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Deposit formation on turbine hardware in propulsion turbine engines can occur in many arid regions globally. Characterising crystalline deposits on metallic substrates can aid in component resilience and health monitor algorithms during particle ingestion. This study has developed two statistical empirical models for prediction from acquired experimental data for the onset of deposits. The prediction models are for crystalline particulate (Arizona Road Test Dust) deposits on a flat rectangular Hastelloy-X test coupon. Particle impingement angles varied between 20° and 80° in experimental flow temperatures of 1,000–1,100°C. Averaged deposits are methodically quantified through normalised particle deposit tallies per area and percent coverage of the surface using microscopic imaging and image processing programs. Deposit accumulation is a quadratic function of both near-surface coupon temperature and coupon angle.
The prevalence of colonization with toxigenic Clostridium difficile among patients with hematological malignancies and/or bone marrow transplant at admission to a 566-bed academic medical care center was 9.3%, and 13.3% of colonized patients developed symptomatic disease during hospitalization. This population may benefit from targeted C. difficile infection control interventions.
Although repeatedly associated with white matter microstructural alterations, bipolar disorder (BD) has been relatively unexplored using complex network analysis. This method combines structural and diffusion magnetic resonance imaging (MRI) to model the brain as a network and evaluate its topological properties. A group of highly interconnected high-density structures, termed the ‘rich-club’, represents an important network for integration of brain functioning. This study aimed to assess structural and rich-club connectivity properties in BD through graph theory analyses.
We obtained structural and diffusion MRI scans from 42 euthymic patients with BD type I and 43 age- and gender-matched healthy volunteers. Weighted fractional anisotropy connections mapped between cortical and subcortical structures defined the neuroanatomical networks. Next, we examined between-group differences in features of graph properties and sub-networks.
Patients exhibited significantly reduced clustering coefficient and global efficiency, compared with controls globally and regionally in frontal and occipital regions. Additionally, patients displayed weaker sub-network connectivity in distributed regions. Rich-club analysis revealed subtly reduced density in patients, which did not withstand multiple comparison correction. However, hub identification in most participants indicated differentially affected rich-club membership in the BD group, with two hubs absent when compared with controls, namely the superior frontal gyrus and thalamus.
This graph theory analysis presents a thorough investigation of topological features of connectivity in euthymic BD. Abnormalities of global and local measures and network components provide further neuroanatomically specific evidence for distributed dysconnectivity as a trait feature of BD.
Resilience is the capacity of individuals to resist mental disorders despite exposure to stress. Little is known about its neural underpinnings. The putative variation of white-matter microstructure with resilience in adolescence, a critical period for brain maturation and onset of high-prevalence mental disorders, has not been assessed by diffusion tensor imaging (DTI). Lower fractional anisotropy (FA) though, has been reported in the corpus callosum (CC), the brain's largest white-matter structure, in psychiatric and stress-related conditions. We hypothesized that higher FA in the CC would characterize stress-resilient adolescents.
Three groups of adolescents recruited from the community were compared: resilient with low risk of mental disorder despite high exposure to lifetime stress (n = 55), at-risk of mental disorder exposed to the same level of stress (n = 68), and controls (n = 123). Personality was assessed by the NEO-Five Factor Inventory (NEO-FFI). Voxelwise statistics of DTI values in CC were obtained using tract-based spatial statistics. Regional projections were identified by probabilistic tractography.
Higher FA values were detected in the anterior CC of resilient compared to both non-resilient and control adolescents. FA values varied according to resilience capacity. Seed regional changes in anterior CC projected onto anterior cingulate and frontal cortex. Neuroticism and three other NEO-FFI factor scores differentiated non-resilient participants from the other two groups.
High FA was detected in resilient adolescents in an anterior CC region projecting to frontal areas subserving cognitive resources. Psychiatric risk was associated with personality characteristics. Resilience in adolescence may be related to white-matter microstructure.
