bluuebunny/crossref_metadata_2025 huggingface dataset:
On the origin of fluorescence emission in optically non-linear DCNP crystals
Authors: Morawski O. , Sobolewski A. L. , Kozankiewicz B. , Sznitko L. , Miniewicz A.
Published: October 2014

In optically nonlinear DCNP single crystals, fluorescence originates from structural traps, which was evidenced by kinetic measurements at 5 K.
The identification and characterization of defect states in hybrid organic–inorganic perovskite photovoltaics
Authors: Duan Hsin-Sheng , Zhou Huanping , Chen Qi , Sun Pengyu , Luo Song , Song Tze-Bin , Bob Brion , Yang Yang
Published: October 2014

Thin film photovoltaic cells based on hybrid halide perovskite absorbers have emerged as promising candidates for next generation photovoltaics.
In situ characterization of Cu–Co oxides for catalytic application
Authors: Tian Z. Y. , Vieker H. , Kouotou P. Mountapmbeme , Beyer A.
Published: October 2014

In situ emission and absorption FTIR methods were employed to characterize the spatially resolved structure of binary Co–Cu oxides for low-temperature oxidation of CO and propene. Co–Cu oxide catalysts were controllably synthesized by pulsed-spray evaporation chemical vapor deposition. XRD, FTIR, XPS, UV-vis and helium ion microscopy (HIM) were employed to characterize the as-prepared thin films in terms of structure, composition, optical and thermal properties as well as morphology. In situ emission FTIR spectroscopy indicates that Co3O4, CuCo2O4 and CuO are thermally stable at 650, 655 and 450 °C, respectively. The catalytic tests with absorption FTIR display that the involvement of Co–Cu oxides can initiate CO and C3H6 oxidation at lower temperatures. The results indicate that in situ emission and absorption FTIR are useful techniques to explore the thermal properties and catalytic performance of functional materials, allowing many potential applications in tailoring their temporally and spatially resolved structure-property relationships.
Preparation of carbon-coated lithium iron phosphate/titanium nitride for a lithium-ion supercapacitor
Authors: Xie Yibing , Song Fei , Xia Chi , Du Hongxiu
Published: October 2014

Carbon-coated lithium iron phosphate supported on a titanium nitride nanowire network was designed as the electrode material for a lithium-ion supercapacitor.
Neck Pain following Laminoplasty
Authors: Mesfin Addisu , Park Moon-Soo , Piyaskulkaew Chaiwat , Chuntarapas Tapanut , Song Kwang Sup , Kim Han Jo , Riew K. Daniel
Published: October 2014

Study Design

Retrospective evaluation of prospectively collected data.

Objective

To compare preoperative and postoperative neck pain following laminoplasty using the Neck Disability Index (NDI).

Methods

Seventy-two patients undergoing laminoplasty from 2006 to 2009 at a single institution were identified. Thirty-four patients with a minimum 1-year follow-up who completed preoperative, 6-week, and 1-year postoperative NDI questionnaires were enrolled. Demographic data and surgical data including estimated blood loss (EBL), length of surgery, number of laminoplasty levels, complications, and length of hospitalization were collected.

Results

Mean age was 62 years (range: 34 to 88), mean follow-up was 17 months (range: 12 to 31), and there were 21 men and 13 women. Diagnoses were cervical spondylotic myelopathy ( n = 26), ossification of the posterior longitudinal ligament ( n = 6), and central cord syndrome ( n = 2). Mean EBL was 120 mL (range: 50 to 200), and mean surgical time was 152 minutes (range: 70 to 240). Average number of laminoplasty levels was 3 (range: 1 to 5). The open door technique was used, and 24/34 (71%) did not have laminoplasty at C3 and C7. No intraoperative complications were noted, and average hospital stay was 1.6 days (range: 1 to 7). Significant improvement in NDI total score was noted at 1 year ( p < 0.002) and in NDI pain score at 6 weeks ( p < 0.028) and 1 year ( p < 0.007) postoperatively.

Conclusions

Patients having laminoplasty experienced significant improvement in NDI pain subscore and NDI total scores at a minimum of 1 year postoperatively.
Bone Scans Are Reliable for the Identification of Lumbar Disk and Facet Pathology
Authors: Malham Gregory M. , Parker Rhiannon M. , Ballok Zita E. , Goss Ben , Diwan Ashish D. , Uribe Juan S.
Published: October 2014

Study Design

Surgeon survey.

Objective

To evaluate the reliability of bone single-photon emission computed tomography (SPECT) versus bone SPECT images co-registered with computed tomography (bone SPECT-CT) by analyzing interobserver agreement for identification of the anatomical location of technetium99m-labeled oxidronate uptake in the lumbar disk and/or facet joint.

Methods

Seven spine surgeons interpreted 20 bone scans: 10 conventional black-and-white tomograms (bone SPECT) and 10 color-graded bone SPECT-CT scans. Each surgeon was asked to identify the location of any diagnostically relevant uptake in the disk and/or facet joint between L1 and S1. Reliability was evaluated using the free-marginal kappa statistic, and the level of agreement was assessed using the Landis and Koch interpretation.

Results

Conventional bone SPECT scans and bone SPECT-CT scans were reliable for the identification of diagnostically relevant uptake, with bone SPECT-CT having higher reliability (kappa = 0.72) than bone SPECT alone (0.59). Bone SPECT and bone SPECT-CT were also reliable in identifying disk pathology, with kappa values of 0.72 and 0.81, respectively. However, bone SPECT-CT was more reliable (0.81) than bone SPECT (0.60) when identifying facet disease.

