bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonlinear long waves generated by a moving pressure disturbance
Authors: Casciola C. M. , Landrini M.
Published: April 2006

The evolution of long waves generated by a pressure disturbance acting on an initially unperturbed free surface in a channel of finite depth is analysed. Both off-critical and transcritical conditions are considered in the context of the fully nonlinear inviscid problem. The solution is achieved by using an accurate boundary integral approach and a time-stepping procedure for the free-surface dynamics.

The discussion emphasizes the comparison between the present results and those provided by both the Boussinesq and the related Korteweg–de Vries model. For small amplitudes of the forcing, the predictions of the asymptotic theories are essentially confirmed. However, for finite intensities of the disturbance, several new features significantly affect the physical results. In particular, the interaction among different wave components, neglected in the Korteweg–de Vries approximation, is crucial in determining the evolution of the wave system. A substantial difference is indeed observed between the solutions of the Korteweg–de Vries equation and those of both the fully nonlinear and the Boussinesq model. For increasing dispersion and fixed nonlinearity the agreement between the Boussinesq and fully nonlinear description is lost, indicating a regime where dispersion becomes dominant.

Consistently with the long-wave modelling, the transcritical regime is characterized by an unsteady flow and a periodic emission of forward-running waves. However, also in this case, quantitative differences are observed between the three models. For larger amplitudes, wave steepening is almost invariably observed as a precursor of the localized breaking commonly detected in the experiments. The process occurs at the crests of either the trailing or the upstream-emitted wave system for Froude numbers slightly sub- and super-critical respectively.
Interaction between a spatially growing turbulent boundary layer and embedded streamwise vortices
Authors: Liu Junhui , Piomelli Ugo , Spalart Philippe R.
Published: April 2006

The interaction between a zero-pressure-gradient turbulent boundary layer and a pair of strong, common-flow-down, streamwise vortices with a sizeable velocity deficit is studied by large-eddy simulation. The subgrid-scale stresses are modelled by a localized dynamic eddy-viscosity model. The results agree well with experimental data. The vortices drastically distort the boundary layer, and produce large spanwise variations of the skin friction. The Reynolds stresses are highly three-dimensional. High levels of kinetic energy are found both in the upwash region and in the vortex core. The two secondary shear stresses are significant in the vortex region, with magnitudes comparable to the primary one. Turbulent transport from the immediate upwash region is partly responsible for the high levels of turbulent kinetic energy in the vortex core; its effect on the primary stress 〈u′v′〉 is less significant. The mean velocity gradients play an important role in the generation of 〈u′v′〉 in all regions, while they are negligible in the generation of turbulent kinetic energy in the vortex core. The pressure-strain correlations are generally of opposite sign to the production terms except in the vortex core, where they have the same sign as the production term in the budget of 〈u′v′〉. The results highlight the limitations of the eddy-viscosity assumption (in a Reynolds-averaged context) for flows of this type, as well as the excessive diffusion predicted by typical turbulence models.
Nonlinear development of flow in channels with non-parallel walls
Authors: Tutty O. R.
Published: April 2006

In Jeffery–Hamel flow, the motion of a viscous incompressible fluid between rigid plane walls, unidirectional flow is impossible if the angle between the walls exceeds a critical value of 2α2 which depends on the Reynolds number. In this paper the nonlinear development of the flow near this critical value is studied through numerical solutions of the two-dimensional Navier–-Stokes equations for flow in divergent channels with piecewise straight walls. It is found that if the angle between the walls exceeds 2α2 then Jeffery–-Hamel flow does not occur, and the solution takes the form of a large-amplitude wave with eddies attached alternately to the upper and lower walls. When viewed in the appropriate coordinate system, far downstream the wave has constant wavelength and strength, although, physically, there is a linear increase in wavelength with distance downstream, i.e. the wavelength is proportional to the channel width. If the angle between the walls is less than 2α2, then the existence (or otherwise) of the wave depends on the conditions near the inlet, in particular the local geometry of the channel. Jeffery–-Hamel flow is obtained downstream of the inlet for angles well below 2α2, but close to but below the critical value, solutions have been obtained with the wave extending (infinitely) far downstream. The wavelengths obtained numerically were compared with those from linear theory with spatially developing steady modes. No agreement was found: the wavelengths from the steady Navier–-Stokes solutions are significantly larger than that predicted by the theory. However, in other important aspects the results of this study are consistent with those from previous studies of the development/existence of Jeffery–-Hamel flow, in particular as regards the importance of the upstream conditions and the subcritical nature of the spatial development of the flow near the critical boundary in the Reynolds number–wall angle parameter space.
Turbulent structure beneath surface gravity waves sheared by the wind
Authors: Thais L. , Magnaudet J.
Published: April 2006

