bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of hydrodynamic slip on the electrophoretic mobility of a spherical colloidal particle
Authors: Khair Aditya S. , Squires Todd M.
Published: April 2009

Recent theoretical studies have suggested a significant enhancement in electro-osmotic flows over hydrodynamically slipping surfaces, and experiments have indeed measured O(1) enhancements. In this paper, we investigate whether an equivalent effect occurs in the electrophoretic motion of a colloidal particle whose surface exhibits hydrodynamic slip. To this end, we compute the electrophoretic mobility of a uniformly charged spherical particle with slip length λ as a function of the zeta (or surface) potential of the particle ζ and diffuse-layer thickness κ−1. In the case of a thick diffuse layer, κa⪡1 (where a is the particle size), simple arguments show that slip does lead to an O(1) enhancement in the mobility, owing to the reduced viscous drag on the particle. On the other hand, for a thin-diffuse layer κa⪢1, the situation is more complicated. A detailed asymptotic analysis, following the method of O’Brien [J. Colloid Interface Sci. 92, 204 (1983)], reveals that an O(κλ) increase in the mobility occurs at low-to-moderate zeta potentials (with ζ measured on the scale of thermal voltage kBT/e≈25 mV). However, as ζ is further increased, the mobility decreases and ultimately becomes independent of the slip length—the enhancement is lost—which is due to the importance of nonuniform surface conduction within the thin-diffuse layer, at large ζ and large, but finite, κa. Our asymptotic calculations for thick and thin-diffuse layers are corroborated and bridged by computation of the mobility from the numerical solution of the full electrokinetic equations (using the method of O’Brien and White [J. Chem. Soc., Faraday Trans. 2 74, 1607 (1978)]). In summary, then, we demonstrate that hydrodynamic slip can indeed produce an enhancement in the electrophoretic mobility; however, such enhancements will not be as dramatic as the previously studied κa→∞ limit would suggest. Importantly, this conclusion applies not only to electrophoresis but also to electro-osmosis over highly charged surfaces, wherein any inhomogeneities (e.g., due to curvature, roughness, charge patterning, or a variation in slip length) will drive nonuniform surface conduction, which prevents the significant slip-driven flow enhancements predicted for a uniform highly charged surface.
Atomic Cholesky decompositions: A route to unbiased auxiliary basis sets for density fitting approximation with tunable accuracy and efficiency
Authors: Aquilante Francesco , Gagliardi Laura , Pedersen Thomas Bondo , Lindh Roland
Published: April 2009

Cholesky decomposition of the atomic two-electron integral matrix has recently been proposed as a procedure for automated generation of auxiliary basis sets for the density fitting approximation [F. Aquilante et al., J. Chem. Phys. 127, 114107 (2007)]. In order to increase computational performance while maintaining accuracy, we propose here to reduce the number of primitive Gaussian functions of the contracted auxiliary basis functions by means of a second Cholesky decomposition. Test calculations show that this procedure is most beneficial in conjunction with highly contracted atomic orbital basis sets such as atomic natural orbitals, and that the error resulting from the second decomposition is negligible. We also demonstrate theoretically as well as computationally that the locality of the fitting coefficients can be controlled by means of the decomposition threshold even with the long-ranged Coulomb metric. Cholesky decomposition-based auxiliary basis sets are thus ideally suited for local density fitting approximations.
Quantitative optical recognition of highly reproducible ultrathin oxide films in microelectrochemical anodization
Authors: Mardare Andrei Ionut , Hassel Achim Walter
Published: April 2009

Automatized microelectrochemical investigations are achieved using a scanning droplet cell. The area reproducibility for a 100 μm oxide spot is found to be better than 1%, a value typically difficult to reach even in macroscopic samples. A systematic change in color appearance is seen for oxide films with a thickness ranging from 14 to 27 nm. Analysis of optical images yields a strictly linear relation between relative transmission and anodization charge and thus allows determination of the oxide thickness with a remarkable precision better than 0.5 nm at an absolute film thickness value that is at least a factor of 20 smaller than the wavelength of light.
An oleic acid-capped CdSe quantum-dot sensitized solar cell
Authors: Chen Jing , Song J. L. , Sun X. W. , Deng W. Q. , Jiang C. Y. , Lei W. , Huang J. H. , Liu R. S.
Published: April 2009

In this letter, we report an oleic acid (OA)-capped CdSe quantum-dot sensitized solar cell (QDSSC) with an improved performance. The TiO2/OA-CdSe photoanode in a two-electrode device exhibited a photon-to-current conversion efficiency of 17.5% at 400 nm. At AM1.5G irradiation with 100 mW/cm2 light intensity, the QDSSCs based on OA-capped CdSe showed a power conversion efficiency of about 1%. The function of OA was to increase QD loading, extend the absorption range and possibly suppress the surface recombination.
A multimodal spectroscopy system for real-time disease diagnosis
Authors: Šćepanović Obrad R. , Volynskaya Zoya , Kong Chae-Ryon , Galindo Luis H. , Dasari Ramachandra R. , Feld Michael S.
Published: April 2009

