bluuebunny/crossref_metadata_2025 huggingface dataset:
On the compositional field of self‐reversing titanomaghemite: Constraints from Deep Sea Drilling Project Site 307
Authors: Doubrovine Pavel V. , Tarduno John A.
Published: November 2005

In 1956, Verhoogen proposed that ionic reordering during low‐temperature oxidation of titanomagnetite could result in self‐reversal of natural remanent magnetization. Later, in 1966, O'Reilly and Banerjee concluded that (1) the compositional field of self‐reversing titanomaghemite was restricted to very high oxidation states and (2) that high oxidation temperature (≥250°C) would be required to reach these oxidation levels, which would in turn be inconsistent with stability of the cation‐deficient structure of titanomaghemite in nature. However, an example of the process has been reported, in some altered pillow basalt lavas of Late Cretaceous age from Detroit Seamount (Ocean Drilling Program (ODP) sites 883, 1203, and 1204) in the northwestern Pacific Ocean. Here we present new paleomagnetic, rock magnetic and compositional data from mid‐ocean ridge tholeiitic basalts of Late Jurassic age collected at Deep Sea Drilling Project (DSDP) Site 307. Although severely oxidized, the DSDP Site 307 basalt samples lack the clear self‐reversed magnetizations seen in some samples from Detroit Seamount. These data constrain the compositional field of self‐reversing titanomaghemite to extremely high oxidation states (z ≥ 0.95), consistent with the first conclusion of O'Reilly and Banerjee. The comparison of results from ODP sites 883, 1203, and 1204 on Detroit Seamount and those from the DSDP Site 307 basalts suggests that the presence of self‐reversed magnetizations may signify unusually vigorous and sustained fluid flow that resulted in very efficient removal of Fe from titanomaghemite producing the extremely high oxidation states required for self‐reversal.
Interplay between the ionic and electronic density profiles in liquid metal surfaces
Authors: González L. E. , González D. J. , Stott M. J.
Published: November 2005

First-principles molecular-dynamics simulations have been performed for the liquid-vapor interfaces of liquid Li, Mg, Al, and Si. We analyze the oscillatory ionic and valence electronic density profiles obtained, their wavelengths, and the mechanisms behind their relative phase shift.
A study of electronic structures of Pt3M (M=Ti,V,Cr,Fe,Co,Ni) polycrystalline alloys with valence-band photoemission spectroscopy
Authors: Mun Bongjin Simon , Watanabe Masamitsu , Rossi Massimiliano , Stamenkovic Vojislav , Markovic Nenad M. , Ross Philip N.
Published: November 2005

The surface valence-band densities of states (DOS) of Pt3M (M=Ti,V,Cr,Fe,Co,Ni) polycrystalline alloys were investigated with ultraviolet photoemission spectroscopy. Upon annealing the ion-sputter-cleaned alloys at high temperatures, the observed valence-band DOS spectra clearly show the modified electronic structures on the surfaces suggesting the surface segregation of Pt as predicted in thermodynamic models. The measured d-band centers and widths for the annealed alloy surfaces show qualitatively the same trend as predicted by density-functional-theory calculations based on the model of a Pt “skin” on the topmost surface layer and a subsurface layer enriched in the 3d transition metal.
Attachment of fiber array adhesive through side contact
Authors: Majidi Carmel S. , Groff Richard E. , Fearing Ronald S.
Published: November 2005

Very slender cylindrical fibers are capable of bending over and maintaining side contact with an opposing substrate even as the fibers are pulled away, providing a mode of adhesion for fiber array adhesives. This paper analyzes side contact and its effect on normal adhesion and provides guidelines for fiber length to achieve side contact under zero load as a function of elastic modulus, area moment of inertia, initial geometry, and energy of adhesion between fiber and substrate. Numerical results for several relevant geometries are presented as well as a comparison to recently reported normal adhesion measurements of multiwalled carbon nanotube arrays.
Nucleation and size distribution of nucleus during induction period of polyethylene crystallization
Authors: Das Narayan Chandra , Hikosaka Masamichi , Okada Kiyoka , Toda Akihiko , Inoue Katsuaki
Published: November 2005

The crystallization process from supercooled melt results in the formation of nanosize nuclei in the earlier stage (induction period) through subsequent attachment or detachment of repeating unit to nuclei. The size distribution of nucleus f(Nj,t) in the induction period of nucleation process from the melts has not been experimentally confirmed yet by direct observation. The reason is that the number density of nuclei ν is too small to be detected experimentally. In our previous work, we showed the direct evidence of nucleation experimentally by means of small angle x-ray scattering (SAXS) technique. Further we have succeeded to observe the nucleation and f(Nj,t) of polymer crystallization from the melts by SAXS using synchrotron radiation. We increased ν by adding a nucleating agent to a polymer (polyethylene). The time evolution of f(Nj,t) was observed for the first time.
Instability inside a rotating gas cylinder subject to axial periodic strain
Authors: Duguet Y. , Scott J. F. , Le Penven L.
Published: November 2005

