bluuebunny/crossref_metadata_2025 huggingface dataset:
Digital electrospray for controlled deposition
Authors: Deng Weiwei , Waits C. Mike , Gomez Alessandro
Published: March 2010

Many novel functional structures are now fabricated by controlled deposition as a maskless, bottom-up fabrication technique. These applications require rapid and precise deposition of minute amounts of solutions/suspensions or their ultimate particle products in predefined patterns. The electrospray is a promising alternative to the commonly used inkjet printing because it can easily handle highly viscous liquid, avoid high shear rates, and has low risk of clogging. We demonstrate a proof-of-concept digital electrospray. This system consists of a 61-nozzle array microfabricated in silicon and a 61-element digital extractor fabricated using flexible polyimide substrates. “Digital” refers to the state of each electrospray source that can be tuned either on or off independently and responsively. We showed a resolution of 675 μm and a response frequency up to 100 Hz. With similar design and industry standard fabrication procedures, it is feasible to scale up the system to O(1000) sources with spatial resolution better than 250 μm and a O(kHz) response frequency. The latter is controlled by the viscous damping time.
Photodissociation and photoisomerization dynamics of CH2CHCHO in solution
Authors: Wu Weiqiang , Yang Chunfan , Zhao Hongmei , Liu Kunhui , Su Hongmei
Published: March 2010

By means of time-resolved Fourier transform infrared absorption spectroscopy, we have investigated the 193 nm photodissociation and photoisomerization dynamics of the prototype molecule of α,β-enones, acrolein (CH2CHCHO) in CH3CN solution. The primary photolysis channels and absolute branching ratios are determined. The most probable reaction mechanisms are clarified by control experiments monitoring the product yields varied with the triplet quencher addition. The predominant channel is the 1,3-H migration yielding the rearrangement product CH3CHCO with a branching ratio of 0.78 and the less important channel is the α cleavage of CH bond yielding radical fragments CH2CHCO+H with a branching ratio of only 0.12. The 1,3-H migration is strongly suggested to correlate with the triplet (ππ∗)3 state rather than the ground S0 state and the α cleavage of CH bond is more likely to proceed in the singlet S1 (nπ∗)1 state. From the solution experiments we have not only acquired clues clarifying the previous controversial mechanisms, but also explored different photochemistry in solution. Compared to the gas phase photolysis which is dominated by photodissociation channels, the most important channel in solution is the photoisomerization of 1,3-H migration. The reason leading to the different photochemistry in solution is further ascribed to the solvent cage effect.
Anomalous exciton lifetime by electromagnetic coupling of self-assembled InAs/GaAs quantum dots
Authors: Bogaart E. W. , Haverkort J. E. M.
Published: March 2010

We report on the experimental observation of a hitherto ignored long-range electromagnetic coupling between self-assembled InAs/GaAs quantum dots (QDs). A 12 times enhancement of the QD exciton lifetime is observed by means of time-resolved differential reflection spectroscopy. The enhancement is due to local field effects within the QD ensemble. The electromagnetic coupling of the QDs results in a collective polarizability, and is observed as a suppression of the emission rate. Our results reveal that the mutual coupling strength can be optically tuned by varying the pump excitation density. This enables us to optically tune the exciton lifetime.
Quantum conductance in nanotube-ribbon hybrids
Authors: Li T. S. , Lin M. F. , Chang S. C.
Published: March 2010

The electronic and transport properties of nanotube-ribbon hybrids subject to the influences of a perpendicular magnetic field are investigated theoretically. The energy dispersion relations are found to exhibit significant dependence on the nanotube-ribbon interactions, the field strength, and the geometry of the hybrids. Variations in the electronic structures with field strength or nanotube location will be reflected in the electrical and thermal conductance. The chemical-potential-dependent electrical and thermal conductances exhibit a stepwise increase and spike behavior. These conductances can be tuned by varying the field strength or the nanotube location. The peak and shoulder structures of the conductance will be stretched as temperature rises. In addition, quantum conductance behavior in nanotube-ribbon hybrids can be observed experimentally at temperature below 10 K.
Stochastic model of lithium ion conduction in poly(ethylene oxide)
Authors: Gitelman L. , Averbuch A. , Nathan M. , Schuss Z. , Golodnitsky D.
Published: March 2010

We develop, analyze, and simulate a physical model of Li+-ion conduction inside polyethylene oxide (PEO) helical tubes, which are the solvent of LiI salt. The current is due to diffusion and electric interactions with a permanent external field, the PEO charges, and ion-ion interactions. Potential barriers are created in the PEO by loops in structure. We calculate the energy of configurations of one or two lithium ions in the loop and derive an explicit expression for the activation energy. We use Kramers’ formula to calculate the conductivity as function of mechanical stretching, which lowers the barrier and causes an exponential rise in the output conductivity.
Effective incorporation of nanoceria into polycrystalline MgB2
Authors: Gharaibeh M. , Albiss B. A. , Jumah I. , Obaidat I. M.
Published: March 2010

