Excimers He2* as tracers of quantum turbulence in 4He in the t = 0 limit.

We have studied the interaction of metastable 4He2* excimer molecules with quantized vortices in superfluid 4He in the zero temperature limit. The vortices were generated by either rotation or ion injection. The trapping diameter of the molecules on quantized vortices was found to be 96±6 nm at a pressure of 0.1 bar and 27±5 nm at 5.0 bar. We have also demonstrated that a moving tangle of vortices can carry the molecules through the superfluid helium.

Study of dielectric breakdown in liquid xenon with XeBrA: The xenon breakdown apparatus.

Maintaining the electric fields necessary for the current generation of noble liquid time projection chambers (TPCs), with drift lengths exceeding 1 m, requires a large negative voltage applied to their cathode. Delivering such high voltage is associated with an elevated risk of electrostatic discharge and electroluminescence, which would be detrimental to the performance of the experiment. The Xenon Breakdown Apparatus (XeBrA) is a 5-l, high voltage test chamber built to investigate the contributing factors to electrical breakdown in noble liquids. In this work, we present the main findings after conducting scans over stressed electrode areas, surface finish, pressure, and high voltage ramp speed in the medium of liquid xenon. Area scaling and surface finish were observed to be the dominant factors affecting breakdown, whereas no significant changes were observed with varying pressure or ramp speed. A general rise in both the anode current and photon rate was observed in the last 30 s, leading up to a breakdown, with a marked increase in the last couple of seconds. In addition, the position of breakdowns was reconstructed with a system of high-speed cameras and a moderate correlation with the Fowler-Nordheim field emission model was found. Tentative evidence for bubble nucleation being the originating mechanism of breakdown in the liquid was also observed. We deem the results presented in this work to be of particular interest for the design of future, large TPCs, and practical recommendations are provided.

Search for light dark matter in XENON10 data.

We report results of a search for light (≲10 GeV) particle dark matter with the XENON10 detector. The event trigger was sensitive to a single electron, with the analysis threshold of 5 electrons corresponding to 1.4 keV nuclear recoil energy. Considering spin-independent dark matter-nucleon scattering, we exclude cross sections σ(n)>7×10(-42) cm(2), for a dark matter particle mass m(χ)=7 GeV. We find that our data strongly constrain recent elastic dark matter interpretations of excess low-energy events observed by CoGeNT and CRESST-II, as well as the DAMA annual modulation signal.

Visualization study of counterflow in superfluid 4He using metastable helium molecules.

Heat is transferred in superfluid 4He via a process known as thermal counterflow. It has been known for many years that above a critical heat current the superfluid component in this counterflow becomes turbulent. It has been suspected that the normal-fluid component may become turbulent as well, but experimental verification is difficult without a technique for visualizing the flow. Here we report a series of visualization studies on the normal-fluid component in a thermal counterflow performed by imaging the motion of seeded metastable helium molecules using a laser-induced-fluorescence technique. We present evidence that the flow of the normal fluid is indeed turbulent at relatively large velocities. Thermal counterflow in which both components are turbulent presents us with a theoretically challenging type of turbulent behavior that is new to physics.

Invited article: development of high-field superconducting Ioffe magnetic traps.

We describe the design, construction, and performance of three generations of superconducting Ioffe magnetic traps. The first two are low current traps, built from four racetrack shaped quadrupole coils and two solenoid assemblies. Coils are wet wound with multifilament NbTi superconducting wires embedded in epoxy matrices. The magnet bore diameters are 51 and 105 mm with identical trap depths of 1.0 T at their operating currents and at 4.2 K. A third trap uses a high current accelerator-type quadrupole magnet and two low current solenoids. This trap has a bore diameter of 140 mm and tested trap depth of 2.8 T. Both low current traps show signs of excessive training. The high current hybrid trap, on the other hand, exhibits good training behavior and is amenable to quench protection.

Calorimetric Observation of Single He 2 ∗ Excimers in a 100-mK He Bath.

