Increasing the Longevity of Tungsten Filaments in a Zone Refiner

Zone refining is used for its ability to purify material and grow single crystals. To produce these single crystals, a suspended molten zone, generated by electron bombardment, passes along the polycrystalline stock. During a zone refining run, the filaments that produce the electron bombardment can fail. In this project, the longevity of tungsten filaments in a zone refiner was investigated. A new bombardment geometry was constructed to attempt to increase the longevity of the filaments. The new geometry had a shield machined into it to prevent line-of-sight impurities originating in the molten zone from striking the filaments. It was found that the new geometry did not significantly increase the lifespan of the filaments. The longevity of the tungsten filaments was longer in a zone refiner that had a pillbox with larger dimensions. It is thought that the increased pillbox size allows for a reduction in the density of impurities, thus limiting the amount striking the filament

Exploring the Electrical Properties of Twisted Bilayer Graphene

Two-dimensional materials exhibit properties unlike anything else seen in conventional substances. Electrons in these materials are confined to move only in the plane. In order to explore the effects of these materials, we have built apparatus and refined procedures with which to create two-dimensional structures. Two-dimensional devices have been made using exfoliated graphene and placed on gold contacts. Their topography has been observed using Atomic Force Microscopy (AFM) confirming samples with monolayer, bilayer, and twisted bilayer structure. Relative work functions of each have been measured using Kelvin Probe Force Microscopy (KPFM) showing that twisted bilayer graphene has a surface potential 20mV higher than that of monolayer graphene and 35 mV below bilayer graphene

Structural Inequality and the New Markets Tax Credit

The New Markets Tax Credit (“NMTC”) is a federal tax incentive used to promote investment in low-income neighborhoods. Many of these neighborhoods are home to historically marginalized communities. However, very few minority-led institutions participate in the NMTC program. This Article provides the first theoretical and empirical exploration of the underrepresentation of minority-led institutions in the NMTC program. Based on original interviews with representatives of Community Development Entities (“CDEs”), investors, borrowers, and consultants who participate in the NMTC program, this Article describes the “NMTC ecosystem,” a complex, relationship-driven network of NMTC program participants who influence decision-making and create opportunities for success within the NMTC program. The Article demonstrates that within the NMTC ecosystem, minority-led CDEs face structural barriers to entry similar to those that exist in purely private markets, such as unequal access to professional networks and lack of track records. Troublingly, those barriers are intensifying with time. The underrepresentation of minority-led CDEs in the NMTC program undermines its capacity to promote equitable economic development. To remedy that problem, this Article proposes that the Treasury should increase transparency and guidance in its administrative process, engage institutional intermediaries to aid minority-led CDEs, and relax requirements that chill participation among minority-led CDEs. These insights and prescriptions have relevance well beyond the context of the NMTC. In many domains, regulators have adopted measures that aim to promote equitable community development. This Article’s findings and reform recommendations thus have important implications for the broader universe of place-based regulatory policies, including for the many other tax incentive programs that aim to promote equity and reduce economic marginalization

Altered electroretinogram b-wave in a Suffolk sheep experimentally infected with scrapie

TRANSMISSIBLE spongiform encephalopathies (TSEs) are a group of fatal neurodegenerative diseases in which an abnormal isoform of the cellular prion protein (PrPSc) accumulates in tissues of the central nervous system. Accumulation of PrPSc occurs in the retina, a rostral projection of the central nervous system, of both natural and nonnatural host species with TSEs (Foster and others 1999, Spraker and others 2002, Head and others 2003, 2005, Hamir and others 2004, 2005, Kercher and others 2004, Greenlee and others 2006, Hortells and others 2006). In retinas from scrapie-affected sheep, PrPSc accumulation is primarily observed in the inner and outer plexiform layers, and in the ganglion cell layer (Jeffrey and others 2001, Greenlee and others 2006). Recent studies have reported few (Hortells and others 2006) or no (Greenlee and others 2006) histological lesions in the retinas of sheep affected with scrapie. However, morphological changes in specific retinal cell types have been demonstrated (Smith and others 2008). Despite the morphological consequences of retinal PrPSc accumulation in sheep (Barnett and Palmer 1971, Smith and others 2008), the functional impact on the retina of these animals is unknown. In the current study, the effect of TSE on retinal function in a scrapie-infected Suffolk sheep using flash electroretinography was investigated

Evaluation of a combinatorial approach to prion inactivation using an oxidizing agent, SDS, and proteinase K