A series of polycrystalline MgB2 samples were prepared with different amounts of nanosized CeO2 inclusions. Samples were subjected to x-ray diffraction, scanning electron microscopy, and atomic force microscopy characterization. We found that nano-CeO2 inclusions affect the lattice parameters as well as the microstructure of MgB2 superconductor. An increase in the lattice parameters a and c was observed due to nanoinclusions up to 2 wt %. The morphology of the surface of pure samples reveals a considerable number of weak-links, randomly oriented grains and clean grain boundaries. While in samples with nanoinclusions, grain surfaces and boundaries were decorated with nanosized CeO2 particles and low traces of secondary phases. A reduction in the average grain size and roughness was also observed for samples with highest inclusions. The superconducting properties have been measured using the magnetization measurement M(H) in magnetic field up to 5 T. Significant enhancement of the superconducting critical current density Jc and the pinning force Fp in applied magnetic field was observed due to nano-CeO2 addition. However, no considerable change in the transition temperature Tc and transition width was observed. These results were interpreted in terms of the scaling of the flux pinning in granular superconducting networks which leads to a better basic understanding of the performance of MgB2 system in relatively high applied magnetic fields.
Stepwise hydration of the cyanide anion: A temperature-controlled photoelectron spectroscopy and ab initio computational study of CN−(H2O)n, n=2–5
Authors: Wang Xue-Bin , Kowalski Karol , Wang Lai-Sheng , Xantheas Sotiris S.
Published: March 2010

We report the study of microsolvated CN−(H2O)n (n=1–5) clusters in the gas phase using a combination of experimental and computational approaches. The hydrated cyanide clusters were produced by electrospray and their structural and energetic properties were probed using temperature-controlled photoelectron spectroscopy (PES) and ab initio electronic structure calculations. Comparison between the low temperature (LT,T=12 K) and the room-temperature (RT) spectra shows a 0.25 eV spectral blueshift in the binding energy of the n=1 cluster and a significant spectral sharpening and blueshift for n=2 and 3. The experimental results are complemented with ab initio electronic structure calculations at the MP2 and CCSD(T) levels of theory that identified several isomers on the ground state potential energy function arising from the ability of CN− to form hydrogen bonds with water via both the C and N ends. In all cases the N end seems to be the preferred hydration site for the water network. The excellent agreement between the low temperature measured PES spectra and the basis set- and correlation-corrected [at the CCSD(T) level of theory] calculated vertical detachment energies, viz., 3.85 versus 3.84 eV (n=0), 4.54 versus 4.54 eV (n=1), 5.20 versus 5.32 eV (n=2), 5.58 versus 5.50 eV (n=3), and 5.89 versus 5.87 eV (n=4), allow us to establish the hydration motif of cyanide. Its microsolvation pattern was found to be similar to that of the halide anions (Cl−, Br−, and I−) as well as other diatomic anions having cylindrical symmetry such as NO−, resulting to structures in which the ion resides on the surface of a water cluster. The exception is CN−(H2O)2, for which one water molecule is bound to either side of the anion resulting in a quasilinear structure. For the n=3 cluster the anion was found to freely “tumble” on the surface of a water trimer, since the inclusion of zero-point energy even at T=0 K stabilizes the configuration of C3 symmetry with respect to the one having the anion tilted toward the water cluster. For n=4 this motion is more restricted since the corresponding barrier at RT is 1.2 kcal/mol. It is also possible that at RT other isomers (lying within ∼0.6 kcal/mol above the global minima) are also populated, resulting in the further broadening of the PES spectra.
Solitary waves in two-dimensional dusty plasma crystal: Effects of weak magnetic field
Authors: Ghosh Samiran , Gupta M. R.
Published: March 2010

It is shown that in the presence of weak magnetic field, the dust lattice solitary wave in two-dimensional (2D) hexagonal dusty plasma crystal is governed by a gyration-modified 2D Korteweg-de Vries equation due to the action of Lorentz force on the dust particles. Numerical solutions reveal that only for weak magnetic field an apparently single hump solitary wave solution exist. But, for strong magnetic field dust lattice solitary wave becomes unstable showing repetitive solitary hump of increasing magnitude with time.
Note: Single-shot continuously time-resolved MeV ultrafast electron diffraction
Authors: Li Renkai , Huang Wenhui , Du Yingchao , Yan Lixin , Du Qiang , Shi Jiaru , Hua Jianfei , Chen Huaibi , Du Taibin , Xu Haisheng , Tang Chuanxiang
Published: March 2010

We have demonstrated single-shot continuously time-resolved MeV ultrafast electron diffraction using a static single crystal gold sample. An MeV high density electron pulse was used to probe the sample and then streaked by an rf deflecting cavity. The single-shot, high quality, streaked diffraction pattern allowed structural information within several picoseconds to be continuously temporally resolved with an ∼200 fs resolution. The temporal resolution can be straightforwardly improved to 100 fs by increasing the streaking strength. We foresee that this system would become a powerful tool for ultrafast structural dynamics studies.
Vibronics and plasmonics based graphene sensors
Authors: Rangel Norma L. , Seminario Jorge M.
Published: March 2010

A high sensitivity and selectivity sensor is proposed using graphene ribbons which are able to read molecular vibrations and molecular electrostatic potentials, acting as an amplifier and as a transducer converting molecular signals into current-voltage quantities of standard electronics. Two sensing mechanisms are used to demonstrate the concept using ab initio density functional methods. By using the terahertz region of the spectrum, we can characterize modes when single molecules are adsorbed on the ribbon surface. Characteristic modes can be obtained and used as fingerprints, which can be transduced into current by applying a voltage along the ribbons. On the other hand, the fully delocalized frontier molecular orbitals of graphene ribbons, commonly denominated plasmons in larger solid state structures, are extremely sensitive to any moiety approach; once plasmons are in contact with an “agent” (actually its molecular potential), the transport through the ribbons acting as electrodes catching the signals is strongly affected.
Communications: Entanglement switch for dipole arrays
Authors: Wei Qi , Kais Sabre , Chen Yong P.
Published: March 2010

