382 research outputs found
Atiyah sequences and connections on principal bundles over Lie groupoids and differentiable stacks
No full textWe construct and study general and integrable connections on Lie groupoids and differentiable
stacks, as well as on principal bundles over them using an Atiyah exact sequence of vector
bundles associated to transversal tangential distributions
Hybrid Transceiver Design and Optimal Power Allocation for the Cognitive mmWave Multiuser MIMO Downlink Relying on Limited Feedback
No full textA hybrid transceiver architecture is conceived for a cognitive radio (CR) aided millimeter wave (mmWave) multiuser (MU) multiple-input multiple-output (MIMO) downlink system relying on multiple radio frequency (RF) chains both at the CR base station (CBS) and the secondary users (SUs). To begin with, a hybrid transceiver design algorithm is proposed for the CBS and SUs, to maximize the sum spectral efficiency (SE) by decoupling the hybrid transceiver into a blind minimum mean squared error (MMSE) receiver combiner (RC) and optimal-capacity two-stage hybrid transmit precoder (TPC) components. These RC-weights and TPC-weights are subsequently found by using the popular simultaneous orthogonal matching pursuit (SOMP) technique. A closed-form solution is derived for the optimal power allocation that maximizes the sum SE under the associated interference and transmit power constraints. To achieve user fairness, we also propose an optimal power allocation scheme for maximizing the geometric mean (GM) of the SU rates. Finally, a low-complexity limited feedback aided hybrid transceiver is designed, which relies on the random vector quantization (RVQ) technique. Our simulation results demonstrate that an improved SE is achieved in comparison to the state-of-the-art techniques
On the third and fourth Betti numbers of a homogeneous space of a Lie group
No full textIn the paper "The Second cohomology of nilpotent orbits in classical Lie
algebras, Kyoto J. Math. 60 (2020), no. 2, 717-799" by I. Biswas, P.
Chatterjee, and C. Maity, computable explicit descriptions of the second and
first cohomology groups of a general homogeneous space of a Lie group are
given, extending an earlier result in "On the exactness of Kostant-Kirillov
form and the second cohomology of nilpotent orbits, Internat. J. Math. 23
(2012), no. 8, 1250086" by I. Biswas and P. Chatterjee. They turned out to be
crucial in our computations related to the cohomology of nilpotent orbits, as
done in the above two papers. Here we describe the third and fourth
cohomologies of a general homogeneous space along the line mentioned above. We
also draw various consequences of our main results in numerous special
settings. In particular, we obtain an interesting invariant by showing that for
a large class of homogeneous spaces, the difference between the third and
fourth Betti numbers coincides with the difference in the numbers of simple
factors of the ambient group and the associated closed subgroup.Comment: 43 page
Bilateral inverse <i>Duane′s retraction syndrome</i>-A case report
No full textDuane′s retraction syndrome is a well known congenital musculo-facial anomaly. Various explanations have been given for the aetiology of this syndrome. Inverse Duane′s retraction syndrome is a condition with reverse clinical features. Abduction of the affected eye is possible to some extent and is accompanied by retraction of the eyeball, narrowing of the palpebral fissure and pseudoptosis. There may be some restriction of movement on adduction. The primary lesion is suspected to be in the medial rectus muscle. Frequently the muscle is found to be entrapped following trauma to the medial wall of the orbit. A case of bilateral inverse Duane′s retraction syndrome and convergent squint along with left-sided perceptive deafness is reported. As is usually the case there was no structural abnormality or entrapment of the muscle from trauma
Retinal detachment associated with thalassemia major and Marfan′s syndrome-A case report
No full textThe thalassaemias, unlike a few other disorders of the haemopoietic system, are very rarely accompanied by ophthalmological changed. Marfan′s Syndrome, on the other hand, exhibits a number of ocular manifestations 2. This article describes a case of uniocular retinal detachment associated with both these condition
Knowledge About HIV And AIDS Among Medical Entrants - A Questionnaire Study
No full textA close ended questionnaire study on knowledge attitude and practice (KAP) about HIV/AIDS was conducted amongst first year MBBS students immediately on joining the course. One hundred and fourteen students participated in the study. Overall level of knowledge about AIDS was found to be 72%. Boys were better informed about possible methods of prevention of AIDS than girls. Misconceptions regarding mode of transmission, clinical presentation and prevention existed amongst large number of them. Seventeen percent of boys and 5% of girls approved of pre-marital sex for boys while 14.8% of boys approved the same for girls. Thirteen and half percent of boys admitted sexual experience. Awareness programme should be intensified amongst students to improve the overall knowledge of AIDS
Single-event charge collection and upset in 65-nm and 40-nm dual- and triple-well bulk CMOS SRAMS
No full textCMOS technologies can be either dual-well or triple-well. Triple-well technology has several advantages compared to dual-well technology in terms of electrical performance. Differences in the ion-induced single-event response between these two technology options, however, are not well understood. This work presents a comparative analysis of heavy ion-induced upsets in dual-well and triple-well 40-nm CMOS SRAMs. Primary factors affecting the charge-collection mechanisms for a wide range of particle energies are investigated, showing that triple-well technologies are more vulnerable to low-LET particles, while dual-well technologies are more vulnerable to high-LET particles. For the triple-well technology, charge confinement and multiple-transistor charge collection triggers the “Single Event Upset Reversal” mechanism that reduces sensitivity at high LETs
Senescence of Staphylococci : metabolic and environmental factors determining bacterial survival and persistence
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