Conclusions

For the identification of disk pathology, it is reasonable to use either conventional bone SPECT or bone SPECT-CT; however, bone SPECT-CT is more reliable for facet joint pathology.
First Confirmed Metastatic Adamantinoma of the Spine: Case Report and Literature Review
Authors: Morales Ciancio Ruben A. , Gasbarrini Alessandro , Boriani Stefano , Gambarotti Marco
Published: October 2014

Study Design

Case report and literature review.

Objective

To present the first case of metastatic adamantinoma of the spine with immunohistochemical confirmation and an updated literature review.

Summary of Background Data

Spinal metastatic disease could be difficult to diagnose because of the multiple differential diagnoses involved. Spinal surgeons must be aware of unusual primary extra-axial tumors that metastasize to the spine because in certain cases the primary surgery must determine the prognosis of this lesion.

Methods

We present a fully documented case of a middle-aged man with tibial adamantinoma who developed spine metastasis, confirmed by immunohistochemistry. A literature review was done.

Results

Based on clinical, imaging, and pathology findings, we provide evidence for the first proven metastatic adamantinoma of the spine, adding this condition to the long list of differential diagnoses of secondary spinal disease.

Conclusions

Adamantinoma is a very rare bone tumor representing ∼1% of primary bone tumors. Spinal metastatic adamantinoma with immunohistochemical confirmation has not been described previously. Due to the lack of specific image findings or serum markers and multiple differential diagnoses, biopsy with immunohistochemical confirmation is mandatory, because “en block resection” might prove to be curative treatment.
Observation of spin-charge conversion in chemical-vapor-deposition-grown single-layer graphene
Authors: Ohshima Ryo , Sakai Atsushi , Ando Yuichiro , Shinjo Teruya , Kawahara Kenji , Ago Hiroki , Shiraishi Masashi
Published: October 2014

Conversion of pure spin current to charge current in single-layer graphene (SLG) is investigated by using spin pumping. Large-area SLG grown by chemical vapor deposition is used for the conversion. Efficient spin accumulation in SLG by spin pumping enables observing an electromotive force produced by the inverse spin Hall effect (ISHE) of SLG. The spin Hall angle of SLG is estimated to be 6.1 × 10−7. The observed ISHE in SLG is ascribed to its non-negligible spin-orbit interaction in SLG.
Perturbative treatment of spin-orbit coupling within spin-free exact two-component theory
Authors: Cheng Lan , Gauss Jürgen
Published: October 2014

This work deals with the perturbative treatment of spin-orbit-coupling (SOC) effects within the spin-free exact two-component theory in its one-electron variant (SFX2C-1e). We investigate two schemes for constructing the SFX2C-1e SOC matrix: the SFX2C-1e+SOC [der] scheme defines the SOC matrix elements based on SFX2C-1e analytic-derivative theory, hereby treating the SOC integrals as the perturbation; the SFX2C-1e+SOC [fd] scheme takes the difference between the X2C-1e and SFX2C-1e Hamiltonian matrices as the SOC perturbation. Furthermore, a mean-field approach in the SFX2C-1e framework is formulated and implemented to efficiently include two-electron SOC effects. Systematic approximations to the two-electron SOC integrals are also proposed and carefully assessed. Based on benchmark calculations of the second-order SOC corrections to the energies and electrical properties for a set of diatomic molecules, we show that the SFX2C-1e+SOC [der] scheme performs very well in the computation of perturbative SOC corrections and that the “2eSL” scheme, which neglects the (SS|SS)-type two-electron SOC integrals, is both efficient and accurate. In contrast, the SFX2C-1e+SOC [fd] scheme turns out to be incompatible with a perturbative treatment of SOC effects. Finally, as a first chemical application, we report high-accuracy calculations of the 201Hg quadrupole-coupling parameters of the recently characterized ethylmercury hydride (HHgCH2CH3) molecule based on SFX2C-1e coupled-cluster calculations augmented with second-order SOC corrections obtained at the Hartree-Fock level using the SFX2C-1e+SOC [der]/2eSL scheme.
Fully quantum state-resolved inelastic scattering of NO(X) + Kr: Differential cross sections and product rotational alignment
Authors: Brouard M. , Chadwick H. , Gordon S. D. S. , Hornung B. , Nichols B. , Kłos J. , Aoiz F. J. , Stolte S.
Published: October 2014

Fully quantum state selected and resolved inelastic scattering of NO(X) by krypton has been investigated. Initial Λ-doublet state selection is achieved using an inhomogeneous hexapole electric field. Differential cross sections and even-moment polarization dependent differential cross sections have been obtained at a collision energy of 514 cm−1 for both spin-orbit and parity conserving and changing collisions. Experimental results are compared with those obtained from quantum scattering calculations and are shown to be in very good agreement. Hard shell quantum scattering calculations are also performed to determine the effects of the different parts of the potential on the scattering dynamics. Comparisons are also made with the NO(X) + Ar system.
Time-resolved characterization and energy balance analysis of implosion core in shock-ignition experiments at OMEGA
Authors: Florido R. , Mancini R. C. , Nagayama T. , Tommasini R. , Delettrez J. A. , Regan S. P.
Published: October 2014

