2,721 research outputs found

    And yet it moves: The dangers of artificially fixing the Milky Way center of mass in the presence of a massive Large Magellanic Cloud

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    Motivated by recent studies suggesting that the Large Magellanic Cloud (LMC) could be significantly more massive than previously thought, we explore whether the approximation of an inertial Galactocentric reference frame is still valid in the presence of such a massive LMC. We find that previous estimates of the LMC's orbital period and apocentric distance derived assuming a fixed Milky Way are significantly shortened for models where the Milky Way is allowed to move freely in response to the gravitational pull of the LMC. Holding other parameters fixed, the fraction of models favoring first infall is reduced. Due to this interaction, the Milky Way center of mass within the inner 50 kpc can be significantly displaced in phase-space in a very short period of time that ranges from 0.3 to 0.5 Gyr by as much as 30 kpc and 75 km/s. Furthermore, we show that the gravitational pull of the LMC and response of the Milky Way are likely to significantly affect the orbit and phase space distribution of tidal debris from the Sagittarius dwarf galaxy (Sgr). Such effects are larger than previous estimates based on the torque of the LMC alone. As a result, Sgr deposits debris in regions of the sky that are not aligned with the present-day Sgr orbital plane. In addition, we find that properly accounting for the movement of the Milky Way around its common center of mass with the LMC significantly modifies the angular distance between apocenters and tilts its orbital pole, alleviating tensions between previous models and observations. While these models are preliminary in nature, they highlight the central importance of accounting for the mutual gravitational interaction between the MW and LMC when modeling the kinematics of objects in the Milky Way and Local Group.Comment: Accepted for publication in ApJ; 16 pages, 11 figure

    Analysis of multiply spliced transcripts in lymphoid tissue reservoirs of rhesus macaques infected with RT-SHIV during HAART.

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    Highly active antiretroviral therapy (HAART) can reduce levels of human immunodeficiency virus type 1 (HIV-1) to undetectable levels in infected individuals, but the virus is not eradicated. The mechanisms of viral persistence during HAART are poorly defined, but some reservoirs have been identified, such as latently infected resting memory CD4⁺ T cells. During latency, in addition to blocks at the initiation and elongation steps of viral transcription, there is a block in the export of viral RNA (vRNA), leading to the accumulation of multiply-spliced transcripts in the nucleus. Two of the genes encoded by the multiply-spliced transcripts are Tat and Rev, which are essential early in the viral replication cycle and might indicate the state of infection in a given population of cells. Here, the levels of multiply-spliced transcripts were compared to the levels of gag-containing RNA in tissue samples from RT-SHIV-infected rhesus macaques treated with HAART. Splice site sequence variation was identified during development of a TaqMan PCR assay. Multiply-spliced transcripts were detected in gastrointestinal and lymphatic tissues, but not the thymus. Levels of multiply-spliced transcripts were lower than levels of gag RNA, and both correlated with plasma virus loads. The ratio of multiply-spliced to gag RNA was greatest in the gastrointestinal samples from macaques with plasma virus loads <50 vRNA copies per mL at necropsy. Levels of gag RNA and multiply-spliced mRNA in tissues from RT-SHIV-infected macaques correlate with plasma virus load

    Environmental Clustering of New Zealand Dairy Herds

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    Previous studies have found that milk yield (a proxy for feeding level) and temperature-humidity index (THI) are important factors in explaining genotype x environment (G x E) interactions, indicating differences between the abilities of genotypes to forage or consume concentrates effectively or to cope with thermal stress (Ravagnolo and Misztal, 2000; Zwald et al., 2003). The objective of this study was to quantify and cluster (CL) herd environments within New Zealand (NZ) based on production levels, a summer heat load index (HLI) and geographical location

    Patient Perceptions of Trauma-Focused Telemental Health Services Using the Telehealth Satisfaction Questionnaire (TSQ)

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    Telehealth services can address many barriers to traditional office-based mental health services. Few studies have assessed youth and caregiver perceptions of and satisfaction with trauma-focused interventions delivered via telemental health. The current study presents data collected using the Telehealth Satisfaction Questionnaire (TSQ), which was developed to measure child and caregiver satisfaction with services, comfort with the telehealth equipment, and barriers to traditional office-based services. Thirteen clinicians delivered home- and school-based Trauma-Focused Cognitive Behavioral Therapy (TF-CBT) via videoconferencing on tablets and computers to 60 child patients (71.7% Latinx, 18.3% Black, and 10.0% non-Hispanic White). Patients and caregivers completed the TSQ at treatment discharge via telephone, videoconferencing, or in-person interviews. There was a high level of satisfaction among patients and caregivers receiving TF-CBT via telemental health. Furthermore, most youth and caregivers felt comfortable using the telehealth equipment from the outset of therapy, and all participants who were not initially comfortable using the equipment reported feeling more comfortable over time. The most common barriers to traditional office-based services were caregiver work schedule (57.7%), distance to mental health clinic (55.8%), and lack of transportation (44.2%). Patients and caregivers expressed a preference for telemental health services if given the option between receiving therapy via videoconferencing versus going to an office-based clinic. Findings indicated telemental health treatment addressed barriers that would have otherwise prevented families from accessing office-based services. The Telehealth Satisfaction Questionnaire can be used to help clinics and providers assess patient and caregiver satisfaction with telehealth services in various settings

    Interpreter perspectives on working with trauma patients: Challenges and recommendations to improve access to care.

