Absolute calibration of the conical crystal configuration of the zinc spectrometer (ZSPEC) at the OMEGA laser facility.

In this study, we present the absolute calibration of the conical crystal for the zinc spectrometer (ZSPEC), an x-ray spectrometer at the OMEGA laser facility at the Laboratory for Laser Energetics. The ZSPEC was originally designed to measure x-ray Thomson scattering using flat or cylindrically curved highly oriented pyrolytic graphite crystals centered around Zn He-alpha emission at 9 keV. To improve the useful spectral range and collection efficiency of the ZSPEC, a conical highly annealed pyrolytic graphite crystal was fabricated for the ZSPEC. The conically bent crystal in the Hall geometry produces a line focus perpendicular to the spectrometer axis, corresponding to the detector plane of electronic detectors at large scale laser facilities such as OMEGA, extending the useful range of the spectrometer to 7-11 keV. Using data collected using a microfocus Mo x-ray source, we determine important characteristics of ZSPEC such as the dispersion, spatial resolution, and absolute sensitivity of the instrument. A ray-trace model of ZSPEC provides another point of agreement in calculations of the ZSPEC dispersion and crystal response.

Conduction mechanism and switchable photovoltaic effect in (1 1 1) oriented BiFe0.95Mn0.05O3 thin film.

Epitaxial 200 nm BiFe0.95Mn0.05O3 (BFO) film was grown by pulsed laser deposition (PLD) on (1 1 1) oriented SrTiO3 substrate buffered with a 50 nm thick SrRuO3 electrode. The BFO thin film shows a rhombohedral structure and a large remnant polarization of Pr = 104 µC cm-2. By comparing I(V) characteristics with different conduction models we reveal the presence of both bulk limited Poole-Frenkel and Schottky interface mechanisms and each one dominates in a specific range of temperature. At room temperature (RT) and under 10 mW laser illumination, the as grown BFO film presents short-circuit current density (J sc) and open circuit voltage (V oc) of 2.25 mA cm-2 and -0.55 V respectively. This PV effect can be switched by applying positive voltage pulses higher than the coercive field. For low temperatures a large V oc value of about -4.5 V (-225 kV cm-1) is observed which suggests a bulk non-centrosymmetric origin of the PV response.

Kinetic Energy of Emerging Neutrons Produced by Photodisintegration in a Medical Linear Accelerator / Energía cinética de neutrones emergentes producidos por fotodesintegración en un acelerador médico lineal

When a gamma photon interacts with a target nucleus a nuclear reaction can be generated, producing as a consequence the expulsion of particles from the atomic nucleus, this process is called photodisintegration. For this work, are of interest nuclear reactions of photodisintegration in which neutrons are ejected due to the interaction of photons with atomic nuclei of different materials in a linear accelerator for medical use. In this paper, the kinetic energy of photoneutrons produced by interactions with atomic nuclei of 184W, 63Cu, 27Al and 12C, which are some of the materials that constitute the head of a medical linear accelerator, is calculated. Also, the nuclei present in the construction materials of the room and the maze of the accelerator, such as, 23Na, 40Ca and 28Si, as also in the human body, ²H, 14N and 16O, are considered. It derives an exact theoretical expression, which has a linear dependence of the energy of the produced neutrons relative to the incident photon energy. It is found that, in the majority of cases, just photons with energies above 10 MV contribute to the production of neutrons. The values calculated from the expression obtained in this work are in good agreement with those reported in the literature, that are obtained by other approaches.

Cuando un fotón gamma interactúa con un núcleo blanco una reacción nuclear puede ser generada, produciendo como consecuencia la expulsión de partículas del núcleo atómico, este proceso se denomina fotodesintegración. Para este trabajo, son de interés las reacciones nucleares de fotodesintegración en las que los neutrones son expulsados debido a la interacción de los fotones con los núcleos atómicos de diferentes materiales en un acelerador lineal para uso médico. En este trabajo, la energía cinética de fotoneutrones producidos por la interacción con los núcleos atómicos de 184 W, 63 Cu, 27 Al y 12 C, que son algunos de los materiales que constituyen el cabezal de un acelerador lineal médico, es calculada. Además, los núcleos presentes en los materiales de construcción de la sala y el laberinto del acelerador, como por ejemplo, 23Na, 40Ca y 28Si, como también en el cuerpo humano, ²H, 14N y 16O, son considerados. Se obtiene una expresión exacta teórica, la cual tiene una dependencia lineal de la energía de los neutrones producidos en relación a la energía del fotón incidente. Se ha encontrado que, en la mayoría de los casos, sólo los fotones con energías por encima de 10 MV contribuyen a la producción de neutrones. Los valores calculados a partir de la expresión obtenida en este trabajo están en buen acuerdo con los reportados en la literatura, los cuales se obtienen mediante otros métodos.