We study numerically the instability of a confined rotating gas flow subject to periodic strain along the axis of rotation, under the low Mach number approximation. An axisymmetric time-stepping spectral Galerkin-type code is used to investigate the viscous basic flow and its stability. Parametric resonance can lead to instability of this flow via the growth of inertial modes coupled by the oscillating strain. The marginal stability curve compares well with earlier experimental and (asymptotic) analytical results in the case of the axisymmetric inertial mode (1,1,0). The resulting flow is dominated by a time-oscillating toroidal vortex and differs very little from the theoretical mode. Two different nonlinear regimes are found, one with saturation to a constant modal amplitude, the other with weak periodic modulation. We also show evidence of the presence of an azimuthal circulation, apparently responsible for the observed modulation.
Surface-detached V-shaped yoke of obliquely bonded magnetostrictive strips for high transduction of ultrasonic torsional waves
Authors: Park Chan Il , Kim Woochul , Cho Seung Hyun , Kim Yoon Young
Published: November 2005

When slender magnetostrictive strips that are obliquely bonded on the surface of a pipe are subjected to a time-varying magnetic field, the strips deform mechanically because of the magnetostrictive effect and in turn, ultrasonic torsional waves are generated in the pipe. If the magnetic flux density in the strips can be increased by simply modifying the magnetic path, the sensitivity of the generated wave signal with respect to the applied magnetic field strength can be considerably enhanced even without increasing the magnetic field strength. Sensitivity has been one of the most important factors in sensors. To achieve this objective, yokes can be used, but improper yoke configurations can generate unwanted additional wave modes with no sensitivity improvement. Consequently, the problem of an optimal yoke configuration to increase the sensitivity was formulated as a topology optimization problem, and an interesting V-shaped yoke was found to be the optimal configuration. When the designed yokes were employed in actual experiments, the sensitivity of the measured wave signal was increased by as much as 7.5 times without needing to increase the magnetic strength.
Irradiation system of ions (H–Xe) for biological studies near the Bragg peak
Authors: Konishi Teruaki , Yasuda Nakahiro , Takeyasu Akihiro , Ishizawa Sachi , Fujisaki Takashi , Matsumoto Kenichi , Furusawa Yoshiya , Sato Yukio , Hieda Kotaro
Published: November 2005

We have developed a new system for irradiating biological samples in air with ions from H to Xe below 6.0MeV∕nucleon near the Bragg peak. The irradiation system can provide ion beams with 20-mm diameter of which the central area of 100mm2 is uniform in fluence rate within a standard deviation of ±10%. For each ion, the linear energy transfer is selectable by irradiation positions in air, from the lowest at the surface of a vacuum window to the highest at the Bragg peak, for example, from 281 to 977 keV/μm for C ions. A wide range of fluence rates, 10−3–104ions∕μm2∕s, can be provided by the system, which makes it possible to irradiate a variety of biological samples with different target sizes, from small plasmid DNA to living mammalian cells. The ion fluence irradiated to each sample is calculated from the output of the secondary electron monitor using the linear relationship between the output and ion fluence measured at the sample position by CR-39 track detectors. Survival curves and visualization of NBS1 foci for human cells are presented as examples of preliminary experiments using C ions near the Bragg peak.
Phase contrast radiography. II. Imaging of complex objects
Authors: Arhatari Benedicta D. , Nugent Keith A. , Peele Andrew G. , Thornton John
Published: November 2005

An image model for phase contrast in projection radiography of complex objects is presented and tested experimentally. The model includes the wavelength distribution of the radiation. The model is used to optimize the contrast of a radiograph of a piece of aluminium containing a fine crack.
Absolute calibration of extreme ultraviolet optical components with an x-ray-induced fluorescence source
Authors: Ueda Nobuyoshi , Nishimura Hiroaki , Fujioka Shinsuke , Miyanaga Noriaki , Izawa Yasukazu , Uegaki Junya , Shimizu Kazuaki , Yamada Takashi
Published: November 2005

A calibration system for extreme ultraviolet (EUV) optical components has been developed. In the system, x rays from a conventional tube induce fluorescence in source materials, which is detected with a gas flow counter or a charge-coupled device detector. The transmittance of an EUV filter (Zr foil) and the diffraction efficiency of a grazing incidence grating were measured and compared with measurements by other sources and calculations. The measured transmission of a filter for 13.5nm light was 14.4%±0.6%, which agrees well with 14.55% measured with synchrotron orbital radiation. As for the gratings, the first-order diffraction shows good agreement with the model calculation, while the second order one has a remarkable discrepancy between the measurement and the calculation.
Isobaric and isochoric fragilities and the influence of volume on the temperature dependence of local segmental relaxation in polyvinylethylene networks
Authors: Roland C. M. , Roland D. F. , Wang J. , Casalini R.
Published: November 2005

The ratio of the isochoric and isobaric activation enthalpies at Tg is used to quantify the relative contributions of the specific volume and temperature to the local segmental dynamics of polyvinylethylene networks. The dynamics of the networks become more dominated by temperature with increasing cross-link density, consistent with an increasing isobaric fragility. We also find a correlation between the isochoric and isobaric fragilities for the polyvinylethylene networks, in accord with a previously reported relationship between these two quantities for polymers and molecular glass-forming liquids [R. Casalini and C. M. Roland, Phys. Rev. E 72, 031503 (2005)].
Characterization of pottery fragments by nondestructive neutron diffraction
Authors: Barilaro Donatella , Crupi Vincenza , Majolino Domenico , Venuti Valentina , Barone Germana , Kockelmann Winfried
Published: November 2005

