bluuebunny/crossref_metadata_2025 huggingface dataset:
Absence of ductus venosus—importance of umbilical venous drainage site
Authors: Berg C. , Kamil D. , Geipel A. , Kohl T. , Knöpfle G. , Hansmann M. , Gembruch U.
Published: July 2006

Objective

To evaluate the conditions associated with absent ductus venosus (ADV) diagnosed by prenatal ultrasonography.

Methods

Retrospective review of 23 cases with ADV diagnosed in two tertiary referral centers with a general screening policy concerning Doppler assessment of the ductus venosus. The results are discussed together with 63 cases from a review of the literature.

Results

In 19 fetuses the umbilical vein connected to the portal sinus, while the remaining four fetuses had extrahepatic umbilical venous drainage. Associated anomalies were present in 15 out of 23 fetuses: complex malformation syndromes (n = 6), chromosomal anomalies (n = 4), isolated cardiac defects (n = 4) and isolated extracardiac anomalies (n = 1). Eight fetuses had either no associated anomalies or minor anomalies. Hydropic changes were present in 12 of the 23 fetuses. In common with the reviewed cases, the presence of cardiac malformations, complex non‐chromosomal malformation syndromes and hydrops was significantly associated with intrauterine or postnatal death while the type of umbilical venous drainage was not significantly different between survivors and non‐survivors. However, among fetuses with no or minor associated anomalies the outcome was significantly better in the group without liver bypass.

Conclusions

ADV is significantly associated with fetal cardiac and extracardiac anomalies, aneuploidies and hydrops. Fetuses with liver bypass have an additional risk of developing congestive heart failure that significantly affects outcome, even if the fetal cardiovascular anatomy is otherwise normal. ADV without liver bypass seems to have a more favorable prognosis if it is not associated with other malformations. Copyright © 2006 ISUOG. Published by John Wiley & Sons, Ltd.
Lesch–Nyhan disease in a 20‐year‐ old man incorrectly described as developing ‘cerebral palsy’ after general anaesthesia in infancy
Authors: Chiong M. A. , Marinaki A. , Duley J. , Bennetts B. , Ouvrier R. , Christodoulou J.
Published: July 2006

Lesch–Nyhan disease (LND) is a rare X‐linked recessive genetic disorder caused by a deficiency of hypoxanthine‐guanine phosphoribosyltransferase (HPRT) enzyme. The classic clinical condition is characterized by cognitive impairment, hypotonia at rest, choreoathetosis, hyperuricaemia and the hallmark symptom of severe and involuntary self‐mutilation. We describe a man with LND who was initially thought to have suffered from a dyskinetic cerebral palsy after an uncomplicated inguinal herniorrhaphy under general anaesthesia at 5 1/2 months of age. In the absence of overt self‐injurious behaviour, the diagnosis was not considered for nearly two decades. The diagnosis of LND was established at 20 years of age through clinical review, biochemical examinations and molecular analysis. HPRT haemolysate activity was 7.6% of the normal control, suggesting that he had a milder variant of the disease. Mutation analysis of the HPRT gene revealed a novel missense mutation, c.449T > G in exon 6 (p.V150G). Cascade testing of family members revealed that the mother was heterozygous for the mutation but two siblings (a brother and a sister) did not carry the sequence mutation. Whether the onset of neurological abnormalities in this particular case can be attributed to the general anaesthesia is discussed.
Organization theory and supply chain management: An evolving research perspective
Authors: Miles Raymond E. , Snow Charles C.
Published: July 2006

The supply chain is the central organizing unit in today's global industries. We describe how supply chains have evolved over the last three decades, arguing that their organizational history can be divided into three periods. In the first period, the primary focus was on how to make operations throughout the supply chain more efficient. In the second period, the focus shifted from efficiency to effectiveness as leading firms began to incorporate the ideas and expertise of their suppliers and partners into the management of the supply chain. In the current period, some firms are beginning to explore how supply chains can be extended across industries in addition to operating efficiently and effectively within industries.
The Anterior Interosseous Nerve Syndrome
Authors: SCHANTZ K. , RIEGELS-NIELSEN P.
Published: July 2006

A follow-up examination of 21 cases of anterior interosseous nerve syndrome in 20 patients is presented. In 15 patients the anterior interosseous nerve was explored, with objective signs of compression in nine. 11 of these patients showed satisfactory function and three had a tendon transfer. Five cases were not operated on. Two recovered and three had continous paralysis after more than four years. One patient had a primary tendon transfer. We conclude that exploration of the anterior interosseous nerve is the treatment of choice, and that expectant treatment can be reserved for patients with slight disability or poor general health. As recovery may take over a year, tendon transfer should be postponed until after this period in patients who do not show satisfactory recovery.
Median Nerve Compression in the Proximal Forearm as a Complication of Partial Rupture of the Distal Biceps Brachii Tendon
Authors: FOXWORTHY M. , KINNINMONTH A. W. G.
Published: July 2006

We report the case of a woman, presenting with anterior proximal forearm pain and median nerve compression, who was found to have a partial tear of her distal biceps brachii tendon associated with a synovial bursa.
Elbow Flexorplasty: A Comparison between Latissimus Dorsi Transfer and Steindler Flexorplasty
Authors: EGGERS I. M. , MENNEN U. , MATIME A. M.
Published: July 2006

