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The purpose of the present paper is to give a comprehensive state of the art review of all electro-optical systems used to date for direct viewing of X-ray topographic images. Consideration is given to both direct conversion X-ray sensitive vidicon systems and to indirect conversion systems which use fluorescent screens to convert the X-ray image into a visible one. Included in this review is a discussion of the relative advantages and disadvantages of the various electro-optical systems, including cost, versatility, portability, simplicity of operation, sensitivity, and resolution capability.
High-temperature x-ray diffraction has many applications. Applied to polymeric materials it is a useful tool for investigating changes in crystallinity, providing insight into molding and extrusion problems, and for examining solvent-resistancy problems. An example of the increasing crystailine character of a polymer as a function of temperature can be seen in figure 1. Diffraction scans at 25°C, 100°C, 150°C, and 200°C clearly show the increasing crystalline character of the potymer with an increase in temperature. Control of sample temperature for a polymer is very important, when analyzing under air, because a momentary overshoot in temperature may lead to the sample igniting. High-temperature investigations of polymers are also subject to the problem of the sample warping and bowing.
An X-ray/Laser technique is described for producing Laue patterns on very small (1mm2) crystal surfaces where it is otherwise not possible to mechanically align the surface of the crystal perpendicular to an X-ray beam. This technique has been used to determine the orientation of the diamond inserts in cutting tool bits.
In order to develop an optimum system for flash x-ray diffraction, consideration must be given to both optimum x-ray generation and optimum x-ray detection in the correct wavelength regime suitable for diffraction. Historically, most workers have concentrated their efforts in either the generation area or detection area, but not both. As early as 1942, experimental recording of Laue diffraction patterns was reported using a pulsed x-ray generator and exposure times of milliseconds. Recently, successful x-ray diffraction experiments have been reported with exposure times less than 100 nanoseconds.
The purpose of the present paper is to trace the development of generation and detection systems for flash x-ray diffraction and to summarize the present state-of-the-art for such systems. A comparative evaluation is presented for flash x-ray diffraction systems using generators which rely on increased electron beam current and those which rely on higher potential difference. Comparison is also made between detection systems incorporating film recording, scintillators fiber-optically coupled to photomultiplier tubes, and image-intensifier systems both lens and fiber-optically coupled to fluorescent screens.
A detailed description of the most rapid flash x-ray diffraction system developed to date is given. This system uses a Field Emission Fexitron single channel 300 kilovolt pulsed x-ray generator incorporating an x-ray tube with a beryllium output window. A fluorescent screen converts the x-ray diffraction image into a visible one and this visible image is focused on the first stage photocathode of an image intensifier tube either by direct fiber-optic coupling or by using a coupling lens. The image intensifier tube used is a cascaded three-stage electrostatic focus type with fiber-optic input and output faceplates and inter-stage couplers. Using this system Laue transmission diffraction patterns of single crystals and powder patterns of polycrystalline aggregates have been obtained with exposure times of 30 nanoseconds.
Considerable work has been undertaken in order to gain an understanding of the mechanisms responsible for the generation of recrystallization textures developed upon annealing of cold-worked metals. Most direct measurements have consisted of measuring the increase in average diameter of the largest grain growing into a polycrystalline aggregate. Experimental measurements of individual boundaries migrating into deformed single crystals, though of a more fundamental nature, have been made by far fewer investigators. This is probably due to the increased experimental difficulties associated with careful control of such experiments. Most previous investigators have made grain boundary migration measurements by the heat-cool-etch method, despite the fact that it has several marked disadvantages. Other investigators have constructed an X-ray goniometer furnace and used it to measure grain boundary migration rates while the test specimen was maintained at temperature. Since there have been no published reports of the use of such a system in the past thirteen years, it must be concluded that the technique was unsuccessful in general.
