bluuebunny/crossref_metadata_2025 huggingface dataset:
MIRACULOUS RECOVERY? HANDEL’S ILLNESSES, THE NARRATIVE TRADITION OF HEROIC STRENGTH AND THE ORATORIO TURN
Authors: HUNTER DAVID
Published: November 2006

The image of the heroic Handel, typified by claims of immense physical and mental toughness, and rapid – even miraculous – recovery, may satisfy the credulous, but it needs considerable modification once we realize that Handel continued to suffer following the first acute paralytic attack in 1737. It is no coincidence that the onset of acute symptoms occurred during Handel’s last lengthy season of opera production and that oratorios came to dominate his composing and his shortened performance seasons thereafter.

Whatever the immediate causes for Handel’s decisions to write and publicly to perform the first few English-language works, the intensification of that practice after 1737 was due in large measure to the challenges posed by lead poisoning and its ensuing saturnine gout, and an increasing debility exacerbated by obesity. In other words, the illnesses should be considered as an integral element in the switch by Handel to writing his late works, the major oratorios.
Climate sensitivity of the century‐scale hydrogen peroxide (H2O2) record preserved in 23 ice cores from West Antarctica
Authors: Frey Markus M. , Bales Roger C. , McConnell Joseph R.
Published: November 2006

We report new century‐scale ice core records of hydrogen peroxide (H2O2), a major atmospheric oxidant, from 23 locations across the West Antarctic Ice Sheet (WAIS) and use the spatial variability of (multi‐) annual mean H2O2 concentrations in snow and firn to investigate the sensitivity of ice core H2O2 preservation to mean annual temperature and accumulation rate. In agreement with the ice‐air equilibrium partitioning, H2O2 uptake in near‐surface firn was found to be greatest at low temperatures, while postdepositional losses from degassing increase as accumulation rates decrease. This resulted in almost complete loss of H2O2 at warm (>−25°C), low‐accumulation sites (<13 cm yr−1), but excellent preservation of records at cold, high‐accumulation sites. A two‐parameter semiempirical model fitted to the 1911–1960 H2O2 means across all sites predicts >94% deviations from the ice‐air equilibrium at high‐accumulation sites (>30 cm yr−1), but close‐to‐equilibrium values on the East Antarctic Plateau, where it is dry (<11 cm yr−1). It also estimates a weighted average of the annual atmospheric H2O2 cycle of 1–3 pptv, about 10% of the levels at the bottom of the H2O2 range observed in winter and early spring in coastal Antarctica. Sensitivities from the model fit suggest that recent changes of annual mean temperature observed in Antarctica have no noticeable effect on the H2O2 record in the interior of West Antarctica and that interannual variability of annual H2O2 is dominated by variations in regional‐scale accumulation under the current WAIS climate. Intermittent correlations between the first PC time series of accumulation rate and H2O2 concentration anomalies and the annualized SOI during the 20th century are statistically significant (r > 0.6, p < 0.05) during extended El Niño–La Niña events and explain the occurrence of significant spectral peaks at ENSO‐like periodicities (2–7 years) in the H2O2 record. Core records of H2O2 at high‐accumulation sites (>30 cm yr−1) are most suitable for detection of temporal changes in atmospheric concentration, although a long‐term H2O2 record will be well preserved under the current environment at the WAIS Divide core site.
Seasonal variation in the stable isotopic composition of precipitation in the tropical montane forests of Monteverde, Costa Rica
Authors: Rhodes Amy L. , Guswa Andrew J. , Newell Silvia E.
Published: November 2006

Climate and land use change may diminish orographic clouds over tropical montane forests, stressing biota and water resources during dry seasons. From 2003 to 2005 we measured the stable isotopic composition of precipitation and throughfall in Monteverde, Costa Rica, to distinguish convective, wet season rainfall associated with the Intertropical Convergence Zone (ITCZ) from dry season, orographic rain produced by northeasterly trade winds. While event‐to‐event fluctuations of δ18O and δ2H are high, monthly samples reveal a seasonal signal that may be used to trace water through the hydrologic cycle. Deuterium excess indicates that water evaporated from land is an important flux to the region during the transitional and dry seasons when winds from the Caribbean slope dominate. Following the shift to convective rainfall at the start of the wet season, when the western equatorial winds influence the Pacific slope of Costa Rica, d excess values become depressed. Yet as the wet season progresses, d excess begins to climb. These data suggest that several months of rain are needed following an acute dry season on the northern Pacific slope before a terrestrial evaporative signal is detected in wet season precipitation. The evaporative flux may result from a wet season expansion of surface water bodies and flooding of seasonal wetlands.
Influence of aerosols on the shortwave cloud radiative forcing from North Pacific oceanic clouds: Results from the Cloud Indirect Forcing Experiment (CIFEX)
Authors: Wilcox Eric M. , Roberts Greg , Ramanathan V.
Published: November 2006

Aerosols over the Northeastern Pacific Ocean enhance the cloud drop number concentration and reduce the drop size for marine stratocumulus and cumulus clouds. These microphysical effects result in brighter clouds, as evidenced by a combination of aircraft and satellite observations. In‐situ measurements from the Cloud Indirect Forcing Experiment (CIFEX) indicate that the mean cloud drop number concentration in low clouds over the polluted marine boundary layer is greater by 53 cm−3 compared to clean clouds, and the mean cloud drop effective radius is smaller by 4 μm. We link these in‐situ measurements of cloud modification by aerosols, for the first time, with collocated satellite broadband radiative flux observations from the Clouds and the Earth's Radiant Energy System to show that these microphysical effects of aerosols enhance the top‐of‐atmosphere cooling by −9.9 ± 4.3 W m−2 for overcast conditions.
Numerical simulation of convection and mixing in magma chambers replenished with CO2‐rich magma
Authors: Longo Antonella , Vassalli Melissa , Papale Paolo , Barsanti Michele
Published: November 2006

