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151.
This paper describes the DTX-240D digital circuit multiplication system (DCMS) offered by ECI Telecom. It will accept up to 240 × 64 kb/s trunks carrying either 64 kb/s voice, voice band analogue non-speech signals, or digital data for transmission over a 2·048 Mb/s digital link. Over 1000 are currently ‘on-line’ and carrying traffic. The system comprises a pair of terminals, one on each side of the interterminal digital link (bearer). It will normally operate in the network at a concentration ratio of 5:1, in which case 150 × 64 kb/s trunks, carrying voice, voice band data or digital data can be concentrated into one 2·048 Mb/s bearer. The users are able to increase the number of trunks up to 240 per 2·048 Mb/s bearer, when time zone differences cause a spread of busy-hour traffic carried on a single system. Each terminal will normally be located at an international switching centre (ISC) but may also be located at an earth-station. The system uses a DSI (digital speech interpolation) stage providing a 2·5:1 multiplication, followed by an additional 2:1 multiplication by means of ADPCM (adaptive differential pulse code modulation). In addition, the VBR (variable bit rate) technique is used to prevent clipping, due to overload congestion. The system can also be used with 1·544 Mb/s digital bit streams (trunk side or bearer). 相似文献
152.
Mobile Commerce: Framework,Applications and Networking Support 总被引:16,自引:2,他引:14
Advances in e-commerce have resulted in significant progress towards strategies, requirements, and development of e-commerce applications. However, nearly all e-commerce applications envisioned and developed so far assume fixed or stationary users with wired infrastructure. We envision many new e-commerce applications that will be possible and significantly benefit from emerging wireless and mobile networks. To allow designers, developers, and researchers to strategize and create mobile commerce applications, we propose a four-level integrated framework for mobile commerce. Since there are potentially an unlimited number of mobile commerce applications, we attempt to identify several important classes of applications such as mobile financial applications, mobile inventory management, proactive service management, product location and search, and wireless re-engineering. We discuss how to successfully define, architect, and implement the necessary hardware/software infrastructure in support of mobile commerce. Also, to make mobile commerce applications a reality, we address networking requirements, discuss support from wireless carriers, and present some open research problems. 相似文献
153.
Yung-Sheng Huang Dave E. Mills Ron P. Ward David F. Horrobin Valerie A. Simmons 《Lipids》1989,24(7):565-571
Weanling male spontaneously hypertensive (SHR) and normotensive (WKY) rats were maintained on a fat-free semisynthetic diet
and killed at various intervals. The effects of fat-depletion on the appearance of essential fatty acid (EFA) deficiency symptoms,
the progressive changes of major fatty acids in plasma, liver, heart, and kidney phospholipids (PL), and in skin total lipids
were compared between these two strains. After five weeks on the diet, the slower growth and the appearance of EFA deficiency
symptoms became evident in SHR. In general, fat-depletion reduced the levels of n−6 fatty acids, whereas it increased those
of 20∶3n−9. However, the fat-depletion induced reduction of 18∶2n−6 in heart PL and 20∶4n−6 in kidney, while the elevation
of 20∶3n−9 in plasma, heart, and kidney PL were greater in WKY than in SHR. As a result, the elevation of biochemical EFA
deficiency index—20∶3n−9/20∶4n−6 ratio—was greater in WKY than in SHR. In comparison with WKY, the concentrations of liver
triacylglycerols and the weights of adipose tissues in SHR were reduced to a greater extent, indicating an active catabolism
of triacylglycerols in SHR. This study suggests that the earlier appearance of morphological symptoms of EFA deficiency in
SHR was not associated with the reducing n−6 EFA levels or with an elevation of triene/tetraene ratio, but possibly to a reduced
supply of n−6 EFA for skin prostaglandin synthesis. 相似文献
154.