The latissimus dorsi transfer and the Steindler flexorplasty were compared to restore elbow flexion in seven cases. All patients had sustained upper trunk brachial plexus injuries and were adults of productive age. Both operations were successful. The results showed that the latissimus dorsi transfer provides more powerful elbow flexion and a greater range of movement one year post-operatively. The criteria for selection of candidates for both operations are set out.
The Role of an Adhesive (Histoacryl) in Tendon Repair
Authors: TRAIL I. A. , POWELL E. S. , NOBLE J. , CRANK S.
Published: July 2006

Two in vitro experiments have been done comparing various techniques of tendon repair. These include repairs using an adhesive, 2-butyl cyanoacrylate (Histoacryl), and repairs by the modified Kessler technique, using 4/0 braided polyester and 4/0 stainless steel. Mechanical analysis has shown that by replacing the circumferential suture of a modified Kessler tendon repair with Histoacryl, the tensile strength of the repair and the force needed to produce a gap can be increased by 30% to 40%. This improvement was statistically significant ( P < 0.05).
Healing of Canine Tendon in Zones Subjected to Different Mechanical Forces
Authors: NESSLER J. P. , AMADIO P. C. , BERGLUND L. J. , AN K.-N.
Published: July 2006

The effect of external force environment on the healing of a partial thickness injury to canine flexor tendon was studied. A 50% laceration was made in either the fibrocartilaginous (compressive) zone or in the tendinous (tensile) zone of canine flexor digitorum profundus tendons. After three or six weeks, the tendons were harvested. An optical method for determining zone-specific material properties showed that, in response to injury, the structural stiffness decreased in the tensile zone of the tendon but increased in the compressive zone. The mechanical properties and failure mechanism of canine tendon and their changes in response to injury vary according to tendon zone, and differences in the healing process in mechanically specialised zones of the flexor tendon are discussed.
Arthroplasty of the Proximal Interphalangeal Joint Using Costal Cartilage Grafts
Authors: HASEGAWA T. , YAMANO Y.
Published: July 2006

Seven intra-articular fractures in five patients with partial bone loss at the PIP joint were reconstructed using a graft of costal cartilage. In all cases there were total or partial cartilagenous defects of the proximal phalangeal side of the joint. Early treatment of two joints, using only costal cartilage grafts, resulted in bony ankylosis due to necrosis of the grafted cartilage. In five joints the grafted cartilage included osseous portions using the costo-osteochondral junction, leading to an average range of movement of 64° with satisfactory clinical results.

The technique is a useful alternative to other forms of arthroplasty or arthrodesis, and can provide satisfactory functional results when there is a partial defect of the head of the proximal phalanx.
Dorsal Fracture Subluxation of the Proximal Interphalangeal Joints Treated by Extension Block Splintage
Authors: HAMER D. W. , QUINTON D. N.
Published: July 2006

In a prospective study, 27 consecutive patients with dorsal fracture subluxation of the PIP joint were treated conservatively using an extension block splint, with good results in 70%. The percentage surface involved with the fracture varied considerably (19–77%) the average being 55%. Three patients intially managed with splintage proceeded to surgery because the splint failed to hold the joint in reduction. These patients had a less favourable outcome. We feel that all such fractures can be treated by splintage, provided that early reduction is maintained in the splint and checked by serial radiology.
Dorsal Fracture Subluxation of the Distal Interphalangeal Joint of the Finger and the Interphalangeal Joint of the Thumb Treated by Extension Block Splintage
Authors: HAMER D. W. , QUINTON D. N.
Published: July 2006

In a prospective study six patients with dorsal fracture subluxation of the IP joint of the thumb or the DIP joint of the finger were treated conservatively using an extension block splint. The fracture size varied from 22% to 47% of the articular surface of the volar base of the terminal phalanx. Good or excellent results were reported in all cases except for one, which was fair. Only one case in the study complained of any pain, and this was minimal. Conservative treatment using extension block splintage for this injury is as good as a surgical approach.
Energy transfer in Hall-MHD turbulence: cascades, backscatter, and dynamo action
Authors: MININNI PABLO D. , ALEXAKIS ALEXANDROS , POUQUET ANNICK
Published: July 2006

Scale interactions in Hall magnetohydrodynamics (MHDs) are studied using both the mean field theory derivation of transport coefficients, and direct numerical simulations in three space dimensions. In the magnetically dominated regime, the eddy resistivity is found to be negative definite, leading to large-scale instabilities. A direct cascade of the total energy is observed, although as the amplitude of the Hall effect is increased, backscatter of magnetic energy to large scales is found, a feature not present in MHD flows. The coupling between the magnetic and velocity fields is different than in the MHD case, and backscatter of energy from small-scale magnetic fields to large-scale flows is also observed. For the magnetic helicity, a strong quenching of its transfer is found. We also discuss non-helical magnetically forced Hall-MHD simulations where growth of a large-scale magnetic field is observed.
Density and temperature effects on a surface electron-acoustic wave in a semi-bounded dusty plasma of two-temperature electrons
Authors: KI DAE-HAN , JUNG YOUNG-DAE
Published: July 2006

The effects of density and temperature on a surface electron-acoustic plasma wave are investigated in a semi-bounded dusty plasma of two-temperature electrons. The dispersion relation of the surface electron-acoustic plasma wave is obtained by the plasma dielectric function with the specular reflection boundary condition. The phase velocity is found to be decreased when increasing the ratio of the temperature of hot electrons to that of cold electrons for large wave numbers. It is also found that the phase velocity increases with an increase in the ratio of the density of hot electrons to that of cold electrons and that the phase velocity of the surface electron-acoustic wave increases with an increase in the density of the dust grains.
In vitro developmental competence of pig nuclear transferred embryos: effects of GFP transfection, refrigeration, cell cycle synchronization and shapes of donor cells
Authors: Zhang Yun-Hai , Pan Deng-Ke , Sun Xiu-Zhu , Sun Guo-Jie , Liu Xiao-Hui , Wang Xiao-Bo , Tian Xing-Hua , Li Yan , Dai Yun-Ping , Li Ning
Published: July 2006

