60,331 research outputs found
Tate (co)homology via pinched complexes
For complexes of modules we study two new constructions, which we call the
pinched tensor product and the pinched Hom. They provide new methods for
computing Tate homology and Tate cohomology, which lead to conceptual proofs of
balancedness of Tate (co)homology for modules over associative rings.
Another application we consider is in local algebra. Under conditions of
vanishing of Tate (co)homology, the pinched tensor product of two minimal
complete resolutions yields a minimal complete resolution.Comment: Final version; 23 pp. To appear in Trans. Amer. Math. So
Development of a 200 W CW High Efficiency Traveling Wave Tube at 12 GHz
The design, development, and test results are reported for an experimental PPM focused, traveling-wave tube that produces 235 watts of CW RF power over 85 MHz centered at 12.080 GHz. The tube uses a coupled cavity RF circuit with a velocity taper for greater than 30 percent basic efficiency. Overall efficiency of 51 percent is achieved by means of a nine stage depressed collector designed at NASA Lewis Research Center. This collector is cooled by direct radiation to deep space
Recommended from our members
The Warburg Dance Movement Library-The WADAMO Library: A Validation Study
The Warburg Dance Movement Library is a validated set of 234 video clips of dance movements for empirical research in the fields of cognitive science and neuroscience of action perception, affect perception and neuroaesthetics. The library contains two categories of video clips of dance movement sequences. Of each pair, one version of the movement sequence is emotionally expressive (Clip a), while the other version of the same sequence (Clip b) is not expressive but as technically correct as the expressive version (Clip a). We sought to complement previous dance video stimuli libraries. Facial information, colour and music have been removed, and each clip has been faded in and out. We equalised stimulus length (6 seconds, 8 counts in dance theory), the dancers’ clothing and video background and included both male and female dancers, and we controlled for technical correctness of movement execution. The Warburg Dance Movement Library contains both contemporary and ballet movements. Two online surveys (N = 160) confirmed the classification into the two categories of expressivity. Four additional online surveys (N = 80) provided beauty and liking ratings for each clip. A correlation matrix illustrates all variables of this norming study (technical correctness, expressivity, beauty, liking, luminance, motion energy)
Myocardial Architecture and Patient Variability in Clinical Patterns of Atrial Fibrillation
Atrial fibrillation (AF) increases the risk of stroke by a factor of four to
five and is the most common abnormal heart rhythm. The progression of AF with
age, from short self-terminating episodes to persistence, varies between
individuals and is poorly understood. An inability to understand and predict
variation in AF progression has resulted in less patient-specific therapy.
Likewise, it has been a challenge to relate the microstructural features of
heart muscle tissue (myocardial architecture) with the emergent temporal
clinical patterns of AF. We use a simple model of activation wavefront
propagation on an anisotropic structure, mimicking heart muscle tissue, to show
how variation in AF behaviour arises naturally from microstructural differences
between individuals. We show that the stochastic nature of progressive
transversal uncoupling of muscle strands (e.g., due to fibrosis or gap
junctional remodelling), as occurs with age, results in variability in AF
episode onset time, frequency, duration, burden and progression between
individuals. This is consistent with clinical observations. The uncoupling of
muscle strands can cause critical architectural patterns in the myocardium.
These critical patterns anchor micro-re-entrant wavefronts and thereby trigger
AF. It is the number of local critical patterns of uncoupling as opposed to
global uncoupling that determines AF progression. This insight may eventually
lead to patient specific therapy when it becomes possible to observe the
cellular structure of a patient's heart.Comment: 5 pages, 4 figures. For supplementary materials please contact Kishan
A. Manani at [email protected]
ECONOMIC IMPACTS OF EPA'S MANURE APPLICATION REGULATIONS ON DAIRY FARMS IN THE SOUTHWEST REGION
We estimate that EPA's CAFO final rule on manure application would have different impacts on dairy farms in the region, assuming that the farms would maintain the same herd size and same crop production practices. Some farms in the region would be able to comply it on their current land base, but other would need to lease additional land for land application of manure. Less than 30 percent of those affected farms would have a lower farm income. Most of these affected farms could have no income reduction or a higher income as a result of reduced feed cost from expanding homegrown feed production.Environmental Economics and Policy,
Isotropic magnetometry with simultaneous excitation of orientation and alignment CPT resonances
Atomic magnetometers have very high absolute precision and sensitivity to
magnetic fields but suffer from a fundamental problem: the vectorial or
tensorial interaction of light with atoms leads to "dead zones", certain
orientations of magnetic field where the magnetometer loses its sensitivity. We
demonstrate a simple polarization modulation scheme that simultaneously creates
coherent population trapping (CPT) in orientation and alignment, thereby
eliminating dead zones. Using Rb in a 10 Torr buffer gas cell we measure
narrow, high-contrast CPT transparency peaks in all orientations and also show
absence of systematic effects associated with non-linear Zeeman splitting.Comment: 4 pages, 4 figure
Identification and evaluation of educational uses and users for the STS. Educational planning for utilization of space shuttle ED-PLUSS
A planning and feasibility study to identify and document a methodology needed to incorporate educational programs into future missions and operations of the space transportation system was conducted. Six tasks were identified and accomplished during the study. The task statements are as follows: (1) potential user identification, (2) a review of space education programs, (3) development of methodology for user involvement, (4) methods to encourage user awareness, (5) compilation of follow-on ideas, and (6) response to NASA questions. Specific recommendations for improving the educational coverage of space activities are provided
- …
