Silicon spin diffusion transistor: materials, physics and device characteristics

The realisation that eaveryday electronics has ignored the spin of the carrier in favour of its charge is the foundation of the field of spintronics. Starting with simple two-terminal devices based on GMR and tunnel magnetoresistance, the technology has advanced to consider three-terminal devices that aim to combine spin sensitivity with a high current gain and a large current output. These devices require both efficient spin injection and semiconductor fabrication. In this paper, a discussion is presented of the design, operation and characteristics of the only spin transistor that has yielded a current gain greater than one in combination with reasonable output current

Reconfigurable Autonomy

This position paper describes ongoing work at the Universities of Liverpool, Sheffield and Surrey in the UK on developing hybrid agent architectures for controlling autonomous systems, and specifically for ensuring that agent-controlled dynamic reconfiguration is viable. The work outlined here forms part of the Reconfigurable Autonomy research project

Efek laju alir dan arah aliran terhadap analisis performa alat penukar panas tipe shell and tube heat exchanger menggunakan SCADA

Panas atau kalor merupakan energi yang dapat berpindah dikarenakan perbedaan temperatur. Dalam melakukan perpindahan panas, dibutuhkan sebuah alat agar mendukung terjadinya perpindahan panas. Alat perpindahan panas yang digunakan pada penelitian ini adalah Shell and Tube Heat Exchanger (STHE). Penelitian ini menggunakan program SCADA yang dapat melakukan proses akusisi data dan kontrol terhadap variabel dependen yaitu laju alir fluida panas sehingga diharapkan data yang ditampilkan pada program SCADA dapat merepresentasikan pengaruh laju alir dan arah aliran terhadap analisis performa alat penukar panas tipe STHE. Penelitian dilakukan dengan memvariasikan laju alir fluida panas pada rentang 0.8 L/min – 1.8 L/min, dimana pada alat ini memiliki maksimum laju alir 2,1 L/min. Dari penelitian ini didapatkan bahwa efektivitas tertinggi sebesar 0,44 pada laju alir fluida panas 1.8 L/min dengan aliran fluida berlawanan arah. Dari hal ini, dapat disimpulkan bahwa laju alir fluida dan arah aliran fluida mempengaruhi efektivitas alat penukar panas, namun bukan hanya mempengaruhi efektivitas alat penukar panas, laju alir dan arah aliran fluida juga mempengaruhi analisis yang lainnya seperti bilangan Reynold, perubahan temperatur rata-rata logaritmik, Number of Transfer Unit (NTU), dan juga efektivitas NTU. Laju alir pada alat penukar panas berpengaruh terhadap besarnya panas yang akan diserap maupun dikeluarkan sehingga, ketika laju alir mengalami peningkatan maka efektivitas alat penukar panas juga akan mengalami peningkatan dikarenakan hal ini dipengaruhi oleh besarnya panas yang dikeluarkan maupun yang diterima

Regulation of Angiogenesis Discriminates Tissue Resident MSCs from Effective and Defective Osteogenic Environments

[Abstract] Background: The biological mechanisms that contribute to atrophic long bone non-union are poorly understood. Multipotential mesenchymal stromal cells (MSCs) are key contributors to bone formation and are recognised as important mediators of blood vessel formation. This study examines the role of MSCs in tissue formation at the site of atrophic non-union. Materials and Methods: Tissue and MSCs from non-union sites (n = 20) and induced periosteal (IP) membrane formed following the Masquelet bone reconstruction technique (n = 15) or bone marrow (n = 8) were compared. MSC content, differentiation, and influence on angiogenesis were measured in vitro. Cell content and vasculature measurements were performed by flow cytometry and histology, and gene expression was measured by quantitative polymerase chain reaction (qPCR). Results: MSCs from non-union sites had comparable differentiation potential to bone marrow MSCs. Compared with induced periosteum, non-union tissue contained similar proportion of colony-forming cells, but a greater proportion of pericytes (p = 0.036), and endothelial cells (p = 0.016) and blood vessels were more numerous (p = 0.001) with smaller luminal diameter (p = 0.046). MSCs showed marked differences in angiogenic transcripts depending on the source, and those from induced periosteum, but not non-union tissue, inhibited early stages of in vitro angiogenesis. Conclusions: In vitro, non-union site derived MSCs have no impairment of differentiation capacity, but they differ from IP-derived MSCs in mediating angiogenesis. Local MSCs may thus be strongly implicated in the formation of the immature vascular network at the non-union site. Attention should be given to their angiogenic support profile when selecting MSCs for regenerative therapy

Observations of quasi-periodic solar X-ray emission as a result of MHD oscillations in a system of multiple flare loops

We investigate the solar flare of 20 October 2002. The flare was accompanied by quasi-periodic pulsations (QPP) of both thermal and nonthermal hard X-ray emissions (HXR) observed by RHESSI in the 3-50 keV energy range. Analysis of the HXR time profiles in different energy channels made with the Lomb periodogram indicates two statistically significant time periods of about 16 and 36 seconds. The 36-second QPP were observed only in the nonthermal HXR emission in the impulsive phase of the flare. The 16-second QPP were more pronounced in the thermal HXR emission and were observed both in the impulsive and in the decay phases of the flare. Imaging analysis of the flare region, the determined time periods of the QPP and the estimated physical parameters of magnetic loops in the flare region allow us to interpret the observations as follows. 1) In the impulsive phase energy was released and electrons were accelerated by successive acts with the average time period of about 36 seconds in different parts of two spatially separated, but interacting loop systems of the flare region. 2) The 36-second periodicity of energy release could be caused by the action of fast MHD oscillations in the loops connecting these flaring sites. 3) During the first explosive acts of energy release the MHD oscillations (most probably the sausage mode) with time period of 16 seconds were excited in one system of the flare loops. 4) These oscillations were maintained by the subsequent explosive acts of energy release in the impulsive phase and were completely damped in the decay phase of the flare.Comment: 14 pages, 4 figure