Time-resolved temperature and density conditions in the core of shock-ignition implosions have been determined for the first time. The diagnostic method relies on the observation, with a streaked crystal spectrometer, of the signature of an Ar tracer added to the deuterium gas fill. The data analysis confirms the importance of the shell attenuation effect previously noted on time-integrated spectroscopic measurements of thick-wall targets [R. Florido et al., Phys. Rev. E 83, 066408 (2011)]. This effect must be taken into account in order to obtain reliable results. The extracted temperature and density time-histories are representative of the state of the core during the implosion deceleration and burning phases. As a consequence of the ignitor shock launched by the sharp intensity spike at the end of the laser pulse, observed average core electron temperature and mass density reach T ∼ 1100 eV and ρ ∼ 2 g/cm3; then temperature drops to T ∼ 920 eV while density rises to ρ ∼ 3.4 g/cm3 about the time of peak compression. Compared to 1D hydrodynamic simulations, the experiment shows similar maximum temperatures and smaller densities. Simulations do not reproduce all observations. Differences are noted in the heating dynamics driven by the ignitor shock and the optical depth time-history of the compressed shell. Time-histories of core conditions extracted from spectroscopy show that the implosion can be interpreted as a two-stage polytropic process. Furthermore, an energy balance analysis of implosion core suggests an increase in total energy greater than what 1D hydrodynamic simulations predict. This new methodology can be implemented in other ICF experiments to look into implosion dynamics and help to understand the underlying physics.
Fluorescence spectroscopy of UV-MALDI matrices and implications of ionization mechanisms
Authors: Lin Hou-Yu , Hsu Hsu Chen , Lu I-Chung , Hsu Kuo-Tung , Liao Chih-Yu , Lee Yin-Yu , Tseng Chien-Ming , Lee Yuan-Tseh , Ni Chi-Kung
Published: October 2014

Matrix-assisted laser desorption ionization (MALDI) has been widely used in the mass analysis of biomolecules; however, there are a lot of debates about the ionization mechanisms. Previous studies have indicated that S1-S1 annihilation might be a key process in the generation of primary ions. This study investigates S1-S1 annihilation by examining the time-resolved fluorescence spectra of 12 matrices. No S1-S1 annihilation was observed in six of these matrices (3-hydroxy-picolinic acid, 6-aza-2-thiothymine, 2,4-dihydroxy-acetophenone, 2,6-dihydroxy-acetophenone, 2,4,6-trihydroxy-acetophenone, and ferulic acid). We observed two matrix molecules reacting in an electronically excited state (S1) in five of these matrices (2,5-dihydroxybenzoic acid, α-cyano-4-hydroxycinnamic acid, 2,5-dihydroxy-acetophenone, 2,3-dihydroxybenzoic acid, and 2,6-dihydroxybenzoic acid), and S1-S1 annihilation was a possible reaction. Among these five matrices, no S1-S1 annihilation was observed for 2,3-dihydroxybenzoic acid in typical peak power region of nanosecond laser pulses in MALDI, but a very small value of reaction rate constant was observed only in the high peak power region. The excited-state lifetime of sinapinic acid was too short to determine whether the molecules reacted in an electronically excited state. No correlation was observed between the ion generation efficiency of MALDI and S1-S1 annihilation. The results indicate that the proposal of S1-S1 annihilation is unnecessary in MALDI and energy pooling model for MALDI ionization mechanism has to be modified.
Core-to-valence spectroscopic detection of the CH2Br radical and element-specific femtosecond photodissociation dynamics of CH2IBr
Authors: Attar Andrew R. , Piticco Lorena , Leone Stephen R.
Published: October 2014

Element-specific single photon photodissociation dynamics of CH2IBr and core-to-valence absorption spectroscopy of CH2Br radicals are investigated using femtosecond high-harmonic extreme ultraviolet (XUV) transient absorption spectroscopy. Photodissociation of CH2IBr along both the C–I or C–Br reaction coordinates is observed in real-time following excitation at 266 nm. At this wavelength, C–I dissociation is the dominant reaction channel and C–Br dissociation is observed as a minor pathway. Both photodissociation pathways are probed simultaneously through individual 4d(I) N4/5 and 3d(Br) M4/5 core-to-valence transitions. The 3d(Br) M4/5 pre-edge absorption spectrum of the CH2Br radical photoproduct corresponding to the C–I dissociation channel is characterized for the first time. Although the radical's singly occupied molecular orbital (SOMO) is mostly localized on the central carbon atom, the 3d(Br) → π*(SOMO) resonances at 68.5 eV and 69.5 eV are detected 2 eV below the parent molecule 3d(Br) → σ*(LUMO) transitions. Core-to-valence XUV absorption spectroscopy provides a unique probe of the local electronic structure of the radical species in reference to the Br reporter atom. The measured times for C–I dissociation leading to I and I* atomic products are 48 ± 12 fs and 44 ± 4 fs, respectively, while the measured C–Br dissociation time leading to atomic Br is 114 ± 17 fs. The investigation performed here demonstrates the capability of femtosecond time-resolved core-level spectroscopy utilizing multiple reporter atoms simultaneously.
Experimental study of particle formation by ion–ion recombination
Authors: Nagato Kenkichi , Nakauchi Masataka
Published: October 2014

