bluuebunny/crossref_metadata_2025 huggingface dataset:
Carbon nanotube-based nonvolatile memory with charge storage in metal nanocrystals
Authors: Ganguly Udayan , Kan Edwin C. , Zhang Yuegang
Published: July 2005

Ultrathin and narrow semiconductor body on insulator allows aggressive scaling of nonvolatile memories for low power, low read/write voltage, high retention, and high density in comparison with bulk devices. We have fabricated memory cells with single-wall carbon nanotubes as channels and gold nanocrystals as charge storage nodes. The devices have large memory windows with low voltage operations and single-electron-controlled drain currents. Coulomb blockade in nanocrystals combined with single charge sensitivity of the nanotube field-effect transistor can potentially enable multilevel operations. Measured retention time is longer than 6200 s at 10 K, but is only about 800 s at room temperature due to the high leakage in evaporated tunnel oxide used in this study. Better dielectric on nanotubes is expected to greatly improve the room-temperature performance for the nanotube memory device.
Alternate operating mode for long wavelength blocked impurity band detectors
Authors: Garcia J. C. , Haegel N. M. , Zagorski E. A.
Published: July 2005

Numerical modeling demonstrates an alternate bias mode for blocked impurity band (BIB) detectors that can reduce growth constraints on the high purity blocking layer. Initiating depletion from the contact on the active layer (the opposite of conventional operation) significantly reduces the large electric field and resultant voltage drop in the blocking layer. Electric field profiles are presented to show that the alternate bias allows for growth of significantly thicker blocking layers. This could be applied to produce modified BIB devices in far-infrared materials (λ>40μm) where growth issues associated with the blocking layer have prohibited conventional operation.
Quantitative determination of the clustered silicon concentration in substoichiometric silicon oxide layer
Authors: Spinella Corrado , Bongiorno Corrado , Nicotra Giuseppe , Rimini Emanuele , Muscarà Anna , Coffa Salvo
Published: July 2005

We present an analytical methodology, based on electron energy loss spectroscopy (EELS) and energy-filtered transmission electron microscopy, which allows us to quantify the clustered silicon concentration in annealed substoichiometric silicon oxide layers, deposited by plasma-enhanced chemical vapor deposition. The clustered Si volume fraction was deduced from a fit to the experimental EELS spectrum using a theoretical description proposed to calculate the dielectric function of a system of spherical particles of equal radii, located at random in a host material. The methodology allowed us to demonstrate that the clustered Si concentration is only one half of the excess Si concentration dissolved in the layer.
Thermoelectric properties of lanthanum sesquisulfide with Ti additive
Authors: Ohta Michihiro , Hirai Shinji , Kato Hisanaga , Nishimura Toshiyuki , Uemura Yoichiro
Published: July 2005

The electrical resistivity, thermopower, and thermal conductivity have been measured for the lanthanum sesquisulfide (La2S3) of which the crystal phase is controlled by the Ti additive. In all the samples, the thermopower is negative between 300 and 1000 K. The sample with 8 wt % Ti, which consists almost of the cubic γ phase, behaves as a degenerate semiconductor. The thermoelectric figure of merit ZT increases with increasing temperature, reaching a value of 0.21 at 1000 K. In contrast, the sample with 2 wt % Ti consists almost of the tetragonal β phase. The transport mechanism can be well explained by the model of the Anderson localization. The ZT value increases abruptly with increasing temperature. At 1000 K, this ZT value is comparable with that of the sample with 8 wt % Ti.
Fabrication of (Ga,Mn)N nanowires with room temperature ferromagnetism using nitrogen plasma
Authors: Baik Jeong Min , Shon Yoon , Kang Tae Won , Lee Jong-Lam
Published: July 2005

Ferromagnetic properties of (Ga,Mn)N nanowires were examined by treating with nitrogen plasma at 200 °C. Nanowires grown by chemical vapor deposition were n-type and no secondary phases were found. The magnetic moment increased and was maintained at room temperature by this treatment. Synchrotron radiation photoemission spectroscopy revealed that Ga vacancies significantly increased, but N vacancies decreased by plasma treatment, leading to a decrease of MnGa–VN complex and the enhancement of Mn activation.
Performances and limitations of InAs∕InAlAs metamorphic heterostructures on InP for high mobility devices
Authors: Wallart X. , Lastennet J. , Vignaud D. , Mollot F.
Published: July 2005

InAs has been studied as the active material of metamorphic InAlAs∕InAs modulation-doped heterostructures grown on InP. We show that the main limitation of these structures is the plastic relaxation of the 10–15nm thick InAs channel compressively strained to the underlying InAlAs buffer. The best results are obtained with a composite channel made of 7nm InAs inserted in an InGaAs layer. In this case, the electron mobility reaches 21 500 and 179000cm2∕Vs at 300 and 77K, respectively, for a sheet carrier density of 9×1011cm−2. These values are among the highest ones ever reported for such metamorphic structures.
Hydrogen-assisted stabilization of Ni nanowires in solution
Authors: Kiguchi Manabu , Konishi Tatsuya , Murakoshi Kei
Published: July 2005

We have studied conductance characteristics of mechanically fabricated Ni nanoconstrictions under controlling electrochemical potential and pH of the electrolyte. The conductance histogram showed a clear feature peaked at 1–1.5 G0(G0=2e2∕h) when the potential of the constriction was kept at more negative potential than −900mV versus Ag∕AgCl at pH=3.7. A comparable feature also appeared at a more positive potential when a lower pH solution was used. We have revealed that Ni monoatomic contact or monoatomic wire can be stabilized in solution at room temperature under the hydrogen evolution.
Theoretical investigation of surface roughness scattering in silicon nanowire transistors
Authors: Wang Jing , Polizzi Eric , Ghosh Avik , Datta Supriyo , Lundstrom Mark
Published: July 2005

