bluuebunny/crossref_metadata_2025 huggingface dataset:
Bacteria, phages and pigs: the effects of in-feed antibiotics on the microbiome at different gut locations
Authors: Looft Torey , Allen Heather K , Cantarel Brandi L , Levine Uri Y , Bayles Darrell O , Alt David P , Henrissat Bernard , Stanton Thaddeus B
Published: February 2014

Disturbance of the beneficial gut microbial community is a potential collateral effect of antibiotics, which have many uses in animal agriculture (disease treatment or prevention and feed efficiency improvement). Understanding antibiotic effects on bacterial communities at different intestinal locations is essential to realize the full benefits and consequences of in-feed antibiotics. In this study, we defined the lumenal and mucosal bacterial communities from the small intestine (ileum) and large intestine (cecum and colon) plus feces, and characterized the effects of in-feed antibiotics (chlortetracycline, sulfamethazine and penicillin (ASP250)) on these communities. 16S rRNA gene sequence and metagenomic analyses of bacterial membership and functions revealed dramatic differences between small and large intestinal locations, including enrichment of Firmicutes and phage-encoding genes in the ileum. The large intestinal microbiota encoded numerous genes to degrade plant cell wall components, and these genes were lacking in the ileum. The mucosa-associated ileal microbiota harbored greater bacterial diversity than the lumen but similar membership to the mucosa of the large intestine, suggesting that most gut microbes can associate with the mucosa and might serve as an inoculum for the lumen. The collateral effects on the microbiota of antibiotic-fed animals caused divergence from that of control animals, with notable changes being increases in Escherichia coli populations in the ileum, Lachnobacterium spp. in all gut locations, and resistance genes to antibiotics not administered. Characterizing the differential metabolic capacities and response to perturbation at distinct intestinal locations will inform strategies to improve gut health and food safety.
A thermodynamic theory of microbial growth
Authors: Desmond-Le Quéméner Elie , Bouchez Théodore
Published: February 2014

Our ability to model the growth of microbes only relies on empirical laws, fundamentally restricting our understanding and predictive capacity in many environmental systems. In particular, the link between energy balances and growth dynamics is still not understood. Here we demonstrate a microbial growth equation relying on an explicit theoretical ground sustained by Boltzmann statistics, thus establishing a relationship between microbial growth rate and available energy. The validity of our equation was then questioned by analyzing the microbial isotopic fractionation phenomenon, which can be viewed as a kinetic consequence of the differences in energy contents of isotopic isomers used for growth. We illustrate how the associated theoretical predictions are actually consistent with recent experimental evidences. Our work links microbial population dynamics to the thermodynamic driving forces of the ecosystem, which opens the door to many biotechnological and ecological developments.
Magnetic iron oxide–fluorescent carbon dots integrated nanoparticles for dual-modal imaging, near-infrared light-responsive drug carrier and photothermal therapy
Authors: Wang Hui , Shen Jing , Li Yingyu , Wei Zengyan , Cao Guixin , Gai Zheng , Hong Kunlun , Banerjee Probal , Zhou Shuiqin
Published: February 2014

The multifunctional hybrid nanoparticles described demonstrate great promise towards advanced nanoplatforms for simultaneous imaging diagnostics and high efficacy therapy.
Zwitteration of dextran: a facile route to integrate antifouling, switchability and optical transparency into natural polymers
Authors: Cao Bin , Li Linlin , Wu Haiyan , Tang Qiong , Sun Bingbing , Dong He , Zhe Jiang , Cheng Gang
Published: February 2014

A facile zwitteration method was developed, using dextran as a model material. This study provides a new avenue for generating multifunctional zwitterionic carboxybetaine materialsin situ.
p-Sulfonic acid calix[n]arenes: the most active and water tolerant organocatalysts in esterification reactions
Authors: Natalino R. , Varejão E. V. V. , da Silva M. J. , Cardoso A. L. , Fernandes S. A.
Published: February 2014

1H NMR experiments showed that p-sulfonic acid calix[n]arenes were more water tolerant and active than monomeric organocatalysts in esterification reactions.
Structural and spectroscopic properties of Yb3+-doped MgAl2O4nanocrystalline spinel
Authors: Wiglusz Rafal J. , Boulon Georges , Guyot Yannick , Guzik Malgorzata , Hreniak Dariusz , Strek Wieslaw
Published: February 2014

Pechini's sol–gel method was successfully applied to obtain an Yb3+-doped MgAl2O4spinel nanopowder. The regularity between the observed structural and spectroscopic measurements was described in detail.
Replacing a stoichiometric silver oxidant with air: ligated Pd(ii)-catalysis to β-aryl carbonyl derivatives with improved chemoselectivity
Authors: Vellakkaran Mari , Andappan Murugaiah M. S. , Kommu Nagaiah
Published: February 2014

Air was employed as a green reoxidant of Pd(0), replacing stoichiometric and toxic silver salt, in the chelation-controlled Pd(ii)-modulated arylative enolization of prop-2-en-1-ols to acquire synthetically-important β-aryl carbonyl derivatives.
A non-diazo strategy to cyclopropanation via oxidatively generated gold carbene: The benefit of a conformationally rigid P,N-bidentate ligand
Authors: Ji Kegong , Zhang Liming
Published: February 2014

