bluuebunny/crossref_metadata_2025 huggingface dataset:
Third-codon transversion rate-based Nymphaea basal angiosperm phylogeny -- concordance with developmental evidence
Authors: Yang Xiaohan , Tuskan Gerald , Tschaplinski Timothy , Cheng Zong-Ming
Published: July 2007

Flowering plants (angiosperms) appeared on Earth rather suddenly approximately 130 million years ago and underwent a massive expansion in the subsequent 10-12 million years. Current molecular phylogenies have predominantly identified Amborella, followed by Nymphaea (water lilies) or Amborella plus Nymphaea, in the ANITA clade (Amborella, Nymphaeales, Illiciaceae, Trimeniaceae and Austrobaileyaceae) as the earliest angiosperm. However, developmental studies suggest that the earliest angiosperm had a 4-cell/4-nucleus female gametophyte and a diploid endosperm represented by Nymphaea, suggesting that Amborella, having an 8-cell/9-nucleus female gametophyte and a triploid endosperm, cannot be representative of the basal angiosperm. This evolution-development discordance is possibly caused by erroneous inference based on phylogenetic signals with low neutrality and/or high saturation. Here we show that the 3rd codon transversion (P3Tv), with high neutrality and low saturation, is a robust high-resolution phylogenetic signal for such divergences and that the P3Tv-based land plant phylogeny cautiously identifies Nymphaea, followed by Amborella, as the most basal among the angiosperm species examined in this study. This P3Tv-based phylogeny contributes insights to the origin of angiosperms with concordance to fossil and stomata development evidence.
Pharmacological activators of AMP‐activated protein kinase have different effects on Na+ transport processes across human lung epithelial cells
Authors: Woollhead A M , Sivagnanasundaram J , Kalsi K K , Pucovsky V , Pellatt L J , Scott J W , Mustard K J , Hardie D G , Baines D L
Published: July 2007

Background and purpose:

AMP‐activated protein kinase (AMPK) is activated by metformin, phenformin, and the AMP mimetic, 5‐aminoimidazole‐4‐carboxamide‐1‐β‐D‐ribofuranoside (AICAR). We have completed an extensive study of the pharmacological effects of these drugs on AMPK activation, adenine nucleotide concentration, transepithelial amiloride‐sensitive (Iamiloride) and ouabain‐sensitive basolateral (Iouabain) short circuit current in H441 lung epithelial cells.

Experimental approach:

H441 cells were grown on permeable filters at air interface. Iamiloride, Iouabain and transepithelial resistance were measured in Ussing chambers. AMPK activity was measured as the amount of radiolabelled phosphate transferred to the SAMS peptide. Adenine nucleotide concentration was analysed by reverse phase HPLC and NAD(P)H autofluorescence was measured using confocal microscopy.

Key results:

Phenformin, AICAR and metformin increased AMPK (α1) activity and decreased Iamiloride. The AMPK inhibitor Compound C prevented the action of metformin and AICAR but not phenformin. Phenformin and AICAR decreased Iouabain across H441 monolayers and decreased monolayer resistance. The decrease in Iamiloride was closely related to Iouabain with phenformin, but not in AICAR treated monolayers. Metformin and phenformin increased the cellular AMP:ATP ratio but only phenformin and AICAR decreased cellular ATP.

Conclusions and implications:

Activation of α1‐AMPK is associated with inhibition of apical amiloride‐sensitive Na+ channels (ENaC), which has important implications for the clinical use of metformin. Additional pharmacological effects evoked by AICAR and phenformin on Iouabain, with potential secondary effects on apical Na+ conductance, ENaC activity and monolayer resistance, have important consequences for their use as pharmacological activators of AMPK in cell systems where Na+K+ATPase is an important component.

British Journal of Pharmacology (2007) 151, 1204–1215; doi:10.1038/sj.bjp.0707343
High‐throughput microscopy must re‐invent the microscope rather than speed up its functions
Authors: Oheim M
Published: July 2007

Knowledge gained from the revolutions in genomics and proteomics has helped to identify many of the key molecules involved in cellular signalling. Researchers, both in academia and in the pharmaceutical industry, now screen, at a sub‐cellular level, where and when these proteins interact. Fluorescence imaging and molecular labelling combine to provide a powerful tool for real‐time functional biochemistry with molecular resolution. However, they traditionally have been work‐intensive, required trained personnel, and suffered from low through‐put due to sample preparation, loading and handling. The need for speeding up microscopy is apparent from the tremendous complexity of cellular signalling pathways, the inherent biological variability, as well as the possibility that the same molecule plays different roles in different sub‐cellular compartments. Research institutes and companies have teamed up to develop imaging cytometers of ever‐increasing complexity. However, to truly go high‐speed, sub‐cellular imaging must free itself from the rigid framework of current microscopes.

British Journal of Pharmacology (2007) 152, 1–4; doi:10.1038/sj.bjp.0707348
Ginsenoside Rb1 inhibits tube‐like structure formation of endothelial cells by regulating pigment epithelium‐derived factor through the oestrogen β receptor
Authors: Leung K W , Cheung L W T , Pon Y L , Wong R N S , Mak N K , Fan T‐PD , Au S C L , Tombran‐Tink J , Wong A S T
Published: July 2007

Background and purpose:

Angiogenesis is a crucial step in tumour growth and metastasis. Ginsenoside‐Rb1 (Rb1), the major active constituent of ginseng, potently inhibits angiogenesis in vivo and in vitro. However, the underlying mechanism remains unknown. We hypothesized that the potent anti‐angiogenic protein, pigment epithelium‐derived factor (PEDF), is involved in regulating the anti‐angiogenic effects of Rb1.

