bluuebunny/crossref_metadata_2025 huggingface dataset:
The intrinsic structure of the water surface
Authors: Chacón Enrique , Tarazona Pedro , Alejandre José
Published: July 2006

An operational procedure to obtain the intrinsic structure of liquid surfaces is applied here to a molecular dynamics simulation of water, with a model of point charges for the molecular interactions. The method, which had been recently proposed and used for simple fluids, is successfully extended to a molecular liquid with the complex bond structure of water. The elimination of the capillary wave fluctuations, in the intrinsic density and orientation profiles, gives a new overall view of the water surface, at the sharpest molecular level, and without the size-dependent broadening observed in the mean profiles. The molecules belonging to the outer liquid layer are clearly identified, and we find that only these molecules exhibit a clear preferential orientation to lie flat on the surface. Moreover, there is a strong correlation between the dipolar structure and the local curvatures of the intrinsic surface, so that at the extrusions of the intrinsic surface the molecular dipoles point preferentially toward the vapor side of the interface. Finally, we have found an intrinsic density layering structure, although the inner structure is strongly damped beyond the second layer.
Dynamically screened local correlation method using enveloping localized orbitals
Authors: Auer Alexander A. , Nooijen Marcel
Published: July 2006

In this paper we present a local coupled cluster approach based on a dynamical screening scheme, in which amplitudes are either calculated at the coupled cluster level (in this case CCSD) or at the level of perturbation theory, employing a threshold driven procedure based on MP2 energy increments. This way, controllable accuracy and smooth convergence towards the exact result are obtained in the framework of an a posteriori approximation scheme. For the representation of the occupied space a new set of local orbitals is presented with the size of a minimal basis set. This set is atom centered, is nonorthogonal, and has shapes which are fairly independent of the details of the molecular system of interest. Two slightly different versions of combined local coupled cluster and perturbation theory equations are considered. In the limit both converge to the untruncated CCSD result. Benchmark calculations for four systems (heptane, serine, water hexamer, and oxadiazole-2-oxide) are carried out, and decay of the amplitudes, truncation error, and convergence towards the exact CCSD result are analyzed.
Darwin and mass-velocity relativistic corrections in the non-Born-Oppenheimer calculations of pure vibrational states of H2
Authors: Kȩdziera Dariusz , Stanke Monika , Bubin Sergiy , Barysz Maria , Adamowicz Ludwik
Published: July 2006

The Darwin and mass-velocity relativistic corrections have been calculated for all pure vibrational states of the H2 using the perturbation theory and very accurate variational wave functions obtained without assuming the Born-Oppenheimer (BO) approximation. Expansions in terms of explicitly correlated Gaussians with premultipliers in the form of even powers of the internuclear distance were used for the wave functions. With the inclusion of the two relativistic corrections to the non-BO energies the transition energies for the highest states agree more with the experimental results.
On correlated electron-nuclear dynamics using time-dependent density functional theory
Authors: Maitra Neepa T.
Published: July 2006

We discuss possibilities and challenges for describing correlated electron and nuclear dynamics within a surface-hopping framework using time-dependent density functional theory (TDDFT) for the electron dynamics. We discuss the recent surface-hopping method proposed by Craig et al. [Phys. Rev. Lett. 95, 163001 (2005)] that is based on Kohn-Sham potential energy surfaces. Limitations of this approach arise due to the Kohn-Sham surfaces generally having different gradients than the true TDDFT-corrected ones. Two mechanisms of the linear response procedure cause this effect: we illustrate these with examples.
Estimations of intrinsic and extrinsic noise in models of nonlinear genetic networks
Authors: Scott Matthew , Ingalls Brian , Kærn Mads
Published: July 2006

We discuss two methods that can be used to estimate the impact of internal and external variability on nonlinear systems, and demonstrate their utility by comparing two experimentally implemented oscillatory genetic networks with different designs. The methods allow for rapid estimations of intrinsic and extrinsic noise and should prove useful in the analysis of natural genetic networks and when constructing synthetic gene regulatory systems.
Optimization of laser-focused deposition lines: Rydberg atoms
Authors: Nguyen Nam A. , Shapiro Moshe , Brumer Paul
Published: July 2006

Optimally narrow nanoscale lines are computationally obtained for Rb Rydberg atoms deposited on surfaces. The use of optimized polychromatic fields is shown to allow lines as narrow as 1nm in the absence of transverse velocities and shown to counter the deleterious effects of transverse velocities in laser cooled beams. Specifically, lines as narrow as 6.5nm wide are obtained in the presence of transverse velocities associated with a temperature of 1mK. Using this approach it is possible to deposit a single narrow line, even when the atomic beam is bigger than the period of the focusing lens, using as few as two, relatively weak, laser fields.
Solvent response and dielectric relaxation in supercooled butyronitrile
Authors: Ito Naoki , Duvvuri Kalyan , Matyushov Dmitry V. , Richert Ranko
Published: July 2006

We have measured the dynamics of solvation of a triplet state probe, quinoxaline, in the glass-forming dipolar liquid butyronitrile near its glass transition temperature Tg=95K. The Stokes shift correlation function displays a relaxation time dispersion of considerable magnitude and the optical linewidth changes along the solvation coordinate in a nonmonotonic fashion. These features are characteristic of solvation in viscous solvents and clearly indicate heterogeneous dynamics, i.e., spatially distinct solvent response times. Using the dielectric relaxation data of viscous butyronitrile as input, a microscopic model of dipolar solvation captures the relaxation time, the relaxation dispersion, and the amplitude of the dynamical Stokes shift remarkably well.
A Michelson interferometer in the field of a plane gravitational wave
Authors: Popławski Nikodem J.
Published: July 2006