New experiments have been carried out in a large laboratory channel to explore the structure of turbulent motion in the water layer beneath surface gravity waves. These experiments involve pure wind waves as well as wind-ruffled mechanically generated waves. A submersible two-component LDV system has been used to obtain the three components of the instantaneous velocity field along the vertical direction at a single fetch of 26 m. The displacement of the free surface has been determined simultaneously at the same downstream location by means of wave gauges. For both types of waves, suitable separation techniques have been used to split the total fluctuating motion into an orbital contribution (i.e. a motion induced by the displacement of the surface) and a turbulent contribution. Based on these experimental results, the present paper focuses on the structure of the water turbulence. The most prominent feature revealed by the two sets of experiments is the enhancement of both the turbulent kinetic energy and its dissipation rate with respect to values found near solid walls. Spectral analysis provides clear indications that wave–turbulence interactions greatly affect energy transfers over a significant frequency range by imposing a constant timescale related to the wave-induced strain. For mechanical waves we discuss several turbulent statistics and their modulation with respect to the wave phase, showing that the turbulence we observed was deeply affected at both large and small scales by the wave motion. An analysis of the phase variability of the bursting suggests that there is a direct interaction between the waves and the underlying turbulence, mainly at the wave crests. Turbulence budgets show that production essentially takes place in the wavy region of the flow, i.e. above the wave troughs. These results are finally used to address the nature of the basic mechanisms governing wave–turbulence interactions.
Laminar flow in rotating curved pipes
Authors: Ishigaki Hiroshi
Published: April 2006

When a curved pipe rotates about the centre of curvature, the fluid flowing in it is subjected to both Coriolis and centrifugal forces. Based on the analogy between laminar flows in stationary curved pipes and in orthogonally rotating pipes, the flow characteristics of fully developed laminar flow in rotating curved pipes are made clear and definite by similarity arguments, computational studies and using experimental data. Similarity arguments clarify that the flow characteristics in loosely coiled rotating pipes are governed by three parameters: the Dean number KLC, a body force ratio F and the Rossby number Ro. As the effect of Ro is negligible when Ro is large, computational results are presented for this case first, and then the effect of Ro is studied. Flow structure and friction factor are studied in detail. Variations of flow structure show secondary flow reversal at F ≈ −1, where the two body forces are of the same order but in opposite directions. It is also shown how the Taylor–Proudman effect dominates the flow structure when Ro is small. Computed curves of the friction factor for constant Dean number have their minimum at F ≈ −1. A composite parameter KL is introduced as a convenient governing parameter and used to correlate the characteristics. By applying KL to the analogy formula previously derived for two limiting flows, a semi-empirical formula for the friction factor is presented, which shows good agreement with the experimental data for a wide range of the parameters.
Potential threat of the international aquarium fish trade to silver arawana Osteoglossum bicirrhosum in the Peruvian Amazon
Authors: Moreau Marie-Annick , Coomes Oliver T.
Published: April 2006

Silver arawana Osteoglossum bicirrhosum are increasingly popular on the international aquarium fish market, but the routine killing of mouth brooding adults to collect juveniles for the trade may threaten wild populations. We describe the aquarium trade and fishery for silver arawana in the Peruvian Amazon. This is the first such report on the species for South America, and is based on field interviews with trade participants and fishermen, and on a review of government statistics. The regional trade is large, expanding and valuable (over 1 million juveniles worth USD 560,000 exported in 2001), of considerable economic importance to the rural poor, and in urgent need of research, monitoring and management. Outright bans on arawana fishing are likely to be ineffective and to destabilize an export fishery that provides significant part-time employment for the rural poor and substantial foreign earnings. Experimental studies are called for that compare the impacts on arawana yields of alternate fishing techniques, such as catch and release of brooding males, as a basis for developing more effective management schemes in Amazonia.
Using fill terraces to understand incision rates and evolution of the Colorado River in eastern Grand Canyon, Arizona
Authors: Pederson Joel L. , Anders Matt D. , Rittenhour Tammy M. , Sharp Warren D. , Gosse John C. , Karlstrom Karl E.
Published: April 2006

The incision and aggradation of the Colorado River in eastern Grand Canyon through middle to late Quaternary time can be traced in detail using well‐exposed fill terraces dated by a combination of optically stimulated luminescence, uranium series, and cosmogenic nuclide dating. This fluvial history provides the best bedrock incision rate for this important landscape and highlights the complications and advantages of fill terrace records for understanding river long‐profile evolution and incision. The use of fill terraces, as distinct from strath terraces, for calculating incision rates is complicated by the cyclic alluviation and incision they record. In the example of the Grand Canyon this has led to various rates being reported by different workers and rates that tend to be overestimates in shorter records. We illustrate that a meaningful long‐term bedrock incision rate of ∼140 m/m.y. can be extracted from the Grand Canyon record by linking episodes when the Colorado River is floored on bedrock. Variable incision rates reported in the greater region may be, to some degree, due to inconsistent calculations. Our data also highlight that the Colorado River has been a mixed alluvial‐bedrock river through both time and space and has been a bedrock river for less than half of its Pleistocene history. This strong temporal variation, combined with the varying bedrock the river encounters on its path, heightens the challenge of understanding the tectonic, climatic, and drainage integration controls on the form and evolution of the Colorado River's long profile.
Electrodynamic bare tether systems as a thruster for the Momentum‐Exchange/Electrodynamic Reboost (MXER) project
Authors: Khazanov G. V. , Krivorutsky E. N. , Gallagher D. L.
Published: April 2006

