bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Cr2O3 nanoparticles on the physical properties of polyvinyl alcohol
Authors: Hassen A. , El Sayed A. M. , Morsi W. M. , El-Sayed S.
Published: November 2012

Nano-sized chromium oxide (Cr2O3) was synthesized by sol-gel method and mixed with polyvinyl alcohol (PVA) to produce nanocomposite films. Scanning electron microscopy (SEM) was used to observe the morphology and dispersion of Cr2O3 on the surface of the PVA films. X-ray diffraction (XRD) was performed on nano-sized Cr2O3, pure PVA, and Cr2O3/PVA composites. Based on the results of both XRD and high-resolution transmission electron microscopy (HR-TEM), the average particle size of the Cr2O3 was ≈ 46 nm. Differential scanning calorimetry (DSC) showed that the thermal stability and degree of crystallinity of the PVA were reinforced by the addition of Cr2O3 nanoparticles. The absorbance and extinction coefficients of the composites were studied in the UV-vis range and compared with those of pure PVA. The optical energy band gap, Eg, was calculated. Dielectric constant, ε′, dielectric loss modulus, M″, and ac conductivity, σac, of all samples were measured within temperature and frequency ranges of 300–468 K and 10 kHz-2 MHz, respectively. According to the frequency and temperature dependence of the dielectric loss modulus, M″, the observed α-relaxation peak was due to the micro-Brownian motion of the polymer main chains. The behavior of σac(f) for the composite films indicated that the conduction mechanism was correlated barrier hopping (CBH). The results of this work were discussed and compared with those of previous studies of PVA composites.
Comparison of thermoelectric properties of p-type nanostructured bulk Si0.8Ge0.2 alloy with Si0.8Ge0.2 composites embedded with CrSi2 nano-inclusisons
Authors: Zamanipour Zahra , Vashaee Daryoosh
Published: November 2012

P-type nanostructured bulk Si0.8Ge0.2 and Si0.8Ge0.2 composites with CrSi2 nano-crystallite inclusions were synthesized via sintering approach. The composite structure showed power factor enhancement compared with nanostructured Si0.8Ge0.2 alloy. The experimental data for both structures were modeled with solving the multiband Boltzmann transport equation in the relaxation time approximation for charge carriers and phonons. The Si0.8Ge0.2 crystallite boundary scattering was modeled by a cylindrical potential barrier at the interfaces and the effects of CrSi2 nano-inclusions were modeled by spherical potential barriers in the Si0.8Ge0.2 lattice. The model calculations revealed that the enhancement in power factor is not an effect of hot carrier energy filtering, but it is due to the enhancement in charge carrier mobility in the composite structure. The analysis of charge carrier mobility components showed that while in nanostructured Si0.8Ge0.2 the ionize impurities and acoustic phonons are dominant scatterers, in the composite structure the scattering by CrSi2 nano-inclusions and acoustic phonons are dominant. The optimum size of the CrSi2 nano-inclusions for enhancing ZT was predicted with the characteristic that ZT drops rapidly when the crystallite size decreases, but it changes slowly as it is increased above its optimum value.
Photoluminescence study of magnetic spin clusters and their temperature evolution in Cd0.70Mn0.30Te spin-glass compound
Authors: Gnatenko Yu. P. , Bukivskij P. M.
Published: November 2012

We have investigated microscopic magnetic spin states (MMSSs) (“loose spins, finite superparamagnetic, ‘locked’ and infinite clusters”) both above and below the freezing temperature in Cd0.70Mn0.30Te spin glass (SG). We used the localized exciton magnetic polarons, which we observed in the photoluminescence spectra, as a probe. This makes it possible to estimate the MMSS's relative concentrations and to study their temperature evolution and thus to elucidate one of the most important issues in this field of research. Furthermore, the findings described here open new prospects for further studies of spin freezing in the different SGs, especially, in dilute magnetic semiconductors.
Dislocation structure in AlN films induced by in situ transmission electron microscope nanoindentation
Authors: Tokumoto Yuki , Kutsukake Kentaro , Ohno Yutaka , Yonenaga Ichiro
Published: November 2012

To elucidate dislocation generation and propagation processes in AlN films containing a high density of grown-in threading dislocations (TDs), in situ nanoindentation (NI) was performed in a transmission electron microscope at room temperature. Dislocations with the Burgers vector b = 1/3<12¯10> were introduced not only on the primary slip plane, i.e., the (0001) basal planes, but also on the {101¯1} and {101¯2} pyramidal planes. The results are explained by considering the distribution of the resolved shear stress. It was found that the dislocations induced by NI interact with grown-in TDs: (1) for the NI-induced dislocations on pyramidal planes, edge grown-in TDs induce cross slip to basal planes, and (2) for the NI-induced dislocations on basal planes, screw grown-in TDs prevent their propagation, while edge grown-in TDs do not.
Effects of volumetric dilution on anaerobic digestion of food waste
Authors: Fang Lou Xian , Nair Jaya , Ho Goen
Published: November 2012