We report the first calorimetric detection of individual He 2 ∗ excimers within a bath of superfluid 4 He . The detector used in this work is a single superconducting titanium transition edge sensor (TES) with an energy resolution of ∼ 1 eV , immersed directly in the helium bath. He 2 ∗ excimers are produced in the surrounding bath using an external gamma-ray source. These excimers exist either as short-lived singlet or long-lived triplet states. We demonstrate detection (and discrimination) of both states: In the singlet case the calorimeter records the absorption of a prompt ≈ 15 eV photon, and in the triplet case the calorimeter records a direct interaction of the molecule with the TES surface, which deposits a distinct fraction of the ≈ 15 eV , released upon decay, into the surface. We also briefly discuss the detector fabrication and characterization.

Producing and imaging a thin line of He*2 molecular tracers in helium-4.

Cryogenic helium-4 has long been recognized as a useful material in fluids research. The unique properties of helium-4 in the gaseous phase and the normal liquid phase allow for the generation of turbulent flows with exceptionally high Reynolds and Rayleigh numbers. In the superfluid phase, helium-4 exhibits two-fluid hydrodynamics and possesses fascinating properties due to its quantum nature. However, studying the flows in helium-4 has been very challenging largely due to the lack of effective visualization and velocimetry techniques. In this article, we discuss the development of novel instrumentation for flow-visualization in helium based on the generation and imaging of thin lines of metastable He*2 tracer molecules. These molecular tracers are created via femtosecond-laser field-ionization of helium atoms and can be imaged using a laser-induced fluorescence technique. By observing the displacement and distortion of the tracer lines in helium, quantitative information about the flow field can be extracted. We present experimental results in the study of thermal counterflow in superfluid helium that validate the concept of this technique. We also discuss anticipated future developments of this powerful visualization technique.

Underlying cardiac lesions in adults with infective endocarditis. The changing spectrum.

The spectrum of recognized cardiac lesions underlying infective endocarditis has been changing as a result of the decline in incidence of rheumatic heart disease, the recognition of the entity of mitral valve prolapse, and the improvement in cardiac diagnostic techniques. Sixty-three cases of native valve endocarditis diagnosed in Memphis hospitals between 1980 and 1984 were reviewed. All diagnoses of underlying cardiac lesions were confirmed by two-dimensional echocardiography, cardiac catheterization, and/or histopathologic examination of valve tissues. Major categories of underlying lesions were as follows: mitral valve prolapse, 29 percent; no underlying disease, 27 percent; degenerative lesions of the aortic or mitral valve, 21 percent; congenital heart disease, 13 percent; rheumatic heart disease, 6 percent. Thus, mitral valve prolapse and, in the elderly, degenerative lesions have displaced rheumatic and congenital heart diseases as the major conditions underlying endocarditis. Redundancy of the mitral valve leaflets was noted in 17 of 18 patients in whom endocarditis was superimposed upon mitral valve prolapse. The risk of infective endocarditis appears to be substantially increased in the subset of patients with mitral valve prolapse who exhibit valvular redundancy.

Prevention of relapse of histoplasmosis with fluconazole in patients with the acquired immunodeficiency syndrome.