Experimental approaches:

Rb1‐induced PEDF was determined by real‐time PCR and western blot analysis. The anti‐angiogenic effects of Rb1 were demonstrated using endothelial cell tube formation assay. Competitive ligand‐binding and reporter gene assays were employed to indicate the interaction between Rb1 and the oestrogen receptor (ER).

Key results:

Rb1 significantly increased the transcription, protein expression and secretion of PEDF. Targeted inhibition of PEDF completely prevented Rb1‐induced inhibition of endothelial tube formation, suggesting that the anti‐angiogenic effect of Rb1 was PEDF specific. Interestingly, the activation of PEDF occurred via a genomic pathway of ERβ. Competitive ligand‐binding assays indicated that Rb1 is a specific agonist of ERβ, but not ERα. Rb1 effectively recruited transcriptional activators and activated an oestrogen‐responsive reporter gene. Furthermore, Rb1‐mediated PEDF activation and the subsequent inhibition of tube formation were blocked by the ER antagonist ICI 182,780 or transfection of ERβ siRNA, indicating ERβ dependence.

Conclusions and implications:

Here we show for the first time that the Rb1 suppressed the formation of endothelial tube‐like structures through modulation of PEDF via ERβ. These findings demonstrate a novel mechanism of the action of this ginsenoside that may have value in anti‐cancer and anti‐angiogenesis therapy.

British Journal of Pharmacology (2007) 152, 207–215; doi:10.1038/sj.bjp.0707359
Neuroprotective and anticonvulsant effects of EGIS‐8332, a non‐competitive AMPA receptor antagonist, in a range of animal models
Authors: Gigler G , Móricz K , ágoston M , Simó A , Albert M , Benedek A , Kapus G , Kertész S , Vegh M , Barkóczy J , Markó B , Szabó G , Matucz É , Gacsályi I , Lévay G , Hársing L G , Szénási G
Published: July 2007

Background and purpose:

Blockade of AMPA (α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid) receptors is a good treatment option for a variety of central nervous system disorders. The present study evaluated the neuroprotective and anticonvulsant effects of EGIS‐8332, a non‐competitive AMPA receptor antagonist, as a potential drug candidate.

Experimental approach:

AMPA antagonist effects of EGIS‐8332 were measured using patch‐clamp techniques. Neuroprotective and anticonvulsant effects of EGIS‐8332 were evaluated in various experimental models, relative to those of GYKI 53405.

Key results:

EGIS‐8332 inhibited AMPA currents in rat cerebellar Purkinje cells and inhibited the AMPA‐ and quisqualate‐induced excitotoxicity in primary cultures of telencephalon neurons (IC50=5.1‐9.0 μM),in vitro. Good anticonvulsant actions were obtained in maximal electroshock‐, sound‐ and chemically‐induced seizures (range of ED50=1.4‐14.0 mg kg−1i.p.) in mice. Four days after transient global cerebral ischaemia, EGIS‐8332 decreased neuronal loss in the hippocampal CA1 area in gerbils and rats. EGIS‐8332 dose‐dependently reduced cerebral infarct size after permanent middle cerebral artery occlusion in mice and rats (minimum effective dose=3 mg kg−1i.p.). Side effects of EGIS‐8332 emerged much above its pharmacologically active doses. A tendency for better efficacy of GYKI 53405 than that of EGIS‐8332 was observed in anticonvulsant tests that reached statistical significance in few cases, while the contrary was perceived in cerebral ischaemia tests.

Conclusions and implications:

EGIS‐8332 seems suitable for further development for the treatment of epilepsy, ischaemia and stroke based on its efficacy in a variety of experimental disease models, and on its low side effect potential.

British Journal of Pharmacology(2007)152, 151–160; doi:10.1038/sj.bjp.0707362
α1‐Adrenoceptors are required for normal male sexual function
Authors: Sanbe A , Tanaka Y , Fujiwara Y , Tsumura H , Yamauchi J , Cotecchia S , Koike K , Tsujimoto G , Tanoue A
Published: July 2007

Background and purpose:

α1‐Adrenoceptor antagonists are extensively used in the treatment of hypertension and lower urinary tract symptoms associated with benign prostatic hyperplasia. Among the side effects, ejaculatory dysfunction occurs more frequently with drugs that are relatively selective for α1A‐adrenoceptors compared with other drugs of this class. This suggests that α1A‐adrenoceptors may contribute to ejaculation. However, this has not been studied at the molecular level.

Experimental approach:

The physiological contribution of each α1‐adrenoceptor subtype was characterized using α1‐adrenoceptor subtype‐selective knockout (KO) mice (α1A‐, α1B‐ and α1D‐AR KO mice) since the subtype‐specific drugs available are only moderately selective. We analysed the role of α1‐adrenoceptors in the blood pressure and vascular response as well as ejaculation by determining these variables in α1‐adrenoceptor subtype‐selective KO mice and in mice with all their α1‐adrenoceptor subtypes deleted (α1‐AR triple‐KO mice).

