bluuebunny/crossref_metadata_2025 huggingface dataset:
Analytical expression for the output voltage of the triple resonance Tesla transformer
Authors: Reed John Randolph
Published: October 2005

An analytical expression for the time-dependent output voltage of the triple resonance Tesla transformer is presented. Presently there does not exist any closed-form solution for the output voltage, and the investigators must use circuit simulators to examine the transformer’s performance. Such simulators are satisfactory in many regards, but they cannot furnish physical insight into the triple resonance device. A governing equation provides this needed insight and opens the way for obtaining optimal high-performance transformers. The present analysis treats the transformer as three oscillatory LC tank circuits feeding a load capacitance. The circuit is assumed to have a very high Q, which is a fundamental design practice for these pulsed power supplies. The formula is exercised using a known triple resonance circuit, and the results closely agree with the analysis of an industry standard circuit simulator.
Benefits of current percolation in superconducting coated conductors
Authors: Rutter N. A. , Durrell J. H. , Blamire M. G. , MacManus-Driscoll J. L. , Wang H. , Foltyn S. R.
Published: October 2005

The critical currents of coated conductors fabricated by metal-organic deposition (MOD) on rolling-assisted biaxially textured substrates (RABiTS) and by pulsed laser deposition (PLD) on ion-beam assisted deposition (IBAD) templates have been measured as a function of magnetic field orientation and compared to films grown on single crystal substrates. By varying the orientation of magnetic field applied in the plane of the film, we are able to determine the extent to which current flow in each type of conductor is percolative. Standard MOD/RABiTS conductors have also been compared to samples whose grain boundaries have been doped by diffusing Ca from an overlayer. We find that undoped MOD/RABiTS tapes have a less anisotropic in-plane field dependence than PLD/IBAD tapes and that the uniformity of critical current as a function of in-plane field angle is greater for MOD/RABiTS samples doped with Ca.
Laser-ablation-assisted microparticle acceleration for drug delivery
Authors: Menezes V. , Takayama K. , Ohki T. , Gopalan J.
Published: October 2005

Localized drug delivery with minimal tissue damage is desired in some of the clinical procedures such as gene therapy, treatment of cancer cells, treatment of thrombosis, etc. We present an effective method for delivering drug-coated microparticles using laser ablation on a thin metal foil containing particles. A thin metal foil, with a deposition of a layer of microparticles is subjected to laser ablation on its backface such that a shock wave propagates through the foil. Due to shock wave loading, the surface of the foil containing microparticles is accelerated to very high speeds, ejecting the deposited particles at hypersonic speeds. The ejected particles have sufficient momentum to penetrate soft body tissues, and the penetration depth observed is sufficient for most of the pharmacological treatments. We have tried delivering 1μm tungsten particles into gelatin models that represent soft tissues, and liver tissues of an experimental rat. Sufficient penetration depths have been observed in these experiments with minimum target damage.
Improved oxide passivation of AlGaN∕GaN high electron mobility transistors
Authors: Gila B. P. , Hlad M. , Onstine A. H. , Frazier R. , Thaler G. T. , Herrero A. , Lambers E. , Abernathy C. R. , Pearton S. J. , Anderson T. , Jang S. , Ren F. , Moser N. , Fitch R. C. , Freund M.
Published: October 2005

MgO has proven effective in the past as a surface passivation layer to minimize current collapse in AlGaN∕GaN high electron mobility transistors (HEMTs). However, MgO is not environmentally stable and more stable oxides need to be developed. MgCaO can be produced that is lattice matched to the GaN. Three samples were grown with 0%, 50% and 75% of Ca, which had respective lattice mismatches of −6.5% for MgO, −1% for Mg0.50Ca0.50O and +4% for Mg0.25Ca0.75O. Drain saturation current in HENTs had increases of 4.5% and 1%, respectively, for Mg0.5Ca0.5O and Mg0.25Ca0.75O passivated devices. However, there was a 10% decrease for the device passivated with pure MgO. This was due to strain applied on the nitride HEMT by the oxide, which is consistent with the piezoelectric effect in the nitride HEMT by the oxide, which is consistent with the piezoelectric effect in the nitride form the lattice mismatch between AlGaN and GaN. From pulsed measurements, HEMTs passivated with Mg0.5Ca0.5O and Mg0.25Ca0.75O showed higher passivation effectiveness (90% of dc current) then the MgO passivated HEMTs (83% dc current). This is due to the closer lattice matching of these calcium containing oxides and the reduction in interface traps associated with lattice mismatch.
Highly oriented zinc blende CdSe nanoneedles
Authors: Shan C. X. , Liu Z. , Hark S. K.
Published: October 2005

Epitaxial growth of highly oriented single-crystalline CdSe nanoneedles on GaAs substrates was obtained by metalorganic chemical vapor deposition using sputter-coated Au as a catalyst. Scanning electron microscopy revealed that they grew tidily along the ⟨110⟩ crystallographic directions and in parallel to the same directions of the substrate. Their density could be adjusted by applying different amounts of the catalyst. X-ray diffraction, transmission electron lattice imaging and electron diffraction showed that they have the zinc blende structure, which is rare for CdSe. Polarized photoluminescence studies on individual nanoneedles verify the zinc blende structure of the needles, and the strong near band edge emissions and no deep-level emissions reveal their good optical quality.
Near-field scanning optical microscopic transient lens for carrier dynamics study in InGaN∕GaN
Authors: Okamoto Koichi , Scherer Axel , Kawakami Yoichi
Published: October 2005