We propose a new entanglement switch of qubits consisting of electric dipoles oriented along or against an external electric field and coupled by the electric dipole-dipole interaction. The pairwise entanglement can be tuned and controlled by the ratio of the Rabi frequency and the dipole-dipole coupling strength. Tuning the entanglement can be achieved for one, two, and three-dimensional arrangements of the qubits. The feasibility of building such an entanglement switch is also discussed.
Enhancement of depletion forces by electrostatic depletant repulsion
Authors: Buzzaccaro Stefano , Piazza Roberto , Colombo Jader , Parola Alberto
Published: March 2010

A large variety of engaging phenomena stems from the occurrence of short-ranged attractive depletion forces. Yet, so far, most experimental studies have been interpreted on the basis of the simple Asakura–Oosawa model, where the depletion agent can be regarded as ideal. Here, conversely, we focus on a system where strong electrostatic coupling is present in the suspension. Specifically, from measurements of equilibrium sedimentation profiles, we obtain an equation of states for a colloidal system where depletion forces are tuned by the addition of a surfactant. At fixed colloid volume fraction, colloidal aggregation takes place when the surfactant concentration reaches a critical value which rises for increasing ionic strength. Screening repulsive electrostatic interactions inhibits the depletion mechanism and weakens the effective colloid-colloid attraction. The metastable coexistence curve displays the universal scaling behavior predicted for short-ranged potentials. The experimental data are compared with the theoretical predictions of a simple model which includes only electrostatic interactions. The effective depletion force on the colloids is evaluated by using the hypernetted-chain equation of liquid state theory at different salt concentrations. This model provides a convincing interpretation of the observed enhancement of the depletion mechanism by Coulomb repulsion.
Magnetism in armchair BC2N nanoribbons
Authors: Lu Peng , Zhang Zhuhua , Guo Wanlin
Published: March 2010

We show by first-principles calculations that H-terminated armchair BC2N nanoribbons (a-BC2NNRs) have exceptional electronic and magnetic properties. In particular, a-BC2NNRs with the B and N atoms uncoordinated can be either p- or n-doped semiconductors, and the wide ones own spontaneous magnetization. It is shown that the magnetism is induced by the localization of acceptor or donor levels from unpaired B or N atoms, and the magnetic moment increases with further increasing ribbon width. The a-BC2NNRs with B and N atoms coordinated have band gaps decreasing with increasing ribbon width.
Gas convection caused by electron pressure drop in the afterglow of a pulsed inductively coupled plasma discharge
Authors: Cunge G. , Vempaire D. , Sadeghi N.
Published: March 2010

Neutral depletion is an important phenomenon in high-density plasmas. We show that in pulsed discharges, the neutral depletion caused by the electron pressure Pe plays an important role on radical transport. In the afterglow, Pe drops rapidly by electron cooling. So, a neutral pressure gradient built up between the plasma bulk and the reactor walls, which forces the cold surrounding gas to move rapidly toward the reactor center. Measured drift velocity of Al atoms in the early afterglow of Cl2/Ar discharge by time-resolved laser induced fluorescence is as high as 250 ms−1. This is accompanied by a rapid gas cooling.
Enhancement of optical absorption in thin-film organic solar cells through the excitation of plasmonic modes in metallic gratings
Authors: Min Changjun , Li Jennifer , Veronis Georgios , Lee Jung-Yong , Fan Shanhui , Peumans Peter
Published: March 2010

We theoretically investigate the enhancement of optical absorption in thin-film organic solar cells in which the top transparent electrode is partially substituted by a periodic metallic grating. We show that the grating can result in broadband optical absorption enhancement for TM-polarized light, due to the large field enhancement in the vicinity of the strips of the grating, associated with the excitation of plasmonic modes. The overall optical absorption in the organic layers can be greatly enhanced up to ∼50% for such solar cell structures.
Casuarina junghuhniana (Casuarinaceae) in India
Authors: Jayaraj R. S. C.
Published: March 2010

Casuarina junghuhniana Miq., introduced into India in 1996, is gaining importance as an agroforestry species, with potential use in pulp and paper industry. Tree improvement of the species and attempts at clonal forestry are in progress. A hybrid of Casuarina equisetifolia L. and C. junghuhniana, introduced in 1951 from Thailand, is also planted in India, with the wrong identity as Casuarina junghuhniana. The present paper reviews the silviculture and tree improvement of the species, especially the attempts at introduction to various parts of the world by CSIRO, Australia, with special reference to India. The paper also attempts to resolve the confusion between the hybrid and the pure species, among the planting agencies in India.
Interacting effects of copper, nitrogen and ultraviolet radiation on the physiology of three south Pacific kelps
Authors: Huovinen Pirjo , Leal Pablo , Gómez Iván
Published: March 2010

