bluuebunny/crossref_metadata_2025 huggingface dataset:
Concentrations and sources of organic carbon aerosols in the free troposphere over North America
Authors: Heald Colette L. , Jacob Daniel J. , Turquety Solène , Hudman Rynda C. , Weber Rodney J. , Sullivan Amy P. , Peltier Richard E. , Atlas Eliot L. , de Gouw Joost A. , Warneke Carsten , Holloway John S. , Neuman J. Andrew , Flocke Frank M. , Seinfeld John H.
Published: December 2006

Aircraft measurements of water‐soluble organic carbon (WSOC) aerosol over NE North America during summer 2004 (ITCT‐2K4) are simulated with a global chemical transport model (GEOS‐Chem) to test our understanding of the sources of organic carbon (OC) aerosol in the free troposphere (FT). Elevated concentrations were observed in plumes from boreal fires in Alaska and Canada. WSOC aerosol concentrations outside of these plumes average 0.9 ± 0.9 μg C m−3 in the FT (2–6 km). The corresponding model value is 0.7 ± 0.6 μg C m−3, including 42% from biomass burning, 36% from biogenic secondary organic aerosol (SOA), and 22% from anthropogenic emissions. Previous OC aerosol observations over the NW Pacific in spring 2001 (ACE‐Asia) averaged 3.3 ± 2.8 μg C m−3 in the FT, compared to a model value of 0.3 ± 0.3 μg C m−3. WSOC aerosol concentrations in the boundary layer (BL) during ITCT‐2K4 are consistent with OC aerosol observed at the IMPROVE surface network. The model is low in the boundary layer by 30%, which we attribute to secondary formation at a rate comparable to primary anthropogenic emission. Observed WSOC aerosol concentrations decrease by a factor of 2 from the BL to the FT, as compared to a factor of 10 decrease for sulfate, indicating that most of the WSOC aerosol in the FT originates in situ. Despite reproducing mean observed WSOC concentrations in the FT to within 25%, the model cannot account for the variance in the observations (R = 0.21). Covariance analysis of FT WSOC aerosol with other measured chemical variables suggests an aqueous‐phase mechanism for SOA generation involving biogenic precursors.
Effects of treatment with a 5‐HT4receptor antagonist in heart failure
Authors: Birkeland J A K , Sjaastad I , Brattelid T , Qvigstad E , Moberg E R , Krobert K A , Bjørnerheim R , Skomedal T , Sejersted O M , Osnes J‐B , Levy F O
Published: December 2006

Background and purpose:

Positive inotropic responses (PIR) to 5‐hydroxytryptamine (5‐HT) are induced in the left ventricle (LV) in rats with congestive heart failure (CHF); this is associated with upregulation of the Gs‐coupled 5‐HT4receptor. We investigated whether chronic 5‐HT4receptor blockade improved cardiac function in CHF rats.

Experimental approach:

Rats were given either the 5‐HT4antagonist SB207266 (0.5 mg kg−124h−1; MIint) or placebo (MIpl) through mini‐osmotic pumps for 6 weeks subsequent to induction of post‐infarction CHF.In vivocardiac function andex vivoresponses to isoprenaline or 5‐HT were evaluated using echocardiography and isolated LV papillary muscles, respectively. mRNA levels were investigated using real‐time quantitative RT‐PCR.

Key results:

LV diastolic function improved, with 4.6% lower LV diastolic diameter and 24.2% lower mitral flow deceleration in MIintcompared to MIpl. SB207266 reduced LV systolic diameter by 6.1%, heart weight by 10.2% and lung weight by 13.1%. The changes in posterior wall thickening and shortening velocity, cardiac output, LV systolic pressure and (dP/dt)max, parameters of LV systolic function, did not reach statistical significance. The PIR to isoprenaline (10 μM) increased by 36% and the response to 5‐HT (10 μM) decreased by 57% in MIintcompared to MIpl. mRNA levels for ANP, 5‐HT4(b)and 5‐HT2Areceptors, MHCβ, and the MHCβ/MHCα‐ratio were not significantly changed in MIintcompared to MIpl.

Conclusions and implications:

Treatment with SB207266 to some extent improvedin vivocardiac function andex vivomyocardial function, suggesting a possible beneficial effect of treatment with a 5‐HT4receptor antagonist in CHF.

British Journal of Pharmacology(2007)150, 143–152. doi:10.1038/sj.bjp.0706966
Phospholipid scramblase-3 regulates cardiolipin de novo biosynthesis and its resynthesis in growing HeLa cells
Authors: Van Quyen , Liu Jihua , Lu Biao , Feingold Kenneth R. , Shi Yuguang , Lee Ray M. , Hatch Grant M.
Published: December 2006

