Aging of the over-voltage protection elements caused by over-voltages

The aim of this work is examining the influence of the number of the activation––over-voltage pulses to the aging of over-voltage protection elements. Both non-linear (gas-filled surge arresters (GFSA), varistors, over-voltage diodes) and linear (capacitors––constituents of filters) over-voltage protection elements were tested. The instruments employed allow reliable measurements, 1000 consecutive activation were tested. The double-exponential current pulse (amplitude I₁^max=13 A, I₂^max=16 A, rise time T₁=8 μs, fall time T₂=20 μs) for non-linear elements and a double-exponential over-voltage pulse (rise time T₁=1.2 μs, fall time T₂=50 μs) of the amplitude U₁^max=320 V, U₂^max=480 V and U₃^max=640 V for capacitors were used. The experimental results show that the over-voltage diodes are the most reliable elements in view of characteristic modifications that are consequence of aging. However, it was observed that varistors, GFSA and capacitors undergo noticeable changes in characteristics.     

"I know you self-handicapped last exam": Gender differences in reactions to self-handicapping.

Past research has shown that self-handicapping involves the trade-off of ability-related attributional benefits for interpersonal costs. Study 1 examined whether perceiver or target sex moderates impressions of self-handicapping targets. Although target sex was not an important factor, female perceivers were consistently more critical of behavioral self-handicappers. Two additional studies replicated this gender difference with variations of the handicap. Study 3 examined the motives inferred by perceivers and found that women not only view self-handicappers as more unmotivated but also report greater suspicion of self-handicapping motives; furthermore, these differences in perceived motives mediated sex differences in reactions to self-handicappers. Implications for the effectiveness of self-handicapping as an impression management strategy are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of Pulsed Laser Radiation on the Properties of Resistive Thick Films Based on Nickel and Barium Borides

We have used atomic force microscopy to study the surface morphology of resistive thick films based on powders of nickel and barium borides and a glass binder, treated with laser radiation. We used x-ray phase analysis to study the phase composition of these films. We have observed a change in the surface morphology, the phase composition, and the electrical resistance of the studied films as a function of the laser radiation energy.     

Discrete thermodynamics of chemical equilibria and classical limit in thermodynamic simulation

This article sets forth comprehensive basic concepts of the discrete thermodynamics of chemical equilibrium as balance between internal and external thermodynamic forces. Conditions of chemical equilibrium in the open chemical system are obtained in the form of a logistic map, containing only one new parameter that defines the chemical system's resistance to external impact and its deviation from thermodynamic equilibrium. Solutions to the basic map are bifurcation diagrams that have quite traditional shape but the diagram areas feature specific meanings for chemical systems and constitute the system's domain of states. The article is focused on two such areas: the area of “true” thermodynamic equilibrium and the area of open chemical equilibrium. The border between them represents the classical limit, a transition point between the classical and newly formulated equilibrium conditions. This limit also separates regions of the system ideality, typical for isolated classical systems, and non-ideality due to the limitations imposed on the open system from outside. Numerical examples illustrating the difference between results of classical and discrete thermodynamic simulation methods are presented. The article offers an analytical formula to find the classical limit, compares analytical results with these obtained by simulation, and shows the classical limit dependence upon the chemical reaction stoichiometry and robustness.     

Graphene Microbolometers with Superconducting Contacts for Terahertz Photon Detection

We report on noise and thermal conductance measurements taken in order to determine an upper bound on the performance of graphene as a terahertz photon detector. The main mechanism for sensitive terahertz detection in graphene is bolometric heating of the electron system. To study the properties of a device using this mechanism to detect terahertz photons, we perform Johnson noise thermometry measurements on graphene samples. These measurements probe the electron–phonon behavior of graphene on silicon dioxide at low temperatures. Because the electron–phonon coupling is weak in graphene, superconducting contacts with large gap are used to confine the hot electrons and prevent their out-diffusion. We use niobium nitride leads with a \(T_\mathrm {c}\approx 10\)  K to contact the graphene. We find these leads make good ohmic contact with very low contact resistance. Our measurements find an electron–phonon thermal conductance that depends quadratically on temperature above 4 K and is compatible with single terahertz photon detection.     

Gold nanorods with a hematoporphyrin-loaded silica shell for dual-modality photodynamic and photothermal treatment of tumors in vivo

Nanocomposites （NCs） consisting of a gold nanorod core and a mesoporous silica shell doped with hematoporphyrin （HP） have been fabricated in order to improve the efficiency of cancer treatment by combining photothermal and photodynamic therapies （PDT ＋ PTT） in vivo. In addition to the long-wavelength plasmon resonance near 810-830 nm, the fabricated NCs exhibited a 400-nm absorbance peak corresponding to bound HP, generated singlet oxygen under 633-nm excitation near the 632.5-nm Q-band, and produced heat under a 808-nm near-infrared （NIR） laser irradiation. These modalities were used for a combined PDT ＋ PTT treatment of large （about 3 cm3） solid tumors in vivo with a xenorafted tumor rat model. NCs were directly injected into tumors and irradiated simultaneously with 633-nm and 808-nm lasers to stimulate the combined photodynamic and photothermal activities of NCs. The efficiency of the combined therapy was evaluated by optical coherence tomography, histological analysis, and by measurements of the tumor volume growth during a 21-day period. The NC-mediated PDT led to weak changes in tissue histology and to a moderate 20% decrease in the tumor volume. In contrast, the combined PDT ＋ PTT treatment resulted in the large-area tumor necrosis and led to dramatic decrease in the tumor volume.     

An Atomistic Tomographic Study of Oxygen and Hydrogen Atoms and their Molecules in CVD Grown Graphene

The properties and growth processes of graphene are greatly influenced by the elemental distributions of impurity atoms and their functional groups within or on the hexagonal carbon lattice. Oxygen and hydrogen atoms and their functional molecules (OH, CO, and CO₂) positions' and chemical identities are tomographically mapped in three dimensions in a graphene monolayer film grown on a copper substrate, at the atomic part‐per‐million (atomic ppm) detection level, employing laser assisted atom‐probe tomography. The atomistic plan and cross‐sectional views of graphene indicate that oxygen, hydrogen, and their co‐functionalities, OH, CO, and CO₂, which are locally clustered under or within the graphene lattice. The experimental 3D atomistic portrait of the chemistry is combined with computational density‐functional theory (DFT) calculations to enhance the understanding of the surface state of graphene, the positions of the chemical functional groups, their interactions with the underlying Cu substrate, and their influences on the growth of graphene.     

A correlation model to compute the incidence angle modifier and to estimate its effect on collectible solar radiation

Radiation transmittance and absorptance of materials vary according to the angle of incidence of the incoming solar radiation. Therefore, the efficiency of most solar converters (thermal or photovoltaic) at a given radiation amount is a function of the sun's position through the angle of incidence. This problem is accounted for by the Incidence Angle Modifier, which is considered in this paper. An analytic expression for the incidence angle modifier, based on meteorological data or on geographic and geometric parameters, has been developed; this expression includes the effect of beam and diffuse radiation as well as the global influence. A comparison between measured data and computed from our model has given a very good correlation, the results being within a ±3% of difference for horizontal and tilted planes, and within ±17% for vertical surfaces, on average. The method also computes the collectible solar energy within a 5% error for thresholds up to 300 W m⁻². The method has been validated for more than 30 locations of south and west Europe.