Magma convection and mixing, and periodic refilling, commonly occur in magma chambers. We show here that the presence of CO2 in the refilling magma is a very efficient mean of inducing buoyant‐driven plume rise and large scale convection. Numerical simulations performed with an appositely developed code for the transient 2D dynamics of multicomponent compressible to incompressible fluids reveal several features of the processes of plume rise, convection and mixing in magma chambers associated with chamber refilling. A parametric study on CO2 abundance in the refilling magma shows that progressively larger amounts of this volatile produce a shift from simple plume rise and spreading near the chamber top, to complex patterns of flow circulation and large scale vorticity and mixing. Lower chamber depth and lower magma viscosity largely enhance the efficiency of mixing and convection, favoring the formation of multiple vortexes migrating with time.
Natural post-translational modifications of chemokines
Authors: Proost P. , Struyf S. , Van Damme J.
Published: November 2006

Chemokines, adhesion molecules, cytokines and proteases regulate the extravasation of leucocytes during acute and chronic inflammation and leucocyte homing. Chemokines are produced after transcriptional activation by inflammatory mediators such as cytokines or microbial Toll-like receptor ligands and their effect depends on the expression of chemokine receptors on specific cell types. More and more evidence points towards a role for post-translational modifications in the fine-tuning of chemokine activity. Although both glycosylation and proteolytic processing of the C- and/or N-terminus of chemokines has been reported, mainly proteolytic processing of the N-terminus appears to affect the receptor specificity, chemotactic property and signalling potency of these low-molecular-mass proteins. N-terminal processing of chemokines by aminopeptidases or endoproteases may alter the receptor specificity and may result in up- or down-regulation of their chemotactic, antiviral or angiogenic activity.
Core promoter elements recognized by transcription factor IIB
Authors: Deng W. , Roberts S.G.E.
Published: November 2006

The general transcription factor TFIIB (transcription factor IIB) plays a critical role in the assembly of the RNA polymerase II pre-initiation complex. TFIIB can make sequence-specific DNA contacts both upstream and downstream of the TATA box. This has led to the definition of two core promoter BREs (TFIIB-recognition elements), one upstream [BREu (upstream BRE)] and one downstream of TATA box [BREd (downstream BRE)]. TFIIB–BREu and TFIIB–BREd contacts are mediated by two independent DNA-recognition motifs within the core domain of TFIIB. Both the BREu and the BREd modulate the transcriptional potency of a promoter. However, the net effect of the BREs on promoter activity is dependent on the specific blend of elements present within a core promoter.
Recruitment of RNA polymerase to Class II CRP-dependent promoters is improved by a second upstream-bound CRP molecule
Authors: Miroslavova N.S. , Mitchell J.E. , Tebbutt J. , Busby S.J.W.
Published: November 2006

Genetics and biochemistry have been exploited to investigate transcription activation by the Escherichia coli CRP (cAMP receptor protein) factor at promoters with a DNA site for CRP near position −41 and the effects of a second upstream-bound CRP molecule. We show that the upstream-bound CRP contributes to transcription activation by improving the recruitment of RNA polymerase.
Transcription factor TFIIIB and transcription by RNA polymerase III
Authors: Kassavetis G.A. , Geiduschek E.P.
Published: November 2006

pol (RNA polymerase) III is charged with the task of transcribing nuclear genes encoding diverse small structural and catalytic RNAs. We present a brief review of the current understanding of several aspects of the pol III transcription apparatus. The focus is on yeast and, more specifically, on Saccharomyces cerevisiae; preponderant attention is given to the TFs (transcription initiation factors) and especially to TFIIIB, which is the core pol III initiation factor by virtue of its role in recruiting pol III to the transcriptional start site and its essential roles in forming the transcription-ready open promoter complex. Certain relatively recent developments are also selected for brief comment: (i) the genome-wide analysis of occupancy of pol III-transcribed genes (and other loci) by the transcription apparatus and the location of pol III transcription in the cell; (ii) progress toward a mechanistic and molecular understanding of the regulation of transcription by pol III in yeast; and (iii) recent experiments identifying a high mobility group protein as a fidelity factor that assures selection of the precise transcriptional start site at certain pol III promoters.
The androgen receptor DNA-binding domain determines androgen selectivity of transcriptional response
Authors: Verrijdt G. , Tanner T. , Moehren U. , Callewaert L. , Haelens A. , Claessens F.
Published: November 2006