By utilizing a conformationally rigid P,N-bidentate ligand, highly efficient intramolecular cyclopropanation reactions using flexible and electronically neutral terminal alkyne substrates are realized.
Adsorption studies of methyl orange on an immobilized Mn-nanoparticle: kinetic and thermodynamic
Authors: Arshadi M. , SalimiVahid F. , Salvacion J. W. L. , Soleymanzadeh M.
Published: February 2014

A nano-adsorbent containing Mn-nanoparticle decorated SiO2–Al2O3 was developed. The application of the nano-adsorbent was studied to remove methyl orange. It effectively removes 98% of methyl orange from contaminated water after 15 min. The novel nano-adsorbent was very stable and easily separated from the purified water.
Mechanism and active site of photocatalytic water splitting on titania in aqueous surroundings
Authors: Zhao Wei-Na , Liu Zhi-Pan
Published: February 2014

Photocatalytic water oxidation is both phase and surface structure-sensitive due to the heat-driven first-step of O–H bond breaking.
Highly diastereoselective hydrosilylations of allylic alcohols
Authors: McLaughlin Mark G. , Cook Matthew J.
Published: February 2014

The highly syn-selective hydrosilylation of allylic alcohols was developed which, following oxidation, provided 1,3 alcohols containing two contiguous stereocentres.
Dynamic combinatorial chemistry with diselenides and disulfides in water
Authors: Rasmussen Brian , Sørensen Anne , Gotfredsen Henrik , Pittelkow Michael
Published: February 2014

Diselenide exchange is introduced as a reversible reaction in dynamic combinatorial chemistry in water at physiological pH.
Highly durable Pt-free fuel cell catalysts prepared by multi-step pyrolysis of Fe phthalocyanine and phenolic resin
Authors: Nabae Yuta , Sonoda Mayu , Yamauchi Chiharu , Hosaka Yo , Isoda Ayano , Aoki Tsutomu
Published: February 2014

A Pt-free cathode catalyst for polymer electrolyte membrane fuel cells has been developed by multi-step pyrolysis of Fe phthalocyanine and phenolic resin and shows a quite promising fuel cell performance.
4,2′:6′,4′′-Terpyridines: diverging and diverse building blocks in coordination polymers and metallomacrocycles
Authors: Housecroft Catherine E.
Published: February 2014

Recent advances in coordination behaviour of 4,2′:6′,4′′-tpy and its 4′-substituted derivatives: chiral polymers, metallohexacycles, packing of extended aryl systems, paddle-wheel and larger cluster nodes leading to predetermined and unexpected architectures.
Reduced memory, low complexity embedded image compression algorithm using hierarchical listless discrete Tchebichef transform
Authors: Senapati Ranjan Kumar , Pati Umesh C. , Mahapatra Kamala Kanta
Published: February 2014

Listless set partitioning embedded block (LSK) and set partitioning embedded block (SPECK) are known for their low complexity and simple implementation. However, the drawback is that these block‐based algorithms encode each insignificant subband by a zero. This generates many zeros at earlier passes because the number of significant coefficients at higher bitplanes is likely to be very few in a transformed image. An improved LSK (ILSK) algorithm that codes a single zero to several insignificant subbands is proposed. This reduces the length of the output bit string, encoding/decoding time and dynamic memory requirement at early passes. Furthermore, ILSK algorithm is coupled with discrete Tchebichef transform (DTT). This gives rise to a novel coder named as hierarchical listless DTT (HLDTT). The proposed HLDTT has desirable attributes like full embeddedness for progressive transmission, precise rate control for constant bit rate traffic and low complexity for low power applications. The performance of HLDTT is assessed using peak‐signal‐to‐noise‐ratio (PSNR) and structural‐similarity‐index‐metric (SSIM). Extensive simulation conducted on various standard test images shows that HLDTT exhibits significant improvement in PSNR values from lower to medium bit rates. At the same time, HLDTT shows improvement in SSIM values on all bit rates.
Analysis of voltage and current stresses of a generalised step‐up DC–DC converter
Authors: Nouri Tohid , Hosseini Seyed Hossein , Babaei Ebrahim
Published: February 2014

A non‐isolated DC–DC converter with high‐voltage gain and low‐voltage stress on switches is proposed in this study. For absorption of energy n stages of diode–capacitor–inductor (D–C–L) units are used at the input that results in higher voltage gains. Actually, the proposed converter generalises the voltage lift circuit and combines it with a voltage multiplier cell. Therefore comparing to structures with one stage of D–C–L unit, it will be feasible to achieve supposed voltage gain at lower duty cycles. Lower values of duty cycle will result in increasing of converter controllability and increasing of operation region. The generalised analysis of the voltage and current stresses of the semiconductors and power components is carried out. The circuit performance will be compared with other solutions that were previously proposed for voltage step‐up in the terms of voltage gain, switch and output diode voltage stress and number of components. The carried mathematical analysis and circuit performance are validated through both simulation and experimental results that match each other reasonably well.
Cramér‐Rao lower bound with Pd < 1 for target localisation accuracy in multistatic passive radar
Authors: Anastasio Valeria , Farina Alfonso , Colone Fabiola , Lombardo Pierfrancesco
Published: February 2014