The present study was designed to evaluate the feasibility of producing pig transgenic blastocysts expressing enhanced green fluorescent protein (GFP) and to examine the effects of shape and preparation methods of donor cells on in vitro developmental ability of pig nuclear transferred embryos (NTEs). In experiment 1, the effect of GFP transfection on development of pig NTEs was evaluated. The cleavage and blastocyst rates showed no significant difference between NTEs derived from transfected and non-transfected donors. In experiment 2, the effect of different nuclear donor preparation methods on in vitro development of NTEs was examined. The cleavage rate showed no statistically significant differences among three preparation methods. The blastocyst rates of donor cells treated once at −4 °C and those of freshly digested cells were similar to each other (26.3% vs 17.9%). The lowest blastocyst rates (5.88%) were observed when cells cryopreserved at −196 °C were used as donors. In experiment 3, the effect of different cell cycle synchronization methods on the in vitro development potential of pig NTEs was evaluated. The cleavage rate of NTEs derived from cycling cells was much better than that of NTEs derived from serum-starved cells (64.4% vs 50.5%, p < 0.05), but no significant difference was observed between the the blastocyst rates of the two groups. In experiment 4, the effect of different shapes of cultured fibroblast cells on the in vitro development of pig NTEs was examined. The fusion rate for couplets derived from rough cells was poorer than that observed in couplets derived from round smooth cells (47.8% vs 76.8%, p < 0.05). However, there were no significant differences observed in the cleavage rate and blastocyst rate. In conclusion, the present study indicated that (i) refrigerated pig GFP-transfected cells could be used as donors in nuclear transfer and these NTEs could be effectively developed to blastocyst stage; (ii) serum starvation of GFP-transfected cells is not required for preimplantation development of pig NTEs; and (iii) a rough surface of GFP-transfected donor cells affects fusion rate negatively but has no influence on the cleavage rate or blastocyst rate of pig NTEs.
Effect of embryo developmental stage and culture conditions on number and quality of ovinein vitroproduced blastocysts
Authors: Garcia-Garcia R.M. , Dominguez V. , Gonzalez-Bulnes A. , Veiga-Lopez A. , Cocero M.J.
Published: July 2006

This study evaluated the final output and quality ofin vitroproduced blastocysts derived fromin vivorecovered sheep embryos cultured at various early developmental stages to blastocyst. A total of 270 embryos were recovered from the oviduct, at different days of the early luteal phase, and were classified into three different developmental stages: 2- to 4-cell (n= 93); 5- to 8-cell (n= 92) and 9- to 12-cell (n= 85). The effect of culture conditions was studied, at the same time, by randomly allocating the embryos to one of four groups: three groups of culture with fresh oviduct monolayers (2, 4 and 5 days old) and a fourth group with 2-day monolayers derived from frozen-thawed oviduct cells. Two control groups were established: first, embryos cultured in semi-defined medium (n= 29) and, second, blastocysts obtainedin vivoand cryopreserved (n= 43). Influence on blastocyst yield of embryo developmental stage at the start of culture was statistically significant (p< 0.001). Two- to four-cell embryos showed a significantly lower developmental rate (67.7%) than the 5- to 8-cell (83.6%;p< 0.001) and 9- to 12-cell groups (90.5%;p< 0.0001) and lower quality in terms of blastocyst cryotolerance (56.0 vs. 83.7%;p< 0.005). There were no detected effects relating to the age or handling of the monolayer on the embryo developmental rate, but the day of blastocyst appearance was different between embryos cultured on monolayers derived from fresh or frozen-thawed cells (p< 0.0001); the main influence was on the group of 9- to 12-cell embryos (p< 0.0001). Current results confirm the temporal sensitivities of sheep embryos toin vitroculture, regardless of the culture conditions.
Unreife bei der Geburt
Authors: Jungmann Tanja
Published: July 2006

Zusammenfassung. Mit den Überlebenschancen ist in den vergangenen 20 Jahren auch das Forschungsinteresse an den Entwicklungsmöglichkeiten sehr und extrem unreif geborener Kinder deutlich gestiegen. Dabei stellt sich die Frage nach der Häufigkeit und Schwere von Entwicklungsstörungen, ihren Frühzeichen und dem Einfluss von biologischen und psychosozialen Faktoren auf ihr Entstehen. Überblicksarbeiten beziehen sich zumeist auf die Zusammenstellung der Befunde zur allgemeinen, zur kognitiven und zur motorischen Entwicklung. Dagegen fokussiert der vorliegende Überblick erstmals die zentralen Forschungsfragen auf die Sprachentwicklung unreif geborener Kinder. Angesichts der Heterogenität der Stichproben, des methodischen Vorgehens und der Befunde, wird ihre Beantwortung durch die Extraktion des gemeinsamen Nenners versucht.
Vertical profiles of the O2/N2 ratio in the stratosphere over Japan and Antarctica
Authors: Ishidoya Shigeyuki , Sugawara Satoshi , Hashida Gen , Morimoto Shinji , Aoki Shuji , Nakazawa Takakiyo , Yamanouchi Takashi
Published: July 2006