The combination of reflectance, fluorescence, and Raman spectroscopy—termed multimodal spectroscopy (MMS)—provides complementary and depth-sensitive information about tissue composition. As such, MMS is a promising tool for disease diagnosis, particularly in atherosclerosis and breast cancer. We have developed an integrated MMS instrument and optical fiber spectral probe for simultaneous collection of all three modalities in a clinical setting. The MMS instrument multiplexes three excitation sources, a xenon flash lamp (370–740 nm), a nitrogen laser (337 nm), and a diode laser (830 nm), through the MMS probe to excite tissue and collect the spectra. The spectra are recorded on two spectrograph/charge-coupled device modules, one optimized for visible wavelengths (reflectance and fluorescence) and the other for the near-infrared (Raman), and processed to provide diagnostic parameters. We also describe the design and calibration of a unitary MMS optical fiber probe 2 mm in outer diameter, containing a single appropriately filtered excitation fiber and a ring of 15 collection fibers, with separate groups of appropriately filtered fibers for efficiently collecting reflectance, fluorescence, and Raman spectra from the same tissue location. A probe with this excitation/collection geometry has not been used previously to collect reflectance and fluorescence spectra, and thus physical tissue models (“phantoms”) are used to characterize the probe’s spectroscopic response. This calibration provides probe-specific modeling parameters that enable accurate extraction of spectral parameters. This clinical MMS system has been used recently to analyze artery and breast tissue in vivo and ex vivo.
High-Q terahertz microcavities in silicon photonic crystal slabs
Authors: Yee Cristo M. , Sherwin Mark S.
Published: April 2009

Photonic crystal cavities consisting of three holes missing along a principal axis in a triangular lattice of holes in a silicon slab were fabricated. Each cavity was built into a waveguide to form a Lorentzian filter. Two samples were constructed with lattice constants a=80 and 76 μm, with a radius r=0.30a in a 44 μm thick high-resistivity silicon wafer. Transmission experiment show a single sharp resonance near 1 THz in each sample with quality factor Q as high as 1020. Contributions to the measured Q from cavity-waveguide coupling, radiative loss, and material loss are determined.
Metallic-like photoluminescence and absorption in fused silica surface flaws
Authors: Laurence Ted A. , Bude Jeff D. , Shen Nan , Feldman Theodore , Miller Philip E. , Steele William A. , Suratwala Tayyab
Published: April 2009

Using high-sensitivity confocal time-resolved photoluminescence (PL) techniques, we report an ultrafast PL (40 ps–5 ns) from impurity-free surface flaws on fused silica, including polished, indented, or fractured surfaces of fused silica, and from laser-heated evaporation pits. This PL is excited by the single-photon absorption of sub-band gap light, and is especially bright in fractures. Regions which exhibit this PL are strongly absorptive well below the band gap, as evidenced by a propensity to damage with 3.5 eV nanosecond-scale laser pulses.
Plasma energy and work function of conducting transition metal nitrides for electronic applications
Authors: Matenoglou G. M. , Koutsokeras L. E. , Patsalas P.
Published: April 2009

The combination of electrical conductivity, chemical and metallurgical stability, refractory character, having lattice constants that are close to those of III-nitrides makes transition metal nitrides promising candidates for electronics and device applications. We study the structure, stability, and the plasma energy of stoichiometric, transition metal nitrides of similar crystal quality as well as the widest variety of their ternaries ever reported. We establish the phase spaces of the plasma energy (6.9–10.5 eV) and the work function (3.7–5.1 eV) of these complex nitrides with their lattice constant (0.416–0.469 nm) and we investigate the limits of their applications.
Diffracted magneto-optical Kerr effect in one-dimensional magnetic gratings
Authors: Kim J. B. , Lu Y. H. , Cho M. H. , Lee G. J. , Lee Y. P. , Rhee J. Y. , Yoon C. S.
Published: April 2009

One-dimensional Co2MnSi magnetic gratings were fabricated with a significant ease by using the interference pattern of two femtosecond-laser beams which resulted in a selective-area annealing of the as-deposited Co2MnSi film. The longitudinal Kerr rotation of the negative first-order diffracted beam was nearly 30 times larger than that of the zeroth-order one in a sample fabricated with the optimal conditions. The enhancement strongly depends on the grating depth, which varies with the number of laser shots, confirming the theoretical result that the magneto-optical Kerr-effect enhancement is reduced as the grating depth increases.
Electronic property of Na-doped epitaxial graphenes on SiC
Authors: Choi Seon-Myeong , Jhi Seung-Hoon
Published: April 2009

The electronic property of epitaxial graphenes with Na adsorption or intercalation is studied with the use of pseudopotential density functional method. It is found that the charge transfer and the Na binding energy show strong coverage dependence. Calculated energetics shows that Na prefers the intercalation between the buffer and top graphene layers to the adsorption on top graphene layer. The buffer layer is inert to Na adsorption on top graphene layer but it is charged when Na atoms are intercalated. This indicates that the conduction of epitaxial graphenes can be affected significantly by Na intercalation.
Half-metallic ferromagnetism in C-doped ZnS: Density functional calculations
Authors: Fan S. W. , Yao K. L. , Liu Z. L.
Published: April 2009

Using the full-potential linearized augmented plane wave method, we study the magnetism and electronic structures of C-doped ZnS (zinc-blende structure). Calculations indicate that C can induce stable ferromagnetic ground state in ZnS hosts. The magnetic moment of the 64-atom supercell (containing one CS defect) is 2.00μB. Low formation energy implies ZnS0.96 875C0.03 125 can be fabricated experimentally. Electronic structures show C-doped ZnS is p-type half-metallic ferromagnetic semiconductor and hole-mediated double exchange is responsible for the ferromagnetism. Relative shallow acceptor levels indicate C-doped ZnS is ionized easily at working temperatures. Several doped configurations calculations suggest ferromagnetic couplings exist between the doped carbon atoms.
Thermoelectric properties of stoichiometric and hole-doped CrN
Authors: Quintela C. X. , Rivadulla F. , Rivas J.
Published: April 2009