By exploiting the sources of opportunity not designed for radar applications, the passive radar system often operates with a Pd in the range from 60 to 85% for acceptable false alarm rates. Multistatic radar networks can be used to both increase detection capability and localisation accuracy. The standard Cramér‐Rao lower bound (CRLB) cannot be used for a realistic assessment of the target localisation accuracy in a surveillance area since it provides optimistic predictions. In this study, the authors derive the CRLB with missing observations, namely for Pd < 1, for the multisensory case. The results are illustrated for the case study of a multistatic passive radar exploiting FM radio transmissions where each bistatic pair within the network is assigned with a detection probability for each target position in the surveillance area. The obtained CRLB with Pd < 1 is then employed to compare the localisation performance achievable by a multistatic passive radar when using different sets of measurements: (A) only range measurements, (B) range and Doppler frequency measurements and (C) Doppler frequency measurements only. The reported results show that the proposed CRLB with Pd < 1 yields a more reliable prediction of the achievable performance thus allowing a fair comparison of the above different strategies for target localisation.
Adaptive multiple‐input multiple‐output radar beamforming based on direct data domain approach
Authors: Zhang Wei , Wang Ju , Wu Siliang
Published: February 2014

An adaptive multiple‐input multiple‐output (MIMO) radar beamforming technique based on direct data domain (D3) approach is presented. The proposed method generally outperforms traditional adaptive beamformers in surprise or rapidly changing interference scenarios due to the use of a D3 interference cancellation technique, which utilises a single snapshot for adaptive beamforming. The proposed D3 approach suffers from performance degradation in the presence of uncertainty in the knowledge of target direction. To overcome this problem, a robust D3 approach using worst‐case performance optimisation is developed to achieve robustness against look direction error.
Graphene-based terahertz photodetector by noise thermometry technique
Authors: Wang Ming-Jye , Wang Ji-Wun , Wang Chun-Lun , Chiang Yen-Yu , Chang Hsian-Hong
Published: February 2014

We report the characteristics of graphene-based terahertz (THz) photodetector based on noise thermometry technique by measuring its noise power at frequency from 4 to 6 GHz. Hot electron system in graphene microbridge is generated after THz photon pumping and creates extra noise power. The equivalent noise temperature and electron temperature increase rapidly in low THz pumping regime and saturate gradually in high THz power regime which is attributed to a faster energy relaxation process involved by stronger electron-phonon interaction. Based on this detector, a conversion efficiency around 0.15 from THz power to noise power in 4–6 GHz span has been achieved.
Effect of structural disorder on the magnetocaloric properties of Ni-Mn-Sn alloy
Authors: Ghosh Arup , Mandal Kalyan
Published: February 2014

The magnetic and magnetocaloric properties of Ni50Mn36.5Sn13.5 Heusler alloy has been studied by varying the duration of annealing (0, 6, 12, 18, and 24 h) at 1173 K. The atomic ordering increases, martensitic transition (MT) becomes sharper and exchange bias field increases with increasing annealing time. The sample annealed for 24 h has shown a large magnetic entropy change (ΔSM) near its MT. But, the net refrigerant capacity at the MT of 12 h annealed sample is larger than the former one. We have discussed these results in the context of structural disorder and the ferro/antiferro correlations present in these alloy systems.
Hysteresis reduction by fluorine incorporation into high permittivity tetragonal ZrO2 on Ge
Authors: Chang Hung-Chih , Lin Cheng-Ming , Huang Chih-Hsiung , Liu C. W.
Published: February 2014

Utilizing remote NH3/H2 plasma on GeO2/Ge can achieve the nearly-free interfacial layer and low equivalent oxide thickness of ∼0.4 nm by the formation of tetragonal ZrO2 phase. However, the electrical defects in ZrO2 result in a large C-V hysteresis (∼580 mV). The fluorine incorporation by CF4 plasma is demonstrated to effectively passivate these defects both experimentally and theoretically. The hysteresis is reduced to be ∼200 mV, and the interface defect density, permittivity, and gate leakage current remain intact. The Zr-F bond formation to remove the midgap states calculated by the density-function-theory may be the origin of passivation.
Resistive switching memories in MoS2 nanosphere assemblies
Authors: Xu Xiao-Yong , Yin Zong-You , Xu Chun-Xiang , Dai Jun , Hu Jing-Guo
Published: February 2014

A resistive switching memory device consisting of reduced graphene oxide and indium tin oxide as top/bottom two electrodes, separated by dielectric MoS2 nanosphere assemblies as the active interlayer, was fabricated. This device exhibits the rewritable nonvolatile resistive switching with low SET/RESET voltage (∼2 V), high ON/OFF resistance ratio (∼104), and superior electrical bistability, introducing a potential application in data storage field. The resistance switching mechanism was analyzed in the assumptive model of the electron tunneling across the polarized potential barriers.
Direct measurement of the vortex migration caused by traveling magnetic wave
Authors: Wang Wei , Spaven Fred , Zhang Min , Baghdadi Mehdi , Coombs Timothy
Published: February 2014

We studied the magnetisation of a 2 in. diameter YBCO thin film in the presence of traveling magnetic waves with six hall sensors. Simulation based on finite element method was conducted to reproduce the process of magnetisation. We discovered that the magnetisation of YBCO thin film based on traveling waves does not follow the constant current density assumption as used in the standing wave condition. We have shown that the traveling wave is more efficient in transporting the flux into the YBCO thin film, which suggests the potential of a flux injection device for high temperature superconducting coils.
A proposal for optical terahertz detection with externally biased nanopore superlattices
Authors: Xiao-Li Yinying , O'Brien John
Published: February 2014

We propose and model a terahertz detector based on the transport properties of an excited carrier population in a nanopore structure. The present work supports the proposal with detailed electronic dispersion, optical absorption, and carrier transport.
Ultra-broadband terahertz time-domain ellipsometric spectroscopy utilizing GaP and GaSe emitters and an epitaxial layer transferred photoconductive detector
Authors: Yamashita Masatsugu , Takahashi Hideki , Ouchi Toshihiko , Otani Chiko
Published: February 2014