OBJECTIVE: To assess the effectiveness of fluconazole for suppression of relapse of histoplasmosis in patients with acquired immunodeficiency syndrome (AIDS). DESIGN: Retrospective, nonrandomized, open trial. SETTING: Multicenter at two university referral centers and in five private practices. PATIENTS: Seventy-six patients with AIDS and disseminated histoplasmosis who completed induction treatment with amphotericin B, itraconazole, or fluconazole and maintained on treatment with fluconazole to prevent relapse. INTERVENTIONS: Fluconazole was given at dosages of 100 to 400 mg per day. Patients were followed by their primary physicians, who completed questionnaires collecting information about treatment and relapse status. Blood and urine specimens were submitted periodically for Histoplasma capsulatum var. capsulatum antigen determination. MEASUREMENTS AND MAIN RESULTS: Nine of the 76 patients relapsed during fluconazole therapy and another was removed from the study because of allergic rash. Survival after initiation of therapy for histoplasmosis was 94 weeks, ranging from 74 weeks for those who received less than 1 g of amphotericin B for induction and none for maintenance therapy to 156 weeks for those who received greater than 1 g for induction and additional amphotericin B for maintenance therapy before beginning fluconazole (P < 0.02). Antigen levels fell at rates of 0.05 units/week in urine and 0.02 units/week in serum in patients who were successfully maintained in remission and increased by > or = 2 units/week in 4 of 6 patients who relapsed. CONCLUSIONS: Fluconazole > or = 200 mg daily is a reasonable choice for chronic suppressive therapy of histoplasmosis in patients who cannot take itraconazole because of drug interactions, malabsorption, or side effects.

Treatment of histoplasmosis with fluconazole in patients with acquired immunodeficiency syndrome. National Institute of Allergy and Infectious Diseases Acquired Immunodeficiency Syndrome Clinical Trials Group and Mycoses Study Group.

PURPOSE: This study assesses the efficacy and safety of fluconazole therapy in patients with acquired immunodeficiency syndrome (AIDS) and mild to moderately severe manifestations of disseminated histoplasmosis. PATIENTS AND METHODS: This was a multicenter, open-label, nonrandomized prospective trial. All patients had AIDS and disseminated histoplasmosis. Patients were treated with 1,200 mg of fluconazole given by mouth once on the first day, then 600 mg once daily for 8 weeks, and those patients who improved clinically were then assigned fluconazole maintenance therapy 200 mg once daily for at least 1 year. Interim analysis revealed a high failure rate (10 of 20, 50%), causing revision of the protocol to increase the fluconazole dose to 1,600 mg given once on the first day, then 800 mg once daily, and the duration to 12 weeks for induction therapy and then 400 mg daily for 1 year for maintenance therapy. MEASUREMENTS AND MAIN RESULTS: Thirty-six of 49 patients (74%; 95% confidence interval [CI]: 59% to 85%) with mild to moderately severe clinical manifestations who entered into the revised study responded to 800 mg of fluconazole daily for 12 weeks as induction therapy. Of the seven patients who failed induction therapy because of progression of histoplasmosis, one died of the infection. Of 36 patients who entered into the maintenance phase of the study receiving 400 mg of fluconazole daily for 1 year, 11 (30.5%) relapsed, including one who died (2.8%). Two of the 49 patients (4.1%) were removed because of grade 4 adverse events, alkaline phosphatase elevation for one and aspartate aminotransferase elevation in the other. The relapse-free rate at 1 year was 53% (95% CI: 32% to 89%), prompting closure of the study. CONCLUSIONS: Fluconazole 800 mg daily is a safe and moderately effective induction therapy for mild or moderately severe disseminated histoplasmosis in patients with AIDS. On the basis of historic comparison, fluconazole 400 mg daily is less effective than itraconazole 200 to 400 mg daily or amphotericin B 50 mg given weekly as maintenance therapy to prevent relapse.

Recurrent massive pleural effusion due to pleural, pericardial, and epicardial fibrosis in histoplasmosis.

Acute histoplasmosis is generally a benign, self-limited pulmonary infection. Although Histoplasma capsulatum pneumonitis is common, pleural effusions associated with histoplasmosis are quite rare, and massive pleural effusions have not been reported. There have been several reports of pericardial fibrosis secondary to histoplasmosis, but epicardial fibrosis has not been described. We report a biopsy-proven case of histoplasmosis initially associated with recurrent massive pleural effusions and excessive pleural fibrosis causing a trapped lung. The patient later developed constrictive pericarditis. Despite pericardiectomy, severe cor pulmonale occurred, and the patient died. Necropsy demonstrated fibrosis of the epicardium.

Effects of injury severity on regional and temporal mRNA expression levels of calpains and caspases after traumatic brain injury in rats.

