Buffering packetised data: an examination of the crossover effect

Buffer analysis has traditionally relied heavily on the use of traffic models with short range (exponentially decaying) autocorrelation, e.g. Poisson and Markov modulated Poisson processes. Recent literature has suggested the presence of traffic with slowly (hyperbolically) decaying autocorrelation functions; these sources collectively and individually seem to be exhibiting the phenomenon of long range dependence (LRD). Furthermore, it has been claimed that this sort of traffic may exhibit behaviour, when buffered, that is advantageous in that a smaller buffer may be required than would be the case with non-LRD traffic. This phenomenon has been named the crossover effect, and the authors quantify its relevance to ATM networking, using simulation studies of a homogenous mix of chaotic sources. These show that there is a crossover effect, but the key finding is that this effect is much nearer to a buffer length of zero than was predicted by previous theoretical studies, actually occurring at a value so low that it has no practical significance     

Modeling of current-voltage characteristics for strained andlattice matched HEMT's on InP substrate using a variational chargecontrol model

A model for the calculation of the current-voltage characteristics of strained In_0.52Al_0.48As/In_xGa_1-xAs on InP substrate High Electron Mobility Transistors (HEMT's), based on a variational charge control model, is presented. A polynomial fit of the two-dimensional electron gas (2DEG) density is used for the calculation of the current-voltage characteristics. The effect of strain is introduced into the 2DEG density versus gate voltage relation. Very good agreement between the calculated and measured I-V characteristics was obtained. In addition, our results show that, for an indium mole fraction of the In_xGa_1-xAs channel in the range 0.53-0.60, increasing the indium mole fraction lowers the threshold voltage and hence increases the drain current at the same gate bias     

Effect of spark discharge parameters on the ignition of gas mixtures

The influence of the duration and spatial extent of a heat-releasing spark discharge on the critical conditions of spark ignition of a reactive gas is considered. A region insensitive to the effect of these parameters and, thus, suitable for work with the instantaneous source model is defined. Tomsk. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 5, pp. 3–7, September–October, 1993.     

Diagnostic results and their clinical interpretation--or: what you never wanted to know about diagnosis

OBJECTIVE: To analyze HLA-DR4 alleles in New Zealand Polynesians with rheumatoid arthritis (RA). METHODS: Thirty Polynesians and 30 Caucasians with RA, as well as 65 Polynesian and 60 Caucasian healthy blood donors, were DR4 subtyped using the polymerase chain reaction and sequence-specific oligonucleotide probes. RESULTS: The frequency of DR4 (DRB1*04) was increased in both Polynesian (P < 0.001) and Caucasian (P < 0.005) RA patients compared with race-matched controls. Dw4 (DRB1*0401) was detected in 15 of 30 Caucasian patients but only 2 of 30 Polynesian patients (P < 0.001). In Polynesians, RA was associated with Dw15 (DRB1*0405), which was present in 11 of 30 patients and 3 of 65 controls (P < 0.001). Dw13 (DRB1*0403) was the most frequent DR4 allele in healthy Polynesians, but was not significantly associated with RA. CONCLUSION: The predominance of the Dw13 subtype in Polynesians may explain in part the low prevalence of RA in this population. The association of Dw15 with RA in Polynesians supports the hypothesis that the third hypervariable region of DR beta determines susceptibility to RA.     

Acquired hemophilia and rheumatoid arthritis. Value of intravenous immunoglobulins

The authors report an exceedingly rare complication of rheumatoid arthritis, i.e. acquired hemophilia due to anti-factor VIII autoantibody production. Treatment with intravenous immune globulin ensured control of hemorrhagic manifestations by inducing a transient rise in factor VIII level.     