We present a reflection-type ultra-broadband terahertz (THz) time-domain spectroscopic ellipsometry system covering the frequency range of 0.5–30 THz. GaP (110) and z-cut GaSe crystals are used as emitters to generate the THz and mid-infrared pulses, respectively, and a photoconductive antenna switch using a low-temperature grown GaAs epitaxial layer transferred on Si substrate was used as a detector. By changing the emitter between the GaP and GaSe crystals, the measurable frequency range can be easily switched from the 0.5–7.8 THz range to the 7.8–30 THz range without additional optical alignment. We demonstrated the measurement of the dielectric function in a p-type InAs wafer and the optical conductivity of an indium tin oxide (ITO) thin film. The obtained carrier density and the mobility of the ITO thin film show good agreement with that obtained by the Hall measurement.
Temperature-dependent morphology of hybrid nanoflowers from elastin-like polypeptides
Authors: Ghosh Koushik , Balog Eva Rose M. , Sista Prakash , Williams Darrick J. , Kelly Daniel , Martinez Jennifer S. , Rocha Reginaldo C.
Published: February 2014

We report a method for creating hybrid organic-inorganic “nanoflowers” using calcium or copper ions as the inorganic component and a recombinantly expressed elastin-like polypeptide (ELP) as the organic component. Polypeptides provide binding sites for the dynamic coordination with metal ions, and then such noncovalent complexes become nucleation sites for primary crystals of metal phosphates. We have shown that the interaction between the stimuli-responsive ELP and Ca2+ or Cu2+, in the presence of phosphate, leads to the growth of micrometer-sized particles featuring nanoscale patterns shaped like flower petals. The morphology of these flower-like composite structures is dependent upon the temperature of growth and has been characterized by scanning electron microscopy. The composition of nanoflowers has also been analyzed by energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The temperature-dependent morphologies of these hybrid nanostructures, which arise from the controllable phase transition of ELPs, hold potential for morphological control of biomaterials in emerging applications such as tissue engineering and biocatalysis.
Equilibrium position dependent magnetic vortex dip dynamics under rotating magnetic fields
Authors: Shim Je-Ho , Piao Hong-Guang , Kim Dong-Hyun
Published: February 2014

We have carried out micromagnetic simulations to explore a magnetic vortex dynamics on ferromagnetic nanodisks under clockwise (CW) and counterclockwise (CCW) rotating magnetic fields. Investigation of low excitational vortex core motion without being involved with a core reversal phenomenon has been systematically carried out, where a contrasting core polariziation-selective dynamics, depending on the rotating field sense, is explained based on a core position, a vortex dip structure, and a dynamic equilibrium position, coined as the Zeeman point. In particular, under rotating fields with the opposite rotation sense to the core gyration, a vortex dip structure formation is suppressed due to a shorter distance between the core and the Zeeman point.
Microwave absorptions of ultrathin conductive films and designs of frequency-independent ultrathin absorbers
Authors: Li Sucheng , Anwar Shahzad , Lu Weixin , Hang Zhi Hong , Hou Bo , Shen Mingrong , Wang Chin-Hua
Published: February 2014

We study the absorption properties of ultrathin conductive films in the microwave regime, and find a moderate absorption effect which gives rise to maximal absorbance 50% if the sheet (square) resistance of the film meets an impedance matching condition. The maximal absorption exhibits a frequency-independent feature and takes place on an extremely subwavelength scale, the film thickness. As a realistic instance, ∼5 nm thick Au film is predicted to achieve the optimal absorption. In addition, a methodology based on metallic mesh structure is proposed to design the frequency-independent ultrathin absorbers. We perform a design of such absorbers with 50% absorption, which is verified by numerical simulations.
Energy transport in crystalline DNA composites
Authors: Xu Zaoli , Xu Shen , Tang Xiaoduan , Wang Xinwei
Published: February 2014

This work reports on the synthesis of crystalline DNA-composited films and microfibers, and details the study of thermal energy transport in them. The transient electro-thermal technique is used to characterize the thermal transport in DNA composite microfibers, and the photothermal technique is used to explore the thermal transport in the thickness direction of DNA films. Compared with microfibers, the DNA films are found to have a higher thermal transport capacity, largely due to the carefully controlled crystallization process in film synthesis. In high NaCl concentration solutions, the bond of the Na+ ion and phosphate group aligns the DNA molecules with the NaCl crystal structure during crystallization. This results in significant enhancement of thermal transport in the DNA films with aligned structure.
Interfacial perpendicular magnetic anisotropy in CoFeB/MgO structure with various underlayers
Authors: Oh Young-Wan , Lee Kyeong-Dong , Jeong Jong-Ryul , Park Byong-Guk
Published: February 2014

Interfacial perpendicular magnetic anisotropy (PMA) in CoFeB/MgO structures was investigated and found to be critically relied on underlayer material and annealing temperature. With Ta or Hf underlayer, clear PMA is observed in as-deposited samples while no PMA was shown in those with Pt or Pd. This may be attributed to smaller saturation magnetization of the films with Ta or Hf underlayer, which makes the PMA of CoFeB/MgO interface dominates over demagnetization field. On the contrary, samples with Pt or Pd demonstrate PMA only after annealing, which might be due to the CoPt (or CoPd) alloy formation that enhances PMA.
High performance bilayer-graphene terahertz detectors
Authors: Spirito Davide , Coquillat Dominique , De Bonis Sergio L. , Lombardo Antonio , Bruna Matteo , Ferrari Andrea C. , Pellegrini Vittorio , Tredicucci Alessandro , Knap Wojciech , Vitiello Miriam S.
Published: February 2014

