Pbte Quantum Dots - Sio2 Multilayers For Optical Devices Produced By Laser Ablation

Thin films of glass doped with PbTe quantum dots were successfully fabricated. The semiconducting quantum dots were grown by laser ablation of a PbTe target (99.99%) using the second harmonic of a Q-Switched Quantel Nd:YAG laser under high purity argon atmosphere. The glass matrix was fabricated by a plasma chemical vapor deposition method using vapor of tetramethoxysilane (TMOS) as precursor. The QD's and the glass matrix were alternately deposited onto a Si (100) wafer for 60 cycles. Cross-section TEM image clearly showed QD's layer well separated from each other with glass matrix layers. The influence of the ablation time on the size distribution of the quantum dots is studied. HRTEM revealed anisotropy in the size of the QD's: they were about 9nm in the high and 3-5 in diameter. Furthermore HRTEM studies revealed that the QD's basically growth in the (200) and (220) directions. The thickness of the glass matrix layer was about 20 nm. Absorption, photo luminescence and relaxation time of the multilayer were also measured.5734116123Alivisatos, A.P., (1996) Sci., 271, p. 933Warnock, J., Awschalom, D.D., (1985) Phys. Rev. B, 32, p. 5529Borrelli, N.F., May, D.W., Holland, H.J., Smith, D.W., (1987) J. Appl. Phys., 61, p. 399Potter, B.G., Simmons, J.H., (1988) Phys. Rev. B, 37, p. 10838Gleiter, H., (1989) Prog. Mater. Sci., 33, p. 223Tsunetomo, K., Shunsuke, S., Koyama, T., Tanaka, S., Sasaki, F., Kobayashi, S., (1995) Nonlinear Opt., 13, p. 109Reynoso, V.C.S., De Paula, A.M., Cuevas, R.F., Neto, J.A.M., Alves, O.L., Cesar, C.L., Barbosa, L.C., (1995) Electr. Lett., 31 (12), pp. 1013-1015Jacob, G.J., Cesar, C.L., Barbosa, L.C., (2002) Chem. Phys. Glass, 43 C, pp. 250-252Singh, R.K., Narayan, J., (1990) Phys. Rev. B, 41, p. 8843Barnes, J.P., (2002) Nanotechnology, 13, p. 465Tudury, G.E., Marquezini, M.V., Ferreira, L.G., Barbosa, L.C., Cesar, C.L., (2000) Phys. Rev. B, 62 (11), pp. 7357-7364Cesar, C.L., Jacob, G.J., Tudury, G.E., Marquezini, M.V., Barbosa, L.C., (2004) Atti della Fondazione G. Ronchi Journal, (4), pp. 519-528. , Anno LI

Phytoplankton productivity in the Barra de Navidad coastal lagoon on the Pacific coast of Mexico

La production du phytoplancton a été mesurée dans la lagune Barra de Navidad, Jalisco, Mexique, d'octobre 1983 à septembre 1984. La production nette au cours de la journée était de 772 g O2m-2an-1 et la production brute 1036 gO2m-2an-1. Dans le temps, la productivité a varié en fonction de variations saisonnières bien marquées de la transparence, de la température, de la salinité et des apports par les rivières. Les plus fortes productivités ont été observées en saison des pluies (juin à octobre). Dans l'espace, les plus fortes valeurs ont eu lieu dans la zone centrale, avec une diminution vers l'embouchure de la rivière et la communication avec l'océan. D'une façon générale, les productivités élevées résultent de concentrations en nutriments et de transparence plus favorables dans la zone centrale. La productivité diminue avec la diminution des apports continentaux durant la saison sèche, mais également avec la forte turbidité liée à la crue de la rivière. (Résumé d'auteur

Small-scale gold mining and the COVID-19 pandemic: Conflict and cooperation in the Brazilian Amazon

The COVID-19 pandemic exposes both conflict and cooperation in artisanal and small-scale gold mining in the Brazilian Amazon. Reporting on the experiences of artisanal and small-scale gold miners (garimpeiros, in Brazilian Portuguese), we show how, on the one hand, the pandemic challenges an already precarious working system that could lead garimpeiros, often invisible to public policies, to positions of further vulnerability; and, on the other hand, highlights the capacity of garimpeiros to self-organize and navigate the difficulties by finding alternative solutions to cope with the crisis. This leads us to argue that emerging strategies of cooperation, related to self-organization and communication channels have the potential to provide experiences useful for processes of conflict transformation in the post-crisis. We acknowledge that much depends on the severity of the crisis and its manifestations in the region; nevertheless, the potential for constructive outcomes from the crisis should not be disregarded

Parasitism in Kansas in the 1800s - A glimpse to the past through the analysis of grave sediments from Meadowlark cemetery.