Coastal ecosystems currently face multiple environmental impacts, such as nutrient loading, chemical contamination and enhanced ultraviolet (UV) radiation. Large kelps dominate many rocky shores worldwide and their capacity to handle environmental stress could have major consequences for these systems. The impacts of the interaction of copper (150 μg L–1), nitrate (350 μM) and short-term UV radiation on the physiological responses (photosynthetic activity, contents and anti-oxidant activity of phlorotannins) of three large kelps, Macrocystis pyrifera, Lessonia nigrescens and Durvillaea antarctica, from the coast of Chile were studied during a 2-week laboratory exposure. Macrocystis accumulated the most copper in its tissues, which decreased under nitrate-enriched conditions. Inhibition of photosynthetic activity by copper was observed in all three species (11–30%) after 12 days of incubation, with the strongest response in Lessonia. Nitrate enrichment mitigated the inhibitory effect of copper on photosynthesis in all three species. Soluble phlorotannin content decreased under copper and/or nitrate-enriched conditions with additional short-term UV exposure, particularly in Durvillaea, in which the strongest increase in the anti-oxidant activity of soluble phlorotannins was observed. Overall, the observed physiological responses reflect differences in morpho-functional processes and habitat characteristics of the three kelps and the importance of the interactions of multiple environmental factors.
Zooplankton avoidance behaviour as a response to point sources of hydrocarbon-contaminated water
Authors: Seuront L.
Published: March 2010

Hydrocarbon contamination is a pernicious threat for marine ecosystems as non-lethal effects on the plankton propagate through the food chain and accumulate in the tissues of top predators, ultimately putting human health at risk. The swimming behaviour of the calanoid copepods Eurytemora affinis and Temora longicornis was investigated in relation to point-source contamination by five different-sized patches of the water-soluble fraction of diesel oil diluted at 1 : 100, 1 : 1000 and 1 : 10 000 in estuarine and coastal waters. Both species consistently showed avoidance of the contaminated patches, irrespective of their size and concentration. Specifically, E. affinis exhibited similar sensory abilities irrespective of contaminant concentrations. In contrast, T. longicornis more efficiently identified high-density contaminated patches than low-density ones, and exhibited a negative exponential density dependence of its sensing abilities to the intensity of the chemical cues. Although the conclusions from this experiment need to be generalised to a variety of hydrocarbon contaminants, the present work indicates that zooplankton organisms have the potential to avoid hydrocarbon-contaminated waters, and also suggests that zooplankton swimming behaviour could potentially be used as an endpoint for a toxicity bioassay to assess the presence of toxic chemicals in estuarine and coastal waters.
Characterisation of bovine epiblast-derived outgrowth colonies
Authors: Oestrup Esben , Gjoerret Jakob , Schauser Kirsten , Schmidt Mette , Hall Vanessa , Hyttel Poul
Published: March 2010

The aim of the present study was to characterise bovine epiblast-derived outgrowth colonies (OCs) with respect to the embryonic origin of their cellular components. Epiblasts were isolated mechanically from bovine Day 12 embryos. Epiblasts were cultured on feeder layers of SNL cells (neomycin-resistant leukaemia inhibitory factor (LIF)-producing STO cells) in Dulbecco’s modified Eagle’s medium (DMEM)/F12 medium supplemented with 15% fetal calf serum, 5% KnockOut Serum Replacement, LIF, basic fibroblast growth factor, non-essential amino acids (NEAA) and nucleosides. Samples were fixed on Days 4, 6 and 8 of culture and processed for immunocytochemistry and transmission electron microscopy. Epiblasts formed OCs consisting of a central core of epiblast-like cells with a basal plate of flattened cells extending outwards from the core. The cells of the core showed nuclear octamer-binding transcription factor 4 (OCT4) staining, indicating an epiblast origin, and some also stained positive for cytoplasmic vimentin. Adjacent cells were linked by tight junctions towards the surface of the colony and rested on a basal lamina. The cells of the basal plate predominantly stained for α1-fetoprotein (AFP), indicative of a possible hypoblast origin. Only a few cells scattered within the basal plate exhibited cytokeratin 8 staining, indicating a trophectoderm nature. The intensity of OCT4 and vimentin staining within the core had decreased by Day 8 of culture. In conclusion, OCs derived from bovine Day 12 epiblasts display a central core of OCT4-stained cells of a potential epiblast origin surrounded by a basal plate of mainly AFP-stained cells of a potential hypoblast nature.
Detection of condensin I and II in maturing pig oocytes
Authors: Lišková Lucie , Šušor Andrej , Pivoňková Kateřina , Šašková Adéla , Karabínová Pavla , Kubelka Michal
Published: March 2010

The multiprotein complexes known as condensins (I and II) are major players in chromosome dynamics in mitotic and meiotic cells. Here, we report for the first time the detection of different condensin subunits from both complexes in mammalian oocytes. Using immunoblotting analysis we examined expression levels of condensin subunits during meiotic maturation of porcine oocytes. The expression of the core subunit structural maintenance of chromosomes 2 (SMC2), identical in both condensin complexes, did not change significantly during maturation. Similarly, there was no significant change in the expression of the chromosome associated protein (CAP)-H and CAP-H2 subunits, components of condensin I and II, respectively. Conversely, the expression profiles of CAP-G, CAP-D2 (condensin I) and CAP-D3 (condensin II) were more interesting. At least two isoforms of the CAP-D2 subunit were detected, along with three isoforms of the CAP-D3 and CAP-G subunits. We suggest that this diverse migration of subunit isoforms is due to post-translational modification. Earlier, it was reported that non-SMC proteins are phosphorylated by cyclin-dependent kinase 1. In the present study, we analysed the phosphorylation status of the three subunits in oocyte extracts using alkaline phosphatase treatment and we found that at least the fastest migrating form of CAP-D3 was likely to be phosphorylated in maturing porcine oocytes. In addition, the localisation of CAP-H and CAP-H2 subunits was examined using immunofluorescence staining with specific antibodies, as well as following microinjection of their enhanced green fluorescent protein-tagged mRNA into germinal vesicle-stage oocytes. CAP-H was found in the cytoplasm, whereas CAP-H2 was localised within the nucleus.
Abnormalities in the transcription of reprogramming genes related to global epigenetic events of cloned endangered felid embryos
Authors: Imsoonthornruksa S. , Lorthongpanich C. , Sangmalee A. , Srirattana K. , Laowtammathron C. , Tunwattana W. , Somsa W. , Ketudat-Cairns M. , Parnpai R.
Published: March 2010