Key results:

The pregnancy rate was reduced by 50% in α1A‐adrenoceptor KO mice, and this reduction was dramatically enhanced in α1‐adrenoceptor triple‐KO mice. Contractile tension of the vas deferens in response to noradrenaline was markedly decreased in α1A‐adrenoceptor KO mice, and this contraction was completely abolished in α1‐adrenoceptor triple‐KO mice. This attenuation of contractility was also observed in the electrically stimulated vas deferens.

Conclusions and implications:

These results demonstrate that α1‐adrenoceptors, particularly α1A‐adrenoceptors, are required for normal contractility of the vas deferens and consequent sperm ejaculation as well as having a function in fertility.

British Journal of Pharmacology (2007) 152, 332–340; doi:10.1038/sj.bjp.0707366; published online 2 July 2007
The exosome and RNA quality control in the nucleus
Authors: Vanacova Stepanka , Stefl Richard
Published: July 2007

To control the quality of RNA biogenesis in the nucleus, cells use sophisticated molecular machines. These machines recognize and degrade not only RNA trimmings—the leftovers of RNA processing—but also incorrectly processed RNAs that contain defects. By using this mechanism, cells ensure that only high‐quality RNAs are engaged in protein synthesis and other cellular processes. The exosome—a complex of several exoribonucleolytic and RNA‐binding proteins—is the central 3′‐end RNA degradation and processing factor in this surveillance apparatus. The exosome operates with auxiliary factors that stimulate its activity and recruit its RNA substrates in the crowded cellular environment. In this review, we discuss recent structural and functional data related to the nuclear quality‐control apparatus, including the long‐awaited structure of the human exosome and its activity.
Normative values, reliability and sample size estimates in heart rate variability
Authors: Sandercock Gavin
Published: July 2007

HRV (heart rate variability) is a non-invasive maker of cardiac autonomic modulation utilized in many hundreds of scientific studies each year. The reliability of heart rate variability has been frequently investigated yet remains poorly quantified. Assessing the reliability of a measure that assesses dynamic physiological processes and shows large between- and within-subject variation is a complex task. In this issue of Clinical Science, Pinna and co-workers provide excellent insight into the test–retest reliability of commonly used HRV indices and put the values obtained into context by comparing them with levels of between-subject variation and by producing sample size estimates.
The Genus Clusia L.: Molecular Evidence for Independent Evolution of Photosynthetic Flexibility
Authors: Vaasen A. , Begerow D. , Lüttge U. , Hampp R.
Published: July 2007

Abstract: Members of the Clusiaceae genus Clusia (tropical trees and shrubs) belong to the small group of dicotyledonous trees which are able to perform crassulacean acid metabolism (CAM). Most of the species are able to switch between C3 and CAM modes of photosynthesis and only a few are restricted to either C3 or CAM. In order to discover possible phylogenetic relationships with regard to the mode of photosynthesis, we investigated 17 species of the genus Clusia, and one species each of the Clusiaceae genera Oedematopus and Hypericum on the basis of internal transcribed spacer (ITS) sequences between the 18S and 26S coding regions of nuclear ribosomal DNA. Little length variation was detected in the ITS region of Clusia species. ITS1 sequences ranged from 255 to 260 bp and ITS2 sequences from 208 to 210 bp. Neighbour‐joining and parsimony analyses of these sequences resulted in considerable differences in cluster formation when compared to a classification based on morphological characteristics. The molecular data also give no indication of a group‐specific evolution of modes of photosynthesis, i.e., C3 and CAM. We thus conclude that CAM has evolved independently several times within the genus Clusia.
Photosynthetic Performance and Pigment Composition of Leaves from two Tropical Species is Determined by Light Quality
Authors: Ramalho J. C. , Marques N. C. , Semedo J. N. , Matos M. C. , Quartin V. L.
Published: July 2007

Abstract: A suitable light quantity and quality is essential for optimal photosynthetic metabolism. Using combinations of three lamp types, the impact of the quality of artificial light conditions on the photosynthetic apparatus of leaves developed in growth chambers was analysed. The VIALOX‐Planta lamps are quite poor outside the green to orange (520 ‐ 620 nm) wavelength range, while the HQI‐BT lamps present a more uniform spectral intensity between 425 and 650 nm (blue to red). The halogen lamps are particularly rich in the red and far red range of the electromagnetic spectra. The lamps also differ in the red: far red ratio, which were 3.07 (VIALOX), 2.06 (HQI‐BT) and 1.12 (halogen). Clear positive effects were detected in most of the photosynthetic parameters in relation to light quality, both at stomatal and mesophyll levels. Despite some species‐dependent sensitivity to blue and red/far red wavelengths, observed among the studied parameters, the best photosynthetic performances of the test plants (Packyrhizus ahipa and Piatã, a hybrid of Coffea dewevrei×Coffea arabica) were obtained almost always with the reinforcement of blue (HQI‐BT lamps), red and far red (halogen lamps) wavelengths and with a red: far red ratio closer to that observed in nature. This suggests the involvement of more than one photoreceptor family in photosynthetic performance. Under such light conditions, increases in net photosynthesis and stomatal conductance were observed and, despite the moderate effects on photosynthetic capacity, strong effects were observed in the capture and transfer of light energy in the antennae pigments, photochemical efficiency of photosystem II and electron transport. This was related to the striking quantitative and qualitative impacts observed on total chlorophylls and carotenoids, which reached, in some cases, increases of 100 and 200 %, respectively. Among carotenoids, increases as high as 9‐fold for α‐carotene were observed (P. ahipa), with chlorophyll (a/b), total (chlorophyll/carotenoid) and carotene (α/β) ratios also strongly affected. This would have affected the structure and stability of photosynthetic membranes which, in turn, affected photosynthetic‐related processes (e.g., antennae pigments, photosystem II and electron transport efficiencies). This was particularly clear in the HQI + halogen treatment. The results unequivocally show that light quality could remain a clear limiting factor for leaf/plant development under artificial light conditions, which could be overcome using more than one lamp type, with complementary emission spectra.
Ab initio molecular orbital study of ground and low-lying electronic states of CoCN
Authors: Hirano Tsuneo , Okuda Rei , Nagashima Umpei , Jensen Per
Published: July 2007

