Makers have proven to be skilled at prototyping and therefore present a unique opportunity for companies, who seek to improve their capabilities, to learn from them. In this study, a mixed methods approach was used to understand possible benefits to both companies and makers from collaborating in prototyping, and to identify a set of design considerations to guide the future development of a tool to facilitate such collaboration. Despite challenges to collaboration, a tool designed to help companies engage with makers in prototyping could be beneficial to both and should be developed.

Interfacial dislocations (IDs) and half-loop arrays (HLAs) present in theepilayers of 4H-SiC crystal are known to have a deleterious effect on deviceperformance. Synchrotron X-ray Topography studies carried out on n-type 4H-SiCoffcut wafers before and after epitaxial growth show that in many cases BPDsegments in the substrate are responsible for creating IDs and HLAs during CVDgrowth. This paper reviews the behaviors of BPDs in the substrate during theepitaxial growth in different cases: (1) screw-oriented BPD segmentsintersecting the surface replicate directly through the interface during theepitaxial growth and take part in stress relaxation process by creating IDs andHLAs (Matthews-Blakeslee model [1] ); (2) non-screw oriented BPD half loopintersecting the surface glides towards and replicates through the interface,while the intersection points convert to threading edge dislocations (TEDs) andpin the half loop, leaving straight screw segments in the epilayer and thencreate IDs and HLAs; (3) edge oriented short BPD segments well below the surfaceget dragged towards the interface during epitaxial growth, leaving two longscrew segments in their wake, some of which replicate through the interface andcreate IDs and HLAs. The driving force for the BPDs to glide toward theinterface is thermal stress and driving force for the relaxation process tooccur is the lattice parameter difference at growth temperature which resultsfrom the doping concentration difference between the substrate and epilayer.

A review is presented of Synchrotron X-ray Topography and KOH etching studies carried out on n type 4H-SiC offcut substrates before and after homo-epitaxial growth to study defect replication and strain relaxation processes and identify the nucleation sources of both interfacial dislocations (IDs) and half-loop arrays (HLAs) which are known to have a deleterious effect on device performance. We show that these types of defects can nucleate during epilayer growth from: (1) short segments of edge oriented basal plane dislocations (BPDs) in the substrate which are drawn by glide into the epilayer; and (2) segments of half loops of BPD that are attached to the substrate surface prior to growth which also glide into the epilayer. It is shown that the initial motion of the short edge oriented BPD segments that are drawn from the substrate into the epilayer is caused by thermal stress resulting from radial temperature gradients experienced by the wafer whilst in the epi-chamber. This same stress also causes the initial glide of the surface half-loop into the epilayer and through the advancing epilayer surface. These mobile BPD segments provide screw oriented segments that pierce the advancing epilayer surface that initially replicate as the crystal grows. Once critical thickness is reached, according to the Mathews-Blakeslee model [1], these screw segments glide sideways under the action of the mismatch stress leaving IDs and HLAs in their wake. The origin of the mismatch stress is shown to be associated with lattice parameter differences at the growth temperature, arising from the differences in doping concentration between substrate and epilayer.

The combined application of section and projection topography carried out using synchrotron white beam radiation can be a powerful tool for the determination of the three-dimensional configurations of defects in single crystals. In this paper, we present examples of the application of this combination of techniques to the analysis of defect configurations in PVT-grown 4H-SiC wafers cut perpendicular and parallel to the growth axis. Detailed correlation between section and projection topography of threading screw dislocations (TSDs) is presented with particular emphasis being laid on the determination of the signs of the dislocations. Further, information can also be determined regarding the position of the dislocations within the crystal depth. In addition, similar correlation is presented for threading edge dislocations (TEDs) and basal plane dislocations (BPDs). The section topography images of dislocations can comprise direct, intermediary and dynamical contrast and all three types are observed. The application to the study of stacking faults will be also discussed in detail.

Synchrotron topography studies are presented of the behavior of growth dislocations and deformation-induced dislocations in 4H-SiC single crystals. The growth dislocations include those in threading orientation with line directions approximately along c with Burgers vectors of a, c, and n a+m c (where n and m are integers) while the deformation-induced dislocations include those with line directions confined to the basal plane with Burgers vectors of a and Shockley partial dislocations with Burgers vectors of 1/3<1-100> as well as those with line directions in the {1-100} prismatic planes with Burgers vectors of a. Processes leading to the nucleation of the growth dislocations are discussed as well as their deflection onto the basal plane during crystal growth in a reversible process. This latter process can lead to the conversion of segments of the deflected growth dislocations into deformation induced dislocations. In some cases this can lead to dislocation multiplication via the Hopping Frank-Read source mechanism and in others to the motion of single Shockley partial dislocations leading to Shockley stacking fault expansion. Studies are also presented of interactions between threading growth dislocations with c-component of Burger’s vector facilitated by climb processes which are mediated by interactions with non-equilibrium concentrations of vacancies. This can lead to reactions whereby complete or partial dislocation Burgers vector annihilation occurs.