Using a full three-dimensional (3D), quantum transport simulator, we theoretically investigate the effects of surface roughness scattering (SRS) on the device characteristics of Si nanowire transistors (SNWTs). The microscopic structure of the Si/SiO2 interface roughness is directly treated by using a 3D finite element technique. The results show that (1) SRS reduces the electron density of states in the channel, which increases the SNWT threshold voltage, and (2) the SRS in SNWTs becomes less effective when fewer propagating modes are occupied, which implies that SRS is less important in small-diameter SNWTs with few modes conducting than in planar metal-oxide-semiconductor field-effect-transistors with many transverse modes occupied.
Exciton radiative recombination in spherical CdS∕CdSe∕CdS quantum-well nanostructures
Authors: Xu Jianfeng , Xiao Min , Battaglia David , Peng Xiaogang
Published: July 2005

Photoluminescence (PL) and lifetimes of colloidal CdS∕CdSe∕CdS (core∕well∕shell) quantum-well (QW) nanostructures are investigated for different well thicknesses in the temperature range of 77–300K. When the temperature increases, the PL intensity decreases continuously and PL peak shifts to lower energy side. The PL lifetimes for the 1–3 monolayer (ML) CdSe QWs increase with temperature and radiative recombination dominates the decay processes. The radiative lifetimes basically increase linearly with temperature, which indicates the existence of free two-dimensional excitons. For the 4 ML CdSe QW sample, the lifetime does not increase with temperature, showing more nonradiative processes due to more defect formation within the thicker QWs.
Increases in the irreversibility field and the upper critical field of bulk MgB2 by ZrB2 addition
Authors: Bhatia M. , Sumption M. D. , Collings E. W. , Dregia S.
Published: July 2005

In a study of the influence of ZrB2 additions on the irreversibility field, μ0Hirr and the upper critical field Bc2, bulk samples with 7.5at% ZrB2 additions were made by a powder milling and compaction technique. These samples were then heated to 700–900°C for 0.5h. Resistive transitions were measured at 4.2K and μ0Hirr and Bc2 values were determined. An increase in Bc2 from 20.5Tto28.6T and enhancement of μ0Hirr from 16Tto24T were observed in the ZrB2 doped sample as compared to the binary sample at 4.2K. Critical field increases similar to those found with SiC doping were seen at 4.2K. At higher temperatures, increases in μ0Hirr were also determined by M-H loop extrapolation and closure. Values of μ0Hirr which were enhanced with ZrB2 doping (as compared to the binary) were seen at temperatures up to 34K, with μ0Hirr values larger than those for SiC doped samples at higher temperatures. The transition temperature, Tc, was then measured using dc susceptibility and a 2.5K drop of the midpoint of Tc was observed. The critical current density was determined using magnetic measurements and was found to increase at all temperatures between 4.2K and 35K with ZrB2 doping.
Wave-form sampling using a driven electron ratchet in a two-dimensional electron system
Authors: Müller T. , Würtz A. , Lorke A. , Reuter D. , Wieck A. D.
Published: July 2005

We utilize a time-periodic ratchetlike potential modulation imposed onto a two-dimensional electron system inside a GaAs∕AlxGa1−xAs heterostructure to evoke a net pumped direct current. The modulation is induced by two sets of interdigitated gates, interlacing off center, which can be independently addressed. When the transducers are driven by two identical but phase-shifted periodic signals, a lateral pumped direct current I(φ) results, which strongly depends on both, the phase shift φ and the wave form V(t) of the imposed gate voltages. We find that for different periodic signals, the phase dependence I(φ) closely resembles V(t). A simple linear model of pumping in two-dimensional electron systems is presented, which reproduces well our experimental findings.
Real-space electron transfer in III-nitride metal-oxide-semiconductor-heterojunction structures
Authors: Saygi S. , Koudymov A. , Adivarahan V. , Yang J. , Simin G. , Khan M. Asif , Deng J. , Gaska R. , Shur M. S.
Published: July 2005

The real-space transfer effect in a SiO2∕AlGaN∕GaN metal-oxide-semiconductor heterostructure (MOSH) from the two-dimensional (2D) electron gas at the heterointerface to the oxide-semiconductor interface has been demonstrated and explained. The effect occurs at high positive gate bias and manifests itself as an additional step in the capacitance-voltage (C-V) characteristic. The real-space transfer effect limits the achievable maximum 2D electron gas density in the device channel. We show that in MOSH structures the maximum electron gas density exceeds up to two times that at the equilibrium (zero bias) condition. Correspondingly, a significant increase in the maximum channel current (up to two times compared to conventional Schottky-gate structures) can be achieved. The real-space charge transfer effect in MOSH structures also opens up a way to design novel devices such as variable capacitors, multistate switches, memory cells, etc.
Quantum efficiency of ZnO nanowire nanolasers
Authors: Zhang Yanfeng , Russo Richard E. , Mao Samuel S.
Published: July 2005