To examine the spatial and temporal behavior of stratospheric O2, air samples were collected using a cryogenic sampler over Sanriku, Japan and Syowa, Antarctica and analyzed for δ(O2/N2), δ15N of N2 and δ18O of O2. The measured values of all these components decreased gradually with height. The differences in δ(O2/N2), δ15N and δ18O between the middle and lowermost levels of the stratosphere were about 250, 100, and 180 per meg, respectively. The observed stratospheric profiles of δ15N and δ18O were in agreement with those calculated using a steady‐state 1‐dimensional eddy‐diffusion/molecular‐diffusion model, which suggests that the upward decrease of stratospheric δ(O2/N2) is caused by a gravitational separation of O2 and N2 molecules. The averaged stratospheric δ(O2/N2) at heights above 20–25 km over Sanriku, corrected for the gravitational separation, was always higher than the upper tropospheric δ(O2/N2) value over Japan, and it decreased secularly. From the past temporal δ(O2/N2) variation deduced from the gravitational separation‐corrected stratospheric δ(O2/N2) values and the mean ages of the respective air samples, which corresponds to its secular trend in the troposphere, average terrestrial biospheric and oceanic CO2 uptake for October 1993–September 2001 were estimated to be 1.1 ± 1.3 and 1.8 ± 1.3 GtC yr−1, respectively.
Transcriptional regulation of Dictyostelium pattern formation
Authors: Williams Jeffrey G
Published: July 2006

On starvation, Dictyostelium cells form a terminally differentiated structure, known as the fruiting body, which comprises stalk and spore cells. Their precursors–prestalk and prespore cells–are spatially separated and accessible in a migratory structure known as the slug. This simplicity and manipulability has made Dictyostelium attractive to both experimental and theoretical developmental biologists. However, this outward simplicity conceals a surprising degree of developmental sophistication. Multiple prestalk subtypes are formed and undertake a co‐ordinated series of morphogenetic cell movements to generate the fruiting body. This review describes recent advances in understanding the signalling pathways that generate prestalk‐cell heterogeneity, focusing on the roles of the prestalk‐cell inducer differentiation‐inducing factor‐1 (DIF‐1), the tip inducer cAMP and the transcription factors that mediate their actions; these include signal transducer and activator of transcription (STAT) proteins, basic leucine zipper (bZIP) proteins and a Myb protein of a class previously described only in plants.
Three-dimensional magnetic spin-echo small-angle neutron scattering and neutron depolarization: A comparison
Authors: Rekveldt M. Theo , van Dijk Niels H. , Grigoriev Serguei V. , Kraan Wicher H. , Bouwman Wim G.
Published: July 2006

The recently developed magnetic spin-echo small-angle neutron scattering (SANS) technique provides unique information about the distance correlation of the local vector magnetization as a function of the spin-echo length within a magnetic material. The technique probes the magnetic correlations on a length scale from 10nm up to 10μm within the bulk of a magnetic material by evaluating the Larmor precession of a polarized neutron beam in a spin-echo setup. The characteristics of the spin-echo SANS technique are discussed and compared to those of the more conventional neutron depolarization technique. Both of these techniques probe the average size of the magnetic inhomogeneities and the local magnetic texture. The magnetic spin-echo SANS technique gives information on the size distribution of these magnetic inhomogeneities perpendicular to the beam and, in principle, independent on the local magnetic induction. This information is not accessible by the neutron depolarization technique that gives the average size parallel to the beam multiplied with the square of the local magnetic induction. The basic possibilities of the magnetic spin-echo SANS technique are demonstrated by experiments on samples with a strong magnetic texture.
Formation and interaction of hydrated alkali metal ions at the graphite-water interface
Authors: Meng Sheng , Gao Shiwu
Published: July 2006

Ion hydration at a solid surface ubiquitously exists in nature and plays important roles in many natural processes and technological applications. Aiming at obtaining a microscopic insight into the formation of such systems and interactions therein, we have investigated the hydration of alkali metal ions at a prototype surface-graphite (0001), using first-principles molecular dynamics simulations. At low water coverage, the alkali metal ions form two-dimensional hydration shells accommodating at most four (Li, Na) and three (K, Rb, Cs) waters in the first shell. These two-dimensional shells generally evolve into three-dimensional structures at higher water coverage, due to the competition between hydration and ion-surface interactions. Exceptionally K was found to reside at the graphite-water interface for water coverages up to bulk water limit, where it forms an “umbrellalike” surface hydration shell with an average water-ion-surface angle of 115°. Interactions between the hydrated K and Na ions at the interface have also been studied. Water molecules seem to mediate an effective ion-ion interaction, which favors the aggregation of Na ions but prevents nucleation of K. These results agree with experimental observations in electron energy loss spectroscopy, desorption spectroscopy, and work function measurement. In addition, the sensitive dependence of charge transfer on dynamical structure evolution during the hydration process, implies the necessity to describe surface ion hydration from electronic structure calculations.
Methane-water cross second virial coefficient with quantum corrections from anab initiopotential
Authors: Akin-Ojo Omololu , Harvey Allan H. , Szalewicz Krzysztof
Published: July 2006

We present our calculations of the cross second virial coefficient (B12) and of a related quantity, ϕ12=B12−TdB12∕dT, for the methane-water system in the temperature range T=200–1000K. These calculations were performed using one of the ab initio potentials developed in previous work [Akin-Ojo and Szalewicz, J. Chem. Phys. 123, 134311 (2005)]. Quantum corrections of order ℏ2 were added to the computed classical values. We have estimated the uncertainties in our computed B12 and ϕ12(T). This allowed evaluation of the quality of the experimental data to which we compare our results. We also provide an analytical expression for B12(T) as a function of the temperature T obtained by fitting the calculated values. This formula also predicts values of ϕ12(T) consistent with the directly calculated values.
Selected configuration interaction with truncation energy error and application to the Ne atom
Authors: Bunge Carlos F.
Published: July 2006

