bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantum mechanical generalized phase-shift approach to atom-surface scattering: A Feshbach projection approach to dealing with closed channel effects
Authors: Maji Kaushik , Kouri Donald J.
Published: March 2011

We have developed a new method for solving quantum dynamical scattering problems, using the time-independent Schrödinger equation (TISE), based on a novel method to generalize a “one-way” quantum mechanical wave equation, impose correct boundary conditions, and eliminate exponentially growing closed channel solutions. The approach is readily parallelized to achieve approximate N2 scaling, where N is the number of coupled equations. The full two-way nature of the TISE is included while propagating the wave function in the scattering variable and the full S-matrix is obtained. The new algorithm is based on a “Modified Cayley” operator splitting approach, generalizing earlier work where the method was applied to the time-dependent Schrödinger equation. All scattering variable propagation approaches to solving the TISE involve solving a Helmholtz-type equation, and for more than one degree of freedom, these are notoriously ill-behaved, due to the unavoidable presence of exponentially growing contributions to the numerical solution. Traditionally, the method used to eliminate exponential growth has posed a major obstacle to the full parallelization of such propagation algorithms. We stabilize by using the Feshbach projection operator technique to remove all the nonphysical exponentially growing closed channels, while retaining all of the propagating open channel components, as well as exponentially decaying closed channel components.
Communication: Propagator for diffusive dynamics of an interacting molecular pair
Authors: Lee Sangyoub , Son Chang Yun , Sung Jaeyoung , Chong Song-Ho
Published: March 2011

We introduce a new method of solution for the Fredholm integral equations of the second kind. The method would be useful when the direct iterative approach leads to a divergent perturbation series solution. By using the method, we obtain an accurate expression of the propagator for diffusive dynamics of a pair of particles interacting via an arbitrary central potential and hydrodynamic interaction. We test the accuracy of the propagator expression by calculating the diffusion-controlled geminate and bimolecular reaction rates. It is shown that our propagator expression provides very accurate results for the whole time region.
Skyrmions, rational maps, and scaling identities
Authors: Charalampidis E. G. , Ioannidou T. A. , Manton N. S.
Published: March 2011

Starting from approximate Skyrmion solutions obtained using the rational map ansatz, improved approximate Skyrmions are constructed using scaling arguments. Although the energy improvement is small, the change of shape clarifies whether the true Skyrmions are more oblate or prolate.
A colorimetric receptor combined with a microcantilever sensor for explosive vapor detection
Authors: Zhu Weibin , Park Jung Su , Sessler Jonathan L. , Gaitas Angelo
Published: March 2011

Substantial effort has been devoted to the synthesis of molecular receptors that can function as chemosensors for nitroaromatic explosives. In spite of several advantages, these receptors suffer from low sensitivity and difficulties translating the response into the gas phase. We have combined tetrathiafulvalene-functionalized calix[4]pyrrole, a colorimetric receptor, with a polyimide microcantilever, that includes a mechanical stress sensing element. The resulting system is capable of detecting 10 ppb trinitrobenzene vapor. This represents a 30-fold improvement relative to the receptor in halogenated solvents, suggesting that this approach can provide a solution to translating the chemical response of colorimetric chemosensors into practical devices.
Evaluation of the Dyre shoving model using dynamic data near the glass temperature
Authors: Xu Ben , McKenna Gregory B.
Published: March 2011

The temperature dependence of the dynamics of glass-forming systems remains an important fundamental problem in glass physics. Here we use literature data [S. A. Hutcheson and G. B. McKenna, J. Chem. Phys. 129, 074502 (2008)] reanalyzed with the Baumgärtel–Schausberger–Winter (BSW) [M. Baumgärtel, A. Schausberger, and H. H. Winter, Rheol. Acta 29, 400 (1990); M. Baumgärtel and H. H. Winter, ibid. 28, 511 (1989); M. Baumgärtel and H. H. Winter, J. Non-Newtonian Fluid Mech. 44, 15 (1992)] model of complex fluid dynamics to evaluate the Dyre shoving model [J. C. Dyre, N. B. Olsen, and T. Christensen, Phys. Rev. B 53, 2171 (1996); J. C. Dyre, Rev. Mod. Phys. 78, 953 (2006)] that relates the temperature dependence of viscosity to the infinite-frequency shear modulus and its temperature dependence. In Dyre's model, the free-energy barrier for a “flow event” is attributed to the work done in shoving aside the surrounding molecules; the free-energy barrier is proportional to the glassy modulus, which increases as the temperature decreases. In the present work, the glassy modulus was obtained by the extrapolation to zero time or infinite frequency of the Kohlrausch–Williams–Watts (KWW) [G. Williams and D. C. Watts, Trans. Faraday Soc. 66, 80 (1970); F. Kolrausch, Pogg. Ann. Phys. 12, 393 (1847)] and BSW [M. Baumgärtel, A. Schausberger, and H. H. Winter, Rheol. Acta 29, 400 (1990); M. Baumgärtel and H. H. Winter, ibid. 28, 511 (1989); M. Baumgärtel and H. H. Winter, J. Non-Newtonian Fluid Mech. 44, 15 (1992)] functions to experimental data for m-toluidine and sucrose benzoate. It was found that the glassy modulus obtained from the KWW function for m-toluidine and sucrose benzoate [S. A. Hutcheson and G. B. McKenna, J. Chem. Phys. 129, 074502 (2008)] provides a consistent picture of the temperature-dependent dynamics within the framework of the shoving model. A similar analysis using a BSW description of the dynamics provides consistency for the sucrose benzoate but not for the m-toluidine.
Turbulence intensity pulse propagation with self-consistent nonlinear noise
Authors: Wang Z. H. , Diamond P. H. , Gürcan Ö. D. , Garbet X. , Wang X. G.
Published: March 2011