The ground and low-lying excited states of CoCN have been studied by ab initio multireference single and double excitation configuration interaction (MR-SDCI) calculations with Davidson’s correction Q and Cowan-Griffin’s relativistic corrections. The electronic ground state of CoCN is Φi3 and the equilibrium geometry is linear with bond lengths of re(Co–C)=1.8540Å and re(C–N)=1.1677Å, substantially different from the experimentally derived values of r0(Co–C)=1.8827(7)Å and r0(C–N)=1.1313(10)Å. The first excited state is Δi3, separated from the ground state by 727cm−1. Larger dynamical electron correlation energy for the low-spin Φ3 state than for the high-spin Φ5 state makes the Φ3 state to be the ground state, which is discussed in terms of the differences in natural orbitals. A new spin-orbit interaction scheme between the X̃Φi3 and 1Δi3 states is proposed.
A conceptual model of the diffuse transmittance of lamellar diffraction gratings on solar cells
Authors: Catchpole K. R.
Published: July 2007

Diffraction gratings are effective ways of increasing the light absorption of solar cells and the light extraction of light-emitting diodes. In this paper, we show that simplified modal analysis can be used as a conceptual model for understanding the behavior of the diffuse transmittance of lamellar diffraction gratings on infinite substrates. We use simplified modal analysis to predict the optimum values of period and height for the gratings, and achieve excellent agreement with rigorous coupled wave analysis. Furthermore, we show that for thin film solar cells with front surface gratings and flat rear reflectors, modal analysis can be used to predict the optimum parameters for maximum light trapping.
Numerical integration techniques for curved-element discretizations of molecule-solvent interfaces
Authors: Bardhan Jaydeep P. , Altman Michael D. , Willis David J. , Lippow Shaun M. , Tidor Bruce , White Jacob K.
Published: July 2007

Surface formulations of biophysical modeling problems offer attractive theoretical and computational properties. Numerical simulations based on these formulations usually begin with discretization of the surface under consideration; often, the surface is curved, possessing complicated structure and possibly singularities. Numerical simulations commonly are based on approximate, rather than exact, discretizations of these surfaces. To assess the strength of the dependence of simulation accuracy on the fidelity of surface representation, here methods were developed to model several important surface formulations using exact surface discretizations. Following and refining Zauhar’s work [J. Comput.-Aided Mol. Des. 9, 149 (1995)], two classes of curved elements were defined that can exactly discretize the van der Waals, solvent-accessible, and solvent-excluded (molecular) surfaces. Numerical integration techniques are presented that can accurately evaluate nonsingular and singular integrals over these curved surfaces. After validating the exactness of the surface discretizations and demonstrating the correctness of the presented integration methods, a set of calculations are presented that compare the accuracy of approximate, planar-triangle-based discretizations and exact, curved-element-based simulations of surface-generalized-Born (sGB), surface-continuum van der Waals (scvdW), and boundary-element method (BEM) electrostatics problems. Results demonstrate that continuum electrostatic calculations with BEM using curved elements, piecewise-constant basis functions, and centroid collocation are nearly ten times more accurate than planar-triangle BEM for basis sets of comparable size. The sGB and scvdW calculations give exceptional accuracy even for the coarsest obtainable discretized surfaces. The extra accuracy is attributed to the exact representation of the solute-solvent interface; in contrast, commonly used planar-triangle discretizations can only offer improved approximations with increasing discretization and associated increases in computational resources. The results clearly demonstrate that the methods for approximate integration on an exact geometry are far more accurate than exact integration on an approximate geometry. A MATLAB implementation of the presented integration methods and sample data files containing curved-element discretizations of several small molecules are available online as supplemental material.
Space-time contours to treat intense field-dressed molecular states. I. Theory
Authors: Sarkar Biplab , Adhikari Satrajit , Baer Michael
Published: July 2007

A molecular system exposed to an intense external field is considered. The strength of the field is measured by the number L of electronic states that become populated during this process. In the present article the authors discuss a rigorous way, based on the recently introduced space-time contours [R. Baer, et al., J. Chem. Phys. 119, 6998 (2003)], to form N coupled Schrödinger equations where N<L, which maintains the effects due to the remaining (L−N) populated states. It is shown that whereas the size of L is unlimited, the main requirement concerning N is that the original group of N field-free states forms a Hilbert subspace in the spatial region of interest. From previous studies it is known that a group of states forms a Hilbert subspace if and only if the corresponding topological D matrix is diagonal [M. Baer, et al., Farad, Discuss 127, 337 (2004)].
New results from the contact theorem for the charge profile for symmetric electrolytes
Authors: Holovko M. , Badiali J. P. , di Caprio D.
Published: July 2007