Despite a preponderance of studies demonstrating gene expression and/or enzymatic activation of calpain and caspase proteases after traumatic brain injury (TBI), no studies have examined the effects of injury magnitude on expression levels of these cell death effectors after TBI. Determination of the degree to which injury severity affects specific expression profiles is critical to understanding the relevant pathways contributing to post-trauma pathology and for developing targeted therapeutics. This investigation tested the hypothesis that different injury magnitudes (1.0, 1.2, and 1.6 mm) cause alterations in the regional and temporal patterns of mRNA expression of calpain-related (calpain-1 and -2, calpastatin) and caspase-related (caspases -3, -8, -9, BID) gene products after cortical impact in rats. Quantitative RT-PCR was used to compare effects of injury severity on mRNA levels in ipsilateral (injured) cortex and hippocampus, 6 h to 5 days post-injury. TBI caused increases in mRNA expression of all proteins examined, with the highest expression detected in the cortex. Generally, injury magnitude and levels of gene expression were positively correlated. High levels of gene induction were observed with BID, caspase-3, and -8, while caspase-9 mRNA had the lowest level of induction. Interestingly, although calpains are activated within minutes of TBI, calpain mRNA expression was highest 72 h to 5 days post-TBI. This study is the first analysis of the regional and temporal expression of calpains and caspases after TBI. These data provide insight into the inter-relationship of these two protease families and on the distinct but overlapping cascades of cell death after TBI.

The effect of a portable HEPA-filtered body exhaust system on airborne microbial contamination in a conventional operating room.

OBJECTIVE: To study the effect of a portable HEPA-filtered air exhaust system (Stackhouse Freedom Surgical Helmet System) on airborne microbial contamination in a modern conventional operating room. DESIGN AND SETTING: Microbial air sampling was done with a two-stage Anderson sampler at the wound site during 46 total joint replacements. All operations were performed by the same surgeon in the same operating room at a large community hospital. RESULTS: In 18 cases done without air exhaust hoods, the number of bacterial and fungal colony-forming units (CFU) ranged from 0.6 to 11.7 (mean, 3.6). Air sampling during 28 operations with the operating team in air exhaust hoods revealed a mean of 3.6 CFU (range, 0 to 11.4). Bacterial CFU averaged 3.4 without hoods and 3.2 with exhaust hoods. Coagulase-negative staphylococci were the most common isolates (48% of isolates with hood, 55% without hood). No infections occurred. CONCLUSION: We concluded that these air exhaust hoods did not lower airborne microbial contamination detectable with this air sampling method, as compared to standard head cover and mask, in a modern conventional operating room.

Histoplasmosis in patients with acquired immunodeficiency syndrome. Hematologic and bone marrow manifestations.

In areas where Histoplasma capsulatum infections are endemic in the United States, there is an increasing frequency of progressive disseminated histoplasmosis (PDH) as an opportunistic infection in patients with acquired immune deficiency syndrome (AIDS). The bone marrow and peripheral blood (PB) specimens in 13 patients with AIDS and PDH were reviewed. Anemia, leukopenia, and thrombocytopenia were found in 12, 10, and 7 patients, respectively. Circulating organisms were detected in the blood smears or buffy coat preparations from five patients and were associated with PB nRBCs and severe absolute monocytopenia. Morphologically, the marrow specimens showed one of four patterns: (1) no morphologic evidence of infection (two patients, one with a positive marrow culture); (2) discrete granulomas (two patients, both with positive marrow cultures); (3) lymphohistiocytic aggregates (six patients, four with positive marrow cultures); and (4) diffuse macrophage infiltrates (three patients, all with positive marrow cultures). Morphologic examination of the bone marrow combined with cultures is useful in diagnosing disseminated histoplasmosis in patients with AIDS. However, the morphologic findings in the bone marrow may be different in patients with AIDS compared with non-AIDS patients, and seemingly nondiagnostic morphologic features must be approached with a high degree of suspicion in diagnosing infections with H. capsulatum in this population.

