Limits of PowerPoint’s Power: Enhancing students’ self-efficacy and attitudes but not their behavior

The effects of accompanying lectures with computer-mediated PowerPoint presentations or PowerPoint generated overheads on students’ self-efficacy, attitudes, course performance, and class-related behaviors were examined. Two Introduction to Developmental Psychology sections were initially taught with lectures accompanied by either overheads or computer-mediated presentations. The teaching format was switched halfway through the semester. Students reported higher self-efficacy and more positive attitudes toward the class with computer-mediated presentations. They also claimed that the website was more interesting and useful under these teaching conditions, indicating a halo effect of the computer-mediated presentations. However, the teaching format did not appear to affect course-related behavior, such as performance on exams, class attendance, participation in class discussions, or course website usage.     

Phase equilibria of alcohols in supercritical fluids Part II. The effect of side branching on C8 alcohols in supercritical carbon dioxide

This paper is a continuation of a previous study and investigated the phase equilibria of six C₈ alcohols (2,2,4-trimethyl-1-pentanol, 2,4,4-trimethyl-1-pentanol, 2-ethyl-1-hexanol, 2-propyl-1-pentanol, 4-methyl-3-heptanol and 6-methyl-2-heptanol) in supercritical carbon dioxide. Data has been measured between 308 and 348 K for alcohol mass fractions between 0.660 and 0.0162. The results show that the position, size and quantity of side chains have a significant effect on the phase behaviour by changing the shape of the molecule and the effect of the hydroxyl group on the polarity of the molecule. The pressure required for total solubility increases in the following sequence: 4-methyl-3-heptanol < 2,2,4-trimethyl-1-pentanol < 6-methyl-2-heptanol < 2,4,4-trimethyl-1-pentanol < 2-propyl-1-pentanol < 2-ethyl-1-hexanol < 1-octanol. The difference in phase behaviour is believed to be a result of a difference in shielding of the hydroxyl group. Greater shielding of the hydroxyl group results in a less asymmetric system, and this, in turn, results in higher solubility of the molecule.     

Emulsion processing of polymer-derived porous Si/C/(O) ceramic bodies

A novel route of miniemulsion processing was applied to preceramic polymers in order to fabricate porous Si/C/(O) bodies. Commercially available polysiloxane and polycarbosilane precursors and water were emulsified via intensive stirring or ultrasonication in the presence of surfactants, and subsequently shaped and cured in an autoclave. The resulting green bodies were dried and pyrolytically converted at 700 and 1050 °C under nitrogen into ceramic counterparts retaining their shape. A fine interconnected pore network derived from the aqueous phase allows escape of gaseous decomposition products during pyrolysis and avoids cracking. In the presence of transition metals such as Fe, Co, Ni or Pd nanofibers consisting of β-SiC/a-SiO₂ are formed. Effects of polymer viscosity and processing parameters on the microstructures, porosities and pore sizes of the resulting products were investigated by means of DLS, mercury porosimetry, SEM, TEM, XRD and FTIR.     

Progranmable Pneumatic Generator for Manipulation of Intrathoracic Pressure

The determination that blood can move during cardiopulmonary resuscitation because of imposed changes in intrathoracic pressure has led to the construction and testing of mechanical devices for increasing intrathoracic pressure fluctuations over those obtained by manual means. These mechanical systems have required high-pressure ventilation simultaneous with compression of the chest to augment blood flow. Their usefulness has been limited, however, because of the requirement for endotracheal intubation and complex devices. Similar systems have also been used to generate intrathoracic pressure changes timed to the cardiac cycle to aid the failing, but beating, heart. A system was developed that can produce high intrathoracic pressure without simultaneous ventilation by using a vest that is placed around the thorax. The vest contains a bladder that is rapidly inflated and deflated by the programmable pneumatic generator. Air flows into and out of the bladder by the proper sequencing of large-bore three-way and two-way solenoid valves that are connected in series. A microcomputer-based controller is used to sequence the valves. The programmable pneumatic generator inflates the bladder more rapidly and to higher pressures than previous systems. The programmable pneumatic generator has been used in studies of cardiopulmonary resuscitation (heart arrested) and circulatory assistance (heart beating, but function depressed).     

Bone loss after hip fracture is correlated to the postoperative degree of mobilisation

This study quantifies changes in bone mineral density (BMD) in the opposite hip and in both proximal tibiae and the correlation with the use of walking aids for patients with two types of hip fracture during the 1st year after surgery. In all, 26 women and 15 men aged 42-88 years (median 71 years) were included. Twenty-one patients had an intracapsular hip fracture (ICF) and 20 had an intertrochanteric fracture (ITF). All patients were treated with a dynamic hip screw. BMD was measured by dual X-ray absorptiometry (DXA; LUNAR, Wisconsin) within the 1st week after surgery and after 3, 6 and 12 months. Initial BMD of the non-fractured hip was significantly lower for both fracture groups compared with reference material. For both fracture types there was a significant decrease in BMD of the non-fractured hip and proximal tibia of the fractured leg during the first 3 months, which still persisted a year after surgery. Improved mobilisation between two examinations was positively correlated with changes in BMD of the proximal tibia of the fractured leg and the non-fractured hip.     