Particle formation by ion–ion recombination has been studied using an ion–ion recombination drift tube (IIR-DT). IIR-DT uses two DC corona ionizers to produce positive and negative ions at the ends of the drift tube. The ions of different polarity move in opposite directions along the electric field in the drift tube. We observed significant particle formation using ions generated in purified air containing H2O, SO2, and NH3. Particle formation was suppressed when no drift field was applied. We also observed few particles when we used a single discharge (positive or negative only). These results clearly show that particle formation observed in the IIR-DT was caused by nucleation by ion–ion recombination. Positive and negative ion species produced by corona ionizers were investigated using an atmospheric pressure ionization mass spectrometer. The ions involved in the particle formation were suggested to include H3O+(H2O)n and NH4+(H2O)n for positive ions and sulfur-based ions such as SO5−, SO5−NO2, and HSO4− for negative ions.
Experimental and ab initio studies of the reactive processes in gas phase i-C3H7Br and i-C3H7OH collisions with potassium ions
Authors: López E. , Lucas J. M. , de Andrés J. , Albertí M. , Bofill J. M. , Bassi D. , Aguilar A.
Published: October 2014

Collisions between potassium ions and neutral i-C3H7Br and i-C3H7OH, all in their electronic ground state, have been studied in the 0.10–10.00 eV center of mass (CM) collision energy range, using the radiofrequency-guided ion beam technique. In K+ + i-C3H7Br collisions KHBr+ formation was observed and quantified, while the analogous KH2O+ formation in K+ + i-C3H7OH was hardly detected. Moreover, formation of the ion-molecule adducts and their decomposition leading to C3H7+ and either KBr or KOH, respectively, have been observed. For all these processes, absolute cross-sections were measured as a function of the CM collision energy. Ab initio structure calculations at the MP2 level have given information about the potential energy surfaces (PESs) involved. In these, different stationary points have been characterized using the reaction coordinate method, their connectivity being ensured by using the intrinsic-reaction-coordinate method. From the measured excitation function for KHBr+ formation the corresponding thermal rate constant at 303 K has been calculated. The topology of the calculated PESs allows an interpretation of the main features of the reaction dynamics of both systems, and in particular evidence the important role played by the potential energy wells in controlling the reactivity for the different reaction channels.
Rotational spectra of propargyl alcohol dimer: A dimer bound with three different types of hydrogen bonds
Authors: Mani Devendra , Arunan E.
Published: October 2014

Pure rotational spectra of the propargyl alcohol dimer and its three deuterium isotopologues have been observed in the 4 to 13 GHz range using a pulsed-nozzle Fourier transform microwave spectrometer. For the parent dimer, a total of 51 transitions could be observed and fitted within experimental uncertainty. For two mono-substituted and one bi-substituted deuterium isotopologues, a total of 14, 17, and 19 transitions were observed, respectively. The observed rotational constants for the parent dimer [A = 2321.8335(4) MHz, B = 1150.4774(2) MHz, and C = 1124.8898(2) MHz] are close to those of the most stable structure predicted by ab initio calculations. Spectra of the three deuterated isotopologues and Kraitchman analysis positively confirm this structure. Geometrical parameters and “Atoms in Molecules” analysis on the observed structure reveal that the two propargyl alcohol units in the dimer are bound by three different types of hydrogen bonds: O–H⋯O, O–H⋯π, and C–H⋯π. To the best of our knowledge, propargyl alcohol seems to be the smallest molecule forming a homodimer with three different points of contact.
Direct observation and mechanism for enhanced field emission sites in platinum ion implanted/post-annealed ultrananocrystalline diamond films
Authors: Panda Kalpataru , Sankaran Kamatchi J. , Inami Eiichi , Sugimoto Yoshiaki , Tai Nyan Hwa , Lin I-Nan
Published: October 2014

Enhanced electron field emission (EFE) properties for ultrananocrystalline diamond (UNCD) films upon platinum (Pt) ion implantation and subsequent post-annealing processes is reported, viz., low turn-on field of 4.17 V/μm with high EFE current density of 5.08 mA/cm2 at an applied field of 7.0 V/μm. Current imaging tunneling spectroscopy (CITS) mode in scanning tunneling spectroscopy directly revealed the increased electron emission sites density for Pt ion implanted/post-annealed UNCD films than the pristine one. The high resolution CITS mapping and local current–voltage characteristic curves demonstrated that the electrons are dominantly emitted from the diamond grain boundaries and Pt nanoparticles.
Tunability over three frequency bands induced by mode transition in relativistic backward wave oscillator with strong end reflections
Authors: Wu Ping , Fan Juping , Teng Yan , Shi Yanchao , Deng Yuqun , Sun Jun
Published: October 2014

This paper presents an efficient approach to realizing the frequency tunability of a relativistic backward wave oscillator (RBWO) over three frequency bands by mode transition without changing the slow wave structure (SWS). It is figured out that the transition of the operation mode in the RBWO can be efficiently achieved by using the strong end reflection of the SWS. This mode transition results in the tunability of the RBWO over three frequency bands at high power and high efficiency without changing the SWS. In numerical simulation, the output frequency of the RBWO can jump over 7.9 GHz in C-band, 9.9 GHz in X-band, and 12.4 GHz in Ku-band with output power exceeding 3.0 GW and conversion efficiency higher than 35% by just reasonably transforming the structures of the front and post resonant reflectors which provide the strong end reflection for the SWS.
Etalon-induced baseline drift and correction in atom flux sensors based on atomic absorption spectroscopy
Authors: Du Yingge , Chambers Scott A.
Published: October 2014