Despite the increasing number of small scale digesters operating, there remains a lack of information with regards to performance optimization from an everyday user's standpoint. The objective of this study was to determine the effects of volumetric dilution and food waste composition on digester performance. Batch experiments utilizing food waste majoring in carbohydrate, protein, lipid, and cellulose, subjected to five concentrations of volumetric dilution (3.7%–17.1% total solids (TS)), were conducted. Irregardless of volumetric dilution, all assays achieved substrate degradation higher than 82.5% and did not suffer methanogenic inhibition, when provided with retention times comparable to those used in small scale digesters. Protein rich and cellulose rich waste achieved the highest methane potential varying between 0.410–0.539 m3/kg volatile solids (VS) and 0.450–0.535 m3/kg VS, respectively. Protein rich assays were also observed to be the first to achieve 50% of its Bo irregardless of concentrations, followed by carbohydrates and cellulose, and lipids having a considerably longer methanation time. Results saw an increase in total methane generated but a decrease in specific yield as % total solid increased. To successfully digest lipid rich waste a dilution no lesser than 1:4 was required.
On Fermat's principle for causal curves in time oriented Finsler spacetimes
Authors: Gallego Torromé Ricardo , Piccione Paolo , Vitório Henrique
Published: November 2012

In this work, a version of Fermat's principle for causal curves with the same energy in time orientable Finsler spacetimes is proved. We calculate the second variation of the time arrival functional along a geodesic in terms of the index form associated with the Finsler spacetime Lagrangian. Then the character of the critical points of the time arrival functional is investigated and a Morse index theorem in the context of Finsler spacetime is presented.
On π-stacking, C-H/π, and halogen bonding interactions in halobenzene clusters: Resonant two-photon ionization studies of chlorobenzene
Authors: Muzangwa Lloyd , Nyambo Silver , Uhler Brandon , Reid Scott A.
Published: November 2012

Noncovalent interactions such as hydrogen bonding, π-π stacking, CH/π interactions, and halogen bonding play crucial roles in a broad spectrum of chemical and biochemical processes, and can exist in cooperation or competition. Here we report studies of the homoclusters of chlorobenzene, a prototypical system where π-π stacking, CH/π interactions, and halogen bonding interactions may all be present. The electronic spectra of chlorobenzene monomer and clusters (Clbz)n with n = 1-4 were obtained using resonant 2-photon ionization in the origin region of the S0–S1 (ππ*) state of the monomer. The cluster spectra show in all cases a broad spectrum whose center is redshifted from the monomer absorption. Electronic structure calculations aid in showing that the spectral broadening arises in large part from inhomogeneous sources, including the presence of multiple isomers and Franck-Condon (FC) activity associated with geometrical changes induced by electronic excitation. Calculations at the M06-2x/aug-cc-pVDZ level find in total five minimum energy structures for the dimer, four π-stacked structures, and one T-shaped, and six representative minimum energy structures were found for the trimer. The calculated time-dependent density functional theory spectra using range-separated and meta-GGA hybrid functionals show that these isomers absorb over a range that is roughly consistent with the breadth of the experimental spectra, and the calculated absorptions are redshifted with respect to the monomer transition, in agreement with experiment. Due to the significant geometry change in the electronic transition, where for the dimer a transition from a parallel displaced to sandwich structure occurs with a reduced separation of the two monomers, significant FC activity is predicted in low frequency intermolecular modes.
Time-resolved photoelectron imaging of excited state relaxation dynamics in phenol, catechol, resorcinol, and hydroquinone
Authors: Livingstone Ruth A. , Thompson James O. F. , Iljina Marija , Donaldson Ross J. , Sussman Benjamin J. , Paterson Martin J. , Townsend Dave
Published: November 2012

Time-resolved photoelectron imaging was used to investigate the dynamical evolution of the initially prepared S1 (ππ*) excited state of phenol (hydroxybenzene), catechol (1,2-dihydroxybenzene), resorcinol (1,3-dihydroxybenzene), and hydroquinone (1,4-dihydroxybenzene) following excitation at 267 nm. Our analysis was supported by ab initio calculations at the coupled-cluster and CASSCF levels of theory. In all cases, we observe rapid (<1 ps) intramolecular vibrational redistribution on the S1 potential surface. In catechol, the overall S1 state lifetime was observed to be 12.1 ps, which is 1–2 orders of magnitude shorter than in the other three molecules studied. This may be attributed to differences in the H atom tunnelling rate under the barrier formed by a conical intersection between the S1 state and the close lying S2 (πσ*) state, which is dissociative along the O–H stretching coordinate. Further evidence of this S1/S2 interaction is also seen in the time-dependent anisotropy of the photoelectron angular distributions we have observed. Our data analysis was assisted by a matrix inversion method for processing photoelectron images that is significantly faster than most other previously reported approaches and is extremely quick and easy to implement.
Experimental and theoretical investigations on photoabsorption and photoionization of trimethylphosphate in the vacuum-ultraviolet energy range
Authors: Homem M. G. P. , López-Castillo A. , Barbatti M. , Rosa L. F. S. , Iza P. , Cavasso-Filho R. L. , Farenzena L. S. , Lee M. T. , Iga I.
Published: November 2012