Superficial magnetic imaging by an xy-scanner of three magnetoresistive channels.

A scanning system developed for planar magnetic surfaces composed of a moving line of three magnetoresistive ultrasensitive transducers, complemented by a signal conditioning circuit is presented. After the calibration of the sensors, it was used to determine magnetized surface images with different shapes to evaluate the sensitivity of the device, and the images are represented in gray levels on a scale from 0 to 255 intensities, to get a visual representation of the magnetic field strength. The device is shown to be sensitive enough to detect gradients homogeneities and discontinuities in the magnetic field maps and images of magnetic susceptibility.

An induction heater device for studies of magnetic hyperthermia and specific absorption ratio measurements.

The development of a device for generating ac magnetic fields based on a resonant inverter is presented, which has been specially designed to carry out experiments of magnetic hyperthermia. By determining the electric current in the LC resonant circuit, a maximum intensity of magnetic field around of 15 mT is calculated, with a frequency around of 206 kHz. This ac magnetic field is able to heat powdered magnetic materials embedded in biological systems to be used in biomedical applications. Indeed, in order to evaluate the sensitivity of the device we also present the measurements of the specific absorption rate in phantoms performed with commercially prepared Fe(3)O(4) and distilled water at different concentrations.

Use of short-term bio-impedance for gastric motility assessment.

Gastric motility (GM) has been assessed using bio-impedance (BI) techniques in the time domain using short term recordings and analyzing mainly the median of the area under the fast Fourier transform (FFT) spectra. The BI technique has been applied to the gastric system mainly for gastric emptying (GE) studies. However, gastric motility evaluation using BI has not been fully implemented. In this study, we propose the use of the BI technique for the evaluation of gastric motility considering global features of the fast FFT spectra. The study was performed in eleven healthy subjects who were evaluated in fasting and postprandial conditions. The results indicate that the use of the median of the area under the FFT spectra is equivalent to the use of the main peak of the spectra to determine the changes in gastric motility from the fasting to the postprandial state. This demonstrates that BI is a valid technique for gastric motility evaluation in short time recordings.

Pulsed electromagnetic fields induced femoral metaphyseal bone thickness changes in the rat.

The effect of 1 Hz, 30 mT pulsed magnetic fields on young adult rat femoral metaphyseal bone thickness was assessed. Ten same litter, female Wistar rats were studied; five of them underwent 30 min magnetic stimulation sessions for 20 consecutive days. The anterior and posterior cortical, as well as trabecular bone transverse thicknesses were measured. The results obtained under clear field microscopy in stimulated and control histological cuts were (in microm) 398 +/- 32 versus 260 +/- 22 (P = 0.002), 380 +/- 68 versus 252 +/- 21 (P = 0.03), and 168 +/- 11 versus 112 +/- 11 (P = 0.002), respectively. The transcranial magnetic stimulation system, approved for human therapy, generates pulsed electromagnetic fields, which induce a significant thickness increase in cortical and trabecular in vivo stimulated bone tissues. This is the first time this effect in healthy animals is shown.

Magnetogastrography (MGG) reproducibility assessments of gastric emptying on healthy subjects.

The aim of this study was to evaluate the half-time gastric emptying reproducibility measured by magnetogastrography (MGG). Seven healthy subjects were subjected to a magnetic pulse of 32 mT for 17 ms, seven times in 90 min. The procedure was repeated one and two weeks later. Assessments of the gastric emptying were carried out for each one of the measurements and statistical analyses of ANOVA and Bland-Altman were performed for every group of data. A mean of 21.7 +/- 3.3 min was measured for the half-time of gastric emptying for yoghurt. Reproducibility estimation was above 85%. Therefore, magnetogastrography seems to be a reliable technique to be implemented in routine clinical trials.