Selected configuration interaction (SCI) for atomic and molecular electronic structure calculations is reformulated in a general framework encompassing all CI methods. The linked cluster expansion is used as an intermediate device to approximate CI coefficients BK of disconnected configurations (those that can be expressed as products of combinations of singly and doubly excited ones) in terms of CI coefficients of lower-excited configurations where each K is a linear combination of configuration-state-functions (CSFs) over all degenerate elements of K. Disconnected configurations up to sextuply excited ones are selected by Brown’s energy formula, ΔEK=(E−HKK)BK2∕(1−BK2), with BK determined from coefficients of singly and doubly excited configurations. The truncation energy error from disconnected configurations, ΔEdis, is approximated by the sum of ΔEKs of all discarded Ks. The remaining (connected) configurations are selected by thresholds based on natural orbital concepts. Given a model CI space M, a usual upper bound ES is computed by CI in a selected space S, and EM=ES+ΔEdis+δE, where δE is a residual error which can be calculated by well-defined sensitivity analyses. An SCI calculation on Ne ground state featuring 1077 orbitals is presented. Convergence to within near spectroscopic accuracy (0.5cm−1) is achieved in a model space M of 1.4×109 CSFs (1.1×1012 determinants) containing up to quadruply excited CSFs. Accurate energy contributions of quintuples and sextuples in a model space of 6.5×1012 CSFs are obtained. The impact of SCI on various orbital methods is discussed. Since ΔEdis can readily be calculated for very large basis sets without the need of a CI calculation, it can be used to estimate the orbital basis incompleteness error. A method for precise and efficient evaluation of ES is taken up in a companion paper.
Generation and detection of alkyl peroxy radicals in a supersonic jet expansion
Authors: Fu H. B. , Hu Y. J. , Bernstein E. R.
Published: July 2006

Alkyl peroxy radicals are synthesized in a supersonic jet expansion by the initial production of alkyl radicals and subsequent reaction with molecular oxygen. Parent ions CH3OO+∕CD3OO+ are observed employing vacuum ultraviolet (VUV) single photon ionization∕time-of-flight mass spectroscopy (TOFMS). Employing infrared (IR)+VUV photofragmentation detected spectroscopy, rotationally resolved infrared spectra of jet-cooled CH3OO and CD3OO radicals are recorded for the ÃA′2←X̃A″2 transition by scanning the IR laser frequency while monitoring the CH3+ and CD3+ ion signals generated by the VUV laser. The band origins of the ÃA′2←X̃A″2 transition for CH3OO and CD3OO are identified at 7381 and 7371cm−1, respectively. Rotational simulation for the CH3OO and CD3OO 000 transitions of Ã←X̃ yields a rotational temperature for these radicals of ∼30K. With the aid of ab initio calculations, two and five vibrational modes for the ÃA′2 excited electronic state are assigned for CH3OO and CD3OO radicals, respectively. Both experimental and theoretical results suggest that the ground electronic state of the ions of ethyl and propyl peroxy radicals are not stable although their ionization energies (IE) are less than 10.5eV. The C2H5OO+∕C3H7OO+ cations can readily decompose to C2H5+∕C3H7+ and O2. This is partially responsible for the inability of IR+VUV photofragmentation spectroscopy to detect the near IR Ã←X̃ electronic transition for these radicals.
Forms and applications of the nucleation theorem
Authors: Kashchiev Dimo
Published: July 2006

The nucleation theorem is a general relation between the nucleation work, the nucleus size, and the supersaturation or other thermodynamic parameters of the old phase. The theorem appears in different forms, depending not only on the chosen set of independent variables describing the nucleation work but also on which of these variables is changed while the others are held fixed. This paper gives a rigorous, systematic, and comprehensive presentation of various forms of the nucleation theorem and shows how some of them can be applied to concrete cases of nucleation. Both theoretical and experimental applications of the theorem to nucleation in unary, binary, or ternary phases are considered.
Assessment of protein folding potentials with an evolutionary method
Authors: de Sancho David , Rey Antonio
Published: July 2006

Many different protein folding potentials have been developed in the last decades, based upon knowledge of experimentally determined protein structures. Decoy-based techniques are frequently used to assess these force fields, but other methods can explore different features in the performance of the interaction schemes, thus helping in their evaluation. Here, we propose an evolutionary strategy to efficiently assess folding potentials. We apply it to three potentials with different characteristics, taken from the bibliography. A search for minimum energy protein topologies, treated as arrangements of rigid protein fragments, is performed. The method, applied to a set of helix bundle proteins, shows the different behavior of the studied potentials, providing a reasonably fast tool to evaluate their advantages and limitations.
Problems in the comparison of theoretical and experimental hyperpolarizabilities revisited
Authors: Reis H.
Published: July 2006

The relationship between nonlinear susceptibilities and hyperpolarizabilities defined using different conventions is reexamined. In previous work [Willetts et al., J. Chem. Phys. 97, 7590 (1992)], relations between different conventions for microscopic hyperpolarizabilities have been derived, but the application of the corresponding conversion factors led to several inconsistencies. It is shown that different conventions for macroscopic susceptibilities have to be taken into account, too, in order to arrive at consistently comparable values. The complete set of conversion factors between several conventions are given for second harmonic generation, electric field induced second harmonic (EFISH) generation, and third harmonic generation. As an illustration, experimental EFISH and hyper-Rayleigh scattering results of p-nitroaniline are compared with each other and with recent results of ab initio computations including solvation effects. Several problems in the comparison of computational and experimental values are also discussed.
A Finslerian version of ‘t Hooft deterministic quantum models
Authors: Torrome Ricardo Gallego
Published: July 2006