We treat the problem of a Michelson interferometer in the field of a plane gravitational wave in the framework of general relativity. The arms of the interferometer are regarded as the world lines of the light beams, whose motion is determined by the Hamilton-Jacobi equation for a massless particle. In the case of a weak monochromatic wave we find that the formula for the delay of a light beam agrees with the result obtained by solving the linearized coupled Einstein-Maxwell equations. We also calculate this delay in the next (quadratic) approximation.
A semiclassical hybrid approach to many particle quantum dynamics
Authors: Grossmann Frank
Published: July 2006

We analytically derive a correlated approach for a mixed semiclassical many particle dynamics, treating a fraction of the degrees of freedom by the multitrajectory semiclassical initial value method of Herman and Kluk [Chem. Phys. 91, 27 (1984)] while approximately treating the dynamics of the remaining degrees of freedom with fixed initial phase space variables, analogously to the thawed Gaussian wave packet dynamics of Heller [J. Chem. Phys. 62, 1544 (1975)]. A first application of this hybrid approach to the well studied Secrest-Johnson [J. Chem. Phys. 45, 4556 (1966)] model of atom-diatomic collisions is promising. Results close to the quantum ones for correlation functions as well as scattering probabilities could be gained with considerably reduced numerical effort as compared to the full semiclassical Herman-Kluk approach. Furthermore, the harmonic nature of the different degrees of freedom can be determined a posteriori by comparing results with and without the additional approximation.
Eluding oblivion with smart stochastic selection of synaptic updates
Authors: Fusi Stefano , Senn Walter
Published: July 2006

The variables involved in the equations that describe realistic synaptic dynamics always vary in a limited range. Their boundedness makes the synapses forgetful, not for the mere passage of time, but because new experiences overwrite old memories. The forgetting rate depends on how many synapses are modified by each new experience: many changes means fast learning and fast forgetting, whereas few changes means slow learning and long memory retention. Reducing the average number of modified synapses can extend the memory span at the price of a reduced amount of information stored when a new experience is memorized. Every trick which allows to slow down the learning process in a smart way can improve the memory performance. We review some of the tricks that allow to elude fast forgetting (oblivion). They are based on the stochastic selection of the synapses whose modifications are actually consolidated following each new experience. In practice only a randomly selected, small fraction of the synapses eligible for an update are actually modified. This allows to acquire the amount of information necessary to retrieve the memory without compromising the retention of old experiences. The fraction of modified synapses can be further reduced in a smart way by changing synapses only when it is really necessary, i.e. when the post-synaptic neuron does not respond as desired. Finally we show that such a stochastic selection emerges naturally from spike driven synaptic dynamics which read noisy pre and post-synaptic neural activities. These activities can actually be generated by a chaotic system.
Noise in genetic and neural networks
Authors: Swain Peter S. , Longtin André
Published: July 2006

Both neural and genetic networks are significantly noisy, and stochastic effects in both cases ultimately arise from molecular events. Nevertheless, a gulf exists between the two fields, with researchers in one often being unaware of similar work in the other. In this Special Issue, we focus on bridging this gap and present a collection of papers from both fields together. For each field, the networks studied range from just a single gene or neuron to endogenous networks. In this introductory article, we describe the sources of noise in both genetic and neural systems. We discuss the modeling techniques in each area and point out similarities. We hope that, by reading both sets of papers, ideas developed in one field will give insight to scientists from the other and that a common language and methodology will develop.
First-principles calculations of zero-field splitting parameters
Authors: Ganyushin Dmitry , Neese Frank
Published: July 2006

In this work, an implementation of an approach to calculate the zero-field splitting (ZFS) constants in the framework of ab initio methods such as complete active space self-consistent field, multireference configuration interaction, or spectroscopy oriented configuration interaction is reported. The spin-orbit coupling (SOC) contribution to ZFSs is computed using an accurate multicenter mean-field approximation for the Breit-Pauli Hamiltonian. The SOC parts of ZFS constants are obtained directly after diagonalization of the SOC operator in the basis of a preselected number of roots of the spin-free Hamiltonian. This corresponds to an infinite order treatment of the SOC in terms of perturbation theory. The spin-spin (SS) part is presently estimated in a mean-field fashion and appears to yield results close to the more complete treatments available in the literature. Test calculations for the first- and second-row atoms as well as first-row transition metal atoms and a set of diatomic molecules show accurate results for the SOC part of ZFSs. SS contributions have been found to be relatively small but not negligible (exceeding 1cm−1 for oxygen molecule). At least for the systems studied in this work, it is demonstrated that the presented method provides much more accurate estimations for the SOC part of ZFS constants than the emerging density functional theory approaches.
Counter-ion perturbation of the fragmentation pathways of multiply charged anions: Evidence for exit channel complexes on the fragmentation potential energy surfaces
Authors: Burke Ruth M. , Boxford William E. , Dessent Caroline E. H.
Published: July 2006

