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A model of a High Voltage CMOS (HV-CMOS) Monolithic Active Pixel Sensor (MAPS) has been modelled using Technology Computer Aided Design (TCAD). The model has incorporated both the active region and the on-pixel readout circuits which were comprised of a source follower amplifier and an integrated charge amplifier. The simulation has examined the electrical characteristics and response output of a HV-CMOS MAPS sensor using typical dimensions, levels of doping in the structural layers and bias conditions for this sensor. The performance of two alternate designs of amplifier have been examined as a function of the operating parameters. The response of the sensor to the incidence of Minimum Ionizing Particles (MIPs) at different energies has been included in the model.
Introduction: Patients with chronic diseases are known to benefit from exercise. Such patients often visit the emergency department (ED). There are few studies examining prescribing exercise in the ED. We wished to study if exercise prescription in the ED is feasible and effective. Methods: In this pilot prospective block randomized trial, patients in the control group received routine care, whereas the intervention group received a combined written and verbal prescription for moderate exercise (150 minutes/week). Both groups were followed up by phone at 2 months. The primary outcome was achieving 150 min of exercise per week. Secondary outcomes included change in exercise, and differences in reported median weekly exercise. Comparisons were made by Mann-Whitney and Fishers tests (GraphPad). Results: Follow-up was completed for 22 patients (11 Control; 11 Intervention). Baseline reported median (with IQR) weekly exercise was similar between groups; Control 0(0-0)min; Intervention 0(0-45)min. There was no difference between groups for the primary outcome of 150 min/week at 2 months (Control 3/11; Intervention 4/11, RR 1.33 (95%CI 0.38-4.6;p=1.0). There was a significant increase in median exercise from baseline in both groups, but no difference between the groups (Control 75(10-225)min; Intervention 120(52.5-150)min;NS). 3 control patients actually received exercise prescription as part of routine care. A post-hoc comparison of patients receiving intervention vs. no intervention, revealed an increase in patients meeting the primary target of 150min/week (No intervention 0/8; Intervention 7/14, RR 2.0 (95%CI 1.2-3.4);p=0.023). Conclusion: Recruitment was feasible, however our study was underpowered to quantify an estimated effect size. As a significant proportion of the control group received the intervention (as part of standard care), any potential measurable effect was diluted. The improvement seen in patients receiving intervention and the increase in reported exercise in both groups (possible Hawthorne effect) suggests that exercise prescription for ED patients may be beneficial.
Introduction: Point-of-care-ultrasound is an established tool in the early diagnosis of abdominal aortic aneurysm (AAA), with a reported pooled sensitivity of 97.5% and pooled specificity 98.9%. Despite these impressive numbers, body habitus and bowel gas often render emergency department (ED) PoCUS for AAA inconclusive. We devised a manual aid “the modified peace sign technique” to improve visualization of the aorta, consisting of placing the divided fingers of the free hand of the sonographer around the probe to increase gas dispersion and improve the view of the obscured aorta. We tested the technique on volunteers during a training course when the initial scan was indeterminate due to inability to view the aorta from sub-xiphoid to bifurcation. Methods: In our pilot study, 7 physicians were asked to make a best attempt to perform an aortic scan. If they were unable to visualize the aorta, they were asked to use the modified peace sign technique. Participants recorded the number of times which they used the technique and the frequency that the technique allowed for a complete aortic scan, previously unobtainable. All scans were supervised by certified PoCUS physicians. Results: The technique was used a total of 25 times. Following failure to complete an aortic scan using their best attempt, participants were subsequently able to obtain a complete aortic scan 70% (95% CI 48 to 83%) of the time using the modified peace sign technique. Conclusion: In our pilot study, the modified peace sign technique had an estimated effect size of 70% improvement for visualization of the aorta in volunteers. Further studies are required to validate the technique in clinical practice.