The concept of electrodynamic tether propulsion has a number of attractive features and has been widely discussed for different applications. Different system designs have been proposed and compared during the last 10 years. In spite of this, the choice of proper design for any particular mission is a unique problem. Such characteristics of tether performance as system acceleration, efficiency, etc., should be calculated and compared on the basis of the known capability of a tether to collect electrical current. We discuss the choice of parameters for circular and tape tethers with regard to the Momentum‐Exchange/Electrodynamic Reboost (MXER) tether project.
Observations of platelet ice growth and oceanographic conditions during the winter of 2003 in McMurdo Sound, Antarctica
Authors: Leonard G. H. , Purdie C. R. , Langhorne P. J. , Haskell T. G. , Williams M. J. M. , Frew R. D.
Published: April 2006

Platelet ice is the name given to ice crystals that nucleate in the ocean and grow either at depth or loosely attached to the ice‐water interface. Related to the proximity of ice shelves, it is known to form in supercooled seawater. This study details the conditions for its growth during the austral winter of 2003 in McMurdo Sound, Antarctica. A key finding is that the presence of platelet ice in the sea ice cover is conclusively linked to the time history of the appearance of ice crystals in the water column, monitored using the strength of the backscattered signal from an acoustic Doppler current profiler as a proxy. Generally, these crystals appeared from mid‐May as water near the interface became supercooled. This near‐surface supercooling appears to be related to a simultaneous, abrupt change in the structure of the upper 250 m of the water column, from one that behaved dynamically and contained both the warmest and coolest measured temperatures to one in which the water was essentially isothermal near its surface freezing temperature. Near‐surface ocean temperature was also affected by tidal mixing and by an increase in the thickness and density, over the course of winter, of the surface mixed layer created by salt rejection during ice growth. These processes allowed cold water, trapped by buoyancy in a band at the base of the mixed layer in early winter, to gain access to the ice‐water interface by midwinter. This band of cold water probably had its origin beneath the McMurdo Ice Shelf.
Formation and decay of a longshore baroclinic jet associated with transient coastal upwelling and downwelling: A numerical study with applications to the Baltic Sea
Authors: Zhurbas Victor , Oh Im Sang , Park Taewook
Published: April 2006

A numerical study is undertaken on the formation and decay of a longshore baroclinic jet (LBJ) caused by a transient wind stress favorable for upwelling and downwelling. The two‐pycnocline type of stratification, typical for the Baltic Sea summertime, results in a nonmonotonic growth of the LBJ velocity with wind stress and time and a two‐branch structure of the jet, with domination of a branch related to the seasonal thermocline (permanent halocline) in the case of fully developed downwelling (upwelling). The LBJ associated with the fully developed upwelling (downwelling) is found to display baroclinic instability, and its decay is accompanied by selective formation of mostly cyclonic (anticyclonic) eddies. If upwelling or downwelling is not fully developed, the LBJ formed in a flat bottom basin does not display baroclinic instability unless the β effect is included. The β effect causes a detachment of the LBJ jet from the shoreline in the eastern half‐basin and thereby stimulates baroclinic instability. As a result, mesoscale eddies are generated only in the eastern half‐basin, and only if the basin diameter D is large enough to satisfy the inequality D > , where RI is the baroclinic Rossby radius, f is the Coriolis parameter, and β = df/dy. Effect of topography on baroclinic instability makes it possible to develop eddies, even if the LBJ related to partially developed upwelling or downwelling is considered at β = 0.
Multi‐scale spatial correlation and scaling behavior of surface soil moisture
Authors: Ryu Dongryeol , Famiglietti James S.
Published: April 2006

The scaling behavior of surface soil moisture variance is presented across spatial scales of observation from 1 × 1 km2 to 140 × 140 km2. Semi‐variograms were used to analyze the spatial correlation in remotely sensed soil moisture data from SGP97. Results indicate that a nested correlation structure exists within regional scale fields. Three representative semi‐variograms were chosen to calculate the scaling of soil moisture variance with increasing support scale. While previous research at smaller scales (<1 km2) revealed that soil moisture variance follows a power law decay with increasing support area, we show that in the presence of significant spatial correlation at the larger scales studied here, a power law relationship no longer holds. Rather, the type of correlation function and correlation length play an important role in the relationship between soil moisture variance and support area. We suggest that understanding the spatial correlation pattern of soil moisture across scales is critical for characterizing the scaling behavior of soil moisture variance.
Inter‐annual sea level variability in the southern Gulf of Mexico (1966–1976)
Authors: Salas‐de‐León David Alberto , Monreal‐Gómez María Adela , Salas‐Monreal David , Riveron‐Enzastiga Mayra Lorena , Sánchez‐Santillan Norma Leticia
Published: April 2006