The present study examined transcription levels of the Oct4, DNMT1, DNMT3a, DNMT3b, HAT1 and HDAC1 genes in cloned felid embryos developing from single one-cell to blastocyst stages. IVF, cloned domestic and leopard cat embryos had low Oct4 and HAT1 levels during the early stages, but transcript expression increased at the eight-cell and blastocyst stages. In contrast, expression in the cloned marble cat embryos was low at all stages. Transcription patterns of HDAC1 were altered in cloned embryos compared with IVF embryos. Transcription levels of DNMT1 decreased markedly throughout development of both IVF and cloned embryos. In IVF embryos, DNMT3a transcripts rarely appeared in the four- to eight-cell stages, but levels increased in the morula to blastocyst stages. In contrast, in cloned embryos, DNMT3a transcript levels were high at the one- to two-cell stages, decreased during subsequent cell division and then increased again at the blastocyst stage. The IVF and cloned embryos showed similar DNMT3b transcription patterns, starting with low levels at the two-cell to morula stages and reaching a maximum at the blastocyst stage. These results suggest that the low level of Oct4 transcripts may be responsible, in part, for the failure of blastocyst production in the cloned marbled cat. However, higher transcription of the DNA methylation genes and lower transcription of the histone acetylation genes were observed in cloned compared with IVF embryos, suggesting that the felids’ donor nucleus could not completely reprogramme the nuclear genome and so the re-establishment of embryonic totipotency was not achieved.
Spatiotemporal expression of α1, α3 and β1 integrin subunits is altered in rat myometrium during pregnancy and labour
Authors: Williams S. J. , Shynlova O. , Lye S. J. , MacPhee D. J.
Published: March 2010

Integrins are transmembrane extracellular matrix (ECM) receptors composed of α- and β-subunits. Integrins can cluster to form focal adhesions and, because there is significant ECM remodelling and focal adhesion turnover in the rat myometrium during late pregnancy, we hypothesised that the expression of α1, α3 and β1 integrin subunits in the rat myometrium would be altered at this time to accommodate these processes. Expression of α1 and β1 integrin subunit mRNA was significantly increased on Days 6–23 of pregnancy compared with non-pregnant (NP) and postpartum (PP) time points (P < 0.05). In contrast, α3 integrin subunit mRNA expression was significantly increased on Days 14, 21 and 22 compared with NP, Day 10, 1 day PP and 4 days PP (P < 0.05). A relative gene expression study revealed that, of the integrins studied, the expression of β1 integrin mRNA was highest in pregnant rat myometrium. The α1, α3 and β1 integrin subunit proteins became immunolocalised to myocyte membranes in situ by late pregnancy and labour in both myometrial muscle layers. Increased α1, α3 and β1 integrin gene expression during gestation and the specific detection of these subunits in myocyte membranes during late pregnancy and labour may contribute to the cell–ECM interactions required for the development of a mechanical syncytium.
Preservation of beluga (Delphinapterus leucas) spermatozoa using a trehalose-based cryodiluent and directional freezing technology
Authors: O'Brien J. K. , Robeck T. R.
Published: March 2010

A beluga (Delphinapterus leucas) sperm preservation method was developed for use in genome banking and AI. In Study 1, glycerol-based cryodiluents (modified BF5F and modified Platz Diluent Variant (PDV)) were unable to maintain adequate progressive motility using straws (fast and slow freezing rate (FR)) or pellets (slow FR). Neither freezing method nor FR affected in vitro sperm characteristics (P > 0.05), but retention of prefreeze progressive motility following thawing was greater (P < 0.05) for BF5F (21%) than PDV (15%). In Study 2, examining the effects of straw freeze–thawing using BF5F with glycerol (1 and 3%, v/v) or trehalose (46 and 91 mM) on sperm characteristics, samples cryopreserved in trehalose exhibited superior (P < 0.05) in vitro parameters compared with their glycerol-treated counterparts. In Study 3, compared with a straw method, directional freezing using 91 mM trehalose enhanced (P < 0.05) sperm characteristics, with samples retaining 38%, 75% and 61% of their prefreeze progressive motility, curvilinear velocity and viability, respectively. A higher (P < 0.05) proportion of motile spermatozoa displayed rapid velocity after directional (21 ± 1%) compared with straw (12 ± 3%) freezing. Systematic development of a cryodiluent and the use of directional freezing resulted in beluga spermatozoa exhibiting adequate post-thaw quality for genome banking and use in AI.
Ago2 and GW182 expression in mouse preimplantation embryos: a link between microRNA biogenesis and GW182 protein synthesis
Authors: Shen Xing-Hui , Han Young-Joon , Cui Xiang-Shun , Kim Nam-Hyung
Published: March 2010

