To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure firstname.lastname@example.org
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Population-based registries report 95% 5-year survival for children undergoing surgery for CHD. This study investigated paediatric cardiac surgical outcomes in the Australian indigenous population.
All children who underwent cardiac surgery between May, 2008 and August, 2014 were studied. Demographic information including socio-economic status, diagnoses and co-morbidities, and treatment and outcome data were collected at time of surgery and at last follow-up.
A total of 1528 children with a mean age 3.4±4.6 years were studied. Among them, 123 (8.1%) children were identified as indigenous, and 52.7% (62) of indigenous patients were in the lowest third of the socio-economic index compared with 28.2% (456) of non-indigenous patients (p⩽0.001). The indigenous sample had a significantly higher Comprehensive Aristotle Complexity score (indigenous 9.4±4.2 versus non-indigenous 8.7±3.9, p=0.04). The probability of having long-term follow-up did not differ between groups (indigenous 93.8% versus non-indigenous 95.6%, p=0.17). No difference was noted in 30-day mortality (indigenous 3.2% versus non-indigenous 1.4%, p=0.13). The 6-year survival for the entire cohort was 95.9%. The Cox survival analysis demonstrated higher 6-year mortality in the indigenous group – indigenous 8.1% versus non-indigenous 5.0%; hazard ratio (HR)=2.1; 95% confidence intervals (CI): 1.1, 4.2; p=0.03. Freedom from surgical re-intervention was 79%, and was not significantly associated with the indigenous status (HR=1.4; 95% CI: 0.9, 1.9; p=0.11). When long-term survival was adjusted for the Comprehensive Aristotle Complexity score, no difference in outcomes between the populations was demonstrated (HR=1.6; 95% CI: 0.8, 3.2; p=0.19).
The indigenous population experienced higher late mortality. This apparent relationship is explained by increased patient complexity, which may reflect negative social and environmental factors.
NASA's Program for Arctic Regional Climate Assessment (PARCA) includes measurements of ice velocity and ice thickness along the 2000 m elevation contour line in the western part of the ice sheet. Here we use these measurements together with published estimates of snow-accumulation rates to infer die mass balance, or rate of thickening/thinning, of the ice-sheet catchment area inland from the velocity traverse. Within the accuracy to which we know snow-accumulation rates, the entire area is in balance, but localized regions inland from Upernavik Isstrom and Jakobshavn Isbra both appear to be thickening by about 10 cm a-1.
We present a status report of the accelerator mass spectrometry (AMS) facility at the University of California, Irvine, USA. Recent spectrometer upgrades and repairs are discussed. Modifications to preparation laboratory procedures designed to improve sample throughput efficiency while maintaining precision of 2–3‰ for 1-mg samples (Santos et al. 2007c) are presented.
For very small samples, it is difficult to prepare graphitic targets that will yield a useful and steady sputtered ion beam. Working with materials separated by preparative capillary gas chromatography, we have succeeded with amounts as small as 20 μg C. This seems to be a practical limit, as it involves 1) multiple chromatographic runs with trapping of effluent fractions, 2) recovery and combustion of the fractions, 3) graphitization and 4) compression of the resultant graphite/cobalt matrix into a good sputter target. Through such slow and intricate work, radiocarbon ages of lignin derivatives and hydrocarbons from coastal sediments have been determined. If this could be accomplished as an “online” measurement by flowing the analytes directly into a microwave gas ion source, with a carrier gas, then the number of processing steps could be minimized. Such a system would be useful not just for chromatographic effluents, but for any gaseous material, such as CO2 produced from carbonates. We describe tests using such an ion source.
We investigate the built-in voltage in organic bulk heterojunction solar cells using electroabsorption spectroscopy based on the Stark effect, i.e. the variation of the absorption energies of a material caused by an electric field. Due to spectral contributions of permanent dipoles, a novel approach for evaluating the EA spectra is required. We use a fitting routine analyzing a broad spectral range instead of using only a single wavelength. A reliable quantitative determination of the built-in voltage is achieved.