The AR (androgen receptor) is a hormone-dependent transcription factor that translates circulating androgen hormone levels into a physiological cellular response by directly regulating the expression of its target genes. It is the key molecule in e.g. the development and maintenance of the male sexual characteristics, spermatocyte production and prostate gland development and growth. It is also a major factor in the onset and maintenance of prostate cancer and a first target for pharmaceutical action against the further proliferation of prostate cancer cells. The AR is a member of the steroid hormone receptors, a group of steroid-inducible transcription factors sharing an identical consensus DNA-binding motif. The problem of how specificity in gene activation is achieved among the different members of this nuclear receptor subfamily is still unclear. In this report, we describe our investigations on how the AR can specifically activate its target genes, while the other steroid hormone receptors do not, despite having the same consensus monomeric DNA-binding motif. In this respect, we describe how the AR interacts with a newly identified class of steroid-response elements to which only the AR and not, for example, the glucocorticoid receptor can bind.
Cannabinoids and PPARα signalling
Authors: Sun Y. , Alexander S.P.H. , Kendall D.A. , Bennett A.J.
Published: November 2006

Cannabinoids have been shown to possess anti-inflammatory and neuroprotective properties, which were proposed to occur mainly via activation of the G-protein-coupled receptor CB1 (cannabinoid receptor 1). Recently, certain cannabinoids have been reported to be ligands for members of the nuclear receptor transcription factor superfamily known as PPARs (peroxisome-proliferator-activated receptors). This review summarizes the evidence for cannabinoid activation of PPARs and identifies a new intracellular target for cannabinoids as therapeutic agents for neuroprotective treatment.
The nuclear receptor co-repressor RIP140 controls the expression of metabolic gene networks
Authors: Parker M.G. , Christian M. , White R.
Published: November 2006

NRs (nuclear receptors) regulate the expression of specific gene networks in target cells by recruiting cofactor complexes involved in chromatin remodelling and in the assembly of transcription complexes. The importance of activating gene expression, in metabolic tissues, is well established, but the contribution of transcriptional inhibition is less well defined. In this review, we highlight a crucial role for RIP140 (receptor-interacting protein 140), a transcriptional co-repressor for NR, in the regulation of metabolic gene expression. Many genes involved in lipid and carbohydrate metabolism are repressed by RIP140 in adipose and muscle. The repressive function of RIP140 results from its ability to bridge NRs to repressive enzyme complexes that modify DNA and histones. In the absence of RIP140, expression from many metabolic genes is increased so that mice exhibit a lean phenotype and resistance to high-fat-diet-induced obesity and display increased glucose tolerance and insulin sensitivity. We propose that a functional interplay between transcriptional activators and the co-repressor RIP140 is an essential process in metabolic regulation.
New developments in oestrogen signalling in colonic epithelium
Authors: Wada-Hiraike O. , Warner M. , Gustafsson J.-Å.
Published: November 2006

Epidemiological studies show that oestrogen reduces the risk of colorectal cancer in postmenopausal women and ERβ (oestrogen receptor β)-selective ligands have been reported to be very effective treatment in animal models of inflammatory bowel disease. Several studies have shown that ERβ is the predominant ER in the colonic epithelium, but it is not clear whether the benefit of ERβ agonists in inflammatory bowel disease are due to their action on the colon epithelium itself, or on the immune system. In order to address this issue, we have compared colons of ERβ−/− and wild-type mice with regard to morphology, histology, proliferation and differentiation. We found that the number of proliferating cells was higher in ERβ−/− mice, and the migration of labelled cells from base to lumen of the crypts was faster. Additionally, immunohistochemical staining revealed fewer apoptotic cells (cleaved caspase 3-positive), a significant decrease in expression of the epithelial differentiation marker, cytokeratin CK20, the adherens junction protein, α-catenin, and the hemidesmosomal protein, plectin, in ERβ−/− mice. These findings suggest a role for ERβ in growth, organization and maintenance of the normal colonic crypt–villus architecture. The next step is to elucidate the molecular mechanisms that underlie the signalling of ERβ in normal cell growth and assess whether or not ERβ agonists will be useful drugs in the prevention or treatment of colorectal cancer. Dietary phyto-oestrogens are believed to play a role in protection against colorectal cancer. Lignans, such as enterolactone, an ER agonist, prevent cancer development in animal models. Since ERβ is the only ER in the colon, there is enough reason to speculate that phyto-oestrogens are acting through ERβ.
Multiple chromatin modifications important for gene expression changes in cardiac hypertrophy
Authors: Bingham A.J. , Ooi L. , Wood I.C.
Published: November 2006

Cardiac hypertrophy is an increase in the size of cardiac myocytes to generate increased muscle mass, usually driven by increased workload for the heart. Although important during postnatal development and an adaptive response to physical exercise, excessive hypertrophy can result in heart failure. One characteristic of hypertrophy is the re-expression of genes that are normally only expressed during foetal heart development. Although the involvement of these changes in gene expression in hypertrophy has been known for some years, the mechanisms involved in this re-expression are only now being elucidated and the transcription factor REST (repressor element 1-silencing transcription factor) has been identified as an important repressor of hypertrophic gene expression.
Biodiversity of CYP51 in trypanosomes
Authors: Lepesheva G.I. , Hargrove T.Y. , Ott R.D. , Nes W.D. , Waterman M.R.
Published: November 2006

