Optimal scheduling of handoffs in cellular networks

The phenomenon of hard handoffs (as applicable to FDMA- and TDMA-based networks) as well as soft handoffs (as applicable to DS/CDMA-based networks) is formulated as stochastic optimization problems. The signals received by a mobile user are treated as stochastic processes with associated rewards, which are functions of some measurable characteristics of the received signals, while the handoff is associated with a switching penalty. This formulation captures the trade-offs involved in handoffs in a flexible manner and captures many facets of popular cellular communication systems in use currently. Using dynamic programming, necessary and sufficient conditions for determining the optimal base station(s) the mobile should be associated with during each decision epoch are derived. For the cases where the above-mentioned necessary and sufficient conditions fail to determine an optimal decision, “limited lookahead” arguments are used for determining handoff decisions. The decisions are taken in a decentralized manner, which makes its implementation easier compared to centralized algorithms. Simulation results show that for the hard handoffs, performance gain by the proposed algorithm over the simpler threshold algorithms proposed in the literature is small; however, for the case of soft handoffs, the proposed algorithm offers considerable improvement over the algorithm proposed in the IS-95 standard     

Computed tomographic findings in peritonsillar abscess and cellulitis

The differentiation of a peritonsillar abscess from peritonsillar cellulitis, although difficult on physical examination, is required in order to determine the appropriate treatment. Peritonsillar cellulitis can be treated with antibiotics alone, while a peritonsillar abscess should be drained. Computed tomography (CT) of the neck is often performed to identify the formation of a deep abscess in the neck, but is rarely used to diagnose peritonsillar infections. We report a patient in whom CT was a useful diagnostic tool for distinguishing peritonsillar abscess from peritonsillar cellulitis.     

Design and Synthesis of DDR1 Inhibitors with a Desired Pharmacophore Using Deep Generative Models

Discoidin domain receptor 1 (DDR1) inhibitors with a desired pharmacophore were designed using deep generative models (DGMs). DDR1 is a receptor tyrosine kinase activated by matrix collagens and implicated in diseases such as cancer, fibrosis and hypoxia. Herein we describe the synthesis and inhibitory activity of compounds generated from DGMs. Three compounds were found to have sub-micromolar inhibitory activity. The most potent of which, compound 3 (N-(4-chloro-3-((pyridin-3-yloxy)methyl)phenyl)-3-(trifluoromethyl)benzamide), had an IC₅₀ value of 92.5 nM. Furthermore, these compounds were predicted to interact with DDR1, which have a desired pharmacophore derived from a known DDR1 inhibitor. The results of synthesis and experiments indicated that our de novo design strategy is practical for hit identification and scaffold hopping.     

Evaluation of the implant type tissue-engineered cartilage by scanning acoustic microscopy

The tissue-engineered cartilages after implantation were nonuniform tissues which were mingling with biodegradable polymers, regeneration cartilage and others. It is a hard task to evaluate the biodegradation of polymers or the maturation of regenerated tissues in the transplants by the conventional examination. Otherwise, scanning acoustic microscopy (SAM) system specially developed to measure the tissue acoustic properties at a microscopic level. In this study, we examined acoustic properties of the tissue-engineered cartilage using SAM, and discuss the usefulness of this devise in the field of tissue engineering. We administered chondrocytes/atelocollagen mixture into the scaffolds of various polymers, and transplanted the constructs in the subcutaneous areas of nude mice for 2 months. We harvested them and examined the sound speed and the attenuation in the section of each construct by the SAM. As the results, images mapping the sound speed exhibited homogenous patterns mainly colored in blue, in all the tissue-engineered cartilage constructs. Contrarily, the images of the attenuation by SAM showed the variation of color ranged between blue and red. The low attenuation area colored in red, which meant hard materials, were corresponding to the polymer remnant in the toluidine blue images. The localizations of blue were almost similar with the metachromatic areas in the histology. In conclusion, the SAM is regarded as a useful tool to provide the information on acoustic properties and their localizations in the transplants that consist of heterogeneous tissues with various components.     

Direct demodulation of a 10.6µm FM signal with an NH2D stark cell

A new technique for direct demodulation of a 10.6-μm FM signal using a Stark absorption cell is described. A Stark tunable absorption line in NH2D is used to track the time-varying frequency of the incoming FM laser signal using a closed servo loop. The demodulated FM signal is proportional to the feedback voltage applied to the Stark cell. Demodulation at frequencies up to 5 kHz has been demonstrated, the rate being limited only by the bandwidth of the available servo electronics.     

Strain-induced anodic dissolution of Cu single crystals—effects of specimen geometry and slip morphology

Specimen geometry with respect to slip deformation and slip morphology have been examined in a study of strain-induced anodic dissolution of Cu single crystals. It has been found that a sample, whose geometry leads to the largest exposure of fresh (111) slip planes onto the original surfaces, shows the largest anodic dissolution on straining. However, the amount and rate of dissolution are unaffected by slip morphology or dislocation density. It has been calculated that approximately seven layers of Cu atoms dissolve from the freshly formed active (111) planes until the planes become inactive.     

Stark-induced three-wave mixing in molecular gases--Part II: Experiment

The first observation of resonantly enhanced, dc-induced, three-wave mixing in a gas is presented. A CW CO2laser beam and microwave radiation at 4 GHz are mixed in a microwave Stark cell containing gaseous NH2D. A single new sideband, 4 GHz below the applied CO2laser frequency, is observed with the aid of a scanning Fabry-Perot interferometer. The dependence of the sideband signal on gas pressure, microwave frequency, applied dc field, and microwave power are presented and compared with theoretical predictions.     

Multi-armed bandits with switching penalties

The multi-armed bandit problem with switching penalties (switching cost and switching delays) is investigated. It is shown that under an optimal policy, decisions about the processor allocation need to be made only at stopping times that achieve an appropriate index, the well-known “Gittins index” or a “switching index” that is defined for switching cost and switching delays. An algorithm for the computation of the “switching index” is presented. Furthermore, sufficient conditions for optimality of allocation strategies, based on limited look-ahead techniques, are established. These conditions together with the above-mentioned feature of optimal scheduling policies simplify the search for an optimal allocation policy. For a special class of multi-armed bandits (scheduling of parallel queues with switching penalties and no arrivals), it is shown that the aforementioned property of optimal policies is sufficient to determine an optimal allocation strategy. In general, the determination of optimal allocation policies remains a difficult and challenging task     

Turbulent Boundary Layer over Symmetric Bodies with Rigid and Flexible Surfaces

This paper presents the results of an investigation concerning the development of a turbulent boundary layer over a 2D symmetrical aerofoil and a 3D axisymmetric body with rigid and flexible surfaces. The experimental work included detailed measurements of the mean velocity profiles, pressure distribution, and drag force. The thin shear layer equations were solved numerically using a modified turbulence model to obtain the characteristics of the turbulent boundary layer. The results of this study indicate a significant difference between the characteristics of flow over rigid surfaces and those of flow over flexible surfaces of the same geometry. The mean velocity of flow in the case of flexible surfaces is smaller than the corresponding velocity of flow in the case of a rigid surface for a major part of the boundary layer. The boundary layer thicknesses are consistently higher on flexible surfaces than those on the corresponding rigid surfaces. Furthermore, in the case of flexible surfaces, drag reduction was always observed. The amount of reduction was seen to be systematically dependent on the characteristics of the flexible surface.