bluuebunny/crossref_metadata_2025 huggingface dataset:
Alaska landfast sea ice: Links with bathymetry and atmospheric circulation
Authors: Mahoney Andy , Eicken Hajo , Gaylord Allison Graves , Shapiro Lewis
Published: February 2007

Using Radarsat Synthetic Aperture Radar (SAR) imagery of northern Alaska and northwestern Canada, we calculated a mean climatology of the annual landfast ice cycle for the period 1996–2004. We also present the monthly minimum, mean, and maximum landfast ice extents throughout the study area. These data reveal where and when the landfast is most stable and which sections of the coast are susceptible to midseason breakout events. Stabilization of landfast ice is strongly related to the advance of the seaward landfast ice edge (SLIE) into waters around 18 m deep. Isobaths near this depth are a good approximation for midseason landfast ice extent. Comparison with work from the 1970s suggests a reduced presence of landfast ice in this region of the Arctic, due to later formation and earlier breakup. This will likely lead to an increase in coastal erosion and may also have profound effects upon subsistence activities, which are intimately linked to the timing of marine mammal migration patterns. Interannually, landfast ice formation correlates with the incursion of pack ice into coastal waters, suggesting that the later mean date of formation in recent years may be related to the increasingly northward location of the perennial sea ice edge. The timing of breakup correlates well with onset of thawing air temperatures. Analysis of regional data shows a multidecadal trend toward earlier thaw onset, which suggests that the observed change in breakup dates may be part of a longer‐term trend.
Assessment of dam failure flood and a natural, high‐magnitude flood in a hyperarid region using paleoflood hydrology, Nahal Ashalim catchment, Dead Sea, Israel
Authors: Greenbaum Noam
Published: February 2007

A dam failure flood in 1993 with a peak discharge of 600–700 m3 s−1 (volume of 0.5 × 106 m3) and a natural, rainfall‐runoff flood with a peak discharge of 420 m3s−1 (volume of >2.0 × 106 m3) in 2004 in the Nahal Ashalim catchment (75 km2) in the hyperarid Dead Sea region were comparatively analyzed. The two floods, which caused serious damage to the Dead Sea Works industries, were analyzed for magnitude and frequency using regional analysis, extrapolation from the short systematic record, rainfall‐runoff modeling, and paleoflood hydrology. The 7600‐year paleoflood record was reconstructed at the Ashalim Cave at the upper Nahal Ashalim. Peak discharges in this high‐gradient, mountainous wadi are highly sensitive to the roughness coefficient and the flow regime. The dam failure peak discharge is lower than the envelope curves of measured floods of the Dead Sea region and of paleofloods of the Negev and the Dead Sea deserts. The probability of the dam failure flood and the natural flood were estimated by various methods at >1% to >0.2% and <2% to >0.5%, respectively. Adding the peak discharge of the October 2004 flood increased the probability from >0.2% to 0.5–0.2%. The long paleoflood record encompasses different hydrological regimes related to climatic fluctuations, which are not relevant to the present hydrological regime; therefore the chosen period for frequency analysis was A.D. 1673–1996.
When loss is gain: reduced presenilin proteolytic function leads to increased Aβ42/Aβ40
Authors: Wolfe Michael S
Published: February 2007

More than 100 missense mutations in presenilin 1 and 2 are associated with early‐onset dominant Alzheimer disease. These proteins span the membrane several times and are ostensibly the catalytic component of the γ‐secretase complex, which is responsible for producing the amyloid β‐peptide (Aβ) that deposits in the Alzheimer brain. A common outcome of Alzheimer‐associated presenilin mutations is an increase in the ratio of the more aggregation‐prone 42‐residue form of Aβ to the 40‐residue variant, which is often referred to as a presenilin ‘gain of function’. An apparent paradox is that most of these mutant presenilins have reduced proteolytic efficiency, which forms part of the counter argument that presenilin ‘loss of function’ can cause the neuronal dysfunction and death that lead to the disease. In this review, a unifying hypothesis is presented that puts forward a biochemical mechanism by which slower less‐efficient forms of the protease can result in a greater proportion of 42‐residue Aβ.
Loss‐of‐function presenilin mutations in Alzheimer disease
Authors: De Strooper Bart
Published: February 2007

Presenilin mutations are the main cause of familial Alzheimer disease. From a genetic point of view, these mutations seem to result in a gain of toxic function; however, biochemically, they result in a partial loss of function in the γ‐secretase complex, which affects several downstream signalling pathways. Consequently, the current genetic terminology is misleading. In fact, the available data indicate that several clinical presenilin mutations also lead to a decrease in amyloid precursor protein‐derived amyloid β‐peptide generation, further implying that presenilin mutations are indeed loss‐of‐function mutations. The loss of function of presenilin causes incomplete digestion of the amyloid β‐peptide and might contribute to an increased vulnerability of the brain, thereby explaining the early onset of the inherited form of Alzheimer disease. In this review, I evaluate the implications of this model for the amyloid‐cascade hypothesis and for the efficacy of presenilin/γ‐secretase as a drug target.
Promotion, Information and Advertising: Why Increasingly Blurred Boundaries do not Benefit the Public
Authors: Glatter Jackie
Published: February 2007

