Some defects in finite-difference edge finders

This work illustrates and explains various artifacts in the output of five finite difference edge finders, those of J.F. Canny (1983, 1986), R.A. Boie et al. (1986) and R.A. Boie and I.J. Cox (1987), and three variations on that of D. Marr and E.C. Hildreth (1980), reimplemented with a common output format and method of noise suppression. These artifacts include gaps in boundaries, spurious boundaries, and deformation of region shape     

Can Acorn Tannin Predict Scrub-Jay Caching Behavior?

We tested the hypothesis that animals caching acorns for future food use may preferentially cache acorns high in tannin content. We used a population of Florida scrub-jays (Aphelocoma coerulescens) that cache acorns from four oak species. Tannin activity in acorns was measured by protein precipitating ability (PPA). Logistic regression models accurately predicted frequency of acorn caching among the oak species, using frequency of usable acorns and PPA loss during burial as predictor variables. Among the four oak species, frequency of caching increased with both increasing frequency of undamaged acorns at peak harvest time, and increasing loss of PPA during burial. Other regression models accurately predicted frequency of undamaged acorns for each species, using green acorn PPA and buried acorn PPA as predictor variables. Among the four oak species, frequency of usable acorns tended to increase with increasing green acorn PPA, and decreased with buried acorn PPA. We suggest that a deterrent effect of tannins on insect larvae is responsible for the differences in frequency of acorns usable to jays among oak species, and that jays select acorns for burial by assessing insect damage. Species differences in PPA change during burial probably reinforce this pattern of scrub-jay caching behavior.     

Intravascular ultrasound assessment of direct percutaneous transluminal coronary angioplasty in patients with acute myocardial infarction

BACKGROUND: Acute myocardial infarction is caused by sudden thrombotic occlusion of the coronary artery due to a previous rupture of atherosclerotic plaque. OBJECTIVE: To use intracoronary ultrasound measurements to evaluate lumen and plaque changes in patients with acute myocardial infarction. METHODS: Patients (n = 103) with acute myocardial infarction who had been scheduled to undergo primary percutaneous transluminal coronary angioplasty (PTCA) were selected. Both before and after successful coronary angioplasty, intracoronary 30 MHz ultrasound studies were performed using a 3.5F monorail catheter. The ultrasound catheter was successfully advanced into the occluded vessel segment without major complications prior to PTCA in 79 of 103 (76.7%) patients and after PTCA in 88 of 103 (85.3%) patients. RESULTS: The plaques were eccentric in 66 patients (83.5%). The plaque morphology was purely low echogenic in 14 (17.7%), highly echogenic in six (7.6%) and mixed in 59 (74.7%) patients. Partial (59 of 79, 74.7%) or ring-like calcification (3 of 79, 3.8%) was observed in 62 patients (78.5%). Plaque fissuring or dissection was detected prior to PTCA in 25 patients (31.7%). Coronary angioplasty successfully enlarged the inner luminal area from 2.1 +/- 0.7 to 7.4 +/- 1.9 mm2 (P < 0.01), whereas the plaque-thrombus area decreased significantly (13.8 +/- 1.7 mm2 before and 9.0 +/- 1.9 mm2 after PTCA; P < 0.01). The total vessel area remained virtually constant (15.9 +/- 1.9 mm2 before and 16.4 +/- 2.5 mm2 after PTCA, NS). PTCA-induced plaque rupture or dissection was observed in only 13 (16.5%) patients. CONCLUSION: Intracoronary ultrasound imaging can be performed safely and successfully prior and subsequent to PTCA in selected patients with acute myocardial infarction. Early reperfusion via PTCA seems to be attributable to a significant reduction in the amount of low-echogenic plaque and thrombus material, whereas factors like balloon-induced dissection and stretching of vessels play only a minor role.     

Social cognitions as organizers of autonomic and affective responses to social challenge.