Influence of To?pa Peat Preparation on the phagocytic activity and bactericidal properties of granulocytes in healthy volunteers

It was found, that To?pa Peat Preparation (TPP) administered to healthy volunteers in doses of 100-300 mg/day during 14 days evoked the stimulation of the phagocytic and bactericidal activity of the granulocytes. The dose of 600 mg/day causes only a transient and insignificant increase of phagocytic and bactericidal properties of the granulocytes.     

False aneurysm of the left ventricle and coronary aneurysms in Beh?et disease

A false left ventricular aneurysm and coronary artery aneurysm were discovered in a 29 year old patient with Beh?et's syndrome. The operation under cardiopulmonary bypass consisted of closing the neck of the false aneurysm by an endo-aneurysmal approach with a Gore-Tex patch. The coronary artery aneurysms were respected. There were no postoperative complications. Cardiac involvement is rare in Beh?et's syndrome (6%). The originality of this case is the association of two aneurysmal pathologies: the coronary and ventricular aneurysms due to the angiitis and the myocardial fragility induced by ischaemia.     

Porphyromonas-like gram-negative rods in naturally occurring periodontitis in dogs

A total of 259 Gram-negative Porphyromonas-like rods isolated from subgingival plaque samples of 16 family-owned dogs with naturally occurring periodontitis were characterized phenotypically by biochemical reactions, metabolic end products and enzymatic activities (API-ZYMTM, RoscoTM). Four distinct groups were found. Group A isolates (63) were asaccharolytic, lipase negative, trypsin positive and produced phenylacetic acid (PAA) from peptone-yeast extract glucose broth. Unlike P. gingivalis strains they were catalase positive. Group B isolates (42) differed from those of group A by a positive lipase reaction and from those of group D by failing to ferment sugars. Group C isolates (88) were asaccharolytic and did not produce PAA. They were alpha-fucosidase, N-acetyl-beta-glucosaminidase (beta-NAG) and trypsin negative, resembling P. endodontalis, but unlike human isolates, they were catalase positive. Subgroup C.1 isolates (6) differed from those of parent group C by producing minor amounts of PAA, and subgroup C.2 isolates (12) were beta-NAG positive. Group D isolates (46) were weakly fermentative, lipase, catalase and trypsin positive, and produced PAA. They resembled the B (P.) salivosus type strain which, in our hands, fermented weakly glucose, lactose and mannose. Two isolates could not be assigned to any of the previous groups.     

Beta-COP is essential for biosynthetic membrane transport from the endoplasmic reticulum to the Golgi complex in vivo

Experimental glomerulonephritis was induced in rats to investigate the consequence of the antigen-antibody interaction on the surface of glomerular endothelial cells (GENs). A lectin, Lens culinaris hemoagglutinin (LCH), was first planted in the left kidney by isolated perfusion of a left kidney, and then the circulation was reestablished. Rabbit anti-LCH antibodies were injected from the tail vein 3 minutes after the recirculation of the left kidney, and acute glomerulonephritis ensued. Fifteen minutes after the injection, rabbit immunoglobulin G (IgG), rat C3, and LCH were observed exclusively on the surface of GENs. Accumulation of platelets was prominent. Three hours later, the immune deposits were seen in the subendothelial space, and the polymorphonuclear cells were the dominant infiltrate in the glomeruli. Up to the seventh day, immune deposits were seen in the subendothelial space, and the widening of this area was increasingly observed. Fourteen days later, immune deposits containing rat IgG were observed in the subepithelial area, but they were only occasionally seen in the subendothelial space and in the mesangial area. No crescent formation was seen at day 14, but the mesangial area was expanded, with an increased number of cells. The number of nuclei in the cross-section of a glomerulus increased after the induction of glomerulonephritis, but the number of leukocyte common antigen-positive cells (infiltrating cells) decreased gradually from day 4 to day 14. The staining of Thy-1.1, a marker of mesangial cell, was markedly enlarged in the glomerulus at day 14. These data suggest that mesangial proliferative glomerulonephritis can be induced by the antigen-antibody interaction on the surface of GENs.