In this work, we report a joint experimental-theoretical investigation on interaction of vacuum-ultraviolet radiation with trimethylphosphate (TMP) molecule (C3H9O4P) in gas phase. This species together with tetrahydrofuran (THF) are model compounds of deoxyribose nucleic acids (DNA)/ribose nucleic acids (RNA) backbone. Absolute photoabsorption cross sections (σa) and ionization yields (η) are measured using the double-ion-chamber technique in the 11.0–21.45 eV energy range. Photoionization (σi) and neutral-decay (σn) cross sections in absolute scale are also derived. Moreover, theoretical photoabsorption cross sections are calculated using the time-dependent density functional theory from the excitation threshold up to 16 eV. Good agreement between the present calculated and experimental photoabsorption cross sections in the 11.0–14.5 eV range is encouraging. Also, the present measured data of σa and σi for TMP are about 1.3 and 1.5 times of those of THF, respectively. Thus, the experimental evidences that the majority of strand breaks being located at sugar rings in the irradiated DNA/RNA backbone moiety may be induced by a possible migration of the hole, initially created at phosphate group, to the linked sugar groups. Finally, absolute partial photoionization cross sections are derived from the experimental time-of-flight mass spectra.
Reactive-ion-etched graphene nanoribbons on a hexagonal boron nitride substrate
Authors: Bischoff D. , Krähenmann T. , Dröscher S. , Gruner M. A. , Barraud C. , Ihn T. , Ensslin K.
Published: November 2012

We report on the fabrication and electrical characterization of both single layer graphene micron-sized devices and nanoribbons on a hexagonal boron nitride substrate. We show that the micron-sized devices have significantly higher mobility and lower disorder density compared to devices fabricated on silicon dioxide substrate in agreement with previous findings. The transport characteristics of the reactive-ion-etched graphene nanoribbons on hexagonal boron nitride, however, appear to be very similar to those of ribbons on a silicon dioxide substrate. We perform a detailed study in order to highlight both similarities as well as differences. Our findings suggest that the edges have an important influence on transport in reactive-ion-etched graphene nanodevices.
The buoyancy-driven motion of a single skirted bubble or drop rising through a viscous liquid
Authors: Ohta Mitsuhiro , Sussman Mark
Published: November 2012

The buoyancy-driven motion of a single skirted bubble or drop rising through a viscous liquid is computationally explored by way of 3d-axisymmetric computations. The Navier-Stokes equations for incompressible two-fluid flow are solved numerically in which the coupled level-set and volume-of-fluid method is used to simulate the deforming bubble/drop boundary and the interface jump conditions on the deforming boundary are enforced through a sharp interface numerical treatment. Dynamic, block structured adaptive grid refinement is employed in order to sufficiently resolve the thin skirts. Results on the sensitivity of the thickness of trailing bubble/drop skirts to the density ratio and viscosity ratio are reported. It is shown that both the density ratio (not the density difference) and the viscosity ratio effect the skirt thickness. Previous theory for predicting skirt thickness can be refined as a result of our calculations. It is also discovered that the formation of thin skirts for bubbles and drops have little effect on the rise velocity. In other words, the measured Re number for cases without skirt formation have almost the same values for Re as cases with a thin skirt.
Nanoxerography utilizing bipolar charge patterns
Authors: Lim Kyunghoon , Lee Jung-Rok , Lee Heechul , Pikhitsa Peter V. , You Sukbeom , Gyu Woo Chang , Kim Pilnam , Suh Kahp Y. , Choi Mansoo
Published: November 2012

We report a nanoxerography utilizing alternating bipolar surface charge patterns. Unlike a conventional nanoxerography using unipolar charge patterns, the present concept generates convex shaped equipotential planes with large curvature that can act as nanoscopic electrostatic lenses. Through these lenses, positively charged aerosol nanoparticles are focused into the center region of the negative surface charge pattern leading to the significant reduction of particle deposition width. We also demonstrate that the focusing capability can be controlled by changing ion flow rates. Numerical simulations of the trajectory and deposition of charged particles were done to support experimental results.
Size-dependent chemical reactivity of porous graphene for purification of exhaust gases
Authors: Si Chen , Zhou Gang
Published: November 2012

From the structural characteristics of pores evolving from the vacancy, the structure-dependent nature of localized states, and the role of electronic states in the reaction, we elucidate size effects on the chemical reactivity of porous graphene using density functional theory. The coupling of conjugated π electrons of graphene with localized defect states allows for the reduction reaction or adsorption of exhaust gases on the edge atoms. The charge redistribution, ascertained from the coupling response, activates the weak C-C bond states at the corners, facilitating the dissociation of exhaust gas (e.g., NO). The size matching effect makes that the dissociation barrier of NO on the vacancy is smaller than 8.30 kcal/mol; whereas, larger pores only capture NO. Following the coupling-response mechanism, we propose the structural requirements for chemical applications of porous graphene: the shape and size of the pores are comparable in scale with those of purified molecules.
Corrosion of Si-O based porous low-k dielectrics
Authors: Hall A. B. , Irvine G. J. , Gates S. M. , Lane M. W.
Published: November 2012

The corrosion behavior of low-k dielectric films used in today's microelectronic interconnects is reported. We study the dielectric constant, k, range 2.7 to 2.05, with all materials based on a Si-O-Si network. A corrosion mechanism based upon the reaction of water molecules with strained crack-tip bonds is used to model crack velocity vs. applied strain energy release rate curves and to extract key atomistic parameters for each dielectric. It is found that bond strength is invariant and bond density varies linearly with k. The data indicate that no new mechanism plays a part in the corrosion of these Si-O-Si based films with dielectric constants down to ∼2.
Observation of boron diffusion in an annealed Ta/CoFeB/MgO magnetic tunnel junction with standing-wave hard x-ray photoemission
Authors: Greer A. A. , Gray A. X. , Kanai S. , Kaiser A. M. , Ueda S. , Yamashita Y. , Bordel C. , Palsson G. , Maejima N. , Yang S.-H. , Conti G. , Kobayashi K. , Ikeda S. , Matsukura F. , Ohno H. , Schneider C. M. , Kortright J. B. , Hellman F. , Fadley C. S.
Published: November 2012