Utilidad de los anticonceptivos con gestagenos solos en pacientes con antecedentes personales de cancer de mama. Influencia de los gestagenos en el desarrollo del cáncer de mama / Utility of the contraceptives with single gestagens in patients with personal antecedents of breast cancer. Influence of the gestagens in the development of the breast cancer

Los gestágenos clásicamente han sido relacionado con el cáncer mamario. Por esto, cuando se requiere indicar un anticonceptivos hormonal en una paciente tratada por cáncer de mama, surge la opción del uso de anticonceptivos con gestágenos solos (POP). Algunos estudios sugieren un rol protector de los gestágenos en el cáncer de mama: 1) La progesterona inhibe la proliferación mamaria inducida por el estradiol. 2) Induce apoptosis celular, inhibiendo la síntesis de las proteínas antiapoptóticas, 3) Inhibe enzimas que aumentan la concentración de estrógenos en la mama. Contrariamente, otras investigaciones muestran una acción favorecedora del cáncer de mama: 1) La actividad mitótica en las mamas es máxima durante la fase lútea, período en que predomina la progesterona. 2) En cultivos celulares los gestágenos estimulan la proliferación de algunas líneas celulares de cáncer de mama. 3) El uso de anticonceptivos orales con progestágenos y la medroxiprogesterona de depósito aumentan en mujeres jóvenes el riesgo de cáncer mamario. 4) En el reemplazo hormonal postmenopáusico varios estudios sugieren que la medroxiprogesterona incrementa el riesgo oncogénico. Conclusión: No existen datos que permitan afirmar con certeza que el uso de POP no tiene riesgos en pacientes con cáncer de mama.

In vivo measurement of human skin absorption of topically applied substances by a photoacoustic technique.

A photoacoustic technique is used for studying topically applied substance absorption in human skin. The proposed method utilizes a double-chamber PA cell. The absorption determination was obtained through the measurement of the thermal effusivity of the binary system substance-skin. The theoretical model assumes that the effective thermal effusivity of the binary system corresponds to that of a two-phase system. Experimental applications of the method employed different substances of topical application in different parts of the body of a volunteer. The method is demonstrated to be an easily used non-invasive technique for dermatology research. The relative concentrations as a function of time of substances such as ketoconazol and sunscreen were determined by fitting a sigmoidal function to the data, while an exponential function corresponds to the best fit for the set of data for nitrofurazona, vaseline and vaporub. The time constants associated with the rates of absorption, were found to vary in the range between 10 and 58 min, depending on the substance and the part of the body.

The effect of serum prolactin levels on ovarian steroidogenesis.

In order to assess the effect of hyperprolactinemia on ovarian steroidogenetic potential, a group of anovulatory hyperprolactinemic patients and a control group of anovulatory normoprolactinemic women were submitted to exogenous gonadotropin (hMG) stimulation under identical experimental conditions. Serum 17 beta-estradiol (E2) concentrations were determined before and after hMG stimulation. The mean basal serum E2 levels in the hyperprolactinemic group (22.7 +/- 3.3 pg/mL, mean +/- 1 SE) were significantly lower than in the normoprolactinemic control group (48.7 +/- 8.4 pg/mL, P less than .01). A significant negative correlation (r = -.6157, P less than .01) between basal serum E2 levels and basal serum prolactin (hPRL) concentrations was found. Following hMG stimulation, the serum E2 increment (delta E2) from basal E2 levels in the control group (491 +/- 91 pg/mL) was significantly higher than the increment in the hyperprolactinemic group (182 +/- 48 pg/mL, P less than .01), and a significant negative correlation was observed between basal serum hPRL levels and the logarithm of delta E2 (r = -.4744, P less than .05). Our results suggest that chronic hyperprolactinemia induces ovarian refractoriness to exogenous gonadotropin stimulation and substantially reduces its steroidogenetic potential.

Improved reliability of a serum alpha-fetoprotein enzyme immunoassay compared with a radioimmunoassay.

