bluuebunny/crossref_metadata_2025 huggingface dataset:
Two types of cone bipolar cells express voltage-gated Na+ channels in the rat retina
Authors: CUI JINJUAN , PAN ZHUO-HUA
Published: December 2008

Two groups of retinal cone bipolar cells (CBCs) in rats were found to express voltage-gated Na+ channels. The axon terminals of the first group stratify in sublamina 2 of the inner plexiform layer (IPL) and partially overlap with the OFF-cholinergic band. This group was identified as type 3 CBCs. The axon terminals of the second group stratify in sublamina 3 of the IPL, slightly distal to the ON-cholinergic band. Cells of this second group resemble type 5 CBCs. In addition, we observed another group of ON-type CBCs with terminal stratification similar to that of the second group. However, this latter group did not show any Na+ current, instead exhibiting a large hyperpolarization-activated cyclic nucleotide-gated cation current, suggesting the existence of two subclasses of physiologically distinct type 5 CBCs. Both groups of Na+-expressing bipolar cells were capable of generating a rapid tetrodotoxin-sensitive action potential as revealed by current injection. Multiple spike-like potentials were also observed in some of these cells. Results of this study provide valuable insights into the function of voltage-gated Na+ channels of retinal bipolar cells in retinal processing.
Understanding and predicting deep percolation under surface irrigation
Authors: Bethune M. G. , Selle B. , Wang Q. J.
Published: December 2008

A lysimeter experiment was conducted in southeastern Australia to quantify the deep percolation response under irrigated pasture to different soil types, water table depths, and ponding times during surface irrigation. Deep percolation was governed by the final infiltration rate of the subsoil, the ponding time, the water table depth, and the amount of water stored in the rootzone between saturation and field capacity. These key variables were used to characterize both steady‐ and nonsteady‐state percolation in a conceptual model of deep percolation. The conceptual model was found to provide an effective representation of deep percolation for both the lysimeter and field‐scale water balance data. Steady‐state percolation during irrigation was the dominant process contributing to deep percolation on most of the studied soils. Nonsteady‐state percolation (redistribution) was very important for the sandiest soil type. The conceptual model provided better prediction of deep percolation than both data‐based model (artificial neural network) and process‐based modeling approach (1‐D Richards' equation model).
Dependence of the land‐sea contrast in surface climate response on the nature of the forcing
Authors: Joshi Manoj , Gregory Jonathan
Published: December 2008

The land‐sea contrast in surface warming is a phenomenon of both transient and equilibrium climate change. Its magnitude, while model‐dependent, is invariant with forcing amplitude. Here we demonstrate that the land‐sea contrast is dependent on whether the climate forcing is mainly caused by changes to CO2 or other mechanisms such as solar or volcanic forcing: this is mainly because a CO2 change affects stomatal conductance in plants, and therefore changes the amount of evaporation from regions with vegetation present. In addition, solar or volcanic radiative forcing has a different latitudinal distribution to CO2 forcing: when this effect is removed by normalising the land temperature response by the average ocean temperature response at the same latitude, spatial differences between the CO2 forced run and the solar forced run become more apparent. Our results affect prediction of the land/sea contrast, as well as the interpretation of proxy climate data.
Origin of the Medusae Fossae Formation, Mars: Insights from a synoptic approach
Authors: Mandt Kathleen E. , de Silva Shanaka L. , Zimbelman James R. , Crown David A.
Published: December 2008

The geologic origin of the Medusae Fossae Formation (MFF) has remained a mystery despite three decades of research. To better constrain its formation, an in‐depth analysis of observations made in the literature was combined with a new survey of over 700 Mars Orbiter Camera narrow‐angle images of the MFF to identify morphologic characteristics and material properties that define this formation as a whole. While previous work has identified clear agreement on some characteristics, our analysis identifies yardangs, collapse features, and layering as pervasive features of the MFF. Whereas collapse features and layering may implicate several different physical and chemical processes, yardangs provide vital information on material properties that inform about mechanical properties of the MFF lithology. Aspect ratios of megayardangs range from 3:1 to 50:1, and slope analyses reveal heights of up to 200 m with cliffs that are almost vertical. Other yardangs show lower aspect ratios and topographic profiles. These characteristics coupled to the presence of serrated margins, suggest that MFF lithology must be of weakly to heavily indurated material that lends itself to jointing. The characteristics and properties of the MFF are inconsistent with those of terrestrial pyroclastic fall deposits or loess, but are in common with large terrestrial ignimbrites, a hypothesis that explains all key observations with a single mechanism. Yardang fields developed in regionally extensive ignimbrite sheets in the central Andes display morphologic characteristics that correlate with degree of induration of the host lithology and suggest an origin by pyroclastic flow for the MFF.
Versatile direct push profiler for the investigation of volatile compounds near the water table
Authors: Amos Richard T. , Blowes David W.
Published: December 2008