Using the Finsler structure living in the phase space associated to the tangent bundle of the configuration manifold, deterministic models at the Planck scale are obtained. The Hamiltonian functions are constructed directly from the geometric data and some assumptions concerning time inversion symmetry. The existence of a maximal acceleration and speed is proved for Finslerian deterministic models. We investigate the spontaneous symmetry breaking of the orthogonal symmetry SO(6N) of the Hamiltonian of a deterministic system. This symmetry break implies the nonvalidity of the argument used to obtain Bell’s inequalities for spin states. It is introduced and motivated in the context of Randers spaces, an example of a simple ’t Hooft model with interactions.
Photoluminescence from C60-coupled porous structures formed on Fe+-implanted silicon
Authors: Zhang Z. Y. , Wu X. L. , Qiu T. , Chen P. , Chu Paul K. , Siu G. G. , Tang D. L.
Published: July 2006

⟨111⟩-oriented p-type Si wafer with a resistivity of 1–5Ωcm was implanted with Fe+ and then annealed at 1100°C in N2 for 60min, followed by anodization in a solution of HF to form porous structure with β-FeSi2 nanocrystallites. Photoluminescence (PL) spectral measurements show that a strong PL peak appears in the range of 610–670nm. The position of the PL peak remains unchanged, but its intensity increases with the storage time in air until about three months and then saturates. C60 molecules were chemically coupled on the porous structure through a kind of silane coupling agent to form a nanocomposite. It is revealed that the stable PL peak monotonically shifts to a pinning wavelength at 570nm. Experimental results from PL, PL excitation, Raman scattering, and x-ray diffraction measurements clearly show that the pinned PL originates from optical transition in C60-related defect states, whereas the photoexcited carriers occur in the β-FeSi2 nanocrystallites formed during anodization. This work opens a new way to tailor nanometer environment for seeking optimal luminescent properties.
Quantum solvation dynamics of HCN in a helium-4 droplet
Authors: Mikosz Aleksandra A. , Ramilowski Jordan A. , Farrelly David
Published: July 2006

Ultracold nanodroplets of helium-4, containing several thousands of He atoms, offer considerable promise as microscopic cryogenic chambers. Potential applications include the creation of tailor-made chemical or biomolecular complexes and studies of superfluidity in nanoscale systems. Recent experiments have succeeded in interrogating droplets of quantum solvent which consist of as few as 1–20 helium-4 atoms and which contain a single solute molecule. This allows the transition from a floppy, but essentially molecular, complex to a dissolved molecule to be followed and, surprisingly, the transition is found to occur quite rapidly, in some cases for as few as N=7–20 solvent atoms. For example, in experiments on helium-4 droplets seeded with CO molecules [Tang and McKellar, J. Chem. Phys. 119, 754 (2003)], two series of transitions are observed which correlate with the a-type (ΔK=0) and b-type (ΔK=±1) lines of the binary complex, CO–He (K is the quantum number associated with the projection of the total angular momentum onto the vector connecting the atom and the molecular center of mass). The a-type series, which evolves from the end-over-end rotational motion of the CO–He binary complex, saturates to the nanodroplet limit for as few as 10–15 helium-4 atoms, i.e., the effective moment of inertia of the molecule converges to its asymptotic (solvated) value quite rapidly. In contrast, the b-type series, which evolves from the free-molecule rotational mode, disappears altogether for N≈7 atoms. Similar behavior is observed in recent computational studies of HCN(He4)N droplets [Paolini et al., J. Chem. Phys. 123, 114306 (2005)]. In this article the quantum solvation of HCN in small helium-4 droplets is studied using a new fixed-node diffusion Monte Carlo (DMC) procedure. In this approach a Born-Oppenheimer-type separation of radial and angular motions is introduced as a means of computing nodal surfaces of the many-body wave functions which are required in the fixed-node DMC method. Excited rotational energies are calculated for HCN(He4)N droplets with N=1–20: the adiabatic node approach also allows concrete physical mechanisms to be proposed for the predicted disappearance of the b-type series as well as the rapid convergence of the a-type series to the nanodroplet limit with increasing N. The behavior of the a-type series is traced directly to the mechanics of angular momentum coupling—and decoupling—between identical bosons and the molecular rotor. For very small values of N there exists significant angular momentum coupling between the molecule and the helium atoms: at N≈10 solvation appears to be complete as evidenced by significant decoupling of the molecule and solvent angular momenta. The vanishing of the b-type series is predicted to be a result of increasing He–He repulsion as the number of solvent atoms increases.
Stabilization of the cubic phase of HfO2 by Y addition in films grown by metal organic chemical vapor deposition
Authors: Rauwel E. , Dubourdieu C. , Holländer B. , Rochat N. , Ducroquet F. , Rossell M. D. , Van Tendeloo G. , Pelissier B.
Published: July 2006

Addition of yttrium in HfO2 thin films prepared on silicon by metal organic chemical vapor deposition is investigated in a wide compositional range (2.0–99.5at.%). The cubic structure of HfO2 is stabilized for 6.5at.%. The permittivity is maximum for yttrium content of 6.5–10at.%; in this range, the effective permittivity, which results from the contribution of both the cubic phase and silicate phase, is of 22. These films exhibit low leakage current density (5×10−7A∕cm2 at −1V for a 6.4nm film). The cubic phase is stable upon postdeposition high temperature annealing at 900°C under NH3.
Theory for high Q p-n junction avalanche inductors
Authors: Lee Chie-In , Pan Dee-Son
Published: July 2006