MicroRNA-mediated RNA interference appears to play a role in early development and differentiation processes in preimplantation embryos. However, the expression of its key effectors, including Ago2, a key component of the RNA-induced silencing complex, and GW182, a critical component of GW bodies (GWBs), has not been assessed in preimplantation embryos. To characterise the roles of Ago2 and GW182 in early embryo development, we determined their transcription and protein synthesis in mouse embryos. Transcript levels of Ago2 and GW182 increased steadily from the one-cell stage through to the blastocyst stage when data were not normalised against an internal reference. However, when normalised against the internal standard, transcript levels for both genes were highest in four-cell stage embryos and decreased steadily through to the blastocyst stage. Indirect immunocytochemistry showed that both AGO2 and GW182 proteins were expressed in each stage in the early embryo and were observed to colocalise in the morula and blastocyst stages. Specific silencing of mRNA expression by short interference (si) RNA against Ago2 or Dicer1 decreased the expression of selected apoptosis- and development-related microRNAs, but did not inhibit development up to the blastocyst stage. However, transcription levels of Oct3/4, Nanog and Sox2 were decreased in both Ago2- and Dicer1-knockdown embryos at the blastocyst stage. Furthermore, although knockdown of these genes did not change transcript levels of GW182, GW182 protein synthesis was decreased in blastocyst stage embryos. These results suggest that Ago2 and Dicer1 regulate GW182 protein expression in mouse embryos, which is linked to microRNA biogenesis and likely to be important for differentiation in the blastocyst stage.
Impact of subsoil physicochemical constraints on crops grown in the Wimmera and Mallee is reduced during dry seasonal conditions
Authors: Nuttall J. G. , Armstrong R. D.
Published: March 2010

Subsoil physicochemical constraints can limit crop production on alkaline soils of south-eastern Australia. Fifteen farmer paddocks sown to a range of crops including canola, lentil, wheat, and barley in the Wimmera and Mallee of Victoria and the mid-north and Eyre Peninsula of South Australia were monitored from 2003 to 2006 to define the relationship between key abiotic/edaphic factors and crop growth. The soils were a combination of Calcarosol and Vertosol profiles, most of which had saline and sodic subsoils. There were significant correlations between ECe and Cl– (r = 0.90), ESP and B (r = 0.82), ESP and ECe (r = 0.79), and ESP and Cl– (r = 0.73). The seasons monitored had dry pre-cropping conditions and large variations in spring rainfall in the period around flowering. At sowing, the available soil water to a depth of 1.2 m (θa) averaged 3 mm for paddocks sown to lentils, 28 mm for barley, 44 mm for wheat, and 92 mm for canola. Subsoil constraints affected canola and lentil crops but not wheat or barley. For lentil crops, yield variation was largely explained by growing season rainfall (GSR) and θa in the shallow subsoil (0.10–0.60 m). Salinity in this soil layer affected lentil crops through reduced water extraction and decreased yields where ECe exceeded 2.2 dS/m. For canola crops, GSR and θa in the shallow (0.10–0.60 m) and deep (0.60–1.20 m) layers were important factors explaining yield variation. Sodicity (measured as ESP) in the deep subsoil (0.80–1.00 m) reduced canola growth where ESP exceeded 16%, corresponding to a 500 kg/ha yield penalty. For cereal crops, rainfall in the month around anthesis was the most important factor explaining grain yield, due to the large variation in rainfall during October combined with the determinant nature of these crops. For wheat, θa in the shallow subsoil (0.10–0.60 m) at sowing was also an important factor explaining yield variation. Subsoil constraints had no impact on cereal yield in this study, which is attributed to the lack of available soil water at depth, and the crops’ tolerance of the physicochemical conditions encountered in the shallow subsoil, where plant-available water was more likely to occur. Continuing dry seasonal conditions may mean that the opportunity to recharge soil water in the deeper subsoil, under continuous cropping systems, is increasingly remote. Constraints in the deep subsoil are therefore likely to have reduced impact on cereals under these conditions, and it is the management of water supply, from GSR and accrued soil water, in the shallow subsoil that will be increasingly critical in determining crop yields in the future.
PI3 kinase signaling is involved in Aβ-induced memory loss in
Drosophila
Authors: Chiang Hsueh-Cheng , Wang Lei , Xie Zuolei , Yau Alice , Zhong Yi
Published: March 2010

Multiple intracellular signals are altered in Alzheimer's disease brain tissues, including the PI3K/Akt pathway. However, the pathological relevance of such alterations is poorly understood. In vitro studies yield results that seem to be consistent with the conventional perception in which an up-regulation of the cell survival pathway, PI3K pathway, is protective in Alzheimer's disease pathogenesis. The current in vivo genetic approach, however, reveals that inhibition of the PI3K pathway leads to rescuing of the β-amyloid peptide (Aβ)-induced memory loss in the
Drosophila
brain. We began our inquiry into the molecular basis of this memory loss by studying Aβ42-induced enhancement of long-term depression. We found that long-term depression is restored to a normal level through inhibition of PI3K activity. Aβ42-induced PI3K hyperactivity is directly confirmed by immunostaining of the PI3K phosphorylation targets, phospholipids. Such observations lead to the following demonstration that Aβ42-induced memory loss can be rescued through genetic silencing or pharmacological inhibition of PI3K functions. Our data suggest that Aβ42 stimulates PI3K, which in turn causes memory loss in association with an increase in accumulation of Aβ42 aggregates.
Measurement of red blood cell mechanics during morphological changes
Authors: Park YongKeun , Best Catherine A. , Badizadegan Kamran , Dasari Ramachandra R. , Feld Michael S. , Kuriabova Tatiana , Henle Mark L. , Levine Alex J. , Popescu Gabriel
Published: March 2010

