On the power efficiency of cooperative broadcast in dense wireless networks

A fundamental problem in large scale wireless networks is the energy efficient broadcast of source messages to the whole network. The energy consumption increases as the network size grows, and the optimization of broadcast efficiency becomes more important. In this paper, we study the optimal power allocation problem for cooperative broadcast in dense large-scale networks. In the considered cooperation protocol, a single source initiates the transmission and the rest of the nodes retransmit the source message if they have decoded it reliably. Each node is allocated an-orthogonal channel and the nodes improve their receive signal-to-noise ratio (SNR), hence the energy efficiency, by maximal-ratio combining the receptions of the same packet from different transmitters. We assume that the decoding of the source message is correct as long as the receive SNR exceeds a predetermined threshold. Under the optimal cooperative broadcasting, the transmission order (i.e., the schedule) and the transmission powers of the source and the relays are designed so that every node receives the source message reliably and the total power consumption is minimized. In general, finding the best scheduling in cooperative broadcast is known to be an NP-complete problem. In this paper, we show that the optimal scheduling problem can be solved for dense networks, which we approximate as a continuum of nodes. Under the continuum model, we derive the optimal scheduling and the optimal power density. Furthermore, we propose low-complexity, distributed and power efficient broadcasting schemes and compare their power consumptions with those-of-a traditional noncooperative multihop transmission     

Role of mitochondria in the switch mechanism of the cell death mode from apoptosis to necrosis--studies on rho0 cells

Detailed mechanisms of the switch of the cell death mode from apoptosis to necrosis remain to be solved, although the intracellular level of ATP and that of free radicals have been postulated to be the major factors involved in the mechanisms. In the present study menadione (MEN)-induced cell injury processes were studied using rho0 cells derived from human osteosarcoma 143B cells and parental rho+ cells co-treated with inhibitors of electron transfer chain of mitochondria or oligomycin, an inhibitor of ATP synthesis. Treatment of rho+ cells with 100 microM MEN induced apoptosis, which reached the maximum at 6 h, and was followed by an abrupt decrease thereafter, while necrotic cells (NC) increased continuously when they were judged by Annexin V and PI double staining. On the other hand, MEN induced apoptotic and necrotic changes much faster in rho0 cells compared to rho+ cells. The frequency to find apoptotic cells (AP) in the former cells was distinctly smaller than that to find NC judged by Annexin V and PI double staining. Electron microscopically, a major population of rho0 cells treated with MEN for 6 h consisted of intermediate cells, and a small number of AP co-existed. At 9 h of the treatment intermediate cells were exclusively seen, and AP were hardly detected. When parental rho+ cells were treated with MEN in the presence of oligomycin or oligomycin plus antimycin A both apoptotic and necrotic changes of the cells were distinctly accelerated. The intracellular level of superoxide in rho0 cells continuously increased after the MEN treatment, whereas that of ATP remained distinctly low before and after the MEN treatment compared to that in rho+ cells. These data suggest that the intracellular level of superoxide may be a key factor controlling the switch from apoptosis to necrosis.     

复合敏化乳化炸药爆速研究

通过对大量测试数据的整理和分析讨论,得出玻璃微球与气泡复合敏化的乳化炸药爆速与炸药密度、敏化剂含量等因素的关系。由显著性分析可知,复合敏化剂中的任何一种组分都对乳化炸药的爆速有显著影响。     