The collection of representative samples of dissolved volatile compounds requires particular care to ensure that degassing does not occur during sampling, particularly for sites where the water table is deep. Furthermore, the investigation of physical and chemical processes involving volatile components can be enhanced by collecting vadose zone gas samples above the water table and collecting water samples very close to the water table. Here we describe the design and operation of a direct push profiler that allows the collection of gas and water samples from one hole. The profiler is capable of collecting water samples close to the water table and preserves the integrity of the samples collected from below deep water tables with respect to volatile compounds. The versatility of the profiler is due to the incorporation of a small‐diameter bladder pump into the tip of a Waterloo profiler. Laboratory testing shows that samples collected from 10 cm below the water table and at 9 m depth below ground surface show no signs of degassing. Field measurements made at a petroleum spill site near Bemidji, Minnesota, provide a comparison of profiler results to samples collected from an existing well cluster, demonstrating the ability of the profiler to obtain representative samples under field conditions. Furthermore, the field tests demonstrate the utility of the direct push profiler in terms of obtaining high‐resolution, high‐quality data through the vadose zone and into the upper few meters of the aquifer.
Assessing marginal water values in multipurpose multireservoir systems via stochastic programming
Authors: Tilmant A. , Pinte D. , Goor Q.
Published: December 2008

The International Conference on Water and the Environment held in Dublin in 1992 emphasized the need to consider water as an economic good. Since water markets are usually absent or ineffective, the value of water cannot be directly derived from market activities but must rather be assessed through shadow prices. Economists have developed various valuation techniques to determine the economic value of water, especially to handle allocation issues involving environmental water uses. Most of the nonmarket valuation studies reported in the literature focus on long‐run policy problems, such as permanent (re)allocations of water, and assume that the water availability is given. When dealing with short‐run allocation problems, water managers are facing complex spatial and temporal trade‐offs and must therefore be able to track site and time changes in water values across different hydrologic conditions, especially in arid and semiarid areas where the availability of water is a limiting and stochastic factor. This paper presents a stochastic programming approach for assessing the statistical distribution of marginal water values in multipurpose multireservoir systems where hydropower generation and irrigation crop production are the main economic activities depending on water. In the absence of a water market, the Lagrange multipliers correspond to shadow prices, and the marginal water values are the Lagrange multipliers associated with the mass balance equations of the reservoirs. The methodology is illustrated with a cascade of hydroelectric‐irrigation reservoirs in the Euphrates river basin in Turkey and Syria.
A model for soil‐vegetation‐atmosphere interactions in water‐limited ecosystems
Authors: Baudena M. , D'Andrea F. , Provenzale A.
Published: December 2008

We study the interaction between atmosphere, soil moisture, and vegetation in water‐limited environments with significant water recycling, and introduce a simple process model including some of the main feedbacks active in the system. In our model, the soil‐vegetation‐atmosphere dynamics display two stable states for realistic values of the synoptic moisture convergence flux. Starting from low soil moisture and/or low vegetation cover, the system reaches a dry and hot state, whereas it reaches a wet and cool state when starting from higher initial values of soil moisture and of vegetation cover. The role of synoptic perturbations is investigated by inserting a stochastic input of moisture: in this case, a bimodal distribution of soil moisture is obtained. We explore the difference between the dynamics of natural vegetation, capable of adjusting its areal extent to variations in soil moisture, and cultivated vegetation, whose areal extent cannot vary. The model results indicate that the presence of natural vegetation increases the probability of reaching a wet/cool state with respect to the case of cultivated plants.
miR‐142‐3p restricts cAMP production in CD4+CD25− T cells and CD4+CD25+ TREG cells by targeting AC9 mRNA
Authors: Huang Bo , Zhao Jie , Lei Zhang , Shen Shiqian , Li Dong , Shen Guan‐Xin , Zhang Gui‐Mei , Feng Zuo‐Hua
Published: December 2008

Cyclic AMP (cAMP) is a ubiquitous second messenger that regulates diverse cellular functions. It has been found that CD4+CD25+ regulatory T (TREG) cells exert their suppressor function by transferring cAMP to responder T cells. Here, we show that miR‐142‐3p regulates the production of cAMP by targeting adenylyl cyclase (AC) 9 messenger RNA in CD4+CD25− T cells and CD4+CD25+ TREG cells. miR‐142‐3p limits the level of cAMP in CD4+CD25− T cells by inhibiting AC9 production, whereas forkhead box P3 (FOXP3) downregulates miR‐142‐3p to keep the AC9/cAMP pathway active in CD4+CD25+ TREG cells. These findings reveal a new molecular mechanism through which CD4+CD25+ TREG cells contain a high level of cAMP for their suppressor function, and also suggest that the microRNA controlling AC expression might restrict the final level of cAMP in various types of cells.
RYBP stabilizes p53 by modulating MDM2
Authors: Chen Deng , Zhang Jianbing , Li Mao , Rayburn Elizabeth R , Wang Hui , Zhang Ruiwen
Published: December 2008

The mouse double minute 2 (MDM2)–p53 interaction regulates the activity of p53 and is a potential target for human cancer therapy. Here, we report that RYBP (RING1‐ and YY1‐binding protein), a member of the polycomb group (PcG), interacts with MDM2 and decreases MDM2‐mediated p53 ubiquitination, leading to stabilization of p53 and an increase in p53 activity. RYBP induces cell‐cycle arrest and is involved in the p53 response to DNA damage. Expression of RYBP is decreased in human cancer tissues compared with adjacent normal tissues. These results show that RYBP is a new regulator of the MDM2–p53 loop and that it has tumour suppressor activity.
Correlation between Ground Level Ultra-Violet Radiation & Lower Atmospheric Aerosol Load
Authors: Yadav Shweta , Tandon Ankit
Published: December 2008

