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51.
Lenzini L. Luise M. Reggiannini R. 《Selected Areas in Communications, IEEE Journal on》2001,19(6):1153-1163
One key requirement for radio access in advanced, third generation (3G) mobile communication systems is the ability to accommodate a variety of services via a flexible and efficient medium access control (MAC) protocol. The paper presents and evaluates a new multiple access protocol termed CRDA (collision resolution and dynamic allocation), which has the potential to meet the above requirement. CRDA is basically a slotted packet-reservation multiple access technique with dedicated reservation slots, which allows the main shortcoming of previous PRMA schemes, i.e., contention, to be overcome through the integration in the MAC protocol of a code-division multiple-access (CDMA) transmission mode used to access the reservation slots. This prevents collisions during the reservation phase and enhances channel throughput, notably in the case of mixed voice/data traffic. Our simulations of the CRDA MAC integrate voice channels with data sources, generating what we call advanced data traffic, which has a very similar shape to the actual traffic generated by World Wide Web (WWW) applications. The standard assumption of Poissonian data traffic is also considered. Our conclusion is that the CRDA MAC protocol satisfactorily accommodates both types of traffic 相似文献
52.
Arroyo-Abad U Elizalde-González MP Hidalgo-Moreno CM Mattusch J Wennrich R 《Journal of hazardous materials》2011,186(2-3):1328-1334
Sorption of phenylarsenicals including 4-hydroxy-3-nitrophenylarsonic acid (roxarsone), an animal feed additive widely used for growth stimulation, on soils was investigated in batch systems. Phenylarsonic acid, o-arsanilic acid and roxarsone were retained differently by unpolluted, non-sterilized soils. Sorption isotherms were analyzed by the Henry, Tóth and Langmuir-Freundlich equations. The saturation capacity of the Acrisol soil was 3.4 for o-arsanilic acid, 10.9 for phenylarsonic acid and 1.9 g(As) kg(soil)(-1) (dry mass) for roxarsone. The iron content in the soil was not the only factor determining retention of the studied phenylarsenicals. The order of retention on the three soils after 24 h was: roxarsone>o-arsanilic acid>phenylarsonic acid. Besides arsenite and arsenate, new arsenic-containing compounds were detected. 相似文献
53.
Reiner Hamm Djurdjica Masic und Luise Tetzlaff 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1971,147(2):71-76
Zusammenfassung Gefrieren (-20° C) and Auftauen der Brust- and Schenkelmuskulatur verschiedener Geflügelarten (Huhn, Pute, Gans, Ente) führte zu keiner nennenswerten Änderung der gesamten Aktivität der Aspartat-Aminotransferase (Glutamat-Oxalacetat-Transaminase; GOT) im Gewebe. Längere Gefrierlagerung (3 Monate) bei -20° C brachte beim Brustmuskel des Huhns keine Änderung, beim Schenkelmuskel jedoch eine Abnahme der gesamten GOT-Aktivität mit sich. Der Muskelpreßsaft von gefrorenem and aufgetautem Gewebe enthielt bei beiden Muskeln aller untersuchten Geflügelarten eine höhere GOT-Aktivität als der Preßsaft des frischen, nicht gefrorenen Gewebes. Diese Erhöhung der GOT-Aktivität beruht auf einer durch Gefrieren and Auftauen hervorgerufenen partiellen Freisetzung des Mitochondrien-Isozyms GOTM in das Sarkoplasma. Offensichtlich werden die Membranen der Muskelmitochondrien durch Gefrieren des Gewebes geschädigt. Es wird eine auf diesen Resultaten beruhende Routinemethode zur Unterscheidung zwischen Frischgeflügel and aufgetautem Gefriergeflügel beschrieben.
Fräulein Herta Sauer danken wir fur ihre fleißige and geschickte Mitarbeit. 相似文献
Influence of freezing and thawing on the subcellular distribution of aspartate aminotransferase in poultry muscle
Summary Freezing (—20° C) and thawing of the breast and thigh muscles of poultry (chicken, turkey, goose, duck) did not result in a remarkable change of the total activity of aspartate amino transferase (glutamate-oxaloacetic transaminase; GOT) in the tissue. Freeze-storage for three months (-20° C) did not cause changes in the total GOT activity in chicken breast muscle but did lower the GOT activity in the thigh muscle of chicken. For both types of muscle of all species investigated, freezing and thawing of tissue caused an increase in the GOT activity of the muscle press-juice. This increase of GOT activity is due to a partial release of the mitochondria) isozyme GOTM into the sarcoplasma. Apparently the membranes of the muscle mitochondria are damaged by the process of freezing. A routine method basing on these results is decsribed which allows a differentiation between nonfrozen poultry and frozen and thawed poultry.
Fräulein Herta Sauer danken wir fur ihre fleißige and geschickte Mitarbeit. 相似文献
54.
Migration towards a full-digital implementation of modems is currently one of the main trends in transmission systems design. The authors describe a noncoherent all-digital delay lock loop (DDLL) suited for chip timing synchronization in band-limited direct sequence spread spectrum (DS/SS) systems, and they thoroughly analyze its performance. The key features of this novel scheme are represented by its low-complexity processing section together with its good tracking capability. Analytical expressions for the DDLL S-curve and steady-state timing jitter are derived and confirmed by a time-domain computer simulation. Furthermore, the Mean Time to Lose Lock (MTLL) of the loop is evaluated and some numerical results are reported. The proposed chip timing synchronization scheme reveals also an improved tracking performance when compared to the traditional analog DLL for rectangular chip DS/SS signals 相似文献
55.
