Selective activation of memristive interfaces in TaO x -based devices by controlling oxygen vacancies dynamics at the nanoscale.

The development of novel devices for neuromorphic computing and non-traditional logic operations largely relies on the fabrication of well controlled memristive systems with functionalities beyond standard bipolar behavior and digital ON-OFF states. In the present work we demonstrate for Ta2O5-based devices that it is possible to selectively activate/deactivate two series memristive interfaces in order to obtain clockwise or counter-clockwise multilevel squared remanent resistance loops, just by controlling both the electroforming process and the (a)symmetry of the applied stimuli, and independently of the nature of the used metallic electrodes. Based on our thorough characterization, analysis and modeling, we show that the physical origin of this electrical behavior relies on controlled oxygen vacancies electromigration between three different nanoscopic zones of the active Ta2O5-x layer: a central one and two quasi-symmetric interfaces with reduced TaO2-h(y) layers. Our devices fabrication process is rather simple as it implies the room temperature deposition of only one CMOS compatible oxide-Ta-oxide-and one metal, suggesting that it might be possible to take advantage of these properties at low cost and with easy scability. The tunable opposite remanent resistance loops circulations with multiple-analogic-intermediate stable states allows mimicking the adaptable synaptic weight of biological systems and presents potential for non-standard logic devices.

Effectiveness of a PMTCT programme in rural Western Kenya.

We assess the coverage of a Prevention of Mother-to-child Transmission (PMTCT) programme in Busia (Kenya) from 1 January 2006 to 31 December 2008 and estimate the risk of transmission of HIV. We also estimate the odds of HIV transmission according to pharmacological intervention received. Programme coverage was estimated as the proportion of mother-baby pairs receiving any antiretroviral (ARV) regimen among all HIV-positive women attending services. We estimated the mother-to-child transmission (MTCT) rate and their 95% confidence interval (95%CI) using the direct method of calculation (intermediate estimate). A case-control study was established among all children born to HIV-positive mothers with information on outcome (HIV status of the babies) and exposure (data on pharmacological intervention). Cases were all HIV-positive children and controls were the HIV-negative ones. Exposure was defined as: (1) complete protocol: ARV prescribed according World Health Organisation recommendations; (2) partial protocol: does not meet criteria for complete protocol; and (3) no intervention: ARVs were not prescribed to both mother and child. Babies were tested using DNA Polymerase Chain Reaction at six weeks of life and six weeks after breastfeeding ceased. In the study period, 22,566 women accepted testing, 1668 were HIV positive (7.4%; 95%CI 7.05-7.73); 1036 (62%) registered in the programme and 632 were lost. Programme coverage was 40.4% (95%CI 37.9-42.7). Out of the 767 newborns, 28 (3.6%) died, 148 (19.3%) defaulted, 282 (36.7%) were administratively censored and 309 (40.2%) babies completed the follow-up as per protocol; 49 were HIV positive and MTCT risk was 15.86% (95%CI 11.6-20.1). The odds of having an HIV-positive baby was 4.6 times higher among pairs receiving a partial protocol compared to those receiving a complete protocol and 43 times higher among those receiving no intervention. Our data show a good level of enrolment but low global coverage rate. It demonstrates that ARV regimens can be implemented in low resource rural settings with marked decreases of MTCT. Increasing the coverage of PMTCT programmes remains the main challenge.

Ionic liquids as solvents for Cerenkov counting and the effect of a wavelength shifter.

We study the wavelength shift of the Cerenkov light - generated in the ionic liquid (BMIMCl) - caused by the addition of the highly fluorescent ionic liquid (BMIMHPTS). 18F and 32P efficiencies increases up to 124% and 14%, respectively, compared with the values obtained with pure BMIMCl. With this improvement, ionic liquid mixtures become a good alternative - when using the TDCR-Cherenkov technique - to standardize radionuclides having electron emissions energies close to the threshold energy in water (∼ 260keV). As an advantage compared with other solvents, the Ionic liquid mixture can be reused, in the case of short-lived radionuclides, by simply removing all water content in a vacuum oven.