We report bilayer-graphene field effect transistors operating as Terahertz (THz) broadband photodetectors based on plasma-waves excitation. By employing wide-gate geometries or buried gate configurations, we achieve a responsivity ∼1.2 V/W (1.3 mA/W) and a noise equivalent power ∼2 × 10−9 W/√Hz in the 0.29–0.38 THz range, in photovoltage and photocurrent mode. The potential of this technology for scalability to higher frequencies and the development of flexible devices makes our approach competitive for a future generation of THz detection systems.
A multiple mapping conditioning model for differential diffusion
Authors: Dialameh L. , Cleary M. J. , Klimenko A. Y.
Published: February 2014

This work introduces modeling of differential diffusion within the multiple mapping conditioning (MMC) turbulent mixing and combustion framework. The effect of differential diffusion on scalar variance decay is analyzed and, following a number of publications, is found to scale as Re−1/2. The ability to model the differential decay rates is the most important aim of practical differential diffusion models, and here this is achieved in MMC by introducing what is called the side-stepping method. The approach is practical and, as it does not involve an increase in the number of MMC reference variables, economical. In addition we also investigate the modeling of a more refined and difficult to reproduce differential diffusion effect – the loss of correlation between the different scalars. For this we develop an alternative MMC model with two reference variables but which also makes use of the side-stepping method. The new models are successfully validated against DNS results available in literature for homogenous, isotropic two scalar mixing.
Calculation and measurement of a neutral air flow velocity impacting a high voltage capacitor with asymmetrical electrodes
Authors: Malík M. , Primas J. , Kopecký V. , Svoboda M.
Published: February 2014

This paper deals with the effects surrounding phenomenon of a mechanical force generated on a high voltage asymmetrical capacitor (the so called Biefeld-Brown effect). A method to measure this force is described and a formula to calculate its value is also given. Based on this the authors derive a formula characterising the neutral air flow velocity impacting an asymmetrical capacitor connected to high voltage. This air flow under normal circumstances lessens the generated force. In the following part this velocity is measured using Particle Image Velocimetry measuring technique and the results of the theoretically calculated velocity and the experimentally measured value are compared. The authors found a good agreement between the results of both approaches.
A variable-temperature nanostencil compatible with a low-temperature scanning tunneling microscope/atomic force microscope
Authors: Steurer Wolfram , Gross Leo , Schlittler Reto R. , Meyer Gerhard
Published: February 2014

We describe a nanostencil lithography tool capable of operating at variable temperatures down to 30 K. The setup is compatible with a combined low-temperature scanning tunneling microscope/atomic force microscope located within the same ultra-high-vacuum apparatus. The lateral movement capability of the mask allows the patterning of complex structures. To demonstrate operational functionality of the tool and estimate temperature drift and blurring, we fabricated LiF and NaCl nanostructures on Cu(111) at 77 K.
The hydrogen abstraction reaction O(3P) + CH4: A new analytical potential energy surface based on fit toab initiocalculations
Authors: González-Lavado Eloisa , Corchado Jose C. , Espinosa-Garcia Joaquin
Published: February 2014

Based exclusively on high-level ab initio calculations, a new full-dimensional analytical potential energy surface (PES-2014) for the gas-phase reaction of hydrogen abstraction from methane by an oxygen atom is developed. The ab initio information employed in the fit includes properties (equilibrium geometries, relative energies, and vibrational frequencies) of the reactants, products, saddle point, points on the reaction path, and points on the reaction swath, taking especial caution respecting the location and characterization of the intermediate complexes in the entrance and exit channels. By comparing with the reference results we show that the resulting PES-2014 reproduces reasonably well the whole set of ab initio data used in the fitting, obtained at the CCSD(T) = FULL/aug-cc-pVQZ//CCSD(T) = FC/cc-pVTZ single point level, which represents a severe test of the new surface. As a first application, on this analytical surface we perform an extensive dynamics study using quasi-classical trajectory calculations, comparing the results with recent experimental and theoretical data. The excitation function increases with energy (concave-up) reproducing experimental and theoretical information, although our values are somewhat larger. The OH rotovibrational distribution is cold in agreement with experiment. Finally, our results reproduce experimental backward scattering distribution, associated to a rebound mechanism. These results lend confidence to the accuracy of the new surface, which substantially improves the results obtained with our previous surface (PES-2000) for the same system.
Nucleation and growth by diffusion under Ostwald-Freundlich boundary condition
Authors: Iwamatsu Masao
Published: February 2014

The critical radius of a nucleus grown by diffusion in a solution is studied thermodynamically as well as kinetically. The thermodynamic growth equation called Zeldovich equation of classical nucleation theory and the kinetic diffusional growth equation combined with the Ostwald-Freundlich boundary condition lead to the same critical radius. However, it should be pointed out that the diffusional equation may lead to a kinetic critical radius that is different from the thermodynamic critical radius, thus indicating the possibility of kinetically controlling the critical radius of a nucleus.
Scalable stacked array piezoelectric deformable mirror for astronomy and laser processing applications
Authors: Wlodarczyk Krystian L. , Bryce Emma , Schwartz Noah , Strachan Mel , Hutson David , Maier Robert R. J. , Atkinson David , Beard Steven , Baillie Tom , Parr-Burman Phil , Kirk Katherine , Hand Duncan P.
Published: February 2014

