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Clay minerals are one of the most difficult classes of materials to analyze by x-ray powder diffraction, yet powder diffraction is the only technique which can yield the important crystallographic information necessary to identify and classify the minerals. The importance of clay minerals in industry and in the studies of rocks, due to their chemical properties and sensitivity to geological changes, often requires the analyses of large numbers of samples in short periods of time. Such sample throughput requires computerized analysis* Because definitive, meaningful d-I data are difficult to obtain from the broad diffraction peaks obtained from most clay samples, this problem has been approached by using the whole diffraction, trace as the basis of a computerized analytical scheme.
Laser-based compact MeV X-ray sources are useful for a variety of applications such as radiography and active interrogation of nuclear materials. MeV X rays are typically generated by impinging the intense laser onto ~mm-thick high-Z foil. Here, we have characterized such a MeV X-ray source from 120 TW (80 J, 650 fs) laser interaction with a 1 mm-thick tantalum foil. Our measurements show X-ray temperature of 2.5 MeV, flux of 3 × 1012 photons/sr/shot, beam divergence of ~0.1 sr, conversion efficiency of ~1%, that is, ~1 J of MeV X rays out of 80 J incident laser, and source size of 80 m. Our measurement also shows that MeV X-ray yield and temperature is largely insensitive to nanosecond laser contrasts up to 10−5. Also, preliminary measurements of similar MeV X-ray source using a double-foil scheme, where the laser-driven hot electrons from a thin foil undergoing relativistic transparency impinging onto a second high-Z converter foil separated by 50–400 m, show MeV X-ray yield more than an order of magnitude lower compared with the single-foil results.
A novel synthesis of Al (1xxx)/carbonised coconut shell (CCS) nanoparticles using a ball milling technique was investigated. Initial Al/0.1%CCS powders of an average size of 51.06μm was milled for a period of 70 h. The milled particles at 16, 46 and 70 h were characterized using X-ray diffractomer (XRD), scanning electron microscope (SEM), transmission electron microscope and UV-Vis spectrophotometer. Result revealed that the calculated particle crystallite size from XRD aided with Scherrer’s equation is consistent with particle image sizes obtained from SEM aided with software. TEM image depicted variation in orientation and appearance of the Al 1xxx/0.1% CCS nanoparticles at different milling time. The wide variation in the particle size is attributable to different ball impacts on the individual powders during the ball milling process. Increased maximum absorbance observed with the milled particles when compared with the initial powders is an indication of quantum/nanosizing effect due to ball milling.
For this study, we adapted the Montgomery Borgatta Caregiver Burden Scale, used widely in the United States, to the Saudi Arabian context. To produce an Arabic, culturally sensitive version of the scale, we conducted semi-structured interviews with 20 Saudi family caregivers. The Arabic version of the scale was tested, and participants were asked to comment on the appropriateness of items for the construct of “caregiver burden” using the repertory grid technique and laddering procedure – two constructivist methods derived from personal construct theory. From interview findings, we examined the content of the items and the caregiver burden construct itself. Our findings suggest that the use of constructivist methods to refine constructs and quantitative instruments is highly informative. This strategy is feasible even when little is known about the investigated constructs in the target culture and further elucidates our understanding of cross-cultural variations or invariance of different versions of the scale.
Previous research suggests that the experience of abuse and neglect in childhood has negative implications for physical health in adulthood. Using data from the Minnesota Longitudinal Study of Risk and Adaptation (N = 115), the present research examined the predictive significance of childhood physical abuse, sexual abuse, and physical/cognitive neglect for multilevel assessments of physical health at midlife (age 37–39 years), including biomarkers of cardiometabolic risk, self-reports of quality of health, and a number of health problems. Analyses revealed that childhood physical/cognitive neglect, but not physical or sexual abuse, predicted all three health outcomes in middle adulthood, even when controlling for demographic risk factors and adult health maintenance behaviors. We discuss possible explanations for the unique significance of neglect in this study and suggest future research that could clarify previous findings regarding the differential impact of different types of abuse and neglect on adult health.
Six radio telescopes were operated as the first southern hemisphere VLBI array in April and May 1982. Observations were made at 2.3 and 8.4 Ghz. This array produced VLBI images of 28 southern hemisphere radio sources, high accuracy VLBI geodesy between southern hemisphere sites, and subarcsecond radio astrometry of celestial sources south of declination −45 degrees. This paper discusses only the astrophysical aspects of the experiment.