We report the first low-energy collisional excitation measurements and density functional theory calculations to characterize the ground state potential energy surfaces of contact ion-pair complexes that contain multiply charged anions (MCAs). Excitation of K+∙Pt(CN)42− and K+∙Pt(CN)62− result in fragmentation products associated with decay of the isolated constituent dianions, revealing that the ground state ion-pair surfaces are dominated by the intrinsic characteristics of the MCA. This observation is important since it indicates that counter-ion complexation only weakly perturbs the electronic structure of an MCA. For K+∙Pt(CN)42−, where the Pt(CN)42− dianion decays with production of two ionic fragments, we observe evidence for the existence of a novel exit-channel complex corresponding to a polar KCN salt unit bound to the Pt(CN)3− anion. The results described provide a basis for understanding the potential energy surfaces and fragmentation characteristics of other ion-pair complexes that involve MCAs.
Intense photoluminescence from amorphous tantalum oxide films
Authors: Zhu Minmin , Zhang Zhengjun , Miao Wei
Published: July 2006

Tantalum oxide films were deposited on silicon substrates at a temperature of ∼450°C by heating a pure tantalum foil in a rough vacuum. The films were amorphous in structure and consisted of fully oxidized Ta2O5 and (TaOx, x<2.5) suboxides. This feature resulted in strong visible light emission from the films further oxidized in the air at temperatures of 200–300°C. The mechanism for this photoluminescence behavior of the amorphous tantalum oxide films was also investigated and discussed. This study suggests that wide-band-gap materials could act as effective visible light emitters and provides a simple route to synthesize such materials.
Improved oxygen diffusion model to explain the effect of low-temperature baking on high field losses in niobium superconducting cavities
Authors: Ciovati Gianluigi
Published: July 2006

Radio-frequency (rf) superconducting cavities made of high purity niobium are widely used to accelerate charged particle beams in particle accelerators. The major limitation to achieve rf field values approaching the theoretical limit for niobium is represented by “anomalous” losses which degrade the quality factor of the cavities starting at peak surface magnetic fields of about 100mT, in the absence of field emission. These high field losses are often referred to as Q drop. It has been observed that the Q drop is drastically reduced by baking the cavities at 120°C for about 48h under ultrahigh vacuum. An improved oxygen diffusion model for the niobium-oxide system is proposed to explain the benefit of the low-temperature baking on the Q drop in niobium superconducting rf cavities. The model shows that baking at 120°C for 48h allows oxygen to diffuse away from the surface, and therefore increasing the lower critical field towards the value for pure niobium.
Phase change observation in reflection multilayers by total electron yield and reflection spectra
Authors: Ejima Takeo , Harada Tetsuo , Yamazaki Atsushi
Published: July 2006

Precise optical elements for use in the extreme ultraviolet region are necessary for controlling both the uppermost layer thickness and the reflection phase in a reflection multilayer system. In this study, a phase value corresponding to both the uppermost layer thickness and the reflection phase was derived from the reflectance and total electron yield (TEY) intensity. Mo∕Si multilayers were fabricated on a silicon wafer with various thicknesses of the uppermost Mo layer. Phase values obtained from the reflection and TEY measurements were found to change in accordance with increases in the thickness of the uppermost Mo layer and a concomitant change in the reflection phase.
Ionic to mixed ionic/electronic conduction transition of chemically lithiated Li0.33La0.56TiO3 at room temperature: Lithium-ion-motion dependent electron hopping
Authors: Yang Kai-Yun , Fung Kuan-Zong
Published: July 2006

The interfacial instability of metallic lithium and cation-vacant lithium lanthanum titanate results in the presence of Ti3+ donors and an increased number of Li+ ions at the Li0.33La0.56TiO3 side. It is clarified that the intercalated Li+ ion and the Ti-site electron are favorable to form a coupled Li+∕e− state to maintain the lowest electrostatic potential energy. Through the motion of these states, the interfacial instability is reflected in the electrical transition of Li0.33La0.56TiO3, in which the change of bulk electronic conduction from an insulator to a n-type semiconductor is determined by the lithium-ion-motion dependent electron hopping.
Mechanical atom manipulation with small amplitude dynamic force microscopy
Authors: Kawai Shigeki , Kawakatsu Hideki
Published: July 2006

We demonstrate atom manipulations of the Si(111)-(7×7) surface with small amplitude dynamic force microscopy at room temperature. Adatoms could not only be extracted and attached but also laterally manipulated in and over the half unit cell with a repulsive interaction force caused between the tip and the sample. In the case of a tip condition that gave a strong image contrast, an adatom beside a vacancy could be pulled to the neighboring stable site with a strong attractive force. Enhanced detection sensitivity due to the small amplitude of 4Å could avoid accidental modifications of the surface during imaging.
First-principles prediction of low shear-strain resistance of Al3BC3: A metal borocarbide containing short linear BC2 units
Authors: Wang Jingyang , Zhou Yanchun , Liao Ting , Lin Zhijun
Published: July 2006

The elastic stiffness and shear deformation mode of Al3BC3, a metal borocarbide containing linear C–B–C units, are studied based on the first-principles total energy calculations. The predominant effect of C–B–C units on mechanical properties is reported by leading to low shear modulus. The low shear-strain resistance originates from the deformation mode as follows: the rigid linear C–B–C units tilt with respect to the c direction easily, and the corner-sharing Al5C bipyramid slabs simultaneously slide along the basal plane with low resistance. The proposed deformation mode may be universal for the ternary metal borocarbides family containing short linear C–B–C units.
Impedance of nanometer sized silicon structures
Authors: Conte G. , Feliciangeli M. C. , Rossi M. C.
Published: July 2006