Crystalline ZnO nanowires were grown on sapphire and silicon substrates using pulsed-laser deposition. The optical properties of nanowire nanolasers, including their absolute light emission intensity and external and internal quantum efficiencies were experimentally determined. The external differential quantum efficiency was measured to be as high as 60% for lasing ZnO nanowires of 7.5μm in length, compared to a value of approximately 10% for photoluminescence. The absolute light emission intensity for individual nanowires was found to be in the vicinity of 0.1mW. By measuring the dependence of external differential quantum efficiency on the cavity length, the internal quantum efficiency of ZnO nanowire nanolasers was determined to be about 85%.
Infrared (3.8μm) interband cascade light-emitting diode array with record high efficiency
Authors: Das Naresh C. , Olver Kim , Towner F. , Simonis G. , Shen H.
Published: July 2005

We report here the light emission from IR interband-cascade (IC) type-II-superlattice light-emitting diode (LED) structures. We employed two different IC epitaxial structures consisting of 9 or 18 periods of active superlattice gain regions separated by multilayer injection regions. The light output (and the voltage drop) of the LEDs is observed to increase as expected with increase in the number of IC active regions. The 18-period LEDs are found to have 0.65% and 2.8% external efficiency at room temperature and liquid nitrogen temperature respectively. An increase of light intensity by 6 times is observed by thinning the GaSb substrates from 500μmto25μm. Another 10% increase is observed using a linear grating on the top surface of the device.
Cr
∕
Pt
Ohmic contacts to B12As2
Authors: Wang S. H. , Lysczek E. M. , Liu Bangzhi , Mohney S. E. , Xu Z. , Nagarajan R. , Edgar J. H.
Published: July 2005

Palladium, Pt, and Cr∕Pt contacts to the wide band gap icosahedral boride semiconductor B12As2 have been studied. All Pd and Pt contacts exhibited nonlinear I-V characteristics, while Cr∕Pt contacts were Ohmic. The specific contact resistance was reduced from 6Ωcm2 as-deposited to 3×10−4Ωcm2 after the Cr∕Pt contacts were annealed at 750°C for 30s in Ar. Annealing at 600°C or higher drastically reduced the semiconductor sheet resistance, whether annealing was performed before or after metallization. This apparent activation of the semiconductor is a likely cause for the improvement in the Ohmic contacts with annealing.
Photomixers fabricated on nitrogen-ion-implanted GaAs
Authors: Mikulics M. , Marso M. , Mayorga I. Cámara , Güsten R. , Stanček S. , Kováč P. , Wu S. , Li Xia , Khafizov M. , Sobolewski R. , Michael E. A. , Schieder R. , Wolter M. , Buca D. , Förster A. , Kordoš P. , Lüth H.
Published: July 2005

We report on fabrication and measurement of photomixers based on nitrogen-ion-implanted GaAs. We used energies of 500keV, 700keV, and 880keV to implant N+ ions into GaAs substrates with an ion concentration of ∼3×1012cm−2. The resulting material exhibited 110fs carrier lifetime due to implantation-induced defects. Our photomixers were fabricated as metal-semiconductor-metal devices, placed at the feed point of a broadband antenna. Optoelectronic measurements were performed in the wavelength range between 350nm and 950nm. In comparison to their counterparts (photomixers fabricated on low-temperature-grown GaAs) the N+-implanted GaAs photomixers exhibit improvements on both the output power and responsivity. A maximal responsivity of above 100mA∕W was achieved and we did not observe any dependence of the mixer cut-off frequency on the bias voltage. These characteristics make N+-implanted GaAs the material of choice for efficient optoelectronic photomixers.
A stop codon polymorphism of Toll-like receptor 5 is associated with resistance to systemic lupus erythematosus
Authors: Hawn Thomas R. , Wu Hui , Grossman Jennifer M. , Hahn Bevra H. , Tsao Betty P. , Aderem Alan
Published: July 2005

Systemic lupus erythematosus (SLE) is an autoimmune disease with a complex genetic basis that includes susceptibility gene(s) within the chromosome 1q41–1q42 region. Toll-like receptor 5 (TLR5), the innate immune receptor for bacterial flagellin, maps to chromosome 1q41 and contains a common stop codon polymorphism that abrogates signaling (allele C1174T) and is associated with an increased risk of infection. By using transmission disequilibrium testing in a cohort containing 199 affected patients and their 75 unaffected siblings and 326 parents, we found that allele 1174C, but not 1174T (with the stop codon), was preferentially transmitted to SLE-affected offspring (a 19:6 transmitted/not transmitted ratio,
P
= 0.009). In contrast, the alleles of the other three TLR5 SNPs did not exhibit preferential transmission. In addition, we found that allele 1174C was not preferentially transmitted to unaffected offspring (3:6 transmitted/not transmitted ratio,
P
value not significant). The allele frequency of 1174T in the probands was 3.2% compared with 5.8% in unaffected individuals, which was consistent with a protective association (odds ratio, 0.51; 95% confidence interval, 0.26–0.98;
P
= 0.041). Subjects with the TLR5 stop codon produced significantly lower levels of proinflammatory cytokines in comparison with individuals with the wild-type genotype. Together, these results indicate that the TLR5 stop codon polymorphism is associated with protection from the development of SLE. These data support a role for flagellated bacteria and the innate immune response in the development of SLE with implications for novel immunomodulatory treatment strategies.
Variant tricarboxylic acid cycle in
Mycobacterium tuberculosis
: Identification of α-ketoglutarate decarboxylase
Authors: Tian Jing , Bryk Ruslana , Itoh Manabu , Suematsu Makoto , Nathan Carl
Published: July 2005

