between NM and ZP-BF positive/negative scores (P = 0.55). These variables had a low Pearson's correlation coefficient (r = 0.081). Cytoplasmic maturation: A total of 85 in vitro-matured MII oocytes were fixed for CM evaluation. Forty-nine oocytes of them (57.6%) showed the complete CM, 30 (61.2%) presented a high/positively scoring ZP-BF and 19 (38.8%) had a low/negatively scoring ZP-BF. From 36 oocytes (42.3%) with incomplete CM, 18 (50%) presented a high/positively scoring ZPBF and 18 (50%) had a low/negatively scoring ZP-BF. No relationship was observed between CM and ZP-BF positive/negative scores (P = 0.42). These variables had a low Pearson's correlation coefficient (r = 0.11).Conclusions: The current study demonstrated an absence of relationship between ZP-BF high/positive or low/negative score and nuclear and cytoplasmic in vitro maturation of oocytes from stimulation cycles.

BARRIER VOLTAGE DEFORMATION OF ZNO VARISTORS BY CURRENT PULSE

The phenomenon of electrical degradation in ZnO varistors was studied by application of high-intensity current pulses. A wave shape of 8 X 20-mu-s and rectangular waves of 1 and 2 ms were used. The degradation was estimated by reference electric-field variation and by Schottky voltage barrier deformation. The results showed that current pulses reduce both the height and the width of the barrier voltage. It was also observed that the donor density N(d) did not change but the surface states density N(s) decreased with degradation.

Ferroelectric ceramic/polymer composite for measuring X-ray intensity in the ortovoltage range

Pyroelectric sensors work as a thermal transducer converting the non-quantified thermal flux into the output measurable quantity of electrical charge, voltage or current. Ferroelectric ceramics and ferroelectric polymers have been extensively used as thermal detectors. More recently the research in the field of pyroelectricity has been concentrated on discovering materials with higher figures of merit (FOM), which means better sensing materials. Composite materials obtained with ferroelectric ceramics embedded in polymer host have received great attention because of their formability, mechanical resistance and the possibility to change their dielectric property varying the volume fraction of ceramic particles. In this work composite films made of modified lead titanate (PZ34) and poly(ether-ether-ketone) (PEEK) were characterized and used as sensing element to measure X-ray intensity in the ortovoltage range (120 - 300 kVp). The sensor response varies from 2.70 V to 0.80 V in the energy fluency range of 6.30 to 37.20 W/m(2). Furthermore the absorbed energy was analyzed as a function of the ionizing energy. The results indicate that the PZ34/PEEK composite with 60/40 vol.% can be useful to monitor X-ray radiation therapy.

Serum and plasma hormonal concentrations are sensitive to periods of intensity and volume of soccer training

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Assessment of Gastrointestinal Motility in Renal Transplant Recipients by Alternate Current Biosusceptometry

Background. Gastrointestinal (GI) complications are common after renal transplantation, mainly owing to immunosuppressive therapy. Assessment of GI transit time can facilitate rational management of these disorders.Objective. We evaluate the GI transit parameters in renal transplant recipients taking tacrolimus, azathioprine, and prednisone with the use of the alternate current biosusceptometry (ACB) technique and compared them with healthy volunteers.Methods. Ten renal transplant recipients and 10 healthy volunteers were enrolled in this study. After an overnight fast, patients and volunteers ingested a standard meal containing magnetic markers. The biomagnetic monitoring was performed at 10-minute intervals for at least 8 hours to obtain gastric emptying as well as the colonic arrival time-intensity curves. Mean gastric emptying time (MGET), mean colon arrival time (MCAT), and mean small intestinal transit time (MSITT) were quantified and compared between control and patient groups with results expressed as mean +/- SD.Results. The MGET measured by the ACB technique was 48 +/- 31 minutes and 197 +/- 50 minutes for patients and healthy subjects, respectively. MSITT and MCAT values calculated for patients versus volunteers were 171 +/- 71 minutes versus 197 +/- 71 minutes and 219 +/- 83 minutes versus 373 +/- 52 minutes, respectively. Renal transplant recipients showed significantly faster; gastric emptying and colon arrival times (P < .001) compared with normal volunteers; however, small intestinal transit time was not significantly different (P = .44).Conclusions. In stable renal transplant recipients, the GI transit parameters were significantly faster than in normal healthy volunteers. ACB sensors are versatile technologies that can be used for clinical research, because they offer an excellent opportunity to evaluate GI transit in a noninvasive manner without the use of ionizing radiation.

