Social media usage during the recent uprisings in Arab countries has gained increasing attention in human–computer interaction research. This study adds to these insights by providing some findings on the use of information and communications technology (ICT), specifically mobile media, by opposition forces and political activists during the Syrian civil war. The presented study is based on 17 interviews with Syrian FSA fighters, activists, and refugees. A first analysis showed evidence for some very specific use patterns during wartime (compared to media usage of political activists under less anomic conditions). The study also describes a fragmented telecom infrastructure in Syria: government-controlled regions offer fairly intact infrastructures while rebel-controlled regions have been cut off from telephone and Internet. Moreover, the central and very critical role of mobile video for documenting, mobilization, and propaganda is discussed. 相似文献
Ontologies – a form of structured and logically related knowledge or classification hierarchy embedded in a computer system – are regarded by many scientists as having enormous promise for the consistent use and re-use of data. To realise this promise, however, is not straightforward. In this paper, based on ethnographic observation, we argue that the challenges for ontology building are ‘social’ as much as they are technical. By this we mean the routine work undertaken in the building process and the problems and difficulties entailed can be understood in terms of the practices of knowledge workers and the practical nature of ‘sorting things out’. Getting a better sense of how, in practise, this work gets done gives a sense of the main challenges of building successful ontologies and how this impacts on the design of tool support. In considering the practices of one group in particular, we try to show how, for members, the technical problems of determining what classification structure is appropriate, and what its boundaries might be, depend substantially on assumptions about the ‘community’ and its interests and purposes. This ‘turn to the social’ has ramifications for the understanding of ontology building and use. Specifically, ‘modelling’ approaches to ontology building tell us little about the practical organisation of the work and how this relates to the prospect of successful sharing. Ethnographic enquiry may reveal important issues that are otherwise missed. 相似文献
Purpose: Identification of the biomarkers of oocyte quality, and developmental and reprogramming potential is of importance to assisted reproductive technology in humans and animals. Experimental design: PerkinElmer ExacTag? Kit was used to label differentially proteins in pig oocyte extracts (oocyte proteome) and pig oocyte‐conditioned in vitro maturation media (oocyte secretome) obtained with high‐ and low‐quality oocytes. Results: We identified 16 major proteins in the oocyte proteome that were expressed differentially in high‐ versus low‐quality oocytes. More abundant proteins in the high‐quality oocyte proteome included kelch‐like ECH‐associated protein 1 (an adaptor for ubiquitin‐ligase CUL3), nuclear export factor CRM1 and ataxia‐telangiectasia mutated protein kinase. Dystrophin (DMD) was more abundant in low‐quality oocytes. In the secretome, we identified 110 proteins, including DMD and cystic fibrosis transmembrane conductance regulator, two proteins implicated in muscular dystrophy and cystic fibrosis, respectively. Monoubiquitin was identified in the low‐quality‐oocyte secretome. Conclusions and clinical implications: A direct, quantitative proteomic analysis of small oocyte protein samples can identify potential markers of oocyte quality without the need for a large amount of total protein. This approach will be applied to discovery of non‐invasive biomarkers of oocyte quality in assisted human reproduction and in large animal embryo transfer programs. 相似文献
We investigate how path failure influences Concurrent Multipath Transfer (CMT) using SCTP multihoming. We show that CMT suffers from significant “receive buffer blocking” which degrades performance during both permanent and short-term failure. To improve performance, we introduce a new “Potentially-Failed” (PF) destination state, and revise CMT’s failure detection and (re)transmission policies to include the PF state. Using simulation, we demonstrate that the modification called CMT-PF outperforms CMT during failure – even with aggressive failure detection thresholds and varying receive buffer constraints. In non-failure scenarios, CMT-PF performs on par or better but never worse than CMT. Finally, we confirm these simulation results using FreeBSD implementations of CMT and CMT-PF. Based on our findings, we recommend CMT-PF be used in existing and future CMT implementations and RFCs. 相似文献
Issues of trust, privacy and security at the intersection of state intervention and the use of the internet both by ‘publics’ and by individuals for—from the State’s point of view- dispreferred purposes have been of great recent interest to researchers. This has been accompanied by a slowly developing concern for the way in which these issues pan out for people in non-Western cultures. Based on a study of Iranians living in urban centers, we examine the way in which culture, State institutions, technological infrastructure and practices intersect. Iran is a republic with a theocratic constitution and relatively strict regulation of private life. It has one of the highest rates of internet appropriation and social media use in the MENA region, but use is heavily mediated by state interventions, for instance the filtering of sites such as Facebook and Twitter. We show how young Iranians, due to restrictions on their private lives, learn from early age on to deal with illegal access techniques such as proxy servers and virtual private networks (VPNs). These access technologies are often used for private purposes such as contacting and meeting other genders. However, these capabilities become even more important when preparing to leave the country or to articulate their political dissatisfaction, specifically at moments of political unrest. We discuss and develop the concept of ‘counter-appropriation’ and the ‘counter-public’ to describe the practices of urban dwellers in circumventing increasingly more sophisticated intervention by the state security apparatus.