Hourly time series at seven locations throughout the southern Gulf of Mexico were used to calculate the trend and the inter‐annual sea level. The sea level series from January 1966 to December 1976 were filtered using a Lanczos low pass filter to remove oscillations with periods smaller than one year. The results revealed a sea level increment of about 1.4 mm yr−1 from 1966 to 1976 in the southern Gulf of Mexico. The monthly sea level variability obtained after the trends were removed, presented a sea level setup during winter and a sea level depression in summer attributed to seasonal wind conditions. The horizontal representation of averaged sea level in the southern Gulf of Mexico presented a saddle critical point. The associated sea level slope indicated water accumulation at Ciudad Madero in the western side of the gulf and Coatzacoalcos in the southernmost station, and sea level depressions at Tuxpan and Progreso in the southwestern and southeastern side of the gulf, respectively. Nevertheless, one of the most intriguing result is the presence of a Kelvin wave with a two mode oscillation axis that goes from Progreso to Tuxpan.
Folate synthesis in plants: purification, kinetic properties, and inhibition of aminodeoxychorismate synthase
Authors: Sahr Tobias , Ravanel Stéphane , Basset Gilles , Nichols Brian P. , Hanson Andrew D. , Rébeillé Fabrice
Published: April 2006

pABA (p-aminobenzoate) is a precursor of folates and, besides esterification to glucose, has no other known metabolic fate in plants. It is synthesized in two steps from chorismate and glutamine, the first step being their conversion into glutamate and ADC (4-aminodeoxychorismate). In Escherichia coli, two proteins forming a heterodimeric complex are required for this reaction, but, in plants and lower eukaryotes, a single protein is involved. The Arabidopsis enzyme was expressed in E. coli and was purified to homogeneity. The monomeric enzyme (95 kDa) catalyses two reactions: release of NH3 from glutamine (glutaminase activity) and substitution of NH3 for the hydroxy group at position 4 of chorismate (ADC synthase activity). The kinetic parameters of the plant enzyme are broadly similar to those of the bacterial complex, with Km values for glutamine and chorismate of 600 and 1.5 μM respectively. As with the bacterial enzyme, externally added NH3 was a very poor substrate for the plant enzyme, suggesting that NH3 released from glutamine is preferentially channelled to chorismate. The glutaminase activity could operate alone, but the presence of chorismate increased the efficiency of the reaction 10-fold, showing the interdependency of the two domains. The plant enzyme was inhibited by dihydrofolate and its analogue methotrexate, a feature never reported for the prokaryotic system. These molecules were inhibitors of the glutaminase reaction, competitive with respect to glutamine (Ki values of 10 and 1 μM for dihydrofolate and methotrexate respectively). These findings support the view that the monomeric ADC synthase is a potential target for antifolate drugs.
Participation of a galactose-specific C-type lectin inDrosophilaimmunity
Authors: Tanji Takahiro , Ohashi-Kobayashi Ayako , Natori Shunji
Published: April 2006

A galactose-specific C-type lectin has been purified from a pupal extract of Drosophila melanogaster. This lectin gene, named DL1 (Drosophilalectin 1), is part of a gene cluster with the other two galactose-specific C-type lectin genes, named DL2 (Drosophilalectin 2) and DL3 (Drosophilalectin 3). These three genes are expressed differentially in fruit fly, but show similar haemagglutinating activities. The present study characterized the biochemical and biological properties of the DL1 protein. The recombinant DL1 protein bound to Escherichia coli and Erwinia chrysanthemi, but not to other Gram-negative or any other kinds of microbial strains that have been investigated. In addition, DL1 agglutinated E. coli and markedly intensified the association of a Drosophila haemocytes-derived cell line with E. coli. For in vivo genetic analysis of the lectin genes, we also established a null-mutant Drosophila. The induction of inducible antibacterial peptide genes was not impaired in the DL1 mutant, suggesting that the galactose-specific C-type lectin does not participate in the induction of antibacterial peptides, but possibly participates in the immune response via the haemocyte-mediated mechanism.
Study of multipole contributions to the structure of water around ions in solution using the soft sticky dipole-quadrupole-octupole (SSDQO) model of water
Authors: Tan Ming-Liang , Lucan Laurentia , Ichiye Toshiko
Published: April 2006

The solvation of ions in the soft sticky dipole-quadrupole-octupole (SSDQO) model for liquid water is presented here. This new potential energy function for liquid water describes water-water interactions by a Lennard-Jones term plus a sticky potential consisting of an approximate moment expansion with point dipole, quadrupole, and octupole moments. The SSDQO potential energy function using the moments from extended simple point charge (SPC/E), TIP3P, or TIP5P reproduces the pair potential energy functions and radial distribution functions of the respective multipoint model but it is much faster than even the three-point models. Here, the solvation of ions in SSDQO water is studied using ion-water potential energy functions consisting of moment expansions up to the charge-quadrupole term, up to the charge-octupole term, and up to an approximate charge-hexadecapole term using the moments of SPC/E water. The radial distributions from Monte Carlo simulations show the best agreement with the results for ions in SPC/E water for the expansion up to the charge-hexadecapole term. Thus, the best results are obtained when the water-water and ion-water potentials are exact up to the 1∕r4 term and also contain an approximate 1∕r5 term. Overall, the simplicity, efficiency, and accuracy of the SSDQO potential make it potentially very useful for computer simulations of aqueous solvation.
Implicit versus explicit solvent in free energy calculations of enzyme catalysis: Methyl transfer catalyzed by catechol O-methyltransferase
Authors: Rod Thomas H. , Rydberg Patrik , Ryde Ulf
Published: April 2006