Mycobacterium tuberculosis
(Mtb) has adapted its metabolism for persistence in the human macrophage. The adaptations are likely to involve Mtb's core intermediary metabolism, whose enzymes have been little studied. The tricarboxylic acid cycle is expected to yield precursors for energy, lipids, amino acids, and heme. The genome sequence of Mtb H37Rv predicts the presence of a complete tricarboxylic acid cycle, but we recently found that α-ketoglutarate dehydrogenase (KDH) activity is lacking in Mtb lysates. Here we showed that citrate synthase, aconitase, isocitrate dehydrogenase, fumarase, malate dehydrogenase, and succinate dehydrogenase, but not KDH, are present, raising the possibility of separate oxidative and reductive half-cycles. As a potential link between the half-cycles, we found that Rv1248c, annotated as encoding SucA, the putative E1 component of KDH, instead encodes α-ketoglutarate decarboxylase (Kgd) and produces succinic semialdehyde. Succinic semialdehyde dehydrogenase activity was detected in Mtb lysates and recapitulated with recombinant proteins GabD1 (encoded by Rv0234c) and GabD2 (encoded by Rv1731). Kgd and GabD1 or GabD2 form an alternative pathway from α-ketoglutarate to succinate. Rv1248c, which is essential or required for normal growth of Mtb [Sassetti, C., Boyd, D. H. & Rubin, E. J. (2003)
Mol. Microbiol
48, 77-84] is the first gene shown to encode a Kgd. Kgd is lacking in humans and may represent a potential target for chemotherapy of tuberculosis.
Expansion of calcium microdomains regulates fast exocytosis at a ribbon synapse
Authors: Beaumont Vahri , Llobet Artur , Lagnado Leon
Published: July 2005

We investigated the Ca
2+
signal regulating fast exocytosis at the ribbon synapse of retinal bipolar cells by using total internal reflection fluorescence microscopy to image fluorescent Ca
2+
indicators and interference reflection microscopy to monitor exocytosis. Depolarization generated Ca
2+
“microdomains” that expanded over the time scale during which the rapidly releasable pool (RRP) of vesicles was released (<40 ms). Replacing mobile Ca
2+
buffers in the terminal with 10 mM EGTA prevented expansion of microdomains and decreased the number of rapidly releasable vesicles by a factor of 2. Conversely, decreasing the concentration of EGTA in the terminal to 0.1 mM increased the apparent width of a Ca
2+
microdomain from 580 nm to 930 nm and increased the size of the RRP size by a factor of 1.5. The [Ca
2+
] over the area that the microdomain expanded was estimated to be 2-7 μM. These results indicate that vesicles within the RRP are located hundreds of nanometers from Ca
2+
channels, and that fusion of these vesicles can be triggered by low micromolar levels of Ca
2+
. Variable distances between docked vesicles and Ca
2+
channels at the active zone, therefore, provide an explanation for the heterogeneous release probability of vesicles comprising the RRP.
Structure of Mycobacterium tuberculosis glutamine synthetase in complex with a transition-state mimic provides functional insights
Authors: Krajewski Wojciech W. , Jones T. Alwyn , Mowbray Sherry L.
Published: July 2005

Glutamine synthetase catalyzes the ligation of glutamate and ammonia to form glutamine, with the resulting hydrolysis of ATP. The enzyme is a central component of bacterial nitrogen metabolism and is a potential drug target. Here, we report a high-yield recombinant expression system for glutamine synthetase of
Mycobacterium tuberculosis
together with a simple purification. The procedure allowed the structure of a complex with a phosphorylated form of the inhibitor methionine sulfoximine, magnesium, and ADP to be solved by molecular replacement and refined at 2.1-Å resolution. To our knowledge, this study provides the first reported structure for a taut form of the
M. tuberculosis
enzyme, similar to that observed for the
Salmonella
enzyme earlier. The phospho compound, generated
in situ
by an active enzyme, mimics the phosphorylated tetrahedral adduct at the transition state. Some differences in ligand interactions of the protein with both phosphorylated compound and nucleotide are observed compared with earlier structures; a third metal ion also is found. The importance of these differences in the catalytic mechanism is discussed; the results will help guide the search for specific inhibitors of potential therapeutic interest.
Ethylene-mediated cross-talk between calcium-dependent protein kinase and MAPK signaling controls stress responses in plants
Authors: Ludwig Andrea A. , Saitoh Hiromasa , Felix Georg , Freymark Gerald , Miersch Otto , Wasternack Claus , Boller Thomas , Jones Jonathan D. G. , Romeis Tina
Published: July 2005

Plants are constantly exposed to environmental changes and need to integrate multiple external stress cues. Calcium-dependent protein kinases (CDPKs) are implicated as major primary Ca
2+
sensors in plants. CDPK activation, like activation of mitogen-activated protein kinases (MAPKs), is triggered by biotic and abiotic stresses, although distinct stimulus-specific stress responses are induced. To investigate whether CDPKs are part of an underlying mechanism to guarantee response specificity, we identified CDPK-controlled signaling pathways. A truncated form of
Nicotiana tabacum
CDPK2 lacking its regulatory autoinhibitor and calcium-binding domains was ectopically expressed in
Nicotiana benthamiana
. Infiltrated leaves responded to an abiotic stress stimulus with the activation of biotic stress reactions. These responses included synthesis of reactive oxygen species, defense gene induction, and SGT1-dependent cell death. Furthermore, N-terminal CDPK2 signaling triggered enhanced levels of the phytohormones jasmonic acid, 12-oxo-phytodienoic acid, and ethylene but not salicylic acid. These responses, commonly only observed after challenge with a strong biotic stimulus, were prevented when the CDPK's intrinsic autoinhibitory peptide was coexpressed. Remarkably, elevated CDPK signaling compromised stress-induced MAPK activation, and this inhibition required ethylene synthesis and perception. These data indicate that CDPK and MAPK pathways do not function independently and that a concerted activation of both pathways controls response specificity to biotic and abiotic stress.
Barnacle reproductive hotspots linked to nearshore ocean conditions
Authors: Leslie Heather M. , Breck Erin N. , Chan Francis , Lubchenco Jane , Menge Bruce A.
Published: July 2005