Toine F H Bovee Gerrit Bor Henri H Heskamp Ron L A P Hoogenboom Michel W F Nielen 《Food Additives & Contaminants》2006,23(6):556-568
Previously we described the construction and properties of a rapid yeast bioassay stably expressing human estrogen receptor alpha (hERalpha) and yeast enhanced green fluorescent protein (yEGFP), the latter in response to estrogens. In the present study this yeast estrogen assay was validated as a qualitative screening method for the determination of estrogenic activity in animal feed. This validation was performed according to EC Decision 2002/657. Twenty blank animal feed samples, including milk replacers and wet and dry feed samples, were spiked with 17beta-estradiol (E2beta) at 5 ng g(-1), 17alpha-ethynylestradiol (EE2) at 5 ng g(-1), diethylstilbestrol (DES) at 10 ng g(-1), zearalenone at 1.25 microg g(-1) or equal at 200 microg g(-1). All of these blank and low estrogen spiked feed samples fulfilled the CCalpha and CCbeta criterions, meaning that all 20 blank feed samples gave a signal below the determined decision limit CCalpha and were thus classified as compliant, and at least 19 out of the 20 spiked samples gave a signal above this CCalpha (beta = 5%) and were thus classified as suspect. The method was specific and estrogens in feed were stable for up to 98 days. In this study we also present long-term performance data and several examples of estrogens found in the routine screening of animal feed. This is the first successful example of a developed, validated and applied bioassay for the screening of hormonal substances in feed. 相似文献
155.
156.
能源话题主导了2005年的新闻,紧跟着这些热点新闻报道之后而来的,是猛增的风险投资。分析风险投资进入的力度以及领域可以把握未来清洁能源领域发展的趋势。[编按] 相似文献
157.
The forthcoming introduction of lower standards for arsenic in drinking water requires new technologies for arsenic removal. We report the development of an electrochemical unit for remediating domestic water supplies for homes without municipally treated water. Electrolysis in a two‐anode system provides oxidants to convert As(III) to As(V) in situ, and a sacrificial anode to deliver iron into solution. Conditioning tanks after each electrolysis step ensure completion of the chemical reactions. At the pH of domestic water, As(V) co‐precipitates with Fe(OH)3; subsequent filtration leaves <10 ppb of inorganic arsenic in solution. 相似文献
158.
Galia Lavi Charles A. Dinarello Ron N. Apte Smadar Cohen 《Israel journal of chemistry》2005,45(4):457-464
A sustained delivery system for interleukin-1 receptor antagonist (IL-1Ra) may have great therapeutic and industrial potential due to the cytokine activity as an IL-1 inhibitor. Here, we investigated the capability of biodegradable polymeric microspheres to sustain the release and prolong the therapeutic efficacy of IL-1Ra. IL-1Ra was encapsulated within rapidly degrading poly(lactic/glycolic acid) PLGA RG502H microspheres, which showed a desirable release profile of IL-1Ra in vitro. Pharmacokinetic study in mice revealed elevated serum levels of the recombinant IL-1Ra (rIL-1Ra) for up to 8 days following subcutaneous injection of IL-1Ra microspheres. In comparison, the serum levels of rIL-1Ra following subcutaneous or intravenous bolus injection of the soluble cytokine decreased very rapidly; within 48 h no recombinant cytokine was detected in mice sera. The sustained delivery of rIL-1Ra for over two weeks was efficient in inhibiting IL-1ß-stimulated induction of serum IL-6. These results suggest that the present therapeutic protocol of daily bolus injections of the IL-1Ra may be replaced by a weekly injection of IL-1Ra within PLGA RG502H microspheres. 相似文献
159.
A new Data Link Layer protocol, named the Twin-Bus-Controller (TBC) protocol, is proposed for a fibre optic network with unidirectional bus topology. The TBC protocol operates on a contention-based, time-division multiplexing scheme, and is managed by two centralized bus controllers. These controllers, which also function as network managers cooperate with each other to control and coordinate the activities on the twin bus. The IBC protocol has the capability to perform at a very high network utilization, and uses simple hardware at all stations except the two bus controllers. This arrangement provides a relatively inexpensive means to accommodate a large number of stations. Heterogeneous data consisting of real-time sensor and control signals, voice and video data, and non-real-time data such as those due to accounting and administration, can be simultaneously handled by the TBC protocol. The TBC protocol maintains global queues for all different types of data, and each class of data has a bounded delay. Furthermore, any new type of data can be added easily to the network without shutting it down or affecting those stations that are unrelated to the new data. A finite-state-machine model has been used to describe the TBC protocol. Performance of the TBC protocol has been evaluated by statistical analysis as well as via simulation for multiple classes of data traffic. Performance of the TBC protocol has been compared with that of Buzznet and Fasnet. The TBC protocol can be directly applied to diverse computer communication systems, e.g. office, manufacturing, and banking environments. 相似文献
160.