Recent legislative proposals from the European Commission to relax the prohibition on direct-to-consumer advertising (DTCA) of prescription medicines in the EU have generated increased debate internationally over the role of the pharmaceutical industry in relation to promotion, information and advertising and the impact of its activities on the public. It is argued that changing information technology and healthcare environments are leading people to take more direct control over their healthcare, although without the necessary health-literacy and critical appraisal skills to do so in a fully informed way. A comprehensive approach to patient information is proposed that would better equip people to take a more active and informed role in both self-care and shared decision making in relation to health, illness and drug and non-drug treatments.
Maximising Profitability through Commercially Successful Implementation of Over-the-Counter Switches
Authors: Eggleston Richard , Bruce Lindsay
Published: February 2007

Under the broad umbrella of generic pharmaceuticals, this paper looks at the specific question of prescription-only medicines to pharmacy switches. Based on an understanding of the current pharmaceuticals market and many successful years' experience of implementing over-the-counter (OTC) switches, the authors offer advice on how to maximise profitability when making the switch to a generic product. The paper covers all aspects, from the initial choice of which product to switch through to the factors, both internal and external, that need to be considered to ensure a successful and profitable switch to OTC. Despite the clear benefits in managing the process well, many companies in the industry still fail to do so. Those who have learned quickly how to handle the specific challenges faced in switching to OTC, and who have developed practices and processes to cope with these, are leading the market and will continue to do so.
Optimising Supply Chain Investments – An Integrated Approach
Authors: Pisani Jo
Published: February 2007

Managing supply chain issues is becoming a critical success factor for branded and generics producers alike. Biotech products and their generic versions require complex supply chain strategies or large capital investment decisions to be made at a time when product launch is still uncertain. This paper describes the issues around making supply chain investment decisions for new generic pharmaceuticals and biogenerics. An integrated planning approach, based on real options valuation, is described, which incorporates product valuation risk with supply chain investment risk. This then forms a more robust basis for making supply chain decisions and for developing alliances with third parties such as contract manufacturers.
Creating Brand Identity for Generic Products
Authors: Williams Don
Published: February 2007

With so many opportunities within the generics industry today as patents expire, new companies are entering the generics market and established companies are adding to their portfolios. This paper looks at the role of branding as generics look to compete more vigorously in this highly competitive arena, and the challenges that exist in creating brand identities to drive their marketing.

The overall competitive marketplace has changed considerably over time and created a very different context in respect of customer ‘need’ states. There is an increasing need to address the end consumer directly via focus on brands. There is continuing proof that adding consumer benefits via effective brand communication can contribute enormously to commercial success — and this is examined here. Generics companies marketing generic products should recognise the benefits of creating brands to achieve visibility, stand-out and clear differentiation via a consumer-focused proposition — and the role that brand identity can play within this.
Evolving Dynamics of US and European Generics Markets
Authors: Schulz Adele
Published: February 2007

The USA has traditionally been seen as the most attractive location for generic products, with the European generics market's development having been stifled by market fragmentation, low brand prices and a general distrust of copy products in some regions. This paper compares the changing dynamics of both European and US markets, and identifies which region is expected to offer generics players the best prospects for future growth. The impact of EU expansion and of recently introduced legislation in both Europe and the USA is assessed, and best practice portfolio management recommendations are evaluated with reference to the geographical region(s) in which companies operate.
The Saga of the Legal Framework for Biogenerics in Europe
Authors: Kox Suzette
Published: February 2007

In 2004, Europe took the lead among regulated markets in creating a legal framework and a regulatory route for biogenerics. The EU has consequently established a competitive advantage over the USA and Japan in this sector. This paper covers the process of drafting and adopting the legal framework for biogenerics in the enlarged EU through the review process of the European pharmaceutical legislation and in parallel with the publication of the new Annex I of Directive 2001/83/EC, which delineates instructions for the presentation and content of the different types of application dossier in Europe. This paper describes the precise chronological order of the development of the legal framework, as well as the main actors in the process, and describes the background to the adoption of the final terminology used to designate biogenerics — that is, ‘similar biological medicinal products’.
Strategies for Biogeneric Success
Authors: Furniss Jim
Published: February 2007

This paper discusses the nature of generic biopharmaceutical products and the barriers to their entry into the market. It reaches the conclusion that there are substantial rewards to be had for the first company to be successful, but that market entry may take longer than many observers think. To be successful, a company must be able to make the product to the required quality standards, to navigate the emerging regulatory pathways successfully and to market the product effectively. In each case the challenge is different, and more complex, than that facing synthetic generic products.
Bringing Generic Medicine Production to Afghanistan: The Business Humanitarian Forum's Cooperative Project with the European Generic Medicines Association
Authors: Maresca John J.
Published: February 2007

The Business Humanitarian Forum (BHF), an international non-profit association based in Geneva, has collaborated with the European Generic medicines Association (EGA) and several companies to donate the machinery needed for the establishment of an Afghan-owned private sector generic medicines factory in Kabul. The new facility will supply much-needed medicines for the Afghan health system, which has been decimated by 20 years of war and mismanagement under Taliban rule.