Sterol 14α-demethylases (CYP51) are metabolic cytochromes P450, found in each biological kingdom. They catalyse a single three-step reaction included in all sterol biosynthetic pathways. Plant CYP51s have strict preference towards their physiological substrate O (obtusifoliol), which is C-4-monomethylated. Natural substrates of animal/fungal CYP51 (lanosterol, 24,25-dihydrolanosterol or 24-methylenelanosterol) are C-4-dimethylated. CYP51 from the pathogenic protozoa TB (Trypanosoma brucei) is the first example of O-specific sterol 14α-demethylase in non-photosynthetic organisms. Surprisingly, at 83% amino acid identity to the TB orthologue, CYP51 from TC (Trypanosoma cruzi) clearly prefers C-4-dimethylated sterols. Replacement of animal/fungi-like Ile105 in the B′ helix of TC CYP51 with phenylalanine, the residue found in this position in all plant and other trypanosome CYP51s, dramatically increases the ability of the enzyme to metabolize O, converting it into a more plant-like sterol 14α-demethylase. A more than 100-fold increase in binding and turnover is observed for the 24-desmethyl analogue of O [N (norlanosterol)], which is found in vivo in procyclic forms of TB and is a good TB CYP51 substrate in vitro. We believe that (i) N is a non-conventional CYP51 substrate, preferred in TB and perhaps other Trypanosomatidae and (ii) functional similarity of TC CYP51 to animal/fungal orthologues is a result of evolutionary convergence (including F105I mutation), leading to different pathways for sterol production in TC versus TB.
Signalling pathways mediating inflammatory responses in brain ischaemia
Authors: Planas A.M. , Gorina R. , Chamorro Á.
Published: November 2006

Stroke causes neuronal necrosis and generates inflammation. Pro-inflammatory molecules intervene in this process by triggering glial cell activation and leucocyte infiltration to the injured tissue. Cytokines are major mediators of the inflammatory response. Pro-inflammatory and anti-inflammatory cytokines are released in the ischaemic brain. Anti-inflammatory cytokines, such as interleukin-10, promote cell survival, whereas pro-inflammatory cytokines, such as TNFα (tumour necrosis factor α), can induce cell death. However, deleterious effects of certain cytokines can turn to beneficial actions, depending on particular features such as the concentration, time point and the very intricate network of intracellular signals that become activated and interact. A key player in the intracellular response to cytokines is the JAK (Janus kinase)/STAT (signal transducer and activator of transcription) pathway that induces alterations in the pattern of gene transcription. These changes are associated either with cell death or survival depending, among other things, on the specific proteins involved. STAT1 activation is related to cell death, whereas STAT3 activation is often associated with survival. Yet, it is clear that STAT activation must be tightly controlled, and for this reason the function of JAK/STAT modulators, such as SOCS (suppressors of cytokine signalling) and PIAS (protein inhibitor of activated STAT), and phosphatases is most relevant. Besides local effects in the ischaemic brain, cytokines are released to the circulation and affect the immune system. Unbalanced pro-inflammatory and anti-inflammatory plasma cytokine concentrations favouring an ‘anti-inflammatory’ state can decrease the immune response. Robust evidence now supports that stroke can induce an immunodepression syndrome, increasing the risk of infection. The contribution of individual cytokines and their intracellular signalling pathways to this response needs to be further investigated.
Neuroprotection and neurosupplementation in ischaemic brain
Authors: Yamashita T. , Deguchi K. , Sawamoto K. , Okano H. , Kamiya T. , Abe K.
Published: November 2006

Possible strategies for treating ischaemic stroke include: (i) neuroprotection (preventing damaged neurons from undergoing apoptosis in the acute phase of cerebral ischaemia), and (ii) neurosupplementation (the repair of broken neuronal networks with newly born neurons in the chronic phase of cerebral ischaemia). In this paper, we review our recent progress in development of these distinct new strategies for treatment of damaged brain following a stroke. Firstly, we investigated the role of endogenous IL-6 (interleukin-6), which is one of the cytokines drastically induced by ischaemic stimuli, by administering IL-6RA (anti-IL-6 receptor monoclonal antibody) to mice. We found that endogenous IL-6 plays a critical role in neuroprotection and that its role may be mediated by STAT3 (signal transducer and activator of transcription-3) activation. Secondly, we studied the endogenous sources of the newly born neurons in the ischaemic striatum by region- and cell-type-specific cell labelling techniques. The results revealed that the SVZ (subventricular zone) is the principal source of the neuronal progenitors that migrate laterally towards the infarcted regions, and differentiate into newly born neurons. Finally, we developed a restorative stroke therapy with a bio-affinitive scaffold, which is an appropriate poly-porous structure releasing bioactive substances such as neurotrophic factor. This bio-affinitive scaffold is able to give an appropriate environment for newly born neurons. In future, we will combine these strategies to develop more effective therapies for treatment of strokes.
Targeting Bid to prevent programmed cell death in neurons
Authors: Culmsee C. , Plesnila N.
Published: November 2006

Sustained progression of neuronal cell death causes brain tissue loss and subsequent functional deficits following stroke or central nervous system trauma and in neurodegenerative diseases. Despite obvious differences in the pathology of these neurological disorders, the underlying delayed neuronal demise is carried out by a common biochemical cell death programme. Mitochondrial membrane permeabilization and subsequent release of apoptotic factors are key mechanisms during this process. Bcl-2 family proteins, e.g. the pro-apoptotic Bid, Bax or Bad and the antiapoptotic Bcl-2, Bcl-XL, play a crucial role in the regulation of this mitochondrial checkpoint in neurons. In particular, cleavage of cytosolic Bid and subsequent mitochondrial translocation have been detected in many paradigms of neuronal cell death related to acute or chronic neurodegeneration. The current review focuses on the emerging role of Bid as an integrating key regulator of the intrinsic death pathway that amplifies caspase-dependent and caspase-independent execution of neuronal apoptosis. Therefore pharmacological inhibition of Bid provides a promising therapeutic strategy in neurological diseases where programmed cell death is prominent.
Protein phosphatases types 2Cα and 2Cβ in apoptosis
Authors: Klumpp S. , Thissen M.-C. , Krieglstein J.
Published: November 2006