We compare free energy calculations for the methyl transfer reaction catalyzed by catechol O-methyltransferase using the quantum mechanical/molecular mechanical free energy method with implicit and explicit solvents. An analogous methylation reaction in a solution is also studied. For the explicit solvent model, we use the three-point transferable intermolecular potential model, and for the implicit model, we use the generalized Born molecular volume model as implemented in CHARMM. We find that activation and reaction free energies calculated with the two models are very similar, despite some structural differences that exist. A significant change in the polarization of the environment occurs as the reaction proceeds. This is more pronounced for the reaction in a solution than for the enzymatic reaction. For the enzymatic reaction, most of the changes take place in the protein rather than in the solvent, and, hence, the benefit of having an instantaneous relaxation of the solvent degrees of freedom is less pronounced for the enzymatic reaction than for the reaction in a solution. This is a likely reason why energies of the enzyme reaction are less sensitive to the choice of atomic radii than are energies of the reaction in a solution.
Collision-induced alignment of H2O+ drifting in helium
Authors: Chen Xin , Thachuk M.
Published: April 2006

The collision-induced alignment of H2O+ drifting in helium is studied with a molecular dynamics method that has been extended to treat nonlinear rigid ions. Rotational distribution functions and averaged quantities are presented in terms of the ρ formalism [M. Thachuk, Phys. Rev. A 72, 032722 (2005)], and it is shown that this description gives a very good agreement with simulation results. In addition to velocity and angular velocity autocorrelation functions, a velocity-angular velocity cross correlation function is introduced. This cross correlation function provides insight into the dynamical nature of the alignment mechanism.
Low loss giant dielectric and electrical transport behavior of KxTiyNi1−x−yO system
Authors: Jana Pradip Kumar , Sarkar Sudipta , Chaudhuri B. K.
Published: April 2006

The KxTiyNi1−x−yO system in the series AxTiyNi1−x−yO (A=Li, K, Na; x=0.05–0.30, y=0.02) shows the highest dielectric constant ε′∼105 and lowest loss. The high ε′ value is attributed to microstructures, which form boundary layer capacitors. Electrical conductivity in these materials follows small polaron hopping mechanism in the nonadiabatic regime. Unlike LixTiyNi1−x−yO and NaxTiyNi1−x−yO (NTNO), KxTiyNi1−x−yO (KTNO) exhibits an anomaly around Tp∼430K. Tp shifts to the lower temperature range with increasing K content which is related to the higher ionic radius of K.
Automatic system for single ion/single cell irradiation based on Cracow microprobe
Authors: Veselov O. , Polak W. , Lekki J. , Stachura Z. , Lebed K. , Styczeń J. , Ugenskiene R.
Published: April 2006

Recently, the Cracow ion microprobe has found its new application as a single ion hit facility (SIHF), allowing precise irradiations of living cells by a controlled number of ions. The instrument enables a broad field of research, such as survival studies, adaptive response investigations, bystander effect, inverse dose-rate effect, low-dose hypersensitivity, etc. This work presents principles of construction and operation of the SIHF based on the Cracow microprobe. We discuss some crucial features of optical, positioning, and blanking systems, including self-developed software responsible for semiautomatic cell recognition, for precise positioning of cells, and for controlling the irradiation process. We also show some tests carried out to determine the efficiency of the whole system and of its segments. In addition, we present results of the first irradiation measurements performed with living cells.
Ultrafast molecule sorting and delivery by atomic force microscopy
Authors: Unal Kerem , Frommer Jane , Kumar Wickramasinghe H.
Published: April 2006

An atomic force microscope (AFM) is tailored to perform ultrafast electrophoretic differentiation of molecules on populations of <0.1zeptomoles (10−22moles) on the surface of a probe tip. The driving force for differentiation is a large electric field applied over the length of an AFM tip that results in enhanced differential mobilities stemming from the confinement of the water layer on the tip surface. In a demonstration on DNA oligonucleotides, a 5-mer and a 16-mer exhibit migration times of 15 and 5ms, respectively, approximately five orders of magnitude faster than in conventional capillary electrophoresis.
Device operation of InGaN heterojunction bipolar transistors with a graded emitter-base design
Authors: Chung T. , Limb J. , Yoo D. , Ryou J.-H. , Lee W. , Shen S.-C. , Dupuis R. D. , Chu-Kung B. , Feng M. , Keogh D. M. , Asbeck P. M.
Published: April 2006