We report the thermoelectric figure of merit of chromium nitride, CrN, and its optimization through hole-doping. CrN is a degenerate semiconductor with large thermoelectric power, reaching −185 μV/K at 420 K. The resistivity can be reduced through hole-doping in the series Cr1−xVxN, keeping a large thermopower. The thermal conductivity of CrN is rather low compared to other transition-metal nitrides, reaching its minimum value of 1.0 W/m K at 267 K. The largest ZT=0.04 was measured for Cr0.9V0.1N at room temperature. Our results suggest that CrN could be a good starting point for the design of a thermoelectric material with optimal mechanical properties.
Detection and discrimination of optical absorption and shear stiffness at depth in tissue-mimicking phantoms by transient optoelastography
Authors: Daoudi Khalid , Boccara Albert-Claude , Bossy Emmanuel
Published: April 2009

This work investigates the ability of transient optoelastography to detect both shear stiffness contrasts and optical absorption contrasts embedded deep in tissuelike media. The technique consists of a camera-based optical detection scheme designed to detect selectively the transient shear motion created at depth by the acoustic radiation force in optically turbid media. It is demonstrated on tissue-mimicking phantoms that transient optoelastography is not only sensitive to both optical absorption and shear stiffness contrasts, but also provides discrimination between these two types of contrasts.
“Villari reversal” in the exchange biased [Pd/Co]5/FeMn thin films with perpendicular anisotropy
Authors: Jeun Minhong , Lin Lin , Joo Ho Wan , Bae Seongtae , Heo Jang , Lee Ky Am
Published: April 2009

Exchange bias characteristics of [Pd/Co]5/FeMn thin films with perpendicular anisotropy have been explored by externally applying a mechanical stress for a magnetic pressure sensor application. It was found that the physical behavior of exchange bias field and coercivity of the [Pd/Co]5/FeMn thin films are closely relevant to the strength of applied stress and its direction. Magnetoelastic energy calculation and the physical analysis demonstrated that the stress-induced “Villari reversal” of the Co magnetizations directly resulted in changing the perpendicular anisotropy of the [Co/Pd] multilayers is primarily responsible for the variation in exchange bias coupling occurred at the [Co/Pd] and FeMn interface.
High performance of diamond p+-i-n+ junction diode fabricated using heavily doped p+ and n+ layers
Authors: Oyama Kazuihiro , Ri Sung-Gi , Kato Hiromitsu , Ogura Masahiko , Makino Toshiharu , Takeuchi Daisuke , Tokuda Norio , Okushi Hideyo , Yamasaki Satoshi
Published: April 2009

A good ideality factor and rectification ratio were obtained in a p+-i-n+ diamond diode with p+ and n+ doping levels of ∼1020 cm−3, where the hopping conduction mechanism dominates in the bulk p+ and n+ layers. The diode characteristics show a rectification ratio of 108 at ±10 V and an ideality factor of n=1.32. This diode showed ruggedness with a large current density of over 15 000 A/cm2 at +35 V. These results indicate the possibility of large-current devices.
Giant optical resonances due to gain-assisted Bloch surface plasmons
Authors: Kobyakov Andrey , Zakharian Aramais R. , Gundu Krishna M. , Darmanyan Sergey A.
Published: April 2009

We theoretically study Bloch surface plasmon (BSP) resonances in a thin subwavelength-structured metallic film adjacent to a submicron dielectric layer with gain. We show that for a planar gold-silver bimetallic grating resonant excitation of a BSP with the optimum value of gain may result in giant amplification of both transmitted and reflected waves. We explain the effect and illustrate how the electromagnetic near-field structure determines the type of interference (constructive or destructive) between the eigenmodes of the system, which results in either strong enhancement or suppression of the scattered waves.
Nonplanar chiral metamaterials with negative index
Authors: Wang Bingnan , Zhou Jiangfeng , Koschny Thomas , Soukoulis Costas M.
Published: April 2009

We demonstrate experimentally and numerically that nonplanar chiral metamaterials give giant optical activity, circular dichroism, and negative refractive index. The transmission, reflection, and the retrieval results of the experiments agree pretty well with the simulations. This is an important step toward the design and fabrication of three-dimensional isotropic chiral metamaterials.
Thickness dependence of nanofilm elastic modulus
Authors: Fedorchenko Alexander I. , Wang An-Bang , Cheng Henry H.
Published: April 2009

Young’s modulus is a fundamental physical parameter that determines not only the mechanic but also the electronic properties of a solid thin film. In here, we show that the elastic modulus is not a constant as that of conventional treatment but varies with film thickness. Scaling behavior is found based on the theoretical analysis of the free energy of surface-to-volume ratio of the film and results of the elastic modulus measurement. It has been shown that there exists some film thickness hb when the surface energy of the film comes into play. The hb is inverse proportional to the bulk Young’s modulus and depends strongly on the in-plain strain ε0 as ε0−2. For Si nanofilms, the variation of dimensionless elastic modulus Ψ=E/Ebulk with the dimensionless film thickness η=h/hb can be represented in the following form: Ψ=η0.226. The present investigation illustrates the importance of the effect of dimensionality on the basic parameter of a thin film as well as providing important implications for electronic devices, in particular for the Si-based strained nanodevices.
Magnetic bead counter using a micro-Hall sensor for biological applications
Authors: Lee Wonhyun , Joo Sungjung , Kim Sun Ung , Rhie Kungwon , Hong Jinki , Shin Kyung-Ho , Kim Ki Hyun
Published: April 2009

