820 research outputs found

    Nanogratings Formation in a System of Ultra-short Laser Pulses – Metalloorganic Gas – Deposited Metal – Sapphire in Sinergetic Interference Field with Waveguide Modes Participation

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    Experimental results of laser-induced deposition of structured metal films from metalloorganic vapor have been analyzed. A new physical model has been put forward to explain the results. The model is based on the interference phenomena between the incident laser radiation and waveguide modes of a thermally induced gradient waveguide in the substrate. Keywords: femtosecond radiation, metal deposition, interference, waveguide modes, surface nanogratings

    Measurement of pressure and assessment of cavitation for a 22.5-kHz intra-arterial angioplasty device

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    This study was performed to understand better the mechanisms of action of an (22.5 kHz) ultrasonic wire catheter device used to remove atheromatous plaque in diseased blood vessels (ultrasonic angioplasty). During a clinical procedure, the wire acts as an acoustic waveguide to transfer acoustic energy from a generator outside the body to the ball tip of the wire, which is inserted in the blood vessel. The acoustic field radiated by the vibrating ball tip (1.5- to 3.0-mm diameter), was mapped in a relatively large (600 L) water tank and compared to the field from a well-characterized simple source. A dipolelike radiation pattern due to the translating ball tip was observed. At low power settings, standing wave effects in a smaller cylindrical volume (200-mm diameter, 350-mm height), which was used to simulate anthropometric dimensions, increase relative to the larger tank measurements. The standing wave ratio is dependent upon the pc characteristics of the medium and the dimensions of the volume, rather than on the absorption at this frequency. At high power-settings of the device, cavitation at the tip of the wire was measured using a 20-MHz passive cavitation detection scheme

    Program on Earth Observation Data Management Systems (EODMS), appendixes

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    The needs of state, regional, and local agencies involved in natural resources management in Illinois, Iowa, Minnesota, Missouri, and Wisconsin are investigated to determine the design of satellite remotely sensed derivable information products. It is concluded that an operational Earth Observation Data Management System (EODMS) will be most beneficial if it provides a full range of services - from raw data acquisition to interpretation and dissemination of final information products. Included is a cost and performance analysis of alternative processing centers, and an assessment of the impacts of policy, regulation, and government structure on implementing large scale use of remote sensing technology in this community of users

    Screening and managing a low-risk pregnant population using continuous-wave Doppler ultrasound in a low-income population: A cohort analytical study

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    Background. In South Africa (SA), the largest category of perinatal deaths is unexplained stillbirths. Two-thirds of these occur in the antenatal period and most fetuses are macerated, but at antenatal clinics the mothers were generally regarded as healthy, with low-risk pregnancies. Innovative methods are urgently required to detect fetuses at risk of stillbirth and manage the mothers appropriately.Objectives. To determine the prevalence of raised resistance indices (RIs) of the umbilical artery in a low-risk, low-income population and ascertain whether use of this information can prevent perinatal deaths.Methods. A descriptive study was performed in Mamelodi township, east of Pretoria, SA, on pregnant women attending antenatal clinics draining to two community health centres (CHCs). These women, classified as having low-risk pregnancies, were screened for placental insufficiency using a continuous-wave Doppler ultrasound apparatus (Umbiflow) between 28 and 32 weeks’ gestation. When a raised RI was detected, the mother was referred to a high-risk clinic and managed according to a standard protocol. A cohort analytical study compared women who attended antenatal care at the same clinics as the Umbiflow group but did not have an Umbiflow test with those who had an Umbiflow test. The outcomes of all the deliveries in Mamelodi were recorded. The prevalences of abnormal RIs, absent end-diastolic flow (AEDF), stillbirths and neonatal deaths were the main outcome measures.Results. An Umbiflow RI was performed in 2 868 women, and pregnancy outcome was available for 2 539 fetuses (88.5%); 297 fetuses (11.7%) were regarded as at high risk. AEDF was found in 1.5% of the population screened with an outcome. There were 29 perinatal deaths in the Umbiflow group (low risk n=18, high risk n=11). The perinatal mortality rate for 12 168 women attending the CHCs and the antenatal clinics draining to the CHCs who did not have an RI was 21.3/1 000 births, significantly higher than that in the Umbiflow group (11.4/1 000 births) (risk ratio 0.58, 95% confidence interval 0.42 - 0.81).Conclusions. The prevalence of AEDF in this low-risk population is ~10 times higher than that previously recorded. Use of the information prevented a number of perinatal deaths, most of which would have been macerated stillbirths. Screening a low-risk pregnant population using continuous-wave Doppler ultrasound may substantially reduce the prevalence of unexplained stillbirths in SA.

    Ability of SP12 mutant of S. typhi to effectively induce antibody responses to the mucosal antigen enterotoxigenic E. coli heat labile toxin B subunit after oral delivery to humans

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    We have evaluated an oral vaccine based on an Salmonella enteric serovar typhi (S. typhi) Ty2 derivative TSB7 harboring deletion mutations in ssaV (SPI-2) and aroC together with a chromosomally integrated copy of eltB encoding the B subunit of enterotoxigenic Escherichia coli heat labile toxin (LT-B) in volunteers. Two oral doses of 108 or 109 CFU were administered to two groups of volunteers and both doses were well tolerated, with no vaccinemia, and only transient stool shedding. Immune responses to LT-B and S. typhi lipopolysaccharide were demonstrated in 67 and 97% of subjects, respectively, without evidence of anti-carrier immunity preventing boosting of LT-B responses in many cases. Further development of this salmonella-based (spi-VEC) system for oral delivery of heterologous antigens appears warranted

