486 research outputs found

    Spacecraft control/flexible structures interaction study

    Get PDF
    An initial study to begin development of a flight experiment to measure spacecraft control/flexible structure interactions was completed. The approach consisted of developing the equations of motion for a vehicle possessing a flexible solar array, then linearizing about some nominal motion of the craft. A set of solutions is assumed for array deflection using a continuous normal mode method and important parameters are identified. Interrelationships between these parameters, measurement techniques, and input requirements are discussed which assure minimization of special vehicle maneuvers and optimization of data to be obtained during the normal flight sequence. Limited consideration is given to flight data retrieval and processing techniques as correlated with the requirements imposed by the measurement system. Results indicate that inflight measurement of the bending and torsional mode shapes and respective frequencies, and damping ratios, is necessary. Other parameters may be measured from design data

    Determination of critical nondimensional parameters in aircraft dynamic response to random input

    Get PDF
    The critical parameters of subsonic jet aircraft response in a random atmospheric environment are determined. Equations of motion are presented for semirigid aircraft with a flexible primary airfoil. However, the analysis is easily extendable to include additional appendage flexibility. The analysis establishes the mechanical admittance values for pitching, plunging, and the first mode effects from wing elastic bending and torsion. Nondimensional parameters are established which allow the representation of all subsonic jet transport aircraft with one nondimensional model. The critical parameters for random forcing are found to be aircraft relative mass, reduced natural and forcing frequencies, and Mach number. Turbulence scale lengths are found to be directly related to the critical values of reduced forcing frequency. Results are given for subsonic craft traveling at constant altitude. Specific values of admittance functions are tabulated at Mach numbers of 0.2, 0.5, and 0.7. The relative mass range covers all aircraft currently in operation

    Voyager Observations of Anomalous and Galactic Cosmic Rays During 1998

    Get PDF
    We present energy spectra of anomalous and galactic cosmic rays over a wide energy range by combining data from the Low Energy Charged Particle experiment and the Cosmic Ray experiment on the Voyager spacecraft. The data set covers all of 1998. We compare energy spectra obtained from Voyagers 1 and 2. The energy range covered contains the peak intensity in the spectra for anomalous cosmic ray hydrogen, helium, and oxygen. The spectra presented can be used to constrain models of solar modulation