The aim of the present work is the characterization of pottery fragments coming from the town of Caltagirone (Sicily, Italy). The samples belong to very different historical periods, from 18th century B.C. to 16th century A.D., and have finely decorated surfaces. Time-of-flight neutron-diffraction measurements were performed in order to obtain a quantitative identification of the mineralogical composition of the samples. A good determination of the relative weight fractions of the phases was obtained using the Rietveld analysis method. The application of neutron-diffraction technique allowed us to carry out a detailed analysis in a nondestructive way, so intact large fragments were investigated without damaging the precious decoration on the surface.
Numerical simulation of bubble growth in film boiling using a coupled level-set and volume-of-fluid method
Authors: Tomar G. , Biswas G. , Sharma A. , Agrawal A.
Published: November 2005

A coupled level-set and volume-of-fluid method is presented for modeling incompressible two-phase flows with surface tension. The coupled algorithm conserves mass and captures the complicated interfaces very accurately. A planar simulation of bubble growth is performed in water at near critical pressure for different degrees of superheat. The effect of superheat on the frequency of bubble formation has been analyzed. In addition, simulation of film boiling and bubble formation is performed in refrigerant R134a at near critical and far critical pressures. The effect of saturation pressure on the frequency of bubble formation has also been studied. A deviation from the periodic bubble release is observed in the case of superheat beyond 15K in water. The effect of heat flux on the instability has also been analyzed. It is found that for water at near critical condition, a decrease in superheat from 15to10K leads to oscillations with subharmonics influencing the time period of the ebullition cycle.
Maser oscillation in a whispering-gallery-mode microwave resonator
Authors: Bourgeois P.-Y. , Bazin N. , Kersalé Y. , Giordano V. , Tobar M. E. , Oxborrow M.
Published: November 2005

We report the observation of above-threshold maser oscillation in a whispering-gallery (WG)-mode resonator, whose quasitransverse-magnetic, 17th-azimuthal-order WG mode, at a frequency of approximately 12.038GHz, with a loaded Q of several hundred million, is supported on a cylinder of monocrystalline sapphire. An electron spin resonance associated with Fe3+ ions, that are substitutively included within the sapphire at an effective concentration of a few parts per billion, coincides in frequency with that of the (considerably narrower) WG mode. By applying a cw “pump” to the resonator at a frequency of approximately 31.34GHz, with no applied dc magnetic field, the WG (“signal”) mode is energized through a three-level maser scheme. Preliminary measurements demonstrate a frequency stability (Allan deviation) of a few times 10−14 for sampling intervals up to 100s.
Josephson junctions with nearly superconducting metal silicide barriers
Authors: Chong Yonuk , Hadacek N. , Dresselhaus P. D. , Burroughs C. J. , Baek B. , Benz S. P.
Published: November 2005

We present a detailed study of the electrical properties of Nb-based planar Josephson junctions with superconducting metal silicide barriers, TiSi2 and WSi2. While these nonhysteretic junctions are useful for voltage standard applications, they are also an excellent model system to study proximity coupling in junctions having a barrier with a finite superconducting transition temperature. These silicide-barrier junctions have excellent uniformity and controllability, but as opposed to junction barriers with no measurable superconducting transition, the critical current of these superconducting-barrier junctions is a strong function of the operating temperature near 4 K; we also discuss the impact of this temperature dependence on device applications.
Generation of terahertz pulses with arbitrary elliptical polarization
Authors: Amer N. , Hurlbut W. C. , Norton B. J. , Lee Yun-Shik , Norris T. B.
Published: November 2005

We employ two different methods to generate controllable elliptical polarization of teraherz (THz) pulses. First, THz pulses are generated via optical rectification in nonlinear crystals using a pair of temporally separated and perpendicularly polarized optical pulses. The THz ellipticity is controlled by adjusting the relative time delay and polarization of the two optical pulses. We generate mixed polarization states of single-cycle THz pulses using ZnTe, and elliptically polarized multicycle THz pulses in periodically poled lithium niobate crystals. Second, we generate elliptically polarized THz pulses by making a THz “wave plate” using a combination of a wire-grid THz polarizer and a mirror to transform linearly polarized multicycle THz pulses into elliptical polarization.
Giant tunneling magnetoresistance in fully epitaxial body-centered-cubic Co∕MgO∕Fe magnetic tunnel junctions
Authors: Yuasa Shinji , Katayama Toshikazu , Nagahama Taro , Fukushima Akio , Kubota Hitoshi , Suzuki Yoshishige , Ando Koji
Published: November 2005

Fully epitaxial bcc Fe1−xCox(001)∕MgO(001)∕Fe(001) magnetic tunnel junctions (x=0, 0.5, 1) were fabricated with molecular-beam epitaxy and microfabrication techniques. While the bcc Fe(001) and Fe0.5Co0.5(001) electrodes had similar magnetoresistance (MR) ratios of about 180% at room temperature, the bcc Co(001) electrode exhibited a higher MR ratio up to 271% at room temperature (353% at 20 K). The fact that the MR ratio for a bcc Co electrode is much higher than that for a bcc Fe electrode is consistent with first-principle calculations, indicating the importance of electrode band structure in the k‖=0 direction.
Spin transfer switching current reduction in magnetic tunnel junction based dual spin filter structures
Authors: Huai Yiming , Pakala Mahendra , Diao Zhitao , Ding Yunfei
Published: November 2005