Time-resolved microscopic transient lens (TR-M-TL) and near-field scanning optical microscopic transient lens (NSOM-TL) were performed to reveal temporal and spatial behavior of carrier dynamics in InGaN∕GaN quantum wells. The carrier and thermal dynamics were observed through the time profile of the TR-M-TL signal. Also, NSOM-photoluminescence and NSOM-TL images were observed at the same time. By comparing these two images, both radiative and nonradiative recombination centers in InGaN active layer were unambiguously discriminated with submicrometer scale. Such nonradiative carrier dynamics has been difficult to observe by conventional techniques in spite of its importance.
Low-frequency noise spectroscopy in Au∕n-GaAs Schottky diodes with InAs quantum dots
Authors: Tsormpatzoglou A. , Hastas N. A. , Tassis D. H. , Dimitriadis C. A. , Kamarinos G. , Frigeri P. , Franchi S. , Gombia E. , Mosca R.
Published: October 2005

The temperature dependence of low-frequency noise in Au∕n-GaAs Schottky diodes, with InAs quantum dots (QDs) embedded in the GaAs confining layers, is investigated in the temperature range of 77–298 K and at frequencies from 1 Hz to 5 kHz. Diodes prepared on samples with similar structure but without QDs exhibit 1∕f behavior. In diodes containing QDs, in addition to the 1∕f noise at low frequencies, generation-recombination (g-r) noise at higher frequencies was observed, related to single energy traps in the GaAs layer. Analysis of the experimental data has shown that the g-r noise is related to three traps with activation energies 0.234, 0.09 and 0.075 eV, corresponding to the ground and two excited confined states in the QDs.
Energy absorption of a nanoporous system subjected to dynamic loadings
Authors: Surani Falgun B. , Kong Xinguo , Panchal Deepam B. , Qiao Yu
Published: October 2005

In a previous study [X. Kong and Y. Qiao, Appl. Phys. Lett. 86, 151919 (2005)], we analyzed the energy absorption behaviors of a nanoporous system subjected to quasi-static loadings. In this work, the performance of similar systems under dynamic loadings is investigated through a Hopkinson bar experiment. The energy absorption efficiency increases significantly with the loading rate, which is attributed to the effect of internal friction.
Effects of Mn doping on the properties of FeCr2−xMnxS4
Authors: Qu Zhe , Tan Shun , He Kuang , Xu Jiangtao , Zhang Yuheng
Published: October 2005

In this letter, the effects of Mn doping on the magnetic properties, resistivity, and magnetoresistance of FeCr2−xMnxS4 (0⩽x⩽0.1) are reported. Both the Curie temperature Tc and the maximum value of the magnetization increase with Mn content, rather than decrease as found in the cases of substituting nonmagnetic ions for Cr. These effects are attributed to the fact that Mn participates in the magnetic interaction networks and strengthens the magnetism of the Cr sublattice. Interestingly, it is found that the resistivity decreases while the maximum magnetoresistance increases and shifts to higher temperature with increasing doping level. These are discussed in the context that more itinerant eg electrons are introduced with substitution of Mn for Cr.
Overcoming the barrier to 1000A∕cm width superconducting coatings
Authors: Foltyn S. R. , Wang H. , Civale L. , Jia Q. X. , Arendt P. N. , Maiorov B. , Li Y. , Maley M. P. , MacManus-Driscoll J. L.
Published: October 2005

Remarkable progress has been made in the development of YBa2Cu3O7−δ (YBCO)-based coated conductors, and the problems of continuous processing of commercially viable tape lengths are being rapidly solved by companies around the world. However, the current carried by these tapes is presently limited to about 100A for a 1-cm-wide tape, and this is due to a rapid decrease of critical current density (Jc) as the coating thickness is increased. We have now overcome this problem by separating relatively thin YBCO layers with very thin layers of CeO2. Using this multilayer technology, we have achieved Jc values on metal substrates of up to 4.0MA∕cm2 (75K, self-field) in films as thick as 3.5μm, for an extrapolated current of 1400A∕cm width.
Ultrafast control of multiple filamentation by ultrafast laser pulses
Authors: Liu Jiansheng , Schroeder Hartmut , Chin See Leang , Li Ruxin , Xu Zhizhan
Published: October 2005

Control of multiple filamentation by laser-induced microlens effect due to a nonlinear interaction of two overlapping laser beams inside a glass plate was demonstrated. Individual or multiple spots on the white light pattern which is a product of multiple filamentation through a mesh can be switched on and off with a very high contrast ratio on a femtosecond time scale. This phenomenon can find applications such as ultrafast optical switch and high-speed sampling.
X-ray diffraction imaging of Al2O3 nanoparticles embedded in an amorphous matrix
Authors: Dilanian Ruben A. , Nikulin Andrei Y.
Published: October 2005

An experimental “momentum transfer” x-ray diffraction imaging technique is suggested and tested for nondestructive determination of the shape and size of Al2O3 nanoscale particles embedded in an amorphous polymer matrix. An advantage of the proposed technique is that it does not require coherent x rays or a beamstop to block the direct beam. A two-dimensional image of an average Al2O3 nanoparticle has been reconstructed using the Gerchberg–Saxton method, with a spatial resolution of 2.5 nm. The shape of the resulting image yielded the average size of the nanoparticle to be approximately 50 nm, which is in excellent agreement with the expected value.
High ductility of a metal film adherent on a polymer substrate
Authors: Xiang Yong , Li Teng , Suo Zhigang , Vlassak Joost J.
Published: October 2005