Analysis of multicomponent formulations containing phenylpropanolamine hydrochloride, caffeine and diazepam by using LC.

A reverse phase high performance liquid chromatography assay was carried out for the simultaneous determination of three active principles present in tablets of different origin and wide commercial use in the Province of Córdoba (Argentina). Prescriptions, commercially available as appetite suppressants, very often include the active principles Phenylpropanolamine Hydrochloride (I), Caffeine (II) and Diazepam (III). Simultaneous determination of these three drugs: anorexic, central nervous stimulant and tranquilizer, respectively, in pharmaceutical dosage forms has not been reported. In this study these active principles are quantified. The only sample preparation necessary for the analysis was their dilution with acetonitrile. The resulting solution was filtered and analyzed on a column packed with Supelcosil LC-18 (5 microm) with acetonitrile:water (30:70 v/v) as initial mobile phase (0.4 ml min(-1)) and the detection was performed at 254 nm. Then a linear gradient up to 100% acetonitrile in 18 min (3.0 ml min(-1)) was applied. The procedure was simple and suitable for quality control. The calibration function was established in the ranges of 0.072-0.168 mg ml(-1) for I, 0.036-0.084 mg ml(-1) for II and 0.06-0.196 mg ml(-1) for III. The detection limits of these compounds were 12.8, 4.1 and 11.0 microg ml(-1), respectively with linear response. No chromatographic interference from the tablet excipients was found. The method described in this paper was validated following the analytical performance parameters required by the USP XXIV, and was successfully applied to the commercial tablets.

Kinetic fluorimetric determination of the antineoplastic methotrexate (MTX) in human serum.

A kinetic study of the oxidation of methotrexate (MTX) in acidic medium and in the presence of potassium permanganate has been made on the basis of the fluorescence-time curves. A kinetic method for the determination of MTX was developed with a range of application between 0.22 and 3.30 microM. The proposed kinetic method permits us to determine MTX in human serum and to avoid the natural fluorescence of the serum. A detection limit of 0.18 microM was calculated in the presence of ascorbic acid as activator. Only 100 s per sample is necessary for the analysis. The interference of pteridin derivatives and the rescue agent folinic acid (leucovorin) was tested.

[Hemolytic activity of venoms from snakes of the genera Bothrop, Lachesis, Crotalus, and Micrurus (Serpentes: Viperidae and Elapidae]. / Actividad hemolítica de venenos de serpientes de los géneros Bothrops, Lachesis, Crotalus y Micrurus (Serpentes: Viperidae y Elapidae).

Hemolytic activity of eight Peruvian snake venoms from the families Viperidae and Elapidae (Bothrops atrox, B. pictus, B. hyoprorus, B. bilineatus, B. neuwedii, Lachesis m. muta, Crotalus d. terrificus, Micrurus tschudi), and three Brazilian viperids (B. jararacussu, B. alternatus and C. d. collilineatus) is described. None of the venoms caused direct lysis on washed human erythrocytes. However, all of them caused indirect hemolysis provided that the incubation medium contains an exogenous source of lecithin. Venom of Micrurus tschudi was the most hemolytic (HD50 2.8 ug/ml) while that of B. bilineatus was the least (HD50 681.3 ug/ml). Only six of eleven venoms showed parallel curves of hemolytic activity, and the HD50 varied from 198 to 681 ug/ml and the following decreasing order of hemolytic activity was obtained: L. muta, C. d. terrificus, C. d. collilineatus, B. hyoprorus, B. bilineatus, B. alternatus.

Evolution of left ventricular mass in renal transplant recipients: the influence of glucose homeostasis and oxidative stress.