A model of turbulence intensity spreading with self-consistent nonlinear noise is derived systematically for the simple dynamical model of resistivity gradient driven turbulence. Local effective drive, thermal conduction damping, nonlinear coupling, and spatial scattering effects are included. As a consequence of nonlinear mode coupling processes (i.e., triad mode interactions), turbulence energy can be spatially scattered, leading to turbulence propagation and spreading. However, the range of any nonlinear mode interactions of the background with a test mode is restricted to within a few mode scale widths from the test mode rational surface. The speed of a turbulent spreading front is calculated. This front speed is effectively constant on macroscopic scales. We show that the effect of self-consistent nonlinear noise on the intensity front speed is modest, as a consequence of the ordering Δc<Lf, where Δc is the turbulence correlation length and Lf is the scale length of the front’s leading edge. The implications of these results for turbulence spreading models and the important differences between self-consistent mode coupling noise and ad hoc external noise are discussed. The broader implications of these results for turbulence front propagation are identified and explained.
Invited Article: Digital beam-forming imaging riometer systems
Authors: Honary Farideh , Marple Steve R. , Barratt Keith , Chapman Peter , Grill Martin , Nielsen Erling
Published: March 2011

The design and operation of a new generation of digital imaging riometer systems developed by Lancaster University are presented. In the heart of the digital imaging riometer is a field-programmable gate array (FPGA), which is used for the digital signal processing and digital beam forming, completely replacing the analog Butler matrices which have been used in previous designs. The reconfigurable nature of the FPGA has been exploited to produce tools for remote system testing and diagnosis which have proven extremely useful for operation in remote locations such as the Arctic and Antarctic. Different FPGA programs enable different instrument configurations, including a 4 × 4 antenna filled array (producing 4 × 4 beams), an 8 × 8 antenna filled array (producing 7 × 7 beams), and a Mills cross system utilizing 63 antennas producing 556 usable beams. The concept of using a Mills cross antenna array for riometry has been successfully demonstrated for the first time. The digital beam forming has been validated by comparing the received signal power from cosmic radio sources with results predicted from the theoretical beam radiation pattern. The performances of four digital imaging riometer systems are compared against each other and a traditional imaging riometer utilizing analog Butler matrices. The comparison shows that digital imaging riometer systems, with independent receivers for each antenna, can obtain much better measurement precision for filled arrays or much higher spatial resolution for the Mills cross configuration when compared to existing imaging riometer systems.
Synthesis and phosphorescence mechanism of a reddish orange emissive long afterglow phosphor Sm3+-doped Ca2SnO4
Authors: Ju Zhenghua , Wei Ruiping , Zheng Jiangrong , Gao Xiuping , Zhang Shuihe , Liu Weisheng
Published: March 2011

A reddish orange emissive long afterglow phosphor Ca2SnO4:Sm3+ was prepared by solid-state reaction in air atmosphere and characterized by photoluminescence, long-lasting phosphoresce. The afterglow time is more than 7 h which is the longest red or reddish orange long afterglow phosphor at the present time. The phosphorescence mechanism of the long afterglow phosphor was studied by thermoluminescence and positron annihilation lifetime experiments. The defects VCa″, structure defects Sn3+ and Sn2+ may act as hole trapping centers while the defects SmCa⋅ may act as electron trapping centers, and trapping centers play an essential role for photoenergy storage in persistent phosphors.
Optoelectronic properties of Al:ZnO: Critical dosage for an optimal transparent conductive oxide
Authors: Bazzani Mirco , Neroni Andrea , Calzolari Arrigo , Catellani Alessandra
Published: March 2011

We study the effects of aluminum doping on the electronic and optical properties of ZnO, via density functional simulations. We discuss the bandstructure and absorption properties of Al:ZnO as a function of the dopant concentration, and compare with recent experimental data. Our results support the formation of a transparent conductive oxide compound up to an incorporation of Al of about 3% in substitutional Zn sites. We propose an explanation to the observed degradation of conductivity in terms of interstitial defects expected to occur at high doping concentrations, beyond the Al solubility limit.
Effect of strain on bond-specific reaction kinetics during the oxidation of H-terminated (111) Si
Authors: Gokce Bilal , Aspnes David E. , Gundogdu Kenan
Published: March 2011

Although strain is used in semiconductor technology for manipulating optical, electronic, and chemical properties of semiconductors, the understanding of the microscopic phenomena that are affected or influenced by strain is still incomplete. Second-harmonic generation data obtained during the air oxidation of H-terminated (111) Si reveal the effect of compressive strain on this chemical reaction. Even small amounts of strain manipulate the reaction kinetics of surface bonds significantly, with tensile strain enhancing oxidation and compressive strain retarding it. This dramatic change suggests a strain-driven charge transfer mechanism between Si–H up bonds and Si–Si back bonds in the outer layer of Si atoms.
Multidepth, multiparticle tracking for active microrheology using a smart camera
Authors: Silburn Scott A. , Saunter Christopher D. , Girkin John M. , Love Gordon D.
Published: March 2011