Activated human protein C prevents thrombin-induced thromboembolism in mice. Evidence that activated protein c reduces intravascular fibrin accumulation through the inhibition of additional thrombin generation

Activated protein C (APC) is a potent physiologic anticoagulant with profibrinolytic properties, and has been shown to prevent thrombosis in different experimental models. We investigated the effect of human APC on thrombin-induced thromboembolism in mice, a model of acute intravascular fibrin deposition leading to death within minutes. APC given intravenously (i.v.) as a bolus 2 min before thrombin challenge (1,250 U/kg) reduced mortality in a dose-dependent manner despite the lack of thrombin inhibitor activity. Significant inhibition of thrombin-induced death was observed at the dose of 0.05 mg/kg, and maximal protection was obtained with 2 mg/kg (> 85% reduction in mortality rate). Histology of lung tissue revealed that APC treatment (2 mg/kg) reduced significantly vascular occlusion rate (from 89.2 to 46.6%, P < 0.01). The protective effect of APC was due to the inhibition of endogenous thrombin formation as indicated by the fact that (a) the injection of human thrombin caused a marked decrease in the coagulation factors of the intrinsic and common pathways (but not of Factor VII), suggesting the activation of blood clotting via the contact system; (b) APC pretreatment reduced markedly prothrombin consumption; (c) the lethal effect of thrombin was almost abolished when the animals were made deficient in vitamin K-dependent factors by warfarin treatment, and could be restored only by doubling the dose of thrombin, indicating that the generation of endogenous thrombin contributes significantly to death; and (d) APC failed to protect warfarin-treated animals, in which mortality is entirely due to injected thrombin, even after protein S supplementation. Other results suggest that APC protects from thrombin-induced thromboembolism by rendering the formed fibrin more susceptible to plasmin degradation rather than by reducing fibrin formation: in thrombin-treated mice, fibrinogen consumption was not inhibited by APC; and inhibition of endogenous fibrinolysis by epsilon-aminocaproic or tranexamic acid resulted in a significant reduction of the protective effect of APC. Since APC did not enhance plasma fibrinolytic activity, as assessed by the measurement of plasminogen activator (PA) or PA inhibitor (PAI) activities, PAI-1 antigen, or 125I-fibrin degrading activity, we speculate that the inhibition of additional (endogenous) thrombin formation by APC interrupts thrombin-dependent mechanisms that make fibrin clots more resistant to lysis, so that the intravascular deposited fibrin can be removed more rapidly by the endogenous fibrinolytic system.     

SLIM: a slender technique for unbounded-field problems

Electrostatic- and electromagnetic-field problems in unbounded regions are often solved using finite differences (FD's) or finite elements (FE) combined with approximate boundary conditions. Inversion of the sparse FD or FE matrix is then required. First-order or higher order absorbing boundary conditions may be used, or one can use more accurate boundary conditions obtained by the measured equation of invariance (MEI) or by iteration. The more accurate boundary conditions are helpful because they permit reduction of the size of the mesh and, thus, the number of unknowns. In this paper, we show that the process can be carried to a maximally simple limit in which the mesh is reduced to a single layer and the matrix-inversion step disappears entirely. This results in the single-layer iterative method (SLIM), an unusually simple technique for unbounded-field problems. Computational experiments demonstrate the effectiveness of SLIM in electrostatics, and also in electrodynamic examples, such as scattering of TM plane waves from a perfectly conducting cylinder. The technique is most likely to be useful in large or complex problems where simplification is helpful, or in repetitive calculations such as scattering of radiation from many angles of incidence     

Quantitative studies on the melittin-induced leakage mechanism of lipid vesicles

We have investigated, both experimentally and theoretically, the efflux of carboxyfluorescein (a self-quenching fluorescent dye) from vesicles of different sizes and lipid species (POPC, DOPC) after having added the bee venom peptide melittin. This comprises quantitative analyses regarding the extent of lipid-associated peptide, the mode as well as the temporal progress of dye release and the possible leakage mechanism. Our results indicate a graded efflux characterized by a single-pore retention factor reflecting the formation of pores whose lifetimes are rather small (millisecond range). The observed fluorescence signal arising from the dequenching of effluent dye has been converted to the number of pore openings over the course of time. All the resulting curves exhibit a pronounced slowing down of the pore formation rate revealing two distinct relaxation steps at about 20 and 200 s, respectively, being largely independent of vesicle type and peptide to lipid ratio. The pore formation rate itself increases in proportion to the amount of membrane bound peptide. We give a quantitative account of our experimental findings based on a novel reaction scheme applicable to any of our various liposome systems. It implies that the pore formation rate is controlled by a passage through two intermediate monomeric peptide states. These states are thought to become well populated in the initial stage of lipid bilayer perturbation, but would practically die out after some time owing to a restabilization of the membrane system.