Improved high-dimensional prediction with Random Forests by the use of co-data

Background: Prediction in high dimensional settings is difficult due to the large number of variables relative to the sample size. We demonstrate how auxiliary 'co-data' can be used to improve the performance of a Random Forest in such a setting. Results: Co-data are incorporated in the Random Forest by replacing the uniform sampling probabilities that are used to draw candidate variables by co-data moderated sampling probabilities. Co-data here are defined as any type information that is available on the variables of the primary data, but does not use its response labels. These moderated sampling probabilities are, inspired by empirical Bayes, learned from the data at hand. We demonstrate the co-data moderated Random Forest (CoRF) with two examples. In the first example we aim to predict the presence of a lymph node metastasis with gene expression data. We demonstrate how a set of external p-values, a gene signature, and the correlation between gene expression and DNA copy number can improve the predictive performance. In the second example we demonstrate how the prediction of cervical (pre-)cancer with methylation data can be improved by including the location of the probe relative to the known CpG islands, the number of CpG sites targeted by a probe, and a set of p-values from a related study. Conclusion: The proposed method is able to utilize auxiliary co-data to improve the performance of a Random Forest

An Empirical Study of the Object-Oriented Paradigm and Software Reuse

Little or no empirical validation exists for many of software engineering's basic assumptions. While some of these assumptions are intuitive, the need for scientific experimentation remains clear. Several assumptions are made about the factors affecting software reuse, and in particular, the role of the object-oriented paradigm. This paper describes the preliminary results of a controlled experiment designed to evaluate the impact of the object-oriented paradigm on software reuse. The experiment concludes that (1) the object-oriented paradigm substantially improves productivity, although a significant part of this improvement is due to the effect of reuse, (2) reuse without regard to language paradigm improves productivity, (3) language differences are far more important when programmers reuse than when they do not, and (4) the object-oriented paradigm has a particular affinity to the reuse process

Dust Devil Tracks

Dust devils that leave dark- or light-toned tracks are common on Mars and they can also be found on the Earth’s surface. Dust devil tracks (hereinafter DDTs) are ephemeral surface features with mostly sub-annual lifetimes. Regarding their size, DDT widths can range between ∼1 m and ∼1 km, depending on the diameter of dust devil that created the track, and DDT lengths range from a few tens of meters to several kilometers, limited by the duration and horizontal ground speed of dust devils. DDTs can be classified into three main types based on their morphology and albedo in contrast to their surroundings; all are found on both planets: (a) dark continuous DDTs, (b) dark cycloidal DDTs, and (c) bright DDTs. Dark continuous DDTs are the most common type on Mars. They are characterized by their relatively homogenous and continuous low albedo surface tracks. Based on terrestrial and martian in situ studies, these DDTs most likely form when surficial dust layers are removed to expose larger-grained substrate material (coarse sands of ≥500 μm in diameter). The exposure of larger-grained materials changes the photometric properties of the surface; hence leading to lower albedo tracks because grain size is photometrically inversely proportional to the surface reflectance. However, although not observed so far, compositional differences (i.e., color differences) might also lead to albedo contrasts when dust is removed to expose substrate materials with mineralogical differences. For dark continuous DDTs, albedo drop measurements are around 2.5 % in the wavelength range of 550–850 nm on Mars and around 0.5 % in the wavelength range from 300–1100 nm on Earth. The removal of an equivalent layer thickness around 1 μm is sufficient for the formation of visible dark continuous DDTs on Mars and Earth. The next type of DDTs, dark cycloidal DDTs, are characterized by their low albedo pattern of overlapping scallops. Terrestrial in situ studies imply that they are formed when sand-sized material that is eroded from the outer vortex area of a dust devil is redeposited in annular patterns in the central vortex region. This type of DDT can also be found in on Mars in orbital image data, and although in situ studies are lacking, terrestrial analog studies, laboratory work, and numerical modeling suggest they have the same formation mechanism as those on Earth. Finally, bright DDTs are characterized by their continuous track pattern and high albedo compared to their undisturbed surroundings. They are found on both planets, but to date they have only been analyzed in situ on Earth. Here, the destruction of aggregates of dust, silt and sand by dust devils leads to smooth surfaces in contrast to the undisturbed rough surfaces surrounding the track. The resulting change in photometric properties occurs because the smoother surfaces have a higher reflectance compared to the surrounding rough surface, leading to bright DDTs. On Mars, the destruction of surficial dust-aggregates may also lead to bright DDTs. However, higher reflective surfaces may be produced by other formation mechanisms, such as dust compaction by passing dust devils, as this may also cause changes in photometric properties. On Mars, DDTs in general are found at all elevations and on a global scale, except on the permanent polar caps. DDT maximum areal densities occur during spring and summer in both hemispheres produced by an increase in dust devil activity caused by maximum insolation. Regionally, dust devil densities vary spatially likely controlled by changes in dust cover thicknesses and substrate materials. This variability makes it difficult to infer dust devil activity from DDT frequencies. Furthermore, only a fraction of dust devils leave tracks. However, DDTs can be used as proxies for dust devil lifetimes and wind directions and speeds, and they can also be used to predict lander or rover solar panel clearing events. Overall, the high DDT frequency in many areas on Mars leads to drastic albedo changes that affect large-scale weather patterns