bluuebunny/crossref_metadata_2025 huggingface dataset:
Signs of Life: Engraved Stone Artefacts from Neolithic South India
Authors: Brumm Adam , Boivin Nicole , Fullagar Richard
Published: June 2006

While exceedingly rare on any given archaeological site, engraved stone artefacts have nonetheless been reported from sites covering a range of periods and regions across the world. Attempts to interpret such engravings have often focused on potential representational or communicative functions, including their role in notational systems, symbolic depiction, and the development of early forms of writing. Contextual and microscopic investigation of a number of engraved artefacts discovered in a large assemblage of dolerite artefacts excavated from a Neolithic hilltop habitation and stone-tool production site in south India suggests, however, that an alternative interpretation of engraved stone artefacts is possible. Drawing on ethnographic evidence concerning the perception of stone, and particularly natural markings on stone, this article argues that the stone pieces on which the marks were engraved were more than just passive surfaces for the creation of unrelated signs. Instead, engravings appear to draw on natural features within and upon the surface of the dolerite, and to suggest an appreciation for the patterns of nature, as well as a lack of distinction between anthropogenic and natural markings. It is argued that the engravings may have been a response to a perceived 'life-force' within the dolerite. The fact that they were produced and then broken apart by knapping suggests that they may have been made to accentuate or attenuate a power that was perceived as either somehow beneficial or in need of careful control.
The ‘Solarization’ of the Moon: Manipulated Knowledge at Stonehenge
Authors: Sims Lionel
Published: June 2006

Recent archaeological research now views the northwest European Neolithic and Early Bronze Age as a period of separation from a resilient complex of traditions of Mesolithic and even Palaeolithic origin. Extending this insight to recent findings in archaeoastronomy, this article treats the sarsen monument at Stonehenge as one among a number of monuments with lunar–solar alignments which privileged night over day, winter over summer, dark moon over full. The aim of the monument builders was to juxtapose, replicate and reverse certain key horizon properties of the sun and the moon, apparently with the intention of investing the sun with the moon's former religious significance. This model is consistent with both current archaeological interpretations of burial practices associated with the monument, and with recent anthropological modelling of hunter-gatherer cultural origins.
Shrine Franchising and the Neolithic in the British Isles: Some Observations based upon the Tallensi, Northern Ghana
Authors: Insoll Timothy
Published: June 2006

Ethnography of the Tallensi shows how rights of access to shrines could be granted to people in other places and how beneficiaries may take with them samples of stone used at the mother shrine. Reasons for taking the samples are considered. It is suggested that Tallensi practice offers an analogy for selection and transfer of stone in the Neolithic of Britain and Ireland.
Beyond Skin: Layering and Networking in Art and Archaeology
Authors: Carl Knappett
Published: June 2006

This article puts forward two modes through which cognition and agency exist beyond skin: ‘layering’ and ‘networking’. These bodily and artefactual processes are broadly equivalent to two fundamental social practices defined by Chapman (2000) — accumulation and enchainment, respectively. While the aim of the article is to develop theoretical frameworks for application in archaeological settings, the themes encountered have wider relevance to material culture as a whole. Examples are taken from modern and contemporary art, notably the work of Marcel Duchamp and Antony Gormley.
Acute mesenteric ischaemia, a highly lethal disease with a devastating outcome
Authors: Safioleas  , Moulakakis  , Papavassiliou  , Kontzoglou  , Kostakis
Published: June 2006