Micro-Hall sensors have been fabricated, and various numbers of micron-size magnetic beads have been placed within the sensor area. The Hall resistances measured at room temperature are found to be proportional to the number of the beads, and are in good agreement with the numerically simulated results presented in this study. Our sensors are designed to measure the number of beads between zero and full-scale signals for a given number range of interest. The effects of miniaturizing the beads and sensors to nanoscale are also discussed.
High Q-factor metasurfaces based on miniaturized asymmetric single split resonators
Authors: Al-Naib Ibraheem A. I. , Jansen Christian , Koch Martin
Published: April 2009

We introduce asymmetric single split rectangular resonators as bandstop metasurfaces, which exhibit very high Q-factors in combination with low passband losses and a small electrical footprint. The effect of the degree of asymmetry on the frequency response is thoroughly studied. Furthermore, complementary structures, which feature a bandpass behavior, were derived by applying Babinet’s principle and investigated with regards to their transmission characteristics. In future, asymmetric single split rectangular resonators could provide efficient unit cells for frequency selective surface devices, such as thin-film sensors or high performance filters.
Electrical properties of N-polar AlGaN/GaN high electron mobility transistors grown on SiC by metalorganic chemical vapor deposition
Authors: Brown David F. , Chu Rongming , Keller Stacia , DenBaars Steven P. , Mishra Umesh K.
Published: April 2009

N-polar high electron mobility transistors (HEMTs) were fabricated from GaN/AlGaN/GaN heterostructures grown on n-type vicinal C-face SiC substrates by metalorganic chemical vapor deposition. The heterostructures had a sheet charge density and mobility of 6.6×1012 cm−2 and 1370 cm2 V−1 s−1, respectively. HEMTs with a gate length of 0.7 μm had a peak transconductance of 135 mS/mm, a peak drain current of 0.65 A/mm, and a three-terminal breakdown voltage greater than 150 V. At a drain bias of 20 V, the current-gain and power-gain cutoff frequencies with the pad capacitances de-embedded were 17 and 33 GHz, respectively.
Modulation of bovine sperm signalling pathways: correlation between intracellular parameters and sperm capacitation and acrosome exocytosis
Authors: Pons-Rejraji Hanae , Bailey Janice L. , Leclerc Pierre
Published: April 2009

In the present study, the viability, intracellular pH (pHi), cAMP ([cAMP]i), calcium concentration and protein phosphotyrosine content were evaluated in relation to the acrosomal and capacitation status of freshly ejaculated bull spermatozoa. These parameters were evaluated before and after incubation with the capacitation inducer heparin, the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX), the phosphotyrosyl-protein phosphatase inhibitors phenylarsine oxide (PAO) and sodium orthovanadate, and hydrogen peroxide. The results obtained were integrated to address the physiological interactions between the different signalling events affecting sperm capacitation and acrosome reaction. As expected, heparin promoted the expression of the ‘B’ pattern of chlortetracycline binding, increased pHi, [cAMP]i and the phosphotyrosine content of sperm proteins. The effects of heparin were enhanced by IBMX. Both PAO and sodium orthovanadate stimulated protein phosphotyrosine content and acrosomal exocytosis, although only PAO affected pH, Ca2+ and cAMP levels. Intracellular pH was increased while both Ca2+ and [cAMP]i were decreased. Physiological concentrations of H2O2 increased [cAMP]i and promoted acrosomal exocytosis. A significant positive correlation was found between sperm capacitation, protein phosphotyrosine content and stored Ca2+ concentration, whereas the acrosome reaction was correlated with pHi and Ca2+ concentration. This study presents the first global analysis of the major elements individually described during sperm capacitation and acrosome reaction signalling pathways, supported by statistical correlations.
Plant protein hydrolysates (plant peptones) as substitutes for animal proteins in embryo culture medium
Authors: George F. , Kerschen D. , Van Nuffel A. , Rees J. F. , Donnay I.
Published: April 2009

The aim of the present study was to improve the sanitary quality of in vitro-produced bovine embryos by using plant protein hydrolysates (plant peptones) as substitutes for animal proteins. Peptones were compared with bovine serum albumin (BSA) as the protein source in synthetic oviduct fluid medium and the quality of the resulting embryos was determined. Two batches of peptones (wheat and cotton) were selected on the basis of their anti-oxidant properties. When added to the culture medium, both peptones (at 0.56 mg mL–1 for cotton peptone and at 0.18 mg mL–1 for wheat peptone) led to similar developmental and hatching rates compared with 4 mg mL–1 BSA and embryos were equally resistant to freezing and able to elongate after transfer. Surprisingly, a significant decrease in reduced glutathione (GSH) content was observed when embryos were produced with plant peptone instead of BSA. Supplementation of the culture medium with precursors of GSH (cysteine and β-mercaptoethanol) significantly increased the GSH content. A shift of the sex ratio towards male embryos was seen for Day 8 embryos cultured with wheat peptone, whereas no shift was observed for embryos cultured in the presence of BSA or polyvinylpyrrolidone. In conclusion, culture with plant peptones enables embryos to be obtained at a similar rate and of similar quality to that seen following the use of BSA. The use of the plant peptones increased the sanitary quality of the embryos and decreased the cost of embryo production.
Normal mammary gland growth and lactation capacity in pregnant relaxin-deficient mice
Authors: Parry Laura J. , Vodstrcil Lenka A. , Madden Anna , Amir Stephanie H. , Baldwin Katrina , Wlodek Mary E. , Nicholas Kevin R.
Published: April 2009