PLS3 (phospholipid scramblase-3) is a new member of the family of phospholipid scramblases and transports CL (cardiolipin) from the inner to the outer mitochondrial membrane. In the present paper we examined whether changing the levels of functional PLS3 in HeLa cells altered de novo CL biosynthesis and its resynthesis. HeLa cells overexpressing PLS3 or expressing a disrupted PLS3 (F258V) or control were incubated with [1,3-3H]glycerol and radioactivity incorporated into CL was determined. CL biosynthesis from [1,3-3H]glycerol was increased 1.8-fold in PLS3 cells and 2.1-fold in F258V cells compared with control. This was due to a 64% (P<0.05) and 2.6-fold (P<0.05) elevation in CL synthase activity in PLS3 and F258V cells respectively, compared with control, and not due to changes in phosphatidylglycerolphosphate synthase activity. The increase in CL synthase activity in these cells was due to an increase in its mRNA expression. In contrast, resynthesis of CL from [1-14C]linoleic acid was reduced 52% (P<0.05) in PLS3 and 45% (P<0.05) in F258V cells compared with control and this was due to a reduction in mitochondrial monolysocardiolipin acyltransferase activity. Although protein levels of mitochondrial monolysocardiolipin acyltransferase were unaltered, activity and mRNA expression of endoplasmic reticulum monolysocardiolipin acyltransferase was upregulated in PLS3 and F258V cells compared with controls. These data indicate that the CL resynthesis in HeLa cells is sensitive to the mitochondrial localization of CL and not the level of the reacylating enzymes. Alterations in functional PLS3 levels in PLS3 or F258V cells did not affect the mitochondrial decarboxylation of phosphatidylserine to phosphatidylethanolamine indicating that the biosynthetic changes to CL were specific for this mitochondrial phospholipid. We hypothesize that the cardiolipin resynthesis machinery in the cell ‘senses’ altered levels of CL on mitochondrial membranes and that de novo CL biosynthesis is up-regulated in HeLa cells as a compensatory mechanism in response to altered movement of mitochondrial CL. The results identify PLS3 as a novel regulator of CL de novo biosynthesis and its resynthesis.
Presenilin/γ-secretase and α-secretase-like peptidases cleave human MHC Class I proteins
Authors: Carey Bryce W. , Kim Doo Y. , Kovacs Dora M.
Published: December 2006

HLA (human leucocyte antigen)-A2 is an MHC Class I protein with primary functions in T-cell development and initi-ation of immune cell responses. MHC I proteins also play roles in intercellular adhesion, apoptosis, cell proliferation and neuronal plasticity. By utilizing a sequence comparison analysis, we recently identified HLA-A2 as a potential substrate for the Alzheimer's disease-associated PS1 (presenilin 1)/γ-secretase. α-Secretase-like membrane metalloproteinases are responsible for an initial shedding event, partially mediated by ADAM (a disinteg-rin and metalloproteinase)-10. Accordingly, activation or inhibition of α-secretase-like membrane metalloproteinases directly modulated levels of a 14 kDa HLA-A2 CTF (C-terminal frag-ment) in CHO (Chinese-hamster ovary) cells. To show that the HLA-A2 CTF is subsequently cleaved by PS1/γ-secretase, we re-duced its activity in cell lines stably expressing HLA-A2 and in Jurkat T-cells expressing endogenous MHC I. Treatment with specific PS1/γ-secretase inhibitors or expression of a dominant-negative construct led to a significant accumulation of HLA-A2 CTFs. We also identified the PS1/γ-secretase cleavage product of HLA-A2 CTF, termed HLA-A2 intracellular domain, in cell-free and cell-based experiments. In the absence of proteasome inhibitors, HLA-A2 intracellular domain underwent rapid degrad-ation. These data indicate that MHC I proteins undergo extra-cellular domain cleavage mediated by α-secretases and the cleavage product is subsequently cleaved by PS1/γ-secretase.
Oxidative stress and cancer: have we moved forward?
Authors: Halliwell Barry
Published: December 2006

‘Reactive species’ (RS) of various types are formed in vivo and many are powerful oxidizing agents, capable of damaging DNA and other biomolecules. Increased formation of RS can promote the development of malignancy, and the ‘normal’ rates of RS generation may account for the increased risk of cancer development in the aged. Indeed, knockout of various antioxidant defence enzymes raises oxidative damage levels and promotes age-related cancer development in animals. In explaining this, most attention has been paid to direct oxidative damage to DNA by certain RS, such as hydroxyl radical (OH•). However, increased levels of DNA base oxidation products such as 8OHdg (8-hydroxy-2′-deoxyguanosine) do not always lead to malignancy, although malignant tumours often show increased levels of DNA base oxidation. Hence additional actions of RS must be important, possibly their effects on p53, cell proliferation, invasiveness and metastasis. Chronic inflammation predisposes to malignancy, but the role of RS in this is likely to be complex because RS can sometimes act as anti-inflammatory agents.
Hypoxia-induced assembly of prolyl hydroxylase PHD3 into complexes: implications for its activity and susceptibility for degradation by the E3 ligase Siah2
Authors: Nakayama Koh , Gazdoiu Stefan , Abraham Robert , Pan Zhen-Qiang , Ronai Ze'ev
Published: December 2006

PHD1–3 (prolyl hydroxylases 1–3) catalyse the hydroxylation of HIF (hypoxia-inducible factor)-α subunit that triggers the substrate ubiquitination and subsequent degradation. The RING (really interesting new gene) finger E3 ligase Siah2 preferentially targets PHD3 for degradation. Here, we identify the requirements for such selective targeting. Firstly, PHD3 lacks an N-terminal extension found in PHD1 and PHD2; deletion of this domain from PHD1 and PHD2 renders them susceptible to degradation by Siah2. Secondly, PHD3 can homo- and hetero-multimerize with other PHDs. Consequently, PHD3 is found in high-molecular-mass fractions that were enriched in hypoxia. Interestingly, within the lower-molecular-mass complex, PHD3 exhibits higher specific activity towards hydroxylation of HIF-1α and co-localizes with Siah2, suggesting that Siah2 limits the availability of the more active form of PHD3. These findings provide new insight into the mechanism underlying the regulation of PHD3 availability and activity in hypoxia by the E3 ligase Siah2.
New mechanisms and targets in the treatment of bone fragility
Authors: Martin T. John , Seeman Ego
Published: December 2006