In this paper the contact value of the charge profile at a charged interface is presented as the sum of the normal component of the Maxwell electrostatic tensor and a new electrostatic property defined by the integral from the product of the gradient of the electrical potential and the singlet distribution function of coions (ions with sign of the charge equal to that of the interface). On physical arguments, it is conjectured that this new property is a monotonic function of the electrical charge at the wall and is limited by the bulk electrolyte pressure for large electrical charges at the wall. Using the contact theorems for the density and the charge profiles, the exact expressions for the contact values of the profiles of coions and counterions are derived and some related general properties are discussed.
Ultrahigh birefringence of elliptic core fibers with irregular air holes
Authors: Kim Soan , Kee Chul-Sik , Lee Jongmin , Jung Yongmin , Choi Hyoung-Gyu , Oh Kyunghwan
Published: July 2007

We have investigated experimentally and theoretically the birefringence of the elliptic core fiber with irregular air holes. The wavelength dependence of the beat length and the birefringence was measured by the wavelength scanning method. The fiber exhibits ultrahigh birefringence of 1.12×10−2 at 1550 nm. We also calculated the modal birefringence of the fundamental modes in the fiber by using the plane wave expansion method. The calculated birefringence is in excellent agreement with the measured one.
Compact x-ray microtomography system for element mapping and absorption imaging
Authors: Feldkamp J. M. , Schroer C. G. , Patommel J. , Lengeler B. , Günzler T. F. , Schweitzer M. , Stenzel C. , Dieckmann M. , Schroeder W. H.
Published: July 2007

We have designed and built a compact x-ray microtomography system to perform element mapping and absorption imaging by exploiting scanning fluorescence tomography and full-field transmission microtomography, respectively. It is based on a low power microfocus tube and is potentially appropriate for x-ray diagnostics in space. Full-field transmission tomography yields the three-dimensional inner structure of an object. Fluorescence microtomography provides the element distribution on a virtual section through the sample. Both techniques can be combined for appropriate samples. Microradiography as well as fluorescence mapping are also possible. For fluorescence microtomography a small and intensive microbeam is required. It is generated using a polycapillary optic. Operating the microfocus tube with a molybdenum target at 12W, a microbeam with a full width at half maximum lateral extension of 16μm and a flux of about 108photons∕s is generated. As an example of application, this beam is used to determine the element distribution inside dried plant samples. For full-field scanning tomography, the x-ray optic is removed and the sample is imaged in magnifying projection onto a two-dimensional position sensitive detector. Depending on the sample size, a spatial resolution down to about 10μm is possible in this mode. The method is demonstrated by three-dimensional imaging of a rat humerus.
Where does the spin reside in ferromagnetic Cu-doped ZnO?
Authors: Keavney D. J. , Buchholz D. B. , Ma Q. , Chang R. P. H.
Published: July 2007

The authors report a soft x-ray absorption spectroscopy and magnetic circular dichroism study of the ferromagnetism in pulsed-laser-deposited Cu-doped ZnO thin films, which display robust room-temperature ferromagnetic signatures using bulk magnetization probes. In this work, the authors probe the spin asymmetries in the Cu 3d, O 2p, and Zn 3d states individually. They find a paramagnetic component originating from the Cu 3d, and no magnetic signal in the O or Zn. They find no dichroic signal consistent with ferromagnetism originating from any of these states.
Resistance switching in the metal deficient-type oxides: NiO and CoO
Authors: Shima Hisashi , Takano Fumiyoshi , Akinaga Hiro , Tamai Yukio , Inoue Isao H. , Takagi Hide
Published: July 2007

The resistance switching properties in Pt∕Ni–O∕Pt and Pt∕Co–O∕Pt synthesized by the magnetron sputtering have been investigated. The oxygen partial pressure during sputtering and the post-thermal process are crucial to forming of the trilayer. By investigating x-ray photoemission spectroscopy spectra, the increase of initial resistance in Ni–O was caused by the variation of the stoichiometry, while that in the Co–O was accompanied by the phase transformation between CoO and Co3O4. The resistance switching in Pt∕Co–O∕Pt and Pt∕Ni–O∕Pt exhibits the analogous electrode area and temperature dependences. As a result of the I-V measurements at the elevated temperature, the assistance of Joule heating in the reset process is implied.
Monolithic mass sensor fabricated using a conventional technology with attogram resolution in air conditions
Authors: Verd J. , Uranga A. , Abadal G. , Teva J. , Torres F. , Pérez-Murano F. , Fraxedas J. , Esteve J. , Barniol N.
Published: July 2007

Monolithic mass sensors for ultrasensitive mass detection in air conditions have been fabricated using a conventional 0.35μm complementary metal-oxide-semiconductor (CMOS) process. The mass sensors are based on electrostatically excited submicrometer scale cantilevers integrated with CMOS electronics. The devices have been calibrated obtaining an experimental sensitivity of 6×10−11g∕cm2Hz equivalent to 0.9ag∕Hz for locally deposited mass. Results from time-resolved mass measurements are also presented. An evaluation of the mass resolution have been performed obtaining a value of 2.4×10−17g in air conditions, resulting in an improvement of these devices from previous works in terms of sensitivity, resolution, and fabrication process complexity.
Transition voltage of asymmetric H state to bend in pi cell
Authors: Sun Yubao , Jiang Li , Li Zaidong , Ma Hongmei , Zhang Zhidong
Published: July 2007