Atom flux sensors based on atomic absorption (AA) spectroscopy are of significant interest in thin film growth as they can provide unobtrusive, element specific real-time flux sensing and control. The ultimate sensitivity and performance of these sensors are strongly affected by baseline drift. Here we demonstrate that an etalon effect resulting from temperature changes in optical viewport housings is a major source of signal instability, which has not been previously considered, and cannot be corrected using existing methods. We show that small temperature variations in the fused silica viewports can introduce intensity modulations of up to 1.5% which in turn significantly deteriorate AA sensor performance. This undesirable effect can be at least partially eliminated by reducing the size of the beam and tilting the incident light beam off the viewport normal.
Hierarchical cobalt-formate framework series with (412⋅63)(49⋅66)n (n = 1–3) topologies exhibiting slow dielectric relaxation and weak ferromagnetism
Authors: Shang Ran , Chen Sa , Hu Ke-Li , Jiang Ze-Chun , Wang Bing-Wu , Kurmoo Mohamedally , Wang Zhe-Ming , Gao Song
Published: October 2014

The employment of linear di-, tri-, and tetra-ammoniums has generated a hierarchy in the binodal (412⋅63)(49⋅66)n topologies with n = 1, 2, and 3, respectively, for the cobalt formate frameworks with increasing length of the cavities to match the ammoniums. This indicates the length-directing effect of the polyammoniums. The dynamic movements of polyammoniums between favored sites or orientations within the cavities lead to slow dielectric relaxations. All materials are spin-canted antiferromagnets in low temperatures and show reduced spontaneous magnetizations from di- and tri-, to tetra-ammoniums, because of the increased number of unique Co ions or the antiferromagnetically coupled sublattices.
High-throughput beamline for attosecond pulses based on toroidal mirrors with microfocusing capabilities
Authors: Frassetto F. , Trabattoni A. , Anumula S. , Sansone G. , Calegari F. , Nisoli M. , Poletto L.
Published: October 2014

We have developed a novel attosecond beamline designed for attosecond-pump/attosecond probe experiments. Microfocusing of the Extreme-ultraviolet (XUV) radiation is obtained by using a coma-compensated optical configuration based on the use of three toroidal mirrors controlled by a genetic algorithm. Trains of attosecond pulses are generated with a measured peak intensity of about 3 × 1011 W/cm2.
Spatiotemporal synchronization of drift waves in a magnetron sputtering plasma
Authors: Martines E. , Zuin M. , Cavazzana R. , Adámek J. , Antoni V. , Serianni G. , Spolaore M. , Vianello N.
Published: October 2014

A feedforward scheme is applied for drift waves control in a magnetized magnetron sputtering plasma. A system of driven electrodes collecting electron current in a limited region of the explored plasma is used to interact with unstable drift waves. Drift waves actually appear as electrostatic modes characterized by discrete wavelengths of the order of few centimeters and frequencies of about 100 kHz. The effect of external quasi-periodic, both in time and space, travelling perturbations is studied. Particular emphasis is given to the role played by the phase relation between the natural and the imposed fluctuations. It is observed that it is possible by means of localized electrodes, collecting currents which are negligible with respect to those flowing in the plasma, to transfer energy to one single mode and to reduce that associated to the others. Due to the weakness of the external action, only partial control has been achieved.
Understanding pop-ins in spherical nanoindentation
Authors: Pathak Siddhartha , Riesterer Jessica L. , Kalidindi Surya R. , Michler Johann
Published: October 2014

Pop-ins, or sudden displacement-bursts at constant load in a nanoindentation test, are typically attributed to the difficulty of setting up potent dislocation sources in the very small indentation zones in these experiments. Such displacement (and strain) bursts would intuitively indicate a sharp drop in stress during the pop-in event itself. However, spherical indentation stress-strain curves routinely exhibit a high and stable indentation stress value during the pop-in, and the indentation stresses decrease only after a further finite amount of additional indentation displacement has been applied. In order to understand this discrepancy, we utilize a combination of interrupted spherical indentation tests along with depth profiling of the residual indentation surfaces using in-situ atomic force microscopy (AFM) to study pop-ins. The AFM surface profile maps show that there is an asymmetric profile change over a limited region around the indentation contact area for a single pop-in; the asymmetry disappears upon further loading beyond the pop-in. A plausible sequence of physical processes (related to metal plasticity) occurring underneath the indenter during and immediately after the occurrence of the pop-in is proposed to explain these observations.
Vibrational coherences in charge-transfer dyes: A non-adiabatic picture
Authors: Sissa Cristina , Delchiaro Francesca , Di Maiolo Francesco , Terenziani Francesca , Painelli Anna
Published: October 2014

Essential-state models efficiently describe linear and nonlinear spectral properties of different families of charge-transfer chromophores. Here, the essential-state machinery is applied to the calculation of the early-stage dynamics after ultrafast (coherent) excitation of polar and quadrupolar chromophores. The fully non-adiabatic treatment of coupled electronic and vibrational motion allows for a reliable description of the dynamics of these intriguing systems. In particular, the proposed approach is reliable even when the adiabatic and harmonic approximations do not apply, such as for quadrupolar dyes that show a multistable, broken-symmetry excited state. Our approach quite naturally leads to a clear picture for a dynamical Jahn-Teller effect in these systems. The recovery of symmetry due to dynamical effects is however disrupted in polar solvents where a static symmetry lowering is observed. More generally, thermal disorder in polar solvents is responsible for dephasing phenomena, damping the coherent oscillations with particularly important effects in the case of polar dyes.
Transverse vibration analysis of single-layered graphene sheet under magneto-thermal environment based on nonlocal plate theory
Authors: Mandal U. , Pradhan S. C.
Published: October 2014

