Probing and controlling fluorescence blinking of single semiconductor nanoparticles

In this review we present an overview of the experimental and theoretical development on fluorescence intermittency (blinking) and the roles of electron transfer in semiconductor crystalline nanoparticles. Blinking is a very interesting phenomenon commonly observed in single molecule/particle experiments. Under continuous laser illumination, the fluorescence time trace of these single nanoparticles exhibit random light and dark periods. Since its first observation in the mid-1990s, this intriguing phenomenon has attracted wide attention among researchers from many disciplines. We will first present the historical background of the discovery and the observation of unusual inverse power-law dependence for the waiting time distributions of light and dark periods. Then, we will describe our theoretical modeling efforts to elucidate the causes for the power-law behavior, to probe the roles of electron transfer in blinking, and eventually to control blinking and to achieve complete suppression of the blinking, which is an annoying feature in many applications of quantum dots as light sources and fluorescence labels for biomedical imaging

Network geometry

Networks are finite metric spaces, with distances defined by the shortest paths between nodes. However, this is not the only form of network geometry: two others are the geometry of latent spaces underlying many networks and the effective geometry induced by dynamical processes in networks. These three approaches to network geometry are intimately related, and all three of them have been found to be exceptionally efficient in discovering fractality, scale invariance, self-similarity and other forms of fundamental symmetries in networks. Network geometry is also of great use in a variety of practical applications, from understanding how the brain works to routing in the Internet. We review the most important theoretical and practical developments dealing with these approaches to network geometry and offer perspectives on future research directions and challenges in this frontier in the study of complexity

Vertical transmission of HIV-1: Maternal immune status and obstetric factors

Objective: To estimate the effect of maternal factors and events around the time of delivery on HIV-1 vertical transmission risk. Design: Prospective study. Setting: Twenty-two obstetric and paediatric clinics in seven European countries. Patients or other participants: Mothers identified as HIV-infected before or at delivery and their children. Main outcome measure: Paediatric HIV infection. Results: By November 1995, 1846 mothers with 1945 children had been enrolled. The vertical transmission rate was 16.4% (95% confidence interval, 14.5-18.3). Parity, maternal age, race, mode of HIV acquisition, injecting drug use and sex of infant were not statistically significantly associated with risk of transmission, Children delivered vaginally were more likely to be infected than those delivered by Caesarean section. However, in vaginal deliveries the procedures used, duration of ruptured membranes or length of second-stage labour were not related to transmission. Transmission increased almost linearly with decreasing CD4 cell count, but there was no such trend for CD8 cell count. Women with CD4 cell counts below 200 x 10(6)/l were significantly more likely to deliver early (chi(2) for trend, 14.02; P < 0.001). Very premature infants were at increased risk of infection, but after about 35 weeks gestation the transmission rate remained stable, with no increase in late pregnancy. This trend was confirmed after allowing for maternal CD4 cell count. Conclusions: The rate of vertical transmission increases linearly with decreasing maternal CD4 cell count. Women with fewer than 200 x 10(6) CD4 cells/l have an increased risk of premature delivery, which would affect timing of interventions. The stable transmission rate after 35 weeks gestation suggests little acquisition of infection during late pregnancy

Therapeutic and other interventions to reduce the risk of mother-to-child transmission of HIV-1 in Europe. The European Collaborative Study

C. Thorne, M.-L. Newell, A. Bailey, C.S. Peckham, C. Giaquinto, E. Ruga, A. De Rossi, D. Truscia, I. Grosch-Worner, A. Schafer, J. Mok, F. Johnstone, F. Omenaca, J. Jiminez, C.De Alba, M.C. Garcia-Rodriguez, I. Bates, I. De Jose, F. Hawkins, R. Martinez Zapico, F. Asensi-Botet, M.C. Otero, D. Perez-Tamarit, A. Gonzalez Molina, H. Canosa, H. Scherpbier, K. Boer, A.B. Bohlin, S. Lindgren, E. Belfrage, J. Levy, A. Alimenti, P. Barlow, A. Ferrazin, A. Dre Maria, C. Gotta, V. Maritati, A. Mur, M.T. Rovira, A. Paya, O. Coll, C. Fortuny, J. Boguna, M. Casellas Caro, Y. Canet, G. Pardi, A.E. Semprini, M. Ravizza, C. Castagna, S. Fiore, B. Guerra, S. Bianchi, L. Bovicelli, E. Prati, S. Zanelli, M. Duse, A. Soresina, G. Scaravelli, M. Stegagno, M. De Santis, M.-L. Muggiasca, P. Marchisio, A. Iasci, A. Spinillo, A. Bucceri, E. Grossi, L. Rancilio, R. Smith, A.-M. Lewi

Exposure to antiretroviral therapy in utero or early life: the health of uninfected children born to HIV-infected women

Concerns have been raised over possible adverse effects of prophylactic antiretroviral therapy (ART) on the fetus and newborn. We analyzed data relating to uninfected children enrolled in the European Collaborative Study and investigated the association between ART exposure, perinatal problems, and major adverse health events later in life. Median length of follow-up was 2.2 (0-15.9) years. Of the 2414 uninfected children, 687 (28%) were exposed to ART in all three periods (antenatal, intrapartum, and neonatal). Of the 1008 infants exposed to ART at any time, 906 (90%) were exposed antenatally, 840 (83%) neonatally, and 750 (74%) both antenatally and neonatally. ART exposure was not significantly associated with pattern or prevalence of congenital abnormalities or low birth weight. In multivariate analysis, prematurity was associated with exposure to combination therapy without a protease inhibitor (PI) (OR = 2.66; 95% CI: 1.52-4.67) and with a PI (OR = 4.14; 95% CI: 2.36-7.23). ART exposure was associated with anemia in early life (P < .001). There was no evidence of an association with clinical manifestations suggestive of mitochondrial abnormalities. The absence of serious adverse events in this large cohort of uninfected children exposed to prophylactic ART in the short to medium term is reassuring

Increasing likelihood of further live births in HIV-infected women in recent years

Objective To examine how the subsequent childbearing of HIV-infected mothers enrolled in the European Collaborative Study (ECS) has changed over time and identify factors predictive of further childbearing. Design Prospective cohort study. Setting Centres in nine European countries included in the ECS, enrolled between end 1986 and November 2003. Population HIV-infected women (3911): 3693 with only one and 218 with subsequent live births. Methods Univariable and multivariable logistic regression analyses to obtain odds ratios (OR) and 95% confidence intervals (CI). Kaplan-Meier (KM) analyses to estimate cumulative proportions of women having a subsequent live birth. Main outcome measures Subsequent live birth. Results In multivariable analysis adjusting for time period, ethnicity, maternal age and parity, black women were more likely [adjusted odds ratio (AOR) 2.45; 95% CI, 1.75-3.43], and women > 30 years less likely (AOR 0.54, 0.37-0.80), to have a subsequent live birth. Time to subsequent live birth significantly shortened over time, with an estimated 2% of women having a subsequent live birth within 24 months of enrolment pre-1989 versus 14% in 2000-2003 (P < 0.001). Estimated time to subsequent live birth was shorter for black than for white women (P < 0.001). Conclusions The likelihood of subsequent live births substantially increased after 1995 and birth intervals were shorter in women on HAART and among black women. Numbers are currently too small to address the issue of advantages and disadvantages in the management of subsequent deliverie