This paper discusses the evolution of coastal currents by considering, relative to a rotating frame, the flow development when buoyant fluid is injected into a quiescent fluid bounded by a solid wall. The initial rapid response is determined by the Coriolis force–pressure gradient balance with a Kelvin wave propagating rapidly, at the long-wave speed, with the bounding wall to its right (for positive rotation). However fluid columns can stretch or squash on ejection from coastal outflows so that the ejected fluid gains positive or negative relative vorticity. Depending on its sign, the image in the solid wall of this vorticity can reinforce or oppose the zero potential-vorticity-anomaly (PVa) current set up by the Kelvin wave (KW). This paper presents a simple, fully nonlinear, dispersive, quasi-geostrophic model to discuss the form of coastal outflows as the relative strength of vortex to KW driving is varied. The model retains sufficient physics to capture both effects at finite amplitude and thus the essential nonlinearity of the flow, but is sufficiently simple so as to allow highly accurate numerical integration of the full problem and also explicit, fully nonlinear solutions for the evolution of a uniform PVa outflow in the hydraulic limit. Outflow evolutions are shown to depend strongly on the sign of the PVa of the expelled fluid, which determines whether the vortex and KW driving are reinforcing or opposing, and on the ratio of the internal Rossby radius to the vortex-source scale,
, of the flow (where
measures the outflow depth,
the PVa of the outflow and
the volume flux of the outflow), which measures the relative strengths of the two drivers. Comparison of the explicit hydraulic solutions with the numerical integrations shows that the analytical solutions predict the flow development well with differences ascribable to dispersive Rossby waves on the current boundary and changes in the source region captured by the full equations but not present in the hydraulic solutions.
The short-range diurnal dispersal pattern of adult western flower thrips Frankliniella occidentalis (Pergande), in relation to spatial distribution of French beans, was determined in the field. A total of 1200 adult female F. occidentalis were released on 60 French bean plants with 20 adult thrips per plant at the central release point of 3.14 m2. Dispersal was determined in terms of the number of thrips recorded on French beans planted on concentric circles at 0.9, 1.8, 3.6, 7.2 and 14.4 m radii from a circular central release point for five days. Results indicated that there was a steady increase in the proportion of dispersing adult F. occidentalis from the first to the fourth day in the first planting season, and from the first to the third day in the second planting season. The peak hour for dispersal was 10.15 h in the first season while it was 13.15 h in the second season. Temperature and wind speed were positively associated with the dispersal activity of adult F. occidentalis. Minimal flight activity was at temperatures below 15 °C and peak flight activity was at 19 °C. The prevailing wind direction did not influence the dispersal pattern of adult F. occidentalis in both seasons. Adult F. occidentalis moved up to 7.2 m on French beans on the first day. In both seasons, the mean direction of thrips dispersal was mostly uniformly distributed (not oriented to a particular compass direction) around the central release point. The results provide an insight into developing integrated management strategies against the pest based on isolation of farm fields, management of alterative hosts around French bean fields and insecticide application.
Traditional and advanced magnetic resonance imaging techniques are often unable to differentiate progressive central nervous system neoplasm from post-treatment radiation effect (PTRE). 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) with delayed imaging has been shown to increase the specificity of PET imaging for cerebral neoplasm in small studies. We sought to further evaluate the potential diagnostic benefits of delayed imaging at 5 hours versus standard imaging at 1 hour to differentiate progressive disease (PD) from PTRE in patients with primary or metastatic brain tumors treated with radiation therapy.
Ten patients with primary (n=4) and metastatic (n=6) brain tumors were identified, with diagnostic confirmation of PD or PTRE provided by pathology or>3 month clinical and radiographic follow-up. Maximum standard uptake values (SUV) were calculated for suspicious areas of abnormal contrast enhancement (lesion) and compared to contralateral normal appearing brain (background) at both early and delayed time points. Seven patients were classified as having PD and 3 as having PTRE based pathology or clinical/radiographic follow up. The average lesion to background ratio (L/B) at the early time point (1.16+0.50) was significantly different than L/B for the later time point (1.72+1.10), p=0.030. The mean L/B for PD was 2.17+1.01 at the later time point compared to 0.65+0.06 for PTRE (p=0.010). For the earlier time point, L/B for PD was 1.40+0.42, compared to the L/B for PTRE which was 0.61+0.10 (p=0.003).L/B ratios at early and delayed time points successfully differentiated between patients with PD and PTRE, with significantly greater L/B ratios seen at delayed time points. These initial results are promising and further investigation is underway to evaluate the contribution of delayed imaging in differentiating PD from PTRE.