Autonomic and affective responses to children were assessed as a function of adult perceptions of interpersonal control. Women (N?=?160) interacted with and provided feedback to computer-simulated children who behaved responsively or unresponsively on a computer game. Women were categorized as low in perceived control (PC) if they attributed high control to children but low control to self over negative events on the Parent Attribution Test. As predicted, low-PC women were maximally reactive to child characteristics, manifesting peak levels of defensive arousal (increased level of heart rate and electrodermal activity) and negative affect with unresponsive children and minimal levels of arousal and negative affect with responsive children. Intermediate response levels were shown by high-PC Ss. We interpreted results as suggesting mediating factors that may operate in dysfunctional interaction patterns previously found for low-PC caregivers. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Partial portal vein and mesenteric vein thrombosis in familial protein S deficiency

Protein S, a vitamin-K dependent glycoprotein is a cofactor of protein-C system, which acts as an inhibitor of the plasmatic coagulation. Protein-S congenital deficiency results in recurrent venous thromboses, atypical locations in portal and mesenteric veins are possible. In our patient the partial thrombosis of the portal vein was diagnosed by computed tomography and angiography. Small bowel ischaemia due to mesenteric vein thrombosis required segmental resection. Post-operatively the patient was heparinized and later phenprocoumon was applied to a long-term therapy.     

Failure of a Porous Solid from a Deep Notch

A finite strain finite element method is used to examine the stress state near the tip of a deep notch in an elastic-plastic porous solid. The notch is loaded in mode I plane strain tension and small scale yielding is assumed. Two rate independent strain hardening material models are used: a version of the Gurson model (1977) and the more recent FKM model developed by Fleck, Kuhn and McMeeking (1992). Under increasing K _I, void growth is initially stable and independent of mesh dimension. Localization of plastic flow sets in at a finite value K _i, and the deformation field is mesh-size dependent thereafter. The initiation of crack growth at the notch root is assumed to occur when a critical level of porosity is attained. The results show that the shape of the plastic zone for both the Gurson and the FKM material is highly dependent on the initial porosity. In the case of low initial porosity, the plastic zone shape is similar to that of a fully dense material; at higher initial porosities the plastic zone is concentrated ahead of the notch tip. The effect of the initial void volume fraction on the porosity field and the critical stress intensity factor is studied, and the mesh-size dependence of the results is discussed. The analysis is useful for prediction of the notched strength of porous metals. This revised version was published online in August 2006 with corrections to the Cover Date.     

Age-dependent differences in the effect of ischaemia on the rat kidney: prevention of the postischaemic damage by different drugs

The acute and subchronic effects of temporary renal ischaemia (45 min) were investigated in one- and two-month old rats. During bilaterial occlusion of renal arteries, the systemic blood pressure (BP) decreased from 90 to 55 and from 100 to 75 mmHg in one- and two-month old rats, respectively. Immediately after reperfusion, BP returned to the baseline level. This temporary drop in BP was prevented by continuous infusion of normal saline, dopamine, or mannitol. However, postischaemic lethality was very similar in all groups (45% in young and 28% in adult rats). An increase in blood urea concentration was observed only 24 hours after the ligation procedure. However, the rats died within 4 postischaemic days often without an elevation in blood urea. Different treatment schedules (infusion of normal saline, dopamine, and mannitol, bolus injection of dimethyl sulfoxide /DMSO/, mannitol, or furosemide, 7-day treatment with thiamazole) were compared. Lethality was reduced only by thiamazole in young rats (45% vs 11%, p < or = 0.01). No ammelioration was seen in adult rats; the lethality was increased in these rats after furosemide (28% vs 73%, p < or = 0.01). The increase in blood urea concentration regularly observed in all rats 24 hours after ischaemia, was lower in all treated groups of young rats except dopamine. In adults, only saline infusion ammeliorated this increase; on the other hand furosemide led to a higher increase than in untreated controls. Saline infusion, DMSO, mannitol, furosemide, and thiamazole treatment are all partially protective in young rats.     

Single steel strut mechanical testing: challenges and future research directions

Open-cell stainless steel foams, composed of hollow struts, are excellent candidates for energy absorption and thermo-mechanical applications. The basic mechanical element responsible for the function of these foams is the single strut. However, testing and characterisation of single foam struts to predict the foam strength have stirred up a new debate about approaches to micro-tensile testing of such elements. In this paper, we present a protocol for in-situ micro-tensile testing of hollow steel struts using a custom-made grip system. The adapted grips make it possible to perform analysis of the deformation of multiple sintered struts. Here we present and discuss challenges encountered during such micro-tensile testing of hollow steel struts.