Spin-transfer-driven magnetization switching was studied in single magnetic tunneling junctions (MTJ: Ta∕PtMn∕CoFe∕Ru∕CoFeB∕Al2O3∕CoFeB∕Ta) and dual spin filters (DSF: Ta∕PtMn∕CoFe∕Ru∕CoFeB∕Al2O3∕CoFeB∕spacer∕CoFe∕PtMn∕Ta) having resistance-area (RA) product in the range of 10–30Ωμm2 and tunnel magnetoresistance (TMR) of 15%–30%. The intrinsic critical current density (Jc0) was estimated by extrapolating experimentally obtained critical current density (Jc) versus pulse width (τ) data to a pulse width of 1ns. Jc, extrapolated to τ of 1ns (∼Jc0), was 7×106 and 2.2×106A∕cm2, respectively, for the MTJ and improved DSF samples having identical free layers. Thus, a significant enhancement of the spin transfer switching efficiency is seen for DSF structures compared to the single MTJ case.
Low-threshold-current operation of 1540 nm GaInAsP∕InP distributed-feedback lasers with multiple-quantum-wire active regions
Authors: Yagi Hideki , Miura Koji , Nishimoto Yoshifumi , Plumwongrot Dhanorm , Ohira Kazuya , Maruyama Takeo , Arai Shigehisa
Published: November 2005

1540 nm wavelength GaInAsP∕InP distributed-feedback lasers consisting of multiple-quantum-wire active regions with the wire width of 24 nm were realized by electron-beam lithography, CH4∕H2 reactive ion etching, and two-step organometallic vapor-phase-epitaxial growth processes. A threshold current as low as 2.7 mA (threshold current density=270A∕cm2), a differential quantum efficiency of 19%∕facet and a submode suppression ratio of 51 dB at a bias current of twice the threshold were achieved for the stripe width of 3.0μm and the cavity length of 330μm under a room-temperature continuous-wave condition.
Efficient blue electroluminescent device using tetra(β-naphthyl)silane as a hole-blocking material
Authors: Yu Gui , Xu Xinjun , Liu Yunqi , Jiang Zuoquan , Yin Shiwei , Shuai Zhigang , Zhu Daoben , Duan Xiaobang , Lu Ping
Published: November 2005

We report an efficient blue light-emitting diode (LED) using N, N′-bis(1-naphthyl)-N, N′-diphenylbenzidine as an emitting layer and tetra(β-naphthyl)silane (TNS) as a hole-blocking layer (HBL). We find that the hole-blocking performance, thermal stability, and film-forming ability of TNS are improved over those of the prototypical hole-blocking material 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP). The device that used TNS as the HBL exhibits a narrower light emission and higher current efficiency (2.5cd∕A) as compared with the device containing BCP as the HBL. TNS should be promising as an excellent hole-blocking layer in LEDs.
Meiobenthos in intermittently open/closed coastal lakes in New South Wales: spatial and temporal patterns in densities of major taxa
Authors: Dye A. H.
Published: November 2005

Intermittently open/closed coastal lakes and lagoons (ICOLLs) are common in Australia. Isolation from the sea makes them susceptible to nutrient enrichment and pollution and many are considered degraded. Understanding of their ecology and the effects of anthropogenic activity is limited. Many lakes are kept open artificially to improve water quality and mitigate the effects of floods. The present study examined the relationship between multivariate and univariate patterns in higher taxa of meiobenthos and compared their densities and distributions in naturally open and closed lakes with those in managed lakes. The degree of correspondence between multivariate and univariate patterns was taxon and locality dependent. Differences in densities between types of lakes was not related to physical factors. Within lakes, meiobenthos generally correlated negatively with salinity and organic content, but positively with silt. Densities reflected the degree of isolation from the sea, but the influence of this factor varied among lakes within categories and between taxa. Most taxa were less abundant in isolated localities, such as the inner reaches of lakes and in closed lakes. Meiobenthos were more spatially variable in closed and in managed lakes. The influence of frequency and duration of closure on the ecology of coastal lakes is discussed.
Reproduction, diet and habitat use of leopard sharks, Triakis semifasciata (Girard), in Humboldt Bay, California, USA
Authors: Ebert David A. , Ebert Thomas B.
Published: November 2005

A total of 312 female leopard sharks (Triakis semifasciata) was sampled in Humboldt Bay, California, USA, an important nursery ground for this species, during the spring month of May from 1983 to 1984 and 1985. Sexual segregation is strong as only three males were observed in the study area. Females ranged in size from 120 to 154 cm total length, and all examined were determined to be mature. Overall, 130 out of 153 females examined in early May contained term embryos. The number of embryos per female ranged from 1 to 37 with larger females tending to possess more embryos. Of the 159 individuals examined in late May, no females were found carrying embryos and most were ovulating. Diet analyses revealed that, overall, fish eggs (Atherinopsis californiensis) at 48.0%, had the highest percentage Index of Relative Importance (%IRI), followed by the cancrid crabs, Cancer antennarius (29.8%) and C. magister (11.6%). All other prey were of relatively minor importance, cumulatively representing 10.6% of the overall diet. Adults shift their diet after parturition: early May sharks fed almost exclusively on fish eggs, while crabs were more important in those examined in late May.
Organic complexation of cobalt across the Antarctic Polar Front in the Southern Ocean
Authors: Ellwood Michael J. , van den Berg Constant M. G. , Boye Marie , Veldhuis Marcel , de Jong Jeroen T. M. , de Baar Hein J. W. , Croot Peter L. , Kattner Gerhard
Published: November 2005