UV radiation is known to affect many biological and chemical processes, and is largely detrimental to individual organisms. Specific concerns include increase in the incidence of skin cancer, ocular damage, and other health effects in humans and other animals; damage to terrestrial and oceanic vegetation; changes in the chemistry of the lower atmosphere e.g. photochemical smog formation. Present study was undertaken to monitor lower atmospheric aerosol load with Respirable Dust Sampler and ultraviolet radiation with UV-radiometer in the ambient environment of Delhi. PM10 (< 10 µm) and SPM (> 10 µm) samples collected for the period of the study (8 weeks, 2 samples per week, total 16 samples). Hourly UV Fluxes (UV-B & UV-A) were measured from four hours ahead to four hours following the solar noon (LAT 12:00hrs), alongside aerosol sampling twice in a week. Our study shows, lower-atmospheric load of finer particles (PM10) significantly cut-off both UV-A and UV-B fluxes reaching the earth surface. PM10 load shows a satisfactory negative correlation with UV-A and UV-B fluxes at ground level.
A haemagglutinin from the medicinal fungus Cordyceps militaris
Authors: Wong Jack H. , Wang Hexiang , Ng Tzi B.
Published: December 2008

There are only a few reports on agglutinins from ascomycete and medicinal fungi. An HA (haemagglutinin), with an N-terminal amino acid sequence different from those of known lectins, was isolated in the present study from dried fruiting bodies of the medicinal ascomycete fungus Cordyceps militaris. The purification protocol consisted of affinity chromatography, ion-exchange chromatography and gel filtration. The haemagglutinating activity of the HA could not be inhibited by simple sugars or heparin, and was stable over the pH range 2–13 and up to 60°C. Chemical modification of tryptophan and tyrosine residues had no effect. The HA exhibited some antiproliferative activity towards hepatoma (HepG2) cells and inhibited HIV-1 reverse transcriptase (IC50=10 μM). However, it did not exhibit antifungal activity, mitogenic activity towards splenocytes, nitric oxide-inducing activity towards macrophages or RNase activity. The results of the present study add to the meagre information pertaining to agglutinins from ascomycete and medicinal mushrooms. It is revealed in this study that C. militaris HA differs from other ascomycete mushroom HAs in a variety of biochemical characteristics.
Calcium entry and the control of calcium oscillations
Authors: Shuttleworth T.J. , Mignen O.
Published: December 2008

During oscillatory Ca2+ signals, the agonist-induced enhanced entry of extracellular Ca2+ plays a critical role in modulating the frequency of the oscillations. Although it was originally assumed that the entry of Ca2+ under these conditions occurred via the well-known, and apparently ubiquitous, store-operated mechanism, subsequent studies suggested that this was unlikely. It is now known that, in many cell types, a novel non-capacitative Ca2+-selective pathway whose activation is dependent on arachidonic acid is responsible, and the channels involved [ARC channels (arachidonate-regulated Ca2+ channels)] have been characterized. These ARC channels co-exist with the store-operated CRAC channels (Ca2+-release-activated Ca2+ channel) in cells, but each plays a unique and non-overlapping role in Ca2+ signalling. In particular, it is the ARC channels that are specifically activated at the low agonist concentrations that give rise to oscillatory Ca2+ signals and provide the predominant mode of Ca2+ entry under these conditions. The indications are that Ca2+ entry through the ARC channels increases the likelihood that low concentrations of Ins(1,4,5)P3 will trigger repetitive Ca2+ release. At higher agonist concentrations, store-depletion is more complete and sustained resulting in the activation of CRAC channels. At the same time the ARC channels are turned off, resulting in what we have described as a reciprocal regulation of these two distinct Ca2+ entry pathways.
Sarcolemma agonist-induced interactions between InsP3 and ryanodine receptors in Ca2+ oscillations and waves in smooth muscle
Authors: McCarron J.G. , Bradley K.N. , MacMillan D. , Muir T.C.
Published: December 2008

Smooth muscle cells respond to InsP3-generating (sarcolemma-acting) neurotransmitters and hormones by releasing Ca2+ from the internal store. However, the release of Ca2+ does not occur uniformly throughout the cytoplasm but often into a localized area before being transmitted to other regions of the cell in the form of Ca2+ waves and oscillations to actively spread information within and between cells. Yet, despite their significance, our understanding of the generation of oscillations to waves is incomplete. A major aspect of controversy centres on whether or not Ca2+ released from the InsP3 receptor activates RyRs (ryanodine receptors) to generate further release by Ca2+-induced Ca2+ release and propagate waves or whether the entire process arises from InsP3 receptor activity alone. Under normal physiological conditions the [Ca2+] required to activate RyR (approx. 15 μM) exceeds the bulk average [Ca2+]c (cytoplasmic Ca2+ concentration) generated by InsP3 receptor activity (<1 μM). Progression of waves and oscillations by RyR activity would require a loss of control of RyR activity and an unrestrained positive feedback on Ca2+ release. Under store-overload conditions, RyR Ca2+ sensitivity is increased and this enables waves to be induced by RyR activity. However, the relevance of these Ca2+-release events to normal physiological functioning is unclear. The InsP3 receptor, on the other hand, is activated by Ca2+ over the physiological range (up to 300 nM) and deactivated by higher [Ca2+]c (>300 nM), features that favour intermittent activity of the receptor as occurs in waves and oscillations. Experimental evidence for the involvement of RyR relies mainly on pharmacological approaches in the intact cell where poor drug specificity could have led to ambiguous results. In this brief review the possible interactions between InsP3 receptors and RyR in the generation of oscillations and waves will be discussed. Evidence is presented that RyRs are not required for InsP3-mediated Ca2+ transients. Notwithstanding, ryanodine can inhibit InsP3-mediated Ca2+ responses after RyR activity has been induced by caffeine or by steady depolarization which evokes spontaneous transient outward currents (a sarcolemmal manifestation of RyR activity). Ryanodine inhibits InsP3-mediated Ca2+ transients by depleting the store of Ca2+ rather than by RyR involvement in the InsP3-mediated Ca2+ increase.
Calcium oscillations in T-cells: mechanisms and consequences for gene expression
Authors: Lewis R.S.
Published: December 2008

