``Plug and play'' systems for quantum cryptography

We present a time-multiplexed interferometer based on Faraday mirrors, and apply it to quantum key distribution. The interfering pulses follow exactly the same spatial path, ensuring very high stability and self balancing. Use of Faraday mirrors compensates automatically any birefringence effects and polarization dependent losses in the transmitting fiber. First experimental results show a fringe visibility of 0.9984 for a 23km-long interferometer, based on installed telecom fibers.Comment: LaTex, 6 pages, with 2 Postscript figures, Submitted to Applied Physics Letter

Phase conversion in a weakly first-order quark-hadron transition

We investigate the process of phase conversion in a thermally-driven {\it weakly} first-order quark-hadron transition. This scenario is physically appealing even if the nature of this transition in equilibrium proves to be a smooth crossover for vanishing baryonic chemical potential. We construct an effective potential by combining the equation of state obtained within Lattice QCD for the partonic sector with that of a gas of resonances in the hadronic phase, and present numerical results on bubble profiles, nucleation rates and time evolution, including the effects from reheating on the dynamics for different expansion scenarios. Our findings confirm the standard picture of a cosmological first-order transition, in which the process of phase conversion is entirely dominated by nucleation, also in the case of a weakly first-order transition. On the other hand, we show that, even for expansion rates much lower than those expected in high-energy heavy ion collisions, nucleation is very unlikely, indicating that the main mechanism of phase conversion is spinodal decomposition. Our results are compared to those obtained for a strongly first-order transition, as the one provided by the MIT bag model.Comment: 12 pages, 10 figures; v2: 1 reference added, minor modifications, matches published versio

Ecological impacts of small dams on South African rivers Part 2: Biotic response – abundance and composition of macroinvertebrate communities

This paper investigates the cumulative impacts of small dams on invertebrate communities in 2 regions of South Africa – the Western Cape and Mpumalanga. Previous research found reduced discharge, increased total dissolved salts, and a decrease in average score per taxon (ASPT; collected using SASS4 methods) at sites with high density of small dams in their catchment. These changes in ASPT are investigated using the invertebrate abundance data available in the River Health Programme. Multivariate analyses found differences in invertebrate communities in rivers with high densities of small dams in their catchment in foothill-gravel streams (in both Western Cape and Mpumalanga) and in foothill-cobble streams (in Western Cape only). Opportunistic taxa that are tolerant of pollution, and capable of exploiting various habitats, and those that prefer slower currents increased in numbers, while other taxa that are sensitive to pollution and disturbance declined in numbers. Some regional differences were noted possibly reflecting climatic differences between the regions. Since the results of this study are correlative, it highlights the need for a systematic (by sites and seasons) and detailed (at species level) collection of data to verify the results of cumulative effects of small dams. This can further the development of a framework for small-dam construction and management that will limit their impact on river catchments

Tracking system analytic calibration activities for the Mariner Mars 1969 mission

Calibration activity of Deep Space Network in support of Mars encounter phase of Mariner Mars 1969 missio

HIV-associated nephropathy - an initial presentation in an HIV-positive patient

The lesions of HIV-associated nephropathy occur in patients with AIDS, AIDS-related complex and in individuals clinically asymptomatic for HIV infection. We report on a 35-year-old black South African Woman who presented with nephrotic syndrome and renal failure. The renal biopsy appearance suggested mv infection and this was subsequently verified. This finding emphasises the possibility that otherwise asymptomatic patients presenting with renal disease may be HIV-positive

Metallicity and Physical Conditions in the Magellanic Bridge

We present a new analysis of the diffuse gas in the Magellanic Bridge (RA>3h) based on HST/STIS E140M and FUSE spectra of 2 early-type stars lying within the Bridge and a QSO behind it. We derive the column densities of HI (from Ly\alpha), NI, OI, ArI, SiII, SII, and FeII of the gas in the Bridge. Using the atomic species, we determine the first gas-phase metallicity of the Magellanic Bridge, [Z/H]=-1.02+/-0.07 toward one sightline, and -1.7<[Z/H]<-0.9 toward the other one, a factor 2 or more smaller than the present-day SMC metallicity. Using the metallicity and N(HI), we show that the Bridge gas along our three lines of sight is ~70-90% ionized, despite high HI columns, logN(HI)=19.6-20.1. Possible sources for the ongoing ionization are certainly the hot stars within the Bridge, hot gas (revealed by OVI absorption), and leaking photons from the SMC and LMC. From the analysis of CII*, we deduce that the overall density of the Bridge must be low (<0.03-0.1 cm^-3). We argue that our findings combined with other recent observational results should motivate new models of the evolution of the SMC-LMC-Galaxy system.Comment: Accepted for publication in the Ap

Sexual Coercion by Male Chimpanzees Shows That Female Choice May Be More Apparent than Real

The extent to which active female mating preferences influence male reproductive success in mammals is unclear, particularly for promiscuously breeding species like chimpanzees (Pan troglodytes). Previous studies from multiple long-term study sites have shown that female chimpanzees mate more restrictively around ovulation, and this has been taken as evidence for female choice. However, none of these studies rigorously evaluated the alternative hypothesis that restrictive mating results not from unconstrained choice, but in response to coercive mate guarding, in which males use punishment and intimidation to reduce female promiscuity and promote their own mating interests. Nor did they consider evidence for the potential genetic or phenotypic benefits that females might be choosing. Using 11 years of data from the Kanyawara community in Kibale National Park, Uganda, we previously demonstrated that males achieve elevated mating success with those females toward whom they direct high levels of aggression. Here we extend those findings to show that even female copulatory approaches, which have previously been attributed to female choice, are correlated with male aggression. Specifically, individual females at our site initiated periovulatory copulations most frequently with the males who were most aggressive toward them throughout their cycles. Those males showed high rates of aggression toward females throughout estrus, despite achieving high copulation rates, demonstrating a continuing conflict of interest over the exclusivity of mating access. Because sexual coercion is potentially widespread in primates and other mammals, our results stress the importance of considering the influence of male aggression in studies of female choice.Human Evolutionary Biolog