The human red blood cell (RBC) membrane, a fluid lipid bilayer tethered to an elastic 2D spectrin network, provides the principal control of the cell’s morphology and mechanics. These properties, in turn, influence the ability of RBCs to transport oxygen in circulation. Current mechanical measurements of RBCs rely on external loads. Here we apply a noncontact optical interferometric technique to quantify the thermal fluctuations of RBC membranes with 3 nm accuracy over a broad range of spatial and temporal frequencies. Combining this technique with a new mathematical model describing RBC membrane undulations, we measure the mechanical changes of RBCs as they undergo a transition from the normal discoid shape to the abnormal echinocyte and spherical shapes. These measurements indicate that, coincident with this morphological transition, there is a significant increase in the membrane’s shear, area, and bending moduli. This mechanical transition can alter cell circulation and impede oxygen delivery.
Climate as a contributing factor in the demise of Angkor, Cambodia
Authors: Buckley Brendan M. , Anchukaitis Kevin J. , Penny Daniel , Fletcher Roland , Cook Edward R. , Sano Masaki , Nam Le Canh , Wichienkeeo Aroonrut , Minh Ton That , Hong Truong Mai
Published: March 2010

The “hydraulic city” of Angkor, the capitol of the Khmer Empire in Cambodia, experienced decades-long drought interspersed with intense monsoons in the fourteenth and fifteenth centuries that, in combination with other factors, contributed to its eventual demise. The climatic evidence comes from a seven-and-a-half century robust hydroclimate reconstruction from tropical southern Vietnamese tree rings. The Angkor droughts were of a duration and severity that would have impacted the sprawling city’s water supply and agricultural productivity, while high-magnitude monsoon years damaged its water control infrastructure. Hydroclimate variability for this region is strongly and inversely correlated with tropical Pacific sea surface temperature, indicating that a warm Pacific and El Niño events induce drought at interannual and interdecadal time scales, and that low-frequency variations of tropical Pacific climate can exert significant influence over Southeast Asian climate and society.
A theoretical framework for gene induction and experimental comparisons
Authors: Ong Karen M. , Blackford John A. , Kagan Benjamin L. , Simons S. Stoney , Chow Carson C.
Published: March 2010

Ligand-mediated gene induction by steroid receptors is a multistep process characterized by a dose–response curve for gene product that follows a first-order Hill equation. This behavior has classically been explained by steroid binding to receptor being the rate-limiting step. However, this predicts a constant potency of gene induction (EC
50
) for a given receptor-steroid complex, which is challenged by the findings that various cofactors/reagents can alter this parameter in a gene-specific manner. These properties put strong constraints on the mechanisms of gene induction and raise two questions: How can a first-order Hill dose–response curve (FHDC) arise from a multistep reaction sequence, and how do cofactors modify potency? Here we introduce a theoretical framework in which a sequence of steps yields an FHDC for the final product as a function of the initial agonist concentration. An exact determination of all constants is not required to describe the final FHDC. The theory predicts mechanisms for cofactor/reagent effects on gene-induction potency and maximal activity and it assigns a relative order to cofactors in the sequence of steps. The theory is supported by several observations from glucocorticoid receptor-mediated gene induction. It identifies the mechanism and matches the measured dose–response curves for different concentrations of the combination of cofactor Ubc9 and receptor. It also predicts that an FHDC cannot involve the DNA binding of preformed receptor dimers, which is validated experimentally. The theory is general and can be applied to any biochemical reaction that shows an FHDC.
Bidirectional changes to hippocampal theta–gamma comodulation predict memory for recent spatial episodes
Authors: Shirvalkar Prasad R. , Rapp Peter R. , Shapiro Matthew L.
Published: March 2010

Episodic memory requires the hippocampus, which is thought to bind cortical inputs into conjunctive codes. Local field potentials (LFPs) reflect dendritic and synaptic oscillations whose temporal structure may coordinate cellular mechanisms of plasticity and memory. We now report that single-trial spatial memory performance in rats was predicted by the power comodulation of theta (4–10 Hz) and low gamma (30–50 Hz) rhythms in the hippocampus. Theta–gamma comodulation (TGC) was prominent during successful memory retrieval but was weak when memory failed or was unavailable during spatial exploration in sample trials. Muscimol infusion into medial septum reduced the probability of TGC and successful memory retrieval. In contrast, patterned electrical stimulation of the fimbria-fornix increased TGC in amnestic animals and partially rescued memory performance in the water maze. The results suggest that TGC accompanies memory retrieval in the hippocampus and that patterned brain stimulation may inform therapeutic strategies for cognitive disorders.
Ventral striatal plasticity and spatial memory
Authors: Ferretti Valentina , Roullet Pascal , Sargolini Francesca , Rinaldi Arianna , Perri Valentina , Del Fabbro Martina , Costantini Vivian J. A. , Annese Valentina , Scesa Gianluigi , De Stefano Maria Egle , Oliverio Alberto , Mele Andrea
Published: March 2010

Spatial memory formation is a dynamic process requiring a series of cellular and molecular steps, such as gene expression and protein translation, leading to morphological changes that have been envisaged as the structural bases for the engram. Despite the role suggested for medial temporal lobe plasticity in spatial memory, recent behavioral observations implicate specific components of the striatal complex in spatial information processing. However, the potential occurrence of neural plasticity within this structure after spatial learning has never been investigated. In this study we demonstrate that blockade of cAMP response element binding protein–induced transcription or inhibition of protein synthesis or extracellular proteolytic activity in the ventral striatum impairs long-term spatial memory. These findings demonstrate that, in the ventral striatum, similarly to what happens in the hippocampus, several key molecular events crucial for the expression of neural plasticity are required in the early stages of spatial memory formation.
Structural basis for solute transport, nucleotide regulation, and immunological recognition of
Neisseria meningitidis
PorB
Authors: Tanabe Mikio , Nimigean Crina M. , Iverson T. M.
Published: March 2010

