Commodity single board computer clusters and their applications

© 2018 Current commodity Single Board Computers (SBCs) are sufficiently powerful to run mainstream operating systems and workloads. Many of these boards may be linked together, to create small, low-cost clusters that replicate some features of large data center clusters. The Raspberry Pi Foundation produces a series of SBCs with a price/performance ratio that makes SBC clusters viable, perhaps even expendable. These clusters are an enabler for Edge/Fog Compute, where processing is pushed out towards data sources, reducing bandwidth requirements and decentralizing the architecture. In this paper we investigate use cases driving the growth of SBC clusters, we examine the trends in future hardware developments, and discuss the potential of SBC clusters as a disruptive technology. Compared to traditional clusters, SBC clusters have a reduced footprint, are low-cost, and have low power requirements. This enables different models of deployment—particularly outside traditional data center environments. We discuss the applicability of existing software and management infrastructure to support exotic deployment scenarios and anticipate the next generation of SBC. We conclude that the SBC cluster is a new and distinct computational deployment paradigm, which is applicable to a wider range of scenarios than current clusters. It facilitates Internet of Things and Smart City systems and is potentially a game changer in pushing application logic out towards the network edge

Next generation single board clusters

Until recently, cluster computing was too expensive and too complex for commodity users. However the phenomenal popularity of single board computers like the Raspberry Pi has caused the emergence of the single board computer cluster. This demonstration will present a cheap, practical and portable Raspberry Pi cluster called Pi Stack. We will show pragmatic custom solutions to hardware issues, such as power distribution, and software issues, such as remote updating. We also sketch potential use cases for Pi Stack and other commodity single board computer cluster architectures

The Aerotactic Response of Caulobacter crescentus

Many motile microorganisms are able to detect chemical gradients in their surroundings to bias their motion toward more favorable conditions. In this study, we observe the swimming patterns of Caulobacter crescentus, a uniflagellated bacterium, in a linear oxygen gradient produced by a three-channel microfluidic device. Using low-magnification dark-field microscopy, individual cells are tracked over a large field of view and their positions within the oxygen gradient are recorded over time. Motor switching events are identified so that swimming trajectories are deconstructed into a series of forward and backward swimming runs. Using these data, we show that C. crescentus displays aerotactic behavior by extending the average duration of forward swimming runs while moving up an oxygen gradient, resulting in directed motility toward oxygen sources. Additionally, the motor switching response is sensitive both to the steepness of the gradient experienced and to background oxygen levels, exhibiting a logarithmic response

Phenotypic and Functional Changes in Blood Monocytes Following Adherence to Endothelium

Blood monocytes are known to express endothelial-like genes during co-culture with endothelium. In this study, the time-dependent change in the phenotype pattern of primary blood monocytes after adhering to endothelium is reported using a novel HLA-A2 mistyped co-culture model.Freshly isolated human PBMCs were co-cultured with human umbilical vein endothelial cells or human coronary arterial endothelial cells of converse human leukocyte antigen A2 (HLA-A2) status. This allows the tracking of the PBMC-derived cells by HLA-A2 expression and assessment of their phenotype pattern over time. PBMCs that adhered to the endothelium at the start of the co-culture were predominantly CD11b+ blood monocytes. After 24 to 72 hours in co-culture, the endothelium-adherent monocytes acquired endothelial-like properties including the expression of endothelial nitric oxide synthase, CD105, CD144 and vascular endothelial growth factor receptor 2. The expression of monocyte/macrophage lineage antigens CD14, CD11b and CD36 were down regulated concomitantly. The adherent monocytes did not express CD115 after 1 day of co-culture. By day 6, the monocyte-derived cells expressed vascular cell adhesion molecule 1 in response to tumour necrosis factor alpha. Up to 10% of the PBMCs adhered to the endothelium. These monocyte-derived cells contributed up to 30% of the co-cultured cell layer and this was dose-dependent on the PBMC seeding density.Human blood monocytes undergo rapid phenotype change to resemble endothelial cells after adhering to endothelium

Electrocardiography : a technologist's guide to interpretation

The nuclear medicine technologist works with electrocardiography when performing cardiac stress testing and gated cardiac imaging and when monitoring critical patients. To enhance patient care, basic electrocardiogram interpretation skills and recognition of key arrhythmias are essential for the nuclear medicine technologist. This article provides insight into the anatomy of an electrocardiogram trace, covers basic electrocardiogram interpretation methods, and describes an example case typical in the nuclear medicine environment.6 page(s

User-level Data Center Tomography

Measurement and inference in data centers present a set of opportunities and challenges distinct from the Internet domain. Existing toolsets may be perturbed or be mislead by issues related to virtualization. Yet, while equally confronted by scale, data centers are relatively homogenous and symmetric. We believe these may be attributes to be exploited. However, data is required to better evaluate our hypotheses. Therefore, we introduce our efforts to gather data using a single framework from which we can launch tests of our choosing. Our observations reinforce recent claims, but indicate changes in the network. They also reveal additional obfuscations stemming from virtualization

Increased expression of VEGFR2 and VCAM-1, reduced expression of CD36 and expression of CD31 and ICAM-1 in the endothelium-adherent monocytes in co-culture.

<p>HLA-A2+ PBMCs (1×10⁶ cells/well) were incubated for 2 h (Day 0) with HLA-A2− HUVEC, after which the non-adherent cells were removed by washing. The cell layers were analysed by dual-colour flow cytometry for HLA-A2 and VEGFR2 expression on Day 1 (A) and Day 2 (B) of co-culture, VCAM-1 expression in the absence of TNF-α on Day 6 of co-culture (C), VCAM-1 expression on Day 6 of co-culture after 24 hours of stimulation with TNF-α (10 ng/ml) (D), CD36 expression on Day 0 (E) and Day 1 (F) of co-culture, as well as CD31 (G) and ICAM-1 (H) expression on Day 0. Representative plots from 2–5 individual experiments are shown.</p

Quantification of endothelium-adherent monocytes in co-culture.

<p>PBMCs were seeded onto HUVECs of converse HLA-A2 status, co-incubated for 2 h, after which the non-adherent cells were washed off. The percentage of HLA-A2+ cells was evaluated using dual-colour flow cytometry after 24–48 h of co-culture. The graph shows the effect of varying the PBMC seeding densities at 0.25×10⁶, 0.5×10⁶ and 1.0×10⁶ cells/well. The % HLA-A2+ PBMCs co-cultured with the HLA-A2− HUVECs (grey bars) and the % HLA-A2− PBMCs co-cultured with HLA-A2+ HUVECs (black bars) are shown.</p

Down-regulation of CD14 and CD11b expression in the endothelium-adherent monocytes during co-culture.

<p>HLA-A2+ PBMCs (1×10⁶ cells/well) were incubated for 2 h (Day 0) with HLA-A2− HUVECs, after which the non-adherent cells were removed by washing. The cell layers were assessed by dual-colour flow cytometry for HLA-A2 and (A) CD14 expression on Day 1 and (B) CD11b expression on Day 3 of co-culture. These are representative plots from 4–7 individual experiments. The reduction in CD14 expression from Day 0 to Day 5 (C) and CD11b expression from Day 0 to Day 3 (D) is also shown.</p