Bone modelling and remodelling are cell-mediated processes responsible for the construction and reconstruction of the skeleton throughout life. These processes are chiefly mediated by locally generated cytokines and growth factors that regulate the differentiation, activation, work and life span of osteoblasts and osteoclasts, the cells that co-ordinate the volumes of bone resorbed and formed. In this way, the material composition and structural design of bone is regulated in accordance with its loading requirements. Abnormalities in this regulatory system compromise the material and structural determinants of bone strength producing bone fragility. Understanding the intercellular control processes that regulate bone modelling and remodelling is essential in planning therapeutic approaches to prevention and treatment of bone fragility. A great deal has been learnt in the last decade. Clinical trials carried out exclusively with drugs that inhibit bone resorption have identified the importance of reducing the rate of bone remodelling and so the progression of bone fragility to achieved fracture reductions of approx. 50%. These trials have also identified limitations that should be placed upon interpretation of bone mineral density changes in relation to treatment. New resorption inhibitors are being developed, based on mechanisms of action that are different from existing drugs. Some of these might offer resorption inhibition without reducing bone formation. More recent research has provided the first effective anabolic therapy for bone reconstruction. Daily injections of PTH (parathyroid hormone)-(1–34) have been shown in preclinical studies and in a large clinical trial to increase bone tissue mass and reduce the risk of fractures. The action of PTH differs from that of the resorption inhibitors, but whether it is more effective in fracture reduction is not known. Understanding the cellular and molecular mechanisms of PTH action, particularly its interactions with other pathways in determining bone formation, is likely to lead to new therapeutic developments. The recent discovery through mouse genetics that PTHrP (PTH-related protein) is a crucial bone-derived paracrine regulator of remodelling offers new and interesting therapeutic targets.
Diet, obesity and diabetes: a current update
Authors: Walker Celia G. , Zariwala M. Gulrez , Holness Mark J. , SUGDEN Mary C.
Published: December 2006

The prevalence of obesity has been increasing at a rapid rate over the last few decades. Although the primary defect can be attributed to an imbalance of energy intake over energy expenditure, the regulation of energy balance is now recognized to be complex. Adipose-tissue factors play a central role in the control of energy balance and whole-body fuel homoeostasis. The regulation of adipose-tissue function, in particular its secretion of adipokines, is impaired by increases in adipose mass associated with obesity, and with the development of insulin resistance and Type 2 diabetes. This review analyses adipose-regulated energy input and expenditure, together with the impact of dietary macronutrient composition on energy balance in relation to susceptibility to the development of obesity and Type 2 diabetes, and how these metabolic conditions may be exacerbated by the consequences of abnormal adipose function. By gaining a greater understanding of how energy balance is controlled in normal, and in obese and diabetic states, a more practical approach can be employed to prevent and better treat obesity and metabolic disorders.
III-VI compound semiconductor indium selenide (In2Se3) nanowires: Synthesis and characterization
Authors: Sun Xuhui , Yu Bin , Ng Garrick , Nguyen Thuc Dinh , Meyyappan M.
Published: December 2006

The authors report the synthesis of one-dimensional indium selenide nanowire, a III-VI group compound semiconductor nanostructure with potential applications in data storage, solar cells, and optoelectronics. Nanoscale gold particles were used as catalysts and growth was also demonstrated using indium as self-catalyst. The growth mechanism is confirmed to be vapor-liquid-solid process by in situ heating experiments in which In and Se were found to diffuse back into the gold catalyst bead forming a Au–In–Se alloy that was molten at elevated temperatures. The morphology, composition, and crystal structure of the In2Se3 nanowires (NWs) were analyzed by scanning electron microscopy, energy dispersive x-ray spectroscopy, and high-resolution transmission electron microscopy.
Sharp bursts of high-flux reactive species in submicrosecond atmospheric pressure glow discharges
Authors: Walsh J. L. , Kong M. G.
Published: December 2006

In this letter, the authors present an experimental study of the temporal characteristics of submicrosecond pulsed atmospheric glow discharges. Using electrical measurements and nanosecond-resolved optical emission spectroscopy, they show that a long initial period of each voltage pulse is spent building up space charges and is then followed by a large current pulse in the voltage-falling phase. Reactive plasma species such as oxygen atoms and OH radicals are produced in a train of sharp and independent pulses of 50–100ns wide. Finally, their production is shown to increase significantly as the voltage pulse width reduces or the repetition frequency increases.
Speed of sound instrument for fluids with pressures up to 100 MPa
Authors: Meier Karsten , Kabelac Stephan
Published: December 2006

An instrument for highly accurate measurements of the speed of sound in fluids in the temperature range between 240 and 420 K with pressures up to 100 MPa is described. The measurement principle of the speed of sound sensor is based on a double path length pulse-echo technique. The achieved measurement uncertainties are 3 mK for the temperature, 0.01% for the pressure below 10 MPa and 0.005% for the pressure between 10 and 100 MPa, and 0.014% for the speed of sound. The high accuracy of the instrument is demonstrated by measurements in liquid water and compressed argon. The results for argon prove that our pulse-echo technique agrees with the highly accurate spherical resonator technique, which is commonly employed for speed of sound measurements in gases, in the pressure range where both methods overlap within our measurement uncertainty.
Angular momentum dependent friction slows down rotational relaxation under nonequilibrium conditions
Authors: Gelin M. F. , Kosov D. S.
Published: December 2006