The CoFeB/MgO system shows promise as a magnetic tunnel junction with perpendicular magnetization and low critical current densities for spin-torque driven magnetization switching. The distribution of B after annealing is believed to be critical to performance. We have studied the distribution of B in a Ta/Co0.2Fe0.6B0.2/MgO sample annealed at 300 °C for 1 h with standing-wave hard x-ray photoemission spectroscopy (SW-HXPS). Comparing experimental rocking curve data to x-ray optical calculations indicates diffusion of 19.5% of the B uniformly into the MgO and of 23.5% into a thin TaB interface layer. SW-HXPS is effective for probing depth distributions in such spintronic structures.
Wheatstone bridge piezoresistive sensing for bulk-mode micromechanical resonator
Authors: Wu Guoqiang , Xu Dehui , Xiong Bin , Wang Yuelin
Published: November 2012

A balanced wheatstone bridge technique for piezoresistive detection in micromechanical resonators is demonstrated. Two identical beam resonators, which vibrate in the length extensional mode with 180° phase shift, are connected in serial to compose a wheatstone bridge. With the differential actuation configuration, this approach eliminates the capacitive feedthrough signal, which may heavily bury the piezoresistive signal of the resonator in traditional piezoresistive sensing approach. The proposed technique is experimentally validated. Experimental results show that the capacitive signal embedded in the piezoresistive sensing approach is nearly eliminated. This method provides an effective way for purely piezoresistive sensing of micromechanical resonators.
Improvement of nonlinear harmonics in free electron laser with planar wiggler
Authors: Bazouband F. , Maraghechi B.
Published: November 2012

Spontaneous emission of free electron laser with planar wiggler and ion-channel guiding is calculated analytically and possibility of emission at up-shifted wiggler or ion-channel betatron frequency and their harmonics has been found. To investigate the nonlinear odd harmonics, a set of self-consistent nonlinear differential equations that governs the evolution of radiation and electron beam are derived and solved numerically by Runge-Kutta method. Using the simulation code, gain improvement of third harmonic is studied in the range of microwave frequency by applying ion-channel guiding for a cold beam. It is shown that the combination of the ion-channel and a prebunched electron beam increases the amplitude of the third harmonic of the radiation and decreases its saturation length. The relation between the linear and nonlinear harmonics is discussed.
Spontaneous healing and growth of locked magnetic island chains in toroidal plasmas
Authors: Fitzpatrick R. , Waelbroeck F. L.
Published: November 2012

Recent experiments have demonstrated that locked magnetic island chains in stellarator plasmas spontaneously heal under certain conditions, and spontaneously grow under others. A formalism initially developed to study magnetic island dynamics in tokamak plasmas is employed to investigate this phenomenon. It is found that island healing/growth transitions can be caused either by a breakdown in torque balance in the vicinity of the island chain, or by an imbalance between the various terms in the island width evolution equation. The scaling of the healing/growth thresholds with the standard dimensionless plasma parameters β, ν∗, and ρ∗ is determined. In accordance with the experimental data, it is found that island healing generally occurs at high β and low ν∗, and island growth at low β and high ν∗. In further agreement, it is found that island healing is accompanied an ion poloidal velocity shift in the electron diamagnetic direction, and island growth by a velocity shift in the ion diamagnetic direction. Finally, it is found that there is considerable hysteresis in the healing/growth cycle, as is also seen experimentally.
Distinguishing similar patterns with different underlying instabilities: Effect of advection on systems with Hopf, Turing-Hopf, and wave instabilities
Authors: Berenstein Igal
Published: November 2012

Systems with the same local dynamics but different types of diffusive instabilities may show the same type of patterns. In this paper, we show that under the influence of advective flow the scenario of patterns that is formed at different velocities change; therefore, we propose the use of advective flow as a tool to uncover the underlying instabilities of a reaction-diffusion system.
Dispersion due to electroosmotic flow in a circular microchannel with slowly varying wall potential and hydrodynamic slippage
Authors: Ng Chiu-On , Zhou Qi
Published: November 2012

An analysis using the lubrication approximation is performed for the dispersion of a neutral non-reacting solute due to electro-osmotic flow through a circular channel under the combined effects of longitudinal non-uniformity of potential and hydrodynamic slippage on the channel wall. The wall is periodically patterned for the charge and slip distributions, with a wavelength much longer than the channel radius. It is shown that the presence of slip can greatly amplify the increased dispersion caused by induced pressure gradient brought about by the non-uniformity of wall potential. Non-uniform wall potential interacting with non-uniform slip can give rise to effects much different from those when the potential and slip are both uniformly distributed and equal to the averages of the non-uniform distributions. Mobility and dispersion associated with recirculating flow resulting from oppositely charged slipping region is also examined.
Buried anti resonant reflecting optical waveguide based on porous silicon material for an integrated Mach Zehnder structure
Authors: Hiraoui M. , Guendouz M. , Lorrain N. , Haji L. , Oueslati M.
Published: November 2012