Background: Acute mesenteric ischaemia remains a serious condition requiring emergency surgical management. The mortality rate still remains high, due to the unspecific and delayed diagnosis and ranges from 59% to 100%. Purpose of our study is to present our experience in the management of the disease. Patients and methods: This is a retrospective study of 61 patients treated surgically for acute mesenteric ischaemia, between 1988 and 2004. All patients underwent a laparotomy. 75% of the patients were operated within the first 24 hours and the rest within 48 hours. Results: Superior mesenteric artery embolism occurred in 36 (59%), thrombosis in 21 (34%) and superior mesenteric vein thrombosis in 4 (7%) cases. In 49 (80%) cases, embolectomy or thrombectomy of the superior mesenteric artery with resection of the necrotic segment of the bowel was performed. Twelve cases (20%) were considered inoperable because of massive bowel necrosis. According to our study mortality and morbidity rate amounts to 75% and 80% respectively. No significant difference in the mortality rate between patients with embolism (75%) and thrombosis (76%) was found. However a significant increase of mortality rate was observed when the surgical intervention became afterwards the first 24-hour period. (72% versus 87%). Patients who underwent embolectomy or thrombectomy with bowel resection presented an improved survival rate compared with patients that underwent only bowel resection. (p = 0.019) Conclusions: Acute mesenteric ischaemia has the characteristics of a highly lethal condition and only early recognition and appropriate treatment can reduce the potential for a devastating outcome. The reduction of time interval from the beginning of symptoms up to the treatment remains the main critical important factor.
Duplex scanning compared with intra-arterial angiography in diagnosing peripheral arterial disease: three analytical approaches
Authors: Krnic  , Vucic  , Sucic
Published: June 2006

Background: This study was undertaken to assess the reliability of duplex scanning, as compared with digital subtraction angiography, in diagnosing peripheral arterial disease of the lower limbs. Patients and methods: 60 legs were studied. Each leg was divided in 5 arterial segments, from aortoiliac to popliteal. Duplex scanning and digital subtraction angiography were performed. The disease in each segment was assessed as significant or insignificant or classified into five categories concerning the grade of stenosis (patent vessel or no diameter reduction, mild stenosis, i.e. 1–19% diameter reduction, moderate and severe stenosis, i.e. 20–49% and 50–99% diameter reduction, respectively, and occluded vessel). Three statistical approaches were applied: calculating sensitivity and specificity, Kappa statistics, and weighted Kappa value. Median grades of arterial stenosis across different segments, according to angiography measurements, were also calculated. Results: The duplex sensitivity in detecting significant lesions ranged from 0.46 to 0.88. The Kappa values of agreement between duplex and angiography ranged from 0.35 to 0.64. Weighted Kappa values ranged from 0.45 to 0.72. Median grades of arterial lesions ranged from 2 (interquartile range 1–2) to 4 (3–4) and differed significantly (Kruskal-Wallis H test, p < 0.001). Conclusions: The sensitivities and specificities suggested various duplex reliabilities in detecting significant arterial disease across different lower limbs segments. The Kappa values, in general, testified duplex’s insufficient accuracy in grading the severity of stenosis. However, weighted Kappa values confirmed duplex’s better ability to approximate the grade of stenosis. The arterial segments themselves were unevenly affected with the peripheral arterial disease.
Antiplatelet therapy prior to carotid endarterectomy – still room for improvement
Authors: Assadian  , Eidher  , Senekowitsch  , Rotter  , Löchli  , Hagmüller  , Knöbl
Published: June 2006

Background: Antiplatelet therapy is one of the most important modalities for secondary prevention of ischemic events. The aim of this prospective study was to evaluate the current practice of antiplatelet therapy in patients with high grade stenosis of the internal carotid artery (ICA), who were referred by neurologists, stroke physicians and cardiologists for carotid endarterectomy. Patients and methods: Patients referred to our department for carotid endarterectomy with ICA stenosis (> 70% according to NASCET criteria) were prospectively evaluated regarding atherosclerosis risk factors and current antiplatelet therapy. During a 7 month period, 235 patients were scheduled for carotid endarterectomy. Their mean age was 70 years (range 42 years to 95 years), 91 patients were female (39%), 144 male (61%). 122 patients (52%) had a symptomatic ICA stenosis, 113 (48%) an asymptomatic ICA stenosis. Results: Of the 235 patients, 29 were either on low molecular weight heparin or vitamin K antagonists for reasons other than ICA stenosis and were therefore excluded from analysis. Therefore, 206 patients (88%) were evaluated for antiplatelet therapy prescribed by their admitting physicians. Of these patients, 77 (37%) (42 (41%) symptomatic and 35 (34%) asymptomatic patients) did not receive any antithrombotic therapy prior to admission for surgery. The majority of patients received aspirin preoperatively (106 patients, 51.5%) 13 (6%) patients were on clopidogrel and 10 (5%) on dual therapy with Aspirin and clopidogrel. Conclusions: More than one third of patients awaiting carotid endarterectomy did not receive any antiplatelet therapy, despite high grade ICA stenosis. Since this practice does not meet the current guidelines, campaigns to increase the awareness of this problem are urgently needed.
Direct retrieval of stratospheric CO2 infrared cooling rate profiles from AIRS data
Authors: Feldman D. R. , Liou K. N. , Yung Y. L. , Tobin D. C. , Berk A.
Published: June 2006