In recent development of deformable electronics, it has been noticed that thin metal films often rupture at small tensile strains. Here we report experiments with Cu films deposited on polymeric substrates and show that the rupture strains of the metal films are sensitive to their adhesion to the substrates. Well-bonded Cu films can sustain strains up to 10% without appreciable cracks and up to 30% with discontinuous microcracks. By contrast, poorly bonded Cu films form channel cracks at strains about 2%. The cracks form by a mixture of strain localization and intergranular fracture. The films rupture at large strains when the localization is retarded by the adherent substrates.
High structural and optical quality 1.3μm GaInNAs∕GaAs quantum wells with higher indium content grown by molecular-beam expitaxy
Authors: Zhang Shiyong , Niu Zhichuan , Ni Haiqiao , Wu Donghai , He Zhenhong , Sun Zheng , Han Qin , Wu Ronghan
Published: October 2005

High structural and optical quality 1.3μm GaInNAs∕GaAs quantum well (QW) samples with higher (42.5%) indium content were successfully grown by molecular-beam epitaxy. The cross-sectional transmission electron microscopy measurements reveal that there are no structural defects in such high indium content QWs. The room-temperature photoluminescence peak intensity of the GaIn0.425NAs∕GaAs (6nm∕20nm) 3QW is higher than, and the full width at half maximum is comparable to, that of In0.425GaAs∕GaAs 3QW, indicating improved optical quality caused by strain compensation effect of introducing N to the high indium content InGaAs epilayer.
Resistivity minima and Kondo effect in ferromagnetic GaMnAs films
Authors: He H. T. , Yang C. L. , Ge W. K. , Wang J. N. , Dai X. , Wang Y. Q.
Published: October 2005

The temperature dependence of the resistivity of ferromagnetic GaMnAs, as-grown or low-temperature-annealed samples is measured from 2to290K. A resistivity minimum is observed with a corresponding temperature TM around 10K for each sample. Below TM, the resistivity exhibits logarithmic temperature dependence, as αln(T), and α is independent of the external magnetic field up to 9T. Such behavior is explained in terms of the Kondo effect arising from the presence of Mn interstitials in the GaMnAs samples. In addition, a well-defined T-squared dependence of resistivity is found in the temperature range between TM and the Curie temperature (TC), which is attributed to single magnon scattering.
Numerical simulations of contact resistance in organic thin-film transistors
Authors: Hill I. G.
Published: October 2005

The origin of the source/drain contact resistance reported in studies of pentacene-based organic thin-film transistors (OTFTs) has been investigated using numerical device simulations. Quantitative agreement with published contact resistance values is obtained, using reasonable values for the physical parameters describing both the semiconductor material and the metal/organic interfaces. In particular, the difference in contact resistance measured in top and bottom contact OTFTs has been reproduced.
The northern Australian beef industry, a snapshot. 1. Regional enterprise activity and structure
Authors: Bortolussi G. , McIvor J. G. , Hodgkinson J. J. , Coffey S. G. , Holmes C. R.
Published: October 2005

During 1996 and 1997, a survey examined the business activities of 375 selected northern Australian beef producers during the 1991 and 1992 to 1995 and 1996 financial years. The producers represented a broad cross-section of the northern beef industry in terms of geographical location, size of enterprise and herd, and ownership structures. The survey examined the enterprise structures and herd productivity of the participating properties. A diverse range of production activities were carried out with breeding and finishing, of which breeding stores and live cattle export being the most common activities. About 50% of the survey properties were run in conjunction with another property, both of which tended to be located in the same survey region. The additional properties served various purposes, depending on their location. There was evidence of specialist roles for the additional properties.
The purchase of store cattle tended to be an opportunistic activity with younger cattle (<2 years old) being most preferred. Survey properties tended to target a range of markets; Northern Territory and northern Western Australian properties being the most likely to target a single market (live export). Aspiring to supply the slaughter markets was of greatest interest to Queensland beef producers. Aspiring to supply the USA manufacturing beef market was lowest where interest in live export was greatest. During the survey period, the USA manufacturing beef market, store and live cattle export markets were important outlets for cattle.
Many herd and pasture-related improvements were planned to boost profitability in the 5 years post-survey (1997–2002). Increasing turn-off weight and branding rate, and decreasing turn-off age were of greatest interest to surveyed beef producers. Pasture improvement and improving pasture management also rated highly.
The survey data indicated that the female genotype of the northern Australian herd had changed significantly over a 10- and 30-year period, with Bos indicus, Bos indicus cross and Taurindicus breeds being the most commonly reported breeds. The bull breeds present in regional herds suggest crossbreeding is occurring in conjunction with pure breeding. Most herds had more than 1 bull and female breed. Regional patterns were also found to exist for female and bull breeds with Bos indicus being common in herds in the northern parts of the survey area and Taurindicus breeds popular in southern herds.
The results of this survey are discussed in relation to future developments in the northern Australian beef industry.
The northern Australian beef industry, a snapshot. 3. Annual liveweight gains from pasture based systems
Authors: Bortolussi G. , McIvor J. G. , Hodgkinson J. J. , Coffey S. G. , Holmes C. R.
Published: October 2005