This work presents a study on the activation behavior of high-dose (φ > 1015 cm-2) boron and phosphorus implants for low resistance source and drain regions for thin-film transistors (TFTs) fabricated using solid-phase crystallization (SPC) of amorphous silicon. Process variables include factors associated with ion implant and annealing conditions, as well as the SPC and implant process arrangement. Four-point probe sheet resistance (Rs) measurements were used as a comprehensive assessment of the electrical properties. Results have identified similarities and differences in activation behavior that can influence process integration strategies considering both the SPC approach and TFT fabrication.
Electroluminescence (EL) and photoluminescence (PL) imaging and stressing techniques are presented that are useful characterization tools for SiC epitaxial layers grown for power devices. Both EL and PL techniques are non-destructive, and the PL imaging is non-contact. These features are important for qualifying epitaxial layers before subjecting the layers to the time-consuming and costly process of device fabrication. By imaging at various emission spectral bands, the spectral information are correlated to the geometric features in the images. This correlation enables the differentiation of dissimilar defects having similar geometric shapes. Row average plots of images at various emission spectral bands revealed that threading dislocations (TDs) have strong emission above 900 nm and that basal plane dislocations (BPDs) have a broad spectral emission that are most easily distinguished in the range between 738 nm and 870 nm. The correlation between spectral information and the image features clearly distinguished TDs and BPDs from other defects, such as, organic substance and other surface blemishes. In addition to identifying the defects, understanding their origin can be useful in developing low-defect growth techniques. The defect origination depth is one of the important information for understanding defect origin. Two schemes for determining the defect origination depth are presented. Varying the focus depth by adjusting the objective lens height is a crude but quick scheme. Stressing the epilayer to grow the BPDs till they reach the surface or the epilayer/substrate interface is more time-consuming but more accurate. The scheme of varying the focus was demonstrated using PL imaging on a 50-mm thick n- epilayer with no p+ anode layer. Adjusting the focus on a partial dislocation in the n- epilayer revealed segments of the partial coming more in focus near the epilayer/substrate interface, suggesting the defect origination depth was at or near the interface. The stress and growth scheme was demonstrated on a straight string of half loop defects in a 100-mm thick n- epilayer. During electrical stressing, BPDs emanated from the half loops and eventually propagated to the surface at a lateral distance of 250 mm. With the basal plane at an 8° offcut from the surface, the origin of the BPDs was calculated to be 35 mm below the surface, suggesting the defects to be introduced during the growth process. Either EL or PL technique can be used with any of these two schemes to determine the defect origination depth. However, the PL technique has the benefit that the p+ anode layer and the procedure for forming a metal grid are not required.
Here we present optical beam induced current, electroluminescence, time resolved photoluminescence and current-voltage measurements on several 4H-SiC PiN diodes containing in-grown stacking faults (IGSFs). These defects were observed to act as either current shorts, creating a direct electrical contact between the p+ and n+ layers, or as a current barrier. Carrier lifetime measurements verify that the change in behavior is indeed associated with changes in the conductivity of the material in the vicinity of the defect and not due to local changes in the carrier lifetime. The IGSFs discussed here appear to differ from those previously discussed in the literature and may constitute a new, multi-layered IGSF.
The forward voltage drop (Vf) increase observed in 4H-SiC bipolar devices such as pin diodes due to recombination-induced Shockley stacking fault (SSF) creation and expansion has been widely discussed in the literature. It was long believed that the deleterious affect of these defects was limited to bipolar devices. However, it was recently reported that forward biasing of the body diode of a 10kV 4H-SiC DMOSFET led to similar Vf increases in the body diode I-V curve as well as a corresponding degradation in the majority carrier conduction characteristics as well and this degradation was believed to be due to the creation and expansion of SSFs during the body diode forward biasing. Here we report measurements comparing the influence of similar stressing, along with annealing and current-induced recovery experiments in DMOSFETs and merged pin-Schottky diodes with the previously reported results of these experiments in 4H-SiC pin diodes. The results of these experiments provide sufficient support that the observed degradation in the majority carrier conduction characteristics is the result of SSF expansion.