Viral Reservoirs in Lymph Nodes of FIV-Infected Progressor and Long-Term Non-Progressor Cats during the Asymptomatic Phase.

BackgroundExamination of a cohort of cats experimentally infected with feline immunodeficiency virus (FIV) for 5.75 years revealed detectable proviral DNA in peripheral blood mononuclear cells (PBMCs) harvested during the asymptomatic phase, undetectable plasma viral RNA (FIV gag), and rarely detectable cell-associated viral RNA. Despite apparent viral latency in peripheral CD4+ T cells, circulating CD4+ T cell numbers progressively declined in progressor animals. The aim of this study was to explore this dichotomy of peripheral blood viral latency in the face of progressive immunopathology. The viral replication status, cellular immunophenotypes, and histopathologic features were compared between popliteal lymph nodes (PLNs) and peripheral blood. Also, we identified and further characterized one of the FIV-infected cats identified as a long-term non-progressor (LTNP).ResultsPLN-derived leukocytes from FIV-infected cats during the chronic asymptomatic phase demonstrated active viral gag transcription and FIV protein translation as determined by real-time RT-PCR, Western blot and in situ immunohistochemistry, whereas viral RNA in blood leukocytes was either undetectable or intermittently detectable and viral protein was not detected. Active transcription of viral RNA was detectable in PLN-derived CD4+ and CD21+ leukocytes. Replication competent provirus was reactivated ex vivo from PLN-derived leukocytes from three of four FIV-infected cats. Progressor cats showed a persistent and dramatically decreased proportion and absolute count of CD4+ T cells in blood, and a decreased proportion of CD4+ T cells in PLNs. A single long-term non-progressor (LTNP) cat persistently demonstrated an absolute peripheral blood CD4+ T cell count indistinguishable from uninfected animals, a lower proviral load in unfractionated blood and PLN leukocytes, and very low amounts of viral RNA in the PLN.ConclusionCollectively our data indicates that PLNs harbor important reservoirs of ongoing viral replication during the asymptomatic phase of infection, in spite of undetectable viral activity in peripheral blood. A thorough understanding of tissue-based lentiviral reservoirs is fundamental to medical interventions to eliminate virus or prolong the asymptomatic phase of FIV infection

Community Engagement in Cultural Heritage A Digital Context

A series of case studies outlining the application of virtual reality and digital technologies for cultural heritage is presented in this article with an aim to examine the role for community engagement and SMEs in cultural heritage within a digital context. Digital technologies can be a repository and tool for telling local stories in relation to place and time on site and virtually off-site. In a series of case studies, tools and technologies for virtual reality experiences are outlined to identify the appropriate tools which can best facilitate this community engagement. In addition, community-based digital heritage initiatives will be discussed with reference to the Faro Convention. These technologies include applying BIM or GIS for historic structures involves initially data capture of the geometry and texture using laser scanning or digital photogrammetry, and then converting the digital survey data to solid Building Information Models (BIM). The process is described as Historic BIM or Historic GIS and, in this paper, several virtual reconstruction case studies of Irish Megalithic and Romanesque structures are presented

Combining low-temperature gettering with phosphorus diffusion gettering for improved multicrystalline silicon

We have investigated low-temperature (≤500 °C) gettering in combination with phosphorus diffusion gettering with a view to improving poor quality multicrystalline silicon. Low-temperature gettering applied after standard phosphorus diffusion gettering is found to provide a >40% improvement in minority carrier lifetime in samples from the top and bottom of an ingot. The best results are achieved at 300 °C with very long annealing times (>24 h). Improvements in the lifetime do not correlate with changes in interstitial iron concentration. Experiments are performed to assess whether the presence of a phosphorus-diffused emitter affects low-temperature gettering, and results from sister samples show the low-temperature gettering behavior is not affected by the existence of an emitter. Further experiments show that low-temperature gettering prior to phosphorus diffusion results in a 20% higher lifetime after phosphorus diffusion. Low-temperature gettering can, therefore, enhance lifetime even when used in conjunction with standard phosphorus diffusion gettering

Hydrogenation effect on low temperature internal gettering in multicrystalline silicon

We have performed a comprehensive study into low temperature ( 500 °C) internal gettering in multicrystalline silicon (mc-Si). Two groups of as-grown mc-Si wafers from different ingot height positions were subjected to the same thermal treatments with surface passivation by either silicon nitride (SiNx:H) or a temporary iodine-ethanol (I-E) chemical solution . With either passivation scheme, lifetime in the relatively low lifetime samples from the bottom of the ingot improves substantially. There are however key passivation-dependent differences in behavior in other parts of the ingot. Lifetime in relatively good wafers from the middle of the ingot is improved significantly with silicon nitride passivation but not with iodine-ethanol, for which substantial reductions in lifetime initially occur. There are also key differences in the internal gettering behavior of bulk iron. We suggest the differences arise because silicon nitride introduces hydrogen into the bulk, whereas the iodine-ethanol does not

Passivation effects on low-temperature gettering in multicrystalline silicon

Annealing at ≤ 500 °C changes minority carrier lifetime in as-grown multicrystalline silicon substantially. Part of the change arises from internal gettering of impurities, but surface passivation for lifetime measurement results in additional effects. We report experiments that aim to clarify the role of passivation. Long-term annealing (up to 60 h) is performed on silicon nitride passivated multicrystalline silicon, and lifetime and interstitial iron concentrations are monitored at each processing stage. Lifetime in all samples is improved under certain conditions, with improvements always achieved at 400 °C. Increases are pronounced in low-lifetime bottom samples, with improvement by a factor of 2.7 at 400 °C or 3.8 at 500 °C. Important differences are found compared with our previous study with iodine–ethanol passivation. First, as-received lifetime is higher with silicon nitride not due to a substantial difference in surface recombination. Second, while interstitial iron concentrations often initially increase with iodine–ethanol, they tend to reduce with silicon nitride. Third, lifetime in high-lifetime samples reduces substantially with iodine–ethanol but increases with silicon nitride. Secondary ion mass spectrometry reveals high iron concentrations in annealed silicon nitride. Results are discussed in terms of gettering of impurities to, and bulk passivation arising from, silicon nitride films

Increasing minority carrier lifetime in as-grown multicrystalline silicon by low temperature internal gettering

We report a systematic study into the effects of long low temperature (≤500 °C) annealing on the lifetime and interstitial iron distributions in as-grown multicrystalline silicon (mc-Si) from different ingot height positions. Samples are characterised in terms of dislocation density, and lifetime and interstitial iron concentration measurements are made at every stage using a temporary room temperature iodine-ethanol surface passivation scheme. Our measurement procedure allows these properties to be monitored during processing in a pseudo in situ way. Sufficient annealing at 300 °C and 400 °C increases lifetime in all cases studied, and annealing at 500 °C was only found to improve relatively poor wafers from the top and bottom of the block. We demonstrate that lifetime in poor as-grown wafers can be improved substantially by a low cost process in the absence of any bulk passivation which might result from a dielectric surface film. Substantial improvements are found in bottom wafers, for which annealing at 400 °C for 35 h increases lifetime from 5.5 μs to 38.7 μs. The lifetime of top wafers is improved from 12.1 μs to 23.8 μs under the same conditions. A correlation between interstitial iron concentration reduction and lifetime improvement is found in these cases. Surprisingly, although the interstitial iron concentration exceeds the expected solubility values, low temperature annealing seems to result in an initial increase in interstitial iron concentration, and any subsequent decay is a complex process driven not only by diffusion of interstitial iron

Sinbad Was In Bad : All The Time

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