Laser treatment of amorphous silicon oxide films resulted in the formation of nanocrystalline silicon grains connected along the laser treated trace. The ac response has been analyzed at different temperatures in a wide frequency range. The real admittance probed along the laser trace showed decreasing values after an initial constant conductance when the frequency is increased; this trend is reminiscent of an inductive behavior. Therefore, the whole impedance figure addressed the probed material as a Debye-like single time constant homogeneous system with the full width at half maximum corresponding to the expected 1.14 decades with evidence of resistive losses only.
ZnO homojunctions grown by cosputtering ZnO and Zn3P2 targets
Authors: Hu Guangxia , Gong Hao , Chor E. F. , Wu Ping
Published: July 2006

We have demonstrated the growth and control of the conductivity type (n or p) of ZnO doped with phosphorus (P). The success of p-type and n-type P-doped ZnO is confirmed by Hall effect measurements, Seebeck measurements, and the realization of p-n homojunctions. The room temperature carrier concentration, mobility, and resistivity of the as-deposited p-type P-doped ZnO are 2.8×1017cm−3, 0.341cm2∕Vs, and 65.4Ωcm, respectively. The P-doped ZnO p-n homojunctions have a turn-on voltage of about 3.4V. Photoluminescence spectra show that the P-doped films may have a shallow accepter energy level.
Strongly enhanced nitriding kinetics by means of grain refinement
Authors: Tong W. P. , He C. S. , He J. C. , Zuo L. , Tao N. R. , Wang Z. B.
Published: July 2006

By means of surface mechanical attrition treatment (SMAT), a nanostructured surface layer was formed on a pure Fe plate. Low-temperature gaseous nitriding of the SMAT Fe sample was investigated in comparison with the coarse-grained sample. It was found that the nitriding kinetics of nanostructured α-Fe was obviously enhanced, and the temperature to form nitrides from the nanostructured α-Fe was greatly reduced with respect to that of the coarse-grained form. The effective activation energy for diffusion of nitrogen in nanocrystalline nitride layer was calculated from the temperature dependence of compound layer thickness, the obtained value being about 54.39kJ∕mol, evidently smaller than that for coarse-grained ε phase (80.7kJ∕mol) and γ′ phase (88.3kJ∕mol).
Feature-size reduction of photopolymerized structures by femtosecond optical curing of SU-8
Authors: Seet Kock Khuen , Juodkazis Saulius , Jarutis Vygandas , Misawa Hiroaki
Published: July 2006

The universal scaling of a width of photopolymerized line on the exposure dose was observed in polymerization by direct laser writing using tightly focused femtosecond pulses in SU-8 resist. This scaling can be explained as the photopolymerization by a blackbody-type emission. A spectrally broad thermal emission of electrons heated up to temperatures approximately Te∼103K coincides with an IR-absorption band of SU-8 centered at the 2.9μm and had caused polymerization by a cumulative direct absorption. Three-dimensional photonic crystal templates with approximately twice reduced feature size were fabricated with stop band at the fiber communication wavelength of 1.3μm.
Storage-ring-based, ultrashort positron beam source
Authors: Li Yuelin , Guo Weiming , Harkay Katherine , Liu Wanming
Published: July 2006

We propose a scheme to generate high-flux, short-burst γ-ray radiation and its application for generating ultrashort positron beams. The intense γ-ray bursts are generated from short laser pulses scattering off high-energy electron beams in a storage ring. The γ-ray bursts are then used to irradiate thin metal targets to generate the positron beams via pair production. Using the example of the Advanced Photon Source storage ring, more than 107positrons∕s in 1ps pulses at energies of a few MeV can be generated.
Atomic force microscopy and x-ray photoelectron spectroscopy studies of ZnO nanoparticles on SiO2 fabricated by ion implantation and thermal oxidation
Authors: Amekura H. , Plaksin O. A. , Yoshitake M. , Takeda Y. , Kishimoto N. , Buchal Ch.
Published: July 2006

The morphology and chemical composition of the surface of SiO2 that had been implanted with Zn ions of 60keV and annealed in two different atmospheres, i.e., oxygen gas and a vacuum, were compared. In the as-implanted state, the surface mainly consisted of SiO2 with low roughness due to radiation-induced smoothing. A large number of domelike structures of ZnO appeared on the surface of the SiO2 after annealing in oxygen gas at 600°C for 1h, and the size increased with the annealing temperature up to 800°C. After annealing at 900°C, the surface roughness steeply decreased and the composition changed to Zn2SiO4.
Interface charge compensation in InP based heterojunction bipolar transistors with implanted subcollectors
Authors: Parthasarathy Navin , Kadow Christoph , Griffith Zach , Rodwell Mark J. W. , Urteaga Miguel , Shinohara Keisuke , Pierson Richard , Brar Bobby
Published: July 2006

We report InP∕In0.53Ga0.47As∕InP double heterojunction bipolar transistors (DHBTs) with implanted subcollectors. We demonstrate the compensation of charge at the regrowth interface by the use of a blanket Fe implant. An isolated N++ subcollector is then formed by a patterned Si implant. With the compensation of the interface charge, this patterned subcollector eliminates the extrinsic base-collector capacitance Ccb associated with the base interconnect pad over the entire range of bias voltages. These implanted subcollector DHBTs with the shallow Fe implant have 363GHz fτ and 410GHz fmax. The dc current gain β∼40, BVceo=4.9V, BVcbo=5.4V, and Icbo<70pA at Vcb=0.3V.
Local silicon-gate carbon nanotube field effect transistors using silicon-on-insulator technology
Authors: Zhang Min , Chan Philip C. H. , Chai Yang , Liang Qi , Tang Z. K.
Published: July 2006