The system described in the present work is relatively simple in design and extremely simple to use. Not only does it permit absolute measurement of grain boundary position at temperature but it also permits boundary migration measurements to be made of extremely fast moving boundaries. The basic components of the system are as follows. A continuous spectrum X-ray beam is converted by a slit collimating system into a beam which is incident along the entire length of the test specimen. This beam is interrupted by a wire grid just prior to impingement on the test specimen. The test specimen is supported vertically in a furnace maintained at the temperature required for grain boundary migration. The various diffracted X-ray beams pass out of the furnace through a highly reflecting insulating baffle made from very thin aluminum foil and impinge on a fluorescent screen. This screen converts the X-ray image into a visible one which is amplified and recorded using the electro-optical system.
X-ray characterization of single crystal materials in the form of thin layers can be accomplished with the use of a double crystal diffractometer. The resultant rocking curve is a convolution of the Bragg reflection from both the first and second crystals. The width of the rocking curve at half-height is a measure of the crystal perfection of a materiel. Since the FWHM for the material being analyzed cannot be less than that of the first crystal (Monochromator), the first crystal should be of very good crystal quality. The problem that arises with the two crystal parallel configuration (Fig. 1) is that the monochromator crystal must be changed each time a material of different orientation or stoichiometry with different resultant lattice constants is analyzed. This requires changing the monochromator and re-aligning the double crystal diffractometer.
Synchrotron white beam transmission topography of GaAs as previously reported by the authors relied on scanning specimen and film synchronously through the incident x-ray beam to record transmission topographic images en film. Sometimes the total dose required for reasonable contrast on film carried with it enough thermal deposition to cause elastic warping of the wafer. To escape these problems, a real time system was assembled. This system included an image intensifier, a solid state camera, a computer board to frame-grab and digitize images, and appropriate image processing software. With this system, a three inch specimen was scanned from edge to edge in one minute. At this scan rate, the incident x-ray beam had to be significantly attenuated to avoid saturating the intensifier output.
Various electro-optical systems have been reported which permit intensification of X-ray diffraction patterns and thus a decrease in exposure time for recording and display of the X-ray images. Prior to 1966, all such electro-optical systems incorporated a large format X-ray image intensifier of the same type as conventionally used for medical and industrial fluoroscopy. In the past four years, a number of different systems have been reported which are superior to those developed prior to 1966. These systems may be grouped into two main categories, the large format variety for Laue diffraction applications, and the small format variety for topographic applications.
The purpose of the present paper is to describe the particular characteristics of both the large format and small format systems and to discuss the advantages and disadvantages associated with each type. Based on actual performance characteristics it will be shown that:
1.A multiple stage image intensifier system coupled to an external fluorescent screen is the most sensitive and only truly instantaneous system; it can be used with very weak X-ray intensities, the resolution is currently limited by the external fluorescent screen to 42μ the system is extremely versatile in that it can be used both for large format recording of Laue patterns as well as for small format recording of X-ray topographe; the system has a very long lifetime since nothing is altered by X-radiation.
2.An X-ray sensitive vidicon is the least sensitive; it must be used with extremely high intensity X-rays or long exposure times; the resolution is the highest at approximately 15μ and is limited by either bandwidth of the television system, the thickness of the X-ray sensitive target or the size of the electron beam at the target; due to the small size of the X-ray sensitive target the system can only be used for small format recording of X-ray topographs; the lifetime of the system is short since X-radiation causes degradation of the target.
To determine the rate of recurrent major trauma (i.e., trauma recidivism) using a provincial population-based trauma registry. We compared outcomes between recidivists and non-recidivists, and assessed factors associated with recidivism and mortality.
Review of all adult (>17 years) major trauma patients in Nova Scotia (2001–2015) using data from the Nova Scotia Trauma Registry. Outcomes of interest were mortality, duration of hospital stay, and in-hospital complications. Multiple regression was used to assess factors associated with recidivism and mortality.
Of 9,365 major trauma patients, 2% (150/9365) were recidivists. Mean age at initial injury was 52 ± 21.5 years; 73% were male. The mortality rate for both recidivists and non-recidivists was 31%. However, after adjusting for potential confounders the likelihood of mortality was over 3 times greater for recidivists compared to non-recidivists (OR 3.67, 95% CI 2.06–6.54). Other factors associated with mortality included age, male gender, penetrating injury, Injury Severity Score, trauma team activation (TTA) and admission to the intensive care unit. The only variables associated with recidivism were age (OR 0.98, 95% CI 0.97–1.00) and TTA (OR 0.59, 95% CI 0.34–0.96).