The quantitative measurement of particle motion in optical tweezers is an important tool in the study of microrheology and can be used in a variety of scientific and industrial applications. Active microheology, in which the response of optically trapped particles to external driving forces is measured, is particularly useful in probing nonlinear viscoelastic behavior in complex fluids. Currently such experiments typically require independent measurements of the driving force and the trapped particle's response to be carefully synchronized, and therefore the experiments normally require analog equipment. In this paper we describe both a specialized camera and an imaging technique which make high-speed video microscopy a suitable tool for performing such measurements, without the need for separate measurement systems and synchronization. The use of a high-speed tracking camera based on a field programmable gate array to simultaneously track multiple particles is reported. By using this camera to simultaneously track one microsphere fixed to the wall of a driven sample chamber and another held in an optical trap, we demonstrate simultaneous optical measurement of the driving motion and the trapped probe particle response using a single instrument. Our technique is verified experimentally by active viscosity measurements on water–ethylene glycol mixtures using a phase-shift technique.
Trapping effect of metal nanoparticle mono- and multilayer in the organic field-effect transistor
Authors: Lee Keanchuan , Weis Martin , Lin Jack , Taguchi Dai , Majková Eva , Manaka Takaaki , Iwamoto Mitsumasa
Published: March 2011

The effect of silver nanoparticles self-assembled monolayer (Ag NPs SAM) on charge transport in pentacene organic field-effect transistors (OFET) was investigated by both steady-state and transient-state methods, which are current-voltage measurements in steady-state and time-resolved microscopic (TRM) second harmonic generation (SHG) in transient-state, respectively. The analysis of electronic properties revealed that OFET with SAM exhibited significant charge trapping effect due to the space-charge field formed by immobile charges. Lower transient-state mobility was verified by the direct probing of carrier motion by TRM-SHG technique. It was shown that the trapping effect rises together with increase of SAM layers suggesting the presence of traps in the bulk of NP films. The model based on the electrostatic charge barrier is suggested to explain the phenomenon.
Enhanced spin contrast of epitaxial Mn films on Fe(100) by spin-polarized scanning tunneling microscopy
Authors: Mishra Puneet , Uchihashi Takashi , Nakayama Tomonobu
Published: March 2011

The magnetic ordering in ultrathin Mn films grown on Fe(100) substrates is studied using spin-polarized scanning tunneling microscopy/scanning tunneling spectroscopy. Enhancement of spin contrast is observed due to a tip modification. Detailed analysis carried out using normalized dI/dV spectra indicates the appearance of resonant tunneling behavior. This is attributed to the attachment of a magnetic cluster at the apex of the magnetic thin film tip. Our results compare well with a recent theoretical prediction of a high vacuum spin-polarization of an Fe tip with an antiferromagnetically coupled Mn adatom [Ferriani et al., Phys. Rev. B 82, 054411 (2010)].
Experimental observation of a traveling plasma grating formed by two crossing filaments in gases
Authors: Durand Magali , Liu Yi , Forestier Benjamin , Houard Aurélien , Mysyrowicz André
Published: March 2011

The spatial motion and effective duration of a traveling plasma grating formed by two interfering femtosecond laser filaments in gases is characterized by its Doppler effect imparted on a probe pulse. The shift velocity determined experimentally agrees with the theoretical calculations.
Direct probing of evanescent field for characterization of porous terahertz fibers
Authors: Atakaramians Shaghik , Afshar V. Shahraam , Nagel Michael , Rasmussen Henrik K. , Bang Ole , Monro Tanya M. , Abbott Derek
Published: March 2011

We develop a technique based on a micromachined photoconductive probe-tip to characterize a terahertz (THz) porous fiber. Losses less than 0.08 cm−1 are measured in the frequency range from 0.2 to 0.35 THz, with the minimum of 0.003 cm−1 at 0.24 THz. Normalized group velocity greater than 0.8, which corresponds to dispersion values in between −1.3 and −0.5 ps/m/μm for 0.2<f<0.35 THz are obtained. Moreover, we directly measure the evanescent electric field as a function of frequency. Good agreement between the measured curves and expected theoretical values indicates the low invasiveness of the applied probe-tip.
Ab initio rovibronic states of the thioketenyl radical in its X2Π electronic ground state
Authors: Jutier Laurent , Dhont Guillaume
Published: March 2011

We present an ab initio study of the thioketenyl (HCCS) radical in its degenerate X2Π electronic ground state. All rotational and vibrational degrees of freedom are taken into account including the electronic orbital and spin angular momenta. The structure of the rovibronic levels and the nature of the corresponding wave functions show resonances even at very low energies due to strong couplings between the bending, rotation, and spin terms in the Hamiltonian. Assignments from the dominant contributions of the eigenvectors are discussed in parallel with previously published data. The rotational structures for the first excited vibronic states are computed as well as transition intensities for the fundamental one.
Solution-growth kinetics and thermodynamics of nanoporous self-assembled molecular monolayers
Authors: Bellec Amandine , Arrigoni Claire , Schull Guillaume , Douillard Ludovic , Fiorini-Debuisschert Céline , Mathevet Fabrice , Kreher David , Attias André-Jean , Charra Fabrice
Published: March 2011