A local silicon-gate carbon nanotube field effect transistor (CNFET) configuration has been proposed and implemented for integration purpose. By combining the advantages of in situ carbon nanotube growth technology and the silicon-on-insulator technology, we have realized the CNFETs with individual device operation, low parasitic capacitance, high yield fabrication, and better compatibility to the complementary-metal-oxide-semiconductor (CMOS) process. The CNFETs show up-to-date electrical performance. The scaling effect of gate oxide is also explored. This configuration makes CNFET a step closer to the CMOS integrated circuit application.
Strong broad C-band room-temperature photoluminescence in amorphous Er2O3 film
Authors: Grishin A. M. , Vanin E. V. , Tarasenko O. V. , Khartsev S. I. , Johansson P.
Published: July 2006

Photoluminescence with the bandwidth of 45nm (1523–1568nm at the level of 3dB) was observed in amorphous Er2O3 films grown on quartz substrate by pulsed laser ablation of erbium oxide stoichiometric target. Optical transmission spectrum has been fitted to Swanepoel formula [J. Phys. E 16, 1214 (1983)] to determine dispersion of refractive index and to extract resonance absorption peaks at 980 and 1535nm. The maximum gain coefficient as high as 800dB∕cm at 1535nm was estimated using McCumber theory and experimental spectrum of the resonance absorption. For 5mm long waveguide amplifier with erbium doping confinement factor of 0.1, the theory predicts the spectral gain of 18dB with 1.2dB peak-to-peak flatness in the bandwidth of 31nm (1532–1563nm) when 73% of Er3+ ions are excited from the ground state to the I13∕24 laser level. Strong broadband photoluminescence at room temperature and inherently flat spectral gain promise Er2O3 films for ultrashort high-gain optical waveguide amplifiers and integrated light circuits.
Defect states in the high-dielectric-constant gate oxide LaAlO3
Authors: Xiong K. , Robertson J. , Clark S. J.
Published: July 2006

We present calculations of the energy levels of the oxygen vacancy, AlLa antisite, and oxygen interstitial defects in LaAlO3 using density functional methods that do not need an empirical band gap correction. The levels are aligned to those of the Si channel using the known band offsets. The oxygen vacancy gives an energy level near the LaAlO3 conduction band and above the Si gap. It is identified as the main electron trap and the cause of instability. The AlLa antisite gives a state near midgap, neutral when empty, which would be an important trap, with no counterpart in HfO2.
Permittivity of a ferroelectric film beneath a metal electrode
Authors: Bayer Christian , Jackson Timothy J.
Published: July 2006

The permittivity of a ferroelectric n-type semiconductor varies smoothly with depth beneath a reversed biased Schottky contact. In partially depleted films, the depletion layer controls the capacitance. In fully depleted films the inverse capacitance is proportional to the thickness, which suggests that Schottky effects do not cause dead-layer behavior.
Correlation between reliability of thermal oxides and dislocations in n-type 4H-SiC epitaxial wafers
Authors: Senzaki Junji , Kojima Kazutoshi , Kato Tomohisa , Shimozato Atsushi , Fukuda Kenji
Published: July 2006

The correlation between thermal oxide reliability and dislocations in n-type 4H-SiC (0001) epitaxial wafers has been investigated. The thermal oxides were grown by dry oxidation at 1200°C followed by nitrogen postoxidation annealing. Charge-to-breakdown values of thermal oxides decrease with an increase in the number of the dislocations in a gate-oxide-forming area. Two types of dielectric breakdown modes, edge breakdown and dislocation-related breakdown, were confirmed by Nomarski microscopy. In addition, it is revealed that basal plane dislocation is the most common cause of the dislocation-related breakdown mode.
A form of motor cortical plasticity that correlates with recovery of function after brain injury
Authors: Ramanathan Dhakshin , Conner James M. , H. Tuszynski Mark
Published: July 2006

To investigate functional mechanisms underlying cortical motor plasticity in the intact and injured brain, we used “behaviorally relevant,” long-duration intracortical microstimulation. We now report the existence of complex, multijoint movements revealed with a 500-msec duration intracortical stimulation in rat motor cortex. A consistent topographic distribution of these complex motor patterns is present across the motor cortex in naïve rats. We further document the plasticity of these complex movement patterns after focal cortical injury, with a significant expansion of specific complex movement representations in response to rehabilitative training after injury. Notably, the degree of functional recovery attained after cortical injury and rehabilitation correlates significantly with a specific feature of map reorganization, the ability to reexpress movement patterns disrupted by the initial injury. This evidence suggests the existence of complex movement representations in the rat motor cortex that exhibit plasticity after injury and rehabilitation, serving as a relevant predictor of functional recovery.
Molecular evidence for deep evolutionary roots of bilaterality in animal development
Authors: Matus David Q. , Pang Kevin , Marlow Heather , Dunn Casey W. , Thomsen Gerald H. , Martindale Mark Q.
Published: July 2006