This is the first provincial investigation of major trauma recidivism in Canada. While recidivism was infrequent (2%), the adjusted odds of mortality were over three times greater for recidivists. Further research is warranted to determine the effectiveness of strategies for reducing rates of major trauma recidivism such as screening and brief intervention in cases of violence or substance abuse.
Despite the significant health benefits of breastfeeding for the mother and the infant, economic class and race disparities in breastfeeding rates persist. Support for breastfeeding from the father of the infant is associated with higher rates of breastfeeding initiation. However, little is known about the factors that may promote or deter father support of breastfeeding, especially in fathers exposed to contextual adversity such as poverty and violence. Using a mixed methods approach, the primary aims of the current work were to (1) elicit, using qualitative methodology, the worries, barriers and promotive factors for breastfeeding that expectant mothers and fathers identify as they prepare to parent a new infant, and (2) to examine factors that influence the parental breastfeeding intentions of both mothers and fathers using quantitative methodology. A sample (N=95) of expectant, third trimester mothers and fathers living in a low-income, urban environment in Midwestern USA, were interviewed from October 2013 to February 2015 about their infant feeding intentions. Compared with fathers, mothers more often identified the benefits of breastfeeding for the infant’s health and the economic advantage of breastfeeding. Mothers also identified more personal and community breastfeeding support resources. Fathers viewed their own support of breastfeeding as important but expressed a lack of knowledge about the breastfeeding process and often excluded themselves from discussions about infant feeding. The results point to important targets for interventions that aim to increase breastfeeding initiation rates in vulnerable populations in the US by increasing father support for breastfeeding.
The objective of this study was to systematically review the published literature for risk factors associated with adverse outcomes in older adults sustaining blunt chest trauma.
EMBASE and MEDLINE were searched from inception until March 2017 for prognostic factors associated with adverse outcomes in older adults sustaining blunt chest trauma using a pre-specified search strategy. References were independently screened for inclusion by two reviewers. Study quality was assessed using the Quality in Prognostic Studies tool. Where appropriate, descriptive statistics were used to evaluate study characteristics and predictors of adverse outcomes.
Thirteen cohort studies representing 79,313 patients satisfied our selection criteria. Overall, 26 prognostic factors were examined across studies and were reported for morbidity (8 studies), length of stay (7 studies), mortality (6 studies), and loss of independence (1 study). No studies examined patient quality of life or emergency department recidivism. Prognostic factors associated with morbidity and mortality included age, number of rib fractures, and injury severity score. Although age and rib fractures were found to be associated with adverse outcomes in more than 3 studies, meta-analysis was not performed due to heterogeneity amongst included studies in how these variables were measured.
While blunt chest wall trauma in older adults is relatively common, the literature on prognostic factors for adverse outcomes in this patient population remains inadequate due to a paucity of high quality studies and lack of consistent reporting standards.
To integrate electronic clinical decision support tools into clinical practice and to evaluate the impact on indwelling urinary catheter (IUC) use and catheter-associated urinary tract infections (CAUTIs).
Design, Setting, and Participants
This 4-phase observational study included all inpatients at a multicampus, academic medical center between 2011 and 2015.
Phase 1 comprised best practices training and standardization of electronic documentation. Phase 2 comprised real-time electronic tracking of IUC duration. In phase 3, a triggered alert reminded clinicians of IUC duration. In phase 4, a new IUC order (1) introduced automated order expiration and (2) required consideration of alternatives and selection of an appropriate indication.
Overall, 2,121 CAUTIs, 179,070 new catheters, 643,055 catheter days, and 2,186 reinsertions occurred in 3·85 million hospitalized patient days during the study period. The CAUTI rate per 10,000 patient days decreased incrementally in each phase from 9·06 in phase 1 to 1·65 in phase 4 (relative risk [RR], 0·182; 95% confidence interval [CI], 0·153–0·216; P<·001). New catheters per 1,000 patient days declined from 53·4 in phase 1 to 39·5 in phase 4 (RR, 0·740; 95% CI, 0·730; P<·001), and catheter days per 1,000 patient days decreased from 194·5 in phase 1 to 140·7 in phase 4 (RR, 0·723; 95% CI, 0·719–0·728; P<·001). The reinsertion rate declined from 3·66% in phase 1 to 3·25% in phase 4 (RR, 0·894; 95% CI, 0·834–0·959; P=·0017).