    Covert Tracking: A Combined ERP and Fixational Eye Movement Study

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    Attention can be directed to particular spatial locations, or to objects that appear at anticipated points in time. While most work has focused on spatial or temporal attention in isolation, we investigated covert tracking of smoothly moving objects, which requires continuous coordination of both. We tested two propositions about the neural and cognitive basis of this operation: first that covert tracking is a right hemisphere function, and second that pre-motor components of the oculomotor system are responsible for driving covert spatial attention during tracking. We simultaneously recorded event related potentials (ERPs) and eye position while participants covertly tracked dots that moved leftward or rightward at 12 or 20°/s. ERPs were sensitive to the direction of target motion. Topographic development in the leftward motion was a mirror image of the rightward motion, suggesting that both hemispheres contribute equally to covert tracking. Small shifts in eye position were also lateralized according to the direction of target motion, implying covert activation of the oculomotor system. The data addresses two outstanding questions about the nature of visuospatial tracking. First, covert tracking is reliant upon a symmetrical frontoparietal attentional system, rather than being right lateralized. Second, this same system controls both pursuit eye movements and covert tracking

    PEPtalk2: results of a pilot randomised controlled trial to compare VZIG and aciclovir as postexposure prophylaxis (PEP) against chickenpox in children with cancer.

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    OBJECTIVE: To determine the likely rate of patient randomisation and to facilitate sample size calculation for a full-scale phase III trial of varicella zoster immunoglobulin (VZIG) and aciclovir as postexposure prophylaxis against chickenpox in children with cancer. DESIGN: Multicentre pilot randomised controlled trial of VZIG and oral aciclovir. SETTING: England, UK. PATIENTS: Children under 16 years of age with a diagnosis of cancer: currently or within 6 months of receiving cancer treatment and with negative varicella zoster virus (VZV) serostatus at diagnosis or within the last 3 months. INTERVENTIONS: Study participants who have a significant VZV exposure were randomised to receive PEP in the form of VZIG or aciclovir after the exposure. MAIN OUTCOME MEASURES: Number of patients registered and randomised within 12 months of the trial opening to recruitment and incidence of breakthrough varicella. RESULTS: The study opened in six sites over a 13-month period. 482 patients were screened for eligibility, 32 patients were registered and 3 patients were randomised following VZV exposure. All three were randomised to receive aciclovir and there were no cases of breakthrough varicella. CONCLUSIONS: Given the limited recruitment to the PEPtalk2 pilot, it is unlikely that the necessary sample size would be achievable using this strategy in a full-scale trial. The study identified factors that could be used to modify the design of a definitive trial but other options for defining the best means to protect such children against VZV should be explored. TRIAL REGISTRATION NUMBER: ISRCTN48257441, EudraCT number: 2013-001332-22, sponsor: University of Birmingham

    Adaptable Categorization of Hands and Tools in Prosthesis Users.

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    Some theories propose that tools become incorporated into the neural representation of the hands (a process known as tool embodiment; Maravita & Iriki, 2004). Others suggest that conceptual body representation is rigid and that experience with one’s own body is insufficient for adapting bodily cognition, as shown in individuals born without hands (Vannuscorps & Caramazza, 2016) and in amputees with persistent phantom hand representation (Kikkert et al., 2016). How sharp is the conceptual boundary between hands and tools? This question is particularly relevant for individuals who have lost one hand and use prosthetic hands as tools to supplement their missing hand function. Although both congenital one-handers (i.e., amelia patients) and one-handed amputees are encouraged to use prostheses, the former show a greater tendency than the latter to use prosthetic hands in daily tasks (Jang et al., 2011). One-handers have a fully functional remaining hand (allowing them to use handheld tools, etc.), which makes them less likely to show semantic distortions in hand and tool representation. However, their bodies and their interactions with their environment are fundamentally altered by their disability (Makin et al., 2013; Makin, Wilf, Schwartz, & Zohary, 2010). To determine how real-world experience shapes conceptual categorization of hands, tools, and prostheses, we recruited one-handers with congenital or acquired unilateral hand loss to take part in a study involving a priming task. We predicted that one-handers, particularly congenital one-handers, would show more conceptual blurring between hands and tools than control participants would, as a result of less experience with a hand and more reliance on prostheses (which are essentially tools) for typical hand functions. We further predicted that individual differences in prosthesis usage would be reflected in implicit categorization of hands, manual tools, and prostheses

    Generic Mechanism of Emergence of Amyloid Protofilaments from Disordered Oligomeric aggregates

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    The presence of oligomeric aggregates, which is often observed during the process of amyloid formation, has recently attracted much attention since it has been associated with neurodegenerative conditions such as Alzheimer's and Parkinson's diseases. We provide a description of a sequence-indepedent mechanism by which polypeptide chains aggregate by forming metastable oligomeric intermediate states prior to converting into fibrillar structures. Our results illustrate how the formation of ordered arrays of hydrogen bonds drives the formation of beta-sheets within the disordered oligomeric aggregates that form early under the effect of hydrophobic forces. Initially individual beta-sheets form with random orientations, which subsequently tend to align into protofilaments as their lengths increases. Our results suggest that amyloid aggregation represents an example of the Ostwald step rule of first order phase transitions by showing that ordered cross-beta structures emerge preferentially from disordered compact dynamical intermediate assemblies.Comment: 14 pages, 4 figure
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