This mini-review highlights the involvement of PP2C (protein phosphatase type 2C) family members α and β in apoptosis. The activity of these isoenzymes can be stimulated by unsaturated fatty acids with special structural features, e.g. oleic acid. Those fatty acids capable of activating PP2Cα and PP2Cβ in vitro induce apoptosis in various cell types as shown here for neurons and endothelial cells. Using RNA interference to reduce the amount of PP2Cα and PP2Cβ results in cells significantly less susceptible to the apoptotic effect of oleic acid. Increased endothelial cell death is considered to be an initial step of atherogenesis. Thus activation of PP2C by physiological unbound (‘free’) unsaturated fatty acids (liberated from lipoproteins) could represent a crucial mechanism in the development of atherosclerosis.
Intensity enhancement of the vibrational spectrum of oxygen when attached to a platinum nanocluster
Authors: Seminario Jorge M. , Saenz Lina R.
Published: November 2006

Detecting single molecules is a technical and scientific challenge and requires to increase the number of molecules or their cross section to a radiation field in order to have a detectable signal. We demonstrate for a single molecule of oxygen that, by attaching the molecule to a nanocluster, the molecule signature spectrum is transferred to the larger complex (molecule cluster). Therefore, the detection can focus on the complex, which can have a much larger cross section, rather than on the small molecule. This is based on the concept of signature transfer, which can be used to detect in the cluster several other properties of the attached molecule.
Heat flux measurements and plasma composition
Authors: Makrinich G. , Fruchtman A.
Published: November 2006

Measurements of heat flux into a probe in plasma, combined with measurement of electron temperature, are used to extract information about the plasma composition. In particular, such measurements in oxygen and nitrogen plasmas at a pressure of several millitorrs indicate that these plasmas are composed mostly of molecular ions. The measurement is based on comparing the rates of heating and cooling of a probe during its exposure to and isolation from the plasma flow. The measured heat flux into the negatively biased probe is in good agreement with the calculated heat flux carried by the impinging plasma ions.
Electrically detected magnetic resonance in ion-implanted Si:P nanostructures
Authors: McCamey D. R. , Huebl H. , Brandt M. S. , Hutchison W. D. , McCallum J. C. , Clark R. G. , Hamilton A. R.
Published: November 2006

The authors present the results of electrically detected magnetic resonance (EDMR) experiments on ion-implanted Si:P nanostructures at 5K, consisting of high-dose implanted metallic leads with a square gap, in which phosphorus is implanted at a nonmetallic dose corresponding to 1017cm−3. By restricting this secondary implant to a 100×100nm2 region, the EDMR signal from less than 100 donors is detected. This technique provides a pathway to the study of single donor spins in semiconductors, which is relevant to a number of proposals for quantum information processing.
Spectral separation of the efficiencies of the inside and outside orders of soft-x-ray-extreme-ultraviolet gratings at near normal incidence
Authors: Goray Leonid I. , Seely John F. , Sadov Sergey Yu.
Published: November 2006

It is shown from both a phenomenological study and exact modeling that the reason for the experimentally observed substantial (a few angstroms or nanometers) separation in wavelength between the maxima of the inside (negative numbered) and outside (positive numbered) diffraction orders of a multilayer-coated grating, operating at near normal incidence and close to the Bragg condition in the soft-x-ray and extreme-ultraviolet (EUV) regions, is related to the different angles of deviation of the orders. This wavelength separation is also a feature of uncoated diffraction gratings, although not clearly noticeable. The widely used approximate approach for calculating the absolute efficiency, the product of the relative grating efficiency and the reflectance of its multilayer coating, has until recently been considered accurate enough for the analysis of soft-x-ray and EUV near-normal-incidence multilayer-coated gratings. The inapplicability of this approximation for the analysis of the precise positions and shapes of the efficiency curves for the inside and outside orders, despite the small ratios of wavelength and groove depth to period and the small angles of incidence, is demonstrated using gratings with realistic groove profiles and operating in the EUV region. The rigorous modified integral method (MIM), which is a variant of boundary integral equation methods and is designed for the calculation of the efficiency of multilayer gratings with arbitrary layer thicknesses and boundary shapes (including microroughness) and over a wide wavelength range, is proposed in a general operator formalism. An analysis of a derived simple phenomenological expression and the exact numerical study indicates that the spectral separation between the inside and the outside orders grows with increasing either wavelength, angle of incidence, groove frequency, or diffraction order number ∣m∣. The efficiency modeling carried out with the commercial program PCGRATE-SX, based on the MIM, gave not only the exact values of the spectral separation between the inside and outside orders of Mo4Ru6∕Be, Mo∕Si, and Mo∕Y multilayer-coated gratings with various real groove profiles measured using atomic force microscopy (AFM) but also good agreement with synchrotron radiation measurements, including high orders as well. To determine the shapes and positions of efficiency curves in the soft-x-ray-EUV range of close to normal-incidence bulk and multilayer-coated gratings with real groove profiles (measured by AFM), one should use codes based on rigorous electromagnetic theory such as the MIM. The modeling is important for developing high efficiency and dispersion gratings for high-resolution spectroscopic studies of laboratory, solar, and astrophysical radiation sources.
Secondary shock formation in xenon-nitrogen mixtures
Authors: Hansen J. F. , Edwards M. J. , Froula D. H. , Edens A. D. , Gregori G. , Ditmire T.
Published: November 2006