It has recently been shown that relaxation of the rotational energy of hot nonequilibrium photofragments (i) slows down significantly with the increase of their initial rotational temperature and (ii) differs dramatically from the relaxation of the equilibrium rotational energy correlation function, manifesting thereby the breakdown of the linear response description [A. C. Moskun et al., Science 311, 1907 (2006)]. We demonstrate that this phenomenon may be caused by the angular momentum dependence of rotational friction. We have developed the generalized Fokker–Planck equation whose rotational friction depends upon angular momentum algebraically. The calculated rotational correlation functions correspond well to their counterparts obtained via molecular dynamics simulations in a broad range of initial nonequilibrium conditions. It is suggested that the angular momentum dependence of friction should be taken into account while describing rotational relaxation far from equilibrium.
High-frequency shear Alfvén instability driven by circulating energetic ions in NSTX
Authors: Kolesnichenko Ya. I. , White R. B. , Yakovenko Yu. V.
Published: December 2006

It is shown that a number of features of an instability with the frequency comparable to the ion gyrofrequency observed in the National Spherical Torus Experiment [E. D. Fredrickson et al., “Observation of hole-clump pair generation by global or compressional Alfvén eigenmodes,” Contributed Papers, 33rd European Physical Society Conference on Plasma Physics, Rome, 2006, Europhysics Conference Abstracts (European Physical Society, Petit-Lancy, 2006), Report P5.058 (unpublished)] is consistent with the features of the Alfvén instability with large, about the inverse, Larmor radius of the energetic ions (ρb−1) longitudinal wavenumbers. The conclusions drawn are based on an analysis of the resonant interaction of the energetic circulating ions and the waves, as well as on the calculation of the instability growth rate taking into account effects of the finite Larmor radius, ρb.
Calculation of the absolute thermodynamic properties of association of host-guest systems from the intermolecular potential of mean force
Authors: Ghoufi Aziz , Malfreyt Patrice
Published: December 2006

The authors report calculations of the intermolecular potential of mean force (PMF) in the case of the host-guest interaction. The host-guest system is defined by a water soluble calixarene and a cation. With an organic cation such as the tetramethylammonium cation, the calixarene forms an insertion complex, whereas with the Lanthane cation, the supramolecular assembly is an outer-sphere complex. The authors apply a modified free energy perturbation method and the force constraint technique to establish the PMF profiles as a function of the separation distance between the host and guest. They use the PMF profile for the calculation of the absolute thermodynamic properties of association that they compare to the experimental values previously determined. They finish by giving some structural features of the insertion and outer-sphere complexes at the Gibbs free energy minimum.
Resonant tunneling magnetoresistance in coupled quantum wells
Authors: Ertler Christian , Fabian Jaroslav
Published: December 2006

A three barrier resonant tunneling structure in which the two quantum wells are formed by a magnetic semiconductor is theoretically investigated. Self-consistent numerical simulations of the structure predict giant magnetocurrent in the resonant bias regime as well as significant current spin polarization for a considerable range of applied biases. The requirements for large magnetocurrent are spin resolved resonance levels as well as asymmetry (spatial or magnetic) of the coupled quantum wells.
Wavelength-tunable and thermally stable Li-α-sialon:Eu2+ oxynitride phosphors for white light-emitting diodes
Authors: Xie Rong-Jun , Hirosaki Naoto , Mitomo Mamoru , Sakuma Ken , Kimura Naoki
Published: December 2006

Eu 2 + -activated Li-α-sialon is a promising yellow phosphor for white light-emitting diodes (LEDs). This letter reports that the emission of Eu2+ in Li-α-sialon can be tuned widely (563–586nm) by tailoring the composition or controlling the Eu2+ concentration. The thermal stability of Li-α-sialon:Eu2+, relying a little on the composition and the Eu2+ concentration, remains high in a wide temperature range (25–200°C). Moreover, the chromaticity of Li-α-sialon:Eu2+ does not shift with changes in temperature. Using a single Li-α-sialon:Eu2+ phosphor, highly efficient white LEDs (46–55lm∕W) with different color temperatures (3000–5200K) can be fabricated.
Writing and erasing information in multilevel logic systems of a single molecule using scanning tunneling microscope
Authors: Bandyopadhyay Anirban , Miki K. , Wakayama Y.
Published: December 2006

Large double negative differential resistance (NDR) has enabled a single quinone derivative to be stable in the neutral (0), singly reduced (1), typical neutral conformation generated by releasing the charge (2), and doubly reduced state (3) at 90K. The authors wrote and erased information by switching a single molecule among these four conducting states (0,1,2,3) showing random access memory and read only memory applications for terabit memory generation in future. Origin of NDR is investigated in typical functional groups of the molecule, in local environment, and at atomic junction with scanning-tunneling-microscope tip to conclude NDR as a collective phenomenon.
Realization of a high capacitance density in Bi2Mg2∕3Nb4∕3O7 pyrochlore thin films deposited directly on polymer substrates for embedded capacitor applications
Authors: Park Jong-Hyun , Xian Cheng-Ji , Seong Nak-Jin , Yoon Soon-Gil , Son Seung-Hyun , Chung Hyung-Mi , Moon Jin-Suck , Jin Hyun-Joo , Lee Seung-Eun , Lee Jeong-Won , Kang Hyung-Dong , Chung Yeoul-Kyo , Oh Yong-Soo
Published: December 2006

