Explicit coordination to prevent congestion in data center networks

Large cluster-based cloud computing platforms increasingly use commodity Ethernet technologies, such as Gigabit Ethernet, 10GigE, and Fibre Channel over Ethernet (FCoE), for intra-cluster communication. Traffic congestion can become a performance concern in the Ethernet due to consolidation of data, storage, and control traffic over a common layer-2 fabric, as well as consolidation of multiple virtual machines (VMs) over less physical hardware. Even as networking vendors race to develop switch-level hardware support for congestion management, we make the case that virtualization has opened up a complementary set of opportunities to reduce or even eliminate network congestion in cloud computing clusters. We present the design, implementation, and evaluation of a system called XCo, that performs explicit coordination of network transmissions over a shared Ethernet fabric to proactively prevent network congestion. XCo is a software-only distributed solution executing only in the end-nodes. A central controller uses explicit permissions to temporally separate (at millisecond granularity) the transmissions from competing senders through congested links. XCo is fully transparent to applications, presently deployable, and independent of any switch-level hardware support. We present a detailed evaluation of our XCo prototype across a number of network congestion scenarios, and demonstrate that XCo significantly improves network performance during periods of congestion. We also evaluate the behavior of XCo for large topologies using NS3 simulations.     

Systems approaches in global change and biogeochemistry research

Systems approaches have great potential for application in predictive ecology. In this paper, we present a range of examples, where systems approaches are being developed and applied at a range of scales in the field of global change and biogeochemical cycling. Systems approaches range from Bayesian calibration techniques at plot scale, through data assimilation methods at regional to continental scales, to multi-disciplinary numerical model applications at country to global scales. We provide examples from a range of studies and show how these approaches are being used to address current topics in global change and biogeochemical research, such as the interaction between carbon and nitrogen cycles, terrestrial carbon feedbacks to climate change and the attribution of observed global changes to various drivers of change. We examine how transferable the methods and techniques might be to other areas of ecosystem science and ecology.     

Efficacy of a Six-Month versus a 36-Month Regimen for Prevention of Tuberculosis in HIV-Infected Persons in India: A Randomized Clinical Trial

Background

The optimal duration of preventive therapy for tuberculosis (TB) among HIV-infected persons in TB-endemic countries is unknown.

Methods

An open-label randomized clinical trial was performed and analyzed for equivalence. Seven hundred and twelve HIV-infected, ART-naïve patients without active TB were randomized to receive either ethambutol 800 mg and isoniazid 300 mg daily for six-months (6EH) or isoniazid 300 mg daily for 36-months (36H). Drugs were dispensed fortnightly and adherence checked by home visits. Patients had chest radiograph, sputum smear and culture performed every six months, in addition to investigations if they developed symptoms. The primary endpoint was incident TB while secondary endpoints were all-cause mortality and adverse events. Survival analysis was performed on the modified intent to treat population (m-ITT) and rates compared.

Findings

Tuberculosis developed in 22 (6.4%) of 344 subjects in the 6EH arm and 13 (3.8%) of 339 subjects in the 36H arm with incidence rates of 2.4/100py (95%CI- 1.4–3.5) and 1.6/100py (95% CI-0.8–3.0) with an adjusted rate ratio (aIRR) of 1.6 (0.8–3.2). Among TST-positive subjects, the aIRR of 6EH was 1.7 (0.6–4.3) compared to 36H, p = 0.8. All-cause mortality and toxicity were similar in the two arms. Among 15 patients with confirmed TB, 4 isolates were resistant to isoniazid and 2 were multidrug-resistant.

Interpretation

Both regimens were similarly effective in preventing TB, when compared to historical incidence rates. However, there was a trend to lower TB incidence with 36H. There was no increase in isoniazid resistance compared to the expected rate in HIV-infected patients.The trial is registered at ClinicalTrials.gov, {"type":"clinical-trial","attrs":{"text":"NCT00351702","term_id":"NCT00351702"}}NCT00351702.     

Fat body catalase activity as a biochemical index for the recognition of thermotolerant breeds of mulberry silkworm, Bombyx mori L.

The fifth instar larvae of the silkworm Bombyx mori L. were exposed to selected high temperatures (35 and 40 °C) in order to understand the changes in the level of catalase activity in the three tissues of fat body, midgut and haemolymph of the five selected bivoltine breeds and their 9 quantitative traits, namely larval weight, cocoon weight, shell weight, shell ratio, filament length, filament weight, denier, renditta and effective rearing rate (ERR), also the correlation between them under high temperature conditions were examined. Catalase activity resulting in fat body revealed a positive correlation between the control (28±1 °C) and 40±1 °C. The CSR₂ breed showed the most level of thermotolerance and catalase activity, compared with the CSR₄, JROP, NB₄D₂ and KA breeds. It was found that the level of catalase activity in fat body may be a reliable biochemical index to recognize thermotolerant breeds in order to develop resistant hybrids for tropical areas.     

<Emphasis Type="Italic">Strobilanthes pothigaiensis</Emphasis> (<Emphasis Type="Italic">Acanthaceae</Emphasis>) — a new species from southern Western Ghats,India

Summary   Strobilanthes pothigaiensis, a new species of Strobilanthes (Acanthaceae) allied to S. foliosus T. Anderson from southern Western Ghats, India, is described and illustrated.     

Technique for cryopreservation of intestinal smooth muscle cells

Attempts were made to develop a simplified procedure for long-term cryopreservation of intestinal smooth muscle cells (ISMC). ISMC were collected from the ileum of Sprague-Dawley neonatal rats through cellular dissociation in trypsin. Cryopreservation method comprised of a rapid 1-step (protocol 1) and a slow 3-step (protocol 2) freezing of ISMC for 1 week. Preparations were thawed and single ISMC were assessed via the comet assay and damaged DNA was quantified through comet tail moment. The control unfrozen ISMC exhibited DNA damage of 2.34 ± 0.35 compared to ISMC cooled via protocol 2 (2.62 ± 0.36) and protocol 1 (10.15 ± 0.72). Thereafter, protocol 2 freezing method was adopted and ISMC were cryopreserved for 1-week, 1-month, and 4-months to analyse the temporal and long-term cryopreservation of ISMC. This revealed a DNA damage of 2.62 ± 0.36 (1-week), 3.81 ± 0.72 (1-month), and 5.1 ± 0.9 (4-months). Gradual cooling is suitable for continuing storage of ISMC and although fluctuation in cryoinjury is observed with time this is considered to reflect cell-to-cell variability.