The project is a good example of how the private sector can contribute to postconflict reconstruction or economic development in poor countries, by supplying expertise, surplus equipment and management assistance to local entrepreneurs. This effort can be especially useful when it aims to meet a recognised humanitarian need in the country concerned.
Strategic Options for Mid-Sized Generics Players
Authors: Sommerfeld Thimo L.
Published: February 2007

As generics markets are becoming more mature, size is playing an increasingly important role. Larger companies and niche players may be able to sustain their profitability by making adjustments to their operations, but mid-sized competitors see their existence as being threatened. Owners and managers at these firms are discussing a wide range of options. Viable options for mid-sized generics businesses follow a limited number of strategies. Waiting for better times is not on that list.
Novartis/Hexal – Lessons for the Generics Industry
Authors: Cloud Frances
Published: February 2007

The acquisition of Hexal by Novartis holds a number of lessons for the generics industry, but it is not clear whether Hexal's peers are drawing the correct conclusions. The deal may give the impression that generic drug assets are very valuable, but a better interpretation might be that times are tough even for the biggest companies and that smart management is what the industry needs most.
Private Equity's Growing role in the Generics Industry
Authors: Sommerfeld Thimo L.
Published: February 2007

Private equity plays an increasingly important role in a number of industries. Early-stage (‘venture capital’) investors have been active in the biotech industry for a long time. Most late-stage (‘buyout’) investors, however, have steered clear of pharmaceutical R&D and generics companies. But the reasons, a comparatively high regulatory environment and the resulting complexities, are losing their threat. In the future, one is likely to see financial investors taking a closer look at the pharmaceutical industry — and at generics opportunities in particular.
Self-consistent variational calculation of the dense fluid helium in the region of partial ionization
Authors: Chen Qifeng , Zhang Ying , Cai Lingcang , Gu Yunjun , Jing Fuqian
Published: February 2007

Developments in shock-wave experimental techniques have allowed Megabar pressure range in dense fluid to be probed. It has been shown that the dissociation of the molecule and ionization of the atom become operative under such ultrahigh pressures. The dense fluid helium will be ionized in high pressures and temperatures. The ionization energy of helium will be lowered due to the interactions among all particles of He, He+, He2+, and e. The ionization degree is obtained from nonideal ionization equilibrium, taking into account the correlation contributions to the chemical potential which is determined self-consistently by the free energy function. The composition of dense helium can be calculated with given densities and temperatures. The equations of state of dense helium plasma are predicted in the density and temperature range of 0<ρ(g∕cm3)<2.0 and 3<T(eV)<7.
Low-temperature plasma-assisted growth of optically transparent, highly oriented nanocrystalline AlN
Authors: Mirpuri C. , Xu S. , Long J. D. , Ostrikov K.
Published: February 2007

Optically transparent, highly oriented nanocrystalline AlN(002) films have been synthesized using a hybrid plasma enhanced chemical vapor deposition and plasma-assisted radio frequency (rf) magnetron sputtering process in reactive Ar+N2 and Ar+N2+H2 gas mixtures at a low Si(111)/glass substrate temperature of 350 °C. The process conditions, such as the sputtering pressure, rf power, substrate temperature, and N2 concentration were optimized to achieve the desired structural, compositional, and optical characteristics. X-ray diffractometry reveals the formation of highly c-oriented AlN films at a sputtering pressure of 0.8 Pa. Field emission scanning electron microscopy suggests the uniform distribution of AlN grains over large surface areas and also the existence of highly oriented in the (002) direction columnar structures of a typical length ∼100−500 nm with an aspect ratio of ∼7−15. X-ray photoelectron and energy dispersive x-ray spectroscopy suggest that films deposited at a rf power of 400 W feature a chemically pure and near stoichiometric AlN. The bonding states of the AlN films have been confirmed by Raman and Fourier transform infrared spectroscopy showing strong E2 (high) and E1 transverse optical phonon modes. Hydrogenated AlN films feature an excellent optical transmittance of ∼80% in the visible region of the spectrum, promising for advanced optical applications.
Electronic structure and charge injection at interface between electrode and liquid-crystalline semiconductor
Authors: Toda Tohru , Hanna Jun-ichi , Tani Tadaaki
Published: February 2007

The measurement and analysis of the current-voltage characteristics of a liquid-crystalline organic semiconductor 2-(4′-octyphenyl)-6-dodecyloxynaphthalene (8-PNP-O12) in contact with electrodes of Pt, Au, ITO, Cr, and Al (in the order of work function) have revealed that the injection of holes from the electrodes of Pt, Au, and indium tin oxide to 8-PNP-O12 takes place according to the Richardson-Schottky model and that an electric double layer is formed at the interface between each of these electrodes and 8-PNP-O12, making it difficult to inject holes from the former to the latter.
Quantum dot strain engineering of InAs∕InGaAs nanostructures
Authors: Seravalli L. , Minelli M. , Frigeri P. , Franchi S. , Guizzetti G. , Patrini M. , Ciabattoni T. , Geddo M.
Published: February 2007