The expansion of shock waves has been studied in mediums with different opacities and heat capacities, varied in systematic ways by mixing xenon with nitrogen keeping the mass density constant. An initial shock is generated through the brief (5ns) deposition of laser energy (5J) on the tip of a pin surrounded by the xenon-nitrogen mixture. The initial shock is spherical, radiative, with a high Mach number, and it sends a supersonic radiatively driven heat wave far ahead of itself. The heat wave rapidly slows to a transonic regime and when its Mach number drops to ∼2 with respect to the downstream plasma, the heat wave becomes of the ablative type, driving a second shock ahead of itself to satisfy mass and momentum conservation in the heat wave reference frame. The details of this sequence of events depend, among other things, on the opacity and heat capacity of the surrounding medium. Second shock formation is observed over the entire range from 100% Xe mass fraction to 100% N2. The formation radius of the second shock as a function of Xe mass fraction is consistent with an analytical estimate.
Linear and nonlinear analysis of a gyrotron traveling wave amplifier with misaligned electron beam
Authors: Jiao Chongqing , Luo Jirun
Published: November 2006

This paper presents linear and self-consistent nonlinear theories to describe the beam-wave interaction in a gyrotron traveling wave amplifier (gyro-TWA) with a misaligned electron beam. A linear theory based on the linearized Vlasov equations is developed by using Laplace transforms. By setting appropriate initial values of the electron guiding center, the nonlinear theory without misalignment can be used to study the misalignment effect. The two theories are in good agreement in the small-signal region for the gyro-TWA. The effects of beam misalignment on the TE01 mode gyro-TWA operating at the fundamental are discussed and the corresponding physical mechanism is analyzed.
In situ x-ray diffraction measurements of the capillary fountain jet produced via ultrasonic atomization
Authors: Yano Yohko F. , Douguchi Junya , Kumagai Atsushi , Iijima Takao , Tomida Yukinobu , Miyamoto Toshiaki , Matsuura Kazuo
Published: November 2006

In situ x-ray diffraction measurements were carried out for investigating the liquid structure in the ultrasonic fountain jet to consider the mechanism of the “ultrasonic ethanol separation” reported by Sato et al. [J. Chem. Phys. 114, 2382 (2001)]. For pure liquids (water and ethanol), it was found that the high frequency ultrasound does not affect the liquid structure microscopically. For the 20mol% ethanol-water mixture, the estimated ethanol mole fraction in the ultrasonic fountain jet by using the position of the main maximum in the x-ray diffraction profile coincided with that in the reservoir. This result suggests that the ethanol separation is not caused by any distorted liquid structure under the ultrasound irradiation and occurs when or after the generation of the liquid droplet mist.
Drag on a nanotube in uniform liquid argon flow
Authors: Tang Wenzhong , Advani Suresh G.
Published: November 2006

In this work, nonequilibrium molecular dynamics (MD) simulations were performed to investigate uniform liquid argon flow past a carbon nanotube. In the simulation, nanotubes were modeled as rigid cylinders of carbon atoms. Both argon-argon and argon-carbon interactions were calculated based on Lennard-Jones potential. Simulated drag coefficients were compared with (i) published empirical equation which was based on experiments conducted with macroscale cylinders and (ii) finite element (FE) analyses based on Navier-Stokes equation for flow past a circular cylinder using the same dimensionless parameters used in MD simulations. Results show that classical continuum mechanics cannot be used to calculate drag on a nanotube. In slow flows, the drag coefficients on a single-walled nanotube calculated from MD simulations were larger than those from the empirical equation or FE analysis. The difference increased as the flow velocity decreased. For higher velocity flows, slippage on the surface of the nanotube was identified which resulted in lower drag coefficient from MD simulation. This explains why the drag coefficient from MD dropped faster than those from the empirical equation or FE simulation as the flow velocity increased. It was also found that the drag forces are almost equal for single- and double-walled nanotubes with the same outer diameter, implying that inner tubes do not interact with fluid molecules.
Effect of oxygen annealing on Pr0.7Ca0.3MnO3 thin film for colossal electroresistance at room temperature
Authors: Kim D. S. , Lee C. E. , Kim Y. H. , Kim Y. T.
Published: November 2006

We studied an appropriate annealing condition of Pr0.7Ca0.3MnO3 (PCMO) thin film that can show good resistive switching characteristics for resistance random access memory applications and also tried to elucidate the mechanism of the resistive switching of PCMO thin film at room temperature. We could observe that crystal structure of PCMO film was changed by oxygen annealing. From x-ray photoelectron spectroscopy measurements, we can conclude that the excess of oxygen by oxygen annealing of PCMO film leads to an increase of Mn4+ content at the PCMO surface with a subsequent change in the Mn4+∕Mn3+ ratio at the PCMO surface. The resistance ratio of high resistance state and low resistance state was increased by oxygen annealing of PCMO thin film. This can be explained as follows. The change of the Mn4+∕Mn3+ ratio at the PCMO surface by oxygen annealing leads to the change of characteristics of Au-PCMO interface domain and therefore results in the change of the resistance ratio.
Structure of a pentacene monolayer deposited on SiO2: Role of trapped interfacial water
Authors: Wo Songtao , Wang Binran , Zhou Hua , Wang Yiping , Bessette Jonathan , Headrick Randall L. , Mayer Alex C. , Malliaras George G. , Kazimirov Alexander
Published: November 2006