The herd performance of 375 northern Australian beef producers during the 1991 and 1992 to 1995 and 1996 financial years was surveyed in 1996 and 1997. Estimates were made of annual liveweight gain from production systems based on native and improved pastures together with hormonal growth promotant use and supplementation practices.
The most commonly used pasture communities for growing and finishing cattle were black speargrass and brigalow communities in Central Coastal Queensland and the Central Highlands; black speargrass in Northern Queensland; Mitchell grass and gidgee in Central Western and North-west Queensland; Mitchell grass in the Northern Territory and northern Western Australia regions and brigalow–softwood scrub in the Maranoa South West.
There was considerable variation and overlap in the production ranges of the various pasture communities. The estimates and ranges of annual liveweight gains were comparable with measurements from scientific and commercial studies for 3 major pasture communities (black speargrass, brigalow and Mitchell grass). On this basis, the annual liveweight gain data are considered to represent sound estimates of performance from the pasture communities and husbandry systems in use in northern Australia. Mean annual gains for pasture communities in the more northern regions tended to be <150 kg/year.
Half the survey group used hormonal growth promotants but use varied between regions with lowest levels in Central Coastal Queensland (30%) and highest usage in the Central Highlands (59%). Steers and bullocks were the most commonly implanted class of cattle. Supplementation periods tended to be longest in more northern regions. Nitrogen was a component of >90% of the supplements offered. The percentage of producers supplementing various classes of cattle varied widely (0–77%). Steers were often the least supplemented class and weaners were the most common. The highest percentage of producers (>68%) supplementing weaners was found in North-west and Northern Queensland, the Northern Territory and northern Western Australia.
Significant correlations explaining 3–23% of the variance were found between annual liveweight gain and latitude and/or longitude for native black speargrass and Mitchell grass pasture communities and improved brigalow pastures. Generally, annual liveweight gain increased with increasing latitude and longitude.
The results are discussed in relation to herd management practices and sources of variation in the northern Australian production environment.
The northern Australian beef industry, a snapshot. 4. Condition and management of natural resources
Authors: Bortolussi G. , McIvor J. G. , Hodgkinson J. J. , Coffey S. G. , Holmes C. R.
Published: October 2005

Natural resource management practices were surveyed on 375 northern Australian beef properties in 8 regions during 1996–97. These producers represented a broad cross section of the beef industry in terms of geographical location, size of enterprise, and herd and ownership structures.
More than 48% of producers reported land degradation (erosion, salinity, weeds, etc.) and >68% reported woody weeds on their properties. Eucalypt (Eucalyptus and Corymbia spp.) and wattle (Acacia spp.) regrowth were universally common native woody weeds. Parkinsonia (Parkinsonia aculeata) was widespread across all survey regions occurring with the greatest frequency in northern regions. A range of native and exotic woody weed species were regionally significant. Brigalow (Acacia harpophylla) regrowth was mainly reported in the central Queensland and Maranoa South West regions. Prickly acacia (Acacia nilotica) was mainly reported in central and north-west Queensland. Rubber vine (Cryptostegia grandiflora) was mainly reported in northern Queensland with a significant presence in central coastal and north-west Queensland. Infestations with multiple weed species were common. Although many producers reported the presence of problem woody weeds, only 3–29% indicated that weed management was practised.
Most producers (67–100%) used fire. The intended purpose of fire varied across survey regions but fire was commonly used to reduce rank material, reduce fire risk, control woody weeds and for grazing management. Seasonal conditions and variability restricted fire use.
Assessment by visual observation was a commonly used practice for determining stocking rate. Between 4–20% of producers were using visual observation combined with some form of calculation of stocking rate at the end of the growing season to determine stocking rate. A majority (>67%) of producers used some form of paddock spelling or regeneration practice. Many producers (47–89%) considered that they used conservative stocking rates. Carrying sufficient stock to meet income requirements was significantly (P<0.05) correlated with the percentage of producers reporting woody weeds as a problem on their property.
In the 5 years preceding the survey, >66% of producers had increased the number of stock watering points, and more than 85% of producers had erected fencing. Most fencing was for new paddocks and laneways, or to replace old fences, and was not associated with new stock watering points. However, the installation of new stock watering points was associated with the creation of new paddocks. Planned future fencing focused on creating new paddocks or laneways or replacing old fences.
The results are discussed in relation to contemporary natural resource management issues and the future approaches to and challenges of implementing sustainable rangeland management.
Opportunities for future Australian dairy systems: a review
Authors: García S. C. , Fulkerson W. J.
Published: October 2005

During the last decade, Australian dairy farmers have been challenged to increase total factor productivity (the ratio between the rate of increase in total output and the rate of increase in the use of all inputs) in order to attenuate the negative effects of a steady decline in the terms of trade over the same period of time. Overall, the increase in total factor productivity has been low (1.5%) and farmers are questioning the most appropriate production system for the future. In an attempt to address this central question, we first identified the nature of the key pressures dairy farmers in Australia are likely to face in the future, namely labour and feed related issues. We then discuss major opportunities for developing new dairy production systems based on increased efficiency in the use of land and cows and on increasing the efficiency of labour management and lifestyle. We do not attempt to provide the best futuristic option for dairy systems in Australia. Instead, this review discusses key areas of the production system with potential to impact positively on any or all the physical, economic and labour-related aspects of modern dairy farming. By so doing, this review highlights the research questions that need to be addressed now in order to provide Australian dairy farmers with improved tools to manage their production systems in the future.
Effectiveness of grazing and herbicide treatments for lucerne removal before cropping in southern New South Wales
Authors: Davies S. L. , Virgona J. M. , McCallum M. H. , Swan A. D. , Peoples M. B.
Published: October 2005