There is compelling evidence to demonstrate that phytoplankton in major regions of the world’s oceans are limited by the availability of certain trace elements, notably iron. Cobalt concentrations in open-ocean waters generally range between 10 and 120 pmol L−1 but such levels were not thought to limit phytoplankton growth. Herein, we present data for total dissolved cobalt and cobalt-complexing ligands for two stations located south (station 200) and north (station 204) of the Antarctic Polar Front (APF) along 20°E in the South Atlantic sector of the Southern Ocean. Results indicate that there was little difference between total cobalt concentrations south and north of the APF, whereas ligand concentrations were significantly higher (15–20 pmol L−1) for the upper water column south of the APF. Productivity in these waters was low at the time of this study; however, numbers of large eukaryotic algal species were higher south of the APF, while north of the APF small eukaryotic and prokaryotic species dominated. The higher ligand concentrations measured at the southern station are probably related to higher algal numbers at this site. Because ligand concentrations were higher, inorganic cobalt concentrations (Co′) south of the APF are extremely low, at femtomolar levels, whereas north of the APF calculated Co′ are much higher at picomolar levels where ligand concentrations were lower.
Extracellular fluid volume, urine filtration rate and haemolymph mixing time in the abalone, Haliotis iris Martyn: a comparison of 51Cr-EDTA and 14C-inulin as extracellular markers
Authors: Taylor H. H. , Ragg N. L. C.
Published: November 2005

Measurement of extracellular fluid volume (ECFV, haemolymph or blood volume) of abalone is important for understanding respiratory and circulatory functions and for investigation of factors affecting meat recovery in the fishery. The compounds 14C-inulin and 51Cr-ethylenediaminetetraacetic acid (EDTA) were evaluated as markers for the determination of ECFV and primary urine formation (filtration) in New Zealand blackfoot abalone or paua, Haliotis iris. The volume of distribution of either marker reliably estimated ECFV after correction for clearance (56.6 ± 3.5 mL 100 g–1 soft tissue). 51Cr-EDTA was cleared from the haemolymph three to five times faster than 14C-inulin and was sequestered in the kidneys, digestive gland and mucous gland. 51Cr-EDTA was therefore unsuitable as a filtration marker. Urine filtration rate was best estimated from the appearance of inulin in the seawater (16.2 ± 2.1 mL 100 g–1 soft tissue day–1). The ECFV (inulin space) of isolated tissues ranged from 12–17 mL 100 g–1 tissue in the digestive gland, foot and adductor muscle to 60–70 mL 100 g–1 tissue in the kidneys, right ctenidium and epipodium. Equalisation of both markers between the efferent ctenidial vein and haemolymph lacunae of the shell adductor muscle occurred extremely slowly (t1/2 ~2 h, t0.95 ~8 h), confirming the poor perfusion of this anaerobic muscle.
Evidence for palatability variation between the sex phenotypes of bladder saltbush from small-plot grazing trials
Authors: Walsh D. , Andrew M. H. , Sinclair R. , Coleman D.
Published: November 2005

This paper reports the results of the first intensive grazing trials to study palatability variation between the sex phenotypes of bladder saltbush (Atriplex vesicaria Hew. ex Benth.). The results show that Merino sheep preferentially graze female shrubs over male and bisexual shrubs in South Australia, which supports earlier paddock-scale observations made in New South Wales. Male shrubs with higher densities of flower spikes were consumed less than those with lower densities. However, when male flowers were small and/or sparse, the removal of male flowers by clipping did not significantly increase the consumption of male shrubs. Female shrubs with very low or very high densities of fruit tended to be consumed significantly more than those with moderate fruit densities. Other physical aspects such as plant growth habit and foliage density did not have a consistent influence on grazing behaviour. Chemical differences between the sex phenotypes are implicated.
The presence of palatability variation between the sex phenotypes suggests that there is potential to refine the existing use of bladder saltbush as an indicator species in southern Australia.
Preliminary assessment of gidgee (Acacia cambagei) woodland thickening in the Longreach district, Queensland
Authors: Fensham R. J. , Fairfax R. J.
Published: November 2005

Gidgee (Acacia cambagei) forms woodlands and forests on moderately fertile clay soils throughout semi-arid areas of north-eastern Australia. Analysis of soil data from Queensland indicates that gidgee’s environmental domain has a broad overlap with treeless Mitchell grassland although a preference for slightly coarser soils with higher phosphorus and lower potassium content. Mapping of woody cover change for an area of central Queensland suggests that gidgee thickening and spread has occurred between 1951 and 1994. However, this increase has been more than offset by loss of gidgee cover by clearing in other areas. Gidgee thickening and encroachment onto grassland is a problem for graziers because the trees suppress grass and are unpalatable except when very young. Landholder surveys and other information indicate that gidgee has recruited sporadically and that thickening occurred with a massive seedling recruitment in the 1950s with a smaller recruitment wave in the 1970s. These waves coincide with relatively wet times and the extreme rainfall abundance in the 1950s has a multi-century expected recurrence. There are historical records describing gidgee death during the extreme droughts in the first part of the 20th century. Young gidgee plants are fire sensitive but well-established gidgee stands are fire retardant, and the importance of fire for control of gidgee thickening is unknown. One scenario explaining gidgee dynamics emphasises the role of environment (mostly climate and soil), while another emphasises management (mostly fire). Research priorities are presented and may contribute to appropriate management of gidgee woodlands.
Early experience in humans is associated with changes in neuropeptides critical for regulating social behavior
Authors: Fries Alison B. Wismer , Ziegler Toni E. , Kurian Joseph R. , Jacoris Steve , Pollak Seth D.
Published: November 2005