Coastal marine ecosystems provide important ecosystem services to human populations worldwide. Understanding the contexts in which a species has markedly higher reproductive output is vital for effective management and conservation of these valuable and highly impacted systems. We documented reproductive hotspots along the Oregon coast for an ecologically significant marine invertebrate, the intertidal barnacleBalanus glandula. Greater larval production in both natural and experimental populations was associated with higher primary productivity in the adjacent nearshore ocean, providing strong evidence for bottom-up forcing. Mean cumulative larval production per 100 cm2in natural barnacle populations in the region of higher primary productivity was almost 5× that of populations in the less productive region. Mean estimated larval production per individual in experimental populations in the region of higher primary productivity was >2× that of populations in the region of lower productivity, and mean larval production per 100 cm2was >120× greater in the region of higher productivity. Our results highlight the importance of spatial heterogeneity in reproduction and other ecological processes in the marine environment and provide a mechanistic basis for evaluating the relative contributions of different sites when designing marine reserves and other protected areas. Our findings also advance the understanding of the role of bottom-up influences on population and community dynamics and contribute data for the next generation of models of marine community dynamics.
Computational model of the cAMP-mediated sensory response and calcium-dependent adaptation in vertebrate olfactory receptor neurons
Authors: Dougherty Daniel P. , Wright Geraldine A. , Yew Alice C.
Published: July 2005

We develop a mechanistic mathematical model of the G-protein coupled signaling pathway responsible for generating current responses in frog olfactory receptor neurons. The model incorporates descriptions of ligand-receptor interaction, intracellular transduction events involving the second messenger cAMP, effector ion-channel activity, and calcium-mediated feedback steps. We parameterized the model with respect to suction pipette current recordings from single cells stimulated with multiple odor concentrations. The proposed model accurately predicts the receptor-current response of the neuron to brief and prolonged odorant exposure and is able to produce the adaptation observed under repeated or sustained stimulation.
Effective treatment of experimental human non-Hodgkin's lymphomas with antagonists of growth hormone-releasing hormone
Authors: Keller Gunhild , Schally Andrew V. , Groot Kate , Toller Gabor L. , Havt Alexandre , Köster Frank , Armatis Patricia , Halmos Gabor , Zarandi Marta , Varga Jozsef L. , Engel Jörg B.
Published: July 2005

Antagonists of growth hormone-releasing hormone (GHRH) were shown to inhibit the growth of various cancers. We investigated the antitumor activity and the mechanism of action of GHRH antagonists in human non-Hodgkin's lymphomas (NHL). Nude mice bearing xenografts of RL and HT human NHL were treated with GHRH antagonists MZ-5-156 and MZ-J-7-138 at a dose of 40 μg twice daily. The concentrations of serum IGF-1 and GHRH, bFGF, and VEGF in tumor tissue were measured by radioimmunoassays. Expression of GHRH and splice variant 1 of the GHRH receptor in both cell lines was examined by RT-PCR. The effects of MZ-5-156, MZ-J-7-138 and GHRH on cell proliferation were evaluated
in vitro
. Treatment with MZ-5-156 and MZ-J-7-138 significantly (
P
< 0.05) inhibited the growth of RL and HT tumors by 59.9-73.9%. High-affinity binding sites for GHRH and mRNA for GHRH and splice variant-1 of the GHRH receptors were found on RL and HT tumors. RL and HT cells contained GHRH peptide, and their growth
in vitro
was significantly inhibited by both antagonists. IGF-I levels in serum of mice were significantly decreased by antagonist MZ-5-156. Therapy with GHRH antagonists also significantly reduced tumoral bFGF, whereas VEGF levels were not suppressed. Our findings suggest that GHRH antagonists inhibit the growth of RL and HT lymphomas by direct effects mediated by tumoral receptors for GHRH. GHRH antagonists could offer a new therapeutic modality for the management of advanced NHL.
Effect of bicarbonate on iron-mediated oxidation of low-density lipoprotein
Authors: Arai Hirofumi , Berlett Barbara S. , Chock P. Boon , Stadtman Earl R.
Published: July 2005