A quantitative method is described for the gas chromatographic analysis of glyceryl ethers using their trifluoroacetate (TFA)
and trimethylsilyl (TMS) ether derivatives. Both derivatives are prepared at room temperature by reactions that proceed virtually
to completion in less than 15 min, eliminating time-consuming derivative preparations and laborious clean-up steps of unreacted
materials required by other methods. Gas-liquid chromatography (GLC) resolves the 1- and 2-isomers of the glyceryl ether TFA
derivatives, which have not been separated previously. Purified synthetic 1- and 2-glyceryl ethers, including saturated and
mono- and diunsaturated, were used to evaluate several polar and nonpolar liquid phases for the analysis of the TFA and TMS
derivatives. Analyses can be made on some liquid phases normally used for methyl esters, while others are unsatisfactory.
A mixture of isomeric C18 saturated and monoand di-unsaturated TFA derivatives was partially resolved; however, a complete analysis of this mixture
can be made by preliminary separation of the unsaturates on silver-ion-impregnated thin-layer plates or by GLC analysis alone
with three different phases.
Presented at the AOCS meeting, Cincinnati, October, 1965.
Under contract with US Atomic Energy Commission. 相似文献
Inhibition isotherms were measured for Western Kentucky No.9 coal. Crushed and sieved coal (?25 + 140 U.S. mesh) was fluidized in 10-g batches in a 22-mm i.d. quartz reactor up to a temperature of 870 °C. The release of hydrogen sulphide during heatup under nitrogen and at the run temperature (usually 1–2 h) under the same gas (pyrolysis), hydrogen, or hydrogen/hydrogen sulphide mixtures was followed by gas chromatography. The residue or char was analysed for pyritic, organic, sulphide, sulphate, and total sulphur. Inhibition isotherms, which are pseudo-equilibria between sulphur in the char and gaseous hydrogen sulphide, were measured at 600 and 870 °C. At the lower temperature the isotherm was found to be independent of the hydrogen sulphide concentration in the gas stream and the char sulphur content remained constant at 2.6%. At 870 °C the sulphur content of the char was greater than that of the original coal when gas mixtures of 1, 3, and 6% hydrogen sulphide in hydrogen were used, indicating the necessity of maintaining low hydrogen sulphide concentration for sulphur removal. In pure hydrogen, sulphur removal increased continuously from 47% at 600 °C to 84% at 870 °C. For pyrolysis under nitrogen, sulphur removal was 40% at 600 °C and increased to 59% at 740 °C. No further removal occurred above this temperature up to 870 °C. In addition to the inhibition isotherms, sulphur-form transformation diagrams were constructed for coal treated with nitrogen, hydrogen, and hydrogen/hydrogen sulphide mixtures. Pyritic sulphur, which comprised 40% of the sulphur in the original coal, was completely converted to ferrous sulphide at 600 °C in hydrogen and 740 °C in nitrogen. At 870 °C the sulphur content of the char produced under hydrogen was 1.1% made up of 48.4% ferrous sulphide, 43.4% organic sulphur, and 8.2% sulphate. 相似文献
Thin, hard ceramic coatings on metals and ceramics are extensively used for wear and abrasion resistance, friction control, corrosion resistance, and tailored functional (electrical, optical, and magnetic) properties across a wide range of high-performance applications. Coating producers and users have to measure and control the coating-substrate adhesion strength, because adhesion failure is often the primary failure mechanism of the coating, limiting its performance and life. The quantitative test method of choice for thin hard coatings is scratch adhesion testing. In this technique, a diamond stylus is drawn across the coating on the surface under increasing normal load and the damage to the coating is assessed against the applied load. With DOE funding and in coordination with the ASTM Committees C28, G08, and B02, a new scratch adhesion test standard has been researched and written and has been published. The ASTM C1624 test standard (Adhesion Strength and Mechanical Failure Modes of Ceramic Coatings by Quantitative Scratch Testing) provides comprehensive and detailed guidance and instructions on scratch adhesion testing of thin, hard ceramic coatings—the principles, terminology, applications, limitations, equipment, specimen preparation and characterization, critical experimental factors, calibration, procedures, calculations, and reporting requirements. 相似文献
The U.S. Air Force and the Environmental Security Technology Certification Program (ESTCP) funded a multi-year collaborative project to test the ability of portable hand-held laser coating removal systems (PLCRS) to remove organic coatings from metallic and non-metallic substrates in an effort to reduce the use of hazardous chemicals and/or solid waste generated from more conventional removal methods. A 250 W carbon dioxide, 40 W neodymium: yttrium, aluminum, garnet (Nd:YAG), and 120 W Nd:YAG laser systems were evaluated for removing a variety of primer and topcoat combinations on 2024 T-3 and 7075 T-6 (bare and aluminum clad with chromate conversion coatings or chromic acid anodize), 4130 steel, honeycomb materials, Kevlar, graphite epoxy, and fiberglass epoxy substrates. Engineering tests were conducted to assess coating removal rate, physical substrate damage, modification of substrate properties, and impact on subsequent paint adhesion. The results of engineering tests were compared to baseline data (i.e., virgin material) and test data available in the literature for conventional coating removal techniques. 相似文献