We present a complete study both by experiments and by model calculations of quantum dot strain engineering, by which a few optical properties of quantum dot nanostructures can be tailored using the strain of quantum dots as a parameter. This approach can be used to redshift beyond 1.31μm and, possibly, towards 1.55μm the room-temperature light emission of InAs quantum dots embedded in InGaAs confining layers grown on GaAs substrates. We show that by controlling simultaneously the lower confining layer thickness and the confining layers’ composition, the energy gap of the quantum dot material and the band discontinuities in the quantum dot nanostructure can be predetermined and then the light emission can be tuned in the spectral region of interest. The availability of two degrees of freedom allows for the control of two parameters, which are the emission energy and the emission efficiency at room temperature. The InAs∕InGaAs structures were grown by the combined use of molecular beam epitaxy and atomic layer molecular beam epitaxy; their properties were studied by photoluminescence and photoreflectance spectroscopies and by atomic force microscopy; in particular, by means of photoreflectance not only the spectral features related to quantum dots were studied but also those of confining and wetting layers. The proposed approach has been used to redshift the room-temperature light emission wavelength up to 1.44μm. The optical results were analyzed by a simple effective-mass model that also offers a rationale for engineering the properties of structures for efficient long-wavelength operation.
Field-effect transistor with a prismoidal controlling gate
Authors: Gribnikov Z. S. , Haddad G. I.
Published: February 2007

A very short-channel field-effect transistor (FET), which is controlled by a nonplanar prismoidal gate, is proposed and its stationary JV characteristics are derived. The prismoidal gate effectively depletes a thin electron channel in a very narrow strip around the gate apex. Interaction of the channel electrons with a controlling gate potential is additionally focused by a selected two-layer dielectric separating the channel and gate. It is shown that in the considered FETs there exist both “standard” regimes characterized by quasisaturation of the drain current jD, with an increase in the drain-source voltage uDS, and nonstandard regimes, with drooping jDuDS characteristics and a “self-blocking” current jD. We consider the dependence of the channel conductance on the gate curvature near the apex.
Grain boundary compositions in Cu(InGa)Se2
Authors: Lei C. , Li C. M. , Rockett A. , Robertson I. M.
Published: February 2007

A microchemical analysis study is reported comparing the grain and grain boundary chemistries of Cu(In,Ga)Se2 (CIGS) films deposited by three different laboratories by different processes. An analysis of a GaAs wafer is described to provide a calibration of the accuracy and precision of the energy dispersive spectroscopy nanoprobe analysis as applied in the current instruments. When averaged over many measurements the precision of the instrument is ±0.1at.% and the accuracy is ±1.0at.% for individual points. The analysis of the CIGS shows less than 0.5at.% composition difference for each constituent element between grain and grain boundary compositions when averaged over hundreds of data points for most samples. One sample deposited at 400°C as a bilayer shows different grain and grain boundary compositions with grain boundaries being In deficient and Se rich. Both grain and grain boundary data in this sample scatter along a line between the Cu(In,Ga)Se2 and CuSe2 phases, which is a nonequilibrium behavior. The scatter in individual analyses is significantly greater than the noise in the analysis technique indicating real composition differences at different points within both grains and grain boundaries. No evidence was found for other substitutional impurities such as O or Na in the grain boundaries. The results suggest that the grain boundaries are self-passivating without a chemistry change.
A one-dimensional hydrodynamic model for pressures induced near the coating-water interface during laser shock peening
Authors: Wu Benxin , Shin Yung C.
Published: February 2007

In laser shock peening (LSP) under a water-confinement regime, laser-matter interaction near the coating-water interface can induce very high pressures in the order of gigapascal, which can impart compressive residual stresses into metal workpieces to improve fatigue and corrosion properties. However, self-closed models with spatial distribution considerations for the induced pressures near the coating-water interface in LSP are rarely reported in literature. In this paper, a self-closed model is developed by numerically solving the one-dimensional hydrodynamic equations, supplemented with appropriate equations of state of water and the coating material. The model can produce the one-dimensional spatial distributions of the material responses near the water-coating interface in LSP. The model-predicted pressures have been compared with experimental measurements under a variety of conditions typical for LSP, and good agreements have been found for both the transient pressure history and the peak pressure magnitude.
Multiple quantum correlated spectroscopy revamped by asymmetric z-gradient echo detection signal intensity as a function of the read pulse flip angle as verified by heteronuclear H1∕P31 experiments
Authors: Jiang Bin , Liu Huili , Liu Maili , Ye Chaohui , Mao Xi-an
Published: February 2007

Heteronuclear multiple quantum (n=±0 and n=±2) correlated spectroscopy revamped by asymmetric z-gradient echo detection (CRAZED) experiments were performed on the spins P31 and H1 in a H3PO4 solution in order to determine the optimum flip angle for the read pulse. It has been shown that for the negative quantum signals, the maximum signals appear at β=0, and for the positive quantum signals, the maximum signals appear at β=π. The CRAZED signals were compared to the single quantum signals in two-pulse two-gradient experiments. It is found that the CRAZED signals can also be distinguished into gradient echoes and spin echoes. The gradient-echo-type CRAZED signal requires β=0 and the spin-echo-type CRAZED signal requires β=π for maximum echo intensities, in the same way as in single quantum experiments.
Phase-field model for epitaxial ferroelectric and magnetic nanocomposite thin films
Authors: Zhang J. X. , Li Y. L. , Schlom D. G. , Chen L. Q. , Zavaliche F. , Ramesh R. , Jia Q. X.
Published: February 2007