The formation of social attachments is a critical component of human relationships. Infants begin to bond to their caregivers from the moment of birth, and these social bonds continue to provide regulatory emotional functions throughout adulthood. It is difficult to examine the interactions between social experience and the biological origins of these complex behaviors because children undergo both brain development and accumulate social experience at the same time. We had a rare opportunity to examine children who were reared in extremely aberrant social environments where they were deprived of the kind of care-giving typical for our species. The present experiment in nature provides insight into the role of early experience on the brain systems underlying the development of emotional behavior. These data indicate that the vasopressin and oxytocin neuropeptide systems, which are critical in the establishment of social bonds and the regulation of emotional behaviors, are affected by early social experience. The results of this experiment suggest a potential mechanism whose atypical function may explain the pervasive social and emotional difficulties observed in many children who have experienced aberrant care-giving. The present findings are consistent with the view that there is a critical role for early experience in the development of the brain systems underlying basic aspects of human social behavior.
Negative regulation of
Salmonella
pathogenicity island 2 is required for contextual control of virulence during typhoid
Authors: Coombes Brian K. , Wickham Mark E. , Lowden Michael J. , Brown Nat F. , Finlay B. Brett
Published: November 2005

Salmonella enterica
relies on a type III secretion system encoded in
Salmonella
pathogenicity island-2 (SPI-2) to survive and replicate within macrophages at systemic sites during typhoid. SPI-2 virulence is induced upon entry into macrophages, but the mechanisms of SPI-2 gene control
in vivo
remain unclear, particularly with regard to negative regulators that control the contextual activation of SPI-2. Here, we identified and characterized YdgT as a negative modulator of the SPI-2 pathogenicity island and established that this negative regulation is central to systemic pathogenesis because
ydgT
mutants overexpressing typhoid virulence genes were ultimately attenuated during infection.
ydgT
mutants displayed a biphasic virulence phenotype during
in vivo
competitive infections that consisted of an early “gain-of-virulence” dependent on SPI-2 activation, followed by attenuation later in infection indicating that proper contextual regulation of SPI-2 by YdgT is necessary for full virulence during systemic colonization. These data suggest that overexpression of virulence-associated type III secretion genes can have an adverse effect on bacterial pathogenesis
in vivo
.
Knockout of caspase-like gene,
YCA1
, abrogates apoptosis and elevates oxidized proteins in
Saccharomyces cerevisiae
Authors: Khan Mohammed A. S. , Chock P. Boon , Stadtman Earl R.
Published: November 2005

In our previous study, we established that inhibition of apoptosis by the general caspase inhibitor is associated with an increase in the level of oxidized proteins in a multicellular eukaryotic system. To gain further insight into a potential link between oxidative stress and apoptosis, we carried out studies with
Saccharomyces cerevisiae
, which contains a gene (
YCA1
) that encodes synthesis of metacaspase, a homologue of the mammalian caspase, and is known to play a crucial role in the regulation of yeast apoptosis. We show that upon exposure to H
2
O
2
, the accumulation of protein carbonyls is much greater in a Δ
yca1
strain lacking the
YCA1
gene than in the wild type and that apoptosis was abrogated in the Δ
yca1
strain, whereas wild type underwent apoptosis as measured by externalization of phosphatidylserine and the display of TUNEL-positive nuclei. We also show that H
2
O
2
-mediated stress leads to up-regulation of the 20S proteasome and suppression of ubiquitinylation activities. These findings suggest that deletion of the apoptotic-related caspase-like gene leads to a large H
2
O
2
-dependent accumulation of oxidized proteins and up-regulation of 20S proteasome activity.
A data integration methodology for systems biology
Authors: Hwang Daehee , Rust Alistair G. , Ramsey Stephen , Smith Jennifer J. , Leslie Deena M. , Weston Andrea D. , de Atauri Pedro , Aitchison John D. , Hood Leroy , Siegel Andrew F. , Bolouri Hamid
Published: November 2005

Different experimental technologies measure different aspects of a system and to differing depth and breadth. High-throughput assays have inherently high false-positive and false-negative rates. Moreover, each technology includes systematic biases of a different nature. These differences make network reconstruction from multiple data sets difficult and error-prone. Additionally, because of the rapid rate of progress in biotechnology, there is usually no curated exemplar data set from which one might estimate data integration parameters. To address these concerns, we have developed data integration methods that can handle multiple data sets differing in statistical power, type, size, and network coverage without requiring a curated training data set. Our methodology is general in purpose and may be applied to integrate data from any existing and future technologies. Here we outline our methods and then demonstrate their performance by applying them to simulated data sets. The results show that these methods select true-positive data elements much more accurately than classical approaches. In an accompanying companion paper, we demonstrate the applicability of our approach to biological data. We have integrated our methodology into a free open source software package namedpointillist.
Probing conformational changes in T7 RNA polymerase during initiation and termination by using engineered disulfide linkages
Authors: Ma Kaiyu , Temiakov Dmitry , Anikin Michael , McAllister William T.
Published: November 2005