Pups born to mice with a targeted deletion of relaxin or its receptor (Rxfp1) die within 24 h postpartum. This has been attributed, in part, to abnormal mammary gland development in relaxin-mutant mice (Rln–/–). However, mammary development is normal in relaxin receptor-mutant (Rxfp1–/–) mice. The present study aimed to verify the mammary phenotypes in late pregnant and early lactating Rln–/– mice and to test the hypothesis that relaxin is involved in milk protein synthesis. Comparisons between late pregnant and early lactating wildtype (Rln+/+) and Rln–/– mice showed no differences in lobuloalveolar structure or ductal branching in the mammary gland. Mammary explants from Rln–/– mice also expressed β-casein and α-lactalbumin in response to lactogenic hormones at a similar level to Rln+/+ mice, implying normal milk protein synthesis. Pregnant Rln–/– mice infused with relaxin for 6 days gave birth to live pups without difficulty, and 96% of pups survived beyond 7 days. This is in contrast with the 100% pup mortality in saline-treated Rln–/– mice or 3-day relaxin-treated Rln–/– mice. Pups born to relaxin-treated Rln–/– dams weighed significantly less than Rln+/+ pups but had similar growth rates as their wildtype counterparts. In summary, relaxin is not critical for mammary gland development or β-casein and α-lactalbumin expression in late pregnant mice. In addition, Rln–/– dams did not need to be treated with relaxin postpartum for the pups to survive, suggesting that relaxin has no role in the maintenance of lactation in mice.
Exogenous transforming growth factor beta1 replacement and fertility in male Tgfb1 null mutant mice
Authors: McGrath Leanne J. , Ingman Wendy V. , Robker Rebecca L. , Robertson Sarah A.
Published: April 2009

Analysis of Tgfb1 null mutant mice has demonstrated that the cytokine transforming growth factor β1 (TGFB1) has essential non-redundant roles in fertility. The present study attempted to alleviate the infertility phenotype of Tgfb1 null mutant male mice by administration of exogenous TGFB1, either orally by colostrum feeding or subcutaneously by delivery of recombinant human latent TGFB1 (rhLTGFB1) via osmotic mini-pumps. Bovine colostrum and fresh unpasteurised bovine milk were found to be rich sources of TGFB1 and TGFB2; however, feeding Tgfb1 null mutant mice colostrum for 2 days failed to raise serum levels of TGFB1. Administration of rhLTGFB1 (~150 μg in total) over 14 days to Tgfb1 null mutant mice resulted in detectable TGFB1 in serum; however, mean levels remained 10-fold less than in Tgfb1 heterozygous mice. After 7 days and 14 days of rhLTGFB1 administration, serum testosterone, spontaneous non-contact erections and mating behaviour were assessed. Despite the increased serum TGFB1, administration of rhLTGFB1 to Tgfb1 null mutant mice failed to improve these fertility parameters. It is concluded that sustained restoration of circulating latent TGFB1 to levels approaching the normal physiological range does not rescue the infertility phenotype caused by TGFB1 deficiency. Reproductive function in male Tgfb1 null mutant mice may not respond to systemic TGFB1 supplementation due to a requirement for local sources of TGFB1 at the site of action in the reproductive tract, or perturbed development during the neonatal period or puberty such that adult reproductive function is permanently impaired.
Intracellular calcium activates TRPM2 and its alternative spliced isoforms
Authors: Du Jianyang , Xie Jia , Yue Lixia
Published: April 2009

Melastatin-related transient receptor potential channel 2 (TRPM2) is a Ca
2+
-permeable, nonselective cation channel that is involved in oxidative stress-induced cell death and inflammation processes. Although TRPM2 can be activated by ADP-ribose (ADPR) in vitro, it was unknown how TRPM2 is gated in vivo. Moreover, several alternative spliced isoforms of TRPM2 identified recently are insensitive to ADPR, and their gating mechanisms remain unclear. Here, we report that intracellular Ca
2+
([Ca
2+
]
i
) can activate TRPM2 as well as its spliced isoforms. We demonstrate that TRPM2 mutants with disrupted ADPR-binding sites can be activated readily by [Ca
2+
]
i
, indicating that [Ca
2+
]
i
gating of TRPM2 is independent of ADPR. The mechanism by which [Ca
2+
]
i
activates TRPM2 is via a calmodulin (CaM)-binding domain in the N terminus of TRPM2. Whereas Ca
2+
-mediated TRPM2 activation is independent of ADPR and ADPR-binding sites, both [Ca
2+
]
i
and the CaM-binding motif are required for ADPR-mediated TRPM2 gating. Importantly, we demonstrate that intracellular Ca
2+
release activates both recombinant and endogenous TRPM2 in intact cells. Moreover, receptor activation-induced Ca
2+
release is capable of activating TRPM2. These results indicate that [Ca
2+
]
i
is a key activator of TRPM2 and the only known activator of the spliced isoforms of TRPM2. Our findings suggest that [Ca
2+
]
i
-mediated activation of TRPM2 and its alternative spliced isoforms may represent a major gating mechanism in vivo, therefore conferring important physiological and pathological functions of TRPM2 and its spliced isoforms in response to elevation of [Ca
2+
]
i
.
Integration of evolutionary and desolvation energy analysis identifies functional sites in a plant immunity protein
Authors: Casasoli Manuela , Federici Luca , Spinelli Francesco , Di Matteo Adele , Vella Nicoletta , Scaloni Flavio , Fernandez-Recio Juan , Cervone Felice , De Lorenzo Giulia
Published: April 2009

