On Interval Systems [<Emphasis Type="Italic">x</Emphasis>] = [<Emphasis Type="Italic">A</Emphasis>][<Emphasis Type="Italic">x</Emphasis>] + [<Emphasis Type="Italic">b</Emphasis>] and the Powers of Interval Matrices in Complex Interval Arithmetics

For the interval system of equations defined by [x] = [A][x] + [b] we derive necessary and sufficient criteria for the existence of solutions [x]. Furthermore we give necessary and sufficient criteria for the convergence of powers of [A]. In contrast to former results we treat complex interval arithmetics.     

Keyhole stability during laser welding—part I: modeling and evaluation

The keyhole is a requirement in order to establish the energy efficient process of laser deep penetration welding. However, the process is highly unstable which results in unwanted pore and spatter formation. In order to avoid process defects, the physical effects in the keyhole have to be better understood to find ways for compensation. This work aims to describe the keyhole properties at different welding parameters for welding of aluminum (EN AW 1050) with the help of a semi-analytical model based on energy and pressure equations and differential equations. The resulting dynamic characteristics of different keyholes are evaluated with frequency analysis of optical observations during the welding process. The spring coefficient, that describes the radial pressure change at radius deviation, is a good indicator for the resulting keyhole dynamics. Dynamic behavior is influenced by the spatial laser intensity distribution, while higher frequencies at lower amplitudes are found at a Top Hat distribution compared to a Gaussian intensity profile.     

What role do lay beliefs about hypertension etiology play in perceptions of medication effectiveness?

Background: Some people take the disease label "hypertension" literally; leading to the belief that increasing relaxation instead of medication is the best treatment for this condition. We experimentally tested the effect of such underlying beliefs on ratings of interventions for hypertension and compared alternative communication strategies to increase medication effectiveness ratings. Methods: Outpatients (N = 152) with a known diagnosis of hypertension read a vignette describing an asymptomatic condition and recommended treatment. Experimental factors were the disease label (Hypertension vs. Korotkoff's Syndrome) and type of argument designed to persuade the reader that medication is most effective (Causal vs. Correlational). Measures: Background measures included demographics, beliefs that stress causes health problems and trust in physicians. Outcomes were effectiveness ratings for interventions to treat the condition. Results: Participants who read a vignette describing "Hypertension" rated "relaxing more" as significantly more effective than participants exposed to the same condition but with the unfamiliar "Korotkoff's Syndrome" label, [F(1, 141) = 5.22, p = .024]. However, medication, reducing salty foods and losing weight were rated as more effective than relaxing more. Intervention ratings did not differ by type of argument presented. There was a significant interaction of disease label and trust in physicians [F(1, 125) = 7.01, p = .009]. Individuals with low trust rated medication as significantly less effective when exposed to an unfamiliar disease label. Conclusions: This study confirms the effect of the hypertension disease label on ratings of different interventions for the condition. However, participants rated biomedically recommended interventions as more effective than those not endorsed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Laser Diagnostics of Combustion Processes: From Chemical Dynamics to Technical Devices

Laser-based in situ diagnostic techniques with high temporal, spectral, and spatial resolution have become valuable tools to study the molecular dynamics of gas-phase and heterogeneous reactions as well as complex technical combustion processes. Results of recent experiments will be presented in which laser-induced fluorescence, sum-frequency generation surface vibrational spectroscopy, Rayleigh scattering, excimer laser-induced fragmentation fluorescence, and high-resolution tunable diode laser absorption spectroscopy were applied to investigate elementary chemical gas-phase and catalytic combustion reactions, internal combustion engine processes, as well as coal combustion and waste incineration.     

On the Solutions of the Interval System [<Emphasis Type="Italic">x</Emphasis>] = [<Emphasis Type="Italic">A][x</Emphasis>] + [<Emphasis Type="Italic">b</Emphasis>]

For the interval system of equations defined by [x] = [A][x]+[b]with(|[A])|1 we derive a necessary and sufficient criterion for the existence and uniqueness of solutions [x]. Generalizing former results we allow the absolute value |[A]| of [A] to be reducible.     

H2O chemisorption and H2 oxidation on yttria-stabilized zirconia: Density functional theory and temperature-programmed desorption studies

The mechanism of H₂O dissociation as well as the adsorption and oxidation reaction of H₂ on yttria-stabilized zirconia (YSZ), commonly used as part of solid oxide fuel cell (SOFC) anodes, was investigated employing temperature-programmed desorption (TPD) spectroscopy and density functional theory (DFT). In agreement with theory the experimental results show that interaction of gaseous H₂O with YSZ results in dissociative adsorption leading to strongly bound OH surface species. In the interaction of gaseous H₂ with an oxygen-enriched YSZ surface (YSZ + O) similar OH surface species are formed as reaction intermediates in the H₂ oxidation. Our experiments showed that in both the H₂O/YSZ and the H₂/YSZ + O heterogeneous reaction systems noticeable amounts of H₂O are “dissolved” in the bulk as interstitial hydrogen and hydroxyl species. The experimental H₂O desorption data is used to access the accuracy of the H₂/H₂O/YSZ adsorption/desorption and surface reaction kinetics data, employed in previous modeling studies of the electrochemical H₂ oxidation on Ni-pattern/YSZ model anodes by Vogler et al. [J. Electrochem. Soc., 156 (2009) B663] and Goodwin et al. [J. Electrochem. Soc., 156 (2009) B1004]. Finally a refined experimentally validated H₂/H₂O/YSZ adsorption/desorption and surface reaction kinetics data set is presented.     

Synthesis of (±)-disparlure

A six-step, convergent synthesis has been developed for racemic (Z)-7,8-epoxy-2-methyloctadecane (disparlure), the sex pheromone of the gypsy moth. The key step is a Wittig reaction between 6-methylheptanal and triphenylundecylphosphonium bromide effected by potassium carbonate in the presence of a crown ether.