35 research outputs found

    The relationship between legal pluralism and the rule of law in South Africa and Timor-Leste

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    The re/establishment of the ‘rule of law’ in transitional countries has become a mantra of the international community. At its core, the rule of law assumes that the state enjoys a monopoly of law. This thesis argues that the promotion of the rule of law in transitional countries gives insufficient attention to whether a strong level of legal pluralism exists, in that forms of non-state law, such as customary law, operate in parallel with state law and are preferred by a large proportion of the population. A strong level of legal pluralism is the norm in many regions of the world, particularly in Africa, Asia and the Pacific, where between 80 to 90 per cent of disputes are taken to non-state legal mechanisms for resolution. This study examines two transitional countries, South Africa and Timor-Leste, which are attempting to re/establish the rule of law and where legal pluralism is strong. ..

    Optomechanical Design and Analysis for Nanosatellite Laser Communications

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    The CubeSat Laser Infrared CrosslinK (CLICK) mission is a technology demonstration of a 1.5U laser communications terminal for an intersatellite link. The terminal is deployed on a pair of 3U CubeSats in Low Earth Orbit (LEO). The pointing, acquisition, and tracking (PAT) approach includes both coarse and fine systems. The coarse tracking system uses a beacon laser transmitter and receiver camera. The fine tracking system uses a fast steering mirror and quadrant photodiode. The communications transmit and receive paths include a refractive telescope, transmit laser collimator, and avalanche photodetector (APD) receiver. The communications laser full-width, half maximum (FWHM) beam divergence angle is 14.6 arcseconds, and the beacon laser FWHM divergence is 0:75° (2700 arcseconds). The opto-mechanical design process includes prediction & verification of assembly alignment & calibration, thermoelastic effects, structural modes & static loading, and fastener analysis. The opto-mechanical assembly has the sensors and laser transmitters kinematically mounted to enable on-ground calibration to less than 25.4 mm decenter, or 0.1° tip/tilt. The thermoelastic alignment error between the payload and bus star tracker is estimated via finite element analysis to be less than 9 arcseconds. The payload optical bench is designed with custom thermal isolation and control to maintain 20 ± 10 ° C. The thermal modeling of the payload is described in detail. Structural static loading and fastener analyses of the CLICK payload under launch loads of 30 G verify margins of safety are greater than 10 and above the recommended values. Modal analyses predict the first resonant frequency to be 888 Hz, above typical vehicle structural vibration ranges with a factor of safety greater than 3.5

    Cryptic Population Dynamics: Rapid Evolution Masks Trophic Interactions

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    Trophic relationships, such as those between predator and prey or between pathogen and host, are key interactions linking species in ecological food webs. The structure of these links and their strengths have major consequences for the dynamics and stability of food webs. The existence and strength of particular trophic links has often been assessed using observational data on changes in species abundance through time. Here we show that very strong links can be completely missed by these kinds of analyses when changes in population abundance are accompanied by contemporaneous rapid evolution in the prey or host species. Experimental observations, in rotifer-alga and phage-bacteria chemostats, show that the predator or pathogen can exhibit large-amplitude cycles while the abundance of the prey or host remains essentially constant. We know that the species are tightly linked in these experimental microcosms, but without this knowledge, we would infer from observed patterns in abundance that the species are weakly or not at all linked. Mathematical modeling shows that this kind of cryptic dynamics occurs when there is rapid prey or host evolution for traits conferring defense against attack, and the cost of defense (in terms of tradeoffs with other fitness components) is low. Several predictions of the theory that we developed to explain the rotifer-alga experiments are confirmed in the phage-bacteria experiments, where bacterial evolution could be tracked. Modeling suggests that rapid evolution may also confound experimental approaches to measuring interaction strength, but it identifies certain experimental designs as being more robust against potential confounding by rapid evolution