[Ca2+]i (intracellular Ca2+ concentration) oscillations play a central role in the activation of T-lymphocytes by antigen. Oscillations in T-cells are absolutely dependent on Ca2+ influx through store-operated CRAC channels (Ca2+-release-activated Ca2+ channels), and evidence suggests that they arise from delayed interactions between these channels and Ca2+ stores. Their potential functions have been explored by creating controlled [Ca2+]i oscillations with pulses of Ca2+ entry or pulses of Ins(1,4,5)P3. Oscillations enhance both the efficiency and specificity of signalling through the Ca2+-dependent transcription factors nuclear factor of activated T-cells (NFAT), Oct/Oap and nuclear factor κB (NFκB) in ways that are consistent with each factor's Ca2+ dependence and kinetics of activation and deactivation. These studies show how [Ca2+]i oscillations may enhance signalling to the nucleus, and suggest a possible cellular mechanism for extracting information encoded in oscillation frequency.
Ca2+-induced Ca2+ release in cardiac and smooth muscle cells
Authors: Kamishima T. , Quayle J.M.
Published: December 2008

Ca2+ influx across plasma membranes may trigger Ca2+ release by activating ryanodine-sensitive receptors in the sarcoplasmic reticulum. This process is called Ca2+-induced Ca2+ release, and may be important in regulating cytosolic Ca2+ concentration ([Ca2+]i). In cardiac cells, the initial [Ca2+]i increase, caused by L-type Ca2+ current, is profoundly amplified with Ca2+ release. The synchronized opening of several ryanodine-sensitive Ca2+-releasing channels was detected as discreet and highly localized Ca2+ elevation, and termed as a ‘Ca2+ spark’. A Ca2+ spark is under local control of an L-type Ca2+ channel, and therefore a Ca2+ spark does not normally trigger subsequent Ca2+ sparks in the neighbouring area. In smooth muscle cells, the importance of Ca2+-induced Ca2+ release in elevating [Ca2+]i appears to differ among preparations and species. Significant elevation in [Ca2+]i during depolarization was attributed to Ca2+ release in some smooth muscle cells, but not in others. Ca2+ sparks are also identified in smooth muscle cells, and may play a role as functional elementary events for Ca2+-induced Ca2+ release. At rest, Ca2+ sparks may be also important in regulating smooth muscle membrane potential. Ca2+ sparks occurring at rest do not raise global [Ca2+]i, but trigger spontaneous transient outward currents (STOCs) or spontaneous transient inward currents (STICs), the former producing hyperpolarization; the latter, depolarization. Thus there may be multiple facets for Ca2+-induced Ca2+ release in regulating the contractile status of smooth muscle cells.
Modulation of Ca2+ oscillations by phosphorylation of Ins(1,4,5)P3 receptors
Authors: Yule D.I. , Straub S.V. , Bruce J.I.E.
Published: December 2008

Activation of InsP3Rs (InsP3 receptors) represents the major mechanism underlying intracellular calcium release in non-excitable cells such as hepatocytes and exocrine cells from the pancreas and salivary glands. Modulation of calcium release through InsP3Rs is therefore a major route whereby the temporal and spatial characteristics of calcium waves and oscillations can potentially be ‘shaped’. In this study, the functional consequences of phosphoregulation of InsP3Rs were investigated. Pancreatic and parotid acinar cells express all three types of InsP3R in differing abundance, and all are potential substrates for phosphoregulation. PKA (protein kinase A)-mediated phosphorylation of InsP3Rs in pancreatic acinar cells resulted in slowed kinetics of calcium release following photo-release of InsP3. In contrast, activation of PKA in parotid cells resulted in a marked potentiation of calcium release. In pancreatic acinar cells the predominant InsP3R isoform phosphorylated was the type 3 receptor, while the type 2 receptor was markedly phosphorylated in parotid acinar cells. In order to further decipher the effects of phosphorylation on individual InsP3R subtypes, DT-40 cell lines expressing homotetramers of a single isoform of InsP3R were utilized. These data demonstrate that phosphoregulation of InsP3Rs results in subtype-specific effects and may play a role in the specificity of calcium signals by ‘shaping’ the spatio-temporal profile of the response.
Role of myristoylation in the intracellular targeting of neuronal calcium sensor (NCS) proteins
Authors: O'Callaghan D.W. , Burgoyne R.D.
Published: December 2008

