Progressive HIV infection is characterized by dysregulation of the intestinal immune barrier, translocation of immunostimulatory microbial products, and chronic systemic inflammation that is thought to drive progression of disease to AIDS. Elements of this pathologic process persist despite viral suppression during highly active antiretroviral therapy (HAART) and drivers of these phenomena remain poorly understood. Disrupted intestinal immunity can precipitate dysbiosis that induces chronic inflammation in the mucosa and periphery of mice. However, putative microbial drivers of HIV-associated immunopathology versus recovery have not been identified in humans. Using high-resolution bacterial community profiling, we identified a dysbiotic mucosal-adherent community enriched in Proteobacteria and depleted of Bacteroidia members that was associated with markers of mucosal immune disruption, T cell activation, and chronic inflammation in HIV-infected subjects. Furthermore, this dysbiosis was evident among HIV-infected subjects undergoing HAART, and the extent of dysbiosis correlated with activity of the kynurenine pathway of tryptophan metabolism and plasma concentrations of the inflammatory cytokine interleukin-6 (IL-6), two established markers of disease progression. Gut-resident bacteria with capacity to metabolize tryptophan through the kynurenine pathway were found to be enriched in HIV-infected subjects, strongly correlated with kynurenine levels in HIV-infected subjects, and capable of kynurenine production in vitro. These observations demonstrate a link between mucosal-adherent colonic bacteria and immunopathogenesis during progressive HIV infection, which is apparent even in the setting of viral suppression during HAART. This link suggests that gut-resident microbial populations may influence intestinal homeostasis during HIV disease.

Magnetic resonance (MR) imaging is often performed to determine the cause of palmar heel pain. We evaluated how distension of the navicular bursa affected the MR appearance of the navicular bursa and associated structures. An MR evaluation was performed on normal cadaver limbs and cadaver limbs from horses with lameness localized to the foot. The normal navicular bursae were injected with 2, 4, or 6 ml of solution. The bursae of the feet from lame horses were injected with 4 or 6 ml, and the MR study was repeated. All bursae were examined grossly to verify the presence or absence of adhesions. Clinical patients that had initial MRI abnormalities suggesting adhesions were also evaluated. Distension of the proximal recess of the normal navicular bursa, proximal to the collateral sesamoidean ligament was achieved with 2 ml. Separation of the collateral sesamoidian ligament from the deep digital flexor tendon (DDFT) was achieved with 4 ml. The separation of the navicular bone from the DDFT and distal sesamoidian impar ligament required 6 ml. Adhesions were more clearly defined in the bursa of the two pathologic cadaver limbs following distension. MR bursography used on clinical patients allowed the determination of the presence or absence of adhesions. In these horses, this determination could not have been definitively made without this technique. MR bursography is useful in horses where the presence of adhesions cannot be clearly defined by MRI.

The single event upset (SEU) sensitivity of certain types of linear microcircuils is strongly affected by bias conditions. For these devices, a model of upset mechanism and a method for SIX7 control have been suggested. I. INTRODIJCTIONThe history of the single event upset (SEIJ) study of linear integrated circuits (ICs) is relatively short. The first reporting of SETJs in linear ICs took place in 1993 [l]. This can be compared with the substantially longer history of the total ionizing dose (TID) investigation of linear ICs, including those involving electron irradiation [2,3]. I Iowever, the study of SEIJs in linear ICs (which have also hcen called analog S E W hac. gained attention [4, 5 , 6 ] in recent years partly due to the detrimental effects which may resulc from analog SElJs in space home electronics systems. For ex,mple, battery charging circuits, which incorporate a voltage comparator followed by a D-type flip-flop, have tenninatcd the charging process when the comparator is irradiated by heavy ions. Similar systems have been utilized in space to charge batteries with the use of solar panels. In other cases, analog SEI Js may be tolcrated, although they are a nuisance 171. While previous studies of analog SEUs have included test results obtained for varying bias settings [4,5,6], the majority of the test results have been obtaincd with a rclativcly small number of input bias settings. Therefore, a substantial difference in the sensitivity of a tcst device type due to different bias conditions has not been reported. In ordcr to better understand the upset mechanisms and to possibly mitigate the impact of SElJs on the system, we have exposed several types of linear ICs biased in varying conditions to heavy ions. This has extended the scope of SEU observations in linear ICs to include various quiescent input conditions. The current investigation has led to a finding in which SEIJ sensitivity may be reduced by controlling the quiescent input conditions in some types of linear ICs. TEST DEVICESTest device types include voltage comparators, operational amplifiers, and other linear integrated circuits, all of which incorporate a difference amplifier circuit at the input section.The input section has been shown to bc sensitive to hcavy ions in similar circuits 111. The test device types are shown in Table 1.The LM119 voltage comparator incorporates npn transistors in the difference amplifier sections @1, D2, and D3) and the level shift section (L) as shown in Figure 1. This is designed for high speed applications and it provides a response time of less than 100 nanoseconds. The positive and the negative inputs (+VIN and -VIN) are directly tied to the transistors 01 and Q2, respectively, in the D1 amplifier.LM139 and LM111 voltage comparators incorporate pnp transistors in the front section, where the initial amplification takes place. These devices are of much older design and have a relatively slow time response. The response times for LM139 and LM111 are about 1.3 microseconds and 200 nanoseconds, respectiv...

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The input bias current (Ira) of the National L M l l 1 voltage comparator exhibits a non-monotonic response to total dose irradiations at various dose rates. At low total doses, below 100 krad(SiOz), increased 2, is due primarily to gain degradation in the circuit's input transistors. At high total doses, above 100 krad(SiOz), Ira shows a downward trend that indicates the influence of compensating circuit mechanisms. Through correlation of transistor and circuit response, the transistors responsible for these compensating mechanisms are identificd. Non-input transistors in the circuit's input stage lower the emitter-base operating point voltage of the input device. Lower emitter-basc voltages reduce the base current supplied by the input transistors, causing a moderate "recovery" in the circuit response.