The device operation of InGaN heterojunction bipolar transistors with a graded InGaN emitter-base design grown by metal organic chemical vapor deposition on sapphire substrates is demonstrated. The Gummel plot, current gain, and common-emitter current-voltage characteristics of the device are presented. The dc common-emitter current gain of a 25×25μm2 (emitter size) device increases with collector current and the current gain reaches a high value of 13 at IC=10mA with a base width of 100nm and a hole concentration of p=2×1018cm−3. The improved device performance is attributed to the graded emitter-base design as well as the high quality of the material made possible by the indium composition grading that enables the epitaxial growth of InGaN layers with a low density of pits or defects. The results demonstrate the potential of the graded InGaN emitter-base junction design in nitride heterojunction bipolar transistors.
Progress in development of spotted medics (Medicago arabica L. Huds.) for Mediterranean farming systems
Authors: Nair Ramakrishnan M. , Hughes Steve J. , Peck David M. , Crocker Graham , Ellwood Simon , Hill Jeffrey R. , Hunt Colleen H. , Auricht Geoffrey C.
Published: April 2006

Spotted medics (Medicago arabica) have become naturalised in Australia, but the spiny nature of their pods has prevented commercial release of any cultivar. Fifty-eight accessions representing Medicago arabica in the Australian Medicago Genetic Resources Collection were grown as spaced plants at Turretfield, South Australia, and the variation for important agronomic traits was studied. There was large variation for traits including days to flowering, dry matter production, pod and seed yield, and pod spininess. Principal component and cluster analyses conducted for 13 traits revealed 5 clusters. One of the clusters identified comprised accessions originating from Greece and Cyprus, which were found to have high agronomic potential. The study has helped in identifying the relationship among traits, namely pod spininess, days to flowering, dry matter yield, and pod and seed yield, which would be useful to breeders for future breeding and selection programs. A sward trial at Moree, New South Wales, comprising a selected cohort of spotted medic accessions, enabled the identification of 2 early flowering and high dry matter yielding accessions; however, both exhibited spiny pods. These 2 accessions were crossed with a smooth-podded accession, and the F1 plants were confirmed using a microsatellite marker. Days to flowering showed a continuous pattern of variation in the F2, suggesting that the trait is quantitatively inherited, whereas segregation ratio revealed that a single recessive gene controlled the smooth pod trait. Early flowering, smooth-podded F2 plants were selected for cultivar development.
Influence of genetically modified rice containing codA gene on physiological metabolism and genetic horizontal transformation in fed rats
Authors: Zhi-Hui Zhao , Li-Tao Yang , Xiao-Jie Ai , Da-Bing Zhang , Si-Xiang Zou
Published: April 2006

To analyse the influence of genetically modified (GM) rice (Oryza sativa) containing the exogenous choline oxidase (codA) gene on physiological metabolism and genetic horizontal transformation in the fed rats, the animals were divided randomly into two groups. One group was fed with the feedstuff containing 30% of transgenic rice. The remaining (control) group was fed with the feedstuff containing 30% of non-transgenic rice. After 30 days, growth, physiological metabolism parameters such as growth hormone (GH), insulin, glucagon, 3,3′,5-triiodothyronine (T3), thyroxine (T4), thyroid-stimulating hormone (TSH), and the genetic horizontal transformation were analysed. Results indicated that the weight of all rats from the two groups was similar (P>0.05). Also, there was no significant difference in the level of GH, insulin, glucagon, T4, T3 and TSH between the treated and untreated rats. The serum urea nitrogen (SUN), glucose, the glutamate–pyruvate transaminase (GTP), as well as the total cholesterol, of treated rats were almost identical to those of the control (P>0.05). Moreover, no target DNA sequence of rice endogenous sucrose phosphate synthase (SPS) gene or exogenous choline oxidase (codA) gene was detected in organs (liver, muscle, pancreas, etc.) except the stomach, gastrointestinal and rectum contents, and no genetic horizontal transformation was observed in rats fed with transgenic rice.
PCR for the detection of the anti-herbicide genes in genetically modified organisms
Authors: Wen-Tao Xu , Kun-Lun Huang , Ai-Ke Deng , Yun-Bo Luo
Published: April 2006

Genetically modified organisms (GMOs) containing anti-herbicide genes account for more than 75% of all GMO and the proportion is increasing. The polymerase chain reaction (PCR) method has proved to be an invaluable tool for the specific and sensitive detection of genetically modified material in foodstuffs and PCR screening for the presence of transgenic components in food is becoming a routine method in modern food analysis. In this study, the five kinds of the anti-herbicide genes (bar, pat,cp4-epsps1,cp4epsps2andgox) were examined by PCR in four kinds of genetically modified crops (soy, maize, cotton and rape). Results indicate that the method was sensitive, specific and credible, and that all genetically modified and approved crops containing the anti-herbicide genes can be examined by this method.
Map2mod—a server for evaluation of crystallographic models and their agreement with electron density maps
Authors: Kirillova Olga , Minor Wladek
Published: April 2006

Summary: Here we report on recent developments of the map2mod server. It has been designed for validation of protein models created by X-ray data interpretation. It can also be used during the refinement process since it is able to indicate problem regions in the model. Apart from evaluation of model quality, it has an option to remove atoms of side chains, which are not consistent with the maps as well as improperly placed water molecules. There are two additional options: checking the B-factors of atoms in the provided model and comparison of R and Rfree values obtained as the result of refinement with the averages characteristic for the data resolution shell.