Nearly all metazoans show signs of bilaterality, yet it is believed the bilaterians arose from radially symmetric forms hundreds of millions of years ago. Cnidarians (corals, sea anemones, and “jellyfish”) diverged from other animals before the radiation of the Bilateria. They are diploblastic and are often characterized as being radially symmetrical around their longitudinal (oral–aboral) axis. We have studied the deployment of orthologs of a number of family members of developmental regulatory genes that are expressed asymmetrically during bilaterian embryogenesis from the sea anemone,
Nematostella vectensis
. The secreted TGF-β genes
Nv-dpp
,
Nv-BMP5–8
, six TGF-β antagonists (
NvChordin
,
NvNoggin1
,
NvNoggin2
,
NvGremlin
,
NvFollistatin
, and
NvFollistatin-like
), the homeodomain proteins
NvGoosecoid
(
NvGsc
) and
NvGbx
, and the secreted guidance factor,
NvNetrin
, were studied.
NvDpp
,
NvChordin
,
NvNoggin1
,
NvGsc
, and
NvNetrin
are expressed asymmetrically along the axis perpendicular to the oral–aboral axis, the directive axis. Furthermore,
NvGbx
, and
NvChordin
are expressed in restricted domains on the left and right sides of the body, suggesting that the directive axis is homologous with the bilaterian dorsal–ventral axis. The asymmetric expression of
NvNoggin1
and
NvGsc
appear to be maintained by the canonical
Wnt
signaling pathway. The asymmetric expression of
NvNoggin1
,
NvNetrin
, and
Hox
orthologs
NvAnthox7
,
NvAnthox8
,
NvAnthox1a
, and
NvAnthox6
, in conjunction with the observation that
NvNoggin1
is able to induce a secondary axis in
Xenopus
embryos argues that
N. vectensis
could possess antecedents of the organization of the bilaterian central nervous system.
Real-time metabolic imaging
Authors: Golman Klaes , in ‘t Zandt René , Thaning Mikkel
Published: July 2006

The endogenous substance pyruvate is of major importance to maintain energy homeostasis in the cells and provides a window to several important metabolic processes essential to cell survival. Cell viability is therefore reflected in the metabolism of pyruvate. NMR spectroscopy has until now been the only noninvasive method to gain insight into the fate of pyruvate in the body, but the low NMR sensitivity even at high field strength has only allowed information about steady-state conditions. The medically relevant information about the distribution, localization, and metabolic rate of the substance during the first minute after the injection has not been obtainable. Use of a hyperpolarization technique has enabled 10–15% polarization of
13
C
1
in up to a 0.3 M pyruvate solution. i.v. injection of the solution into rats and pigs allows imaging of the distribution of pyruvate and mapping of its major metabolites lactate and alanine within a time frame of ≈10 s. Real-time molecular imaging with MRI has become a reality.
The role of procalcitonin as a predictor of nosocomial sepsis in preterm infants
Authors: TURNER DAN , HAMMERMAN CATHY , RUDENSKY BERNARD , SCHLESINGER YECHIEL , SCHIMMEL MICHAEL S.
Published: July 2006

Aim: To assess the role of procalcitonin in detecting nosocomial sepsis in preterm infants, after the onset of clinical symptoms. Subjects: 100 preterm infants, 24–36 wk of gestation, were followed from the age of 3 d until discharge. Procalcitonin and C‐reactive protein (CRP) levels were measured within 3 d of sepsis workup events. Results: 141 blood samples were drawn from 36 infants during 85 episodes of sepsis workup performed between 4 and 66 d of life. Of these episodes, 51 (60%) were not a result of documented sepsis and thereby served as the negative comparison group. Median procalcitonin levels were higher in the septic group compared with the non‐septic group at the time of the sepsis workup (2.7 vs 0.5 ng/ml, p=0.003), at 1–24 h after the sepsis workup (4.6 vs 0.6 ng/ml, p=0.003), and at 25–48 h (6.9 vs 2.0 ng/ml, p=0.016). Using high cutoff levels, both procalcitonin (2.3 ng/ml) and CRP (30 mg/l) had high specificity and positive predictive value (97%, 91% and 96%, 87%, respectively) but low sensitivity (48% and 41%, respectively) to detect sepsis. Areas under the ROC curve for procalcitonin and CRP were 0.74 and 0.73, respectively.

Conclusion: Procalcitonin >2.3 ng/ml or CRP >30 μg/l indicates a high likelihood for neonatal sepsis, and antibiotic therapy should be continued even in the presence of sterile cultures.
Rooming‐in for preterm infants: How far should we go? Five‐year experience at a tertiary hospital
Authors: DE CARVALHO GUERRA ABECASIS FRANCISCO , GOMES ANTÓNIO
Published: July 2006

Aim: To determine the rate of rooming‐in among preterm infants born in a tertiary hospital. Methods: We reviewed the records of all preterm infants born at our hospital during a 5‐y period, 2000 to 2004. Results: Of the 18953 neonates born at our institution during this time, 1356 (7.2%) were <37 wk gestational age. Considering only preterm infants with birthweight 1500 g, 806 (74.1%) stayed with their mothers and 282 (25.9%) were admitted to the NICU. Of all the preterm infants that initially stayed with their mothers, 42 (5.2%) needed to be transferred to the NICU. When we stratified these preterm infants according to birthweight, we found that 29% of those <1750 g were transferred to the NICU, compared to only 5% of those 1750 g.

Conclusion: Our study supports the idea that the majority of preterm infants, especially those with birthweight <1750 g, can safely remain near their mothers at all times during hospital stay, with both clinical and financial benefits. Neonates with birthweight <1750 g should be evaluated carefully to decide whether rooming‐in is the best option. Rooming‐in should be encouraged in preterm infants.
Patent ductus arteriosus in extremely preterm infants receiving phototherapy: Does shielding the chest make a difference? A randomized, controlled trial
Authors: Travadi Javeed , Simmer Karen , Ramsay James , Doherty Dorota , Hagan Ronald
Published: July 2006