In situ synchrotron x-ray reflectivity is used to probe the early stages of pentacene growth in real time, under conditions relevant to the fabrication of organic thin film transistors. The results reveal that there is an interfacial water layer initially present on the SiO2 substrate and that this water layer is still present at the interface after the deposition of a pentacene thin film. The thickness of the trapped interfacial water layer does not significantly change subsequent to film deposition, even after exposure to atmospheric pressure or during vacuum annealing at 70°C. However, a water layer is observed to form on the free surface of pentacene after sufficient exposure to water vapor, and the thickness of this layer can be reduced by subsequent vacuum annealing. These observations are correlated with organic thin film transistor mobilities measured at atmospheric pressure versus under vacuum.
Water flow in poly(N-isopropylacrylamide) gels
Authors: Suzuki Atsushi , Yoshikawa Muneyuki
Published: November 2006

Friction between a polymer network of poly(N-isopropylacrylamide) gels and solvent water was investigated. The gel was mechanically constrained in a glass capillary at gelation, and hydrostatic pressure was directly applied to the cross section of the cylinder. The temperature dependence of the flow velocity was extensively measured in the vicinity of the transition temperature for gels with different lengths, l0, at gelation. As the temperature increased, the friction slightly decreased at the transition point and increased rapidly in the collapsed phase. Although the flow velocity depended on l0, the friction in the vicinity of the transition point was well scaled by l0 based on the Hagen-Poiseuille equation for the flux of water flow in a capillary. The results suggested that the assumption that the gel is a bundle of microcapillaries was applicable to the water flow through the hydrogel, which was largely deformed not only by the pressure applied to the solvent but also by the shrinking force caused by the temperature increment. Macroscopic deformation did not affect the friction between the three-dimensional polymer network and water.
Spectromicroscopic evidence for epitaxial poly-Si thin film formed on amorphous Si substrate by nickel induced lateral crystallization
Authors: Hong Ie-Hong , Hsu Ting-Chang , Yen Shang-Chieh , Lin Fu-Shiang , Huang Mao-Lin , Chen Chia-Hao
Published: November 2006

The spatial variations in the chemical composition and electronic structure of nickel metal induced lateral crystallization (Ni-MILC) of amorphous silicon film with in situ vacuum annealing were investigated by scanning photoelectron spectromicroscopy. Lateral chemistry variations of the Ni-MILC of amorphous silicon were directly imaged. Via a system study of the correlation between the core and valence level spectra, the nature of chemical bonding for the different chemical phases was examined. Our results clearly show that the Ni-MILC in UHV leads to the formation of a high-crystallinity poly-Si film, which was laterally grown over ∼20μm at 500°C for 1h.
Computer investigations on the mechanism of the influence of quencher concentration on the rate of simple bimolecular reaction
Authors: Litniewski Marek
Published: November 2006

Molecular dynamics investigations on the influence of the concentration of B (quencher) on the rate coefficient, k(t), for the reaction A+B→C+B are continued [M. Litniewski, J. Chem. Phys. 123, 124506 (2005); 124, 114501 (2006)]. The problem is investigated by analyzing the excess in the two-particle probability density function and in its radial moments. The simulations have been performed for the deterministic systems as gas and liquid as well as for the Brownian system. The influence of moderate changes of the reaction radius resulting in changes of the activation energy has been also considered. The most important result is that the excess in k(t) may be not only a direct consequence of fluctuations in concentrations. For the gas, the excess in the mean radial velocity of A towards B dominated over the excess in the value of the probability density function. As a result, the excess in k(t) was negative in spite of the excess in the relative spatial correlations between A and B was positive. The excess in the mean radial velocity was completely unimportant for dense liquids and the Brownian system.
Probing dielectrophoretic force fields with metallic carbon nanotubes
Authors: Marquardt Christoph W. , Blatt Sabine , Hennrich Frank , Löhneysen Hilbert v. , Krupke Ralph
Published: November 2006

The authors show that single-walled carbon nanotubes are effective probes for dielectrophoretic force fields by studying their deposition pattern on surfaces. Different force fields were generated by electrodes on insulating oxides, with or without conducting substrates underneath. The patterns were recorded by scanning electron microscopy and simulated by finite element calculations. The data show that a sign change of the normal component of the dielectrophoretic force close to the substrate surface can lead to a repulsion of metallic carbon nanotubes from the surface. The authors present geometrical constraints to avoid such a sign change in the dielectrophoretic force.
Comment on “Optical characterization of CuIn1−xGaxSe2 alloy thin films by spectroscopic ellipsometry” [J. Appl. Phys. 94, 879 (2003)]
Authors: Han Sung-Ho , Levi Dean
Published: November 2006

A method to determine the optical functions of thin-film CuIn1−xGaxSe2 alloys was provided in the paper “Optical characterization of CuIn1−xGaxSe2 alloy thin films by spectroscopic ellipsometry.” The optical functions were obtained and the effect of Ga content on the electronic transitions of CuIn1−xGaxSe2 was discussed. We indicate the mistake of their method in determining the critical point energies and discuss the reason for using standard analytic line shape, ϵ̃(ω)=C−Aeiϕ(ω−E+iΓ)n, in this comment.
Epitaxial growth and the magnetic properties of orthorhombic YTiO3 thin films
Authors: Chae S. C. , Chang Y. J. , Seo S. S. A. , Noh T. W. , Kim D.-W. , Jung C. U.
Published: November 2006