From June 15 to 28, 1991 the Compton Gamma-Ray Observatory (CGRO) observed the radio-loud quasar 3C 273. All four CGRO instruments detected radiation from this quasar in their relevant energy range (from 20 keV to 5 GeV). Simultaneous and quasi-simultaneous observations (spanning the time period May 27 – July 25, 1991) by instruments sensitive at other wavelengths have also been obtained. The data from all these observations spanning the frequency range from ∼ 109 Hz to ∼ 1026 Hz were collected and analysed. The resulting energy-density spectrum is shown in the figure below. It shows two maxima, one in the UV, another one at low-energy γ-rays which have nearly the same strength (the corresponding luminosities per decade of frequency for H0 = 60(km/s)/Mpc are 3.2·1046 erg/s and 2.7·1046 erg/s, respectively). A break of the spectrum at low-energy γ-rays is evident. From a detailed analysis a break energy of (2±1.5) MeV could be derived corresponding to a frequency of (4.8±3.6)·1020 Hz. The observed spectral break between X- and γ-rays is ∼ 0.8, much higher than the value of 0.5 predicted by some models. A more detailed paper on this topic is in preparation (Lichti et al.).
To define how often methicillin-resistant Staphylococcus aureus (MRSA) is spread from resident to resident in long-term care facilities using whole-genome sequencing
Prospective cohort study
A long-term care facility
Elderly residents in a long-term care facility
Cultures for MRSA were obtained weekly from multiple body sites from residents with known MRSA colonization over 12-week study periods. Simultaneously, cultures to detect MRSA acquisition were obtained weekly from 2 body sites in residents without known MRSA colonization. During the first 12-week cycle on a single unit, we sequenced 8 MRSA isolates per swab for 2 body sites from each of 6 residents. During the second 12-week cycle, we sequenced 30 MRSA isolates from 13 residents with known MRSA colonization and 3 residents who had acquired MRSA colonization.
MRSA isolates from the same swab showed little genetic variation between isolates with the exception of isolates from wounds. The genetic variation of isolates between body sites on an individual was greater than that within a single body site with the exception of 1 sample, which had 2 unrelated strains among the 8 isolates. In the second cycle, 10 of 16 residents colonized with MRSA (63%) shared 1 of 3 closely related strains. Of the 3 residents with newly acquired MRSA, 2 residents harbored isolates that were members of these clusters.
Point prevalence surveys with whole-genome sequencing of MRSA isolates may detect resident-to-resident transmission more accurately than routine surveillance cultures for MRSA in long-term care facilities.
Whether genetic factors influence the associations of fatty acids with the risk of sudden cardiac arrest (SCA) is largely unknown. To investigate possible gene–fatty acid interactions on SCA risk, we used a case-only approach and measured fatty acids in erythrocyte samples from 1869 SCA cases in a population-based repository with genetic data. We selected 191 SNP in ENCODE-identified regulatory regions of fifty-five candidate genes in fatty acid metabolic pathways. Using linear regression and additive genetic models, we investigated the association of the selected SNP with erythrocyte levels of fatty acids, including DHA, EPA and trans-fatty acids among the SCA cases. The assumption of no association in non-cases was supported by analysis of publicly available datasets containing over 8000 samples. None of the SNP–fatty acid associations tested among the cases reached statistical significance after correction for multiple comparisons. One SNP, rs4654990 near PLA2G2A, with an allele frequency of 0·33, was nominally associated with lower levels of DHA and EPA and higher levels of trans-fatty acids. The strongest association was with DHA levels (exponentiated coefficient for one unit (1 % of total fatty acids), 0·90, 95 % CI 0·85, 0·97; P = 0·003), indicating that for subjects with a coded allele, the OR of SCA associated with one unit higher DHA is about 90 % what it is for subjects with one fewer coded allele. These findings suggest that the associations of circulating n-3 and trans-fatty acids with SCA risk may be more pronounced in carriers of the rs4654990 G allele.
Linearly polarized SiO emission spread over 12 km/s has been detected from the star R Leo. The position angle of polarized emission varies systematically with respect to the spectral line center. Interpreted in terms of radiative transfer theory, this change in position angle may be due to magnetorotation, which allows the determination of the magnetic field (9×10−3/cos θ Gauss), and the SiO systemic velocity (−1 ± 2 km/s).
AlGaN/GaN High Electron Mobility Transistors were exposed to 60Co gamma-irradiation to doses up to 300Gy. The impact of Compton- electron injection (due to gamma-irradiation) is studied through monitoring of minority carrier transport using Electron Beam Induced Current (EBIC) technique. Temperature dependent EBIC measurements were conducted on devices before and after exposure to the irradiation, which provide us with critical information on gamma-irradiation induced defects in the material. As a result of irradiation, minority carrier diffusion length increases significantly, with an accompanying decrease in the activation energy. This is consistent with the longer life time of minority carrier in the material’s valence band as a result of an internal electron injection and subsequent trapping of Compton electrons on neutral levels.