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    Given the growing number of immigrant and limited-English-proficiency individuals in the U.S., accessing language-congruent services can be a significant barrier for many seeking mental health treatment. The use of spoken-language interpreters can help address this barrier; however, the interpretation in the context of trauma therapy can be particularly challenging for interpreters without mental health training. This quality improvement study explores issues identified by interpreters assisting in the provision of trauma-focused treatment for primarily immigrant populations. Ten certified medical interpreters (nine Spanish-language interpreters and one American Sign Language interpreter) participated in a focus group at a specialty trauma clinic in the southeastern U.S. Core findings concerned the challenges of interpreting (i.e., use of mental health terminology, little time to process emotionally charged sessions, the impact of vicarious trauma, difficulties related to the speed of interpreting and interpreting for multiple patients at once, logistical difficulties, and the availability of interpreters). Interpreters also identified perceived needs and provided recommendations for overcoming challenges (i.e., holding presession meetings with clinicians, ensuring breaks between trauma patients, creating a support group for interpreters, ensuring a direct telephonic line between interpreters and the trauma clinic, providing interpreters with session materials before appointments, and training clinicians on the use of interpreters specifically for trauma treatment). Specific recommendations for agencies and clinicians new to the use of interpreters for trauma-focused services can ultimately enhance service provision for trauma patients in need of language-congruent services

    Resultados a medio y largo plazo de la utilización de videotoracoscopia en la cirugía de resección de las metástasis pulmonares

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    The surgical resection of pulmonary metastases is a method of treatment accepted as habitual in thoracic surgery. However, it continues to be a source of controversy if this resection must be realised by thoracotomy or by modern video-assisted techniques. With the aim of finding a response to this controversy in our work milieu, a review was made of the surgical interventions carried out in order to resect pulmonary metastases. Between January 1997 and December 2001, 56 patients were found whose pulmonary metastases had been resected by videothorascopy out of a total of 252 metastasectomies (22.2%). The primary tumours were classified in 4 groups: sarcoma (n=11); colorectal (n=25); renal (n=5); and others (n=15). Videothoroscopy was carried out on the right hemithorax (n=28), left hemithorax (n=22) or on both at once (n=6). Operational mortality was nil and the only morbidity attributable to the technique was a defect of re-expansion following the removal of the thoracic drainage in one patient. Using the Kaplan-Meier method, the probability of survival in this series of patients was 60.4% after 5 years, with an average survival time of 48 months. All of this data supports the use of videothorascopy in our milieu on patients with pulmonary metastases. However, in the light of the results, it is important in using this technique to place special emphasis on obtaining good margins of resection, due to the real risk of local recurrence on these margins in the medium term

    Calculation of a cow culling merit index including specific heterosis in a multibreed dairy population

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    Abstract. The objective of this study was to compare two models for the estimation of producing values (EPV) for lactation yields of milk, fat and protein, and calving interval (CI), which were combined in an index called the Cow Culling Merit Index (CMI), in Irish dairy cattle. Data comprised 188 927 records for production and 157 117 records for CI, collected on North American Holstein Friesian (HO), Friesian (FR), Jersey (JE), and Montbéliarde (MO) pure breeds, and some of their crosses. Cows calved from 2002 to 2006 and were from parities 1 to 5. Coefficients of specific heterosis for HO×FR, HO×JE, and HO×MO were calculated for each cow from parental breed information. The coefficient of general heterosis (GH) for each cow was obtained as the sum of the specific coefficients previously estimated. Model 1 included fixed effects of contemporary group, age at calving within parity, linear regression on gene proportions for FR, JE, and MO, and linear regression on the coefficient of expected GH. Additive genetic, permanent environmental, and error were random effects. Model 2 was based on Model 1 but GH was replaced by linear regressions on coefficients of expected specific heterosis for HO×FR, HO×JE, and HO×MO. Estimated producing values were calculated as the sum of estimated breeding value, permanent environmental and heterosis effects. The inclusion of coefficients of specific heterosis in the model did not produce re-ranking of animals but important differences in EPVs were observed in crossbred cows. These changes are important if EPVs are used to develop a culling merit index

    Improving Deep Brain Stimulation Electrode Performance in vivo Through Use of Conductive Hydrogel Coatings

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    Active implantable neurological devices like deep brain stimulators have been used over the past few decades to treat movement disorders such as those in people with Parkinson’s disease and more recently, in psychiatric conditions like obsessive compulsive disorder. Electrode-tissue interfaces that support safe and effective targeting of specific brain regions are critical to success of these devices. Development of directional electrodes that activate smaller volumes of brain tissue requires electrodes to operate safely with higher charge densities. Coatings such as conductive hydrogels (CHs) provide lower impedances and higher charge injection limits (CILs) than standard platinum electrodes and support safer application of smaller electrode sizes. The aim of this study was to examine the chronic in vivo performance of a new low swelling CH coating that supports higher safe charge densities than traditional platinum electrodes. A range of hydrogel blends were engineered and their swelling and electrical performance compared. Electrochemical performance and stability of high and low swelling formulations were compared during insertion into a model brain in vitro and the formulation with lower swelling characteristics was chosen for the in vivo study. CH-coated or uncoated Pt electrode arrays were implanted into the brains of 14 rats, and their electrochemical performance was tested weekly for 8 weeks. Tissue response and neural survival was assessed histologically following electrode array removal. CH coating resulted in significantly lower voltage transient impedance, higher CIL, lower electrochemical impedance spectroscopy, and higher charge storage capacity compared to uncoated Pt electrodes in vivo, and this advantage was maintained over the 8-week implantation. There was no significant difference in evoked potential thresholds, signal-to-noise ratio, tissue response or neural survival between CH-coated and uncoated Pt groups. The significant electrochemical advantage and stability of CH coating in the brain supports the suitability of this coating technology for future development of smaller, higher fidelity electrode arrays with higher charge density requirement

    On extending actions of groups

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    Problems of dense and closed extension of actions of compact transformation groups are solved. The method developed in the paper is applied to problems of extension of equivariant maps and of construction of equivariant compactifications
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