System requirements for Ka-band Earth-satellite propagation data

Accurate estimates of the propagation impairments that affect link quality and availability and determine signal interference fields are essential for the reliable design of telecommunication systems and the efficient use of the electromagnetic spectrum. Recent announcements by commercial entities of their intent to use Ka-band spectrum to supply satellite services have heightened interest in propagation data and models for these frequencies. This paper provides a brief overview of Ka-band Earth-satellite systems and requirements in relation to the need for specific types of propagation data     

A 2.2 W, 80 MHz superscalar RISC microprocessor

A 28 mW/MHz at 80 MHz structured-custom RISC microprocessor design is described. This 32-b implementation of the PowerPC architecture is fabricated in a 3.3 V, 0.5 μm, 4-level metal CMOS technology, resulting in 1.6 million transistors in a 7.4 mm by 11.5 mm chip size. Dual 8-kilobyte instruction and data caches coupled to a high performance 32/64-b system bus and separate execution units (float, integer, loadstore, and system units) result in peak instruction rates of three instructions per clock cycle. Low-power design techniques are used throughout the entire design, including dynamically powered down execution units. Typical power dissipation is kept under 2.2 W at 80 MHz. Three distinct levels of software-programmable, static, low-power operation-for system power management are offered, resulting in standby power dissipation from 2 mW to 350 mW. CPU to bus clock ratios of 1×, 2×, 3×, and 4× are implemented to allow control of system power while maintaining processor performance. As a result, workstation level performance is packed into a low-power, low-cost design ideal for notebooks and desktop computers     

How disorder can diminish avalanche risks: effect of size distribution

We study the behavior of disk assemblies with a variable disorder distribution. The packing is first consolidated and then continuously tilted very slowly. The amount of displaced disks for each tilted angle is recorded. Large displacements of the disks can occur due to some local or global mechanical instabilities. The definition of neighboring disks is based on radical (extension of Voronoï) tessellation rules to decompose, in a unique and perfectly defined manner, the two-dimensional space for polydisperse disks. In this way, by comparing the characteristics of stability for one disk to the neighboring ones for local ordered cluster, we can predict the global amount of displaced disks. Some tilting cycles have been performed to check the correlation between the instability of the packing structure (collective displacements) with micro and macro order parameters.     

Ecological vulnerability analysis: A river basin case study

Assessing and quantifying ecosystem vulnerability is a key issue in site-specific ecotoxicological risk assessment. In this paper, the concept of vulnerability, particularly referred to aquatic ecosystems is defined. Sensitivity to stressors, susceptibility for exposure and recovery capability are described as component of vulnerability of biological communities. The potential for habitat changes must also be considered in ecosystem vulnerability assessment. A procedure based on the application of an ecosystem vulnerability index is proposed. The method allows the assessment of vulnerability of riverine ecosystems to multiple stressors. The procedure is applied to two river systems in northern Italy: River Serio, subject to strong human pressure, and River Trebbia, in semi-natural conditions, as reference system. Macrozoobenthos is chosen as the indicator community. The actual quality of River Serio was evaluated as the result of the multiple stressor pressure on the reference system. Values and limitations of the approach are discussed.     

Effects of Pre- and Postharvest Chitosan Treatments to Control Storage Grey Mold of Table Grapes

ABSTRACT: The effectiveness of pre- and postharvest treatments with chitosan (0.1, 0.5, and 1.0%) to control Botrytis cinerea on table grapes was investigated. In postharvest treatments, small bunches dipped in chitosan solutions and inoculated with the pathogen showed a reduction of incidence, severity, and nesting of grey mold, in comparison with the control. Single berries artificially wounded, treated with the polymer, and inoculated with B. cinerea showed a reduced percentage of infected berries and lesion dia. Higher chitosan concentrations demonstrated greater decay reduction. All preharvest treatments significantly reduced the incidence of grey mold, as compared to the control. Table grapes treated with 1.0% chitosan showed a significant increase of phenylalanine ammonia-lyase (PAL) activity. Consequently, besides a direct activity against B. cinerea , chitosan produces other effects contributing to reduce decay.     

Creating gold nanoprisms directly on quartz crystal microbalance electrodes for mercury vapor sensing

A novel electrochemical route is used to form highly {111}-oriented and size-controlled Au nanoprisms directly onto the electrodes of quartz crystal microbalances (QCMs) which are subsequently used as mercury vapor sensors. The Au nanoprism loaded QCM sensors exhibited excellent response-concentration linearity with a response enhancement of up to ～ 800% over a non-modified sensor at an operating temperature of 28?°C. The increased surface area and atomic-scale features (step/defect sites) introduced during the growth of nanoprisms are thought to play a significant role in enhancing the sensing properties of the Au nanoprisms toward Hg vapor. The sensors are shown to have excellent Hg sensing capabilities in the concentration range of 0.123-1.27 ppm(v) (1.02-10.55 mg m(-3)), with a detection limit of 2.4 ppb(v) (0.02 mg m(-3)) toward Hg vapor when operating at 28?°C, and 17 ppb(v) (0.15 mg m(-3)) at 89?°C, making them potentially useful for air monitoring applications or for monitoring the efficiency of Hg emission control systems in industries such as mining and waste incineration. The developed sensors exhibited excellent reversible behavior (sensor recovery) within 1 h periods, and crucially were also observed to have high selectivity toward Hg vapor in the presence of ethanol, ammonia and humidity, and excellent long-term stability over a 33 day operating period.     

Propagation considerations for emerging satellite communicationsapplications

The effects of rain and other propagation concerns for new applications areas, currently in operation or planned for implementation by the end of this decade, are described. The areas include: VSAT systems employing low operating margins and/or low elevation angles; traditional communications applications operating with inclined geosynchronous orbits; and mobile and personal communications applications employing networks of low earth orbit (LEO) satellites. Prediction modeling and analysis techniques applicable to these areas are described. Analytical results for a range of operational parameters involving low-margin, low elevation angle, inclined geosynchronous, and LEO systems are presented     

Acute acalculous cholecystitis associated with common hepatic duct obstruction: a variant of Mirizzi's syndrome

A variation of Mirizzi's syndrome is described in which common hepatic duct obstruction occurs due to extrinsic compression by an acutely inflamed acalculous gallbladder abutting the common hepatic duct. This case suggests that extrinsic compression and inflammation in the absence of stones can result in complete obstruction of extrahepatic biliary flow.