The temperature and concentration dependences of the self-assembly onto graphite from solution of a series of molecular building blocks able to form nanoporous structures are analyzed experimentally by in situ scanning tunneling microscopy. It is shown that the commonly observed coexistence of dense and nanoporous domains results from kinetic blockades rather than a thermodynamic equilibrium. The ripening can be favored by high densities of domain boundaries, which can be obtained by cooling the substrate before the nucleation and growth. Then ripening at higher-temperature yields large defect-free domains of a single structure. This thermodynamically stable structure can be either the dense or the nanoporous one, depending on the tecton concentration in the supernatant solution. A sharp phase transition from dense to honeycomb structures is observed at a critical concentration. This collective phenomenon is explained by introducing interactions between adsorbed molecules in the thermodynamic description of the whole system.
Exponential tuning of the coupling constant of coupled microcantilevers by modifying their separation
Authors: Gil-Santos Eduardo , Ramos Daniel , Pini Valerio , Calleja Montserrat , Tamayo Javier
Published: March 2011

Vibration localization in coupled nanomechanical resonators has emerged as a promising concept for ultrasensitive mass sensing. It possesses intrinsic common mode rejection and the mass sensitivity can be enhanced with no need of extreme miniaturization of the devices. In this work, we have experimentally studied the role of the separation between cantilevers that are elastically coupled by an overhang. The results show that the coupling constant exponentially decays with the separation. In consistency with the theoretical expectations, the mass sensitivity is inversely proportional to the coupling constant. Finite element simulations show that the coupling constant can be exponentially reduced by increasing the ratio of the cantilever separation to the overhang length.
Surface-adsorption-induced bending behaviors of graphene nanoribbons
Authors: Zhang Zuoqi , Liu Bin , Hwang Keh-Chih , Gao Huajian
Published: March 2011

We investigate bending behaviors of graphene nanoribbons (GNRs) induced by surface adsorption of hydrogen atoms or molecules. At low adsorption coverage, it is shown that the chemical adsorption of hydrogen atoms causes a GNR to bend away from the adsorbed atoms while the physical adsorption of hydrogen molecules causes it to bend toward the adsorbed molecules. Interestingly, these trends are reversed at high adsorption coverage. There exists a range of linear responses for both chemical and physical adsorptions, which points to promising applications of GNRs as sensitive chemical-/biosensors.
Single-layer graphene cathodes for organic photovoltaics
Authors: Cox Marshall , Gorodetsky Alon , Kim Bumjung , Kim Keun Soo , Jia Zhang , Kim Philip , Nuckolls Colin , Kymissis Ioannis
Published: March 2011

A laminated single-layer graphene is demonstrated as a cathode for organic photovoltaic devices. The measured properties indicate that graphene offers two potential advantages over conventional photovoltaic electrode materials; work function matching via contact doping, and increased power conversion efficiency due to transparency. These findings indicate that flexible, light-weight all carbon solar cells can be constructed using graphene as the cathode material.
A tunneling field-effect transistor exploiting internally combined band-to-band and barrier tunneling mechanisms
Authors: Lattanzio Livio , Biswas Arnab , De Michielis Luca , Ionescu Adrian M.
Published: March 2011

This letter proposes a hybrid abrupt switch principle and a corresponding device architecture that combines quantum mechanical band-to-band and barrier tunneling mechanisms. The device overcomes the intrinsically low on-current (ION) of conventional tunnel field-effect transistors (TFETs) and the 60 mV/dec subthreshold swing limitation of metal-oxide-semiconductor FETs at room temperature. The device principle and characteristics are studied through two-dimensional numerical simulations. The predicted performance of such hybrid TFET architecture, implementing an ultrathin (0.5 nm) tunneling dielectric between metal source and silicon channel are: average SS values as low as 43 mV/dec, ION∼49.3 μA/μm, and ION/IOFF∼107.
Effect of surface produced secondary electrons on the sheath structure induced by high-power microwave window breakdown
Authors: Cheng Guoxin , Liu Lie
Published: March 2011

Dielectric window breakdown, whose mechanism is not thoroughly understood, is a major factor of limiting the transmission and radiation of high-power microwave on the order of 1 GW. In this paper, a one-dimensional fluid-like sheath model is developed to investigate the sheath structures formed at different gas pressures. The dominant processes during the surface flashover are isolated by this model. In vacuum, electron multipactor is self-sustained by secondary electron emission, a positive space-charge potential is formed on the dielectric surface. With increasing gas pressure, electron-neutral ionization prevails against secondary electron emission. The multipactor effect is suppressed by the shielding of plasma electrons. This leads to the sheath potential changing gradually from a positive space-charge potential to a negative space-charge potential. For argon gas pressure lower than 14 Torr, the sheath is space charge limited. A potential minimum could be formed in front of the dielectric which traps secondary electrons emitted from the wall. With the higher argon gas pressure, the number density of ions becomes comparable to that of electrons, all surface produced electrons are accelerated toward the presheath region. Therefore, the normal sheath is formed and the resulting surface flashover on the dielectric surface becomes rf-driven volumetric breakdown.
Bandfilling and photon-assisted tunneling in a quantum-well transistor laser
Authors: Feng M. , Bambery R. , Holonyak N.
Published: March 2011

