Bonding Changes in Compressed Superhard Graphite Mao, Wendy L.; Mao, Ho-kwang; Eng, Peter J. ...
Science (American Association for the Advancement of Science),
10/2003, Letnik:
302, Številka:
5644
Journal Article
Recenzirano
Compressed under ambient temperature, graphite undergoes a transition at ~17 gigapascals. The near K-edge spectroscopy of carbon using synchrotron x-ray inelastic scattering reveals that half of the ...π-bonds between graphite layers convert to σ-bonds, whereas the other half remain as π-bonds in the high-pressure form. The x-ray diffraction pattern of the high-pressure form is consistent with a distorted graphite structure in which bridging carbon atoms between graphite layers pair and form σ-bonds, whereas the nonbridging carbon atoms remain unpaired with π-bonds. The high-pressure form is superhard, capable of indenting cubic-diamond single crystals.
This volume explores linguistic diversity and complexity in different urban contexts, many of which have never been subject to significant sociolinguistic inquiry. A novel mixture of cities of ...varying size from around the world is studied, from megacities to smaller cities on the national periphery. All chapters discuss either the multilingualism or the pluricentric aspect of the linguistic diversity in urban areas, most focussing on one urban centre.
Based on a qualitative and quantitative survey of introduction and address and naming behaviour of Austrian academics at international conferences in linguistics and language studies, we compare ...reported strategies in Austrian German and in English as a lingua franca (ELF). The scenarios asked about are self-introduction, introduction of others and when being introduced by others. Overall, the qualitative data demonstrate that Austrian academics are well aware of the social and linguistic complexities of introductions at international conferences as well as of cross-cultural differences in introduction and address conventions in academia. Quantitative results show important differences across scenarios and between the two languages of communication. Elements of the cohort's L1 introduction behaviour, such as high frequency of title use when introducing others, confirm previous studies. To determine if there are any transfer effects from their L1, the ELF introduction behaviour of the Austrian German L1 speakers is also compared to the L1 behaviour of speakers of US English. The frequency of reported first name use in ELF introductions by our Austrian respondents is similar to that reported by their American counterparts. However, title use by Austrians in ELF scenarios is consistently higher than among US English L1 speakers, indicating pragmatic transfer.
•The national variety of one's first language influences introduction behaviour.•This influence can be seen both in the first language and in English.•Speakers of Austrian German tend to be formal when introducing others in German.•When using English, they are much less formal in self-introductions than in German.•When introducing others in English, they tend to be more formal than US Americans.
In Germany geriatric outpatient care is predominantly done by family doctors and general practitioners (GP). There are regionally different concepts for additional specialized geriatric outpatient ...care but they have not yet been validated and established. Still, it remains unclear whether a geriatric patient has to be diagnosed rather in a specialized outpatient or inpatient setting. The aim of the present study is the profiling of geriatric outpatients to find key distinctions from geriatric patients that have to be admitted to hospital.
Retrospective data analysis of patients sent to a specialized geriatric outpatient clinic by their GP, compared with data of geriatric inpatients sent to hospital by their GP during the same time period. Study parameters comprised elements of the comprehensive geriatric assessment as well as results of routinely applied laboratory tests.
Patients sent to the specialized geriatric outpatient clinic showed better results of functional assessments. Regression analysis: improvement of Barthel Index, GFR and total protein increased the chance of outpatient treatment.
Early identification of geriatric patients who can be treated in a specialized outpatient setting would ease the burden for GPs by interdisciplinary cooperation and prevent cost-intensive readmissions to hospital.
Purpose
Herpes simplex virus (HSV) and varicella-zoster virus (VZV) are neurotropic human alphaherpesviruses endemic worldwide. Upon primary infection, both viruses establish lifelong latency in ...neurons and reactivate intermittently to cause a variety of mild to severe diseases. Acute retinal necrosis (ARN) is a rare, sight-threatening eye disease induced by ocular VZV or HSV infection. The virus and host factors involved in ARN pathogenesis remain incompletely described. We hypothesize an underlying genetic defect in at least part of ARN cases.
Methods
We collected blood from 17 patients with HSV-or VZV-induced ARN, isolated DNA and performed Whole Exome Sequencing by Illumina followed by analysis in Varseq with criteria of CADD score > 15 and frequency in GnomAD < 0.1% combined with biological filters. Gene modifications relative to healthy control genomes were filtered according to high quality and read-depth, low frequency, high deleteriousness predictions and biological relevance.
Results
We identified a total of 50 potentially disease-causing genetic variants, including missense, frameshift and splice site variants and on in-frame deletion in 16 of the 17 patients. The vast majority of these genes are involved in innate immunity, followed by adaptive immunity, autophagy, and apoptosis; in several instances variants within a given gene or pathway was identified in several patients.
Discussion
We propose that the identified variants may contribute to insufficient viral control and increased necrosis ocular disease presentation in the patients and serve as a knowledge base and starting point for the development of improved diagnostic, prophylactic, and therapeutic applications.
Natural olivine with 12 mol % Fe2 SiO4 and synthetic orthopyroxenes with 20% and 40% FeSiO3 were studied beyond the pressure-temperature conditions of the core-mantle boundary. All samples were found ...to convert entirely or partially into the CalrO3 postperovskite structure, which was recently reported for pure MgSiO3. The incorporation of Fe greatly reduces the pressure needed for the transition and establishes the new phase as the major component of the D″ layer. With the liquid core as an unlimited reservoir of iron, core-mantle reactions could further enrich the iron content in this phase and explain the intriguing seismic signatures observed in the D″ layer.
The Earth's core is comprised mostly of iron and nickel, but it also contains several weight percent of one or more unknown light elements, which may include silicon. Therefore it is important to ...understand the high pressure, high temperature properties and behavior of alloys in the Fe–FeSi system, such as their phase diagrams. We determined melting temperatures and subsolidus phase relations of Fe–9wt% Si and stoichiometric FeSi using synchrotron X-ray diffraction at high pressures and temperatures, up to ~200GPa and ~145GPa, respectively. Combining this data with that of previous studies, we generated phase diagrams in pressure–temperature, temperature–composition, and pressure–composition space. We find the B2 crystal structure in Fe–9Si where previous studies reported the less ordered bcc structure, and a shallower slope for the hcp+B2 to fcc+B2 boundary than previously reported. In stoichiometric FeSi, we report a wide B2+B20 two-phase field, with complete conversion to the B2 structure at ~42GPa. The minimum temperature of an Fe–Si outer core is 4380K, based on the eutectic melting point of Fe–9Si, and silicon is shown to be less efficient at depressing the melting point of iron at core conditions than oxygen or sulfur. At the highest pressures reached, only the hcp and B2 structures are seen in the Fe–FeSi system. We predict that alloys containing more than ~4–8wt% silicon will convert to an hcp+B2 mixture and later to the hcp structure with increasing pressure, and that an iron–silicon alloy in the Earth's inner core would most likely be a mixture of hcp and B2 phases.
•We determined phase diagrams of Fe–9Si and FeSi to 200 and 145GPa, respectively.•The phase diagram of FeSi has a wide B20+B2 mixed phase field.•Silicon is inefficient at depressing Fe melting curve at core pressures.•T–X and P–X phase diagrams suggest transitions to B2+hcp then hcp for most alloys.•Extrapolation of phase diagrams suggests B2+hcp mixture at inner core conditions.
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