Reduced adipose 18∶3ω3 with weight loss by very low calorie dieting

The human undergoing rapid and sustained weight loss by very low calorie dieting (VLCD) derives the majority of daily energy needs from adipose fatty acids. To evaluate the rates of metabolic utilization of individual fatty acids in humans, two groups of adult women outpatients were studied during major weight loss by VLCD. The diets used were either food or formula, providing the recommended dietary allowance for minerals and vitamins, with fat contents of 2–20 g/d. Group 1 consisted of 10 subjects [initial body mass index (BMI) 32.7, 157% of ideal body weight (IBW)] with a mean loss of 17.7 kg in 3–5 months. Group 2 consisted of 14 subjects (initial BMI 36.7, 167% of IBW) with a mean loss of 25.6 kg in 4–5 months. Adipose tissue biopsies were obtained by needle aspiration from Group 1 before and after weight loss and from Group 2 before, at the midpoint, and after weight loss. With weight loss in Group 1, the adipose tissue content of 18∶1ω9, 18∶2ω6, and 20∶4ω6 did not change, but 18∶3ω3 fell (0.67 to 0.56 wt%, p<0.0001) as did 20∶5ω3 (0.08 to 0.05, p<0.01). Adipose tissue 22∶6ω3 rose from 0.03 to 0.07 (p<0.01). In Group 2, only 18∶3ω3 showed a change, falling from 0.71 to 0.69 to 0.59 wt% across weight loss (p=0.03 by analysis of variance). We conclude that the major fatty acids are oxidized in proportion to their composition in adipose triglyceride. The significant reduction in the concentration of 18∶3ω3 during weight loss is unique among fatty acids. Its accelerated removal from adipose tissue indicates either a preferential step in β-oxidation or a defined need during supplemented fasting which exceeds its rate of provision from adipose stores. This work was presented in part at the Annual Meeting of the American Society for Clinical Nutrition, Washington, D.C., 1988.     

Polyesters containing sulfur. I. Products of melt polycondensation of diphenylmethane-4,4′-di(methylthioacetic acid) with some diols

Several new polyesters containing sulfur in the main chain were obtained by melt polycondensation of diphenylmethane-4,4′-di(methylthioacetic acid) with ethanediol, 1,3-propane diol, 1,4-butanediol, 1,5-pentenediol, 1,6-hexanediol, 1,2-propanediol, and 2,2′-oxydiethanol. The structure of all polyesters was determined from elemental analysis and infrared (IR) spectra. Yield, reduced viscosity, molecular weight, and softening temperature for reaction products have been found. Initial decomposition and initial intensive decomposition temperature were defined from the curves of thermogravimetric analysis.     

A two‐phase combined QoS‐based handoff scheme in a wireless ATM network

We describe the QoS‐based rerouting algorithm that is designed to implement a two‐phase inter‐switch handoff scheme for wireless ATM networks. We propose to use path extension for each inter‐switch handoff, and invoke path optimization when the handoff path exceeds the delay constraint or maximum path extension hops constraint. We study three types of path optimization schemes: combined QoS‐based, delay‐based and hop based path rerouting schemes. Copyright © 2001 John Wiley & Sons, Ltd.     

Development of Synthetic Platelet‐Activating Hydrogel Matrices to Induce Local Hemostasis

Several hemostatic strategies rely on the use of blood components such as fibrinogen and thrombin, which suffer from high cost and short shelf‐life. Here, a cost‐effective synthetic biomaterial is developed for rapid local hemostasis. Instead of using thrombin, thrombin‐receptor‐agonist‐peptide‐6 (TRAP6) is covalently engineered in polyvinyl alcohol (PVA) hydrogels. Soluble PVA‐TRAP6 is first prepared by covalent attachment of cysteine‐containing TRAP6 onto the backbone of PVA‐norbornenes (PVA‐NB) through photoconjugation. Cytotoxicity studies using C2C12 myoblasts indicate that PVA‐NB and PVA‐TRAP6 are nontoxic. Thromboelastography reveals that hemostatic activity of TRAP6 is retained in conjugated form, which is comparable to free TRAP6 solutions with equal concentrations. A 0.1% PVA‐TRAP6 solution can shorten the clotting time (CT) to ca. 45% of the physiological CT. High platelet‐activating efficiency is further confirmed by platelet aggregation assay and flow cytometry (FACS). For potential clinical applications, TRAP6‐presenting hydrogel particulates (PVA‐TRAP6‐P) are developed for local platelet activation and hemostasis. PVA‐TRAP6‐P is prepared by biofunctionalization of photopolymerized PVA‐NB hydrogel particulates (PVA‐NB‐P) with TRAP6. It is demonstrated that PVA‐TRAP6‐P can effectively shorten the CT to ca. 50%. FACS shows that PVA‐TRAP6‐P can activate platelets to a comparable extent as soluble TRAP6 control. Altogether, PVA‐TRAP6‐P represents a promising class of biomaterials for safe hemostasis and wound healing.     