A simple theory for p-n junction inductors is presented. The theory explains the previously measured inductances of p-n junction inductors very well. It shows that the measured low quality factors of the earlier report are due to the unnecessary space charge resistances of the p-n junctions adopted in the experiment. A simple theoretical design example of high Q p-n junction inductors is shown to be readily available in silicon.
Band gap engineering and stimulated emission of ZnMgO nanowires
Authors: Hsu Hsu-Cheng , Wu Chun-Yi , Cheng Hsin-Ming , Hsieh Wen-Feng
Published: July 2006

We report a simple method for fabricating heterostructured ZnMgO nanowires by annealing the preformed ZnO∕MgO core-shell structure. Photoluminescence from the alloy nanowires shows strong near-band-edge (NBE) emission, reflecting good material quality. A blueshift of the NBE emission at room temperature after the annealing treatment is attributed to the diffusion of Mg from the shell into the core ZnO of the nanowires to form a ternary ZnMgO alloy. Band gap engineering and stimulated emissions of ZnMgO nanowires with different Mg doping concentrations are also demonstrated.
Energy-band parameters of atomic-layer-deposition Al2O3∕InGaAs heterostructure
Authors: Huang M. L. , Chang Y. C. , Chang C. H. , Lin T. D. , Kwo J. , Wu T. B. , Hong M.
Published: July 2006

The valence-band offset has been determined to be 3.83±0.05eV at the atomic-layer-deposition Al2O3∕InGaAs interface by x-ray photoelectron spectroscopy. The Au–Al2O3∕InGaAs metal-oxide-semiconductor diode exhibits current-voltage characteristics dominated by Fowler-Nordheim tunneling. From the current-voltage data at forward and reverse biases, a conduction-band offset of 1.6±0.1eV at the Al2O3–InGaAs interface and an electron effective mass ∼0.28±0.04m0 of the Al2O3 layer have been extracted. Consequently, combining the valence-band offset, the conduction-band offset, and the energy-band gap of the InGaAs, the energy-band gap of the atomic-layer-deposited Al2O3 is 6.65±0.11eV.
Low-resistance p+ layer formation into diamond using heavily B ion implantation
Authors: Tsubouchi Nobuteru , Ogura Masahiko , Horino Yuji , Okushi Hideyo
Published: July 2006

We examine the B dosage dependence of the lattice and electronic structures of a heavily B doped layer formed by multiple-energy B-implantation into diamond (up to 1.7×1017Bcm−2) at an elevated temperature. The resultant highly B doped diamond layer exhibits p-type conduction with very low sheet resistance of 90Ω∕◻ (0.25μm thickness) and low resistivity of 2.3mΩ cm and has temperature-independent transport properties. This suggests that a high-temperature ion implantation technique allows the formation of diamond as a p-type degenerate semiconductor with metallic conduction and provides a useful tool for selective doping required for practical diamond device processing.
Piezoelectricity of A3BC3D2O14 structure crystals
Authors: Chen Jianjun , Zheng Yanqing , Kong Haikuan , Shi Erwei
Published: July 2006

First-principle calculations are performed to reveal the microscopic origin of piezoelectricity of ordered crystals with A3BC3D2O14 structure. The calculated piezoelectric constant e11 and atomistic piezoelectric contribution from every single atom type in a primitive cell of Sr3NbGa3Si2O14 (SNGS), Sr3TaGa3Si2O14 (STGS), Ca3NbGa3Si2O14 (CNGS), and Ca3TaGa3Si2O14 (CTGS) structures showed that the piezoelectricity comes mostly from one of three atoms in A positions. The percentages of the contributions from the A positions to the total internal piezoelectric constant exceed 69% in CNGS and CTGS and 81% in SNGS and STGS, respectively.
Phase selective growth and properties of rhombohedral and cubic indium oxide
Authors: Wang Ch. Y. , Cimalla V. , Romanus H. , Kups Th. , Ecke G. , Stauden Th. , Ali M. , Lebedev V. , Pezoldt J. , Ambacher O.
Published: July 2006

Phase selective growth of rhombohedral and cubic indium oxide polytypes was studied. The selective growth of different polytypes was achieved by adjusting substrate temperature and trimethylindium flow rate during metal organic chemical vapor deposition on c-plane sapphire. The optical band gaps of the cubic and rhombohedral phases were determined to be ∼3.7 and ∼3.0eV, respectively. On the basis of the performed structural investigations, a phenomenological model of the nucleation and growth of highly textured cubic In2O3 on Al2O3 (0001) is proposed.
Method for analyzing the in-plane uniaxial anisotropy of soft magnetic thin film
Authors: Xue Desheng , Fan Xiaolong , Jiang Changjun
Published: July 2006

Based on the vibrating sample magnetometer, a method is proposed to comprehensively analyze the in-plane uniaxial anisotropy of magnetic thin film. It can be used to determine accurately the values of effective anisotropy magnetic field Ha, anisotropy constants K1 and K2, as well as the directions of easy and hard axes. All of them can be carried out by fitting experimental M∕Ms-θ0 curves with theoretical equations that only require one measurement. Using this method an effective anisotropy magnetic field Ha=25.3Oe and anisotropy constants K1=2.24×104erg∕cm3 and K2=−4.7×103erg∕cm3 for the Co92Zr8 thin film were derived.
Demonstration of a silicon-based quantum cellular automata cell
Authors: Mitic M. , Cassidy M. C. , Petersson K. D. , Starrett R. P. , Gauja E. , Brenner R. , Clark R. G. , Dzurak A. S. , Yang C. , Jamieson D. N.
Published: July 2006