Microcontrolled pyro-electric instrument for measuring X-ray intensity in mammography

A novel instrument for measurement of X-ray intensity from mammography consists of a sensitive pyro-electric detector, a high-sensitivity, low-noise current-to-voltage converter, a microcontroller and a digital display. The heart of this device, and what makes it unique is the pyro-electric detector, which measures radiation by converting heat from absorbed incident X-rays into an electric current. This current is then converted to a voltage and digitised. The detector consists of a ferro-electric crystal; two types were tested; lithium tantalate and lithium niobate. X-ray measurement in mammography is challenging because of its relatively low photon energy range, from 11 keV to 15 keV equivalent mean energy, corresponding to a peak tube potential from 22 to 36 kV. Consequently, energy fluence rate or intensity is low compared with that of common diagnostic X-ray. The instrument is capable of measuring intensities as low as 0.25 mWm -2 with precision greater than 99%. Not only was the instrument capable of performing in the clinical environment, with high background electromagnetic interference and vibration, but its performance was not degraded after being subjected to 140 roentgen (3.6 × 10 -2 C kg -2 air) as measured by piezo-electric (d 33) or pyro-electric coefficients. © IFMBE 2005.

Measurement of orthovoltage X-ray intensity with a lithium niobate transducer

A microcontrolled instrument for measuring the energy fluence rate (or intensity) of X-ray pulses in the orthovoltage range of 120 to 300 kV is described. The prototype instrument consists of a pyroelectric sensor, a low-noise highsensitivity current-to-voltage converter, a microcontroller and a digital display. The response of the instrument is nonlinear with the intensity of the radiation. The precision is better than 3%. The equipment is inexpensive, rugged, simple to construct and has good long-term stability. © 2009 Springer-Verlag.

Optical transition radiation used in the diagnostic of low energy and low current electron beams in particle accelerators

Optical transition radiation (OTR) plays an important role in beam diagnostics for high energy particle accelerators. Its linear intensity with beam current is a great advantage as compared to fluorescent screens, which are subject to saturation. Moreover, the measurement of the angular distribution of the emitted radiation enables the determination of many beam parameters in a single observation point. However, few works deals with the application of OTR to monitor low energy beams. In this work we describe the design of an OTR based beam monitor used to measure the transverse beam charge distribution of the 1.9-MeV electron beam of the linac injector of the IFUSP microtron using a standard vision machine camera. The average beam current in pulsed operation mode is of the order of tens of nano-Amps. Low energy and low beam current make OTR observation difficult. To improve sensitivity, the beam incidence angle on the target was chosen to maximize the photon flux in the camera field-of-view. Measurements that assess OTR observation (linearity with beam current, polarization, and spectrum shape) are presented, as well as a typical 1.9-MeV electron beam charge distribution obtained from OTR. Some aspects of emittance measurement using this device are also discussed. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4748519]

Increasing Intensity of TENS Prevents Analgesic Tolerance in Rats

Transcutaneous electrical nerve stimulation (TENS) reduces hyperalgesia and pain. Both low-frequency (LF) and high-frequency (HF) TENS, delivered at the same intensity (90% motor threshold [MT]) daily, result in analgesic tolerance with repeated use by the fifth day of treatment. The current study tested 1) whether increasing intensity by 10% per day prevents the development of tolerance to repeated TENS; and 2) whether lower intensity TENS (50% MT) produces an equivalent reduction in hyperalgesia when compared to 90% MT TENS. Sprague-Dawley rats with unilateral knee joint inflammation (3% carrageenan) were separated according to the intensity of TENS used: sham, 50% LF, 50% HF, 90% LF, 90% HF, and increased intensity by 10% per day (IF and HF). The reduced mechanical withdrawal threshold following the induction of inflammation was reversed by application of TENS applied at 90% MT intensity and increasing intensity for the first 4 days. On the fifth day, the groups that received 90% MT intensity showed tolerance. Nevertheless, the group that received an increased intensity on each day still showed a reversal of the mechanical withdrawal threshold with TENS. These results show that the development of tolerance can be delayed by increasing intensity of TENS. Perspective: Our results showed that increasing intensity in both frequencies of TENS was able to prevent analgesic tolerance. Results from this study suggest that increasing intensities could be a clinical method to prevent analgesic tolerance and contribute to the effective use of TENS in reducing inflammatory pain and future clinical trials. (c) 2012 by the American Pain Society

The structure of planktonic communities under variable coastal upwelling conditions off Cape Ghir (31ºN), in the Canary Current System (NW Africa)

Universidad de Las Palmas de Gran Canaria. Facultad de Ciencias del Mar. Programa de doctorado en Oceanografía. Diploma de Estudios Avanzados