The difficulty of reliably removing an established lucerne pasture before cropping has been identified as a major problem with phase-farming systems on mixed farms. A series of experiments were undertaken on established lucerne stands at the Ginninderra Experimental Station in the Australian Capital Territory (ACT) and at the Temora Research Station in southern New South Wales (NSW) to compare the ability of grazing, either alone or in combination with herbicides, to remove a lucerne pasture. A pilot study at the Ginninderra Experimental Station in 1998–99 utilised a high stocking rate (30 dry sheep equivalents [dse]/ha), while the main study at the Ginninderra Experimental Station and the Temora Research Station in 1999–2000 used a lower stocking rate (10–12 dse/ha) considered to be closer to farmer practice in the region. Continuous grazing at the high stocking rate removed 73% of the lucerne stand over 3 months. In contrast, the stocking rates applied in the main study proved too low to substantially impact on lucerne survival at both the ACT and NSW sites (13–23% removal) under the good seasonal conditions experienced in 1999–2000 even though the pastures were continuously grazed for 8–9 months. The use of herbicides both alone or in conjunction with grazing greatly improved lucerne removal in both studies. However, herbicide efficacy was variable (53–100% removal), and seemed to be related to the time of year it was applied, the period of lucerne regrowth or the amount of rainfall before herbicide application.
An additional on-farm study was undertaken near Junee Reefs in southern NSW between 2001 and 2003 that compared the survival of a range of lucerne cultivars under simulated hay-cutting (mown) and commercial grazing regimes. Dry conditions during 2002–03 resulted in a decline in lucerne frequency at about 50% in mown control plots. Grazing increased the stand decline, particularly for many winter-active cultivars where lucerne frequency was reduced by up to 70–93%.
It was concluded that: (i) continuous grazing for prolonged periods can be effective at removing lucerne, but the rate of lucerne loss will be influenced by both stocking rate and rainfall; (ii) the application of herbicides can improve lucerne removal either in association with, or in the absence of grazing; however, herbicide efficacy appeared to be dependent upon the physiological status of the lucerne plants and/or the environmental conditions before application; and (iii) cultivar responses indicated that lucerne types could potentially be developed for phase-farming systems with increased susceptibility to grazing mismanagement.
Low mobility of phosphatidylinositol 4,5-bisphosphate underlies receptor specificity of Gq-mediated ion channel regulation in atrial myocytes
Authors: Cho Hana , Kim Yeon A. , Yoon Jin-Young , Lee Doyun , Kim Jae Ho , Lee Suk Ho , Ho Won-Kyung
Published: October 2005

We have shown previously that cardiac G protein-gated inwardly rectifying K
+
(GIRK) channels are inhibited by Gq protein-coupled receptors (GqPCRs) via phosphatidylinositol 4,5-bisphosphate (PIP
2
) depletion in a receptor-specific manner. To investigate the mechanism of receptor specificity, we examined whether the activation of GqPCRs induces localized PIP
2
depletion. When we applied endothelin-1 to the bath, GIRK channel activities recorded in cell-attached patches were not changed, implying that PIP
2
signal is not diffusible but is a localized signal. To test this possibility, we directly measured lateral diffusion by introducing fluorescence-labeled phosphoinositides to a small area of the membrane with patch pipettes. After pipettes were attached, phosphatidylinositol 4-monophosphate or phosphatidylinositol diffused rapidly to the entire membrane, whereas PIP
2
was confined to the membrane patch inside the pipette. The confinement of PIP
2
was disrupted after cytochalasin D treatment, suggesting that the cytoskeleton is responsible for the low mobility of PIP
2
. The diffusion coefficient (
D
) of PIP
2
in the plasma membrane measured with the fluorescence recovery after photobleaching technique was 0.00039 μm
2
/s(
n
= 6), which is markedly lower than
D
of phosphatidylinositol (5.8 μm
2
/s,
n
= 5). Simulation of PIP
2
concentration profiles by the diffusion model confirms that when
D
is small, the kinetics of PIP
2
depletion at different distances from phospholipase C becomes similar to the characteristic kinetics of GIRK inhibition by different agonists. These results imply that PIP
2
depletion is localized adjacent to GqPCRs because of its low mobility, and that spatial proximity of GqPCR and the target protein underlies the receptor specificity of PIP
2
-mediated signaling.
Crystal structures of oxidized and reduced mitochondrial thioredoxin reductase provide molecular details of the reaction mechanism
Authors: Biterova Ekaterina I. , Turanov Anton A. , Gladyshev Vadim N. , Barycki Joseph J.
Published: October 2005