Two seasons of work have now been conducted by British and French survey teams, in conjunction with members of the Libyan Antiquities Department, under the charge of Dr. Abdullah Shaiboub. The objectives of the survey are to locate, survey and analyse the extensive remains of the ancient agricultural settlements that can be found in the wadis of the hinterlands of Tripolitania and the Sirtica. Within the framework established by the Department in cooperation with Unesco lies the archaeological aim of recording the evidence for periods when extensive areas of the pre-desert were, for whatever reasons, cultivated in ways that are not similarly practised today. In the longer term the programme is designed to locate those areas where modern farming might be re-established. Archaeology is thus brought into line with the aims of the modern world.
For the purposes of this report we intend to concentrate on the period which we call the Romano/Libyan in which the great majority of those farming settlements flourished. The prehistoric evidence is in any case mainly of the palaeolithic period, on which there is a separate section.
The preferred zone of settlement in Tripolitania has traditionally been the well watered coastal plain and the adjacent limestone hills of the Tarhuna Gebel as far south as the town of Beni Ulid, for these regions have more than 200 mm of rain a year, regarded as the threshold for settled farming without irrigation. Prehistoric settlement concentrated here, and mixed farming has probably characterised this zone from the fourth millennium b.c. In the Roman period the coastal cities like Sabratha and Leptis Magna were supported by prosperous farms on the plain and in the Gebel. In the Islamic period, too, the same region was densely settled.
Three seasons of intensive survey in the central Tripolitanian pre-desert, primarily in the regions of the Wadis Sofeggin and Zem Zem, have provided a new basis for the study of pre-desert cultures. Not only have hundreds of new sites been discovered, but the combination of environmental and geomorphological studies with archaeological survey is now providing important information about the underlying mechanisms which supported them. An increasing settlement density and social complexity can be identified in the Romano–Libyan period together with the development of intensive farming and elaborate irrigation systems. There is little evidence for significant climatic change to account for this increased settlement intensity or for its subsequent decline. The explanation for this must probably be sought in a complex relationship between social organisation, population change, and the agricultural system, and its impact on the environment.
A fourth season of work was carried out in the Spring of 1984. The centrepiece of the programme was the investigation of the well-preserved farm in the Wadi el-Amud (Lamout). The main farm buildings were excavated, faunal and botanical samples were collected systematically from within and between them, the field systems and sluices were examined in detail and investigations begun on the geomorphological and hydrological context. This report presents the basic description of the archaeological data resulting from excavation and survey; a second report will present the results of the various laboratory studies which were generated by the field work.
The final season of the three-year programme to survey the central Tripolitanian pre-desert examined the region to the west of the regions of the Wadis Sofeggin and Zem Zem, casting important light on the route between the interior of Libya and the coast during the prehistoric and Roman periods. In particular, a detailed account is given of the archaeological sites of the Bir Scedua Basin and of the Severan fort at Gheriat el-Garbia.
This report presents the preliminary results of the final season of the UNESCO Libyan Valleys Survey, that took place in October 1989. The fieldwork was divided in two parts. The first part of the work concentrated on the settlements in the Wadi Buzra, a northern tributary of the Wadi Sofeggin, especially at Souk el Awty. The major monument here consists of a substantial church (published elsewhere by D. A. Welsby in this volume), which was investigated by architectural survey and limited excavation, as were the surrounding late Romano-Libyan farms. The modern name of the settlement suggests that it may have been an important centre in Islamic as well as the Romano-Libyan periods, but the excavation did not obtain conclusive chronological evidence. The second part of the fieldwork was in the Wadi Umm el-Kharab, a southern tributary of the Sofeggin. Here, the team carried out a detailed study of a series of fortified farms of the later Romano-Libyan period, to compare with the open farm of the earlier Romano-Libyan period in Wadi el Amud previously studied by the project. An analysis of the constructional details of the major farms was integrated with excavations to recover stratified dating evidence from within the farms and faunal and botanical evidence from associated middens, and with a survey of the water-control systems of walls down the length of the wadi. The study indicates that the wadi was settled by people living in open farms and nucleated settlements in the first four centuries AD, but that by the fifth and sixth centuries AD these were replaced by fortified farms. There is evidence that the occupants of the fortified farms cultivated the wadi within an integrated economic system characterised by centralised food storage, rather than as independent units.
