Balanced Scheduling toward Loss-Free Packet Queuing and Delay Fairness

In current networks, packet losses can occur if routers do not provide sufficiently large buffers. This paper studies how many buffers should be provided in a router to eliminate packet losses. We assume a network router has m incoming queues, each corresponding to a single traffic stream, and must schedule at any time on-line from which queue to take the next packet to send out. To exclude packet losses with a small amount of buffers, the maximum queue length must be kept low over the entire scheduling period. We call this new on-line problem the balanced scheduling problem (BSP). By competitive analysis, we measure the power of on-line scheduling algorithms to prevent packet losses. We show that a simple greedy algorithm is Θ(log m)-competitive which is asymptotically optimal, while Round-Robin scheduling is not better than m-competitive, as actually is any deterministic on-line algorithm for BSP. We also give a polynomial time algorithm for solving off-line BSP optimally. We also study another on-line balancing problem that tries to balance the delay among the m traffic streams.     

Induced Zinc Loss Produces Heterogenous Biological Responses in Melanoma Cells

Zinc levels in serum and/or tissue are reported to be altered in melanoma with unknown effects on melanoma development and biology. The purpose of this study was to examine the effects of acute chelation of free intracellular zinc pools in melanoma cell lines Bowes and A375, as well as selected melanoma tissue explants with high or low intracellular free zinc. Zinc chelating agent TPEN at the concentration of 25 µM was employed during 48 h, which significantly reduced intracellular free zinc while decreasing melanoma cell proliferation, inducing G1/S arrest and cell damage leading to mitochondrial, caspase-dependent apoptosis. Chelation of free zinc was also associated with increased generation of superoxide in cell lines but not marked lysosomal membrane damage. Conversely, melanoma explant cultures mostly displayed time-dependent loss of lysosomal membrane integrity in the presence of slowly growing superoxide levels. Loss of free zinc-dependent p53 activity was similarly disparate in individual melanoma models. Surviving melanoma cells were arrested in the cell cycle, and varying proportions of them exhibited features characteristic of premature senescence, which increased in time despite zinc reloading. The present results show that melanoma cells with varying free zinc levels respond to its acute loss in a number of individual ways, reflecting activated mechanisms including oxidative stress, lysosomal damage, and p53 activity leading to heterogenous outcomes including cell death, transient, and/or permanent cell cycle arrest and premature senescence.     

Could SGLT2 Inhibitors Improve Exercise Intolerance in Chronic Heart Failure?

Despite the constant improvement of therapeutical options, heart failure (HF) remains associated with high mortality and morbidity. While new developments in guideline-recommended therapies can prolong survival and postpone HF hospitalizations, impaired exercise capacity remains one of the most debilitating symptoms of HF. Exercise intolerance in HF is multifactorial in origin, as the underlying cardiovascular pathology and reactive changes in skeletal muscle composition and metabolism both contribute. Recently, sodium-related glucose transporter 2 (SGLT2) inhibitors were found to improve cardiovascular outcomes significantly. Whilst much effort has been devoted to untangling the mechanisms responsible for these cardiovascular benefits of SGLT2 inhibitors, little is known about the effect of SGLT2 inhibitors on exercise performance in HF. This review provides an overview of the pathophysiological mechanisms that are responsible for exercise intolerance in HF, elaborates on the potential SGLT2-inhibitor-mediated effects on these phenomena, and provides an up-to-date overview of existing studies on the effect of SGLT2 inhibitors on clinical outcome parameters that are relevant to the assessment of exercise capacity. Finally, current gaps in the evidence and potential future perspectives on the effects of SGLT2 inhibitors on exercise intolerance in chronic HF are discussed.     

Messung und Theorie der Wandschubspannung bei Zweiphasenströmung im Rohr

Zusammenfassung Im allgemeinen gilt es als selbstverst?ndlich, da? ein durch ein Rohr str?mendes Medium auf die Rohrwand eine Schubspannung in Richtung der Str?mung übertr?gt. Aus Versuchen und überlegungen geht jedoch hervor, da? bei Zweiphasenstr?mungen im Schwerefeld auf Grund der Vorg?nge an der Wand die Schubspannung u. U. der Hauptstromrichtung entgegengerichtet ist. Auch ergibt sich, da? die dynamisch, d. h. unter Einflu? der Reibung gemessene F?rderh?he einer Pumpe h?her als die hydrostatisch berechnete sein kann. VDI Mitteilung aus dem Institut für kalorische Apparate und K?ltetechnik der Eidgen?ssischen Technischen Hochschule Zürich Herrn Prof. Dr. phil.E. Justi zur Vollendung seines 60. Geburtstags gewidmet.     

Das Schwinden und seine Beziehungen zu Rohwichte und Aufbau des Holzes

Zusammenfassung Einleitend werden Rohwiechte und Holzfeuchtigkeit als grundlegende Weiser technisch wichtiger Holzeigenschaften behandelt und die physikalischen Vorg?nge beim Zutrift von Wasser zu Holz erl?utert, die für die Untersuchung des Schwindvorganges von besonderer Bedeutung sind. Die Zusammenh?nge zwischen Luftfeuchtigkeit, Temperatur und Holzfeuehtigkeit k?nnen durch Einführung des S?ttigungsgrades der Luft an Stelle der relativen Luftfeuchtigkeit vereinfacht dargestellt werden (Bild 3). Die Raumquellung des Holzes kann bei vorangegangener vorsichtiger Mitteilung aus dem Mechanisch-technologischen Institut der Reichsanstalt für Holzforschung.