Summary

Background and objective: Previous studies mainly conducted on elective patients recommend doses of 0.9–1.2 mg kg−1 rocuronium to obtain comparable intubation conditions with succinylcholine 1.0 mg kg−1 after 60 s during a rapid-sequence induction. We decided to compare the overall intubating conditions of standard doses of rocuronium 0.6 mg kg−1 and succinylcholine 1.0 mg kg−1 during a strict rapid-sequence induction regimen including propofol and alfentanil. Methods: Male and female patients (ASA I–III) older than 17 yr scheduled for emergency abdominal or gynaecological surgery and with increased risk of pulmonary aspiration of gastric content were randomized to a rapid-sequence induction with succinylcholine 1.0 mg kg−1 or rocuronium 0.6 mg kg−1. Patients with a predicted difficult airway were excluded. A senior anaesthesiologist ‘blinded’ for the randomization performed the intubation 60 s after injection of the neuromuscular blocker. Intubating conditions were evaluated according to an established guideline. Tracheal intubation not completed within 30 s was recorded as failed. Results: 222 patients were randomized. Three patients had their operation cancelled and 10 did not fulfil the inclusion criteria. Clinically acceptable intubation conditions were present in 93.5% and 96.1% of patients in the succinylcholine group (n = 107) and the rocuronium group (n = 102), respectively (P = 0.59). Conclusions: During a rapid-sequence induction with alfentanil and propofol, both rocuronium 0.6 mg kg−1 and succinylcholine 1.0 mg kg−1 provide clinically acceptable intubation conditions in 60 s in patients scheduled for emergency surgery. Under the conditions of this rapid-sequence induction regimen rocuronium may be a substitute for succinylcholine.

Background and objective Late postoperative hypoxaemia after upper abdominal surgery is common even among cardiopulmonary healthy patients. Atelectasis may develop after intubation and persist into or reveal a disposition for atelectasis in the postoperative period. Positive end–expiratory pressure (PEEP) eliminates peroperative atelectasis but the effect on perioperative oxygenation is controversial. This study evaluated the effect of peroperative PEEP optimized pulmonary compliance on perioperative oxygenation and complications.

Methods Forty patients assessed by electrocardiography, spirometry, functional residual capacity and diffusion capacity were randomly assigned to receive positive end–expiratory pressure (PEEP) or zero endexpiratory pressure (ZEEP) during surgery. PaO2, SPO2 and complications in the postoperative period were evaluated without knowledge of peroperative PEEP or ZEEP application.

Results Peroperative arterial oxygenation improved for all patients receiving PEEP, mean 2.1 kPa (0.7–3.5 kPa). There was no difference in postoperative median PaO2 between the groups. The differences in the incidence of late prolonged postoperative hypoxaemia and complications were 25% (−5% to 55%) and −1% (−31% to 29%) between the ZEEP and the PEEP group, but were not statistically significant.

Peat deposits in Greenland and Denmark were investigated to show that high-resolution dating of these archives of atmospheric deposition can be provided for the last 50 years by radiocarbon dating using the atmospheric bomb pulse. 14C was determined in macrofossils from sequential one cm slices using accelerator mass spectrometry (AMS). Values were calibrated with a general-purpose curve derived from annually averaged atmospheric 14CO2 values in the northernmost northern hemisphere (NNH, 30°–90°N). We present a thorough review of 14C bomb-pulse data from the NNH including our own measurements made in tree rings and seeds from Arizona as well as other previously published data. We show that our general-purpose calibration curve is valid for the whole NNH producing accurate dates within 1–2 years. In consequence, 14C AMS can precisely date individual points in recent peat deposits within the range of the bomb-pulse (from the mid-1950s on). Comparing the 14C AMS results with the customary dating method for recent peat profiles by 210Pb, we show that the use of 137Cs to validate and correct 210Pb dates proves to be more problematic than previously supposed.

As a unique example of our technique, we show how this chronometer can be applied to identify temporal changes in Hg concentrations from Danish and Greenland peat cores.

The effect of surfactant on the breakup of a viscous filament, initially at rest, surrounded by another viscous fluid is studied using linear stability analysis. The role of the surfactant is characterized by the elasticity number – a high elasticity number implies that surfactant is important. As expected, the surfactant slows the growth rate of disturbances. The influence of surfactant on the dominant wavenumber is less trivial. In the Stokes regime, the dominant wavenumber for most viscosity ratios increases with the elasticity number; for filament to matrix viscosity ratios ranging from about 0.03 to 0.4, the dominant wavenumber decreases when the elasticity number increases. Interestingly, a surfactant does not affect the stability of a filament when the surface tension (or Reynolds) number is very large.