In the present paper, the effect of magneto-thermal environment on the transverse vibration of magnetically sensitive single-layered graphene sheets (SLGS) has been analyzed based on nonlocal plate theory. Governing differential equations for the analysis of vibration characteristics of SLGS under magneto-thermal environment are derived considering the Lorentz magnetic force obtained from Maxwell's relationship and thermal elasticity. The governing differential equations are solved employing differential quadrature method. Convergence and validation study are performed. Moreover, the influences of SLGS geometrical properties, nonlocal parameter, in-plane magnetic field and environmental temperature change on the vibration characteristics of SLGS are studied and reported.
Optical properties of single crystal Bi4Ge3O12 from the infrared to ultraviolet
Authors: Haneef Hamna F. , Podraza Nikolas J.
Published: October 2014

Optical properties in the form of the complex dielectric function spectra (ε = ε1 + iε2) of commercially produced single crystal bismuth germanate (Bi4Ge3O12) have been studied using spectroscopic ellipsometry from 0.033 to 6.478 eV. Transmission measurements have also been performed in order to more accurately obtain low values of the absorption coefficient close to the band edge. Critical point parameters have been determined by analyzing the interband transitions. Infrared extended measurements yield vibrational modes corresponding to chemical bonding environments and the lattice structure. The overall analysis yields ε from 0.033 to 6.478 eV and provides information about the crystal such as the energy of the band gap at 4.16 ± 0.01 eV; interband transitions at 4.49, 4.75, 4.81, 5.08, 5.59, and 6.08 eV; transverse optical phonon modes at 283, 364, 395, 447, 702, 729, and 778 cm−1 and longitudinal optical phonon modes at 292, 386, 445, 458, 710, 779, and 817 cm−1.
Synchronization of networks of oscillators with distributed delay coupling
Authors: Kyrychko Y. N. , Blyuss K. B. , Schöll E.
Published: October 2014

This paper studies the stability of synchronized states in networks, where couplings between nodes are characterized by some distributed time delay, and develops a generalized master stability function approach. Using a generic example of Stuart-Landau oscillators, it is shown how the stability of synchronized solutions in networks with distributed delay coupling can be determined through a semi-analytic computation of Floquet exponents. The analysis of stability of fully synchronized and of cluster or splay states is illustrated for several practically important choices of delay distributions and network topologies.
Evidence of improved ferroelectric phase stabilization in Nd and Sc co-substituted BiFeO3
Authors: Durga Rao T. , Asthana Saket
Published: October 2014

Polycrystalline BiFeO3 and Bi0.9Nd0.1Fe1−xScxO3 (x = 0, 0.05, and 0.10) multiferroic compounds were prepared using conventional solid-state route. X-ray diffraction studies and Raman measurements indicated that the compounds were crystallized in rhombohedral structure with R3c space group. Weak ferromagnetism was induced due to the suppression of canted spin structure in the substituted compounds. Both remanent magnetization (Mr) and coercive field (Hc) were enhanced in Nd and Sc substituted compounds. Further, Néel temperature TN was decreased from 644 K for BiFeO3 to 550 K for Bi0.9Nd0.1Fe0.9Sc0.1O3 compound due to weakening of magnetic exchange interactions between B-site cations in the substituted compounds. Enhanced and nearly well saturated electrical polarizations were observed in Sc substituted compounds, which are attributed to the strengthening of covalent hybridization between Bi and O ions and reduction in oxygen vacancies. The remnant polarization was enhanced to 12.5 μC/cm2 in Bi0.9Nd0.1Fe0.9Sc0.1O3 compound. Impedance studies revealed that insulating character of substituted compounds is enhanced and electrical relaxations are of non-Debye type.
Modelling the acoustical response of lossy lamella-crystals
Authors: Christensen J. , Mortensen N. A. , Willatzen M.
Published: October 2014

The sound propagation properties of lossy lamella-crystals are analysed theoretically utilizing a rigorous wave expansion formalism and an effective medium approach. We investigate both supported and free-standing crystal slab structures and predict high absorption for a broad range of frequencies. A detailed derivation of the formalism is presented, and we show how the results obtained in the subwavelength and superwavelength regimes qualitatively can be reproduced by homogenizing the lamella-crystals. We come to the conclusion that treating this structure within the metamaterial limit only makes sense if the crystal filling fraction is sufficiently large to satisfy an effective medium approach.
Photoresponse properties of large-area MoS2 atomic layer synthesized by vapor phase deposition
Authors: Luo Siwei , Qi Xiang , Ren Long , Hao Guolin , Fan Yinping , Liu Yundan , Han Weijia , Zang Chen , Li Jun , Zhong Jianxin
Published: October 2014

Photoresponse properties of a large area MoS2 atomic layer synthesized by vapor phase deposition method without any catalyst are studied. Scanning electron microscopy, atomic force microscopy, Raman spectrum, and photoluminescence spectrum characterizations confirm that the two-dimensional microstructures of MoS2 atomic layer are of high quality. Photoelectrical results indicate that the as-prepared MoS2 devices have an excellent sensitivity and a good reproducibility as a photodetector, which is proposed to be ascribed to the potential-assisted charge separation mechanism.
A parametric study of the drift-tearing mode using an extended-magnetohydrodynamic model
Authors: King J. R. , Kruger S. E.
Published: October 2014