The control of the intracellular localization of NCS (neuronal calcium sensor) proteins is of importance for their ability to respond appropriately to differing calcium signals. We examine the localization of three NCS proteins: NCS-1, KChIP-1 (potassium-channel-interacting protein 1) and hippocalcin. Additionally, the [Ca2+] dependency of the calcium-induced translocation of hippocalcin is investigated. The implications of the differential targeting of these proteins on calcium signal interpretation are considered.
Imaging molecular interactions in cells by dynamic and static fluorescence anisotropy (rFLIM and emFRET)
Authors: Lidke D.S. , Nagy P. , Barisas B.G. , Heintzmann R. , Post J.N. , Lidke K.A. , Clayton A.H.A. , Arndt-Jovin D.J. , Jovin T.M.
Published: December 2008

We report the implementation and exploitation of fluorescence polarization measurements, in the form of anisotropy fluorescence lifetime imaging microscopy (rFLIM) and energy migration Förster resonance energy transfer (emFRET) modalities, for wide-field, confocal laser-scanning microscopy and flow cytometry of cells. These methods permit the assessment of rotational motion, association and proximity of cellular proteins in vivo. They are particularly applicable to probes generated by fusions of visible fluorescence proteins, as exemplified by studies of the erbB receptor tyrosine kinases involved in growth-factor-mediated signal transduction.
Oxidative modification of triacylglycerol-rich lipoproteins
Authors: Young I.S. , McFarlane C. , McEneny J.
Published: December 2008

Lipoprotein oxidation is thought to play a pivotal role in the evolution of atherosclerosis. Low-density lipoprotein (LDL) is the main source of oxidized lipid in the arterial wall. Oxidation of LDL alters its properties in a number of ways, making it more atherogenic, but oxidation of other lipoprotein classes may also be important. Common mechanisms are likely to contribute to the oxidation of all lipoprotein classes, with enzyme-mediated oxidation likely to be most important. Antioxidant content, fatty acid composition, particle size and the presence of seeding hydroperoxides also influence oxidative reactions. Larger triglyceride-rich lipoproteins are less likely to enter the arterial wall than LDL, but when oxidized will deliver a greater oxidant load to the arterial wall.
Regression of pre-established atherosclerosis in the apoE−/− mouse by conjugated linoleic acid
Authors: Toomey S. , Roche H. , Fitzgerald D. , Belton O.
Published: December 2008

Conjugated linoleic acid (CLA) refers to a group of positional and geometric isomers of linoleic acid that has been shown to suppress the development of atherosclerosis in a rabbit model. We investigated whether CLA acts as a cyclo-oxygenase (COX) inhibitor or as an agonist of the peroxisome-proliferator-activator receptor (PPAR) γ in the ApoE−/− mouse model. In vitro, a 9-cis, 11-trans isomer of CLA inhibited prostaglandin formation and oxygen consumption by both isoforms of COX, with no evidence by MS of alternative products being generated. In vivo, supplementation with CLA was found to induce resolution of atherosclerosis. The effect of CLA in vivo could not be explained by COX inhibition alone, as urinary prostaglandin levels were unchanged in animals receiving CLA supplementation, and administration of selective COX inhibitors did not induce lesion regression. There was however induction of PPARγ, a known response to agonists of this nuclear orphan receptor.
Intramyocellular lipid levels are associated with peripheral, but not hepatic, insulin sensitivity in normal healthy subjects
Authors: Salgin Burak , Sleigh Alison J. , Williams Rachel M. , Jackson Sarah J. , Bluck Les J. , Murgatroyd Peter R. , Humphreys Sandy M. , Harding Sally , Carpenter T. Adrian , Dunger David B.
Published: December 2008

Increased levels of IMCL (intramyocellular lipid) have been shown to be associated with reduced steady-state glucose infusion rates during a hyperinsulinaemic–euglycaemic clamp (M-value). The aim of the present study was to explore how IMCL levels relate to the insulin-mediated suppression of endogenous glucose production [hepatic SI (insulin sensitivity)] and increase in glucose disposal (peripheral SI). In the present study, 11 healthy young adults (7 male, 4 female; aged 21–31 years) undertook, in random order, an hyperinsulinaemic–euglycaemic clamp combined with stable glucose isotope enrichment to measure peripheral and hepatic SI, a 1H-MRS (proton-magnetic resonance spectroscopy) scan to determine IMCL levels and a DXA (dual-energy X-ray absorptiometry) scan to assess body composition. IMCL levels (range, 3.2–10.7) were associated with whole-body fat mass (r=0.787, P=0.004), fat mass corrected for height (r=0.822, P=0.002) and percentage of central fat mass (r=0.694, P=0.02), but were not related to whole-body FFM (fat-free mass; r=−0.472, P=0.1). IMCL levels correlated closely with the M-value (r=−0.727, P=0.01) and FFM-corrected peripheral SI (r=−0.675, P=0.02), but were not related to hepatic SI adjusted for body weight (r=0.08, P=0.8). The results of the present study suggest that IMCL accumulation may be a sensitive marker for attenuations in peripheral, but not hepatic, SI in normal populations. Given the close relationship of IMCL levels to whole-body and central abdominal fat mass, relative increases in the flux of lipids from adipose tissue to the intramyocellular compartment may be an integral part of the mechanisms underlying reductions in SI.
Ultrafast laser direct-write actuable microstructures
Authors: Tapalian H, Charles , Langseth Jason , Chen Ying , Anderegg James W. , Shinar Joseph
Published: December 2008