Bi 2 Mg 2 ∕ 3 Nb 4 ∕ 3 O 7 (BMN) thin films were deposited on copper clad laminate substrates at temperatures below 150°C for embedded capacitor applications by pulsed laser deposition. The BMN films deposited at temperatures below 150°C showed smooth surface morphologies having root mean square roughness of approximately 3.0nm. 130-nm-thick films deposited at 150°C exhibit a dielectric constant of 47, a capacitance density of approximately 302nF∕cm2, and breakdown strength of 0.7MV∕cm. The origin exhibiting high dielectric constant in BMN films deposited at low temperatures was attributed to the nanocrystallines having grain sizes of approximately 4.0nm in the films. The low temperature processed-BMN films are suitable candidate for capacitor applications embodied directly on printed circuit board substrates.
Property enhancement of optically transparent bionanofiber composites by acetylation
Authors: Nogi Masaya , Abe Kentaro , Handa Keishin , Nakatsubo Fumiaki , Ifuku Shinsuke , Yano Hiroyuki
Published: December 2006

The authors studied acetylation of bacterial cellulose (BC) nanofibers to widen the applications of BC nanocomposites in optoelectronic devices. The slight acetylation of BC nanofibers significantly reduces the hygroscopicity of BC nanocomposites, while maintaining their high optical transparency and thermal stability. Furthermore, the degradation in optical transparency at elevated temperature (200°C) was significantly reduced by acetylation treatment. Therefore, the acetylation of bionanofibers has an extraordinary potential as treatment for property enhancement of bionanofiber composites.
Surface pole figures by reflection high-energy electron diffraction
Authors: Tang F. , Wang G.-C. , Lu T.-M.
Published: December 2006

The authors demonstrated that it is possible to construct a reflection high-energy electron diffraction (RHEED) pole figure of a polycrystalline film by recording multiple RHEED patterns as they rotate the substrate around the surface normal. Since electrons have limited penetration depth, the pole figure constructed is a surface pole figure. It is in contrast with the conventional x-ray pole figure which gives an average texture information of the entire film. Surface texture change, particularly the evolution of multiple preferred orientations, in polycrystalline Ru films grown by oblique angle vapor deposition has been observed using this RHEED surface pole figure technique.
Ferroelectric properties and poling of BaMgF4 for ultraviolet all solid-state lasers
Authors: Shimamura Kiyoshi , Víllora Encarnación G. , Zeng Huarong , Nakamura Masaru , Takekawa Shunji , Kitamura Kenji
Published: December 2006

The ferroelectric properties of bulk BaMgF4 are determined by polarization hysteresis measurements. The spontaneous polarization Ps is found to be 6.6μC∕cm2, while the coercive field Ec varies between 4 and 24kV∕cm, depending exponentially on the frequency. Periodical poling of domains, with a 24μm period, is demonstrated and evidenced by a selective domain etching.
Amplitude compensation of a diode laser array phase locked with a Talbot cavity
Authors: Li Qiang , Zhao Pengfei , Guo Weirong
Published: December 2006

Phase locking of the output beam and in-phase mode selection with the amplitude compensator at a high injection current were achieved experimentally by a quarter-Talbot cavity. The linear array used in the experiment consisted of 49 wide-aperture diodes with a diode width of a=100μm and a spacing period of d=200μm. Increasing output beam intensity in the far-field central lobe was demonstrated, and 1.46W of output power distributed on the multilobes was concentrated on the single lobe and changed to 0.92W by the amplitude compensator. The far-field divergence of the phase-locked beam was 1.69mrad, and the spectral full width at half maximum of the output beam was suppressed from 1.7to0.13nm.
Structure and photoluminescence properties of epitaxially oriented GaN nanorods grown on Si(111) by plasma-assisted molecular-beam epitaxy
Authors: Chen Hung-Ying , Lin Hon-Way , Shen Chang-Hong , Gwo Shangjr
Published: December 2006

The authors show that vertically c-axis-aligned GaN nanorod arrays grown by plasma-assisted molecular-beam epitaxy are epitaxially oriented on Si(111) substrates and their crystal structure corresponds to a fully relaxed wurtzite lattice. At later growth stage, these GaN nanorods exhibit the tendency to coalesce into nanorod bundles. Low-temperature photoluminescence spectrum from 1-μm-long GaN nanorods consists of intense exciton lines of strain-free bulk GaN and additional lines at ∼3.21 and ∼3.42eV (Y7 and Y2). The Y7 line is attributed to the excitons trapped along the dislocations at the boundaries of coalesced GaN nanorods, while the Y2 line has its origin in the interface defects at the GaN∕Si(111) interfaces.
Magnetic properties of ZnMnO nanopowders solvothermally grown at low temperature from zinc and manganese acetate
Authors: Tomaszewska-Grzȩda A. , Opalińska A. , Grzanka E. , Łojkowski W. , Gedanken A. , Godlewski M. , Yatsunenko S. , Osinniy V. , Story T.
Published: December 2006

The authors demonstrate that nanometer size ZnMnO nanopowders, grown from zinc and manganese (II) acetates at low temperatures under microwave radiation, are free of Mn clusters and the inclusion of Mn oxides. These nanopowders show a strong paramagnetic phase with only a weak antiferromagnetic contribution due to Mn–Mn interactions.
Compact dye laser on a chip fabricated by ultraviolet nanoimprint lithography
Authors: Peroz Ch. , Galas J-C. , Le Gratiet L. , Chen Y. , Shi J.
Published: December 2006