High-quality YTiO3 thin films were grown on LaAlO3 (110) substrates at low oxygen pressures (⩽10−8Torr) using pulsed laser deposition. The in-plane asymmetric atomic arrangements at the substrate surface allowed the authors to grow epitaxial YTiO3 thin films, which have an orthorhombic crystal structure with quite different a- and b-axis lattice constants. The YTiO3 film exhibited a clear ferromagnetic transition at 30K with a saturation magnetization of about 0.7μB∕Ti. The magnetic easy axis was found to be along the [1−10] direction of the substrate, which differs from the single crystal easy axis direction, i.e., [001].
Low-operating-voltage pentacene field-effect transistor with a high-dielectric-constant polymeric gate dielectric
Authors: Kim Se Hyun , Yang Sang Yoon , Shin Kwonwoo , Jeon Hayoung , Lee Jong Won , Hong Ki Pyo , Park Chan Eon
Published: November 2006

Low-operating-voltage organic field-effect transistor has been realized by using the cross-linked cyanoethylated poly(vinyl alcohol) (CR-V) as a gate dielectric. The cross-linked CR-V dielectric was found to have a high dielectric constant of 12.6 and good insulating properties, resulting in a high capacitance (92.9nF∕cm2 at 20Hz) for a dielectric thickness of 120nm. A pentacene field-effect transistor fabricated with the cross-linked CR-V dielectric was found to exhibit a high carrier mobility (0.62cm2∕Vs), a small subthreshold swing (185mV∕decade), and little hysteresis at low operating voltages (⩽−3V).
Effects of gate bias on hot-carrier reliability in drain extended metal-oxide-semiconductor transistors
Authors: Wu K. M. , Chen J. F. , Su Y. K. , Lee J. R. , Lin K. W. , Shih J. R. , Hsu S. L.
Published: November 2006

The effect of gate voltage on hot-carrier induced degradation in drain extended high-voltage metal-oxide-semiconductor (MOS) transistors with thick gate oxide (100nm) structure is presented. Different from the conventional low-voltage n-type MOS transistors, under a fixed drain voltage, devices stressed at a higher Vgs result in a greater maximum transconductance and on-resistance degradation. Under higher Vgs, the increase in channel hot-carrier injection is responsible for the greater Gm,max degradation. On the other hand, Kirk effect induced increase in drain avalanche hot carriers near the drain as well as higher electric field in the channel is responsible for the greater Ron degradation.
Photoluminescence properties of high-pressure-polymerized C60 nanorods in the orthorhombic and tetragonal phases
Authors: Hou Yuanyuan , Liu Bingbing , Wang Lin , Yu Shidan , Yao Mingguang , Chen Ao , Liu Dedi , Cui Tian , Zou Guangtian , Iwasiewicz Agnieszka , Sundqvist Bertil
Published: November 2006

C 60 nanorods in two polymeric phases have been synthesized under different high pressure and high temperature conditions. Orthorhombic and tetragonal phases have been identified from Raman spectra. The rod shape can be kept under quasihydrostatic pressure. The photoluminescence intensity of the polymeric C60 nanorods has been greatly enhanced compared with that of pristine C60 nanorods. The main fluorescence band shifted from 730nm in the unpolymeric phase to 748nm and near infrared 780nm in the orthorhombic and tetragonal phases, respectively. The enhanced photoluminescence with tunable frequency for different polymeric C60 nanorods suggests potential applications in luminescent nanomaterials.
Performance of an electro-optic waveguide modulator fabricated using a deoxyribonucleic-acid-based biopolymer
Authors: Heckman Emily M. , Grote James G. , Hopkins F. Kenneth , Yaney Perry P.
Published: November 2006

An electro-optic (EO) planar waveguide modulator using a deoxyribonucleic acid (DNA)-based biopolymer for both the waveguide core and cladding layers has been fabricated and its performance evaluated. A cross-linked DNA-surfactant biopolymer was used for the top and bottom cladding layers and the core layer was a cross-linked DNA-surfactant biopolymer with 3wt% Disperse Red 1. The EO coefficient r33 was induced through contact poling. The fabricated device was found to exhibit EO modulating behavior. Using an estimated value of r33=0.5pm∕V, a sine-squared fit to the modulating data was obtained with Vπ=263V±10%.
Switching of magnetic domains in Permalloy microstructures using two-dimensional electron gas
Authors: Belkin A. , Fedor J. , Pankowski P. , Iavarone M. , Novosad V. , Karapetrov G. , Cambel V. , Gregušová D. , Kúdela R.
Published: November 2006

The authors demonstrate the ability to monitor and alter the magnetization state of microscopic Permalloy element deposited on the active area of a two-dimensional electron gas (2DEG) Hall probe using the current through the 2DEG. Magnetic force microscopy imaging shows the exact magnetization state of the Permalloy thin film ellipse at different applied magnetic fields. Recorded Hall voltage signal provides information on local magnetization of the ferromagnetic element at the same time. Application of short, but intense current pulses through the Hall probe changes the magnetization state of the Permalloy ellipse.