Investigations of intestinal secretion are often performed under anaesthesia. This study evaluates the influence of anaesthetic agents on the intestinal secretion induced by cholera toxin (CT) in the pig. CT was instilled for 4 h in ligated jejunal loops under anaesthesia with halothane, saffan, [alpha]-chloralose, or propofol. Cardiovascular parameters, blood gas data, plasma cortisol levels, net fluid accumulation, intraluminal mediators (serotonin (5-HT), prostaglandin E2 (PGE2)) and electrolyte concentrations in the accumulated fluid were determined. The systolic blood pressure and heart rate was highest for saffan-anaesthetized pigs (blood pressure: saffan > [alpha]-chloralose > propofol = halothane; heart rate: saffan > [alpha]-chloralose = propofol = halothane), while blood gases and cortisol levels were within the same range. CT induced a dose-dependent fluid accumulation under all four anaesthetics. The fluid accumulation was significantly higher in pigs treated with saffan, [alpha]-chloralose and propofol than in halothane-treated pigs (saffan = [alpha]-chloralose > propofol > halothane). There was no significant difference in electrolyte concentrations in the accumulated fluid or in the luminal content of 5-HT and PGE2 between anaesthetics. The results demonstrate that anaesthetic agents profoundly influence the secretory response in the small intestine and indicate the importance of the choice of anaesthetic in this type of experiment.

Cardiac and major abdominal surgery are associated with granulocytosis in peripheral blood. The purpose of the present study was to describe the granulocyte and monocyte oxidative burst and the expression of adhesion molecules following cardiac surgery with cardiopulmonary bypass and abdominal surgery. The ability to respond with an oxidative burst was measured by means of flow cytometry using 123-dihydrorhodamine. The adhesion molecules CD11a/CD18, CD11c/CD18, CD44 were measured using monoclonal antibodies. Blood samples from eight patients undergoing open-heart surgery were taken before surgery, 1, 5, 10 and 20 min after aortic clamping, and then 1, 5, 10 and 20 min and 1, 2 and 3 h after declamping. Samples from eight patients undergoing abdominal surgery were taken before surgery, at the end of surgery, and 2 and 3 h post-operatively. A decrease in number of granulocytes and monocytes during cardiopulmonary bypass was observed. The percentage of CD11a-positive granulocytes increased from 30% preoperatively to 75% following cardiopulmonary bypass, while CD44-positive granulocytes increased from 5% to 13%. Despite the extent of the changes, these were not significant. The oxidative burst of the granulocytes and monocytes decreased after declamping to 15% and 27% of initial values in vitro. Several hours after surgery, there was no significant difference between the two groups. These results can be explained by a granulocyte and monocyte refractory response developing subsequent to an increased per-operative oxidative burst activity, and the induction of adhesion molecules on granulocytes associated with the cardiopulmonary bypass and surgery. In conclusion, open-heart surgery with cardiopulmonary bypass was associated with a rapid and pronounced activation of leukocytes which may play a role in reperfusion injury.

A novel methodology has been developed for the preparation of amorphous semiconductor samples for use in transmission extended x-ray absorption fine structure (EXAFS) measurements. Epitaxial heterostructures were fabricated by metal organic chemical vapour deposition (group III-Vs) or molecular beam epitaxy (group IVs). An epitaxial layer of ∼2 μm thickness was separated from the underlying substrate by selective chemical etching of an intermediate sacrificial layer. Ion implantation was utilised to amorphise the epitaxial layer either before or after selective chemical etching. The resulting samples were both stoichiometric and homogeneous in contrast to those produced by conventional techniques. The fabrication of amorphous GaAs, InP, In0.53Ga0.47As and SixGe1-x samples is described. Furthermore, EXAFS measurements comparing both fluorescence and transmission detection, and crystalline and amorphised GaAs, are shown.

We report the analysis of 154 hours of nearly continuous high-speed photometric data on the pulsating DB white dwarf (DBV) GD 358 obtained during the Whole Earth Telescope (WET) run of May 1990. The Fourier transform (FT) of the light curve is dominated by power in the range from 1200 – 1700μHz with more than 180 significant peaks in the total transform. We also see significant power at the sums and differences of the dominant frequencies, indicating the importance of nonlinear behavior. We can use this data to obtain an accurate total stellar mass, and surface He layer mass. The implied surface He layer mass, if correct, provides a significant and surprising challenge to stellar evolution theory, as well as the theory of chemical mixing.

We consider a three-state lattice-gas with nearest-neighbor interactions on a triangular lattice as a model for multicomponent chemi- and physisorption. By varying the lateral interaction constants between the adsorbate particles, this model can be made to exhibit either enhanced adsorption or poisoning (inhibited adsorption). We discuss here the conditions on the interaction constants that lead to poisoning. We present the results of a ground-state calculation and detailed numerical study of the phase diagram for a set of interactions that exhibits poisoning. We calculate the phase diagrams and adsorption isotherms by the finite-size scaling transfer-matrix method. We consider the result as a simple model for the coadsorption of Sulphur and Hydrogen on a Platinum (111) surface, with interaction constants estimated from experimental data. The resulting adsorption isotherms are in good agreement with experimental results.