A phase-field model was developed for studying the magnetoelectric coupling effect in epitaxial ferroelectric and magnetic nanocomposite thin films. The model can simultaneously take into account the ferroelectric and magnetic domain structures, the electrostrictive and magnetostrictive effects, substrate constraint, as well as the long-range interactions such as magnetic, electric, and elastic interactions. As an example, the magnetic-field-induced electric polarization in BaTiO3–CoFe2O4 nanocomposite film was analyzed. The effects of the film thickness, morphology of the nanocomposite, and substrate constraint on the degree of magnetoelectric coupling were discussed.
New Thomson scattering diagnostic on RFX-mod
Authors: Alfier A. , Pasqualotto R.
Published: February 2007

This article describes the completely renovated Thomson scattering (TS) diagnostic employed in the modified Reversed Field eXperiment (RFX-mod) since it restarted operation in 2005. The system measures plasma electron temperature and density profiles along an equatorial diameter, measuring in 84 positions with 7mm spatial resolution. The custom built Nd:YLF laser produces a burst of 10 pulses at 50Hz with energy of 3J, providing ten profile measurements in a plasma discharge of about 300ms duration. An optical delay system accommodates three scattering volumes in each of the 28 interference filter spectrometers. Avalanche photodiodes detect the Thomson scattering signals and allow them to be recorded by means of waveform digitizers. Electron temperature is obtained using an alternative relative calibration method, based on the use of a supercontinuum light source. Rotational Raman scattering in nitrogen has supplied the absolute calibration for the electron density measurements. During RFX-mod experimental campaigns in 2005, the TS diagnostic has demonstrated its performance, routinely providing reliable high resolution profiles.
Field and laboratory emission cell automation and control system for investigating surface chemistry reactions
Authors: Flemmer Michael M. , Ham Jason E. , Wells J. R.
Published: February 2007

A novel system [field and laboratory emission cell (FLEC) automation and control system] has been developed to deliver ozone to a surface utilizing the FLEC to simulate indoor surface chemistry. Ozone, humidity, and air flow rate to the surface were continuously monitored using an ultraviolet ozone monitor, humidity, and flow sensors. Data from these sensors were used as feedback for system control to maintain predetermined experimental parameters. The system was used to investigate the chemistry of ozone with α-terpineol on a vinyl surface over 72h. Keeping all other experimental parameters the same, volatile organic compound emissions from the vinyl tile with α-terpineol were collected from both zero and 100ppb(partsper109) ozone exposures. System stability profiles collected from sensor data indicated experimental parameters were maintained to within a few percent of initial settings. Ozone data from eight experiments at 100ppb (over 339h) provided a pooled standard deviation of 1.65ppb and a 95% tolerance of 3.3ppb. Humidity data from 17 experiments at 50% relative humidity (over 664h) provided a pooled standard deviation of 1.38% and a 95% tolerance of 2.77%. Data of the flow rate of air flowing through the FLEC from 14 experiments at 300ml∕min (over 548h) provided a pooled standard deviation of 3.02ml∕min and a 95% tolerance range of 6.03ml∕min. Initial experimental results yielded long term emissions of ozone/α-terpineol reaction products, suggesting that surface chemistry could play an important role in indoor environments.
Dual monogamy inequality for entanglement
Authors: Gour Gilad , Bandyopadhyay Somshubhro , Sanders Barry C.
Published: February 2007

We establish duality for monogamy of entanglement: whereas monogamy of entanglement inequalities provide an upper bound for bipartite sharability of entanglement in a multipartite system, as quantified by linear entropy, we prove that the same quantity (namely, linear entropy) provides a lower bound for distribution of bipartite entanglement in a multipartite system. Our theorem for monogamy of entanglement is used to establish relations between bipartite entanglement that separate one qubit from the rest versus separating two qubits from the rest.
Effects of non-Maxwellian electron velocity distribution function on two-stream instability in low-pressure discharges
Authors: Sydorenko D. , Smolyakov A. , Kaganovich I. , Raitses Y.
Published: February 2007

Electron emission from discharge chamber walls is important for plasma maintenance in many low-pressure discharges. The electrons emitted from the walls are accelerated by the sheath electric field and are injected into the plasma as an electron beam. Penetration of this beam through the plasma is subject to the two-stream instability, which tends to slow down the beam electrons and heat the plasma electrons. In the present paper, a one-dimensional particle-in-cell code is used to simulate these effects both in a collisionless plasma slab with immobile ions and in a cross-field discharge of a Hall thruster. The two-stream instability occurs if the total electron velocity distribution function of the plasma-beam system is a nonmonotonic function of electron speed. Low-pressure plasmas can be depleted of electrons with energy above the plasma potential. This study reveals that under such conditions the two-stream instability depends crucially on the velocity distribution function of electron emission. It is shown that propagation of the secondary electron beams in Hall thrusters may be free of the two-stream instability if the velocity distribution of secondary electron emission is a monotonically decaying function of speed. In this case, the beams propagate between the walls with minimal loss of the beam current and the secondary electron emission does not affect the thruster plasma properties.
Large-mode-number magnetohydrodynamic instability driven by sheared flows in a tokamak plasma with reversed central shear
Authors: Bierwage Andreas , Yu Qingquan , Günter Sibylle
Published: February 2007