High aspect ratio and high resolution distributed feed back (DFB) gratings have been patterned on a fused silica plate by ultraviolet nanoimprint lithography and reactive ion etch techniques. Then, they were integrated into a microfluidic chip for optofluidic operations. The authors observed laser emission from organic dye solutions flowing through an optical resonator formed between two third order DFB gratings. Such a dye layer can operate with a picoliter dye solution. With rhodamine 6G dye molecules dissolved in ethanol and pumped by a frequency-doubled Nd:YAG pulsed laser, a laser emission of threshold of 12μJ∕mm2 has been found.
Charging and Coulomb staircase effects in silicon nanodisk structures fabricated by defect-free Cl neutral beam etching process
Authors: Kubota Tomohiro , Hashimoto Takeshi , Ishikawa Yasushi , Samukawa Seiji , Miura Atsushi , Uraoka Yukiharu , Fuyuki Takashi , Takeguchi Masaki , Nishioka Kensuke , Yamashita Ichiro
Published: December 2006

A defect-free nanometer-scale silicon disk (nanodisk) on thin SiO2 film was precisely fabricated by using Cl neutral beam etching of a 3.5–4-nm-thick polycrystalline silicon on 1.4–3-nm-thick underlying SiO2 with a 7-nm-diameter ferritin iron core mask. Kelvin force microscope observations revealed that nanodisks could maintain injected positive and negative charges. Additionally, Coulomb staircases were observed by I-V measurement of a nanodisk at a temperature of 25K. These results indicate that the nanodisk fabricated in this research had a precise quantum effect structure and attained the single electron property. This process has great potential in the development of future quantum effect devices.
Modulating transmission properties of nanoscale transistors by dipoles near contacts
Authors: Yang Li , Wu Jian , Duan Wenhui , Gu Bing-Lin
Published: December 2006

The authors theoretically demonstrate that dipole layers on the electrode can modulate the transmission properties of nanoscale devices by influencing the contact properties, through first principles simulations on carbon nanotube based field effect transistors. The dipole layers are realized by potassium adsorption on Au electrodes, which change the electrostatic potential at the near contact region significantly. The dipoles parallel to the direction of the bias voltage may act as a supplement to the effect of gate voltages, while the perpendicular dipoles modify the interface barrier of contacts.
Demonstration and dynamic analysis of trapping of hot electrons at gate edge model for current collapse and gate lag in GaN-based high-electron-mobility transistor including self-heating effect
Authors: Hu W. D. , Chen X. S. , Quan Z. J. , Xia C. S. , Lu W. , Yuan H. J.
Published: December 2006

Using a two-dimensional simulator, the authors report on demonstration of trapping of hot electrons at gate edge model in GaN-based high-electron-mobility transistors. Dynamic picture of hot electrons under gate pulse voltage is discussed in detail. Trapped charges may accumulate under punch-off gate voltage at gate edge drain side, where the electric field significantly changes and gate-voltage-dependent strain is induced. Significant band barrier is formed at the gate edges causing a notable current collapse. Self-heating effect is one of the reasons for current collapse and gate lag.
Adhesion energy in nanogap InP∕InGaAs microcantilevers
Authors: Makowski Jan D. , Gawarikar Anand S. , Talghader Joseph J.
Published: December 2006

The adhesion energy is measured between InGaAs quantum wells that have collapsed across a 125nm air gap in an InP∕InGaAs heterostructure. The method relies on measuring the unadhered length and shape of collapsed microcantilevers with optical interferometry. The adhesion energy is found to be 72±16mJm−2. Since the air gap is much smaller than has been measured previously, the influence of van der Waals forces across the gap was included in theoretical modeling. It was found that the forces should not cause significant deviation from the standard adhesion models unless the adhesion energy drops below 25mJm−2.
Composite growth in highly undercooled Ni70.2Si29.8 eutectic alloy
Authors: Lu Yiping , Liu Feng , Yang Gencang , Zhou Yaohe
Published: December 2006

High undercooling was achieved in eutectic Ni70.2Si29.8 alloy melt using glass fluxing combined with cyclic superheating. An unusual interlaced morphology is observed in the as-solidified microstructure. This composite structure is found for the first time. Its forming process can be ascribed to a composite growth concurring with recalescence.
Thin-film transistor realized with a combined active layer
Authors: Yang Qi , Li Dejie , Yao Baolun
Published: December 2006

A combined active layer thin-film transistor is reported. The effective channel length of this planar thin-film transistor is only 1.2μm, and no high resolution lithography technology is necessary for the fabrication processes. A discontinuous metal film is deposited on the semiconductor layer to form the combined active layer. The on-state current for a 3mm channel width is about 31mA, which is sufficient for most flat panel display devices.
A Field Investigation of Solubility and Food Chain Accumulation of Biosolid-Cadmium Across Diverse Soil Types
Authors: McLaughlin Mike J. , Whatmuff Mark , Warne Michael , Heemsbergen Diane , Barry Glenn , Bell Mike , Nash David , Pritchard Deb
Published: December 2006