A buried anti resonant reflecting optical waveguide for an integrated Mach Zehnder structure based on porous silicon material is achieved using a classical photolithography process. Three distinct porous silicon layers are then elaborated in a single step, by varying the porosity (thus the refractive index) and the thickness while respecting the anti-resonance conditions. Simulations and experimental results clearly show the antiresonant character of the buried waveguides. Significant variation of the reflectance and light propagation with different behavior depending on the polarization and the Mach Zehnder dimensions is obtained. Finally, we confirm the feasibility of this structure for sensing applications.
Interface engineering between metal electrode and GeO2 dielectric for future Ge-based metal-oxide-semiconductor technologies
Authors: Ogawa Shingo , Hideshima Iori , Minoura Yuya , Yamamoto Takashi , Yasui Asami , Miyata Hiroaki , Kimura Kosuke , Ito Toshihiko , Hosoi Takuji , Shimura Takayoshi , Watanabe Heiji
Published: November 2012

Interfacial reactions between a metal-gate electrode and GeO2 dielectric in Ge-based metal-oxide-semiconductor (MOS) devices have been investigated by several analytical techniques, and we have demonstrated a method to suppress the interfacial reactions. Although no reaction occurs at the Au/GeO2 interface, a significant reaction was observed at the Al/GeO2 interface, which leads to increases in the leakage current and defect states in an MOS capacitor. While Al is oxidized at the Al/GeO2 interface, GeO2 is reduced to form Ge-Ge and Ge-Al bonding units during the early stage of the Al deposition. Moreover, the Ge-Al alloy segregates to the Al-electrode surface during the sequent Al deposition. These interfacial reactions are dramatically suppressed by insertion of ultrathin Al2O3 into the Al/GeO2 interface.
Radial p-n junction macroporous silicon solar cell on p-type upgraded metallurgical-grade silicon substrate
Authors: Zhao L. , Li Z. C. , Diao H. W. , Li H. L. , Zhou C. L. , Wang W. J.
Published: November 2012

Macroporous silicon was fabricated on p-type upgraded metallurgical-grade (UMG) c-Si substrate with the resistivity of about 0.1–3 Ω cm, by metal-catalyzed electrochemical etching (MCECE). Ag nanoparticle catalyst was first fabricated on the c-Si substrate. Then, the electrochemical etching was performed. By optimizing the MCECE processes carefully, the macroporous silicon was successfully obtained with the pore width up to about 400 nm and the pore depth of 2–5 μm. After that, the radial amorphous/crystalline silicon heterojunction (SHJ) structure was prepared by conformally depositing a-Si:H i-layer and n-layer on the macroporous silicon via plasma-enhanced chemical vapor deposition (PECVD) at 200 °C, followed by depositing indium tin oxide front contact and Ag back contact via magnetron sputtering and thermal evaporation, respectively. As a result, the demonstrated radial p-n junction macroporous silicon solar cell with the unoptimized SHJ structure gave out a conversion efficiency of 3.67% under the standard AM1.5 illumination, which indicated a potential to make high performance radial p-n junction solar cell on UMG c-Si substrate.
Woodchip drying in a screw conveyor dryer
Authors: Kaplan Ozgur , Celik Cenk
Published: November 2012

Moisture content of raw biomass materials is a crucial parameter for system efficiency and the main purpose of the drying process is to reduce moisture content of the wet biomass. In this study, the drying characteristics of woodchip dried in a screw conveyor dryer had investigated experimentally. The experimental results demonstrated that drying rate had increased with the increasing drying air temperature and flow rate; however, the amount of volatile organic matters in the sample has kept constant. Furthermore, the results have showed that the best drying conditions in this study is 30 m3/h drying airflow rate, 200 °C drying air temperature, and co-current dryer type. With these conditions, moisture content of woodchip decreased from 60% to 27% (wet basis, mass %).
Feasibility analysis of megawatt scale solar thermal power plants
Authors: Reddy K. S. , Ravi Kumar K. , Devaraj Vikramaditya A.
Published: November 2012

In this article, feasibility analysis of solar thermal power plants is carried out for large scale power generation. Three different configurations of concentrating solar power technologies such as linear Fresnel reflector collector (LFRC), parabolic trough collector (PTC), and power tower (PT) are analyzed for power generation in stand-alone mode and various plant capacities such as 1 MWe, 5 MWe, 10 MWe, 30 MWe, and 50 MWe. The maximum achievable steam conditions in LFRC system has been considered for all the power plant capacities as 55 bar and 270 °C. In case of parabolic trough and power tower, the steam parameters have been considered as 60 bar, 370 °C for 1 MWe, 65 bar, 400 °C for 5 MWe, 65 bar, 410 °C for 10 MWe, 100 bar, 410 °C for 30 MWe, and 100 bar, 410 °C for 50 MWe. The feasibility of stand-alone solar power plants (SASPPs) is compared with coal fired power plant (CFPP) and solar aided coal fired power plant (SACFPP). The feasibility analysis in terms of performance and levelised electricity cost (LEC) is carried out for various technologies with capacities. It is observed that the LFRC power plants are relatively less efficient than others due to lower optical and thermal efficiency. The energy and exergy efficiencies of a 50 MWe LFRC power plant are found as 12.17% and 17.21%, respectively. The efficiency of 50 MWe solar PTC power plants is found as 23.16% which is higher than other technologies. The net exergy efficiency of PTC power plants increases from 23.14% to 32.76% for the plant capacity increases from 1 MWe to 50 MWe. It is observed that the exergy efficiency decreases from 22.57% to 19.65% as plant capacity increases from 1 MWe to 10 MWe due to shading and blocking for PT power plants and then increases to maximum of 23.33% for the 50 MWe power plant. The exergy efficiencies of 50 MWe CFPP and SACFPP have been estimated as 28.17% and 28.21%, respectively. The environmental benefits of stand-alone solar power plants are estimated in terms of CO2 mitigations and compared with CFPP. The LEC of CFPP, SACFPP, and SASPP is found as INR 3.56/kWh, INR 3.60/kWh, and INR 8.48/kWh, respectively. The discounted payback period, benefit-to-cost ratio, and net present value of all the power plants are also estimated.
Electrically induced decrease of magnetization in Ca3Mn2O7
Authors: Zhu Wenka , Pi Li , Huang Yuanjie , Tan Shun , Zhang Yuheng
Published: November 2012