The effect of a narrow sub-Alfvénic shear flow layer near the minimum qmin of the tokamak safety factor profile in a configuration with reversed central shear is analyzed. Sufficiently strong velocity shear gives rise to a broad spectrum of fast growing Kelvin-Helmholtz (KH)-like ideal magnetohydrodynamic modes with dominant mode numbers m,n∼10. Nonlinear simulations with finite resistivity show magnetic reconnection near ripples caused by KH-like vortices, the formation of turbulent structures, and a flattening of the flow profile. The KH modes are compared to double tearing modes that dominate at lower shearing rates. The possible application of these results in tokamaks with internal transport barrier is discussed.
High resolution transmission electron microscopy and Raman scattering studies of room temperature ferromagnetic Ni-doped ZnO nanocrystals
Authors: Wang Hao , Chen Y. , Wang H. B. , Zhang C. , Yang F. J. , Duan J. X. , Yang C. P. , Xu Y. M. , Zhou M. J. , Li Q.
Published: February 2007

Ni-doped ZnO nanocrystals have been synthesized by a wet chemical reaction. The nanocrystals have been investigated carefully by high resolution transmission electron microscopy and all the particles are found to be the known wurtzite ZnO. X-ray photoelectron spectroscopy and Raman spectra results provide the evidence that Ni2+ is incorporated into the ZnO lattice at Zn2+ site. Magnetic property measurements reveal that the as-grown Zn1−xNixO nanocrystals exhibit room temperature ferromagnetic behaviors with saturation magnetization of 0.01emu∕g and Curie temperature above 340K for Ni concentration of ∼1% in atomic ratio.
Motion characteristics of long ac arcs in atmospheric air
Authors: Gu Shanqiang , He Jinliang , Zeng Rong , Zhang Bo , Xu Guozheng , Chen Weijiang
Published: February 2007

Experiments on the motion of long alternating current arcs in atmospheric air show that the anode and cathode arc roots have different motion characteristics because of different formation mechanisms. During a half cycle of the arc current, the anode arc root moves towards the direction of magnetic force and occasionally has a jumping motion, while the cathode arc root moves sufficiently slow to consider it stationary and hardly has any jump. The arc column has a complex shape and moves under the drive of the magnetic force and is also quickened by the lower arc root.
Giant magnetoresistance behavior of an iron/carbonized polyurethane nanocomposite
Authors: Guo Zhanhu , Park Sung , Hahn H. Thomas , Wei Suying , Moldovan Monica , Karki Amar B. , Young David P.
Published: February 2007

This letter describes the magnetoresistance (MR) behavior of the heat treated polyurethane composites reinforced with iron nanoparticles. The flexible nanocomposites were fabricated by the surface-initiated-polymerization method. The uniformly distributed nanoparticles within the polymer matrix, well characterized by field emission scanning electron microscopy, favor a continuous carbon matrix formation, rendering the transition from insulating to conductive composites. The coercive forces reflect strong particle loading and matrix dependent magnetic properties. By simply annealing in a reducing environment, the obtained nanocomposites possess a MR of 7.3% at room temperature and 14% at 130K occurring at a field of 90kOe.
Properties of Ta–Ge–(O)N as a diffusion barrier for Cu on Si
Authors: Rawal S. , Norton D. P. , Ajmera Hiral , Anderson T. J. , McElwee-White L.
Published: February 2007

The properties of Ta–Ge–(O)N as a diffusion barrier for Cu on silicon have been investigated. Ta–Ge–(O)N was deposited on single crystal p-Si(001) by reactive sputtering. This was followed by in situ deposition of Cu. Diffusion barrier tests were conducted by subsequent annealing of individual samples in Ar atmosphere at higher temperature. The films were characterized by x-ray diffraction, Auger electron spectroscopy, and four-point probe. The results indicate that Ta–Ge–(O)N fails after annealing at 500°C for 1h compared to Ta(O)N which fails after annealing at 400°C for 1h indicating better diffusion barrier properties.
Random point fields for paraparticles of any order
Authors: Tamura Hiroshi , Ito Keiichi R.
Published: February 2007

Random point fields which describe gases consisting of paraparticles of any order p∊N are given by means of the canonical ensemble approach. The analysis for the cases of the parafermion gases are discussed in full detail and it is shown that the partition functions are pth power of that of the usual (i.e., p=1) fermion. The same is true for parabosons.
Magnetic and transport properties of homogeneous MnxGe1−x ferromagnetic semiconductor with high Mn concentration
Authors: Chen Y. X. , Yan Shi-shen , Fang Y. , Tian Y. F. , Xiao S. Q. , Liu G. L. , Liu Y. H. , Mei L. M.
Published: February 2007

Homogeneous MnxGe1−x ferromagnetic semiconductor films with high Mn concentration were prepared, contrasting with dilute inhomogeneous MnxGe1−x magnetic semiconductors. The saturation magnetization of Mn0.57Ge0.43 films is high, up to 327emu∕cm3 (1.04μB∕Mn) at 5K, and the Curie temperature is about 213K. The Mn0.57Ge0.43 films show semiconducting resistance, but the magnetoresistance is negligibly small. The anomalous Hall effect was observed below the Curie temperature, which is consistent with the magnetic measurements. The global ferromagnetism was discussed based on s,p-d exchange coupling between the weakly localized s,p hole carriers and the strongly localized d electrons of the Mn atoms.
Observation of photoassisted polarization switching in BiFeO3 thin films probed by terahertz radiation
Authors: Takahashi Kouhei , Tonouchi Masayoshi
Published: February 2007

