1,173 research outputs found
Design of an 8-BIT VLSI Packet Switch Element
This paper describes the design of the Packet Switch Element Chip, one of the components of a high speed broadcast packet switching network. The chip is a 2x2 switch element, from which a switch fabric of arbitrary size can be constructed. It is currently being implemented in 2um CMOS technology
Infusion of plasma-derived mannan-binding lectin (MBL) into MBL-deficient humans.
To access publisher full text version of this article. Please click on the hyperlink in Additional Links fieldOur first experience of mannan-binding lectin (MBL)-replacement therapy was with a patient experiencing recurrent erythema multiforme associated with reactivation of herpes simplex virus; his erythematous eruptions could be controlled with infusions of fresh frozen plasma containing MBL, but not with plasma lacking MBL. Some years later, we treated a young girl with recurrent, debilitating infections with purified MBL; this was also followed by a dramatic clinical improvement. We have now carried out a phase I clinical trial on 20 MBL-deficient, but healthy, adult volunteers. The MBL was prepared by the State Serum Institute in Copenhagen, Denmark, from blood donor plasma. Each volunteer received a total of 18 mg of MBL in three 6-mg doses given intravenously once a week over 3 weeks. The volunteers were monitored closely after each infusion and no adverse clinical or laboratory effects were observed. Laboratory parameters included C-reactive protein, various complement components, and antibodies to MBL, HIV and hepatitis viruses. C3a (the anaphylotoxin derived from complement component C3) was monitored for signs of complement activation, but no significant infusion-associated fluctuations were observed. Serum levels of MBL after each 6-mg infusion ranged between 1200 and 2500 ng/ml. The half-life of the infused MBL was about 70 h, or 3 days. It was concluded that infusion of purified MBL manufactured by the Danish State Serum Institute is a safe procedure. However, adults may have to be given 6 mg or more at least twice weekly to maintain protective plasma MBL levels in MBL-deficient individuals
Connexin Gene Expression And The Control Of Gap Junction Assembly In Preimplantation Development
Gap junctional communication in preimplantation mouse embryos was explored by investigating: (1) the expression pattern of the connexin (Cx: gap junction protein) multigene family in maturing mouse oocytes and preimplantation embryos; (2) the relative role of Cx43 in gap junctional communication in embryos; and (3) the control of the acquisition of gap junctional coupling.;Both Cx43 and Cx32 transcripts were detected in maturing oocytes but these transcripts declined to undetectable levels shortly after ovulation. Cx43 transcripts were detected again at the 4-cell stage and accumulated steadily thereafter to reach a maximum in blastocysts. Cx26 and Cx46 transcripts could not be detected in embryos. By Western blotting Cx43 was detected in 1-cell embryos, the levels decreased by the 2-cell stage, and then increased gradually from the 4-cell stage to the blastocyst stage. Oogenetic expression of Cx32 and 43 is therefore replaced by exclusive Cx43 expression in the embryos and it is probably Cx43 that is the main contributor to the assembly of gap junctions at the 8-cell stage. To attempt to inhibit Cx43 gene expression, embryos were either microinjected with Cx43 antisense deoxyoligonucleotides, or cultured in their presence. Dye coupling and Cx43 mRNA levels were not noticeably affected by the presence of the antisense reagents.;Treatment of 4-cell embryos with an activator of protein kinase C triggered premature compaction without an accompanying establishment of gap junctional communication. On the other hand, when coupled, 8-cell embryos were treated with the activator, intercellular coupling was diminished. Western blot analysis revealed that Cx43 becomes phosphorylated between the late 4-cell stage and the late morula stage. Aphidicolin experiments showed that the third and fourth rounds of DNA synthesis are not required for the normal acquisition of gap junctional communication. However, embryos in which the second round of DNA synthesis was delayed by 10 hours failed to initiate gap junctional coupling. Immunofluorescence localization of Cx43 in these communication-deficient embryos revealed extensive cytoplasmic Cx43 staining but punctate interblastomeric staining, indicative of gap junction plaques, was absent.;These results are consistent with a model in which the regulated step in the onset of gap junction assembly involves the phosphorylation of cytoplasmic Cx43
Two geometric inequalities in harmonic analysis
We study two geometric inequalities in harmonic analysis.In the first part we study the Brascamp-Lieb inequality. We re- examine several of the approaches that have yielded results for this inequality and use them to
derive new results. Specifically we prove an inequality involving the Hessian of the
optimal transport map and use it to derive the generalised Brascamp-Lieb and
reverse Brascamp-Lieb inequality with the methods of Barthe. Also, we extend
the heat flow methods from Carlen, Lieb and Loss to give the form of all optimisers for the Brascamp-Lieb inequality and we use the induction on dimension
method of Bennett, Carbery, Christ and Tao to prove a Brascamp-Lieb inequality
for finite fields. Finally, we study the set of LP- indices where the Brascamp-Lieb
inequality holds and give alternative ways of describing it in several situations.In the second part we study a multilinear analogue of fractional integration
which has been studied in one form by Drury. We give the L bounds for it and
find the optimal constant for this bound in the case with the most symmetries.