Introduction: The positive health outcomes of exercise have been well-studied, and exercise prescription has been shown to reduce morbidity in several chronic health conditions. However, patient attitudes around the prescription of exercise in the emergency department (ED) have not been explored. The aim of our pilot study is to explore patients’ willingness and perceptions of exercise being discussed and prescribed in the ED. Methods: This study is a survey of patients who had been previously selected for exercise prescription in a pilot study conducted at a tertiary care ED. This intervention group were given a standardized provincial written prescription to perform moderate exercise for 150 minutes per week. Participants answered a discharge questionnaire and were followed up by a telephone interview 2 months later. A structured interview of opinions around exercise prescription was conducted. Questions included a combination of non-closed style interview questions and Likert scale. Patients rated prescription detail, helpfulness and likelihood on a Likert scale from 1-5 (1 being strongly disagree and 5 being strongly agree). Median values (+/-IQRs) are presented, along with dominant themes. Results: 17 people consented to exercise prescription and follow up surveys. 2 were excluded due to hospital admission. 15 participants were enrolled and completed the discharge survey. Two-month follow up survey response rate was 80%. Patients rated the detail given in their prescription as 5 (+/-1). Helpfulness of prescription was rated as 4 (+/-2). Likelihood to continue exercising based on the prescription was rated as 4 (+/-2). 11/12 participants felt that exercise should be discussed in the Emergency Department either routinely or on a case-by-case basis.1 participant felt it should not be discussed at all. Conclusion: Our study demonstrates that most patients are open to exercise being discussed during their Emergency Department visit, and that the prescription format was well-received by study participants.
The electrical characteristics of Au/Ni/Ti/ n-SiC contacts have been examined as a function of implant dose (1013-1014 ions/cm2) at 5 KeV and temperature of annealing (750-1000 °C). Measurements of specific contact resistance, ρc, were approximately constant at lower implant doses until increasing at 1 x 1015 ions/cm2 for both C and P ions. Annealing at a temperature of 1000 °C has reduced the value of ρc by an order of magnitude to ∼1 x 10-6 Ω.cm2 at implant doses of 1013-1014 ions/cm2. Auger Electron Spectroscopy (AES) has shown that annealing at 1000 °C resulted in a strong indiffusion of the metallization layers at the interface.
We present low resolution spectrophotometric and imaging ISO observations of a sample of 58 AGN's over the 2.5–11.6 μ range. The data strongly support unification schemes and set new constraints on models of the molecular torus.
Finite element modelling has been used to optimise the current/ voltage (I/V) characteristics of metal/ n-SiC and metal/ n-Si diodes incorporating a thin interfacial layer. The electrical properties of the diodes have been examined in relation to the polytype of SiC (3H, 4H or 6C), the doping level, NA, (1015 - 1018cm3) of the substrate, the defect state density, Dit and the work function of the Schottky metal, Φm. The modelling by Technology Computer-Aided Design (TCAD) has shown that the presence of an interfacial insulating layer with a thickness of 1.0 nm has reduced the reverse leakage current of the diode by a factor of ∼102 in Si and 1013 (from 10-19 A to 10-6 A) for SiC with only a minor reduction (∼ 0.8 times) in the forward current in SiC. The properties of the diodes have been modelled at room temperature without thermal annealing.
Carbon films deposited by filtered cathodic vacuum arc have been used to form high quality Schottky diodes on p-Si. Energetic deposition with an applied substrate bias of -1 kV and with a substrate temperature of 100 °C has produced carbon diodes with rectification ratios of ∼ 3 × 106, saturation currents of ∼0.02 nA and ideality factors close to unity (n = 1.05). Simulations were used to estimate the effective work function and the thickness of an interfacial mixed (C/SiO2) layer from the current/voltage characteristics of the diodes.
The effect of low energy implantation of P or C ions in 3C-SiC on the properties of Ti/Ni/Au contacts has been examined for doses in the range 1013-1015 ions/cm2. Measurements of specific contact resistance, ρc, were performed using the two-contact circular test structure. The magnitude of ρc for the Ti/Ni/Au contacts on unimplanted SiC was 1.29 x 10−6 Ω.cm2. The value of ρc increased significantly at an implant dose of 1 x 1015 ions/cm2. The dependence of ρc on ion dose has been measured using both C and P implant species.
Energetically-deposited carbon contacts to n-type 6H-SiC have exhibited either insulating, rectifying or ohmic electrical characteristics depending on the average energy of the depositing flux and the substrate temperature. Deposition at room temperature and at a low-medium average energy (<500 eV) has resulted in carbon with a low graphitic content and insulating electrical contacts. With higher average energy and at a moderately elevated temperature (∼100 °C), the higher graphitic content contacts were rectifying with an ideality factor, η, of ∼1.8 and barrier height of ∼0.88 eV. Oriented graphitic carbon deposited at 200 °C with biases exceeding 300 V formed ohmic contacts.