The authors have examined the effect of photoexcitation in a multiferroic BiFeO3 thin film using terahertz radiation as the probe. The illumination of femtosecond laser pulses with a center wavelength of 400nm gave rise to a significant improvement in the polarization switching process by the application of bias electric field. This effect is attributed to the depinning of domain walls induced by carrier excitation as reported in ordinary ferroelectrics. The authors revealed that a significantly weak laser power in the order of submilliwatt is sufficient to invoke this effect.
Curvelets for surface characterization
Authors: Ma Jianwei
Published: February 2007

Surface metrology is the science of measuring small-scale features on surfaces, which is important to many disciplines including tribology, fluid mechanics, optics, and manufacturing. Applications of wavelets on functional surfaces have become an increasing interest. Unfortunately, the traditional wavelets have good performance only at representing point singularities because they ignore the geometric properties of surfaces with scratches and do not exploit the regularity of curves. In this letter, a second-generation curvelet transform combined with total variation minimization is proposed to characterize surfaces with general scratches along C2 singularities. The ability of the developed geometric multiscale method is demonstrated on bioengineering surfaces.
Electron-beam-induced formation of Zn nanocrystal islands in a SiO2 layer
Authors: Kim Tae Whan , Shin Jae Won , Lee Jeong Yong , Jung Jae Hun , Lee Jung Wook , Choi Won Kook , Jin Sungho
Published: February 2007

Electron-beam-induced Zn nanocrystal islands were formed in a dielectric SiO2 layer. When a ZnO thin film on a p-type Si with amorphous SiOx interface layer is subjected to a 900°C annealing followed by electron irradiation in a transmission electron microscope environment, an amorphous Zn2xSi1−xO2 layer is formed. Upon irradiation with a 300keV electrons, metallic and single crystal nanoislands of Zn with ∼7–10nm diameter were formed and embedded within the SiO2 interface layer. Possible mechanisms for the formation of Zn nanocrystals are presented.
Menstrual cycle phase modulates reward-related neural function in women
Authors: Dreher Jean-Claude , Schmidt Peter J. , Kohn Philip , Furman Daniella , Rubinow David , Berman Karen Faith
Published: February 2007

There is considerable evidence from animal studies that the mesolimbic and mesocortical dopamine systems are sensitive to circulating gonadal steroid hormones. Less is known about the influence of estrogen and progesterone on the human reward system. To investigate this directly, we used functional MRI and an event-related monetary reward paradigm to study women with a repeated-measures, counterbalanced design across the menstrual cycle. Here we show that during the midfollicular phase (days 4–8 after onset of menses) women anticipating uncertain rewards activated the orbitofrontal cortex and amygdala more than during the luteal phase (6–10 days after luteinizing hormone surge). At the time of reward delivery, women in the follicular phase activated the midbrain, striatum, and left fronto-polar cortex more than during the luteal phase. These data demonstrate augmented reactivity of the reward system in women during the midfollicular phase when estrogen is unopposed by progesterone. Moreover, investigation of between-sex differences revealed that men activated ventral putamen more than women during anticipation of uncertain rewards, whereas women more strongly activated the anterior medial prefrontal cortex at the time of reward delivery. Correlation between brain activity and gonadal steroid levels also revealed that the amygdalo-hippocampal complex was positively correlated with estradiol level, regardless of menstrual cycle phase. Together, our findings provide evidence of neurofunctional modulation of the reward system by gonadal steroid hormones in humans and establish a neurobiological foundation for understanding their impact on vulnerability to drug abuse, neuropsychiatric diseases with differential expression across males and females, and hormonally mediated mood disorders.
Two B3 domain transcriptional repressors prevent sugar-inducible expression of seed maturation genes in
Arabidopsis
seedlings
Authors: Tsukagoshi Hironaka , Morikami Atsushi , Nakamura Kenzo
Published: February 2007

During development of plant seeds, embryos import nutrients and store massive amounts of reserves. Seed reserves are rapidly degraded and mobilized to support seedling development after germination. HIGH-LEVEL EXPRESSION OF SUGAR-INDUCIBLE GENE 2 (HSI2) of
Arabidopsis thaliana
is a B3 DNA-binding domain protein that represses the transcription of sugar-inducible reporter gene. Although disruption of
HSI2
or
HSI2-Like 1
(
HSL1
) did not affect growth, seeds with disruption of both
HSI2
and
HSL1
(
KK
mutant) developed abortive seedlings that stopped growing 7–9 days after imbibition.
KK
seedlings developed swollen hypocotyls that accumulated seed storage proteins and oil on medium containing sucrose or other metabolizable sugars, and calluses developed from
KK
seedlings also accumulated seed storage reserves. The expression of seed maturation genes, which include LEAFY COTYLEDON-type master regulators, in
KK
seedlings depended on the concentration of sucrose, suggesting that sugar controls the expression of seed maturation genes. Our results suggest that HSI2 and HSL1 repress the sugar-inducible expression of the seed maturation program in seedlings and play an essential role in regulating the transition from seed maturation to seedling growth.
Complex network analysis of free-energy landscapes
Authors: Gfeller D. , De Los Rios P. , Caflisch A. , Rao F.
Published: February 2007