Thioredoxin reductase (TrxR) is an essential enzyme required for the efficient maintenance of the cellular redox homeostasis, particularly in cancer cells that are sensitive to reactive oxygen species. In mammals, distinct isozymes function in the cytosol and mitochondria. Through an intricate mechanism, these enzymes transfer reducing equivalents from NADPH to bound FAD and subsequently to an active-site disulfide. In mammalian TrxRs, the dithiol then reduces a mobile C-terminal selenocysteine-containing tetrapeptide of the opposing subunit of the dimer. Once activated, the C-terminal redox center reduces a disulfide bond within thioredoxin. In this report, we present the structural data on a mitochondrial TrxR, TrxR2 (also known as TR3 and TxnRd2). Mouse TrxR2, in which the essential selenocysteine residue had been replaced with cysteine, was isolated as a FAD-containing holoenzyme and crystallized (2.6 Å;R= 22.2%;Rfree= 27.6%). The addition of NADPH to the TrxR2 crystals resulted in a color change, indicating reduction of the active-site disulfide and formation of a species presumed to be the flavin–thiolate charge transfer complex. Examination of the NADP(H)-bound model (3.0 Å;R= 24.1%;Rfree= 31.2%) indicates that an active-site tyrosine residue must rotate from its initial position to stack against the nicotinamide ring of NADPH, which is juxtaposed to the isoalloxazine ring of FAD to facilitate hydride transfer. Detailed analysis of the structural data in conjunction with a model of the unusual C-terminal selenenylsulfide suggests molecular details of the reaction mechanism and highlights evolutionary adaptations among reductases.
Deleted in liver cancer 2
(
DLC2
) suppresses cell transformation by means of inhibition of RhoA activity
Authors: Leung Thomas Ho-Yin , Ching Yick-Pang , Yam Judy Wai Ping , Wong Chun-Ming , Yau Tai-On , Jin Dong-Yan , Ng Irene Oi-Lin
Published: October 2005

The
deleted in liver cancer 2
(
DLC2
) gene, located at chromosome 13q12.3, is a recently identified tumor suppressor gene. The gene is frequently underexpressed in human hepatocellular carcinoma, and its chromosomal region shows frequent deletion. DLC2 encodes a unique RhoGTPase-activating protein (RhoGAP) specific for small RhoGTPases, RhoA, and Cdc42. With bioinformatic analysis, we have identified four different isoforms of
DLC2
, which we named DLC2α, DLC2β, DLC2γ, and DLC2δ. Three of the isoforms contain the RhoGAP domain, namely, DLC2α, DLC2β, and DLC2γ. Ectopic expression of these three isoforms in mouse fibroblasts showed cytoplasmic localization. Of interest, overexpression of these isoforms suppressed the lysophosphatidic acid-induced stress fiber formation in mouse fibroblasts and changed the morphology of the transfected cells from angular and spindle to round. Furthermore, the RhoA pull-down assay demonstrated a remarkable reduction in RhoA activity in the DLC2 transiently transfected cells. In contrast, cells transfected with inactive DLC2 GAP-mutant remained unchanged in cell morphology, actin stress fiber formation, and RhoA activity. HepG2 hepatoma cells stably transfected with the DLC2γ isoform also changed to a round morphology, as in mouse fibroblasts. Of significance, these DLC2γ stable transfectants showed marked suppression in cell proliferation, motility, and transformation, and there was a remarkable reduction in
in vivo
RhoA activity in these cells. These results suggest that
DLC2
exhibits its tumor suppressor functions
in vivo
as a GAP specific for RhoA, exerting its effects in suppression of cytoskeleton reorganization, cell growth, cell migration, and transformation.
Generalized epileptic discharges show thalamocortical activation and suspension of the default state of the brain
Authors: Gotman J. , Grova C. , Bagshaw A. , Kobayashi E. , Aghakhani Y. , Dubeau F.
Published: October 2005

Our objective was to evaluate the brain regions showing increased and decreased metabolism in patients at the time of generalized bursts of epileptic discharges in order to understand their mechanism of generation and effect on brain function. By recording the electroencephalogram during the functional MRI, changes in the blood oxygenation level-dependent signal were obtained in response to epileptic discharges observed in the electroencephalogram of 15 patients with idiopathic generalized epilepsy. A group analysis was performed to determine the regions of positive (activation) and negative (deactivation) blood oxygenation level-dependent responses that were common to the patients. Activations were found bilaterally and symmetrically in the thalamus, mesial midfrontal region, insulae, and midline and bilateral cerebellum and on the borders of the lateral ventricles. Deactivations were bilateral and symmetrical in the anterior frontal and parietal regions and in the posterior cingulate gyri and were seen in the left posterior temporal region. Activations in thalamus and midfrontal regions confirm known involvement of these regions in the generation or spread of generalized epileptic discharges. Involvement of the insulae in generalized discharges had not previously been described. Cerebellar activation is not believed to reflect the generation of discharges. Deactivations in frontal and parietal regions remarkably followed the pattern of the default state of brain function. Thalamocortical activation and suspension of the default state may combine to cause the actual state of reduced responsiveness observed in patients during spike-and-wave discharges. This brief lapse of responsiveness may therefore not result only from the epileptic discharge but also from its effect on normal brain function.
Dynamics of the acetylcholine receptor pore at the gating transition state
Authors: Mitra Ananya , Cymes Gisela D. , Auerbach Anthony
Published: October 2005