Environmental Context. Cadmium is a potentially toxic metal that is an unwanted contaminant in urban wastewater biosolids, and has the potential to accumulate through the food chain. This study found that the accumulation of cadmium in wheat grain from application of urban biosolids to soils in Australia was less than when cadmium was applied in a water-soluble form. The critical soil cadmium concentration, above which wheat grain would exceed food contaminant limits, could also be simply predicted using soil pH (acidity) and clay content.
Abstract. One of the pathways for transfer of cadmium (Cd) through the food chain is addition of urban wastewater solids (biosolids) to soil, and many countries have restrictions on biosolid use to minimize crop Cd contamination. The basis of these restrictions often lies in laboratory or glasshouse experimentation of soil–plant transfer of Cd, but these studies are confounded by artefacts from growing crops in controlled laboratory conditions. This study examined soil to plant (wheat grain) transfer of Cd under a wide range of field environments under typical agronomic conditions, and compared the solubility and bioavailability of Cd in biosolids to soluble Cd salts. Solubility of biosolid Cd (measured by examining Cd partitioning between soil and soil solution) was found to be equal to or greater than that of soluble Cd salts, possibly due to competing ions added with the biosolids. Conversely, bioavailability of Cd to wheat and transfer to grain was less than that of soluble Cd salts, possibly due to addition of Zn with the biosolids, causing reduced plant uptake or grain loading, or due to complexation of soluble Cd2+ by dissolved organic matter.
Multiple sequence alignment for phylogenetic purposes
Authors: Morrison David A.
Published: December 2006

I have addressed the biological rather than bioinformatics aspects of molecular sequence alignment by covering a series of topics that have been under-valued, particularly within the context of phylogenetic analysis. First, phylogenetic analysis is only one of the many objectives of sequence alignment, and the most appropriate multiple alignment may not be the same for all of these purposes. Phylogenetic alignment thus occupies a specific place within a broader context. Second, homology assessment plays an intricate role in phylogenetic analysis, with sequence alignment consisting of primary homology assessment and tree building being secondary homology assessment. The objective of phylogenetic alignment thus distinguishes it from other sorts of alignment. Third, I summarise what is known about the serious limitations of using phenetic similarity as a criterion for automated multiple alignment, and provide an overview of what is currently being done to improve these computerised procedures. This synthesises information that is apparently not widely known among phylogeneticists. Fourth, I then consider the recent development of automated procedures for combining alignment and tree building, thus integrating primary and secondary homology assessment. Finally, I outline various strategies for increasing the biological content of sequence alignment procedures, which consists of taking into account known evolutionary processes when making alignment decisions. These procedures can be objective and repeatable, and can involve computerised algorithms to automate much of the work. Perhaps the most important suggestion is that alignment should be seen as a process where new sequences are added to a pre-existing alignment that has been manually curated by the biologist.
The small-molecule VEGF receptor inhibitor pazopanib (GW786034B) targets both tumor and endothelial cells in multiple myeloma
Authors: Podar Klaus , Tonon Giovanni , Sattler Martin , Tai Yu-Tzu , LeGouill Steven , Yasui Hiroshi , Ishitsuka Kenji , Kumar Shaji , Kumar Rakesh , Pandite Lini N. , Hideshima Teru , Chauhan Dharminder , Anderson Kenneth C.
Published: December 2006

A critical role for vascular endothelial factor (VEGF) has been demonstrated in multiple myeloma (MM) pathogenesis. Here, we characterized the effect of the small-molecule VEGF receptor inhibitor pazopanib on MM cells in the bone marrow milieu. Pazopanib inhibits VEGF-triggered signaling pathways in both tumor and endothelial cells, thereby blocking
in vitro
MM cell growth, survival, and migration, and inhibits VEGF-induced up-regulation of adhesion molecules on both endothelial and tumor cells, thereby abrogating endothelial cell-MM cell binding and associated cell proliferation. We show that pazopanib is the first-in-class VEGF receptor inhibitor to inhibit
in vivo
tumor cell growth associated with increased MM cell apoptosis, decreased angiogenesis, and prolonged survival in a mouse xenograft model of human MM. Low-dose pazopanib demonstrates synergistic cytotoxicity with conventional (melphalan) and novel (bortezomib and immunomodulatory drugs) therapies. Finally, gene expression and signaling network analysis show transcriptional changes of several cancer-related genes, in particular c-Myc. Using siRNA, we confirm the role of c-Myc in VEGF production and secretion, as well as angiogenesis. These preclinical studies provide the rationale for clinical evaluation of pazopanib, alone and in combination with conventional and novel therapies, to increase efficacy, overcome drug resistance, reduce toxicity, and improve patient outcome in MM.
Purified vitamin K epoxide reductase alone is sufficient for conversion of vitamin K epoxide to vitamin K and vitamin K to vitamin KH2
Authors: Chu Pei-Hsuan , Huang Teng-Yi , Williams Jason , Stafford D. W.
Published: December 2006

More than 21 million prescriptions for warfarin are written yearly in the U.S. Despite its importance, warfarin's target, vitamin K epoxide reductase (VKOR), has resisted purification since its identification in 1972. Here, we report its purification and reconstitution. HPC4, a calcium-specific antibody that recognizes a 12-aa tag, was used to purify and identify VKOR. Partial reconstitution is achieved on the column by washing with 0.4% dioleoylphosphatidylcholine/0.4% deoxycholate. Activity is completely recovered by dialysis against a buffer containing a reducing agent but lacking dioleoylphosphatidylcholine/deoxycholate. Removal of detergent from the eluted proteins apparently facilitates liposome formation. Purified recombinant VKOR with tag is ≈21 kDa, as expected; fully active; and >93% pure. The concentration of warfarin for 50% inhibition is the same for purified protein and microsomes. It has been reported that VKOR is a multisubunit enzyme. Our results, however, suggest that a single peptide can accomplish both the conversion of vitamin K epoxide to vitamin K and vitamin K to reduced vitamin K. This purification will allow further characterization of VKOR in relation to other components of the vitamin K cycle and should facilitate its structural determination.
Paleobiology and comparative morphology of a late Neandertal sample from El Sidrón, Asturias, Spain
Authors: Rosas Antonio , Martínez-Maza Cayetana , Bastir Markus , García-Tabernero Antonio , Lalueza-Fox Carles , Huguet Rosa , Ortiz José Eugenio , Julià Ramón , Soler Vicente , de Torres Trinidad , Martínez Enrique , Cañaveras Juan Carlos , Sánchez-Moral Sergio , Cuezva Soledad , Lario Javier , Santamaría David , de la Rasilla Marco , Fortea Javier
Published: December 2006