BACKGROUND: Prions demonstrate an unusual resistance to methods effective at inactivating conventional microorganisms. This has resulted in a very tangible and difficult infection control challenge to the medical and veterinary communities, as well as animal agriculture and related industries. Currently accepted practices of harsh chemical treatments such as prolonged exposure to sodium hydroxide or sodium hypochlorite, or autoclaving are not suitable in many situations. Less caustic and more readily applicable treatments to contaminated environments are therefore desirable. We recently demonstrated that exposure of the RML scrapie agent to a commercial product containing sodium percarbonate (SPC-P) with or without sodium dodecyl sulfate (SDS) rendered PrP(Sc) sensitive to proteinase K (PK), but did not eliminate infectivity. The current study was designed to evaluate the efficacy of a combinatorial approach to inactivating prions by exposing RML-positive brain homogenate to SPC-P and SDS followed by PK. Treated samples were evaluated for PrP(Sc)-immunoreactivity by western blot, and residual infectivity by mouse bioassay. RESULTS: Treatment of infected brain homogenate with SPC-P and SDS followed by PK exposure resulted in a 4–5 log(10) reduction in infectivity when bioassayed in tga20 mice. CONCLUSIONS: This study demonstrates that exposure of the RML scrapie agent to SPC-P and SDS followed by PK markedly reduces, but does not eliminate infectivity. The results of this study encourage further investigation into whether consecutive or concomitant exposure to sodium percarbonate, SDS, and a protease may serve as a viable and non-caustic option for prion inactivation

Retinal function and morphology are altered in cattle infected with the prion disease transmissible mink encephalopathy

Transmissible spongiform encephalopathies (TSEs) are a group of diseases that result in progressive and invariably fatal neurologic disease in both animals and humans. TSEs are characterized by the accumulation of an abnormal protease-resistant form of the prion protein in the central nervous system. Transmission of infectious TSEs is believed to occur via ingestion of prion protein–contaminated material. This material is also involved in the transmission of bovine spongiform encephalopathy (“mad cow disease”) to humans, which resulted in the variant form of Creutzfeldt-Jakob disease. Abnormal prion protein has been reported in the retina of TSE-affected cattle, but despite these observations, the specific effect of abnormal prion protein on retinal morphology and function has not been assessed. The objective of this study was to identify and characterize potential functional and morphologic abnormalities in the retinas of cattle infected with a bovine-adapted isolate of transmissible mink encephalopathy. We used electroretinography and immunohistochemistry to examine retinas from 10 noninoculated and 5 transmissible mink encephalopathy–inoculated adult Holstein steers. Here we show altered retinal function, as evidenced by prolonged implicit time of the electroretinogram b-wave, in transmissible mink encephalopathy–infected cattle before the onset of clinical illness. We also demonstrate disruption of rod bipolar cell synaptic terminals, indicated by decreased immunoreactivity for the alpha isoform of protein kinase C and vesicular glutamate transporter 1, and activation of Müller glia, as evidenced by increased glial fibrillary acidic protein and glutamine synthetase expression, in the retinas of these cattle at the time of euthanasia due to clinical deterioration. This is the first study to identify both functional and morphologic alterations in the retinas of TSE-infected cattle. Our results support future efforts to focus on the retina for the development of new strategies for the diagnosis of TSEs

Device Therapies Among Patients Receiving Primary Prevention Implantable Cardioverter-Defibrillators in the Cardiovascular Research Network

BACKGROUND: Primary prevention implantable cardioverter-defibrillators (ICDs) reduce mortality in selected patients with left ventricular systolic dysfunction by delivering therapies (antitachycardia pacing or shocks) to terminate potentially lethal arrhythmias; inappropriate therapies also occur. We assessed device therapies among adults receiving primary prevention ICDs in 7 healthcare systems. METHODS AND RESULTS: We linked medical record data, adjudicated device therapies, and the National Cardiovascular Data Registry ICD Registry. Survival analysis evaluated therapy probability and predictors after ICD implant from 2006 to 2009, with attention to Centers for Medicare and Medicaid Services Coverage With Evidence Development subgroups: left ventricular ejection fraction, 31% to 35%; nonischemic cardiomyopathy \u3c 9 months\u27 duration; and New York Heart Association class IV heart failure with cardiac resynchronization therapy defibrillator. Among 2540 patients, 35% were \u3c 65 years old, 26% were women, and 59% were white. During 27 (median) months, 738 (29%) received \u3e /=1 therapy. Three-year therapy risk was 36% (appropriate, 24%; inappropriate, 12%). Appropriate therapy was more common in men (adjusted hazard ratio [HR], 1.84; 95% confidence interval [CI], 1.43-2.35). Inappropriate therapy was more common in patients with atrial fibrillation (adjusted HR, 2.20; 95% CI, 1.68-2.87), but less common among patients \u3e /=65 years old versus younger (adjusted HR, 0.72; 95% CI, 0.54-0.95) and in recent implants (eg, in 2009 versus 2006; adjusted HR, 0.66; 95% CI, 0.46-0.95). In Centers for Medicare and Medicaid Services Coverage With Evidence Development analysis, inappropriate therapy was less common with cardiac resynchronization therapy defibrillator versus single chamber (adjusted HR, 0.55; 95% CI, 0.36-0.84); therapy risk did not otherwise differ for Centers for Medicare and Medicaid Services Coverage With Evidence Development subgroups. CONCLUSIONS: In this community cohort of primary prevention patients receiving ICD, therapy delivery varied across demographic and clinical characteristics, but did not differ meaningfully for Centers for Medicare and Medicaid Services Coverage With Evidence Development subgroups