Actuable microelectromechanical systems (MEMS), fabricated by direct “writing” of deformable membranes on indium tin oxide/copper phthalocyanine (CuPc)/Al microstructures using 130 fs laser pulses, are described. The pulses locally ablate the CuPc without requiring micromachined release holes, demonstrating a novel material release mechanism. The direct-write procedure therefore requires fewer processing steps than traditional MEMS approaches. Using it, we fabricated optical modulators with phase modulation depths >π, intensity modulation amplitudes >50%, and bandwidths >100 kHz, at 5–10 V drive voltage. Fabrication of numerous microstructures and nanostructures can be envisioned, including photonic crystals and optical phased-array gratings.
Coupling, concentration inequalities, and stochastic dynamics
Authors: Chazottes Jean-René , Collet Pierre , Redig Frank
Published: December 2008

In the context of interacting particle systems, we study the influence of the action of the semigroup on the concentration property of Lipschitz functions. As an application, this gives a new approach to estimate the relaxation speed to equilibrium of interacting particle systems. We illustrate our approach in a variety of examples for which we obtain several new results with short and nontechnical proofs. These examples include the symmetric and asymmetric exclusion processes and high-temperature spin-flip dynamics (“Glauber dynamics”). We also give a new proof of the Poincaré inequality, based on coupling, in the context of one-dimensional Gibbs measures. In particular, we cover the case of polynomially decaying potentials, where the log-Sobolev inequality does not hold.
High resolution NMR study of T1 magnetic relaxation dispersion. I. Theoretical considerations of relaxation of scalar coupled spins at arbitrary magnetic field
Authors: Ivanov Konstantin , Yurkovskaya Alexandra , Vieth Hans-Martin
Published: December 2008

A theoretical approach to the description of longitudinal (T1) relaxation in scalar coupled systems of spin 1/2 nuclei at arbitrary magnetic field is developed, which is based on the Redfield theory. The consideration is addressed to field-cycling relaxometry experiments with high-resolution NMR detection, in which the field dependence of T1-relaxation times, the nuclear magnetic relaxation dispersion (NMRD), can be studied for individual spins of the molecule. Our study reveals well-pronounced effects of spin-spin couplings on the NMRD curves. First, coupled spins having completely different high-field T1 times tend to relax at low field with a common relaxation time. Second, the NMRD curves exhibit sharp features at the fields corresponding to the positions of nuclear spin level anticrossings. Such effects of spin-spin couplings show up not only for individual spins but also for the T1-relaxation of the total spin magnetization of the molecule. The influence of spin-spin coupling is of importance as long as the coupling strength J is larger than the inverse T1-relaxation times of the spins. Around J⋅T1=1 there is also a coherent contribution to the relaxation kinetics resulting in an oscillatory component of the kinetic curves. Application of the theory to experimental examples will be described in subsequent publications.
Hydrophilic low-temperature direct wafer bonding
Authors: Ventosa C. , Rieutord F. , Libralesso L. , Morales C. , Fournel F. , Moriceau H.
Published: December 2008

The sealing mechanism of silicon bonding interfaces is reported as a function of annealing temperature. Details of the structural and chemical interface evolution are obtained for hydrophilic silicon/silicon and silicon/silicon dioxide wafer bonding, using x-ray reflectivity and infrared spectroscopy. A two-step mechanism is demonstrated: first a partial sealing of the interface driven by cross-wafer silanol bond condensation and second a water evacuation via oxide formation at the silicon oxide interface.
X-ray photoelectron spectroscopy and x-ray excited Auger spectroscopy studies of manganese thiophosphate intercalated with sodium ions
Authors: Silipigni L. , Quattrone T. , Schirò L. , Grasso V. , Scolaro L. Monsù , De Luca G. , Salvato G.
Published: December 2008

Polycrystalline powders of Na2xMn1−xPS3 have been synthesized from layered MnPS3 material by successive ion-exchange intercalation of potassium and sodium ions. Their x-ray photoelectron spectroscopy (XPS) and x-ray excited Auger spectroscopy spectra have been measured at room temperature using Mg Kα (1253.6 eV) x-ray source. In particular, the Mn, P, and S 2p and Na 1s and 2p core-level regions and the Na Auger KL23L23 transition have been investigated. All the analyzed XPS core-level spectra display a single-peak structure, suggesting the absence of nonequivalent atoms of Na, Mn, P, and S. The manganese XPS spectrum shows, as observed in MnPS3 and in its cesium and potassium intercalation compounds, typical shake-up satellites, suggesting that the Mn–S bond is yet mainly ionic in nature. The comparison with the XPS spectra relative to MnPS3 and its potassium intercalation compound (K2xMn1−xPS3) does not emphasize any relevant difference in the binding energy positions of the investigated core levels, indicating that sodium ion intercalation process does not alter the electronic properties of pure host matrix. Moreover, Na 2p core levels are discrete and well localized in agreement with the hypothesis of a weak link between the guest (the Na+ ions) and the host lattice (the negatively charged Mn1−xPS3 sheets). Such a hypothesis finds confirmation by the calculation of the Na modified Auger parameter.
Two- and three-photon absorption of semiconductor quantum dots in the vicinity of half of lowest exciton energy
Authors: Xing Guichuan , Ji Wei , Zheng Yuangang , Ying Jackie Y.
Published: December 2008