A prototype of a scalable and potentially low-cost stacked array piezoelectric deformable mirror (SA-PDM) with 35 active elements is presented in this paper. This prototype is characterized by a 2 μm maximum actuator stroke, a 1.4 μm mirror sag (measured for a 14 mm × 14 mm area of the unpowered SA-PDM), and a ±200 nm hysteresis error. The initial proof of concept experiments described here show that this mirror can be successfully used for shaping a high power laser beam in order to improve laser machining performance. Various beam shapes have been obtained with the SA-PDM and examples of laser machining with the shaped beams are presented.
Nondegenerate parametric generation of 2.2-mJ, few-cycle 2.05-μm pulses using a mixed phase matching scheme
Authors: Xu Guibao , Wandel Scott F. , Jovanovic Igor
Published: February 2014

We describe the production of 2.2-mJ, ∼6 optical-cycle-long mid-infrared laser pulses with a carrier wavelength of 2.05 μm in a two-stage β-BaB2O4 nondegenerate optical parametric amplifier design with a mixed phase matching scheme, which is pumped by a standard Ti:sapphire chirped-pulse amplification system. It is demonstrated that relatively high pulse energies, short pulse durations, high stability, and excellent beam profiles can be obtained using this simple approach, even without the use of optical parametric chirped-pulse amplification.
Boron- and phosphorus-doped silicon germanium alloy nanocrystals—Nonthermal plasma synthesis and gas-phase thin film deposition
Authors: Rowe David J. , Kortshagen Uwe R.
Published: February 2014

Alloyed silicon-germanium (SiGe) nanostructures are the topic of renewed research due to applications in modern optoelectronics and high-temperature thermoelectric materials. However, common techniques for producing nanostructured SiGe focus on bulk processing; therefore little is known of the physical properties of SiGe nanocrystals (NCs) synthesized from molecular precursors. In this letter, we synthesize and deposit thin films of doped SiGe NCs using a single, flow-through nonthermal plasma reactor and inertial impaction. Using x-ray and vibrational analysis, we show that the SiGe NC structure appears truly alloyed for Si1−xGex for 0.16 < x < 0.24, and quantify the atomic dopant incorporation within the SiGe NC films.
Inhibition of beta-amyloid aggregation by fluorescent dye labels
Authors: Amaro Mariana , Wellbrock Thorben , Birch David J. S. , Rolinski Olaf J.
Published: February 2014

The fluorescence decay of beta-amyloid's (Aβ) intrinsic fluorophore tyrosine has been used for sensing the oligomer formation of dye-labelled Aβ monomers and the results compared with previously studied oligomerization of the non-labelled Aβ peptides. It has been demonstrated that two different sized, covalently bound probes 7-diethylaminocoumarin-3-carbonyl and Hilyte Fluor 488 (HLF), alter the rate and character of oligomerization to different extents. The ability of HLF to inhibit formation of highly ordered structures containing beta-sheets was also shown. The implications of our findings for using fluorescence methods in amyloidosis research are discussed and the advantages of this auto-fluorescence approach highlighted.
Excess carrier lifetimes in Ge layers on Si
Authors: Geiger R. , Frigerio J. , Süess M. J. , Chrastina D. , Isella G. , Spolenak R. , Faist J. , Sigg H.
Published: February 2014

The excess charge carrier lifetimes in Ge layers grown on Si or germanium-on-insulator are measured by synchrotron based pump-probe transmission spectroscopy. We observe that the lifetimes do not strongly depend on growth parameters and annealing procedure, but on the doping profile. The defect layer at the Ge/Si interface is found to be the main non-radiative recombination channel. Therefore, the longest lifetimes in Ge/Si (2.6 ns) are achieved in sufficiently thick Ge layers with a built-in field, which repels electrons from the Ge/Si interface. Longer lifetimes (5.3 ns) are obtained in overgrown germanium-on-insulator due to the absence of the defective interface.
Entanglement-assisted electron microscopy based on a flux qubit
Authors: Okamoto Hiroshi , Nagatani Yukinori
Published: February 2014

A notorious problem in high-resolution biological electron microscopy is radiation damage caused by probe electrons. Hence, acquisition of data with minimal number of electrons is of critical importance. Quantum approaches may represent the only way to improve the resolution in this context, but all proposed schemes to date demand delicate control of the electron beam in highly unconventional electron optics. Here we propose a scheme that involves a flux qubit based on a radio-frequency superconducting quantum interference device, inserted in a transmission electron microscope. The scheme significantly improves the prospect of realizing a quantum-enhanced electron microscope for radiation-sensitive specimens.
Chaotic magnetic fields in Vlasov-Maxwell equilibria
Authors: Ghosh Abhijit , Janaki M. S. , Dasgupta Brahmananda , Bandyopadhyay Alak
Published: February 2014

Stationary solutions of Vlasov-Maxwell equations are obtained by exploiting the invariants of single particle motion leading to linear or nonlinear functional relations between current and vector potential. For a specific combination of invariants, it is shown that Vlasov-Maxwell equilibria have an associated Hamiltonian that exhibits chaos.
Diagnostics of fast formation of distributed plasma discharges using X-band microwaves
Authors: Xiang X. , Kupczyk B. , Booske J. , Scharer J.
Published: February 2014