The magnetoelectric effect of Ca3Mn2O7 is verified by measuring the electric field dependence of magnetization. The magnetization is reduced by the electric field, as much as nearly 6% at 4 K under 100 Oe magnetic field and 40 kV/m electric field. There are two theoretical models in previous researches. Harris's model [A. B. Harris, Phys. Rev. B 84, 064116 (2011)], based on the rotating effect of electric field predicts electric-field-direction dependence of the magnetization decrease. Benedek and Fennie's model [N. A. Benedek and C. J. Fennie, Phys. Rev. Lett. 106, 107204 (2011)] emphasizes the stretching effect of electric field and predicts direction independence. The experimental results support Benedek and Fennie's framework and conflict with Harris's prediction. We argue that the large anisotropy and the antiferromagnetic nature impede the rotation of domains and suppress the rotating effect. In the coupling of magnetic ordering and ferroelectric ordering, the oxygen octahedron tilt distortion (X3−) plays an essential role.
Quantitative phase imaging of human red blood cells using phase-shifting white light interference microscopy with colour fringe analysis
Authors: Singh Mehta Dalip , Srivastava Vishal
Published: November 2012

We report quantitative phase imaging of human red blood cells (RBCs) using phase-shifting interference microscopy. Five phase-shifted white light interferograms are recorded using colour charge coupled device camera. White light interferograms were decomposed into red, green, and blue colour components. The phase-shifted interferograms of each colour were then processed by phase-shifting analysis and phase maps for red, green, and blue colours were reconstructed. Wavelength dependent refractive index profiles of RBCs were computed from the single set of white light interferogram. The present technique has great potential for non-invasive determination of refractive index variation and morphological features of cells and tissues.
Measuring the stability of polarization orientation in high intensity laser filaments in air
Authors: Sheinfux A. H. , Schleifer E. , Papeer J. , Fibich G. , Ilan B. , Zigler A.
Published: November 2012

We suggest a method for measuring the polarization orientation of high-intensity beams, by analyzing the damage structures on metal targets, created by laser-plasma-metal interaction. We apply our method on laser filaments and demonstrate stability and instability of the polarization orientation dynamics. Our experimental results show that the polarization orientation of linearly polarized input beams during filamentation is stable, whereas that of elliptically polarized input beams is not. The results are supported by an analytical model.
Metastable ultrathin crystal in thermally grown SiO2 film on Si substrate
Authors: Kimoto Koji , Tanaka Hiroki , Matsushita Daisuke , Tatsumura Kosuke , Takeno Shiro
Published: November 2012

A silicon dioxide film on a silicon substrate is the most essential element in semiconductor devices and various advanced materials. We have elucidated the atomic structure of SiO2 films using low-dose scanning transmission electron microscopy (STEM). We have visualized a metastable crystalline SiO2 layer near a silicon substrate, which was not revealed in previous studies probably due to the vitrification caused by electron irradiation. Our experimental results also suggest a crystallographic nature of various surface oxides.
Nitrous oxide emissions from subtropical horticultural soils: a time series analysis
Authors: Huang Xiaodong , Grace Peter , Weier Keith , Mengersen Kerrie
Published: November 2012

Time series regression models were used to examine the influence of environmental factors (soil water content and soil temperature) on the emissions of nitrous oxide (N2O) from subtropical soils, by taking into account temporal lagged environmental factors, autoregressive processes, and seasonality for three horticultural crops in a subtropical region of Australia. Fluxes of N2O, soil water content, and soil temperature were determined simultaneously on a weekly basis over a 12-month period in South East Queensland. Annual N2O emissions for soils under mango, pineapple, and custard apple were 1590, 1156, and 2038 g N2O-N/ha, respectively, with most emissions attributed to nitrification. The N2O-N emitted from the pineapple and custard apple crops was equivalent to 0.26 and 2.22%, respectively, of the applied mineral N. The change in soil water content was the key variable for describing N2O emissions at the weekly time-scale, with soil temperature at a lag of 1 month having a significant influence on average N2O emissions (averaged) at the monthly time-scale across the three crops. After accounting for soil temperature and soil water content, both the weekly and monthly time series regression models exhibited significant autocorrelation at lags of 1–2 weeks and 1–2 months, and significant seasonality for weekly N2O emissions for mango crop and for monthly N2O emissions for mango and custard apple crops in this location over this time-frame. Time series regression models can explain a higher percentage of the temporal variation of N2O emission compared with simple regression models using soil temperature and soil water content as drivers. Taking into account seasonal variability and temporal persistence in N2O emissions associated with soil water content and soil temperature may lead to a reduction in the uncertainty surrounding estimates of N2O emissions based on limited sampling effort.
Soil selenium in a forested seabird colony: distribution, sources, uptake by plants, and comparison with non-seabird sites
Authors: Hawke David J. , Wu Jun-Ru
Published: November 2012