We present a demonstration of the unambiguous determination of two-photon absorption (2PA) and three-photon absorption (3PA) in semiconductor quantum dots in the vicinity of E0/2, where E0 denotes the peak position of the lowest exciton energy. In the spectral region where photon energies ℏω≥E0/2, the 2PA cross section is determined by open-aperture Z scans with femtosecond laser pulses at relatively lower irradiances, and then the 3PA cross section is extracted from the Z scans measured at higher irradiances. As photon energies are less than but near E0/2, multiphoton-excited photoluminescence techniques have to be employed in conjunction with open-aperture Z scan to distinguish between 2PA and 3PA.
Determining the terahertz optical properties of subwavelength films using semiconductor surface plasmons
Authors: Isaac T. H. , Barnes W. L. , Hendry E.
Published: December 2008

By employing a combination of time-domain measurements and numerical calculations, we demonstrate that the semiconductor InSb supports a strongly confined surface plasmon (SP) in the terahertz frequency range. We show that these SPs can be used to enhance the light-matter interaction with dielectric layers above the semiconductor surface, thereby allowing us to detect the presence of polystyrene layers around 1000 times thinner than the free space wavelength of the terahertz light. Finally we discuss the viability of using semiconductor SPs for the purposes of terahertz sensing and spectroscopy.
Morphology and conductivity modification of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) films induced by conductive atomic force microscopy measurements
Authors: Dang Xuan-Dung , Dante Mark , Nguyen Thuc-Quyen
Published: December 2008

Morphology and conductivity modifications in poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films induced by conductive atomic force microscopy probe are investigated. At an applied bias of positive or negative 10 V, raised features of 12.8±1.8 nm in height are generated and the local film conductivity is reduced. The feature height formation is irreversible and dependent on both applied bias and tip velocity. The mechanism by which these features are generated is proposed to be mass transport of PSS− to the surface under the atomic force microscope tip. This finding may open up the possibility of patterning PEDOT:PSS films, and thereby organic optoelectronic devices.
Effect of oxygen incorporation on normal and superconducting properties of MgB2 films
Authors: Singh R. K. , Shen Y. , Gandikota R. , Carvalho C. , Rowell J. M. , Newman N.
Published: December 2008

Oxygen was systematically incorporated in MgB2 films using in situ postgrowth anneals in an oxygen environment. Connectivity analysis in combination with measurements of the critical temperature (Tc) and resistivity (ρ) indicate that oxygen is distributed both within and between the grains. High values of critical current densities (Jc) in field (∼4×105A∕cm2 at 8T and 4.2K), extrapolated critical fields [Hc2(0)] (>45T), and slopes of critical field versus temperature (1.4T∕K) are observed. Our results suggest that low growth temperatures (300°C) and oxygen doping (⩾0.65%) can produce MgB2 with high Jc values in field and Hc2 for high-field magnet applications.
Enhanced oxygen precipitation in neutron-irradiated nitrogen-doped Czochralski silicon crystal
Authors: Cui Can , Ma Xiangyang , Yang Deren
Published: December 2008

Nitrogen and vacancies were intentionally introduced into Czochralski silicon crystal by doping and neutron irradiation, respectively, to study the effect on oxygen precipitation. A series of isochronal anneals in the temperature range of 700–1150 °C revealed that vacancies showed the prominent enhancement effect on oxygen precipitation at temperatures below 1000 °C, whereas nitrogen exhibited the evident enhancement in oxygen precipitation at temperatures above 900 °C. It is suggested that the vacancies induced by neutron irradiation form VnOm (n, m≥1) complexes acting as nuclei to facilitate oxygen precipitation in silicon. However, the VnOm complexes are not stable at higher temperatures; thus, the enhancement effect of vacancies on oxygen precipitation decreases evidently as the temperature increases above 1000 °C. In addition to the formation of new nuclei based on the VnOm complexes, the growth of grown-in oxygen precipitates is also facilitated by the incorporation of high concentration vacancies in the neutron-irradiated silicon. In nitrogen-doped silicon, the enhanced oxygen precipitation at high temperatures primarily depends on nitrogen concentration rather than vacancy concentration as a result of forming stable N2V2 complexes acting as precipitate nuclei.
Properties of O2(Δ1)–I(P21/2) laser medium with a dc glow discharge iodine atom generator
Authors: Mikheyev Pavel A. , Azyazov Valeriy N.
Published: December 2008

Experiments were carried out in a flow cell apparatus under conditions corresponding to those of a typical oxygen-iodine laser. The cell was equipped with a chemical jet type singlet oxygen generator and an electric discharge for the production of iodine atoms. The properties of the discharge generator and the active medium were studied using laser-induced fluorescence and emission spectroscopy. I2 or CH3I entrained in a carrier flow of Ar were used as atomic iodine precursors. About 50% of the iodine contained in CH3I molecules was extracted in the generator. 2.6% of the electric power loaded into the discharge was used in CH3I dissociation. Right after the discharge 80%–90% of the iodine flow consisted of atoms. However, due to recombination during transport, only 20%–50% of atoms remained at the point of injection into the oxygen flow. A straightforward comparison of two methods of oxygen-iodine medium production—conventional, by means of I2 dissociation in the singlet oxygen flow and with iodine atoms produced externally in the electric discharge—was performed. It was found that the lifetime for the energy stored in singlet oxygen was about 30% longer, when atomic iodine was produced from CH3I in the discharge, as compared to the conventional chemical dissociation of I2 in the singlet oxygen flow.
Shape-controlled synthesis and cathodoluminescence properties of elongated α-Fe2O3 nanostructures
Authors: Chioncel M. F. , Díaz-Guerra C. , Piqueras J.
Published: December 2008