Hydroxyurea in combination with didanosine and stavudine in antiretroviral-experienced HIV-infected subjects with a review of the literature.

The safety and efficacy of hydroxyurea with didanosine in combination with stavudine in nucleoside reverse-transcriptase inhibitor (NRTI)-experienced patients was investigated. Entry criteria included HIV-1 infected, NRTI-experienced adults, with CD4(+) counts 50-550 cells/mm(3) and viral loads >or=12,500 copies/mL. Subjects were treated with didanosine 200 mg twice a day (BID), stavudine 40 mg BID, and hydroxyurea 1000 mg daily for 16 weeks. Thirty-one HIV-1 subjects with mean bDNA viral load 1x10(5) log(10) copies/mL and mean CD4(+) T-cell counts of 231 cells/mm(3) were enrolled. A 1.3 log(10) decrease in mean viral load was seen at 12 weeks of therapy. Prior didanosine use resulted in a more rapid response to therapy compared with prior zidovudine use. Side effects consisting of neutropenia, pancreatitis, and peripheral neuropathy occurred in four subjects and resolved upon withdrawal of therapy. This non-randomized study in subjects with a mean CD4(+) T-cell count of 230 cells/mm(3) demonstrates the antiviral activity of hydroxyurea+didanosine and stavudine. Toxicities related to therapy need to be followed closely. The results support the need for a randomized, prospective study to determine the safety and efficacy of hydroxyurea plus didanosine in antiretroviral-experienced patients with CD4(+) cell counts below 300 cells/mm(3).

Histoplasmosis in AIDS: advances in management.

Histoplasmosis is one of the most common opportunistic infections in HIV-infected patients who reside in endemic areas, and "imported infections" also occur elsewhere. A recent decline in the incidence of histoplasmosis appears to correlate with advances in antiretroviral therapy. Histoplasmosis occurs due to either dissemination of newly acquired infection or reactivation of latent foci of infection. Major risk factors include a CD4 count < or = 150/microL, positive complement fixation serology for the Histoplasma capsulatum mycelial antigen, and a history of exposure to chicken coops; in addition, suboptimal antiretroviral therapy seems likely to be a risk factor. Although there are a variety of clinical manifestations, most patients present with a several-week history of fever, chills, weakness, and weight loss. Diagnosis is based on positive cultures of blood, bone marrow, or other sites; detection of antigen in serum or urine; or characteristic histopathologic findings in biopsy specimens. Induction therapy consists of amphotericin B for acutely ill patients or itraconazole for patients with mild to moderately severe disease. Subsequent lifelong maintenance therapy with itraconazole is recommended. In patients with CD4 counts of < or = 150/microL, itraconazole is effective primary prophylaxis.

Histoplasmosis in Missouri: historical review and current clinical concepts.

Histoplasmosis is particularly common in Missouri, and many important clinical observations about the disease were made in this state in the 1950s and 1960s. When the AIDS epidemic spread to Missouri in the mid-1980s, histoplasmosis became recognized as a common and important opportunistic infection among Missourians with AIDS. Clinicians must maintain a high level of suspicion for histoplasmosis in any HIV-infected patient who presents with unexplained fever, particularly if the patient has evidence of hepatosplenomegaly, generalized lymphadenopathy, pancytopenia, abnormal liver function tests, or bilateral pulmonary infiltrates. The diagnosis of histoplasmosis can be established rapidly by observation of organisms on peripheral blood smear or bone marrow biopsy specimens or by Histoplasma Polysaccharide Antigen testing. The diagnosis can be confirmed by blood cultures in most cases. Histoplasmosis in AIDS is invariably fatal if not treated. Treatment consists of two phases: initial induction therapy and subsequent lifelong maintenance therapy. Amphotericin B and itraconazole are extremely effective for induction and maintenance therapy; fluconazole appears to be effective maintenance therapy. Strategies for the prevention of histoplasmosis in high risk patients are being evaluated currently.