Availability: The map2mod server is freely available for all user community ().

Contact: olga,wladek@iwonka.med.virginia.edu
Comparative Study on the Long‐Term Effectiveness Between Coblation‐ and Microdebrider‐Assisted Partial Turbinoplasty
Authors: Lee Jae Yong , Lee Jong Dae
Published: April 2006

Objectives: Various surgical methods have been tried to relieve the symptoms of nasal obstruction in patients with inferior turbinate hypertrophy. Recently, coblation that uses the radiofrequency and microdebrider is being increasingly used in turbinate surgery. The aim of this study was to compare the long‐term postoperative outcome between the coblation‐ and microdebrider‐assisted partial turbinoplasty.

Methods: We selected 60 patients for this prospective study who had nasal obstruction and hypertrophied turbinate mucosa that was refractory to medical treatment. Thirty patients were treated with coblation (group 1) and 30 patients were treated with microdebrider (group 2). Postoperative changes in degree of nasal obstruction were evaluated prospectively at 3, 6, and 12 months after the procedure. A cross‐sectional area of second notch and volume of nasal cavity were compared at 12 months after operation. Operation time, duration of crust formation, postnasal drip, and postoperative bleeding were also compared.

Results: Nasal obstruction was improved significantly in both groups at 3, 6, and 12 months after the procedure. However, when compared between two groups, symptom improvement was statistically significant in group 2 at 12 months after surgery. Acoustic rhinometry performed at 12 months demonstrated a significant increase of cross‐sectional area of second notch and volume of nasal cavity in group 2 in comparison with group 1. There were no significant differences in degree of postnasal drip, operation time, or duration of crust formation between the two groups.

Conclusion: This study suggests that microdebrider‐assisted partial turbinoplasty is more effective and satisfactory in long‐term relief of nasal obstruction and reduction in mucosal volume of anterior head of inferior turbinate.
Surgical Removal of Jugular Paragangliomas After Stenting of the Intratemporal Internal Carotid Artery: A Preliminary Report
Authors: Sanna Mario , Khrais Tarek , Menozi Roberto , Piaza Paolo
Published: April 2006

Objective: Jugular paragangliomas with extensive involvement of the internal carotid artery (ICA) represent a true challenge for surgeons, especially in the presence of inadequate collateral circulation through the circle of Willis. The aim of our study is to present a preliminary report of our experience with the surgical removal of three such cases using the stenting of the ICA as the method of choice for protecting and preserving the integrity of the artery.

Methods: This retrospective study was conducted at Gruppo Otologico, a private referral center for neurotology and skull base surgery. The subjects of our study are three cases of jugular paragangliomas with extensive involvement of the ICA and inadequate collateral circulation. These cases are the first three cases operated at our center after stenting of the intratemporal portion of the ICA.

Results: Complete surgical removal of the tumor, including the part involving the ICA, was achieved in all cases. Over a follow‐up period of 22 to 30 months, no complications occurred and the patency of the stented arteries was preserved.

Conclusion: Although more follow‐up is still needed before establishing the exact long‐term outcome of stenting the intratemporal ICA, our preliminary report shows that the stent has facilitated the complete surgical removal of the tumor, preserving the integrity of the ICA.
Partial Cricotracheal Resection for Successful Reversal of Laryngotracheal Separation in Patients with Chronic Aspiration
Authors: Hricko Peter , Storck Claudio , Schmid Stephan , Stoeckli Sandro J.
Published: April 2006

Objective: To present our experience with successful reversal of laryngotracheal separation in patients with chronic aspiration, to discuss our surgical technique, and to review the literature.

Study Design: Retrospective case review.

Methods: The medical records of two patients who underwent a successful reversal of laryngotracheal reversal after separation were reviewed. The two patients were evaluated clinically with videostroboscopy and videofluoroscopy.

Results: Both patients presented with intractable aspiration despite protective tracheostomy because of impairment of lower cranial nerve function. After laryngotracheal separation, swallowing rehabilitation was safely possible, and neurologic improvement allowed reversal of the separation procedure. For reversal, we present the use of a partial cricotracheal resection with tracheocricothyropexia similar to the technique used for subglottic stenosis. Both patients were successfully reversed.

Satisfactory voice and swallowing function 7 and 10 years after reversal, respectively, could be assessed through our evaluation. Review of the literature revealed a total of 13 cases of successful reversal after laryngotracheal separation. Technical details of surgery and functional results are rarely reported.
Research on twins: implications for parenting
Authors: SHOWERS JACY , McCLEERY JANET T.
Published: April 2006

Summary
A review of the literature on twins is provided regarding bonding, parent preference, temperament and personality, the separation‐individuation process, cognitive development, and child abuse. Practical suggestions are given for successfully parenting twins toward optimal growth and development.
Cerebral function in iron deficiency: a review
Authors: EVANS D. I. K.
Published: April 2006