Suppressed Lattice Disorder for Large Emission Enhancement and Structural Robustness in Hybrid Lead Iodide Perovskite Discovered by High-Pressure Isotope Effect

The soft nature of organic–inorganic halide perovskites renders their lattice particularly tunable to external stimuli such as pressure, undoubtedly offering an effective way to modify their structure for extraordinary optoelectronic properties. Here, using the methylammonium lead iodide as a representative exploratory platform, it is observed that the pressure-driven lattice disorder can be significantly suppressed via hydrogen isotope effect, which is crucial for better optical and mechanical properties previously unattainable. By a comprehensive in situ neutron/synchrotron-based analysis and optical characterizations, a remarkable photoluminescence (PL) enhancement by threefold is convinced in deuterated CD₃ND₃PbI₃, which also shows much greater structural robustness with retainable PL after high peak-pressure compression–decompression cycle. With the first-principles calculations, an atomic level understanding of the strong correlation among the organic sublattice and lead iodide octahedral framework and structural photonics is proposed, where the less dynamic CD₃ND₃⁺ cations are vital to maintain the long-range crystalline order through steric and Coulombic interactions. These results also show that CD₃ND₃PbI₃-based solar cell has comparable photovoltaic performance as CH₃NH₃PbI₃-based device but exhibits considerably slower degradation behavior, thus representing a paradigm by suggesting isotope-functionalized perovskite materials for better materials-by-design and more stable photovoltaic application.     

Dielectric–Semiconductor Interface Limits Charge Carrier Motion at Elevated Temperatures and Large Carrier Densities in a High‐Mobility Organic Semiconductor

The fundamental nature of charge transport in highly ordered organic semiconductors is under constant debate. At cryogenic temperatures, effects within the semiconductor such as traps or the interaction of charge carriers with the insulating substrate (dipolar disorder or Fröhlich polarons) are known to limit carrier motion. In comparison, at elevated temperatures, where charge carrier mobility often also decreases as function of temperature, phonon scattering or dynamic disorder are frequently discussed mechanisms, but the exact microscopic cause that limits carrier motion is debated. Here, the mobility in the temperature range between 200 and 420 K as function of carrier density is explored in highly ordered perylene‐diimide from 3 to 9 nm thin films. It is observed that above room temperature increasing the gate electric field or decreasing the semiconducting film thickness leads to a suppression of the charge carrier mobility. Via X‐ray diffraction measurements at various temperatures and electric fields, changes of the thin film structure are excluded as cause for the observed mobility decrease. The experimental findings point toward scattering sites or traps at the semiconductor–dielectric interface, or in the dielectric as limiting factor for carrier mobility, whose role is usually neglected at elevated temperatures.     

A Roadmap for Controlled and Efficient n‐Type Doping of Self‐Assisted GaAs Nanowires Grown by Molecular Beam Epitaxy

N‐type doping of GaAs nanowires has proven to be difficult because the amphoteric character of silicon impurities is enhanced by the nanowire growth mechanism and growth conditions. The controllable growth of n‐type GaAs nanowires with carrier density as high as 10²⁰ electron cm^?3 by self‐assisted molecular beam epitaxy using Te donors is demonstrated here. Carrier density and electron mobility of highly doped nanowires are extracted through a combination of transport measurement and Kelvin probe force microscopy analysis in single‐wire field‐effect devices. Low‐temperature photoluminescence is used to characterize the Te‐doped nanowires over several orders of magnitude of the impurity concentration. The combined use of those techniques allows the precise definition of the growth conditions required for effective Te incorporation.