International audienceDuring the excavations of the XIX century Meadowlark cemetery (Manhattan, Kansas, US), samples of sediments were taken from around five skeletons, and analyzed to detect intestinal parasites. No helminth eggs were found, but immunological ELISA tests for Entamoeba histolytica were positive in three samples. The immunological techniques have been successfully used in paleoparasitology to detect protozoan infections. Amoebiasis could have been a severe disease in the past, especially where poor sanitary conditions prevailed, and there is evidence that this cemetery may have been used in a situation where poor sanitary conditions may have prevailed. The presence of this protozoan in US during the late XIX century gives information on the health of the population and provides additional data on the parasite's evolution since its appearance in the New World

The use of metamaterial technology to improve a GTEM chamber

In this work, metamaterial patterns are applied to a\ud GTEM – Gigahertz Transverse Electromagnetic Chamber to\ud improve and give flexibility to its frequency response. The main\ud goal is to achieve a better frequency resonance regardless the\ud dimensions of the original chamber. Therefore, a comparison\ud between the CLL – Capacitively Loaded Loop and Fractal\ud metamaterial technology for these purposes, is done.\ud Experimental results are compared to the simulated one

[vasopressin Intravenous Infusion Causes Dose Dependent Adverse Cardiovascular Effects In Anesthetized Dogs].

BACKGROUND: Arginine vasopressin (AVP) has been broadly used in the management of vasodilatory shock. However, there are many concerns regarding its clinical use, especially in high doses, as it can be associated with adverse cardiovascular events. OBJECTIVE: To investigate the cardiovascular effects of AVP in continuous IV infusion on hemodynamic parameters in dogs. METHODS: Sixteen healthy mongrel dogs, anesthetized with pentobarbital were intravascularly catheterized, and randomly assigned to: control (saline-placebo; n=8) and AVP (n=8) groups. The study group was infused with AVP for three consecutive 10-minute periods at logarithmically increasing doses (0.01; 0.1 and 1.0 U/kg/min), at them 20-min intervals. Heart rate (HR) and intravascular pressures were continuously recorded. Cardiac output was measured by the thermodilution method. RESULTS: No significant hemodynamic effects were observed during 0.01 U/kg/min of AVP infusion, but at higher doses (0.1 and 1.0 U/kg/min) a progressive increase in mean arterial pressure (MAP) and systemic vascular resistance index (SVRI) were observed, with a significant decrease in HR and the cardiac index (CI). A significant increase in the pulmonary vascular resistance index (PVRI) was also observed with the 1.0 U/kg/min dose, mainly due to the decrease in the CI. CONCLUSION: AVP, when administered at doses between 0.1 and 1.0 U/kg/min, induced significant increases in MAP and SVRI, with negative inotropic and chronotropic effects in healthy animals. Although these doses are ten to thousand times greater than those routinely used for the management of vasodilatory shock, our data confirm that AVP might be used carefully and under strict hemodynamic monitoring in clinical practice, especially if doses higher than 0.01 U/kg/min are needed.942213218, 229-234, 216-22

Kinin B1 receptor controls maternal adiponectin levels and influences offspring weight gain

Given the importance of the kinin B1 receptor in insulin and leptin hormonal regulation, which in turn is crucial in maternal adaptations to ensure nutrient supply to the fetus, we investigated the role of this receptor in maternal metabolism and fetoplacental development. Wild-type and kinin B1 receptor-deficient (B1KO) female mice were mated with male mice of the opposite genotype. Consequently, the entire litter was heterozygous for kinin B1 receptor, ensuring that there would be no influence of offspring genotype on the maternal phenotype. Maternal kinin B1 receptor blockade reduces adiponectin secretion by adipose tissue ex vivo, consistent with lower adiponectin levels in pregnant B1KO mice. Furthermore, fasting insulinemia also increased, which was associated with placental insulin resistance, reduced placental glycogen accumulation, and heavier offspring. Therefore, we propose the combination of chronic hyperinsulinemia and reduced adiponectin secretion in B1KO female mice create a maternal obesogenic environment that results in heavier pups