Data and a phenomenological model for quantum-well (QW) transistor laser operation are presented showing, via the three-port input-output (electrical and optical) characteristics, the strong QW to collector coupling and the influence of bandfilling (QW states, Δhν recombination radiation, sensitivity of Eλ0→Eλ1,λ0→λ1,λ0>λ1) on base-to-collector photon-assisted tunneling and laser operation. Transistor (electrical) and laser (optical) operation are locked and “slide” up and down as a function of base current (IB), collector-base voltage (VBC or VCE), and the influence of QW bandfilling (with increased sensitivity at Eλ0→Eλ1) on photon-assisted base-collector tunneling.
The crystallization behavior of stoichiometric and off-stoichiometric Ga–Sb–Te materials for phase-change memory
Authors: Cheng Huai-Yu , Raoux Simone , Jordan-Sweet Jean L.
Published: March 2011

The stoichiometric Ga4Sb6Te3 and Ga–Sb materials were systemically studied. The alloy Ga4Sb6Te3 shows a fast crystallization speed, very high crystallization temperature, Tx, and high electrical contrast. Although stoichiometric GaSb has similar performance and even faster crystallization speed, the electrical contrast is much lower. The other off-stoichiometric compounds we studied all have higher Tx than Ge2Sb2Te5 indicating a good amorphous stability. By raising the Sb/Te ratio with GaSb incorporation, Tx and the recrystallization time of melt-quenched, amorphous samples can be effectively increased. The stoichiometric Ga4Sb6Te3 with less likelihood of phase-segregation compared to nonstoichiometric compounds is a promising candidate for phase-change memory.
Ultrafast carrier dynamics and saturable absorption of solution-processable few-layered graphene oxide
Authors: Zhao Xin , Liu Zhi-Bo , Yan Wei-Bo , Wu Yingpeng , Zhang Xiao-Liang , Chen Yongsheng , Tian Jian-Guo
Published: March 2011

Ultrafast carrier dynamics and saturable absorption of few-layered graphene oxide, well-dispersed in organic solvent, are studied using femtosecond pump-probe and Z-scan techniques. The results demonstrate that few-layered graphene oxide has a fast energy relaxation of hot carriers and strong saturable absorption, which is comparable with that of reduced graphene oxide. Fast carrier relaxation combined with well solution processing capability arises from the large fraction of sp2 carbon atom inside the few-layered graphene oxide sheet together with oxidation mainly existing at the edge areas. This superiority of few-layered graphene oxide will facilitate potential applications of graphene for ultrafast photonics.
Effect of channel thickness on density of states in amorphous InGaZnO thin film transistor
Authors: Lee Sang Yeol , Kim Do Hyung , Chong Eugene , Jeon Yong Woo , Kim Dae Hwan
Published: March 2011

We report on the origin of threshold voltage shift with the thickness of amorphous InGaZnO channel layer deposited by rf magnetron sputter at room temperature, using density of states extracted from multi frequency method and falling rates of activation energy, which of trends are entirely consistent each other in respect of the reduction of total traps with increasing the channel thickness. Furthermore, we shows that the behavior of ΔVth under the positive gate bias stress and thermal stress can be explained by charge trapping mechanism based on total trap variation.
Three color infrared detector using InAs/GaSb superlattices with unipolar barriers
Authors: Gautam N. , Naydenkov M. , Myers S. , Barve A. V. , Plis E. , Rotter T. , Dawson L. R. , Krishna S.
Published: March 2011

We report on a three color heterojunction band gap engineered type-II InAs/GaSb strained-layer superlattice photodiode for short-wave infrared (SWIR), mid-wave infrared (MWIR), and long-wave infrared (LWIR) detection. The reported structure is a three contact device with nBn architecture for SWIR and MWIR and heterojunction PIbN architecture for LWIR detection. At 77 K, the cutoff wavelength for SWIR, MWIR, and LWIR regions are 3.0 μm, 4.7 μm, and 10.1 μm, respectively. The reported architecture can be used for simultaneous detection in the LWIR/MWIR and LWIR/SWIR bands as well as sequential detection in the MWIR/SWIR bands by switching the polarity of the applied bias.
Near-infrared spectroscopy of LiNH3: First observation of the electronic spectrum
Authors: Varriale Luigi , Bhalla Nitika , Tonge Nicola M. , Ellis Andrew M. , Wright Timothy G.
Published: March 2011

Electronic spectra of LiNH3 and its partially and fully deuterated analogues are reported for the first time. The spectra have been recorded in the near-infrared and are consistent with two electronic transitions in close proximity, the $\tilde A$Ã2E−$\tilde X$X̃2A1 and $\tilde B$B̃2A1−$\tilde X$X̃2A1 systems. Vibrational structure is seen in both systems, with the Li–N–H bending vibration (ν6) dominant in the $\tilde A$Ã2E−$\tilde X$X̃2A1 system and the Li–N stretch (ν3) in the $\tilde B$B̃2A1−$\tilde X$X̃2A1 system. The prominence of the $6_0^1$601 band in the $\tilde A$Ã2E−$\tilde X$X̃2A1 spectrum is attributed to Herzberg–Teller coupling. The proximity of the $\tilde B$B̃2A1 state, which lies a little more than 200 cm−1 above the $\tilde A^2$Ã2E state, is likely to be the primary contributor to this strong vibronic coupling.
Electro-osmotic mobility of non-Newtonian fluids
Authors: Zhao Cunlu , Yang Chun
Published: March 2011