Fossil evidence from the Iberian Peninsula is essential for understanding Neandertal evolution and history. Since 2000, a new sample ≈43,000 years old has been systematically recovered at the El Sidrón cave site (Asturias, Spain). Human remains almost exclusively compose the bone assemblage. All of the skeletal parts are preserved, and there is a moderate occurrence of Middle Paleolithic stone tools. A minimum number of eight individuals are represented, and ancient mtDNA has been extracted from dental and osteological remains. Paleobiology of the El Sidrón archaic humans fits the pattern found in other Neandertal samples: a high incidence of dental hypoplasia and interproximal grooves, yet no traumatic lesions are present. Moreover, unambiguous evidence of human-induced modifications has been found on the human remains. Morphologically, the El Sidrón humans show a large number of Neandertal lineage-derived features even though certain traits place the sample at the limits of Neandertal variation. Integrating the El Sidrón human mandibles into the larger Neandertal sample reveals a north–south geographic patterning, with southern Neandertals showing broader faces with increased lower facial heights. The large El Sidrón sample therefore augments the European evolutionary lineage fossil record and supports ecogeographical variability across Neandertal populations.
Experience pays: offspring survival increases with female age
Authors: Paitz Ryan T , Harms Heidi K , Bowden Rachel M , Janzen Fredric J
Published: December 2006

Life-history theory predicts that, in long-lived organisms, effort towards reproduction will increase with age, and research from oviparous vertebrates largely supports this prediction. In reptiles, where parental care occurs primarily via provisioning of the egg, older females tend to produce larger eggs, which in turn produce larger hatchlings that have increased survival. We conducted an experimental release study and report that maternal age positively influences offspring survivorship in the painted turtle (Chrysemys picta) and predicts offspring survival at least as well as hatchling body size does. These data suggest that, although increasing hatchling size is a major component of reproductive success in older individuals, other factors also contribute.
Mathematical models of the VEGF receptor and its role in cancer therapy
Authors: Alarcón Tomás , Page Karen M
Published: December 2006

We present an analysis of a stochastic model of the vascular endothelial growth factor (VEGF) receptor. This analysis addresses the contribution of ligand-binding-induced oligomerization, activation of src-homology 2 domain-carrying kinases and receptor internalization in the overall behaviour of the VEGF/VEGF receptor (VEGFR) system. The analysis is based upon a generalization of a Wentzel–Kramers–Brillouin (WKB) approximation of the solution of the corresponding master equation. We predict that tumour-mediated overexpression of VEGFRs in the endothelial cells (ECs) of tumour-engulfed vessels leads to an increased sensitivity of the ECs to low concentrations of VEGF, thus endowing the tumour with increased resistance to anti-angiogenic treatment.
Tissue engineering of replacement skin: the crossroads of biomaterials, wound healing, embryonic development, stem cells and regeneration
Authors: Metcalfe Anthony D , Ferguson Mark W.J
Published: December 2006

Advanced therapies combating acute and chronic skin wounds are likely to be brought about using our knowledge of regenerative medicine coupled with appropriately tissue-engineered skin substitutes. At the present time, there are no models of an artificial skin that completely replicate normal uninjured skin. Natural biopolymers such as collagen and fibronectin have been investigated as potential sources of biomaterial to which cells can attach. The first generation of degradable polymers used in tissue engineering were adapted from other surgical uses and have drawbacks in terms of mechanical and degradation properties. This has led to the development of synthetic degradable gels primarily as a way to deliver cells and/or moleculesin situ, the so-called smart matrix technology. Tissue or organ repair is usually accompanied by fibrotic reactions that result in the production of a scar. Certain mammalian tissues, however, have a capacity for complete regeneration without scarring; good examples include embryonic or foetal skin and the ear of the MRL/MpJ mouse. Investigations of these model systems reveal that in order to achieve such complete regeneration, the inflammatory response is altered such that the extent of fibrosis and scarring is diminished. From studies on the limited examples of mammalian regeneration, it may also be possible to exploit such models to further clarify the regenerative process. The challenge is to identify the factors and cytokines expressed during regeneration and incorporate them to create a smart matrix for use in a skin equivalent. Recent advances in the use of DNA microarray and proteomic technology are likely to aid the identification of such molecules. This, coupled with recent advances in non-viral gene delivery and stem cell technologies, may also contribute to novel approaches that would generate a skin replacement whose materials technology was based not only upon intelligent design, but also upon the molecules involved in the process of regeneration.
The mechanics of active fin-shape control in ray-finned fishes
Authors: Alben Silas , Madden Peter G , Lauder George V
Published: December 2006

We study the mechanical properties of fin rays, which are a fundamental component of fish fin structure. We derive a linear elasticity model that predicts the shape of fin rays, given the input muscle actuation and external loading. We then test the model using experiments that measure (i) the ray deflection for a given actuation at the muscular interface, and (ii) the force–displacement response under conditions of actuation and non-actuation. The model agrees well with the experiment; both show a concentration of curvature at the ray base or at the point of an externally applied force, and a variation in ray stiffness over more than an order of magnitude depending on actuation at the bases of the fin rays.