Neuromuscular acetylcholine receptors (AChRs) are ion channels that alternatively adopt stable conformations that either allow (open) or prohibit (closed) ionic conduction. We probed the dynamics of pore (M2) residues at the diliganded gating transition state by using single-channel kinetic and rate-equilibrium free energy relationship (Φ-value) analyses of mutant AChRs. The mutations were at the equatorial (9′) position of the α, β, and ε subunits (
n
= 15) or at sites between the equator and the extracellular domain in the α-subunit (
n
= 8). We also studied AChRs having only one of the two α-subunits mutated. The results indicate that the α-subunit, like the δ-subunit, has a region of flexure near the middle of M2, that the two α-subunits experience distinct energy barriers to gating at the equator (but not elsewhere), and that the collective subunit motions at the equator are asymmetric during the AChR gating isomerization.
DNA and mRNA elements with complementary responses to hemin, antioxidant inducers, and iron control ferritin-L expression
Authors: Hintze Korry J. , Theil Elizabeth C.
Published: October 2005

Ferritins, an ancient family of protein nanocages, concentrate iron in iron–oxy minerals for iron–protein biosynthesis and protection against oxy radical damage. Of the two genetic mechanisms that regulate rates of ferritin-L synthesis, DNA transcription and mRNA translation, more is known about mRNA regulation where iron targets complexes of an mRNA structure, the iron-responsive element (IRE) sequence, and ferritin IRE repressors (iron regulatory proteins 1 and 2). Neither the integration of mRNA and DNA regulation nor the ferritin-L DNA promoter are well studied. We now report the combined effects of DNA transcription and mRNA translation regulation of ferritin-L synthesis. First, the promoter of human ferritin-L, encoding the animal-specific subunit associated with human diseases, was identified, and contained an overlapping Maf recognition element (MARE) and antioxidant responsive element (ARE) that was positively regulated by
tert
-butylhydroquinone, sulforaphane, and hemin with responses comparable to thioredoxin reductase (ARE regulator) or quinone reductase (MARE/ARE regulator). Iron, a poor regulator of the ferritin-L promoter, was 800 times less effective than sulforaphane. Combining the ferritin-L MARE/ARE and IRE produced a response to hemin that was 3-fold greater than the sum of responses of the MARE/ARE or IRE alone. Regulation of ferritin-L by a MARE/ARE DNA sequence emphasizes the importance of ferritin-L in oxidative stress that complements the mRNA regulation in iron stress. Combining DNA and mRNA mechanisms of regulation, as for ferritin-L, illustrates the advantages of using two types of genetic targets to achieve sensitive responses to multiple signals.
Cenozoic continental climatic evolution of Central Europe
Authors: Mosbrugger Volker , Utescher Torsten , Dilcher David L.
Published: October 2005

Continental climate evolution of Central Europe has been reconstructed quantitatively for the last 45 million years providing inferred data on mean annual temperature and precipitation, and winter and summer temperatures. Although some regional effects occur, the European Cenozoic continental climate record correlates well with the global oxygen isotope record from marine environments. During the last 45 million years, continental cooling is especially pronounced for inferred winter temperatures but hardly observable from summer temperatures. Correspondingly, Cenozoic cooling in Central Europe is directly associated with an increase of seasonality. In contrast, inferred Cenozoic mean annual precipitation remained relatively stable, indicating the importance of latent heat transport throughout the Cenozoic. Moreover, our data support the concept that changes in atmospheric CO2concentrations, although linked to climate changes, were not the major driving force of Cenozoic cooling.
Partition congruences and the Andrews-Garvan-Dyson crank
Authors: Mahlburg Karl
Published: October 2005

In 1944, Freeman Dyson conjectured the existence of a “crank” function for partitions that would provide a combinatorial proof of Ramanujan's congruence modulo 11. Forty years later, Andrews and Garvan successfully found such a function and proved the celebrated result that the crank simultaneously “explains” the three Ramanujan congruences modulo 5, 7, and 11. This note announces the proof of a conjecture of Ono, which essentially asserts that the elusive crank satisfies exactly the same types of general congruences as the partition function.
Alteration of phosphatidylinositol 3-kinase cascade in the multilobulated nuclear formation of adult T cell leukemia/lymphoma (ATLL)
Authors: Fukuda Ryu-ichi , Hayashi Ayako , Utsunomiya Atae , Nukada Yuko , Fukui Rie , Itoh Katsuhiko , Tezuka Katsunari , Ohashi Kazumasa , Mizuno Kensaku , Sakamoto Manabu , Hamanoue Masahiro , Tsuji Takashi
Published: October 2005

Adult T cell leukemia/lymphoma (ATLL) has been characterized as one of the most aggressive human neoplasias and its incidence is thought to be caused by both genetic and epigenetic alterations to the host cellular genes of T cells infected with human T cell leukemia virus type I (HTLV-I). A multilobulated nuclear appearance is an important diagnostic marker of ATLL, and we have now identified that the molecular mechanisms underlying these formations occur through microtubule rearrangement via phosphatidylinositol 3-kinase (PI3-kinase) activation by AILIM/ICOS signaling. We also show that PTEN and/or SHIP-1, which are PIP3 inositol phosphatases that inhibit the activation of downstream effectors of the PI3-kinase cascade, are disrupted in both ATLL neoplasias and in multilobulated nuclei-forming Jurkat cells. This down-regulation of PTEN was found to be essential for the formation of ATLL-type nuclear lobules. Furthermore, PI3-kinase and PTEN activities were observed to be closely associated with cellular proliferation. Thus, our results suggest that alteration of PI3-kinase signaling cascades, as a result of the down-regulation of inositol phosphatases, induces ATLL-type multilobulated nuclear formation and is also associated with the cellular proliferation of malignant T cell leukemias/lymphomas.
Inhibition of vagally mediated immune-to-brain signaling by vanadyl sulfate speeds recovery from sickness
Authors: Johnson Daniel R. , O'Connor Jason C. , Dantzer Robert , Freund Gregory G.
Published: October 2005