Electrokinetically driven microfluidic devices are usually used to analyze and process biofluids which can be classified as non-Newtonian fluids. Conventional electrokinetic theories resulting from Newtonian hydrodynamics then fail to describe the behaviors of these fluids. In this study, a theoretical analysis of electro-osmotic mobility of non-Newtonian fluids is reported. The general Cauchy momentum equation is simplified by incorporation of the Gouy–Chapman solution to the Poisson–Boltzmann equation and the Carreau fluid constitutive model. Then a nonlinear ordinary differential equation governing the electro-osmotic velocity of Carreau fluids is obtained and solved numerically. The effects of the Weissenberg number (Wi), the surface zeta potential (ψ¯s), the power-law exponent (n), and the transitional parameter (β) on electro-osmotic mobility are examined. It is shown that the results presented in this study for the electro-osmotic mobility of Carreau fluids are quite general so that the electro-osmotic mobility for the Newtonian fluids and the power-law fluids can be obtained as two limiting cases.
Deterministic integrated tuning of multicavity resonances and phase for slow-light in coupled photonic crystal cavities
Authors: Gu T. , Kocaman S. , Yang X. , McMillan J. F. , Yu M. B. , Lo G.-Q. , Kwong D.-L. , Wong C. W.
Published: March 2011

We present the integrated chip-scale tuning of multiple photonic crystal cavities. The optimized implementation allows effective and precise tuning of multiple cavity resonances (up to ∼1.60 nm/mW) and intercavity phase (∼0.038 π/mW) by direct local temperature tuning on suspended silicon nanomembranes. Through designing the serpentine metal electrodes and careful electron-beam alignment to avoid cavity mode overlap, the coupled photonic crystal L3 cavities preserve their high quality factors. The deterministic resonance and phase control enables switching between the all-optical analog of electromagnetically-induced-transparency to flat-top filter lineshapes, with future applications of trapping photons and optoelectronic modulators.
Terahertz-frequency photoconductive detectors fabricated from metal-organic chemical vapor deposition-grown Fe-doped InGaAs
Authors: Hatem O. , Cunningham J. , Linfield E. H. , Wood C. D. , Davies A. G. , Cannard P. J. , Robertson M. J. , Moodie D. G.
Published: March 2011

We report the detection of terahertz frequency radiation using photoconductive antennas fabricated from Fe-doped InGaAs, grown by metal-organic chemical vapor deposition. Coherent photoconductive detection is demonstrated using femtosecond laser pulses centered at either an 800 or a 1550 nm wavelength. The InGaAs resistivity and the sensitivity of photoconductive detection are both found to depend on the Fe-doping level. We investigate a wide range of probe laser powers, finding a peak in detected signal for ∼5 mW probe power, followed by a reduction at larger powers, attributed to screening of the detected THz field by photo-generated carriers in the material. The measured signal from Fe:InGaAs photoconductive detectors excited at 800 nm is four times greater than that from a low-temperature-grown GaAs photodetector with identical antenna design, despite the use of a ten times smaller probe power.
Conservation of a rare arboreal mammal: habitat preferences of the Lumholtz's tree-kangaroo, Dendrolagus lumholtzi
Authors: Heise-Pavlov Sigrid R. , Jackrel Sara L. , Meeks Spenser
Published: March 2011

Success of conservation efforts of large and cryptic mammals is often limited due to a lack of knowledge of their habitat preferences. This study investigates factors that affect the habitat selection of the rare Lumholtz’s tree-kangaroo, Dendrolagus lumholtzi, using signs of its activity. The presence and absence of scratch marks on tree trunks and faecal pellets within a 100-cm radius around them were surveyed on 23 ha within a 65-ha large fragment of rainforest on the Atherton Tablelands, north-eastern Australia in order to classify trees as ‘actively used’ or ‘inactive’. Structural features of the 315 surveyed tree trunks were also recorded. Using discriminant function analysis, ‘actively used’ trees were found to have no epiphytes on the main trunk, less obstruction by neighbouring trees, shrubs or lianas within a 0.5-m radius of the trunk (particularly in the eastern direction), and a smaller diameter at breast height than ‘inactive’ trees. Smaller tree trunks and less obstruction may facilitate a more rapid movement into the canopy as well as provide potential escape routes from predators. More specific knowledge on factors that affect habitat selection of the Lumholtz’ tree-kangaroo will help in a reclassification of the threatened status of this species and assist in more effective conservation efforts.
Captive breeding of the sandhill dunnart, Sminthopsis psammophila (Marsupialia:Dasyuridae): reproduction, husbandry and growth and development
Authors: Lambert Cathy , Gaikhorst Glen , Matson Phillip
Published: March 2011