Background: Patent ductus arteriosus (PDA), a common complication in extremely preterm infants, is associated with increased mortality and morbidity. Phototherapy has been associated with PDA, and one randomized, control trial has shown that shielding of the chest may decrease the risk of PDA. Aim: To examine if chest shielding reduces the incidence and severity of PDA in extremely preterm infants. Study design: Randomized clinical trial of infants < 29 wk gestation (stratified into two groups: <27 wk gestation and 27–28 wk gestation). Methods: Following written parental consent, eligible infants were randomized to receive phototherapy, with or without a chest shield. Ductal parameters were assessed by Doppler echocardiogram in all infants prior to starting phototherapy and at 48 h after initiation, or earlier if phototherapy was discontinued. Results: 54 infants were enrolled in the study. The incidence of PDA (shield 19/27 vs no shield 21/27), ductal size (1.4 vs 1.0 mm) and left atrial/aortic root (LA/Ao) ratio (1.2 vs 1.3) were similar in the two groups pre‐phototherapy. There was no difference between the groups post‐phototherapy in incidence (shield 12/27 vs no shield 13/27), ductal size (1.4 vs 1.5 mm) or LA/Ao ratio (1.1 vs 1.3).

Conclusion: Chest shielding did not alter the incidence or severity of PDA in our population of extremely preterm infants.
Autoantibodies linked to autoimmune polyendocrine syndrome type I are prevalent in Down syndrome
Authors: SÖDERBERGH ANNIKA , GUSTAFSSON JAN , EKWALL OLOV , HALLGREN ÅSA , NILSSON TOMAS , KÄMPE OLLE , RORSMAN FREDRIK , ANNERÉN GÖRAN
Published: July 2006

Background: Patients with Down syndrome are prone to autoimmune diseases which also occur in the recessive disease autoimmune polyendocrine syndrome type I (APS I). Since this disease is caused by mutations in the gene AIRE on chromosome 21, one might speculate that altered expression of AIRE contributes to autoimmune disease in Down syndrome. Aim: To study the prevalence of 11 well‐defined autoantibodies, five of which are specific for APS I, associated with various manifestations of APS I in patients with Down syndrome. Methods: Sera from 48 patients with Down syndrome were analysed. Autoantibodies against 21‐hydroxylase, 17α‐hydroxylase, side‐chain cleavage enzyme, aromatic L‐amino acid decarboxylase, cytochrome P4501A2, tyrosine hydroxylase, tryptophan hydroxylase, glutamic acid decarboxylase 65, tyrosine phosphatase IA‐2 and transglutaminase were analysed using an immunoprecipitation assay, and thyroid peroxidase autoantibodies were measured using a haemagglutination assay. Results: Seven of 48 patients had elevated titres of autoantibodies: one against 21‐hydroxylase, three against aromatic L‐amino acid decarboxylase, one against cytochrome P4501A2, one against glutamic acid decarboxylase 65 and one against tyrosine phosphatase IA‐2. None of the patients had clinical or laboratory signs of disease coupled to the respective autoantibody.

Conclusion: Four patients with Down syndrome had autoantibodies hitherto regarded as unique for APS I, which may suggest a dysregulation of AIRE.
Maternal cigarette smoking and breastfeeding duration
Authors: Giglia Roslyn , Binns Colin W. , Alfonso Helman
Published: July 2006

Aim: To examine the relationship between cigarette smoking and breastfeeding duration at 2 wk, 6 mo, and longer. Methods: Design. A 12‐mo longitudinal study. Setting. Two public maternity hospitals in the Perth metropolitan area (Western Australia). Subjects. Eligible mothers of healthy newborn infants. Interventions. Participants completed a self‐administered baseline questionnaire while in hospital or shortly after discharge. All women regardless of their chosen infant feeding method were followed up by telephone interview at 4, 10, 16, 22, 32, 40 and 52 wk postpartum. Main outcome measures. Prevalence of breastfeeding at 2 wk, 2 wk to 6 mo and >6 mo in women who smoked during pregnancy, and breastfeeding duration. Results: Women who smoked during pregnancy had a lower prevalence and shorter duration of breastfeeding than non‐smoking mothers (28 vs 11 wk, 95% CI 8.3–13.7). This effect remained even after adjustment for age, education, income, father's smoking status, mother's country of birth, intended duration of breastfeeding >6 mo and birthweight (risk ratio 1.59, 95% CI 1.22–2.08).

Conclusion: Women who smoke during pregnancy are at greater risk of not achieving national and international targets for breastfeeding. Encouraging smoking cessation in the antenatal setting is an area for considerable public health gain.
The impact of continuous subcutaneous insulin infusion on health‐related quality of life in children and adolescents with type 1 diabetes
Authors: Júlíusson Pétur Benedikt , Graue Marit , Wentzel‐Larsen Tore , Søvik Oddmund
Published: July 2006

Aim: To study the impact of continuous subcutaneous insulin infusion (CSII) therapy on health‐related quality of life in children and adolescents with type 1 diabetes. Methods: 31 children and adolescents with poorly regulated type 1 diabetes (mean HbA1c 10.4%, SD 1.8), mean age 14.4 (1.5) y (range 9.7–17.1) and mean diabetes duration of 6.8 (3.2) y (range 1.3–14.6) were consecutively assigned to CSII therapy. Data for generic (CHQ‐CF87) and diabetes‐specific quality of life (DQOL) were obtained before initiating pump therapy and twice during 15 mo of treatment. HbA1c, BMI and episodes of severe hypoglycaemia and ketoacidosis were recorded over 15 mo prior to and 15 mo during pump therapy. Results: Analysis showed improvements on the family activity scale (p=0.041) and change in health score (p=0.042) (CHQ‐CF87). Mean HbA1c decreased from 10.4% (1.8) to 9.0% (0.9) after 3 mo, increasing to 9.6% (1.2) after 15 mo. The number of overweight and obese children increased from 4 and 2 before CSII, to 6 and 3 after 15 mo (IOTF criteria). There was a reduction in severe hypoglycaemia episodes from 43.8 to 5.2 per 100 patient years, but no change in ketoacidosis episodes.