BACKGROUND: Left ventricular hypertrophy, considered an independent factor for cardiovascular mortality, is frequent among renal transplant recipients (RTR), in whom we investigated changes in left ventricular mass (LVM) after grafting and associations with possible causal factors, especially glucose metabolism and oxidative stress. METHODS: We performed a prospective study of 37 RTR without prior diabetes mellitus who were evaluated at three times after transplantation (medians of 0.6, 16 and 28 months) by means of the LVM index (LVMI, echocardiographic measure of LVM related to body surface area, g/m(2)), oral glucose tolerance test and determinations of malondialdehyde and total glutathione (GSH), as well as glomerular filtration rate (GFR) estimate by the Modification of Diet in Renal Disease formula. We calculated the overall increment (DeltaLVMI) and percent change of LVMI. Patients were diagnosed to be prediabetic (PD) or new-onset diabetes after transplant (NODAT) according to ADA criteria. RESULTS: The mean LVMI decreased significantly over time among whole group baseline = 108.34 ± 27.71 g/m(2) versus middle: 100.03 ± 27.53 g/m(2) versus final: 90.62 ± 24.06 g/m(2) (P = .000). However, 13.5% of subjects showed an increased LVMI and 59.5%, a decrease less than 20%. Patients with NODAT at the end of the study showed a positive DeltaLVMI, which was negative in nondiabetics (0.24 ± 16.14 versus -19.86 ± 12.61 g/m(2), P = .018). Compared with DeltaLVMI(-) recipients, patients with DeltaLVMI(+) showed a greater proportion of PD and NODAT at baseline (60% and 40% versus 18.8% and 12.5%, P = .017), and significantly higher all-time fasting glycemia, lower estimated GFR, and greater increments of malondialdehyde and GSH over time. Those with a <20% LVMI decrease experienced progressive GFR impairment over time, as opposed to those with an LVMI decrease > 20%, who showed greater and improving GFR over the whole study. CONCLUSIONS: LVMI does not always improve in RTR; the evolution of ventricular mass after renal transplantation is influenced by glucose metabolism disorders, oxidative stress, and graft function.

Magnesemia in renal transplant recipients: relation with immunosuppression and posttransplant diabetes.

Hypomagnesemia, a frequent disorder in renal transplant patients related to the use of calcineurin inhibitors (CNIs), plays a causal role in insulin resistance and type 2 diabetes. Recently, hypomagnesemia has been identified as an independent predictor of new-onset diabetes after transplant (NODAT). The objective of this study was to investigate the influence of various immunosuppressive regimens on magnesemia in relation to the development of NODAT. We performed a retrospective study in 589 nondiabetic subjects who underwent serum magnesium measurements (mg/dL) on days 7 and 15 as well as at 1, 2, 3, 6, 9, and 12 months after transplantation. NODAT was diagnosed during the first year using American Diabetes Association criteria. The overall mean magnesemia was lower among CNI compared with non-CNI patients (1.73±0.25 vs 1.98±0.23; P=.000) and in patients on tacrolimus versus cyclosporine (1.72±0.24 vs 1.80±0.26; P=.007). It was higher in patients who received anti-CD25 antibodies with delayed CNI introduction (1.83±0.28 vs 1.71±0.23; P=.000). The use of CNIs and delayed CNI introduction were identified as independent factors related to magnesemia. No differences in magnesemia were observed among patients who developed NODAT versus the non-NODAT cohort. The incidence of NODAT was higher among patients on tacrolimus versus cyclosporine (26.8% vs 18.1%; P=.026), but no differences were found between the serum Mg tertiles at any time during the study or between mean magenesemia tertiles. In conclusion, despite the fact that CNI patients showed lower magnesemia and the group of tacrolimus, the lowest magnesemia and the highest incidence of NODAT, our study did not demonstrate a relationship between the Mg levels and the occurrence of NODAT. Patients treated with anti-CD25 antibodies and delayed CNI introduction maintained higher magnesemia during the first year after transplant.

Antiretroviral therapy for HIV prevention: many concerns and challenges, but are there ways forward in sub-Saharan Africa?