Oxidation of low-density lipoprotein (LDL) may play an important role in atherosclerosis. We studied the effects of bicarbonate/CO
2
and phosphate buffer systems on metal ion-catalyzed oxidation of LDL to malondialdehyde (MDA) and to protein carbonyl and MetO derivatives. Our results revealed that LDL oxidation in mixtures containing free iron or heme derivatives was much greater in bicarbonate/CO
2
compared with phosphate buffer. However, when copper was substituted for iron in these mixtures, the rate of LDL oxidation in both buffers was similar. Iron-catalyzed oxidation of LDL was highly sensitive to inhibition by phosphate. Presence of 0.3-0.5 mM phosphate, characteristic of human serum, led to 30-40% inhibition of LDL oxidation in bicarbonate/CO
2
buffer. Iron-catalyzed oxidation of LDL to MDA in phosphate buffer was inhibited by increasing concentrations of albumin (10-200 μM), whereas MDA formation in bicarbonate/CO
2
buffer was stimulated by 10-50 μM albumin but inhibited by higher concentrations. However, albumin stimulated the oxidation of LDL proteins to carbonyl derivatives at all concentrations examined in both buffers. Conversion of LDL to MDA in bicarbonate/CO
2
buffer was greatly stimulated by ADP, ATP, and EDTA but only when EDTA was added at a concentration equal to that of iron. At higher than stoichiometric concentrations, EDTA prevented oxidation of LDL. Results of these studies suggest that interactions between bicarbonate and iron or heme derivatives leads to complexes with redox potentials that favor the generation of reactive oxygen species and/or to the generation of highly reactive CO
2
anion or bicarbonate radical that facilitates LDL oxidation.
Accelerated chemokine receptor 7-mediated dendritic cell migration in Runx3 knockout mice and the spontaneous development of asthma-like disease
Authors: Fainaru Ofer , Shseyov David , Hantisteanu Shay , Groner Yoram
Published: July 2005

The Runx3 transcription factor is a key regulator of lineage-specific gene expression in several developmental pathways and could also be involved in autoimmunity. We report that, in dendritic cells (DC), Runx3 regulates TGFβ-mediated transcriptional attenuation of the chemokine receptor CCR7. When Runx3 is lost, i.e., in Runx3 knockout mice, expression of CCR7 is enhanced, resulting in increased migration of alveolar DC to the lung-draining lymph nodes. This increased DC migration and the consequent accumulation of activated DC in draining lymph nodes is associated with the development of asthma-like features, including increased serum IgE, hypersensitivity to inhaled bacterial lipopolysaccharide, and methacholine-induced airway hyperresponsiveness. The enhanced migration of DC in the knockout mice could be blockedin vivoby anti-CCR7 antibodies and by the drug Ciglitazone, known to inhibit CCR7 expression. The data indicate that Runx3 transcriptionally regulates CCR7 and that, when absent, the dysregulated expression of CCR7 in DC plays a role in the etiology of asthmatic conditions that recapitulate clinical symptoms of the human disease. Interestingly, humanRUNX3resides in a region of chromosome 1p36 that contains susceptibility genes for asthma and hypersensitivity against environmental antigens. Thus, mutations inRUNX3may be associated with increased sensitivity to asthma development.
Genome-wide screen identifies host genes affecting viral RNA recombination
Authors: Serviene Elena , Shapka Natalia , Cheng Chi-Ping , Panavas Tadas , Phuangrat Bencharong , Baker Jannine , Nagy Peter D.
Published: July 2005

Rapid evolution of RNA viruses with mRNA-sense genomes is a major concern to health and economic welfare because of the devastating diseases these viruses inflict on humans, animals, and plants. To test whether host genes can affect the evolution of RNA viruses, we used a
Saccharomyces cerevisiae
single-gene deletion library, which includes ≈80% of yeast genes, in RNA recombination studies based on a small viral replicon RNA derived from tomato bushy stunt virus. The genome-wide screen led to the identification of five host genes whose absence resulted in the rapid generation of new viral RNA recombinants. Thus, these genes normally suppress viral RNA recombination, but in their absence, hosts become viral recombination “hotbeds.” Four of the five suppressor genes are likely involved in RNA degradation, suggesting that RNA degradation could play a role in viral RNA recombination. In contrast, deletion of four other host genes inhibited virus recombination, indicating that these genes normally accelerate the RNA recombination process. A comparison of deletion strains with the lowest and the highest recombination rate revealed that host genes could affect recombinant accumulation by up to 80-fold. Overall, our results demonstrate that a set of host genes have a major effect on RNA virus recombination and evolution.
Myosin 2 Is a Key Rho Kinase Target Necessary for the Local Concentration of E-Cadherin at Cell–Cell Contacts
Authors: Shewan Annette M. , Maddugoda Madhavi , Kraemer Astrid , Stehbens Samantha J. , Verma Suzie , Kovacs Eva M. , Yap Alpha S.
Published: July 2005

Classical cadherins accumulate at cell–cell contacts as a characteristic response to productive adhesive ligation. Such local accumulation of cadherins is a developmentally regulated process that supports cell adhesiveness and cell–cell cohesion. Yet the molecular effectors responsible for cadherin accumulation remain incompletely understood. We now report that Myosin 2 is critical for cells to concentrate E-cadherin at cell–cell contacts. Myosin 2 is found at cadherin-based cell–cell contacts and its recruitment requires E-cadherin activity. Indeed, both Myosin 2 recruitment and its activation were stimulated by E-cadherin homophilic ligation alone. Inhibition of Myosin 2 activity by blebbistatin or ML-7 rapidly impaired the ability of cells to concentrate E-cadherin at adhesive contacts, accompanied by decreased cadherin-based cell adhesiveness. The total surface expression of cadherins was unaffected, suggesting that Myosin 2 principally regulates the regional distribution of cadherins at the cell surface. The recruitment of Myosin 2 to cadherin contacts, and its activation, required Rho kinase; furthermore, inhibition of Rho kinase signaling effectively phenocopied the effects of Myosin 2 inhibition. We propose that Myosin 2 is a key effector of Rho-Rho kinase signaling that regulates cell–cell adhesion by determining the ability of cells to concentrate cadherins at contacts in response to homophilic ligation.
Transcription in response to physical stress—clues to the molecular mechanisms of exercise‐induced asthma
Authors: Hilberg Thomas , Deigner Hans‐Peter , Möller Eva , Claus Ralf A. , Ruryk Andriy , Gläser Doreen , Landre Julien B. P. , Brunkhorst Frank M. , Reinhart Konrad , Gabriel Holger H. W. , Russwurm Stefan
Published: July 2005