    ЭЭГ БИОУПРАВЛЕНИЕ УЛУЧШАЕТ СФОКУСИРОВАННОЕ ВНИМАНИЕ ПРИ СИНДРОМЕ ДЕФИЦИТА ВНИМАНИЯ И ГИПЕРАКТИВНОСТИ

    Get PDF
    EEG biofeedback (so called neurofeedback) is considered as an efficacious treatment for ADHD. We propose that operant conditioning of EEG in neurofeedback training mode, aimed to mitigate inattention and low arousal in ADHD, will be accompanied by changes in EEG bands' relative power. Patients were 18 children diagnosed with ADHD. The neurofeedback protocol (“Focus/Alertness” by Peak Achievement Trainer, Neurotek, KY) used to train patients has focused attention training procedure, which according to specifications, represents wide band EEG amplitude suppression training. Quantitative EEG analysis was completed on each of 25 min long twelve sessions to determine the relative power of each of the EEG bands of interest throughout each session, and from the first session to the last session. Additional statistical analysis was performed to determine significant changes in relative power within sessions (from minute 1 to minute 25), and between sessions (from session 1 to session 12) for an individual patient. We performed analysis of relative power of Theta, Alpha, Low and High Beta, Theta/Alpha, Theta/Beta, and Theta/Low Beta and Theta/High Beta ratios. We performed also analysis between the “Focus”measure and changes in relative power of above EEG rhythms and their ratios. Additional secondary measures of patients’ post-neurofeedback outcomes were assessed using an audio-visual selective attention test (IVA + Plus) and behavioral evaluation scores from Aberrant Behavior Checklist. We found that, as expected, Theta/Low Beta and Theta/Alpha ratios decreased significantly from Session 1 to Session 12 and from minute 1 to minute 25 within sessions. The ‘Focus” measure of protocol showed high negative correlation with both Theta/Alpha and Theta/Beta ratios. The findings regarding EEG changes resulting from self-regulation training along with behavioral evaluations will help in elucidation of neural mechanisms of neurofeedback aimed to improve focused attention and alertness in ADHD.Электроэнцефалографическое биоуправление, или нейробиоуправление, – эффективная технология при лечении синдрома дефицита внимания и гиперактивности (СДВГ). Предполагалось, что оперантное обусловливание электроэнцефалографии (ЭЭГ) в тренинге нейробиоуправления, направленном на снижение невнимательности и низкой активности детей с СДВГ, будет сопровождаться изменениями относительной мощности в разных ЭЭГ-частотных диапазонах. Пациентами были 18 детей с диагнозом «синдром дефицита внимания и гиперактивности». Протокол нейробиоуправления (Focus/Alertness, Peak Achievement Trainer, Neurotek, KY), используемый для тренинга, включал обучающие процедуры фокусировки внимания, которые, согласно спецификации, представляли собой интерактивные процедуры, направленные на подавление амплитуды в широком ЭЭГ-диапазоне. Количественный анализ ЭЭГ был проведен для двенадцати 25-минутных сессий, чтобы определить относительную мощность каждого из интересующих частотных диапазонов ЭЭГ в ходе каждой сессии, а также с первой по последнюю сессию. Проведен дополнительный статистический анализ определения значимых изменений относительной мощности внутри сессии (от 1-й до 25-й мин) и в период между сессиями (от 1-й до 12-й мин) для конкретного пациента. Проанализированы относительная мощность в диапазонах тета, альфа, низкочастотного и высокочастотного бета, а также их соотношений: тета/альфа, тета/бета, тета/низкочастотный бета и тета/высокочастотный бета. Сравнивались динамика показателя «фокус» и изменения относительной мощности вышеперечисленных ритмов ЭЭГ и их соотношений.Дополнительные повторные измерения результатов нейробиоуправления у пациентов оценивались с использованием аудиовизуального теста селективного внимания (IVA + Plus) и поведенческих оценок из опросника Aberrant Behavior Checklist. Как и ожидалось, соотношения диапазонов тета/низкочастотный бета и тета/альфа значимо снижались с 1-й до 12-й сессии и с 1-й до 25-й мин внутри сессии. Показатель «фокус» в протоколе обнаружил высокую отрицательную корреляцию как с тета/альфа-, так и с тета/бета-коэффициентами. Полученные результаты, касающиеся изменений ЭЭГ вследствие обучения саморегуляции, наряду с поведенческими оценками могут способствовать выяснению нейрональных механизмов нейробиоуправления, направленных на увеличение фокусировки внимания и активности при СДВГ

    Molecular Sequence of Events and Signaling Pathways in Cerebral Metastases

    Get PDF
    Brain metastases are the leading cause of morbidity and mortality among cancer patients, and are reported to occur in about 40% of cancer patients with metastatic disease in the United States of America. Primary tumor cells appear to detach from the parent tumor site, migrate, survive and pass through the blood brain barrier in order to establish cerebral metastases. This complex process involves distinct molecular and genetic mechanisms that mediate metastasis from these primary organs to the brain. Furthermore, an interaction between the invading cells and cerebral milieu is shown to promote this process as well. Here, we review the mechanisms by which primary cancer cells metastasize to the brain via a mechanism called epithelial-to-mesenchymal transition, as well as the involvement of certain microRNA and genetic aberrations implicated in cerebral metastases from the lung, breast, skin, kidney and colon. While the mechanisms governing the development of brain metastases remain a major hindrance in treatment, understanding and identification of the aforementioned molecular pathways may allow for improved management and discovery of novel therapeutic targets