The linear, collisional, constant-ψ drift-tearing mode is analyzed for different regimes of the plasma-β, ion-skin-depth parameter space with an unreduced, extended-magnetohydrodynamic model. New dispersion relations are found at moderate plasma β and previous drift-tearing results are classified as applicable at small plasma β.
Novel free-form hohlraum shape design and optimization for laser-driven inertial confinement fusion
Authors: Jiang Shaoen , Jing Longfei , Huang Yunbao , Ding Yongkun
Published: October 2014

The hohlraum shape attracts considerable attention because there is no successful ignition method for laser-driven inertial confinement fusion at the National Ignition Facility. The available hohlraums are typically designed with simple conic curves, including ellipses, parabolas, arcs, or Lame curves, which allow only a few design parameters for the shape optimization, making it difficult to improve the performance, e.g., the energy coupling efficiency or radiation drive symmetry. A novel free-form hohlraum design and optimization approach based on the non-uniform rational basis spline (NURBS) model is proposed. In the present study, (1) all kinds of hohlraum shapes can be uniformly represented using NURBS, which is greatly beneficial for obtaining the optimal available hohlraum shapes, and (2) such free-form uniform representation enables us to obtain an optimal shape over a large design domain for the hohlraum with a more uniform radiation and higher drive temperature of the fuel capsule. Finally, a hohlraum is optimized and evaluated with respect to the drive temperature and symmetry at the Shenguang III laser facility in China. The drive temperature and symmetry results indicate that such a free-form representation is advantageous over available hohlraum shapes because it can substantially expand the shape design domain so as to obtain an optimal hohlraum with high performance.
Instability of the current sheet in the Earth's magnetotail with normal magnetic field
Authors: Bessho N. , Bhattacharjee A.
Published: October 2014

Instability of a current sheet in the Earth's magnetotail has been investigated by two-dimensional fully kinetic simulations. Two types of magnetic configuration have been studied; those with uniform normal magnetic field along the current sheet and those in which the normal magnetic field has a spatial hump. The latter configuration has been proposed by Sitnov and Schindler [Geophys. Res. Lett. 37, L08102 (2010)] as one in which ion tearing modes might grow. The first type of configuration exhibits electron tearing modes when the normal magnetic field is small. The second type of configuration exhibits an instability which does not tear or change the topology of magnetic field lines. The hump in the initial configuration can propagate Earthward in the nonlinear regime, leading to the formation of a dipolarization front. Secondary magnetic islands can form in regions where the normal magnetic field is very weak. Under no conditions do we find the ion tearing instability.
Optimizing minimum free-energy crossing points in solution: Linear-response free energy/spin-flip density functional theory approach
Authors: Minezawa Noriyuki
Published: October 2014

Examining photochemical processes in solution requires understanding the solvent effects on the potential energy profiles near conical intersections (CIs). For that purpose, the CI point in solution is determined as the crossing between nonequilibrium free energy surfaces. In this work, the nonequilibrium free energy is described using the combined method of linear-response free energy and collinear spin-flip time-dependent density functional theory. The proposed approach reveals the solvent effects on the CI geometries of stilbene in an acetonitrile solution and those of thymine in water. Polar acetonitrile decreases the energy difference between the twisted minimum and twisted-pyramidalized CI of stilbene. For thymine in water, the hydrogen bond formation stabilizes significantly the CI puckered at the carbonyl carbon atom. The result is consistent with the recent simulation showing that the reaction path via this geometry is open in water. Therefore, the present method is a promising way of identifying the free-energy crossing points that play an essential role in photochemistry of solvated molecules.
Josephson effects in an alternating current biased transition edge sensor
Authors: Gottardi L. , Kozorezov A. , Akamatsu H. , van der Kuur J. , Bruijn M. P. , den Hartog R. H. , Hijmering R. , Khosropanah P. , Lambert C. , van der Linden A. J. , Ridder M. L. , Suzuki T. , Gao J. R.
Published: October 2014

We report the experimental evidence of the ac Josephson effect in a transition edge sensor (TES) operating in a frequency domain multiplexer and biased by ac voltage at MHz frequencies. The effect is observed by measuring the non-linear impedance of the sensor. The TES is treated as a weakly linked superconducting system and within the resistively shunted junction model framework. We provide a full theoretical explanation of the results by finding the analytic solution of the non-inertial Langevian equation of the system and calculating the non-linear response of the detector to a large ac bias current in the presence of noise.
Theoretical study of hydrogen storage in binary hydrogen-methane clathrate hydrates
Authors: Belosludov R. V. , Zhdanov R. K. , Subbotin O. S. , Mizuseki H. , Kawazoe Y. , Belosludov V. R.
Published: October 2014

The properties of binary H2 + CH4 clathrate hydrates have been estimated using the extended van der Waals and Platteeuw statistical thermodynamic model that takes into account the lattice relaxation, host-guest, and guest-guest interactions as well as the quantum nature of guest behavior in the clathrate cavities. It has been found that at a small methane concentration in the gas phase the stable hydrate phase has cubic structure II (CS-II) and at a methane concentration of 6% stabilizes cubic structure I, which is metastable in the case of the pure hydrogen hydrate. This is in agreement with recent experimental data. The amount of hydrogen storage depends on the methane concentration in the gas phase as well as the thermodynamic conditions of hydrate formation. Hydrogen storage up to 2.6 wt. % can be achieved in the binary H2 + CH4 CS-II hydrate at T = 250 K.
Integrated energy-exergy-based evaluation and optimization of a bio-dimethyl ether production system via entrained flow gasification
Authors: Xiang Yangyang , Zhou Jingsong , Chen Chao , Luo Zhongyang
Published: October 2014