During the transition from an initiation complex to an elongation complex (EC), the single-subunit bacteriophage T7 RNA polymerase (RNAP) undergoes dramatic conformational changes. To explore the significance of these changes, we constructed mutant RNAPs that are able to form disulfide bonds that limit the mobility of elements that are involved in the transition (or its reversal) and examined the effects of the crosslinks on initiation and termination. A crosslink that is specific to the initiation complex conformation blocks transcription at 5–6 nt, presumably by preventing isomerization to an EC. A crosslink that is specific to the EC conformation has relatively little effect on elongation or on termination at a class I terminator (Tφ), which involves the formation of a stable stem–loop structure in the RNA. Crosslinked ECs also pause and resume transcription normally at a class II pause site (concatamer junction) but are deficient in termination at a class II terminator (PTH, which is found in human preparathyroid hormone gene), both of which involve a specific recognition sequence. The crosslinked amino acids in the EC lie close to the upstream end of the RNA–DNA hybrid and may prevent a movement of the polymerase that would assist in displacing or releasing RNA from a relatively unstable DNA–RNA hybrid in the paused PTH complex.
Acute Pulmonary Toxicity Caused by Exposure to Colloidal Silica: Particle Size Dependent Pathological Changes in Mice
Authors: Kaewamatawong Theerayuth , Kawamura Natsuko , Okajima Mina , Sawada Masumi , Morita Takehito , Shimada Akinori
Published: November 2005

To compare the pulmonary toxicity between ultrafine colloidal silica particles (UFCSs) and fine colloidal silica particles (FCSs), mice were intratracheally instilled with 3 mg of 14 nm UFCSs and 230 nm FCSs and pathologically examined from 30 minutes to 24 hour postexposure. Histopathologically, lungs exposed to both sizes of particles showed bronchiolar degeneration and necrosis, neutrophilic inflammation in alveoli with alveolar type II cell swelling and particle-laden alveolar macrophage accumulation. UFCSs, however, induced extensive alveolar hemorrhage compared to FCSs from 30 minutes onwards. UFCSs also caused more severe bronchiolar epithelial cell necrosis and neutrophil influx in alveoli than FCSs at 12 and 24 hours postexposure. Laminin positive immunolabellings in basement membranes of bronchioles and alveoli of UFCSs treated animals was weaker than those of FCSs-treated animals in all observation times. Electron microscopy demonstrated UFCSs and FCSs on bronchiolar and alveolar wall surface as well as in the cytoplasm of alveolar epithelial cells, alveolar macrophages and neutrophils. Type I alveolar epithelial cell erosion with basement membrane damage in UFCSs treated animals was more severe than those in FCSs-treated animals. At 12 and 24 hours postexposure, bronchiolar epithelial cells in UFCSs-treated animals showed more intense vacuolation and necrosis compared to FCSs-treated animals. These findings suggest that UFCSs have greater ability to induce lung inflammation and tissue damages than FCSs.
Sensory evoked potentials in infants with Down syndrome
Authors: CHEN YUNG‐JUNG , FANG PENG‐CHENG
Published: November 2005

Aim: To investigate the sensory functions of the peripheral to central pathways in infants with Down syndrome (DS) by sensory evoked potentials.

Methods: Fifty‐five infants, 30 DS infants and 25 controls, were examined by multimodal evoked potentials, including brainstem auditory evoked potentials (BAEP), visual evoked potentials (VEP) and short‐latency somatosensory evoked potentials (SSEP).

Results: No obvious difference was found in the peak latencies between the two groups for BAEP. Nine children with DS showed abnormal BAEP; six had hearing loss and three had prolonged wave I latencies. For VEP, the peak latencies of P2 and N2 were significantly longer and the amplitudes were smaller in the DS group than in the control group. Of the 30 infants with DS, five had significantly prolonged P2 latencies and two had lower amplitudes. In SSEP, the mean latencies of N20 and the interpeak latencies of N13‐N20 of the infants with DS showed apparent prolongation compared to the controls. Seven of 30 (23.3%) DS patients had prolonged N20 latencies.

Conclusion: Our results indicate that various sensory deficits occur in patients with DS during the first year of life.
Breastfeeding and school achievement in Brazilian adolescents
Authors: VICTORA CESAR G. , BARROS FERNANDO C. , HORTA BERNARDO L. , LIMA ROSÂNGELA C.
Published: November 2005

Aim: To assess the effect of breastfeeding duration on school achievement in a Brazilian cohort.

Methods: In a population‐based birth cohort, we analysed the highest grade achieved in school of over 2000 male 18‐y‐olds relative to breastfeeding information collected in early life. Analyses were adjusted for birthweight, family income, maternal and paternal schooling, household assets, number of siblings, social class, maternal smoking during pregnancy, and ethnicity.

Results: After adjustment for confounding variables, there was a highly significant trend in school achievement with increasing breastfeeding duration. Those breastfed for 9 mo or more were ahead by 0.5–0.8 school grades, relative to those breastfed for less than 1 mo. Data from a cross‐sectional survey in the same population suggest that such a difference corresponds to a 10–15% difference in adult income levels. The duration of exclusive or predominant breastfeeding was also positively associated with schooling.