During the 6-month period between September 1982 and February 1983, serum samples were obtained from 850 pregnant women attending the municipal family clinics in Tel Aviv. All serum samples were tested by alpha-fetoprotein (AFP) enzyme immunoassay (EIA), and 650 samples were also tested by AFP radioimmunoassay (RIA). Comparisons were made between the absolute values, the medians, and the multiples of the median (MOM) obtained by each method. The ratios of the 90th percentile to the median and of the median to the 10th percentile were also compared. Inter- and intraassay variation were determined for both methods. Correlating the test results with the birth results showed that both methods detected the four fetuses with a neural tube defect (NTD) and three of nine twin pairs, when using a cutoff point of greater than or equal to 2.5 MOM. Elevated maternal serum AFP (MSAFP) levels were also noted in 32 normal singletons (3.8%). There were no false negative results during this phase of the study. Although the median values were similar for both methods, the mean of the ratios of the median to the 10th percentile and the 90th percentile to the median, showed a reduced spread for the EIA method.

The suppressive effect of delta-1-tetrahydrocannabinol on the steroidogenic activity of rat granulosa cells in culture.

In previous study the major psychoactive ingredient of marihuana (delta 1-THC) has been shown to inhibit ovarian prostaglandin synthesis when administered to normally cycling rats in the early afternoon of proestrus. These results suggested a direct suppressive effect of the drug on the ovary. The purpose of this study was to evaluate the effect of delta 1-THC on steroidogenesis in granulosa cells (GC) in vitro. Incubation of GC with delta 1-THC (10-50 microM) effectively inhibited LH-stimulatable progestin production. This suppressive effect was not abolished by washing the cells after 24 h of culture in the presence of delta 1-THC, indicating the irreversible nature of the blocking effect of delta 1-THC. By contrast, estradiol production following incubation of GC with testosterone (1 microgram/ml) was not inhibited by similar concentrations of delta 1-THC, thus suggesting that delta 1-THC does not inhibit aromatase activity in GC. In addition, delta 1-THC was shown to inhibit cAMP production as well as 125I-hCG binding capacity to GC. Administration of 8-Br-cAMP did not abolish the delta 1-THC-induced block, suggesting that the drug probably acts distal to the cAMP site of action.

Carcinoembryonic antigen in patients with colorectal cancer: correlation between stage of disease and antigen level.

Carcinoembryonic antigen (CEA) levels were measured by radio-immunoassay in the sera of 339 patients with various stages of colorectal cancer. Of 298 patients considered to be free of disease, 61 (20.5%) were found to have elevated CEA values of greater than 10 ng/ml. Of these patients, 36 had subsequent disease progression, 23 had only a transient rise in CEA and 2 showed a persistent increase with no clinical deterioration during the study period. Of 41 patients with known active disease, only 27 (65.9%) had elevated CEA values, most greater than 30 ng/ml, whereas the remaining 14 patients had CEA levels less than 10 ng/ml. Of a total of 77 patients with known active colorectal cancer throughout the whole study period, these 14 (18%) represent the number of false-negative CEA determinations. This relatively high rate of false-negative measurements should not obscure the fact that full accordance between CEA levels and clinical status as determined throughout 38 months of follow-up, occurred in 323 of the 339 patients.

In vitro effects of cannabinoids on follicular function in the rat.

delta 1-Tetrahydrocannabinol (delta 1-TCH), the major psychoactive constituent of marihuana, was found to suppress the preovulatory surge of gonadotropins and thereby to prevent ovulation in rats, rabbits and rhesus monkeys. These studies suggested that the drug acts primarily on the hypothalamus to suppress luteinizing hormone releasing hormone (LHRH) secretion. The aim of the present study was to examine the direct effect of delta 1-THC, the psychoactive constituent of marihuana and cannabidiol (CBD), one of its nonpsychoactive constituents, on preovulatory rat follicles in vitro. Both cannabinoids inhibited follicular steroidogenesis in a dose-dependent manner. Basal accumulation of progesterone (P), testosterone (T) and estradiol-17 beta (E2) was reduced up to 60% by the highest doses examined (100-200 microM). The luteinizing hormone (LH)-stimulated increase in P and T was inhibited by 75-88% by the highest doses of both cannabinoids (50-200 microM), while E2, accumulation was inhibited by only 40%. It appears that the inhibitory action of cannabinoids is exerted beyond LH binding and activation of adenylate cyclase and prior to pregnenolone formation in the gonadal steroidogenic pathway. In addition to this anti-steroidogenic effect, both cannabinoids induced resumption of meiosis in follicle-enclosed oocytes cultured in hormone-free medium; 200 microM delta 1-THC resulted in 80% maturation and CBD in 75%. It seems that the action of cannabinoids on rat follicles in vitro is unrelated to their psychotropic activity.