Plant immune responses often depend on leucine-rich repeat receptors that recognize microbe-associated molecular patterns or pathogen-specific virulence proteins, either directly or indirectly. When the recognition is direct, a molecular arms race takes place where plant receptors continually and rapidly evolve in response to virulence factor evolution. A useful model system to study ligand-receptor coevolution dynamics at the protein level is represented by the interaction between pathogen-derived polygalacturonases (PGs) and plant polygalacturonase-inhibiting proteins (PGIPs). We have applied codon substitution models to
PGIP
sequences of different eudicotyledonous families to identify putative positively selected sites and then compared these sites with the propensity of protein surface residues to interact with protein partners, based on desolvation energy calculations. The 2 approaches remarkably correlated in pinpointing several residues in the concave face of the leucine-rich repeat domain. These residues were mutated into alanine and their effect on the recognition of several PGs was tested, leading to the identification of unique hotspots for the PGIP-PG interaction. The combined approach used in this work can be of general utility in cases where structural information about a pattern-recognition receptor or resistance-gene product is available.
Drawing digital pictures: An investigation of primary pupils’ representations of ICT and schools
Authors: Selwyn Neil , Boraschi Daniela , Özkula Suay Melisa
Published: April 2009

The relatively restricted nature of children's use of information and communications technologies (ICTs) inside the school setting has long been noted by researchers. With this in mind, this article offers a grounded analysis of drawings collected from 355 primary pupils (years three to six) from five English primary schools depicting desired future forms of school ICT provision. The article contends that the nature and content of these future orientated pictures reflect many of the tensions underlying children's current engagements with ICTs in school. Specifically the article discusses how the drawings offer valuable insights into the issues underlying pupils’ understandings of ICT and schools, not least: the restrictions of the school as organisation; the oppositional relationship between the ‘work’ of learning in school and the ‘play’ of using digital media at home; the unequal power relations that exist between pupils, schools and teachers. The article concludes that rather than accede to demands for free and unfettered use of game consoles and portable devices in the classroom, schools should instead concentrate on fostering informed dialogues with young people about the potential educational benefits of school ICT use.
Forecasting seasonal to interannual variability in extreme sea levels
Authors: Menendez Melisa , Mendez Fernando J. , Losada Inigo J.
Published: April 2009

Menendez, M., Mendez, F. J., and Losada, I. J. 2009. Forecasting seasonal to interannual variability in extreme sea levels. – ICES Journal of Marine Science, 66: 1490–1496. A statistical model to predict the probability of certain extreme sea levels occurring is presented. The model uses a time-dependent generalized extreme-value (GEV) distribution to fit monthly maxima series, and it is applied for a particular time-series record for the Atlantic Ocean (Newlyn, UK). The model permits the effects of seasonality, interannual variability, and secular trends to be identified and estimated in the probability distribution of extreme sea levels. These factors are parameterized as temporal functions (linear, quadratic, exponential, and periodic functions) or covariates (for instance, the North Atlantic Oscillation index), which automatically yield the best-fit model for the variability present in the data. A clear pattern of within-year variability and significant effects resulting from astronomical modulations (the nodal cycle and perigean tides) are detected. Modelling different time-scales helps to gain a better understanding of recent secular trends regarding extreme climate events, and it allows predictions to be made (for example, up to 2020) about the probability of the future occurrence of a particular sea level.
Biological functions and therapeutic use of erythropoiesis‐stimulating agents: perplexities and perspectives
Authors: Merchionne Francesca , Dammacco Franco
Published: April 2009

Randomized clinical studies, carried out in patients with haematological malignancies and with solid tumours, have consistently demonstrated that treatment with recombinant human erythropoietin (Epo) increases haemoglobin levels, reduces blood transfusion requirements, and improves the quality of life. In addition, identification of erythropoietin receptor (EpoR) expression on many types of non‐erythroid and cancer cells has spurred an interest in the extra‐haematological activities of Epo itself and other erythropoiesis‐stimulating agents (ESAs). Epo and its derivatives have emerged as major tissue‐protective cytokines in ischaemic and degenerative damage of cardiovascular, neurological and renal diseases, while their angiogenetic and immunomodulatory properties indicate that their therapeutic potential may extend well beyond erythropoiesis alone. Both preclinical and clinical data, however, have suggested that they may contribute to tumour progression and prejudice survival when administered to anaemic cancer patients, though the results are equivocal and the assumed mechanisms by which tumour growth could be promoted are not fully understood. While these findings offer new perspectives, they nonetheless demand caution in the employment of ESAs. Further, well‐designed experimental and clinical studies are warranted.
Anti‐bacterial IgE in the antibody responses of house dust mite allergic children convalescent from asthma exacerbation
Authors: Hales B. J. , Martin A. C. , Pearce L. J. , Rueter K. , Zhang G. , Khoo S‐K , Hayden C. M. , Bizzintino J. , McMinn P. , Geelhoed G. C. , Lee W‐M , Goldblatt J. , Laing I. A. , LeSouëf P. N. , Thomas W. R.
Published: April 2009

Background
Atopic sensitization to the house dust mite (HDM) is associated with altered antibody responses to the nasopharyngeal colonizing bacterium Haemophilus influenzae and children admitted to the emergency department for asthma exacerbation have reduced IgG responses to HDM allergens.

Objective
To investigate anti‐bacterial and anti‐allergen antibody responses during convalescence from asthma exacerbation and differences found in exacerbations associated with and without viral infection.