The formation of nickel germanide has been examined over a range of low temperatures (200-400 °C) in an attempt to minimize the thermal budget for the process. Cross-sectional Transmission Electron Microscopy (TEM) was used to determine the texture of the germanide layer and the morphology and constituent composition of the Ge/NiGe interface. The onset and completion of reaction between Ni and Ge were identified by means of a heated stage in combination with in-situ x-ray diffraction (XRD) measurements. The stages of reaction were also monitored using measurements of sheet resistance of the germanides by the Van der Pauw technique. The results have shown that the minimum temperature for the initiation of reaction of Ni and Ge to form NiGe was 225 °C. However, an annealing temperature > 275 °C was necessary for the extensive (and practical) formation of NiGe. Between 200 and 300 °C, the duration of annealing required for the formation of NiGe was significantly longer than at higher temperatures. The stoichiometry of the germanide was very close to NiGe (1:1) as determined using energy dispersive spectroscopy (EDS).
As ohmic contacts decrease in size and approach nanoscale dimensions, accurate electrical characterization is essential, requiring the development of suitable test structures for this task. We present here a new test structure derived from the standard three-contact circular transmission line model (CTLM) , for determining the specific contact resistivity of ohmic contacts. This test structure minimizes sources of error which arise from the CTLM by – (i) reducing the number of contacts within one test pattern from three to two, (ii) ensuring the assumption of equipotential metal contacts used in modelling is more easily attained experimentally, and (iii) allowing the fabrication of reduced geometrical dimensions essential for determining low specific contact resistivity values. The analytical expressions are presented and experiment results are undertaken to demonstrate the accuracy of the technique. There are no error corrections required for determining contact parameters using the presented test structure.
The OVV blazar 3C 446 was monitored over seven months in 1997 with ground based telescopes and instruments on ESA's Infrared Space Observatory (ISO). The aim was to try to detect variations in the IR and see if these were correlated with optical variations. The object varied in the optical and near-IR during this period, but did not vary in the far-IR. Despite being a factor of ten weaker than in 1983, the optical-IR SED exhibited the same slope. The new far-IR observations from ISO allow us to determine the location of the turnover in the spectrum, caused by synchrotron self-absorption. It occurs just longwards of 100 μm.
The reactive ion etching of diamond in O2, CF4/O2, CHF3/O2, O2/Ar) discharges has been examined as a function of bias voltage, flow rate and composition of the gas mixtures. Etching in O2 and O2/Ar plasmas (with flow ratio of O2/Ar >25% ) was characterised by a high etch rate (∼35 nm/min) and an increase in surface roughness with rising bias voltage. The CF4/O2 plasmas also produced a high etch rate (∼50 nm/min) but with only minor dependence of roughness on bias voltage. In comparison, the O2/Ar (with O2/Ar flow ratio <25%) and CHF3/O2 plasmas resulted in a low etch rate (7-10 nm/min). The high and low rate regimes were identified as ion- enhanced chemical etching and physical sputtering respectively. Etching in the O2/Ar plasmas has been attributed to a combination of the two processes dependent on the O2 content.
We describe the novel application of light coupling masks (LCM) in the lithographic patterning of fine structures in diamond films. A PDMS mask was used in the exposure of complex patterns of gratings in AZP 1205 resist on a substrate of Al/ diamond. The profiles of these grating patterns were then modified on a localized scale by a process of reflow of the resist. We report on the transfer of the patterns formed in resist by the LCMs into the diamond film using a sputtered Al layer as a mask. The two-stage process comprised etching of the pattern into the Al followed by transfer into the diamond film using CF4/ O2 and CHF3/ O2 gases. The presence of O2 in the CF4/ O2 and CHF3/ O2 gas mixtures produced Al oxides on the surface of the mask. The etch selectivity of the mask was greater in CF4/ O2 than in CHF3/ O2 gases and was only weakly dependent on the concentration of O2 (0-12 sccm).
The effect of incorporating a Yb diffusion barrier on the electrical and interfacial properties of In/Hg1−xCdxTe contacts has been examined. Measurements of the specific contact resistance, pc, as a function of Yb layer thickness were performed for a series of semiconductor compositions from x = 0.32 to 0.65. Large changes in pc were evident only at x 0.56 and above a Yb thickness of 2.5nm to 6.0nm, this critical level of layer thickness decreasing with x-value. Analytical examination of the interfaces by Auger electron spectroscopy, secondary ion mass spectroscopy and Rutherford backscattering spectrometry has shown a progressive reduction in the extent of In indiffusion with increasing thickness of the Yb interlayer.
This paper describes a laboratory built ion beam etching system and its performance when used for etching Hg1-xCdxTe, GaAs and InP. The etching system provides a means for forming device mesas on a wide range of semiconductors without having to resort to wet chemical etches. The system uses a Kaufmann ion source, a rotating platform and two flow controllers to allow the variation of gas ratios and flows.