Determination of the minimum alveolar concentration of isoflurane in Shetland ponies using constant current or constant voltage electrical stimulation

OBJECTIVE: To determine the minimum alveolar concentration (MAC) of isoflurane in Shetland ponies using a sequence of three different supramaximal noxious stimulations at each tested concentration of isoflurane rather than a single stimulation. STUDY DESIGN: Prospective, experimental trial. ANIMALS: Seven 4-year-old, gelding Shetland ponies. METHODS: The MAC of isoflurane was determined for each pony. Three different modes of electrical stimulation were applied consecutively (2 minute intervals): two using constant voltage (90 V) on the gingiva via needle- (CVneedle) or surface-electrodes (CVsurface) and one using constant current (CC; 40 mA) via surface electrodes applied to the skin over the digital nerve. The ability to clearly interpret the responses as positive, the latency of the evoked responses and the inter-electrode resistance were recorded for each stimulus. RESULTS: Individual isoflurane MAC (%) values ranged from 0.60 to 1.17 with a mean (+/-SD) of 0.97 (+/-0.17). The responses were more clearly interpreted with CC, but did not reach statistical significance. The CVsurface mode produced responses with a longer delay. The CVneedle mode was accompanied by variable inter-electrode resistances resulting in uncontrolled stimulus intensity. At 0.9 MAC, the third stimulation induced more positive responses than the first stimulation, independent of the mode of stimulation used. CONCLUSIONS: The MAC of isoflurane in the Shetland ponies was lower than expected with considerable variability among individuals. Constant current surface electrode stimulations were the most repeatable. A summation over the sequence of three supramaximal stimulations was observed around 0.9 MAC. CLINICAL RELEVANCE: The possibility that Shetland ponies require less isoflurane than horses needs further investigation. Constant current surface-electrode stimulations were the most repeatable. Repetitive supramaximal stimuli may have evoked movements at isoflurane concentrations that provide immobility when single supramaximal stimulation was applied.

Community mean traits as additional indicators to monitor effects of land-use intensity on grassland plant diversity

Semi-natural grasslands, biodiversity hotspots in Central-Europe, suffer from the cessation of traditional land-use. Amount and intensity of these changes challenge current monitoring frameworks typically based on classic indicators such as selected target species or diversity indices. Indicators based on plant functional traits provide an interesting extension since they reflect ecological strategies at individual and ecological processes at community levels. They typically show convergent responses to gradients of land-use intensity over scales and regions, are more directly related to environmental drivers than diversity components themselves and enable detecting directional changes in whole community dynamics. However, probably due to their labor- and cost intensive assessment in the field, they have been rarely applied as indicators so far. Here we suggest overcoming these limitations by calculating indicators with plant traits derived from online accessible databases. Aiming to provide a minimal trait set to monitor effects of land-use intensification on plant diversity we investigated relationships between 12 community mean traits, 2 diversity indices and 6 predictors of land-use intensity within grassland communities of 3 different regions in Germany (part of the German ‘Biodiversity Exploratory’ research network). By standardization of traits and diversity measures, use of null models and linear mixed models we confirmed (i) strong links between functional community composition and plant diversity, (ii) that traits are closely related to land-use intensity, and (iii) that functional indicators are equally, or even more sensitive to land-use intensity than traditional diversity indices. The deduced trait set consisted of 5 traits, i.e., specific leaf area (SLA), leaf dry matter content (LDMC), seed release height, leaf distribution, and onset of flowering. These database derived traits enable the early detection of changes in community structure indicative for future diversity loss. As an addition to current monitoring measures they allow to better link environmental drivers to processes controlling community dynamics.

Investigating the sensitivity of hurricane intensity and trajectory to sea surface temperatures using the regional model WRF

The influence of sea surface temperature (SST) anomalies on the hurricane characteristics are investigated in a set of sensitivity experiments employing the Weather Research and Forecasting (WRF) model. The idealised experiments are performed for the case of Hurricane Katrina in 2005. The first set of sensitivity experiments with basin-wide changes of the SST magnitude shows that the intensity goes along with changes in the SST, i.e., an increase in SST leads to an intensification of Katrina. Additionally, the trajectory is shifted to the west (east), with increasing (decreasing) SSTs. The main reason is a strengthening of the background flow. The second set of experiments investigates the influence of Loop Current eddies idealised by localised SST anomalies. The intensity of Hurricane Katrina is enhanced with increasing SSTs close to the core of a tropical cyclone. Negative nearby SST anomalies reduce the intensity. The trajectory only changes if positive SST anomalies are located west or north of the hurricane centre. In this case the hurricane is attracted by the SST anomaly which causes an additional moisture source and increased vertical winds.