Conclusion: Unlike studies from developed countries, there was no clear association between breastfeeding duration and either the family's socio‐economic level or parental schooling in our sample and therefore residual confounding is improbable. These results suggest that the impact of breastfeeding on intellectual development may lead to sizeable differences in adult education and wage‐earning performance.
Graves' disease in children and adolescents: Response to long‐term treatment
Authors: BARRIO RAQUEL , LÓPEZ‐CAPAPÉ MARTA , MARTINEZ‐BADÁS ITZIAR , CARRILLO ANGEL , MORENO JOSE C. , ALONSO MILAGROS
Published: November 2005

Background: Optimal treatment of Graves' disease in paediatric patients is still a matter of controversy. Antithyroid drugs, radioiodine and thyroidectomy are the three therapeutic options available. Aim: To report our experience of long‐term medical treatment and outcome of paediatric Graves' disease.

Methods: A 5‐y‐long medical protocol was implemented in 20 children and adolescents with Graves' disease. All patients received antithyroid drugs as the first therapeutic option; patients who did not enter long‐term remission received I131 and/or surgery as the definitive treatment.

Results: The mean age at diagnosis was 12.1±4 y. Only two patients were males, both presenting concomitant type 1 diabetes. Mean follow‐up was 13.8 ± 5.5 y. Forty per cent of patients achieved long‐term remission with low antithyroid drugs doses (mean treatment time: 5.4± 1.4 y). Six patients received I131 as definitive treatment and another six underwent surgery after completing medical treatment for 6.8 ± 4.1 and 5.1 ± 2 y, respectively. No patients requiring high antithyroid drugs doses to maintain euthy‐roidism reached long‐term remission and needed I131 and/or surgery.

Conclusion: Implementation of a long‐term antithyroid drug protocol achieved 40% long‐term remissions in paediatric patients with Graves' disease. Need for maintained high doses of antithyroid drugs could be considered a predictive factor for no remission. When permanent remission was not obtained by medical treatment, I131 and/or surgery allowed healing in all cases.
Changes in shape and location of BMI distributions of Swedish children
Authors: ERIKSSON MARIT , RASMUSSEN FINN , NORDQVIST TOBIAS
Published: November 2005

Aims: One aim was to disentangle how the shape and location of the BMI distribution changed among Swedish children over a 12 y period. Another aim was to identify the age during childhood when changes occurred or became manifest.

Methods: Two population‐based cohorts—2591 children from Stockholm born 1985–1987 and 3650 from Gothenburg born 1973–1975—were compared with respect to BMI distributions from 2 to 15 y of age.

Results: Differences between the BMI distributions of the two cohorts were present from 5–6 y of age. From age 7, the children born in 1985–1987 and belonging to the upper parts of the BMI distribution, e.g. those above the 90th or 95th BMI percentiles, had much higher BMI mean values compared to their counterparts born 12 y earlier. Comparisons with respect to the 5th, 10th, 25th, 50th, 75th, 90th and 95th BMI percentiles showed that changes appeared above the 25th percentile and became increasingly pronounced in the upper parts of the BMI distributions.

Conclusion: School‐aged children in the rightmost parts of the BMI distributions may be more susceptible to “obesogenic” environmental exposures than those in the middle or leftmost parts. The results support the suggestion that the period of BMI rebound is critical for the development of obesity.
Troponin‐T levels in perinatally asphyxiated infants during the first 15 days of life
Authors: GÜNES TAMER , ÖZTÜRK M. ADNAN , KÖKLÜ SELMIN MURADALDI , NARIN NAZMI , KÖKLÜ ESAD
Published: November 2005

Aim: To measure serial cardiac troponin‐T, creatine kinase, creatine kinase‐MB, aspartate aminotransferase, alanine aminotransferase and lactate dehydrogenase levels in asphyxiated newborn infants during the first 15 d of life.

Methods: Troponin‐T, creatine kinase, creatine kinase‐MB, aspartate aminotransferase, alanine aminotransferase and lactate dehydrogenase (LDH) concentrations were measured prospectively in blood samples obtained from 45 asphyxiated and 15 healthy term neonates within the first 2–4 h, third, seventh and 15th days.

Results: Infants with severe asphyxia had significantly higher cardiac troponin‐T levels than grade I and II asphyxiated and healthy neonates within the first 2–4 h of life (0.34 ± 0.21 ag/ml vs 0.07 ± 0.03 ag/ml, 0.12 ± 0.07 ag/ml, 0.04 ± 0.02 ag/ml, respectively). Troponin‐T levels remained high on days 3 and 7 in severely asphyxiated neonates. The creatinine kinase‐MB levels were significantly higher in grade II and III asphyxiated neonates than grade I asphyxiated and healthy neonates within the first 2–4 h. No difference was found in creatinine kinase‐MB on day 3. There was cardiac involvement in 12 (80%) newborns of group III on B mode echocardiographic images on day 1. However, no echocardigraphic pathology was found in the seventh‐ and 15th‐day echocardiographic analysis in any groups.

Conclusion: Our results suggest that asphyxia‐related cardiac changes were significant but reversible in severely asphyxiated neonates, and troponin T is a good determinant of the degree of injury to the heart within the first week of life. Cardiac troponin T also has a wider diagnostic frame than other diagnostic markers of myocardial damage.