We report on the demonstration of a silicon-based quantum cellular automata (QCA) unit cell incorporating two pairs of metallically doped (n+) phosphorus-implanted nanoscale dots, separated from source and drain reservoirs by nominally undoped tunnel barriers. Metallic cell control gates, together with Al–AlOx single electron transistors for noninvasive cell-state readout, are located on the device surface and capacitively coupled to the buried QCA cell. Operation at subkelvin temperatures was demonstrated by switching of a single electron between output dots, induced by a driven single electron transfer in the input dots. The stability limits of the QCA cell operation were also determined.
SiC nanowires: A photocatalytic nanomaterial
Authors: Zhou Weimin , Yan Lijun , Wang Ying , Zhang Yafei
Published: July 2006

Single-crystal β-SiC nanowires coated with amorphous SiO2 were synthesized by a simple thermal evaporation technique. The photocatalytic activity of the SiC nanowires was characterized by measuring the photodegradation rate of acetaldehyde catalyzed by SiC as a function of UV irradiation time. It exhibited excellent photocatalytic activity, leading to the efficient decomposition of acetaldehyde by irradiation with UV light. The progress of the photocatalytic reaction can be monitored by the evolution of one of the products, CO2. It has been observed that the as-synthesized SiC nanowires (with the SiO2 coating) have higher catalytic activity than the HF-etched, oxide-free SiC nanowires.
Bias voltage dependence of the electron spin injection studied in a three-terminal device based on a (Ga,Mn)As∕n+-GaAs Esaki diode
Authors: Kohda M. , Kita T. , Ohno Y. , Matsukura F. , Ohno H.
Published: July 2006

We investigated injection of spin polarized electrons in a (Ga,Mn)As∕n+-GaAs Esaki diode (ED) by using a three-terminal device integrating a (Ga,Mn)As ED and a light emitting diode (LED). Electroluminescence polarization (PEL) from the LED was measured under the Faraday configuration as a function of bias voltages applied independently to the Esaki diode and to the LED. The maximum PEL of 32.4% was observed when the valence electrons near the Fermi energy of (Ga,Mn)As are ballistically injected into the LED.
Influence of V/III molar ratio on the formation of In vacancies in InN grown by metal-organic vapor-phase epitaxy
Authors: Pelli A. , Saarinen K. , Tuomisto F. , Ruffenach S. , Briot O.
Published: July 2006

We have applied a slow positron beam to study InN samples grown by metal-organic vapor-phase epitaxy with different V/III molar ratios (3300–24 000) and at different growth temperatures (550–625°C). Indium vacancies were identified in samples grown at V/III ratios below 4000. Their concentration is in the 1017cm−3 range. No strong dependence of vacancy concentration on the molar ratio was observed. At low V/III ratios, however, In droplets and vacancy clusters are formed near the substrate interface. The elevated growth temperature enhances the In vacancy formation, possibly due to limited sticking of In on the growth surface close to the decomposition temperature.
Minute doping with deleterious rare earths in YBa2Cu3O7−δ films for flux pinning enhancements
Authors: Barnes P. N. , Kell J. W. , Harrison B. C. , Haugan T. J. , Varanasi C. V. , Rane M. , Ramos F.
Published: July 2006

To enhance the critical current density of YBa2Cu3O7−δ films, flux pinning centers are intentionally added to inhibit flux flow in applied magnetic fields. Here we provide an initial demonstration that the incorporation of very minor additions (⩽1% of Y as opposed to the 10%–40% in standard substitutions) of typically deleterious rare earths into high quality YBa2Cu3O7−δ thin films provides significant improvement of the film’s in-field current density. This is accomplished without reoptimization of the deposition parameters. Instead of site substitution for Y as might be expected, the deleterious rare earths potentially result in the formation of nanoparticulates.
Single-crystal silicon nanoparticles: An instability to check their synthesis
Authors: Cavarroc M. , Mikikian M. , Perrier G. , Boufendi L.
Published: July 2006

An instability occuring in electrical signals of the discharge is used as a mark to detect the end of the single-crystal silicon nanoparticle formation in Ar∕SiH4 rf plasmas. Scanning electron microscopy and atomic force microscopy studies of depositions show that the exact beginning of the coalescence phase corresponds to the onset of the instability. At the end of the instability, no single-crystal nanoparticles are remaining in the gas phase. These results based on a nonperturbative method allow to control depositions of single-crystal silicon nanoparticles of a well-defined size distribution with the highest density available during dust particle growth.
Honey produced from genetically modified canola (Brassica napus) nectar will not need to be labelled as a GM food under current Australian guidelines
Authors: Hornitzky M. , Ghalayini A.
Published: July 2006

Food or ingredients labelled as genetically modified (GM) contain either new genetic material or protein as a result of genetic modification. In Australia, a 1% threshold, below which labelling is not required, exists for the unintended presence of GM material in non-GM foods. The canola pollen content by dry weight in a range of canola honey samples from diverse geographical areas in Australia was determined to be 0.2 ± 0.12%, well below the 1% threshold. Two GM canola honey samples sourced from Canada contained 0.19 and 0.24% of canola pollen. This work indicates honey derived from GM canola crops will not need to be labelled as a GM food.