The dynamic behavior for the splay to bend transition of pi cell is investigated numerically in detail. When a pi cell has asymmetric pretilt angles, the initial splay configuration changes to asymmetric H state driven by a low voltage, then to bend configuration driven by a pulse voltage that is larger than a transition voltage. The author’s results show that the transition voltage decreases with the increasing pretilt angle, and increases with the increasing anchoring energy and surface viscosity. The transition time is less than 50ms which is much faster than that of other methods.
Mg acceptor level in InN epilayers probed by photoluminescence
Authors: Khan N. , Nepal N. , Sedhain A. , Lin J. Y. , Jiang H. X.
Published: July 2007

Mg-doped InN epilayers were grown on sapphire substrates by metal organic chemical vapor deposition. Effects of Mg concentration on the photoluminescence (PL) emission properties have been investigated. An emission line at ∼0.76eV, which was absent in undoped InN epilayers and was about 60meV below the band-to-band emission peak at ∼0.82eV, was observed to be the dominant emission in Mg-doped InN epilayers. The PL spectral peak position and the temperature dependent emission intensity corroborated each other and suggested that the Mg acceptor level in InN is about 60meV above the valance band maximum.
Influence of temperature and photoexcitation density on the quantum efficiency of defect emission in ZnO powders
Authors: Foreman J. V. , Everitt H. O. , Yang J. , Liu J.
Published: July 2007

The effect of laser excitation power density on the efficiency of intrinsic defect emission in ZnO powders was characterized by varying the laser irradiance over three orders of magnitude and monitoring changes in the samples’ photoluminescence. The external quantum efficiency of the visible wavelength, broadband defect photoluminescence was found to depend not only on laser irradiance but also on temperature and prior annealing conditions. This material system is potentially useful as an ultraviolet-photoexcited, white light phosphor under low-power excitation (<0.2W∕cm2) at room temperature and below.
Scalable fabrication of electrowetting displays with self-assembled oil dosing
Authors: Sun B. , Zhou K. , Lao Y. , Heikenfeld J. , Cheng W.
Published: July 2007

Scalable fabrication of electrowetting displays with self-assembled oil dosing is reported. Electrowetting pixel structures consisted of flexible substrate/electrode/hydrophobic dielectric/hydrophilic grid. 20 electrowetting display prototypes were constructed with four pixel sizes ranging from 300×900to50×150μm2 and with five grid thicknesses ranging from 16.2to3.3μm. Self-assembled oil dosing was achieved by dip coating the substrate through an oil film suspended on water. The oil films in pixels were geometrically flat. Operating voltage increased with pixel aspect ratio. Electrical capacitance and optical absorption calculations confirm that oil thickness is within ±5% of the hydrophilic grid height.
Enhancing the dot density in quantum dot infrared photodetectors via the incorporation of antimony
Authors: Aivaliotis P. , Wilson L. R. , Zibik E. A. , Cockburn J. W. , Steer M. J. , Liu H. Y.
Published: July 2007

The authors combine optical spectroscopic studies and infrared photodetector development to demonstrate the potential of antimony-mediated InAs quantum dot growth for the production of high performance dot-based devices. By depositing 1 ML of gallium antimonide prior to dot growth, the dot density is increased from ∼3×1010 for conventional InAs dots, to ∼6×1010cm−2. Detailed intra- and interband spectroscopic studies show no significant differences in the electron energy level configuration compared with standard InAs∕GaAs dots, while intraband absorption strength is increased. Furthermore, they have implemented this growth technique to produce a quantum dot infrared photodetector with a detectivity of ∼5×1010cmHz1∕2W−1 at 7.5μm (T=77K).
Whiskers of tantalum trisulfide twist in response to an electric field
Authors: Day Charles
Published: July 2007

A coherent electronic structure known as a charge-density wave is responsible for the twist. How the whiskers pick a rotation direction is a mystery.
China’s space science prepares for liftoff
Authors: Feder Toni
Published: July 2007

In its latest five-year plan, China backs an ambitious selection of space-science projects and encourages international collaborations.
The fundamental physical constants
Authors: Mohr Peter J. , Taylor Barry N. , Newell David B.
Published: July 2007

Incorporating recent data, a new set of recommended values of the basic constants and conversion factors of physics and chemistry has just been issued.
The case for extra dimensions
Authors: Randall Lisa
Published: July 2007

Spaces with more than three dimensions are consistent with known physics, can help solve a vexing problem in the standard model, and may soon be indirectly observed at the Large Hadron Collider.
Modes of Governing Municipal Waste
Authors: Bulkeley Harriet , Watson Matt , Hudson Ray
Published: July 2007

From recent debates on governance and governmentality, two key analytical imperatives arise: the need to engage simultaneously with the structures and processes of governing, and the need to recognise the plurality and multiplicity of governing sites and activities. In seeking to address these imperatives, we develop an analytical approach, the modes of governing approach, which engages with the rationalities, agencies, institutional relations, and technologies of governing that coalesce around particular objectives and entities to be governed. Drawing on the example of municipal waste management, we illustrate how this framework can illuminate the dynamic and multiple nature of governing, and outline the key modes of governing which currently shape the policy and practice of municipal waste.
Embodying Responsibility: Children's Health and Supermarket Initiatives
Authors: Colls Rachel , Evans Bethan
Published: July 2007