α -Fe 2 O 3 (hematite) nanostructures with various morphologies have been grown by thermal oxidation of compacted iron powder at temperatures between 700 and 900 °C. Different thermal treatments have been found to induce the growth of single-crystalline nanowires, nanobelts, nanoplates and featherlike structures, free and caped nanopillars, and pyramidal microcrystals or cactuslike microstructures. The experimental conditions leading to the different morphologies have been systematically investigated, as well as the possible growth mechanisms. The obtained nanostructures have been characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy, x-ray diffraction, and cathodoluminescence (CL) spectroscopy in the SEM. The formation of the nanostructures induces changes in the intensity and spectral distribution of the CL emission, as compared with the bulk material. Ligand to metal charge transfer transitions as well as Fe3+ ligand field transitions are thought to be involved in the observed luminescence. The evolution of the panchromatic CL intensity in the visible range as a function of temperature shows some anomalies that may be induced by magnetic ordering effects.
Neurogenesis and widespread forebrain migration of distinct GABAergic neurons from the postnatal subventricular zone
Authors: Inta Dragos , Alfonso Julieta , von Engelhardt Jakob , Kreuzberg Maria M. , Meyer Axel H. , van Hooft Johannes A. , Monyer Hannah
Published: December 2008

Most forebrain GABAergic interneurons in rodents are born during embryonic development in the ganglionic eminences (GE) and migrate tangentially into the cortical plate. A subset, however, continues to be generated postnatally in the subventricular zone (SVZ). These interneurons populate the olfactory bulb (OB) reached via migration in the rostral migratory stream (RMS). Employing transgenic mice expressing EGFP in 5-HT
3
-positive neurons, we identified additional migratory pathways in the early postnatal brain. Time-lapse imaging experiments revealed massive migration of EGFP-positive cells from the SVZ into numerous forebrain regions, including cortex, striatum, and nucleus accumbens. The neuronal fate of the migratory EGFP-labeled cells was indicated by their doublecortin (DCX) expression. Birthdating experiments, by using 5-bromo-2′-deoxyuridine (BrdU) and retrovirus-based experiments, provided evidence that migrating neuroblasts were born in the SVZ postnatally and developed a distinct GABAergic phenotype. Our results demonstrate that the SVZ is a reservoir of GABAergic interneurons not only for the OB, but also for other cortical and subcortical areas.
Identification of gene 3′ ends by automated EST cluster analysis
Authors: Muro Enrique M. , Herrington Robert , Janmohamed Salima , Frelin Catherine , Andrade-Navarro Miguel A. , Iscove Norman N.
Published: December 2008

The properties and biology of mRNA transcripts can be affected profoundly by the choice of alternative polyadenylation sites, making definition of the 3′ ends of transcripts essential for understanding their regulation. Here we show that 22–52% of sequences in commonly used human and murine “full-length” transcript databases may not currently end at bona fide polyadenylation sites. To identify probable transcript termini over the entire murine and human genomes, we analyzed the EST databases for positional clustering of EST ends. The analysis yielded 58,282 murine- and 86,410 human-candidate polyadenylation sites, of which 75% mapped to 23,091 known murine transcripts and 22,891 known human transcripts. The murine dataset correctly predicted 97% of the 3′ ends in a manually curated and experimentally supported benchmark transcript set. Of currently known genes, 15% had no associated prediction and 25% had only a single predicted termination site. The remaining genes had an average of 3–4 alternative polyadenylation sites predicted for each murine or human transcript, respectively. The results are made available in the form of tables and an interactive web site that can be mined for rapid assessment of the validity of 3′ ends in existing collections, enumeration of potential alternative 3′ polyadenylation sites of known transcripts, direct retrieval of terminal sequences for design of probes, and detection of polyadenylation sites not currently mapped to known genes.
Selectin catch–slip kinetics encode shear threshold adhesive behavior of rolling leukocytes
Authors: Beste Michael T. , Hammer Daniel A.
Published: December 2008

The selectin family of leukocyte adhesion receptors is principally recognized for mediating transient rolling interactions during the inflammatory response. Recent studies using ultrasensitive force probes to characterize the force–lifetime relationship between P- and L-selectin and their endogenous ligands have underscored the ability of increasing levels of force to initially extend the lifetime of these complexes before disrupting bond integrity. This so-called “catch–slip” transition has provided an appealing explanation for shear threshold phenomena in which increasing levels of shear stress stabilize leukocyte rolling under flow. We recently incorporated catch–slip kinetics into a mechanical model for cell adhesion and corroborated this hypothesis for neutrophils adhering via L-selectin. Here, using adhesive dynamics simulations, we demonstrate that biomembrane force probe measurements of various P- and L-selectin catch bonds faithfully predict differences in cell adhesion patterns that have been described extensively in vitro. Using phenomenological parameters to characterize the dominant features of molecular force spectra, we construct a generalized phase map that reveals that robust shear-threshold behavior is possible only when an applied force very efficiently stabilizes the bound receptor complex. This criteria explains why only a subset of selectin catch bonds exhibit a shear threshold and leads to a quantitative relationship that may be used to predict the magnitude of the shear threshold for families of catch–slip bonds directly from their force spectra. Collectively, our results extend the conceptual framework of adhesive dynamics as a means to translate complex single-molecule biophysics to macroscopic cell behavior.