PorB is the second most prevalent outer membrane protein in
Neisseria meningitidis
. PorB is required for neisserial pathogenesis and can elicit a Toll-like receptor mediated host immune response. Here, the x-ray crystal structure of PorB has been determined to 2.3 Å resolution. Structural analysis and cocrystallization studies identify three putative solute translocation pathways through the channel pore: One pathway transports anions nonselectively, one transports cations nonselectively, and one facilitates the specific uptake of sugars. During infection, PorB likely binds host mitochondrial ATP, and cocrystallization with the ATP analog AMP–PNP suggests that binding of nucleotides regulates these translocation pathways both by partial occlusion of the pore and by restricting the motion of a putative voltage gating loop. PorB is located on the surface of
N. meningitidis
and can be recognized by receptors of the host innate immune system. Features of PorB suggest that Toll-like receptor mediated recognition outer membrane proteins may be initiated with a nonspecific electrostatic attraction.
Oral delivery of bioencapsulated coagulation factor IX prevents inhibitor formation and fatal anaphylaxis in hemophilia B mice
Authors: Verma Dheeraj , Moghimi Babak , LoDuca Paul A. , Singh Harminder D. , Hoffman Brad E. , Herzog Roland W. , Daniell Henry
Published: March 2010

To address complications of pathogenic antibody or life-threatening anaphylactic reactions in protein replacement therapy for patients with hemophilia or other inherited protein deficiencies, we have developed a prophylactic protocol using a murine hemophilia B model. Oral delivery of coagulation factor IX fused with cholera toxin β-subunit (with or without a furin cleavage site; CTB-FFIX or CTB-FIX), expressed in chloroplasts (up to 3.8% soluble protein or 0.4 mg/g leaf tissue), bioencapsulated in plant cells, effectively blocked formation of inhibitory antibodies (undetectable or up to 100-fold less than controls). Moreover, this treatment eliminated fatal anaphylactic reactions that occurred after four to six exposures to intravenous F.IX. Whereas only 20–25% of control animals survived after six to eight F.IX doses, 90–93% of F.IX-fed mice survived 12 injections without signs of allergy or anaphylaxis. Immunostaining confirmed delivery of F.IX to Peyer's patches in the ileum. Within 2–5 h, feeding of CTB-FFIX additionally resulted in systemic delivery of F.IX antigen. This high-responder strain of hemophilia B mice represents a new animal model to study anaphylactic reactions. The protocol was effective over a range of oral antigen doses (equivalent to 5–80 μg recombinant F.IX/kg), and controlled inhibitor formation and anaphylaxis long-term, up to 7 months (∼40% life span of this mouse strain). Oral antigen administration caused a deviant immune response that suppressed formation of IgE and inhibitory antibodies. This cost-effective and efficient approach of antigen delivery to the gut should be applicable to several genetic diseases that are prone to pathogenic antibody responses during treatment.
Regulators of G-protein Signaling accelerate GPCR signaling kinetics and govern sensitivity solely by accelerating GTPase activity
Authors: Lambert Nevin A. , Johnston Christopher A. , Cappell Steven D. , Kuravi Sudhakiranmayi , Kimple Adam J. , Willard Francis S. , Siderovski David P.
Published: March 2010

G-protein heterotrimers, composed of a guanine nucleotide-binding Gα subunit and an obligate Gβγ dimer, regulate signal transduction pathways by cycling between GDP- and GTP-bound states. Signal deactivation is achieved by Gα-mediated GTP hydrolysis (GTPase activity) which is enhanced by the GTPase-accelerating protein (GAP) activity of “regulator of G-protein signaling” (RGS) proteins. In a cellular context, RGS proteins have also been shown to speed up the onset of signaling, and to accelerate deactivation without changing amplitude or sensitivity of the signal. This latter paradoxical activity has been variably attributed to GAP/enzymatic or non-GAP/scaffolding functions of these proteins. Here, we validated and exploited a Gα switch-region point mutation, known to engender increased GTPase activity, to mimic
in cis
the GAP function of RGS proteins. While the transition-state, GDP·AlF
4
−
-bound conformation of the G202A mutant was found to be nearly identical to wild-type, Gα
i1
(G202A)·GDP assumed a divergent conformation more closely resembling the GDP·AlF
4
−
-bound state. When placed within
Saccharomyces cerevisiae
Gα subunit Gpa1, the fast-hydrolysis mutation restored appropriate dose–response behaviors to pheromone signaling in the absence of RGS-mediated GAP activity. A bioluminescence resonance energy transfer (BRET) readout of heterotrimer activation with high temporal resolution revealed that fast intrinsic GTPase activity could recapitulate
in cis
the kinetic sharpening (increased onset and deactivation rates) and blunting of sensitivity also engendered by RGS protein action
in trans
. Thus Gα-directed GAP activity, the first biochemical function ascribed to RGS proteins, is sufficient to explain the activation kinetics and agonist sensitivity observed from G-protein–coupled receptor (GPCR) signaling in a cellular context.