This paper describes the system architecture of a newly constructed radio telescope – the Boolardy engineering test array, which is a prototype of the Australian square kilometre array pathfinder telescope. Phased array feed technology is used to form multiple simultaneous beams per antenna, providing astronomers with unprecedented survey speed. The test array described here is a six-antenna interferometer, fitted with prototype signal processing hardware capable of forming at least nine dual-polarisation beams simultaneously, allowing several square degrees to be imaged in a single pointed observation. The main purpose of the test array is to develop beamforming and wide-field calibration methods for use with the full telescope, but it will also be capable of limited early science demonstrations.
Excavations at the Easton Down long barrow were part of a wider programme of research into the Neolithic sequence and context of the Avebury area in north Wiltshire. The short barrow, on high chalk downland to the south-west of Avebury and the upper Kennet valley, and containing only a few inhumations according to Thurnam's 19th-century investigation, dates to the later 4th millennium BC. Test pits around the barrow produced very little struck flint, and virtually no colluvium in the adjacent dry valley to the west. The mound covered a thin calcareous turfline above a rubbly soil, probably formerly cultivated. The pre-barrow molluscan fauna, soil micromorphology and other environmental data indicate a clearance adjacent to woodland. In the secondary fill of the flanking ditches there is a succession from renewed woodland to open conditions in the Late Neolithic.
The Easton Down monument falls relatively late in the regional sequence of long barrow construction. Its setting was probably one of scattered, non-permanent clearances in woodland. Woodland was still widespread on the higher downland of the region in the middle of the Neolithic. Renewed and bigger-scale clearance towards the end of the Neolithic may be connected with the construction of very large monuments elsewhere in the region. The later prehistoric landscape became both more open and less diverse.
The marble-clad surfaces of the numerous bars or shops (so-called thermopolia) of Pompeii and Herculaneum are a vast and hitherto untapped source of information about marble use beyond the confines of public building and élite houses. Four field seasons of survey work have documented 49 bars at Pompeii and eight at Herculaneum with over 8,000 pieces of stone, mainly marble. This paper discusses the results of this project: first, the types of stone used on these bars and how they were displayed; second, what their quantities and distribution, within these cities and on individual bars, reveal about the pervasiveness of the wider pan-Mediterranean marble trade; third, what we can say about where these materials came from and how they were acquired, and what this in turn reveals about the economics of reuse of architectural materials in the Vesuvian cities.
Blood flow is one of the most fundamental physiological parameters. Maintenance of adequate blood flow is vital for the health of biological tissue. The growth and function of many organ systems are linked tightly to their blood supply. In addition, many disease processes are associated with either increases or decreases in flow compared with normal values. The development and validation of non-invasive tools for the measurement of flow have been longstanding goals, both in biomedical research and in clinical practice.
Traditionally, the imaging of flow, or perfusion, has been accomplished using either nuclear medicine-based techniques involving radioactive isotopes, or X-ray computed tomography (CT) methods using radio-opaque contrast agents. However, soon after the introduction of magnetic resonance imaging (MRI) for anatomical imaging, research began on techniques for depicting flow. Since then, progress has been rapid, not least because MR methods have the advantage of not involving radiation, and in the case of arterial spin labeling-based techniques, are completely non-invasive. This makes them particularly appealing for use in a wide range of populations, including children and normal subjects. In addition, MR perfusion can be combined with the armamentarium of other structural, vascular, physiological, metabolic, and functional techniques available with MR to provide a comprehensive, “one-stop” examination for the patient.