Little is known of the reproductive biology of the endangered sandhill dunnart (Sminthopsis psammophila). This study demonstrates the first captive breeding of the species, defines several important reproductive parameters and documents morphological development of the young. The study confirmed field speculation that S. psammophila is a seasonal breeder and adopts a life-history strategy similar to that of other arid-zone Sminthopsinae. The average (range) interval from mating to birth is 18 (16–19) days.
Helminth parasite communities in four species of sympatric macropodids in western Victoria
Authors: Aussavy M. , Bernardin E. , Corrigan A. , Hufschmid J. , Beveridge I.
Published: March 2011

Helminth parasites of Macropus fuliginosus, M. giganteus, M. rufogriseus and Wallabia bicolor were examined in a region of western Victoria, Australia, where all four species of hosts are sympatric. M. fuliginosus and M. giganteus shared most of their parasites while the helminth communities of M. rufogriseus and W. bicolor were distinctive. The sympatric distribution of the host species studied provides evidence in support of the hypothesis that the differences between the parasite communities of M. fuliginosus–M. giganteus compared with those of M. rufogriseus and W. bicolor are due to parasite specificity rather than to host ecological differences. However, lack of detailed data on the ecological differences of these hosts in areas of sympatry prevents more precise conclusions being drawn on the reasons for the distinctiveness of the parasite communities.
Nest use by western pygmy-possums (Cercartetus concinnus) (Marsupialia:Burramyidae) at Innes National Park, South Australia
Authors: Morrant Damian S. , Petit Sophie
Published: March 2011

We examined the nest use of 15 radio-tracked western pygmy-possums (Cercartetus concinnus) throughout one year for up to nine nights each at Innes National Park, South Australia. At least one pygmy-possum was followed in each of 12 months. Nest type and nest fidelity varied greatly; shallow burrows under debris were the most frequently used. Nest preferences of females with young remain unknown. The ability of C. concinnus to use a diversity of nest types over relatively short periods is likely to be an important survival strategy.
Den trees, hollow-bearing trees and nest boxes: management of squirrel glider (Petaurus norfolcensis) nest sites in tropical Australian woodland
Authors: Ball Tina , Goldingay Ross L. , Wake Judith
Published: March 2011

The squirrel glider (Petaurus norfolcensis) is an arboreal marsupial potentially impacted throughout its geographic range by the loss of hollow-bearing trees. We investigated the use of den trees and the availability of hollow-bearing trees near Mackay in the tropical north of the squirrel glider range where information was deficient. Mean den tree size (41.1 ± 2.9 cm (s.e.), diameter at breast height (dbh)) was significantly larger than that of available trees (27.5 ± 0.9 cm). Dead trees (stags) comprised 52% of 27 dens but comprised only 12% of available trees. This likely reflects the greater frequency of hollows in dead trees compared with other trees. Surveys found that 59% of 720 available trees contained hollows. A much lower percentage of trees in the 10–30-cm dbh size class were hollow-bearing (22%) compared with trees >30 cm (77%), and we view these smaller trees as those providing future den trees. Their density varied from 17 to 95 ha–1 among sites, which suggests that most sites have an adequate supply of future hollows. We installed 56 nest boxes to determine use by squirrel gliders. Only 20% were used after 3 years, but use was not influenced by the availability of tree hollows. Tree hollow availability appears adequate for the squirrel glider in these tropical woodlands but further studies are needed to understand the dynamic processes that govern this resource.
Phylogenetics of hopbushes and pepperflowers (Dodonaea, Diplopeltis - Sapindaceae), based on nuclear ribosomal ITS and partial ETS sequences incorporating secondary-structure models
Authors: Harrington Mark G. , Gadek Paul A.
Published: March 2011

Hopbushes and pepperflowers (Dodonaea, Diplopeltis – Sapindaceae) are important components of Australia’s arid zone and sclerophyll and temperate forests and woodlands. Phylogenetic analyses of nuclear ribosomal ITS and partial ETS sequences for near-complete sampling of both genera were performed using a Bayesian statistical method and RNA specific models of nucleotide evolution that incorporate secondary structure (separate models for stems and loops). Diplopeltis is paraphyletic. Diplopeltis stuartii is not closer to other species of the genus than it is to species outside the genus. There are also several evolutionary elements in the molecular data that support D. stuartii as distinct from the other members of the genus. The monophyly of Dodonaea as redefined here to include all species of Distichostemon is unequivocally supported by the molecular data and the morphological synapomorphies of petal-less flowers with a highly reduced intrastaminal disk that is absent in staminate flowers. There do not appear to be any obvious evolutionary trends in the morphological characters (leaf and capsule form, presence or absence of aril, or breeding system) that have been previously used to group taxa. However, there are some morphological characters that may be useful to delineate some of the clades recovered in the present molecular study. New combinations in Dodonaea are made for all species of Distichostemon.
Evolution of nickel hyperaccumulation by Stackhousia tryonii (Celastraceae), a serpentinite-endemic plant from Queensland, Australia
Authors: Burge Dylan O. , Barker W. R.
Published: March 2011