We present measurements of high power (25.7 kW), pulsed (800 ns), X-band (9.382 GHz) microwave breakdown plasmas, including reflected power measurements, mixer reflected amplitude and phase measurements, optical emission spectroscopy (OES) measurements, and an analysis that estimates the average electron density and electron temperature. In addition, a six-region, 1-D model was used to determine plasma parameters and compare with the experimental results. The experimental results show that using a 43 Hz repetition rate with an 800 ns pulse, fast (<300 ns) breakdown occurs in neon measured between 50 Torr and 250 Torr, producing plasma that lasts for over 7 μs. It also leads to large microwave reflections (70%) and an on-axis transmission attenuation of −15 dB. Moreover, a comparison between a 1-D model and mixer measurements shows that at 100 Torr, the neon plasma electron density peaked at 2 × 1012 cm−3, and the electron temperature peaked at 2.5 eV assuming a Maxwellian distribution. The addition of 2% Ar in Ne reduced the breakdown time and allowed OES measurements to determine the effective electron temperature. OES measurements of mixed (Ne/Ar: 98/2) argon line ratios (420.1 nm/419.8 nm) were used to determine the average effective electron temperature Te(eff) = 1.2 eV, averaged over the entire 7μs plasma lifetime. They indicate that the electron energy distribution was not Maxwellian but, instead, tended towards a Druyvesteyn character.
Magnetic interactions in a quasi-one-dimensional antiferromagnet Cu(H2O)2(en)SO4
Authors: Sýkora Rudolf , Legut Dominik
Published: February 2014

A theoretical ab-initio investigation of exchange interaction between Cu atoms in an insulating antiferromagnet Cu(H2O)2(en)SO4, en = C2H8N2, is reported. While the previous experimental studies described the system's magnetism to be quasi-two-dimensional, our results, based on a mapping of the system onto an effective Heisenberg model, rather support a quasi-one-dimensional character with the exchange coupling between the Cu atoms being propagated mainly along a zigzag line lying in the crystal's bc plane and connecting the Cu atoms through the N atoms. Further, the direction of magnetic moments on the Cu atoms is suggested to be nearly along the crystal's a axis. A check of the change in the exchange constants induced either by external pressure or by various values of U in the GGA + U approximation is made. Finally, based on experimental values of positions of broad maxima in magnetic-susceptibility and specific-heat curves and using theoretical expressions available in the literature a relevant value of the U parameter and related expected value of the electronic gap are estimated to be about 5 eV and 2 eV, respectively.
Realization of one-way electromagnetic modes at the interface between two dissimilar metals
Authors: Dixit Mehul , Stroud David
Published: February 2014

We calculate the dispersion relations for electromagnetic waves propagating at the interface between two dissimilar Drude metals in an external magnetic field B parallel to the interface. The propagating modes are bound to the interface and travel perpendicular to B. In certain frequency ranges, the waves can propagate in one direction only. The frequency range for these one-way modes increases with increasing B. One group of modes occurs at moderate frequencies, between the lower and upper plasma frequencies of the two metals. The other occurs at much lower frequencies, between their lower and upper cyclotron frequencies. We discuss possible ways to realize such modes in real materials, including dissimilar superconductors.
Note: Versatile sample stick for neutron scattering experiments in high electric fields
Authors: Bartkowiak M. , White J. S. , Rønnow H. M. , Prša K.
Published: February 2014

We present a versatile high voltage sample stick that fits into all cryomagnets and standard cryostats at the Swiss Spallation Neutron Source, Paul Scherrer Institut, and which provides a low effort route to neutron scattering experiments that combine electric field with low temperature and magnetic field. The stick allows for voltages up to 5 kV and can be easily adapted for different scattering geometries. We discuss the design consideration and thermal behavior of the stick, and give one example to showcase the abilities of the device.
Magnetic and dielectric properties of Aurivillius phase Bi6Fe2Ti3−2xNbxCoxO18 (0 ≤ x ≤ 0.4)
Authors: Yuan B. , Yang J. , Chen J. , Zuo X. Z. , Yin L. H. , Tang X. W. , Zhu X. B. , Dai J. M. , Song W. H. , Sun Y. P.
Published: February 2014

We investigate the structural, magnetic, and dielectric properties of Bi6Fe2Ti3−2xNbxCoxO18 (0 ≤ x ≤ 0.4). The room-temperature ferromagnetism is observed in the Nb and Co co-doped samples compared with the paramagnetic behavior in Bi6Fe2Ti3O18. The ferromagnetism in Bi6Fe2Ti3−2xNbxCoxO18 can be understood in terms of spin canting of the antiferromagnetic coupling of the Fe-based and Co-based sublattices via Dzyaloshinsky-Moriya interaction. Moreover, doping Co at Ti sites can significantly enhance the ferromagnetic Curie temperature compared with the substitution of Co for Fe in the Aurivillius compounds. The dielectric loss of Bi6Fe2Ti3−2xNbxCoxO18 (0.1 ≤ x ≤ 0.4) exhibits a relaxation process. The rather large activation energy in the 0.1 ≤ x ≤ 0.3 samples implies that the relaxation process is not due to the thermal motion of oxygen vacancies inside ceramics.
Non-equilibrium deposition of phase pure Cu2O thin films at reduced growth temperature
Authors: Subramaniyan Archana , Perkins John D. , O’Hayre Ryan P. , Lany Stephan , Stevanovic Vladan , Ginley David S. , Zakutayev Andriy
Published: February 2014