The phased introduction of decision support tools was associated with progressive declines in new catheters, total catheter days, and CAUTIs. Clinical decision support tools offer a viable and scalable intervention to target hospital-wide IUC use and hold promise for other quality improvement initiatives.
Two spectral snow-reflectance models that account for the effects of grain-size and liquid-water fraction are described and initial validation results presented. The models are based upon the spectral complex refractive index of liquid water and ice in the region from 400 to 2500 nm. Mie scattering calculations are used to specify the essential optical properties of snow in the models. Two approaches are explored to model the effect of liquid water in the snow. The first accounts for the liquid water as separate spheres interspersed with ice spheres in the snow layer. The second accounts for the liquid water as coatings on ice grains in the snow layer. A discrete-ordinate radiative transfer code is used to model the spectral reflectance of the snow for the Mie-calculated optical properties. Both the interspersed- and coated-sphere models show that the snow-absorption feature at 1030 nm shifts to shorter wavelength as the liquid-water content increased. The expression of these shifts is different for the two models. A comparison of the models with a spectral measurement of frozen and melting snow shows better agreement with the coated-sphere model. A spectral fitting algorithm was developed and tested with the coated-sphere model to derive the grain-size and liquid-water fraction from snow spectral reflectance measurements. Consistent values of grain-size and liquid water were retrieved from the measured snow spectra. This research demonstrates the use of spectral models and spectral measurements to derive surface snow grain-size and liquid-water fraction. The results of this research may be extended to regional and greater scales using data acquired by airborne and spaceborne imaging spectrometers for contributions to energy balance and hydrological modeling.
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.
While the use of formal trauma teams is widely promoted, the literature is not clear that this structure provides improved outcomes over emergency physician delivered trauma care. The goal of this investigation was to examine if a trauma team model with a formalized, specialty-based trauma team, with specific activation criteria and staff composition, performs differently than an emergency physician delivered model. Our primary outcome was survival to discharge or 30 days.
An observational registry-based study using aggregate data from both the New Brunswick and Nova Scotia trauma registries was performed with data from April 1, 2011 to March 31, 2013. Inclusion criteria included patients 16 years-old and older who had an Injury Severity Score greater than 12, who suffered a kinetic injury and arrived with signs of life to a level-1 trauma centre.
266 patients from the trauma team model and 111 from the emergency physician model were compared. No difference was found in the primary outcome of proportion of survival to discharge or 30 days between the two systems (0.88, n=266 vs. 0.89, n=111; p=0.8608).
We were unable to detect any difference in survival between a trauma team and an emergency physician delivered model.
Trauma systems have been widely implemented across Canada, but access to trauma care remains a challenge for much of the population. This study aims to develop and validate a model to quantify the accessibility of definitive care within one provincial trauma system and identify populations with poor access to trauma care.
A geographic information system (GIS) was used to generate models of pre-scene and post-scene intervals, respectively. Models were validated using a population-based trauma registry containing data on prehospital time intervals and injury locations for Nova Scotia (NS). Validated models were then applied to describe the population-level accessibility of trauma care for the NS population as well as a cohort of patients injured in motor vehicle collisions (MVCs).
Predicted post-scene intervals were found to be highly correlated with documented post-scene intervals (β 1.05, p<0.001). Using the model, it was found that 88.1% and 42.7% of the population had access to Level III and Level I trauma care within 60 minutes of prehospital time from their residence, respectively. Access for victims of MVCs was lower, with 84.3% and 29.7% of the cohort having access to Level III and Level I trauma care within 60 minutes of the location of injury, respectively.
GIS models can be used to identify populations with poor access to care and inform service planning in Canada. Although only 43% of the provincial population has access to Level I care within 60 minutes, the majority of the population of NS has access to Level III trauma care.