Attentional suppression of activity in the human visual cortex

We have used fMRI to examine the nature of the changes that occur in the human visual cortex when an observer attends to a particular location in the visual image. Previous studies have shown that the magnitude of the response to a visual stimulus is increased when the observer attends to the stimulus. We show that, in addition, attention to a particular location results in a widespread suppression of activity levels at all other locations. This suggests that a key mechanism of attentional modulation may be that spontaneous (baseline) levels of neural activity are adjusted in a position-dependent manner across the entire visual field

White-tailed deer are susceptible to the agent of sheep scrapie by intracerebral inoculation

Interspecies transmission studies afford the opportunity to better understand the potential host range and origins of prion diseases. The purpose of this experiment was to determine susceptibility of white-tailed deer to the agent of scrapie after intracerebral inoculation and to compare clinical signs and lesions to those reported for chronic wasting disease (CWD). Deer (n = 5) were inoculated with 1 mL of a 10% (wt/vol) brain homogenate derived from a sheep clinically affected with scrapie. A non-inoculated deer was maintained as a negative control. Deer were observed daily for clinical signs of disease and euthanized and necropsied when unequivocal signs of scrapie were noted. One animal died 7 months post inoculation (pi) due to intercurrent disease. Examinations of brain tissue for the presence of the disease-associated abnormal prion protein (PrPSc) by western blot (WB) and immunohistochemistry (IHC) were negative whereas IHC of lymphoid tissues was positive. Deer necropsied at 15-22 months pi were positive for scrapie by IHC and WB. Deer necropsied after 20 months pi had clinical signs of depression and progressive weight loss. Tissues with PrPSc immunoreactivity included brain (at levels of cerebrum, hippocampus, colliculus, cerebellum, and brainstem), trigeminal ganglion, neurohypophysis, retina, spinal cord, and various lymphoid tissues including tonsil, retropharyngeal and mesenteric lymph nodes, Peyer's patches, and spleen. This work demonstrates for the first time that white-tailed deer are susceptible to sheep scrapie by intracerebral inoculation. To further test the susceptibility of white-tailed deer to scrapie these experiments will be repeated with a more natural route of inoculation

Spatiotemporal Frequency and Direction Sensitivities of Human Visual Areas Measured Using fMRI

Using functional magnetic resonance imaging (fMRI) we have studied the variation in response magnitude, in each visual area (V1–V5), as a function of spatial frequency (SF), temporal frequency (TF) and unidirectional motion versus counterphase flicker. Each visual area was identified in each subject using a combination of retinotopic mapping fMRI and cortical flattening techniques. A drifting (or counterphasing) sinusoidal grating was used as the stimulus in a study in which we parametrically varied SF between 0.4 and 7 cycles/degree and TF between 0 and 18 Hz. For each experiment we constructed fMRI amplitude tuning curves, averaged across subjects, for each visual area. The tuning curves that resulted are consistent with the known physiological properties of cells in the corresponding macaque visual areas, previous functional imaging studies, and in the case of V1, the psychophysically determined contrast sensitivity functions for spatial and temporal frequency. In the case of V3A, the SF tuning functions obtained were more similar to those found in single cell studies of macaque V3 rather than macaque V3A. All areas showed at least a moderate preference for directed versus counterphasing motion with V5 showing the largest preference. Visual areas V1, V2, V3, and V3A showed more direction sensitivity at low spatial frequencies, while VP, V4, and V5 had the highest drifting versus counterphasing ratios for higher spatial frequencies