We also determine all functions which are optimisers for this inequality. Finally,
we study an analogue of this form which corresponds to the Hilbert transform.
Here the finiteness of the form depends on cancellation properties in the kernel
and we show how to define the form in terms of distributions. Then we prove L
bounds for that form
Performance Evaluation of a User Network Interface for ATM Networks
In this paper the functionality requirements of a user-network interface for bandwidth allocation are discussed. Such requirements include the capability to provide end users with a variety of non-deteriorating connection types. In addition effective policy enforcement and traffic shaping mechanisms are required to facilitate network management and the efficient utilization of network resources. Based on these requirements, a user-network interface model is proposed, and its performance is studied. Its intrinsic properties are revealed for two cases, a Poisson source and a bursty source
The endpoint multilinear Kakeya theorem via the Borsuk--Ulam theorem
We give an essentially self-contained proof of Guth's recent endpoint
multilinear Kakeya theorem which avoids the use of somewhat sophisticated
algebraic topology, and which instead appeals to the Borsuk-Ulam theorem
Cervical artery dissection - review
Neðst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinn Skoða/Opna(view/open)In recent years carotid and vertebral artery dissections have been diagnosed more frequently, probably because new imaging techniques are more reliable and they are certainly less invasive. The cause of cervical artery dissections is largely unexplained but probably involves a combination of genetic and environmental factors such as trauma or infection. Most authors recommend intravenous heparin or low molecular weight heparin followed by oral warfarin to maintain INR between 2-3 for 3-6 months. If the artery has healed after 3-6 months of anti-coagulation all treatment can be stopped but if there is a remaining stenosis the patient can be put on aspirin 75-100 mg a day. The long-term prognosis of cervical artery dissection is favourable in the majority of patients. New dissections are uncommon.Áður var flysjun í innri hálsslagæð (arteria carotis interna) eða hryggslagæð (arteria vertebralis) talin sjaldgæf ástæða heilablóðfalls en vegna betri greiningartækni og aukinnar vitneskju lækna um sjúkdóminn greinist flysjun mun oftar en áður. Er flysjun nú talin ein helsta ástæða heilablóðþurrðar hjá yngri og miðaldra einstaklingum. Meingerð flysjunar er lítt þekkt. Líklega er oftast um að ræða undirliggjandi galla í æðarvegg ásamt útleysandi þáttum eins og áverkum á hálsi eða sýkingu. Grunur um sjúkdóminn vaknar við klínísk einkenni á borð við skyndilegan verk á hálsi, andliti eða höfði og/eða Horners-heilkenni með eða án einkenna heilablóðþurrðar. Greiningin er staðfest með því að sýna fram á dæmigerðar breytingar á æðinni með myndrannsókn. Hefðbundin meðferð hefst með heparín-innrennsli í æð eða lágmólekúlarheparíni gefið undir húð. Síðan tekur við blóðþynning með warfaríntöflum (með það að markmiði að halda INR milli 2,0-3,0) í 3-6 mánuði
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