    Cryptic Population Dynamics: Rapid Evolution Masks Trophic Interactions

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    Trophic relationships, such as those between predator and prey or between pathogen and host, are key interactions linking species in ecological food webs. The structure of these links and their strengths have major consequences for the dynamics and stability of food webs. The existence and strength of particular trophic links has often been assessed using observational data on changes in species abundance through time. Here we show that very strong links can be completely missed by these kinds of analyses when changes in population abundance are accompanied by contemporaneous rapid evolution in the prey or host species. Experimental observations, in rotifer-alga and phage-bacteria chemostats, show that the predator or pathogen can exhibit large-amplitude cycles while the abundance of the prey or host remains essentially constant. We know that the species are tightly linked in these experimental microcosms, but without this knowledge, we would infer from observed patterns in abundance that the species are weakly or not at all linked. Mathematical modeling shows that this kind of cryptic dynamics occurs when there is rapid prey or host evolution for traits conferring defense against attack, and the cost of defense (in terms of tradeoffs with other fitness components) is low. Several predictions of the theory that we developed to explain the rotifer-alga experiments are confirmed in the phage-bacteria experiments, where bacterial evolution could be tracked. Modeling suggests that rapid evolution may also confound experimental approaches to measuring interaction strength, but it identifies certain experimental designs as being more robust against potential confounding by rapid evolution

    Within-Host Dynamics of the Hepatitis C Virus Quasispecies Population in HIV-1/HCV Coinfected Patients

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    HIV/HCV coinfected individuals under highly active antiretroviral therapy (HAART) represent an interesting model for the investigation of the role played by the immune system in driving the evolution of the HCV quasispecies. We prospectively studied the intra-host evolution of the HCV heterogeneity in 8 coinfected subjects, selected from a cohort of 32 patients initiating HAART: 5 immunological responders (group A) and 3 immunological non-responders (group B), and in two HCV singly infected controls not assuming drugs (group C). For all these subjects at least two serial samples obtained at the first observation (before HAART) and more than 1 year later, underwent clonal sequence analysis of partial E1/E2 sequences, encompassing the whole HVR1. Evolutionary rates, dated phylogenies and population dynamics were co-estimated by using a Bayesian Markov Chain Monte Carlo approach, and site specific selection pressures were estimated by maximum likelihood-based methods. The intra-host evolutionary rates of HCV quasispecies was 10 times higher in subjects treated with HAART than in controls without immunodeficiency (1.9 and 2.3×10−3 sub/site/month in group A and B and 0.29×10−3 sub/site/month in group C individuals). The within-host Bayesian Skyline plot analysis showed an exponential growth of the quasispecies populations in immunological responders, coinciding with a peak in CD4 cell counts. On the contrary, quasispecies population remained constant in group B and in group C controls. A significant positive selection pressure was detected in a half of the patients under HAART and in none of the group C controls. Several sites under significant positive selection were described, mainly included in the HVR1. Our data indicate that different forces, in addition to the selection pressure, drive an exceptionally fast evolution of HCV during HAART immune restoration. We hypothesize that an important role is played by the enlargement of the viral replicative space

    The COVID-19 pandemic: a letter to G20 leaders

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    Complement lectin pathway activation is associated with COVID-19 disease severity, independent of MBL2 genotype subgroups

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    IntroductionWhile complement is a contributor to disease severity in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections, all three complement pathways might be activated by the virus. Lectin pathway activation occurs through different pattern recognition molecules, including mannan binding lectin (MBL), a protein shown to interact with SARS-CoV-2 proteins. However, the exact role of lectin pathway activation and its key pattern recognition molecule MBL in COVID-19 is still not fully understood.MethodsWe therefore investigated activation of the lectin pathway in two independent cohorts of SARS-CoV-2 infected patients, while also analysing MBL protein levels and potential effects of the six major single nucleotide polymorphisms (SNPs) found in the MBL2 gene on COVID-19 severity and outcome.ResultsWe show that the lectin pathway is activated in acute COVID-19, indicated by the correlation between complement activation product levels of the MASP-1/C1-INH complex (p=0.0011) and C4d (p<0.0001) and COVID-19 severity. Despite this, genetic variations in MBL2 are not associated with susceptibility to SARS-CoV-2 infection or disease outcomes such as mortality and the development of Long COVID.ConclusionIn conclusion, activation of the MBL-LP only plays a minor role in COVID-19 pathogenesis, since no clinically meaningful, consistent associations with disease outcomes were noted
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