Conclusion: The degree of limitation experienced by families due to adolescents’ general health and well‐being was significantly reduced. Expected improvement in metabolic control and frequency of severe hypoglycaemia was observed.
Subclinical hyperthyroidism due to a thyrotropin receptor (TSHR) gene mutation (S505R)
Authors: POHLENZ JOACHIM , PFARR NICOLE , KRÜGER SILVIA , HESSE VOLKER
Published: July 2006

Aim: To identify the molecular defect by which non‐autoimmune subclinical hyperthyroidism was caused in a 6‐mo‐old infant who presented with weight loss. Methods: Congenital non‐autoimmune hyperthyroidism is caused by activating germline mutations in the thyrotropin receptor (TSHR) gene. Therefore, the TSHR gene was sequenced directly from the patient's genomic DNA. Results: Molecular analysis revealed a heterozygous point mutation (S505R) in the TSHR gene as the underlying defect.

Conclusion: A constitutively activating mutation in the TSHR gene has to be considered not only in patients with severe congenital non‐autoimmune hyperthyroidism, but also in children with subclinical non‐autoimmune hyperthyroidism.
Preterm birth in Sweden: What are the average lengths of hospital stay and the associated inpatient costs?
Authors: RINGBORG ANNA , BERG JENNY , NORMAN MIKAEL , WESTGREN MAGNUS , JÖNSSON BENGT
Published: July 2006

Aim: To provide estimates of the first‐year length of stay and inpatient costs of Swedish infants admitted for neonatal care by week of gestation and by birthweight; and to provide estimates of the length of stay and inpatient costs of delivering mothers during the ante‐ and postpartum period by week of gestation and birthweight of the infant. Methods: Population‐based registry study covering all live singleton deliveries in Sweden between 1998 and 2001 (n=336 136). First‐year hospitalizations of infants admitted for neonatal care 0–6 d after birth (n=24 583) were tracked, as were hospitalizations of mothers for whom the date of admission lay±1 mo from the date of delivery. Monetary values were assigned to each hospitalization using the Nord‐DRG classification system. Results: On average, preterm infants (GA<37 wk) had first‐year lengths of stay roughly four times as long as full‐term infants admitted for neonatal care (30 d vs 8 d, p<0.0001). The average first‐year length of stay of the extremely immature infants (GA 22–25 wk) was more than six times as long that of infants born at 34–36 wk (108 d vs 17 d, p<0.0001). Mothers delivering preterm had an average length of stay slightly more than twice as long (p<0.0001) as that of mothers of full‐term infants during the ante‐ and postpartum period.

Conclusion: The estimated lengths of stay and costs may serve as reference values for a Swedish setting.
A diary approach to analysing young adults' drinking events and motivations
Authors: WILKS JEFFREY , CALLAN VICTOR J.
Published: July 2006

Completing a diary over two weeks, 201 young adults recorded each of their drinking events, and information about the context and their motivations for alcohol use. Males reported almost twice as many drinking events and three times the number of drinks over the two‐week period. At the same time, males and females mostly drank from Wednesdays to Sundays, with the majority of beer, wine and spirit consumption being between 4 p.m. and midnight. Most drinking occurred in mixed‐sex peer groups, and the next greatest in family gatherings. Males mostly drank beer, while females chose either wine or spirits. Most drinking was in bars or at home. Males tended to drink for a wider range of reasons. The advantages of using prospective diaries in studies of young adults' alcohol use are discussed.
Alcohol consumption patterns of women in Perth, Western Australia
Authors: CORTI BILLIE , BLAZE‐TEMPLE DEBRA , HOWAT PETER , BINNS COLIN , RADALJ TONY
Published: July 2006

A survey of women aged 18–64 living in Perth in February 1987 showed that a prospective alcohol consumption diary measured a higher level of consumption (9.3%) than did a retrospective alcohol consumption diary. According to the National Health and Medical Research Council (NH) guidelines for safe and responsible drinking, 11.2% of women drank alcohol at hazardous levels (14 + drinks per week). Although on an overall weekly basis there was no significant association between age and consumption level, drinking patterns varied on a daily basis according to age. The current study may provide a conservative estimate of the percentage of women at risk. The reasons for this underestimation and the implications are discussed, together with the need to develop health promotion messages based on drinking patterns.
Consumption and advertising of alcoholic beverages in Australia, 1969‐86
Authors: SMITH D. IAN
Published: July 2006

The objective of the study was to examine the relationship between alcohol consumption per adult (≥15 years old) and expenditure on alcohol advertising per adult in Australia for the 18 years from 1969 to 1986. In addition, analyses were made of the extent to which annual changes in consumption were related to annual changes in advertising. The results showed that at the macro or aggregate level, alcohol advertising appeared to have little or no effect on alcohol consumption. By contrast, the level of consumption was positively related to the level of advertising 42 months later. In the very short term, an increase in consumption was followed by a decrease in advertising, and vice versa. The Australian results were found to be consistent with a large number of overseas studies which failed to find that alcohol advertising increased total consumption, although the advertising may have affected brand and beverage preferences. Attention is drawn to a number of methodological issues relevant to the study, and in particular the need for evaluation studies of specific advertising campaigns.