In this paper we interrogate the ways in which supermarkets ‘place’ responsibility for children's ‘healthy’ eating with parents and/or children, as set within the contemporary British public health concern with the prevalence of childhood obesity. We use British food retailers' corporate social responsibility (CSR) policies as a way of identifying specific relations of responsibility between supermarkets, parents, and children. We do this through focusing upon a critical interrogation of two supermarkets' children's ‘healthy’ eating initiatives; a supermarket own-brand range of children's ‘healthy’ food products; and a supermarket in-store ‘healthy’ food tour. The emergent geographies of embodied responsibility illustrate a deferral of responsibility from supermarkets to parents. This is problematic because it conversely excludes the possibilities for the child to be a consumer on the grounds that they are irresponsible and incapable of engaging with ‘healthy’ food. We suggest that this implied model of responsibility, which conceptualises responsibility as contained within the individual, is unhelpful because of its exclusivity and suggest that a collective notion of responsibility is necessary to understand fully the relations of responsibility that exist between bodies. This opens up possibilities for a more nuanced account of the ‘child’ consumer and the relationships that children have with ‘healthy’ food.
Environment and Planning B: Planning and Design as a Journal: The Interdisciplinarity of its Environment and the Citation Impact
Authors: Leydesdorff Loet
Published: July 2007

The citation impact of Environment and Planning B: Planning and Design can be visualized using its citation relations with journals in its environment as the links of a network. The size of the nodes is varied in correspondence to the relative citation impact in this environment. Additionally, one can correct for the effect of within-journal ‘self’-citations. The network can be partitioned and clustered using algorithms from social network analysis. After transposing the matrix in terms of rows and columns, the citing patterns can be mapped analogously. Citing patterns reflect the activity of the community of authors who publish in the journal, while being cited indicates reception. Environment and Planning B: Planning and Design is cited across the interface between the social sciences and the natural sciences, but its authors cite almost exclusively from the domain of the Social Science Citation Index.
The mitochondrial E3 ubiquitin ligase MARCH5 is required for Drp1 dependent mitochondrial division
Authors: Karbowski Mariusz , Neutzner Albert , Youle Richard J.
Published: July 2007

We identify a mitochondrial E3 ubiquitin ligase, MARCH5, as a critical regulator of mitochondrial fission. MARCH5 RING mutants and MARCH5 RNA interference induce an abnormal elongation and interconnection of mitochondria indicative of an inhibition of mitochondrial division. The aberrant mitochondrial phenotypes in MARCH5 RING mutant–expressing cells are reversed by ectopic expression of Drp1, but not another mitochondrial fission protein Fis1. Moreover, as indicated by abnormal clustering and mitochondrial accumulation of Drp1, as well as decreased cellular mobility of YFP-Drp1 in cells expressing MARCH5 RING mutants, MARCH5 activity regulates the subcellular trafficking of Drp1, likely by impacting the correct assembly at scission sites or the disassembly step of fission complexes. Loss of this activity may account for the observed mitochondrial division defects. Finally, MARCH5 RING mutants and endogenous Drp1, but not wild-type MARCH5 or Fis1, co-assemble into abnormally enlarged clusters in a Drp1 GTPase-dependent manner, suggesting molecular interactions among these proteins. Collectively, our data suggest a model in which mitochondrial division is regulated by a MARCH5 ubiquitin-dependent switch.
Loss of p53 promotes RhoA–ROCK-dependent cell migration and invasion in 3D matrices
Authors: Gadea Gilles , de Toledo Marion , Anguille Christelle , Roux Pierre
Published: July 2007

In addition to its role in controlling cell cycle progression, the tumor suppressor protein p53 can also affect other cellular functions such as cell migration. In this study, we show that p53 deficiency in mouse embryonic fibroblasts cultured in three-dimensional matrices induces a switch from an elongated spindle morphology to a markedly spherical and flexible one associated with highly dynamic membrane blebs. These rounded, motile cells exhibit amoeboid-like movement and have considerably increased invasive properties. The morphological transition requires the RhoA–ROCK (Rho-associated coil-containing protein kinase) pathway and is prevented by RhoE. A similar p53-mediated transition is observed in melanoma A375P cancer cells. Our data suggest that genetic alterations of p53 in tumors are sufficient to promote motility and invasion, thereby contributing to metastasis.
BMP gradients steer nerve growth cones by a balancing act of LIM kinase and Slingshot phosphatase on ADF/cofilin
Authors: Wen Zhexing , Han Liang , Bamburg James R. , Shim Sangwoo , Ming Guo-li , Zheng James Q.
Published: July 2007

Bone morphogenic proteins (BMPs) are involved in axon pathfinding, but how they guide growth cones remains elusive. In this study, we report that a BMP7 gradient elicits bidirectional turning responses from nerve growth cones by acting through LIM kinase (LIMK) and Slingshot (SSH) phosphatase to regulate actin-depolymerizing factor (ADF)/cofilin-mediated actin dynamics. Xenopus laevis growth cones from 4–8-h cultured neurons are attracted to BMP7 gradients but become repelled by BMP7 after overnight culture. The attraction and repulsion are mediated by LIMK and SSH, respectively, which oppositely regulate the phosphorylation-dependent asymmetric activity of ADF/cofilin to control the actin dynamics and growth cone steering. The attraction to repulsion switching requires the expression of a transient receptor potential (TRP) channel TRPC1 and involves Ca2+ signaling through calcineurin phosphatase for SSH activation and growth cone repulsion. Together, we show that spatial regulation of ADF/cofilin activity controls the directional responses of the growth cone to BMP7, and Ca2+ influx through TRPC tilts the LIMK-SSH balance toward SSH-mediated repulsion.
Molecular characterization of centriole assembly in ciliated epithelial cells
Authors: Vladar Eszter K. , Stearns Tim
Published: July 2007