    Funerary Artifacts, Social Status, and Atherosclerosis in Ancient Peruvian Mummy Bundles

    Get PDF
    Background: Evidence of atherosclerotic plaques in ancient populations has led to the reconsideration of risk factors for heart disease and of the common belief that it is a disease of modern times. Methods: Fifty-one wrapped mummy bundles excavated from the sites of Huallamarca, Pedreros, and Rinconada La Molina from the Puruchuco Museum collection in Lima, Peru, were scanned using computed tomography to investigate the presence of atherosclerosis. Funerary artifacts contained within the undisturbed mummy bundles were analyzed as an attempt to infer the social status of the individuals to correlate social status with evidence of heart disease in this ancient Peruvian group. This work also provides an inventory of the museum mummy collection to guide and facilitate future research. Results: Statistical analysis concluded that there is little association between the types of grave goods contained within the bundles when the groups are pooled together. However, some patterns of artifact type, material, atherosclerosis, and sex emerge when the 3 excavation sites are analyzed separately. Conclusions: From the current sample, it would seem that social class is difficult to discern, but those from Huallamarca have the most markers of elite status. We had hypothesized that higher-status individuals may have had lifestyles that would place them at a higher risk for atherogenesis. There seems to be some indication of this within the site of Huallamarca, but it is inconclusive in the other 2 archeological sites. It is possible that a larger sample size in the future could reveal more statistically significant results

    Is there a role for menopausal hormone therapy in the management of postmenopausal osteoporosis?

    Get PDF
    We provide an evidence base and guidance for the use of menopausal hormone therapy (MHT) for the maintenance of skeletal health and prevention of future fractures in recently menopausal women. Despite controversy over associated side effects, which has limited its use in recent decades, the potential role for MHT soon after menopause in the management of postmenopausal osteoporosis is increasingly recognized. We present a narrative review of the benefits versus risks of using MHT in the management of postmenopausal osteoporosis. Current literature suggests robust anti-fracture efficacy of MHT in patients unselected for low BMD, regardless of concomitant use with progestogens, but with limited evidence of persisting skeletal benefits following cessation of therapy. Side effects include cardiovascular events, thromboembolic disease, stroke and breast cancer, but the benefit-risk profile differs according to the use of opposed versus unopposed oestrogens, type of oestrogen/progestogen, dose and route of delivery and, for cardiovascular events, timing of MHT use. Overall, the benefit-risk profile supports MHT treatment in women who have recently (< 10 years) become menopausal, who have menopausal symptoms and who are less than 60 years old, with a low baseline risk for adverse events. MHT should be considered as an option for the maintenance of skeletal health in women, specifically as an additional benefit in the context of treatment of menopausal symptoms, when commenced at the menopause, or shortly thereafter, in the context of a personalized benefit-risk evaluation

    Apolipoprotein-ε4 is Associated with Higher Fecundity in a Natural Fertility Population

    Get PDF
    In many populations, the apolipoprotein-ε4 (APOE-ε4) allele increases the risk for several chronic diseases of aging, including dementia and cardiovascular disease; despite these harmful effects at later ages, the APOE-ε4 allele remains prevalent. We assess the impact of APOE-ε4 on fertility and its proximate determinants (age at first reproduction, interbirth interval) among the Tsimane, a natural fertility population of forager-horticulturalists. Among 795 women aged 13 to 90 (20% APOE-ε4 carriers), those with at least one APOE-ε4 allele had 0.3 to 0.5 more children than (ε3/ε3) homozygotes, while those with two APOE-ε4 alleles gave birth to 1.4 to 2.1 more children. APOE-ε4 carriers achieve higher fertility by beginning reproduction 0.8 years earlier and having a 0.23-year shorter interbirth interval. Our findings add to a growing body of literature suggesting a need for studies of populations living in ancestrally relevant environments to assess how alleles that are deleterious in sedentary urban environments may have been maintained by selection throughout human evolutionary history
    corecore