Seabirds vector selenium (Se) into terrestrial ecosystems in Antarctica and on tropical coral islands, but factors controlling distribution within affected soils are unknown, especially in temperate regions. At a Westland petrel (Procellaria westlandica) breeding colony on mainland New Zealand, the concentration of Se in petrel guano (3.6 mg kg–1) exceeded soil parent material (0.8 mg kg–1) and in all but two soil samples (range 1.2–4.2 mg kg–1; n = 52). External Se (Se not derived from parent material) accounted for 64 ± 9% (mean ± s.d.) of soil Se. Measurements were also made at a former seabird breeding site, and at a site with no Holocene seabird breeding. Median surface-soil Se concentrations (mg kg–1) were in the order burrow soil (2.6) > adjacent forest floor (2.2) > former breeding site (1.0) > control site (0.2), with significant differences between burrow soil and (1) the former breeding site and (2) the control site. In a linear regression model, soil pH, and δ15N were the only significant predictors of external Se in colony soil. The correlations are consistent with seabird input driving both the Se supply and increased sorptive uptake in an environment acidified by seabird guano. Despite the enhanced Se in colony soil, median foliage concentrations (tree fern 0.05 mg kg–1, nikau 0.08 mg kg–1) were close to the accepted minimum for herbivore nutrition. Seabirds therefore contribute significant Se to breeding colony soils in temperate areas, but this is not necessarily transferred to plant foliage.
Variable evolutionary routes to host establishment across repeated rabies virus host shifts among bats
Authors: Streicker Daniel G. , Altizer Sonia M. , Velasco-Villa Andrés , Rupprecht Charles E.
Published: November 2012

Determining the genetic pathways that viruses traverse to establish in new host species is crucial to predict the outcome of cross-species transmission but poorly understood for most host–virus systems. Using sequences encoding 78% of the rabies virus genome, we explored the extent, repeatability and dynamic outcome of evolution associated with multiple host shifts among New World bats. Episodic bursts of positive selection were detected in several viral proteins, including regions associated with host cell interaction and viral replication. Host shifts involved unique sets of substitutions, and few sites exhibited repeated evolution across adaptation to many bat species, suggesting diverse genetic determinants over host range. Combining these results with genetic reconstructions of the demographic histories of individual viral lineages revealed that although rabies viruses shared consistent three-stage processes of emergence in each new bat species, host shifts involving greater numbers of positively selected substitutions had longer delays between cross-species transmission and enzootic viral establishment. Our results point to multiple evolutionary routes to host establishment in a zoonotic RNA virus that may influence the speed of viral emergence.
Electronic sensor and actuator webs for large-area complex geometry cardiac mapping and therapy
Authors: Kim Dae-Hyeong , Ghaffari Roozbeh , Lu Nanshu , Wang Shuodao , Lee Stephen P. , Keum Hohyun , D’Angelo Robert , Klinker Lauren , Su Yewang , Lu Chaofeng , Kim Yun-Soung , Ameen Abid , Li Yuhang , Zhang Yihui , de Graff Bassel , Hsu Yung-Yu , Liu ZhuangJian , Ruskin Jeremy , Xu Lizhi , Lu Chi , Omenetto Fiorenzo G. , Huang Yonggang , Mansour Moussa , Slepian Marvin J. , Rogers John A.
Published: November 2012

Curved surfaces, complex geometries, and time-dynamic deformations of the heart create challenges in establishing intimate, nonconstraining interfaces between cardiac structures and medical devices or surgical tools, particularly over large areas. We constructed large area designs for diagnostic and therapeutic stretchable sensor and actuator webs that conformally wrap the epicardium, establishing robust contact without sutures, mechanical fixtures, tapes, or surgical adhesives. These multifunctional web devices exploit open, mesh layouts and mount on thin, bio-resorbable sheets of silk to facilitate handling in a way that yields, after dissolution, exceptionally low mechanical moduli and thicknesses. In vivo studies in rabbit and pig animal models demonstrate the effectiveness of these device webs for measuring and spatially mapping temperature, electrophysiological signals, strain, and physical contact in sheet and balloon-based systems that also have the potential to deliver energy to perform localized tissue ablation.
A critical role for Mnt in Myc-driven T-cell proliferation and oncogenesis
Authors: Link Jason M. , Ota Sara , Zhou Zi-Qiang , Daniel Colin J. , Sears Rosalie C. , Hurlin Peter J.
Published: November 2012