Results
IgE antibodies to the P6 bacterial antigen increased in 60% of sera during convalescence and for many children achieved titres as high as IgE titres to allergens. In contrast IgE anti‐HDM titres declined during convalescence. The anti‐bacterial IgE titres were the same in subjects with and without virus infection while the anti‐HDM IgE declined more rapidly in virus‐infected subjects. IgG titres to the major HDM allergens showed no consistent increase and the overall IgG anti‐HDM titres even declined in subjects without a virus infection. Anti‐bacterial IgG antibodies in contrast to IgE did not change. Patients with frequent episodic or persistent asthma had similar IgE anti‐bacterial titres to patients with infrequent asthma during the acute phase, although they had reduced IgG titres to both the bacteria and the HDM.

Conclusions
During the period following an acute exacerbation of asthma there was a marked and specific increase in anti‐bacterial IgE compared with a reduced IgE response to HDM. This provides further support for the concept of T‐helper type 2 responses to bacterial antigens playing a role in asthma pathogenesis.
Hormonal determinants of bone turnover before and after attainment of peak bone mass
Authors: Walsh Jennifer S. , Henry Yvette M. , Fatayerji Diana , Eastell Richard
Published: April 2009

Introduction  Bone turnover decreases from adolescence into adulthood, but does not reach a nadir until the fourth decade. Biochemical markers of bone turnover reflect different processes before and after peak bone mass, so hormonal influences on bone turnover may differ before and after peak bone mass.

Objectives  To describe the changes in bone turnover and hormones relevant to bone metabolism from adolescence into adulthood, and to identify which hormones correlate with bone turnover before and after peak bone mass.

Design/participants  Two measurements of bone turnover markers and hormones were obtained 5–9 years apart in 116 healthy males and females recruited from secondary schools and general practices. Correlations were examined cross‐sectionally and longitudinally.

Results  Dehydroepiandrosterone sulphate (DHEAS) correlated negatively with bone turnover cross‐sectionally and longitudinally (r−0·59 to −0·69) in males and females under the age of 25 years. IGF‐1 correlated positively with aminoterminal propeptide of type I procollagen (PINP) cross‐sectionally and longitudinally (r 0·35) in women over the age of 25 years. After correction for change in BMI, there were significant longitudinal correlations between DHEAS and bone turnover in women under 25 years (r−0·62, −0·66) and IGF‐1 and PINP in women over 25 years (r 0·56).

Conclusions  We have described changes in bone turnover and hormones from adolescence into adulthood. Dehydroepiandrosterone sulphate correlates with bone turnover before peak bone mass which may represent a direct effect on bone metabolism or the role of dehydroepiandrosterone sulphate as a substrate for conversion to other sex steroids. IGF‐1 is correlated with aminoterminal propeptide of type I procollagen in women after peak bone mass, which may reflect an influence on cortical modelling.
Identification of steroid biosynthetic defects in genotype‐proven heterozygous individuals for 17α‐hydroxylase/17,20‐lyase deficiency
Authors: Qiao Jie , Chen Xia , Zuo Chun‐Lin , Gu Yan‐Yun , Liu Bing‐Li , Liang Jun , Lu Ying‐Li , Tang Jin‐Feng , Wu Yi‐Xin , Chen Ming‐Dao , Chen Jia‐Lun , Wu Wan‐Ling , Song Huai‐Dong
Published: April 2009

Objective  P450c17 deficiency (17α‐hydroxylase/17,20‐lyase deficiency, 17OHD) is a rare form of congenital adrenal hyperplasia caused by CYP17A1 gene mutations. The D487_F489 deletion in exon 8 and Y329fs in exon 6 are relatively frequent mutations of the CYP17A1 gene in China that completely abolish the enzyme activity of P450c17. However, little remains known about steroid biosynthetic functions in carriers with these mutations in a single allele of the CYP17A1 gene, who are assumed to have 50% P450c17 activity. We investigated adrenal steroidogenic function in genotype‐proven heterozygotes carrying such mutations in the CYP17A1 gene in vivo.

Patients and design  Eight patients and fourteen family members from five families with 17OHD were recruited. The mutations of the CYP17A1 gene in these individuals were screened by sequencing. The hormonal response to cosyntropin (ACTH) was evaluated in the 14 genotype‐proven carriers and 45 age‐ and gender‐matched normal controls.

Results  Fourteen carriers of the CYP17A1 mutation – seven with the D487_F489 deletion, six with Y329fs and one with H373L – were identified from the five families with 17OHD. Compared with normal controls, carriers showed lower basal and ACTH‐stimulated cortisol levels but higher ACTH‐stimulated corticosterone levels. The ratios of corticosterone to cortisol in the genotype‐proven heterozygotes were higher than those of the normal controls at the baseline and after cosyntropin stimulation. Similarly, the progesterone levels and the ratios of progesterone to 17‐hydroxyprogesterone in the male heterozygotes were also higher than those of the normal controls, both before and after ACTH stimulation.

Conclusion  Genotype‐proven carriers of the CYP17A1 mutation who lack apparent clinical symptoms exhibit decreased adrenal 17α‐hydroxylase activity and altered adrenal gland reserve for steroid biosynthesis.
Gender effects on cardiac valvular function in hyperprolactinaemic patients receiving cabergoline: a retrospective study
Authors: Nachtigall Lisa B. , Valassi Elena , Lo Janet , McCarty David , Passeri Jonathan , Biller Beverly M. K. , Miller Karen K. , Utz Andrea , Grinspoon Steven , Lawson Elizabeth A. , Klibanski Anne
Published: April 2009

Background  Ergot‐derived dopamine agonists are associated with increased risk of valvular dysfunction in Parkinson’s disease. The risk of valvular disease associated with lower doses of cabergoline used to treat prolactinomas remains controversial.