To clarify stress‐induced immunological reactions and molecular events during exercise and the potential relevance to exercise‐induced bronchoconstriction, transcriptional responses to standardized physical stress were determined. Six healthy, young volunteers underwent an endurance exercise of 90% of their individual anaerobic threshold for 90 min. Time‐dependent alterations in the expression pattern of leukocytes from healthy, trained subjects were analyzed by DNA microarrays before and 2 h and 6 h after exercise. Starting out from a large collection of cDNA library clones comprising more than 70,000 human expressed sequence tags, we selected, designed, and immobilized oligonucleotide probes (60–70mers) for transcripts of 5000 stress‐and inflammation‐relevant genes. Exercise‐induced stress provoked changes in the expression of 433 gene activities 2 h and/or 6 h after exercise, which could be grouped into six clusters. The most prominent feature was an enhanced transcription of two genes, coding for 5‐lipoxygenase (ALOX5) and ALOX5‐activating protein. Moreover, enhanced levels of leukotriene B4 (LTB4) and LTC4 (P<0.05) were detected in plasma after exercise. Our data demonstrate that exercise alters the activities of a distinct number of genes. In particular, they possibly provide novel insights into the molecular mechanisms of exercise‐induced bronchoconstriction and suggest that enhanced transcription of ALOX5 and its activating protein together with a present predisposition of the subject critically contribute to exercise‐induced asthma.
Invasive exotic plants suffer less herbivory than non-invasive exotic plants
Authors: Cappuccino Naomi , Carpenter David
Published: July 2005

We surveyed naturally occurring leaf herbivory in nine invasive and nine non-invasive exotic plant species sampled in natural areas in Ontario, New York and Massachusetts, and found that invasive plants experienced, on average, 96% less leaf damage than non-invasive species. Invasive plants were also more taxonomically isolated than non-invasive plants, belonging to families with 75% fewer native North American genera. However, the relationship between taxonomic isolation at the family level and herbivory was weak. We suggest that invasive plants may possess novel phytochemicals with anti-herbivore properties in addition to allelopathic and anti-microbial characteristics. Herbivory could be employed as an easily measured predictor of the likelihood that recently introduced exotic plants may become invasive.
Inelastic neutron scattering study on bioprotectant systems
Authors: Magazù S , Migliardo F , Ramirez-Cuesta A.J
Published: July 2005

We collected inelastic neutron scattering (INS) spectra of homologous disaccharide (C
12
H
22
O
11
)/H
2
O mixtures at a very low temperature by using indirect geometry time-of-flight spectrometer TOSCA at the ISIS pulse neutron facility (DRAL, UK). The aim of this work is to investigate the vibrational behaviour of trehalose, maltose and sucrose/H
2
O mixtures with INS in order to characterize the structural changes induced by these disaccharides on the H
2
O hydrogen-bonded network. A higher degree of ‘crystallinity’ for the trehalose/H
2
O system is observed in the vibrational region corresponding to the ice bending modes. This feature could justify the better
crypto
biotic action of trehalose compared with maltose and sucrose. On the other hand, the better bioprotective effectiveness could be explained by the higher destructuring effect of trehalose, emphasized by the analysis of the librational modes region.
Stride lengths, speed and energy costs in walking ofAustralopithecus afarensis: using evolutionary robotics to predict locomotion of early human ancestors
Authors: Sellers William I , Cain Gemma M , Wang Weijie , Crompton Robin H
Published: July 2005

This paper uses techniques from evolutionary robotics to predict the most energy-efficient upright walking gait for the early human relativeAustralopithecus afarensis, based on the proportions of the 3.2 million year old AL 288-1 ‘Lucy’ skeleton, and matches predictions against the nearly contemporaneous (3.5–3.6 million year old) Laetoli fossil footprint trails. The technique creates gaitsde novoand uses genetic algorithm optimization to search for the most efficient patterns of simulated muscular contraction at a variety of speeds. The model was first verified by predicting gaits for living human subjects, and comparing costs, stride lengths and speeds to experimentally determined values for the same subjects. Subsequent simulations forA. afarensisyield estimates of the range of walking speeds from 0.6 to 1.3 m s−1at a cost of 7.0 J kg−1 m−1for the lowest speeds, falling to 5.8 J kg−1 m−1at 1.0 m s−1, and rising to 6.2 J kg−1 m−1at the maximum speed achieved. Speeds previously estimated for the makers of the Laetoli footprint trails (0.56 or 0.64 m s−1for Trail 1, 0.72 or 0.75 m s−1for Trail 2/3) may have been underestimated, substantially so for Trail 2/3, with true values in excess of 0.7 and 1.0 m s−1, respectively. The predictions conflict with suggestions thatA. afarensisused a ‘shuffling’ gait, indicating rather that the species was a fully competent biped.
Population effects of increased climate variation
Authors: Drake John M
Published: July 2005