M. Schubert P. Morgenstern R. Wennrich K. Freyer H. Weiss 《Mine Water and the Environment》2003,22(1):2-6
One of the ore processing residues in the Mansfeld region of Germany is a flue dust, which was scrubbed out of the smelter
process gases by spraying water into the hot gas stream. During the many years of ore processing, the resulting fine-grained
sludge was washed into ponds for storage. These sludge deposits were covered by water and thus sealed off from the atmosphere.
However, after the local copper works shut down in 1990, the ponds dried up, causing the sludge in the uppermost layers to
oxidize. The need to assess the risk posed by these deposits today prompted questions over the depth to which the dried sludge
can be altered by weathering and the extent of heavy metal emissions. A drill hole was bored at the center of a dry pond and
the core samples analyzed. The samples indicated relatively constant levels of Cu and Pb with depth, but other metals, such
as Cd, Mn, and Zn, were relatively depleted in the upper 50 cm of the sludge body. Such behavior can be explained by the solubilities
of the respective secondary phases. It appears that the oxidation of metal sulfides and the subsequent dissolution of the
respective secondary phases, especially sulfates, pose a potential problem for the quality of the nearby ground and surface
water. 相似文献
56.
JR Zalcberg XF Hu DM Wall S Mirski S Cole G Nadalin M De Luise JD Parkin V Vrazas L Campbell 《Canadian Metallurgical Quarterly》1994,57(4):522-528
Separate mechanisms underlying the multidrug resistant (MDR) phenotype were identified in 2 independent approaches to select tumour cells resistant to low concentrations of doxorubicin (Dox) from the sensitive T cell leukemia cell line CCRF-CEM. The CEM/A7 cell line was selected at an initial concentration of 0.005 microgram/ml of Dox and maintained at 0.07 microgram/ml. In contrast, the CEM/A5 line was selected using an initial concentration of 0.01 microgram/ml and maintained in Dox at a concentration of 0.05 microgram/ml. P-glycoprotein expression was demonstrated in the CEM/A7 line but not the CEM/A5 line. Amplification of the mdrI gene was not observed in the CEM/A7 cell line. Both cell lines showed cross-resistance to a number of structurally unrelated cytotoxic drugs including anthracyclines and etoposide (VP-16), although only the CEM/A7 line was cross resistant to Vinca alkaloids. Immunoblots of total cell lysates of the CEM/A5 line have revealed almost undetectable levels of topoisomerase II alpha and beta in this line. Cytogenetic analyses of both lines revealed numerous karyotypic abnormalities which were present in the parental cell line as well as both resistant cell lines. The CEM/A7 line also demonstrated a duplication of part of the long arm of chromosome 7 which included the region containing the mdrI gene, a finding not seen in the parental or CEM/A5 line. CEM/A5, however, demonstrated an abnormality of chromosome 7, outside the region of the mdrI gene, and it also contained a deletion of the short arm of chromosome 2. Abnormalities in this latter region of genome have been associated with non-P-glycoprotein-mediated MDR. 相似文献
57.
BK Luise 《Canadian Metallurgical Quarterly》1996,7(4):130, 153-130, 154
58.
59.
Luise Fiedler Dr. Markus Kellner Rosel Oos PD Dr. Guido Böning Prof. Sibylle Ziegler Prof. Peter Bartenstein Prof. Reinhard Zeidler Dr. Franz Josef Gildehaus Dr. Simon Lindner 《ChemMedChem》2018,13(12):1230-1237
64Cu is a cyclotron‐produced radionuclide which offers, thanks to its characteristic decay scheme, the possibility of combining positron emission tomography (PET) investigations with radiotherapy. We evaluated the Alceo system from Comecer SpA to automatically produce 64Cu for radiolabelling purposes. We established a 64Cu production routine with high yields and radionuclide purity in combination with excellent operator radiation protection. The carbonic anhydrase XII targeting 6A10 antibody Fab fragment was successfully radiolabelled with the produced 64Cu, and proof‐of‐principle small‐animal PET experiments on mice bearing glioma xenografts were performed. We obtained a high tumor‐to‐contralateral muscle ratio, which encourages further in vivo investigations of the radioconjugate regarding a possible application in diagnostic tumor imaging. 相似文献
60.
The authors present a nonconventional joint data demodulation-pseudo-noise (PN) code tracking scheme for direct sequence (DS) spread-spectrum (SS) signals which solves problems of component imbalance and sensitivity with hardware simplicity and no performance degradation. An integrate-and-dump Costas loop is used for carrier recovery and data demodulation of the SS signal. Both data and carrier are then used to derive the baseband error signal of the code tracking loop. Moreover, a single passband correlator is used to perform the early-late correlation, leading to a hardware complexity equivalent to that of the tau-dither scheme, but without its loss in performance. Results of a thorough theoretical analysis of the system in an additive Gaussian noise (AWGN) environment are reported. They provide performance curves in terms of steady-state jitter and mean time to first lock loss. A superior jitter performance for low values of E b/ N 0 with respect to a traditional noncoherent delay lock loop (DLL) is shown, along with the potential gain of Manchester coding upon the more usual NRZ format 相似文献