Objective  To determine whether there is an association of cabergoline and valvular function in patients with hyperprolactinaemia according to gender.

Design  Case‐record retrospective study.

Setting  Outpatient neuroendocrine clinical centre at a tertiary care hospital.

Study participants  One hundred patients (48 men and 52 women) with hyperprolactinaemia who had an echocardiogram while receiving cabergoline for at least 6 months.

Controls  One hundred controls (48 men and 52 women) selected from Massachusetts general hospital (MGH) database of echocardiograms without clinically significant findings, matched to patients for age, gender, body mass index (BMI) and hypertension.

Main outcome measure  Echocardiogram.

Results  There were no significant differences in valvular function in patients compared with controls. However, women patients had a higher prevalence of mild tricuspid regurgitation (TR) than female controls (15·4%vs. 1·9%, P = 0.03). Among men only, patients had more trace TR than controls (68·8%vs. 45·8%, P = 0.02). The mild valvular regurgitation in patients was not clinically significant and did not correlate with dose, duration or cumulative dose.

Conclusions  Overall cabergoline was not associated with valvulopathy. However, subdivided by gender, hyperprolactinaemic men and women had higher prevalence of trace or mild TR, respectively, compared with gender matched controls. There may be gender differences in valvular dysfunction associated with cabergoline. Longer term, larger studies are necessary to evaluate definitively an effect of cabergoline on valvular function in hyperprolactinaemic patients.
Should we evaluate for cardiovascular disease in patients with Cushing’s syndrome?
Authors: Fallo Francesco , Sonino Nicoletta
Published: April 2009

Current evidence indicates a strong association between Cushing’s syndrome, characterized by a cluster of systemic complications and increased cardiovascular risk. The biological link is cortisol overproduction, which influences various pathogenetic processes leading to cardiovascular damage, a main cause of increased mortality. Anthropometric and biochemical profile (including fasting glucose, lipids, potassium and coagulation parameters), clinical blood pressure measurement and electrocardiogram should be routinely carried out. Oral glucose tolerance test, 24‐h ambulatory blood pressure monitoring, echocardiography and carotid ultrasound are recommended for further evaluation. Search for cardiac and vascular damage, according to specialist’s advice, is mandatory in complicated hypertension or diabetes, as part of a comprehensive assessment. A combination of treatments directed against the aetiology of hypercortisolism and aimed at controlling cardiovascular risk factors, is required in this complex condition.
Barriers to TB care for rural‐to‐urban migrant TB patients in Shanghai: a qualitative study
Authors: Wei Xiaolin , Chen Jing , Chen Ping , Newell James N. , Li Hongdi , Sun Chenguang , Mei Jian , Walley John D.
Published: April 2009

Objective  To understand barriers to tuberculosis (TB) care among migrant TB patients in Shanghai after the introduction of the TB‐free treatment policy which has applied to migrants since 2003, and to provide policy recommendations to improve TB control in migrant populations in big cities.

Methods  In‐depth interviews were conducted with 34 migrant patients who registered on the Shanghai TB programme as new bacteria positive pulmonary TB cases. Patients were purposively selected across six districts of Shanghai to give a balance of gender and TB treatment phase.

Results  Financial constraints were reported as the biggest barriers to TB service among migrant patients. Many migrant patients experienced high medical costs both before and after their TB diagnosis. The government free treatment policy only covered a small fraction of patients’ total costs. However, respondents tended to stay in Shanghai for treatment because their families were in Shanghai, they were more confident with the quality of medical care there or they felt they could not earn cash at home. Migrant patients had a limited knowledge of TB and the free TB treatment policy, and reported being laid off from work or avoided after having TB.

Conclusions  Health system problems caused the biggest barrier to migrant patients’ access to TB care. The free treatment policy alone has little, if any, effect in reducing migrant patients’ financial stress: it is also essential to provide social welfare, including living subsidies, for poor migrant TB patients.
Relationship between renal resistance index and renal function in liver transplant recipients after cessation of calcineurin inhibitor
Authors: Eisenberger Ute , Sollinger Daniel , Stickel Felix , Burckhardt Beat , Frey Felix J.
Published: April 2009

Abstract:  End stage renal disease is a major complication after orthotopic liver transplantation (OLT). Vasoconstriction of renal arterial vessels because of calcineurin inhibitor (CNI) treatment plays a pivotal role in the development of renal insufficiency following OLT. Renal resistance can be measured non‐invasively by determining the resistance index (RI) of segmental arteries by color‐coded duplex ultrasonography, a measure with predictive value for future renal failure. Sixteen OLT patients on long‐term CNI therapy were recruited prospectively and randomly assigned either to receive the m‐TOR inhibitor sirolimus (SRL) or to continue on CNI treatment, and were followed for one yr. Serum creatinine (crea) declined after conversion to SRL, whereas it tended to increase in patients remaining on CNI (meanΔ crea SRL: −27, −18, −18, −15 μmol/L; meanΔ crea CNI: 4, 5, 8, 11 μmol/L at 1, 3, 6, 12 months, p = 0.02). RI improved after switching to SRL and was lower on SRL than on CNI (meanΔRI SRL: −0.04, −0.04, −0.03, −0.03; meanΔRI CNI: −0.006, 0.004, −0.007, −0.01 after 1, 3, 6, 12 months, p = 0.016). Individual changes of RI correlated significantly with individual changes of crea (r = 0.54, p < 0.001). Conversion from CNI to SRL can ameliorate renal function accompanied by a reduction of intrarenal RI after OLT.