In this paper, an integrated energy-exergy-based evaluation was conducted on an entire bio-dimethyl ether (bio-DME) system established using ASPEN PLUS. The system contained a novel combination of biomass torrefaction unit (BTU) and entrained-flow gasification (EFG) followed by single-step DME synthesis, including DME purification, as well as heat recovery and cogeneration. The mass and energy balances were calculated in detail and compared with those cited in previous literature. The overall energetic and exergetic efficiencies of the system were found to be 55.2% and 46.9%, respectively. The exergy rates for all processes involved in the system were calculated and the locations as well as magnitudes of exergy losses were determined. Subsequently, the causes of exergy losses were deeply analyzed followed by pointing out the corresponding improvement potentials. Further investigation indicated that considerable improvement could be achieved for BTU and EFG, where the largest and second largest exergy loss took place. According to the parametric investigation based on energetic and exergetic efficiencies, controlling the BTU and EFG operation at 250 °C and 1200 °C, respectively, was proposed to improve the efficiency of the system and increase the overall exergetic efficiency to 52.6% while reducing the total exergy losses by 5.7%.
Note: A micro-perfusion system for use during real-time physiological studies under high pressure
Authors: Maltas Jeff , Long Zac , Huff Alison , Maloney Ryan , Ryan Jordan , Urayama Paul
Published: October 2014

We construct a micro-perfusion system using piston screw pump generators for use during real-time, high-pressure physiological studies. Perfusion is achieved using two generators, with one generator being compressed while the other is retracted, thus maintaining pressurization while producing fluid flow. We demonstrate control over perfusion rates in the 10-μl/s range and the ability to change between fluid reservoirs at up to 50 MPa. We validate the screw-pump approach by monitoring the cyanide-induced response of UV-excited autofluorescence from Saccharomyces cerevisiae under pressurization.
Gate tuning of anomalous Hall effect in ferromagnetic metal SrRuO3
Authors: Shimizu Sunao , Takahashi Kei S. , Kubota Masashi , Kawasaki Masashi , Tokura Yoshinori , Iwasa Yoshihiro
Published: October 2014

The electric field effect on ferromagnetism offers a new dimension in the recent advancement of spintronics. We report on the gate control of transport properties in thin films of oxide-based ferromagnetic metal, SrRuO3. An electric double layer transistor configuration was utilized with an ionic liquid dielectric to apply a strong electric field on a SrRuO3 thin film of 5 monolayers in thickness. The application of gate voltage induced a clear electroresistance effect, despite a considerably-large initial carrier density of the order of 1022 cm−3. Furthermore, we found that the gate modulation of the anomalous Hall conductivity σxy, which was as large as ∼±40% at low temperatures, was about three times larger than that of the longitudinal conductivity σxx. The variation of σxy is characterized by the power-law scaling relation with σxx, which is widely observed in a bad metal regime of the charge transport.
Concentrating solar power contribution to the mitigation of C-emissions in power generation and corresponding extra-costs
Authors: Hernández-Moro J. , Martínez-Duart J. M.
Published: October 2014

In this paper, we first proceed to develop the mathematical tools for the calculation of CO2 emissions abatement (annual and total) due to the installation of concentrating solar power (CSP) plants instead of the traditional systems. For this, we take into account the targets for the CSP cumulative installed capacity from several scenarios elaborated by the International Energy Agency. We have also developed in this paper mathematical closed-form expressions for the evaluation of the extra-costs of implementing these scenarios, and calculated the unit costs of the CO2 emissions avoided by the new CSP systems. The obtained results are shown both graphically and numerically, and their applications to energy planning policies are discussed. From the results exposed in this paper, it is possible to evaluate the economic advantages of installing the new CSP plants in those geographical areas with higher pollutant electricity mixes, as well as the planning of the most convenient calendar for CSP systems implementation.
Low-frequency, self-sustained oscillations in inductively coupled plasmas used for optical pumping
Authors: Coffer J. , Encalada N. , Huang M. , Camparo J.
Published: October 2014

We have investigated very low frequency, on the order of one hertz, self-pulsing in alkali-metal inductively-coupled plasmas (i.e., rf-discharge lamps). This self-pulsing has the potential to significantly vary signal-to-noise ratios and (via the ac-Stark shift) resonant frequencies in optically pumped atomic clocks and magnetometers (e.g., the atomic clocks now flying on GPS and Galileo global navigation system satellites). The phenomenon arises from a nonlinear interaction between the atomic physics of radiation trapping and the plasma's electrical nature. To explain the effect, we have developed an evaporation/condensation theory (EC theory) of the self-pulsing phenomenon.
Electron energy spectrum in circularly polarized laser irradiated overdense plasma
Authors: Liu C. S. , Tripathi V. K. , Shao Xi , Kumar Pawan
Published: October 2014

A circularly polarized laser normally impinged on an overdense plasma thin foil target is shown to accelerate the electrons in the skin layer towards the rear, converting the quiver energy into streaming energy exactly if one ignores the space charge field. The energy distribution of electrons is close to Maxwellian with an upper cutoff εmax=mc2[(1+a02)1/2−1], where a02=(1+(2ω2/ωp2)|ain|2)2−1, |ain| is the normalized amplitude of the incident laser of frequency ω, and ωp is the plasma frequency. The energetic electrons create an electrostatic sheath at the rear and cause target normal sheath acceleration of protons. The energy gain by the accelerated ions is of the order of εmax.