To the ill patient with diabetes, the behavioral symptoms of sickness such as fatigue and apathy are debilitating and can prevent recuperation. Here we report that peripherally administered insulin-like growth factor 1 (IGF-1) attenuates LPS-dependent depression of social exploration (sickness) in nondiabetic (db/+) but not in diabetic (db/db) mice. We show that the insulin/IGF-1 mimetic vanadyl sulfate (VS) is effective at augmenting recovery from sickness in bothdb/+ anddb/dbmice. Specifically, peak illness was reached at 2 h for both VS and control animals injected with LPS, and VS mice recovered 50% faster than non-VS-treated animals. Examination of the mechanism of VS action indb/+ mice showed that VS paradoxically augmented peritoneal macrophage responsivity to LPS, increasing both peritoneal andex vivomacrophage production of IL-1β and IL-6 but not TNF-α. The effects of VS in promoting recovery from sickness were not restricted to LPS, because they were also observed after direct administration of IL-1β. To explore the possibility that VS impairs immune-to-brain communication via vagal afferents, the vagally mediated satiety-inducing effects of cholecystokinin 8 were tested indb/+ mice. Cholecystokinin decreased food intake in saline-injected mice but not in VS-treated mice. VS also inhibited LPS-dependent up-regulation of IL-1β and IL-6 mRNA in the brain, while increasing by 50% the cerebral expression of transcripts of the specific antagonist of IL-1 receptors IL-1RA and IL-1R2. Taken together, these data indicate that VS improves recovery from LPS-induced sickness by blocking vagally mediated immune-to-brain signaling and by up-regulating brain expression of IL-1β antagonists.
Making ATP
Authors: Xing Jianhua , Liao Jung-Chi , Oster George
Published: October 2005

We present a mesoscopic model for ATP synthesis by F
1
F
o
ATPase. The model combines the existing experimental knowledge of the F
1
enzyme into a consistent mathematical model that illuminates how the stages in synthesis are related to the protein structure. For example, the model illuminates how specific interactions between the γ, ε, and α
3
β
3
subunits couple the F
o
motor to events at the catalytic sites. The model also elucidates the origin of ADP inhibition of F
1
in its hydrolysis mode. The methodology we develop for constructing the structure-based model should prove useful in modeling other protein motors.
Dynamic effects of antibody-dependent enhancement on the fitness of viruses
Authors: Cummings Derek A. T. , Schwartz Ira B. , Billings Lora , Shaw Leah B. , Burke Donald S.
Published: October 2005

Antibody-dependent enhancement (ADE), a phenomenon in which viral replication is increased rather than decreased by immune sera, has been observed
in vitro
for a large number of viruses of public health importance, including flaviviruses, coronaviruses, and retroviruses. The most striking
in vivo
example of ADE in humans is dengue hemorrhagic fever, a disease in which ADE is thought to increase the severity of clinical manifestations of dengue virus infection by increasing virus replication. We examine the epidemiological impact of ADE on the prevalence and persistence of viral serotypes. Using a dynamical system model of
n
cocirculating dengue serotypes, we find that ADE may provide a competitive advantage to those serotypes that undergo enhancement compared with those that do not, and that this advantage increases with increasing numbers of cocirculating serotypes. Paradoxically, there are limits to the selective advantage provided by increasing levels of ADE, because greater levels of enhancement induce large amplitude oscillations in incidence of all dengue virus infections, threatening the persistence of both the enhanced and nonenhanced serotypes. Although the models presented here are specifically designed for dengue, our results are applicable to any epidemiological system in which partial immunity increases pathogen replication rates. Our results suggest that enhancement is most advantageous in settings where multiple serotypes circulate and where a large host population is available to support pathogen persistence during the deep troughs of ADE-induced large amplitude oscillations of virus replication.
A spider that feeds indirectly on vertebrate blood by choosing female mosquitoes as prey
Authors: Jackson Robert R. , Nelson Ximena J. , Sune Godfrey O.
Published: October 2005

Spiders do not feed directly on vertebrate blood, but a small East African jumping spider (Salticidae),
Evarcha culicivora
, feeds indirectly on vertebrate blood by choosing as preferred prey female mosquitoes that have had recent blood meals. Experiments show that this spider can identify its preferred prey by sight alone and by odor alone. When presented with two types of size-matched motionless lures,
E. culicivora
consistently chose blood-fed female mosquitoes in preference to nonmosquito prey, male mosquitoes, and sugar-fed female mosquitoes (i.e., females that had not been feeding on blood). When the choice was between mosquitoes of different sizes (both blood- or both sugar-fed), small juveniles chose the smaller prey, whereas adults and larger juveniles chose the larger prey. However, preference for blood took precedence over preference for size (i.e., to get a blood meal, small individuals took prey that were larger than the preferred size, and larger individuals took prey that were smaller than the preferred size). When presented with odor from two prey types,
E. culicivora
approached the odor from blood-fed female mosquitoes significantly more often the odor of the prey that were not carrying blood.