Ciliated epithelial cells have the unique ability to generate hundreds of centrioles during differentiation. We used centrosomal proteins as molecular markers in cultured mouse tracheal epithelial cells to understand this process. Most centrosomal proteins were up-regulated early in ciliogenesis, initially appearing in cytoplasmic foci and then incorporated into centrioles. Three candidate proteins were further characterized. The centrosomal component SAS-6 localized to basal bodies and the proximal region of the ciliary axoneme, and depletion of SAS-6 prevented centriole assembly. The intraflagellar transport component polaris localized to nascent centrioles before incorporation into cilia, and depletion of polaris blocked axoneme formation. The centriolar satellite component PCM-1 colocalized with centrosomal components in cytoplasmic granules surrounding nascent centrioles. Interfering with PCM-1 reduced the amount of centrosomal proteins at basal bodies but did not prevent centriole assembly. This system will help determine the mechanism of centriole formation in mammalian cells and how the limitation on centriole duplication is overcome in ciliated epithelial cells.
Filamin B represses chondrocyte hypertrophy in a Runx2/Smad3-dependent manner
Authors: Zheng Lihua , Baek Hwa-Jin , Karsenty Gerard , Justice Monica J.
Published: July 2007

FILAMIN B, which encodes a cytoplasmic actin binding protein, is mutated in several skeletal dysplasias. To further investigate how an actin binding protein influences skeletogenesis, we generated mice lacking intact Filamin B. As observed in spondylocarpotarsal synostosis syndrome patients, Filamin B mutant mice display ectopic mineralization in many cartilaginous elements. This aberrant mineralization is due to ectopic chondrocyte hypertrophy similar to that seen in mice expressing Runx2 in chondrocytes. Accordingly, removing one copy of Runx2 rescues the Filamin B mutant phenotype, indicating that Filamin B is a regulator of Runx2 function during chondrocyte differentiation. Filamin B binds Smad3, which is known to interact with Runx2. Smad3 phosphorylation is increased in the mutant mice. Thus, Filamin B inhibits Runx2 activity, at least in part, through the Smad3 pathway. Our results uncover the involvement of actin binding proteins during chondrogenesis and provide a molecular basis to a human genetic disease.
A post-transcriptional regulatory switch in polypyrimidine tract-binding proteins reprograms alternative splicing in developing neurons
Authors: Boutz Paul L. , Stoilov Peter , Li Qin , Lin Chia-Ho , Chawla Geetanjali , Ostrow Kristin , Shiue Lily , Ares Manuel , Black Douglas L.
Published: July 2007

Many metazoan gene transcripts exhibit neuron-specific splicing patterns, but the developmental control of these splicing events is poorly understood. We show that the splicing of a large group of exons is reprogrammed during neuronal development by a switch in expression between two highly similar polypyrimidine tract-binding proteins, PTB and nPTB (neural PTB). PTB is a well-studied regulator of alternative splicing, but nPTB is a closely related paralog whose functional relationship to PTB is unknown. In the brain, nPTB protein is specifically expressed in post-mitotic neurons, whereas PTB is restricted to neuronal precursor cells (NPC), glia, and other nonneuronal cells. Interestingly, nPTB mRNA transcripts are found in NPCs and other nonneuronal cells, but in these cells nPTB protein expression is repressed. This repression is due in part to PTB-induced alternative splicing of nPTB mRNA, leading to nonsense-mediated decay (NMD). However, we find that even properly spliced mRNA fails to express nPTB protein when PTB is present, indicating contributions from additional post-transcriptional mechanisms. The PTB-controlled repression of nPTB results in a mutually exclusive pattern of expression in the brain, where the loss of PTB in maturing neurons allows the synthesis of nPTB in these cells. To examine the consequences of this switch, we used splicing-sensitive microarrays to identify different sets of exons regulated by PTB, nPTB, or both proteins. During neuronal differentiation, the splicing of these exon sets is altered as predicted from the observed changes in PTB and nPTB expression. These data show that the post-transcriptional switch from PTB to nPTB controls a widespread alternative splicing program during neuronal development.
Autophagy mitigates metabolic stress and genome damage in mammary tumorigenesis
Authors: Karantza-Wadsworth Vassiliki , Patel Shyam , Kravchuk Olga , Chen Guanghua , Mathew Robin , Jin Shengkan , White Eileen
Published: July 2007

Autophagy is a catabolic process involving self-digestion of cellular organelles during starvation as a means of cell survival; however, if it proceeds to completion, autophagy can lead to cell death. Autophagy is also a haploinsufficient tumor suppressor mechanism for mammary tumorigenesis, as the essential autophagy regulator beclin1 is monoallelically deleted in breast carcinomas. However, the mechanism by which autophagy suppresses breast cancer remains elusive. Here we show that allelic loss of beclin1 and defective autophagy sensitized mammary epithelial cells to metabolic stress and accelerated lumen formation in mammary acini. Autophagy defects also activated the DNA damage response in vitro and in mammary tumors in vivo, promoted gene amplification, and synergized with defective apoptosis to promote mammary tumorigenesis. Therefore, we propose that autophagy limits metabolic stress to protect the genome, and that defective autophagy increases DNA damage and genomic instability that ultimately facilitate breast cancer progression.