Summary
Studies in many parts of the world have shown that children with iron deficiency and anaemia show minor defects of cerebral function such as poor attentiveness, poor coordination and slightly impaired scores on developmental assessment. The patients improve rapidly after treatment with iron—too quickly for their anaemia to have been corrected. Such changes have not been detected in children with anaemia from other causes, nor in patients with iron deficiency too slight to cause anaemia. The possibility that these changes are due in some way to some other aspect of malnutrition has not been excluded. Fortunately they are minimal, easily reversible and potentially preventable.
The choice to breast feed or bottle feed and influences upon that choice: a survey of 1525 mothers
Authors: JONES DEE A.
Published: April 2006

Summary
A consecutive sample of 1525 mothers was interviewed after delivery in hospital in order to investigate the characteristics of breast and bottle feeders and to examine the reasons for deciding how to feed and the influences upon that decision. Breast feeding was associated with age, social class and parity. A woman's choice of feeding was strongly associated with her husband's opinion if he had a definite preference; also her choice was associated with the feeding method of her own mother if it had been consistent. The most frequent reasons for breast feeding were the belief that it was ‘better for the baby’ and that it was ‘natural’. The most commonly reported reasons for bottle feeding were that breast feeding was inconvenient and embarrassing. Women's own previous failures at breast feeding and those of their friends were powerful influences upon many mothers.
Differences in attention control between ‘clinic‐observable’ and ‘reported’ hyperactivity: a preliminary report
Authors: LEUNG PATRICK W. L. , LUK S.L.
Published: April 2006

Summary
A series of attention tests were administered to two groups of hyperactive children and a control group of normal children. The first group of hyperactive children had both ‘reported’ hyperactivity (defined as having hyperactive behaviour reported at school and home) and ‘clinic‐observable’ hyperactivity (defined as having hyperactive behaviour readily observable in a clinic interview). The second group had only ‘reported’ hyperactivity. The results of attention testing indicated that the children with both ‘reported’ and ‘clinic‐observable’ hyperactivity had significant attentional difficulties in comparison with children with ‘reported’ hyperactivity as well as with the normal controls. On the other hand, the children with ‘reported’ hyperactivity had less evidence of attentional problems when compared to the normal children. Hence; the differentiation into ‘reported’ and ‘clinic‐observable’ hyperactivity was of theoretical importance as clinic behaviour was a significant diagnostic marker in predicting performance in attention tests. The results of this study suggest the presence of different types of attention deficits in ‘reported’ and ‘clinic‐observable’ hyperactivity respectively as well as heterogeneity in hyperactive children.
Meeting the needs of young deaf‐blind children and their parents Part 2
Authors: ANDREW ANN K.
Published: April 2006

Summary In this paper the writer continues the theme of the deaf‐blind child and focuses on the needs of the parents, by considering the needs of all parents with handicapped children and the specific needs of those with a deaf‐blind child. The stages of grieving and the importance of time for adjustment are discussed, and also the necessity for practical help, advice and resources from those who really understand the problems and the value of contact with older parents who have come through the experience. Issues of education, hearing aids and a brief consideration of the underlying principles in programme planning for the deaf‐blind child are also considered.
The comparative efficacy of antecedent exercise and methylphenidate: a single‐case randomized trial
Authors: SILVERSTEIN JAY M. , ALLISON DAVID B.
Published: April 2006

Summary
This study evaluated the comparative efficacy of antecedent exercise, methylphenidate (Ritalin), and placebo in the reduction of hyperactive behaviour in a pre‐school boy. A single‐case alternating treatments experimental design was employed for a total of 82 days. The dependent variable was the Conners' Abbreviated Symptom Questionnaire. Antecedent exercise failed to reduce hyperactive behaviour. Methylphenidate produced significantly less hyperactive behaviour than both placebo and antecedent exercise (P = 0.0238). Neither methylphenidate nor antecedent exercise produced notable side‐effects as measured by the Monitoring of Side‐Effects Scale. These data add to a sparse literature on the effects of antecedent exercise and methylphenidate amongst pre‐school children.
Groups for parents of pre‐school children with severe disabilities
Authors: STALLARD P. , DICKINSON* F.
Published: April 2006

Summary
The emotional impact upon the family following the diagnosis of a child's disability is significant although parents feel that their needs are not specifically addressed by professionals. A series of groups for the parents of pre‐school children with severe disabilities are described. The groups are designed to provide parents with an opportunity to discuss in depth the impact of their childs' disability upon themselves, their partners and their families. Feedback from group members is reported and the practical issues in providing such groups discussed.
The clinical significance of mediators of cellular immunity
Authors: DUMONDE D. C. , MAINI R. N.
Published: April 2006

This paper reviews experimental and clinical evidence for the existence of soluble mediators of cellular immune responses. Clinical appraisal of this field is now emerging from the stage of biological definition and technical development to the stage at which acceptable standards of mediator activity will now be required. The biological significance of these mediators may lie in amplification and regulation of the immunological response. The clinical significance of this field lies in the detection, assay and repair of genetic or non‐genetic disorders of cell‐mediated immunity. Development of this field will be much assisted by parallel studies of cell‐mediator function in both animals and man; and, with some optimism, may yield a predictive basis for control of the cellular immune response.