The kinetics of biomolecular isomerization processes, such as protein folding, is governed by a free-energy surface of high dimensionality and complexity. As an alternative to projections into one or two dimensions, the free-energy surface can be mapped into a weighted network where nodes and links are configurations and direct transitions among them, respectively. In this work, the free-energy basins and barriers of the alanine dipeptide are determined quantitatively using an algorithm to partition the network into clusters (i.e., states) according to the equilibrium transitions sampled by molecular dynamics. The network-based approach allows for the analysis of the thermodynamics and kinetics of biomolecule isomerization without reliance on arbitrarily chosen order parameters. Moreover, it is shown on low-dimensional models, which can be treated analytically, as well as for the alanine dipeptide, that the broad-tailed weight distribution observed in their networks originates from free-energy basins with mainly enthalpic character.
Understanding the nanoparticle–protein corona using methods to quantify exchange rates and affinities of proteins for nanoparticles
Authors: Cedervall Tommy , Lynch Iseult , Lindman Stina , Berggård Tord , Thulin Eva , Nilsson Hanna , Dawson Kenneth A. , Linse Sara
Published: February 2007

Due to their small size, nanoparticles have distinct properties compared with the bulk form of the same materials. These properties are rapidly revolutionizing many areas of medicine and technology. Despite the remarkable speed of development of nanoscience, relatively little is known about the interaction of nanoscale objects with living systems. In a biological fluid, proteins associate with nanoparticles, and the amount and presentation of the proteins on the surface of the particles leads to an
in vivo
response. Proteins compete for the nanoparticle “surface,” leading to a protein “corona” that largely defines the biological identity of the particle. Thus, knowledge of rates, affinities, and stoichiometries of protein association with, and dissociation from, nanoparticles is important for understanding the nature of the particle surface seen by the functional machinery of cells. Here we develop approaches to study these parameters and apply them to plasma and simple model systems, albumin and fibrinogen. A series of copolymer nanoparticles are used with variation of size and composition (hydrophobicity). We show that isothermal titration calorimetry is suitable for studying the affinity and stoichiometry of protein binding to nanoparticles. We determine the rates of protein association and dissociation using surface plasmon resonance technology with nanoparticles that are thiol-linked to gold, and through size exclusion chromatography of protein–nanoparticle mixtures. This method is less perturbing than centrifugation, and is developed into a systematic methodology to isolate nanoparticle-associated proteins. The kinetic and equilibrium binding properties depend on protein identity as well as particle surface characteristics and size.
Partial rescue of MeCP2 deficiency by postnatal activation of MeCP2
Authors: Giacometti Emanuela , Luikenhuis Sandra , Beard Caroline , Jaenisch Rudolf
Published: February 2007

In humans, mutations in the X-linked
MECP2
gene, are the cause of Rett syndrome (RTT), a neurodevelopmental disorder that affects mainly girls. MeCP2 binds to methylated CpGs and is thought to act as a transcriptional repressor. In male mice, deletion or targeted mutation of
Mecp2
leads to lethality and causes a neuronal phenotype. Selective mutation of
Mecp2
in postnatal neurons results in a similar, although delayed, phenotype, suggesting that the symptoms are caused by MeCP2 deficiency in postmitotic neurons. In agreement with this idea, expression of a Mecp2 transgene in postmitotic neurons of
Mecp2
-null mutant mice resulted in the phenotypical rescue of the symptoms. To assess whether postnatal activation of MeCP2 in mutant animals could also affect the progression of the disorder, we constructed a conditionally active Mecp2 “rescue transgene” that was activated between P0 and P30. The Mecp2 transgene was under the control of the CAGGS promoter and was activated by using brain specific Cre-mediated recombination. Our results indicate that postnatal, neuron-specific activation of MeCP2 as late as 2–4 weeks of age significantly prolonged the lifespan of mutant animals and delayed the onset of neurologic symptoms.
GSTπ expression mediates dopaminergic neuron sensitivity in experimental parkinsonism
Authors: Smeyne Michelle , Boyd Justin , Raviie Shepherd Kennie , Jiao Yun , Pond Brooks Barnes , Hatler Matthew , Wolf Roland , Henderson Colin , Smeyne Richard Jay
Published: February 2007

The cause of 95% of Parkinson's disease (PD) cases is unknown. It is hypothesized that PD arises from an interaction of free-radical-generating agents with an underlying genetic susceptibility to these compounds. Here we use the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine model of parkinsonism to examine the role of a dual function protein, GSTπ, in dopaminergic neuron death. GSTπ is the only GST family member expressed in substantia nigra neurons. GSTπ reduction by pharmacological blockade, RNA inhibition, and gene targeting increases sensitivity to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, suggesting that differential expression of GSTπ contributes to the sensitivity to xenobiotics in the substantia nigra and may influence the pathogenesis of reactive oxygen species-induced neurological disorders including PD.