Scientists from the WHO have presented a theoretical mathematical model of the potential impact of universal voluntary HIV testing and counselling followed by immediate antiretroviral therapy (ART). The results of the model suggests that, in a generalised epidemic as severe as that in sub-Saharan Africa (SSA), HIV incidence may be reduced by 95% in 10 years and that this approach may be cost effective in the medium term. This offers a 'ray of hope' to those who have thus far only dreamed of curbing the HIV/AIDS epidemic in SSA, as until now the glaring truth has been pessimistic. When it comes to ART, approximately 7 of 10 people who clinically need ART still do not receive it. From an epidemic point of view, for every person placed on ART an estimated four to six others acquire HIV. The likelihood of achieving the targets of the Millennium Development Goals for 2015 and universal ART access by 2010 are thus extremely low. A new window of opportunity may have now opened, but there are many unanswered feasibility and acceptability issues. In this paper, we highlight four key operational challenges linked to acceptability and feasibility and discuss possible ways forward to address them.

Prediabetic States, subclinical atheromatosis, and oxidative stress in renal transplant patients.

Prediabetic states are common among renal transplant patients, portending increased cardiovascular risk with associated carotid atheromatosis. Oxidative stress (OS) induces lipid peroxidation, a key factor in the development of atheromatosis. The aim of this study was to investigate the influence of OS and impaired glucose homeostasis status on carotid atheromatosis in nondiabetic recipients. Thirty-seven nondiabetic renal transplant patients were studied at baseline (<3 months) and at 1 and 2 years posttransplantation by ultrasound measurement of carotid intima-media thickness (CIMT), standard oral glucose tolerance test, and determination of blood markers of lipid peroxidation (8-isoprostanes [8-ISOP] and malondialdehyde [MDA]). Prediabetic state (impaired fasting glucose, impaired glucose tolerance, and provisional diagnosis of diabetes [provDM] and new-onset diabetes after transplantation [NODAT]) was classified following American Diabetes Association (ADA) criteria. Total CIMT index (TCIMT) was calculated as the sum of right and left CIMT and DeltaTCIMT as the difference in TCIMT values at 2 years (end of study) minus baseline. At baseline and 1 year, TCIMT was significantly related to 8-ISOP (r = .611; P = .002) and to recipient age (r = .654; P = .000). At 2 years, DeltaTCIMT was significantly correlated with MDA (r = .635; P = .001) with significant differences in TCIMT observed between prediabetic states and diabetes (P = .001). Multiple regression analysis identified 8-ISOP and age as factors independently associated with TCIMT and MDA with DeltaTCIMT. These results suggested that lipid peroxidation in renal transplant recipients contributed to increases in CIMT, which was more pronounced among older and diabetic (provDM or NODAT) patients.

Effect of preconditioning with triiodothyronine on renal ischemia/reperfusion injury and poly(ADP-ribose) polymerase expression in rats.

The ischemia/reperfusion (I/R) model in rats allows pharmacological investigation of protective renal effects of certain agents to thereby diminish the incidence of delayed graft function (DGF). The aim of this study was to determine the effects of preconditioning with triiodothyronine (T(3)) on renal function and oxidative status in renal I/R injury. Forty male Wistar rats were preconditioned with T(3) (100 microg/kg) or control (normal saline) at 24 hours prior to 45 minutes of renal ischemia, followed by a 4-hour (groups C-4h and T(3)-4h) or 24-hour (groups C-24h and T(3)-24h) reperfusion period. We determined renal function parameters (urea, creatinine, and proteinuria), oxidative stress biomarkers in plasma (malondialdehyde [MDA], glutathione [GSH], and superoxide dismutase [SOD]), urine (hydrogen peroxide [H(2)O(2)]), and renal tissue (GSH and MDA), and poly(ADP-ribose) polymerase (PARP-1) expression. Proteinuria was significantly lower in the T(3)-treated group (4.63 +/- 1.9 vs 9.27 +/- 0.72 mg/mL/100 g body weight). Pretreated rats showed lower levels of plasma and tissue MDA and urine H(2)O(2) (50.57 +/- 1.17 vs 71.16 +/- 1.14 micromol/100 g body weight). The T(3) treatment was associated with lower postischemia GSH concentrations (3.82 +/- 1.16 vs 4.89 +/- 0.68 nmol/mg protein) and higher SOD levels at 24 hours (11.27 +/- 0.86 vs 9.92 +/- 1.77 nmol/mg protein). Preconditioning with the hormone also reduced PARP-1 tissue expression by 18% (P