Mnt (Max's next tango) is a Max-interacting transcriptional repressor that can antagonize both the proproliferative and proapoptotic functions of Myc in vitro. To ascertain the physiologically relevant functions of Mnt and to help define the relationship between Mnt and Myc in vivo, we generated a series of mouse strains in which Mnt was deleted in T cells in the absence of endogenous c-Myc or in the presence of ectopic c-Myc. We found that apoptosis caused by loss of Mnt did not require Myc but that ectopic Myc expression dramatically decreased the survival of both Mnt-deficient T cells in vivo and Mnt-deficient MEFs in vitro. Consequently, Myc-driven proliferative expansion of T cells in vitro and thymoma formation in vivo were prevented by the absence of Mnt. Consistent with T-cell models, mouse embryo fibroblasts (MEFs) lacking Mnt were refractory to oncogenic transformation by Myc. Tumor suppression caused by loss of Mnt was linked to increased apoptosis mediated by reactive oxygen species (ROS). Thus, although theoretically and experimentally a Myc antagonist, the dominant physiological role of Mnt appears to be suppression of apoptosis. Our results redefine the physiological relationship between Mnt and Myc and requirements for Myc-driven oncogenesis.
The basis of musical consonance as revealed by congenital amusia
Authors: Cousineau Marion , McDermott Josh H. , Peretz Isabelle
Published: November 2012

Some combinations of musical notes sound pleasing and are termed “consonant,” but others sound unpleasant and are termed “dissonant.” The distinction between consonance and dissonance plays a central role in Western music, and its origins have posed one of the oldest and most debated problems in perception. In modern times, dissonance has been widely believed to be the product of “beating”: interference between frequency components in the cochlea that has been believed to be more pronounced in dissonant than consonant sounds. However, harmonic frequency relations, a higher-order sound attribute closely related to pitch perception, has also been proposed to account for consonance. To tease apart theories of musical consonance, we tested sound preferences in individuals with congenital amusia, a neurogenetic disorder characterized by abnormal pitch perception. We assessed amusics’ preferences for musical chords as well as for the isolated acoustic properties of beating and harmonicity. In contrast to control subjects, amusic listeners showed no preference for consonance, rating the pleasantness of consonant chords no higher than that of dissonant chords. Amusics also failed to exhibit the normally observed preference for harmonic over inharmonic tones, nor could they discriminate such tones from each other. Despite these abnormalities, amusics exhibited normal preferences and discrimination for stimuli with and without beating. This dissociation indicates that, contrary to classic theories, beating is unlikely to underlie consonance. Our results instead suggest the need to integrate harmonicity as a foundation of music preferences, and illustrate how amusia may be used to investigate normal auditory function.
Tissue-resident memory CD8
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T cells continuously patrol skin epithelia to quickly recognize local antigen
Authors: Ariotti Silvia , Beltman Joost B. , Chodaczek Grzegorz , Hoekstra Mirjam E. , van Beek Anna E. , Gomez-Eerland Raquel , Ritsma Laila , van Rheenen Jacco , Marée Athanasius F. M. , Zal Tomasz , de Boer Rob J. , Haanen John B. A. G. , Schumacher Ton N.
Published: November 2012

Recent work has demonstrated that following the clearance of infection a stable population of memory T cells remains present in peripheral organs and contributes to the control of secondary infections. However, little is known about how tissue-resident memory T cells behave in situ and how they encounter newly infected target cells. Here we demonstrate that antigen-specific CD8
+
T cells that remain in skin following herpes simplex virus infection show a steady-state crawling behavior in between keratinocytes. Spatially explicit simulations of the migration of these tissue-resident memory T cells indicate that the migratory dendritic behavior of these cells allows the detection of antigen-expressing target cells in physiologically relevant time frames of minutes to hours. Furthermore, we provide direct evidence for the identification of rare antigen-expressing epithelial cells by skin-patrolling memory T cells in vivo. These data demonstrate the existence of skin patrol by memory T cells and reveal the value of this patrol in the rapid detection of renewed infections at a previously infected site.
Bioinspired multivalent DNA network for capture and release of cells
Authors: Zhao Weian , Cui Cheryl H. , Bose Suman , Guo Dagang , Shen Chong , Wong Wesley P. , Halvorsen Ken , Farokhzad Omid C. , Teo Grace Sock Leng , Phillips Joseph A. , Dorfman David M. , Karnik Rohit , Karp Jeffrey M.
Published: November 2012

Capture and isolation of flowing cells and particulates from body fluids has enormous implications in diagnosis, monitoring, and drug testing, yet monovalent adhesion molecules used for this purpose result in inefficient cell capture and difficulty in retrieving the captured cells. Inspired by marine creatures that present long tentacles containing multiple adhesive domains to effectively capture flowing food particulates, we developed a platform approach to capture and isolate cells using a 3D DNA network comprising repeating adhesive aptamer domains that extend over tens of micrometers into the solution. The DNA network was synthesized from a microfluidic surface by rolling circle amplification where critical parameters, including DNA graft density, length, and sequence, could readily be tailored. Using an aptamer that binds to protein tyrosine kinase-7 (PTK7) that is overexpressed on many human cancer cells, we demonstrate that the 3D DNA network significantly enhances the capture efficiency of lymphoblast CCRF-CEM cells over monovalent aptamers and antibodies, yet maintains a high purity of the captured cells. When incorporated in a herringbone microfluidic device, the 3D DNA network not only possessed significantly higher capture efficiency than monovalent aptamers and antibodies, but also outperformed previously reported cell-capture microfluidic devices at high flow rates. This work suggests that 3D DNA networks may have broad implications for detection and isolation of cells and other bioparticles.