To elucidate the evolutionary origin of nickel (Ni) hyperaccumulation by the Australian serpentinite-endemic plant Stackhousia tryonii Bailey, phylogenetic analyses of chloroplast and nuclear DNA for Stackhousia and its close relatives were combined with assays of plant-tissue Ni concentrations. Thirty-five plants from 20 taxa were analysed by sequencing nuclear rDNA (ITS) and the plastid trnL–F region. Phylogenetic analysis of sequence data was conducted under maximum parsimony and Bayesian search criteria. In all, 100 plants from 39 taxa, including all 33 Stackhousia species, were analysed for Ni concentration by radial inductively coupled plasma atomic-emission spectrometry (ICP–AES). In phylogenetic analyses, S. tryonii was monophyletic, nested within a monophyletic Stackhousia. Only S. tryonii contained concentrations of Ni above the hyperaccumulation threshold (0.1%; 1000 ppm), containing between 0.25% (2500 ppm) and 4.1% (41 000 ppm) Ni by dry weight. Nickel-hyperaccumulation ability appears to have been acquired once during diversification of Stackhousia, by S. tryonii.
The Lejeunea tumida species group (Lejeuneaceae: Jungermanniopsida) in New Zealand
Authors: Renner Matt A. M. , Brown Elizabeth A. , Wardle Glenda M.
Published: March 2011

Plants attributed to Lejeunea tumida comprise a heterogeneous aggregate of four morphologically distinct species, each circumscribed by subtle yet significant differences in perianth morphology, oil bodies, lobule morphology and lobe ornamentation. Size and shape also have utility in delimiting species, despite morphological overlap. We employ geometric morphometric methods to quantify and communicate diagnostic differences in lobule shape. Two new species, Lejeunea oracola M.A.M.Renner and Lejeunea rhigophila M.A.M.Renner are described, and a previously described species of Taxilejeunea reinstated as a new combination, Lejeunea colensoana (Steph.) M.A.M.Renner. Descriptions and illustrations of these three species and Lejeunea tumida Mitt. are presented. All four species occur in New Zealand. Although L. tumida has been reported for New South Wales, Victoria, and Tasmania, the identities of Australian plants comprising these records are largely unresolved, and require further investigation.
Premigration ethnic and national identities: Jewish adolescents planning emigration from Russia and Ukraine to Israel
Authors: Tartakovsky Eugene
Published: March 2011

The ethnic and national identities of Jewish high‐school adolescents planning emigration from Russia and Ukraine to Israel were investigated about six months before their emigration. The national identities of adolescent emigrants (n = 243) were compared with those of non‐emigrant Russian and Ukrainian adolescents (n = 740). The emigrants’ attitude to their country of origin was less positive and their identification with Russians and Ukrainians was weaker as compared with the non‐emigrant adolescents. In addition, the attitude of the emigrants towards Israel was more positive than their attitude to Russia or Ukraine. Finally, the emigrants’ strongest identification was with the Jewish people, followed by identification with Israelis, while their weakest identification was with Russians and Ukrainians. Israeli and Jewish identities of the emigrant adolescents were positively correlated, and they were independent of the Russian and Ukrainian identities. Perceived discrimination was negatively correlated with the emigrants’ attitude to Russia or Ukraine, and it was positively correlated with the emigrants’ identification with Israelis and with the Jewish people. Jewish ethnicity was correlated with identification with Jewish people; however, it was not correlated with any component of the Israeli or Russian/Ukrainian identities. The study results indicate that in the premigration period emigrants form a multidimensional system of ethnic and national identities, which reflects their partial detachment from their homeland and affiliation with the country of provisional immigration. This premigration identity system may be termed “anticipatory” (cf. Merton, 1968), because it is not based on real contact with the country of provisional immigration, but rather on the emigrants’ expectations. On the other hand, the premigration identities are reactive, in the sense that they reflect the emigrants’ reaction to the perceived discrimination they experience in their country of origin. The results of the present study are discussed in light of social identity theory.
Intimate boundaries: Therapists’ perception and experience of erotic transference within the therapeutic relationship
Authors: Rodgers Nicky M.
Published: March 2011

Aim: This study explored therapists’ understanding and experiences of erotic transference within therapeutic relationships. Method: A small‐scale qualitative research project was undertaken with six therapists working within different counselling contexts. Data was collected through semi‐structured face‐to‐face interviews, and an Interpretative Phenomenological Analysis used for analysis of individual perception and experience. Findings: All participants had experienced what they understood to be erotic transference and/or sexual and loving feelings within therapy. There was little differentiation between the two phenomena, and both were often referred to interchangeably. There were contradictory views as to whether using the phenomena would be beneficial to client work, but there was a strong motivation to learn more about it. Therapists who encountered sexual attraction within therapy experienced feelings including shame and embarrassment. Supervisory support was seen to be beneficial. Implications/conclusion: The importance for therapists to acknowledge a lack of clarity that exists around the understanding of erotic transference and its relationship to sexual attraction within therapy is noted. Also, a recognition that better access to training regarding erotic transference and sexual responsibility within client relationships might be helpful to therapists in their work.
Rapid communication: Automatic priming of grip force following action observation
Authors: Salama Islam Mohamed , Turner Sarah , Edwards Martin Gareth
Published: March 2011

Research shows that action observation can prime execution. Evidence for this comes from experiments that show that action observation influenced temporal (e.g., speed) or spatial (e.g., peak grasp aperture or trajectory) aspects of executed movement. In the paper presented here, we for the first time show that observation can also prime executed action force. Following observation of force actions, participants executed grip-force responses using a dynamometer, and the data showed that their force was modulated by the condition observed. The findings of the study are discussed in terms of a likely cause of the force modulation effect and potential uses that the effect may have for strength rehabilitation.