Global circulation models predict and numerous observations confirm that anthropogenic climate change has altered high-frequency climate variability. However, it is not yet well understood how changing patterns of environmental variation will affect wildlife population dynamics and other ecological processes. Theory predicts that a population's long-run growth rate is diminished and the chance of population extinction is increased as environmental variation increases. This results from the fact that population growth is a multiplicative process and that long-run population growth rate is the geometric mean of growth rates over time, which is always less than the arithmetic mean. However, when population growth rates for unstructured populations are related nonlinearly to environmental drivers, increasing environmental variation can increase a population's long-run growth rate. This suggests that patterns of environmental variation associated with different aspects of climate change may affect population dynamics in different ways. Specifically, increasing variation in rainfall might result in diminished long-run growth rates for many animal species while increasing variation in temperature might result in increased long-run growth rates. While the effect of rainfall is theoretically well understood and supported by data, the hypothesized effect of temperature is not. Here, I analyse two datasets to study the effect of fluctuating temperatures on growth rates of zooplankton. Results are consistent with the prediction that fluctuating temperatures should increase long-run growth rates and the frequency of extreme demographic events.
Photoreceptor sectral sensitivities in terrestrial animals: adaptations for luminance and colour vision
Authors: Osorio D , Vorobyev M
Published: July 2005

This review outlines how eyes of terrestrial vertebrates and insects meet the competing requirements of coding both spatial and spectral information. There is no unique solution to this problem. Thus, mammals and honeybees use their long-wavelength receptors for both achromatic (luminance) and colour vision, whereas flies and birds probably use separate sets of photoreceptors for the two purposes. In particular, we look at spectral tuning and diversification among ‘long-wavelength’ receptors (sensitivity maxima at greater than 500 nm), which play a primary role in luminance vision. Data on spectral sensitivities and phylogeny of visual photopigments can be incorporated into theoretical models to suggest how eyes are adapted to coding natural stimuli. Models indicate, for example, that animal colour vision—involving five or fewer broadly tuned receptors—is well matched to most natural spectra. We can also predict that the particular objects of interest and signal-to-noise ratios will affect the optimal eye design. Nonetheless, it remains difficult to account for the adaptive significance of features such as co-expression of photopigments in single receptors, variation in spectral sensitivities of mammalian L-cone pigments and the diversification of long-wavelength receptors that has occurred in several terrestrial lineages.
An empirical test of Lanchester's square law: mortality during battles of the fire antSolenopsis invicta
Authors: Plowes Nicola J.R , Adams Eldridge S
Published: July 2005

Lanchester's models of attrition describe casualty rates during battles between groups as functions of the numbers of individuals and their fighting abilities. Originally developed to describe human warfare, Lanchester's square law has been hypothesized to apply broadly to social animals as well, with important consequences for their aggressive behaviour and social structure. According to the square law, the fighting ability of a group is proportional to the square of the number of individuals, but rises only linearly with fighting ability of individuals within the group. By analyzing mortality rates of fire ants (Solenopsis invicta) fighting in different numerical ratios, we provide the first quantitative test of Lanchester's model for a non-human animal. Casualty rates of fire ants were not consistent with the square law; instead, group fighting ability was an approximately linear function of group size. This implies that the relative numbers of casualties incurred by two fighting groups are not strongly affected by relative group sizes and that battles do not disproportionately favour group size over individual prowess.
Experimental manipulation of queen number affects colony sex ratio investment in the highly polygynous antFormica exsecta
Authors: Kümmerli Rolf , Helms Ken R , Keller Laurent
Published: July 2005

In polygynous (multiple queens per nest) ants, queen dispersal is often limited with young queens being recruited within the parental colony. This mode of dispersal leads to local resource competition between nestmate queens and is frequently associated with extremely male-biased sex ratios at the population level. The queen-replenishment hypothesis has been recently proposed to explain colony sex ratio investment under such conditions. It predicts that colonies containing many queens (subject to high local resource competition) should only produce males, whereas colonies hosting few queens (reduced or no local resource competition) should produce new queens in addition to males. We experimentally tested this hypothesis in the antFormica exsectaby manipulating queen number over three consecutive years in 120 colonies of a highly polygynous population. Queens were transferred from 40 colonies into another 40 colonies while queen number was not manipulated in 40 control colonies. Genetic analyses of worker offspring revealed that our treatment significantly changed the number of reproductive queens. The sex ratio of colonies was significantly different between treatments in the third breeding season following the experiment initiation. We found that, as predicted by the queen-replenishment hypothesis, queen removal resulted in a significant increase in the proportion of colonies that produced new queens. These results provide the first experimental evidence for the queen-replenishment hypothesis, which might account for sex ratio specialization in many highly polygynous ant species.
Building an infrastructure for scientific Grid computing: status and goals of the EGEE project
Authors: Gagliardi Fabrizio , Jones Bob , Grey François , Bégin Marc-Elian , Heikkurinen Matti
Published: July 2005

The state of computer and networking technology today makes the seamless sharing of computing resources on an international or even global scale conceivable. Scientific computing Grids that integrate large, geographically distributed computer clusters and data storage facilities are being developed in several major projects around the world. This article reviews the status of one of these projects, Enabling Grids for E-SciencE, describing the scientific opportunities that such a Grid can provide, while illustrating the scale and complexity of the challenge involved in establishing a scientific infrastructure of this kind.
The service architecture of the TeraGyroid experiment
Authors: Haines R , McKeown M , Pickles S.M , Pinning R.L , Porter A.R , Riding M
Published: July 2005

We describe the service architecture of the successful TeraGyroid experiment. In particular we discuss the use of the open Grid service infrastructure (OGSI) to build the services used during the experiment and illustrate the problems we encountered.