Cuprous oxide (Cu2O) is actively studied as a prototypical material for energy conversion and electronic applications. Here we reduce the growth temperature of phase pure Cu2O thin films to 300 °C by intentionally controlling solely the kinetic parameter (total chamber pressure, Ptot) at fixed thermodynamic condition (0.25 mTorr pO2). A strong non-monotonic effect of Ptot on Cu-O phase formation is found using high-throughput combinatorial-pulsed laser deposition. This discovery creates new opportunities for the growth of Cu2O devices with low thermal budget and illustrates the importance of kinetic effects for the synthesis of metastable materials with useful properties.
Non-Kondo zero-bias anomaly in disordered quantum wires
Authors: Wen Chong-Shian , Hsiao J. H. , Chen Jeng-Chung
Published: February 2014

We investigated the behavior of the zero-bias anomaly in quantum wires that were embedded with impurities. The linear conductance G can exhibit cusp features that evolve with the positions of the impurities, and these features can be continuously changed using a combination of spit-gate and top-gate voltages. ZBA is observed regardless of the presence of impurity. Kondo model is inadequate for describing the behaviors of both G and ZBA. Despite the presence of impurity scattering, various ZBA behaviors that resemble those reported in clean quantum wires can be observed. Our results suggest that ZBA is an intrinsic phenomenon in a quantum wire, and its temperature and magnetic field dependence does not pertain to the Kondo correlations in quantum dot.
Above room-temperature ferromagnetism of Mn delta-doped GaN nanorods
Authors: Lin Y. T. , Wadekar P. V. , Kao H. S. , Chen T. H. , Huang H. C. , Ho N. J. , Chen Q. Y. , Tu L. W.
Published: February 2014

One-dimensional nitride based diluted magnetic semiconductors were grown by plasma-assisted molecular beam epitaxy. Delta-doping technique was adopted to dope GaN nanorods with Mn. The structural and magnetic properties were investigated. The GaMnN nanorods with a single crystalline structure and with Ga sites substituted by Mn atoms were verified by high-resolution x-ray diffraction and Raman scattering, respectively. Secondary phases were not observed by high-resolution x-ray diffraction and high-resolution transmission electron microscopy. In addition, the magnetic hysteresis curves show that the Mn delta-doped GaN nanorods are ferromagnetic above room temperature. The magnetization with magnetic field perpendicular to GaN c-axis saturates easier than the one with field parallel to GaN c-axis.
Rarefactive and compressive soliton waves in unmagnetized dusty plasma with non-thermal electron and ion distribution
Authors: Eslami Esmaeil , Baraz Rasoul
Published: February 2014

Sagdeev's pseudo potential method is employed to study dust acoustic solitary waves in an unmagnetized plasma containing negatively charged dusts with non-thermal electron and ion. The range of parameters for the existence of solitary waves using the analytical expression of the Sagdeev potential has been found. It is observed that, depending on the values of the plasma parameters like ion to electron temperature ratio σ, non-thermal parameters β and γ, electron to ion density ratio μ, and the value of the Mach number M, both rarefactive and compressive solitary waves may exist.
A unified theory of quasibound states
Authors: Moyer Curt A.
Published: February 2014

We report a formalism for the study of quasibound states, defined here broadly as those states having a connectedness to true bound states through the variation of some physical parameter. The theory admits quasibound states with real energies (stationary quasibound states) and quantum resonances within the same framework, and makes a clean distinction between these states and those of the associated continuum. The approach taken here builds on our earlier work by clarifying several crucial points and extending the formalism to encompass a variety of continuous spectra, including those with degeneracies. The theory is illustrated by examining several cases pertinent to applications widely discussed in the literature. The related issue of observing stationary quasibound states also is addressed. We argue that the Adiabatic Theorem of quantum mechanics not only establishes the criteria necessary for their detection, but also engenders a method for assigning to them a level width that is sufficiently distinct from that of quantum resonances so as to allow the two to be differentiated experimentally.
Measuring Community Completeness: Jobs—Housing Balance, Accessibility, and Convenient Local Access to Nonwork Destinations
Authors: Merlin Louis A
Published: February 2014

Using 2007 travel-diary data from metropolitan Chicago, I investigate what aspects of urban form contribute most to community completeness, as defined by internal tour capture for nonwork tours. I examine two distinct geographic scales: census-defined ‘places’, and synthetically constructed ‘centered communities’. Centered communities are defined as nonwork travel sheds centered upon well-defined concentrations of activity. Higher accessibility share (a new urban form measure defined in the paper) and higher mixed use both significantly predict greater community completeness, as do higher levels of residential or employment density. Furthermore, I find that mixed-use measures describe something other than simple proximity to job-based attractions; these measures also address the appropriate balance of activities necessary for a complete community. To build more-complete communities, planners need to ensure that local accessibility to a variety of destinations of interest is high relative to the regional accessibility to these same types of destinations outside the community.
Bilateral Symmetry and Perceptual Reversals
Authors: Deręgowski Jan B
Published: February 2014

Imposition of patterns varying in symmetry about the observer's median plane on a reversible figure affects duration for which each of the fluctuating percepts is experienced. Symmetry of the imposed patterns is associated with lesser difference between the two durations. This effect is particularly pronounced when the patterns are enantiomorphic and therefore jointly form a symmetrical pattern, but is also present when the patterns are symmetrical but unrelated.