We expand upon methods for retrieving thermal infrared cooling rate profiles, originally developed by Liou and Xue (1988) through application to the inversion of the stratospheric cooling rate produced by carbon dioxide (CO2) and a formal description of the associated error budget. Specifically, we infer lower‐ and mid‐stratospheric cooling rates from the CO2 ν2 band on the basis of selected spectral channels and available data from the Atmospheric Infrared Sounder (AIRS). In order to establish the validity of our results, we compare our retrievals to those calculated from a forward radiative transfer program using retrieved temperature data from spectra taken by the Scanning High‐Resolution Interferometer Sounder (S‐HIS) on two aircraft campaigns: the Mixed‐Phase Arctic Cloud Experiment (MPACE) and the Aura Validation Experiment (AVE) both in Fall, 2004. Reasonable and consistent comparisons are illustrated, revealing that spectral radiance data taken by high‐resolution infrared sounders can be used to determine the vertical distribution of radiative cooling due to CO2.
Impact of open ocean influence on a coastal model: The 1997–1998 El Niño off central California
Authors: Wang Dong‐Ping , Ohashi Kyoko
Published: June 2006

Extensive moored current meters, atmospheric observations, and hydrographic surveys were obtained off central California during the 1997–1998 El Niño. In this study the temperature observations from current meter moorings and hydrographic surveys are assimilated into a coastal ocean model to study the seasonal circulation in the Santa Barbara Channel–Santa Maria Basin (SBC‐SMB). Mean coastal circulation was dominated by a poleward jet in fall 1997 at the peak of the El Niño but returned to the normal surface convergent pattern in fall 1998. The data‐assimilated model reproduces well the observed flow patterns in both years. The interannual flow variability is examined through sensitivity analysis of the effects of local forcing and open ocean influence. It is shown that the poleward jet is associated with enhanced California Countercurrent during El Niño, while the surface convergence is driven by local wind stress curl. Taking advantage of the extensive data set, the climatology is compared with the synoptic states. It is found that the climatology could cause significant negative impact.
Magnetic and structural constraints for the noncylindrical evolution of a continental forebulge (Hyblea, Italy)
Authors: Billi Andrea , Porreca Massimiliano , Faccenna Claudio , Mattei Massimo
Published: June 2006

The Hyblean Plateau in southeastern Sicily, Italy, consists of an isolated and elevated forebulge structure formed since the early Miocene time by bending the foreland lithosphere below the advancing Maghrebian thrust‐fold belt. The Hyblean forebulge is presently located in front of an orogenic recess and partly surrounded by two orogenic salients. We analyzed magnetic (anisotropy of magnetic susceptibility) and structural (joints, faults, slickenside lineations, and bed attitudes) fabric data from Neogene carbonate rocks exposed atop the Hyblean forebulge. Results showed unidirectional fabrics developed in response to a NW‐SE extension at the end the of early Miocene time and beginning of middle Miocene time, and duple‐to‐multiple fabrics developed in response to major NW‐SE and NE‐SW extensions from the Langhian time onward. We interpreted these results as the evidence for the growth of a doubly plunging forebulge due to the presence of foreland crustal heterogeneities, which enhanced differential retreating processes of the foreland along the subduction zone and the subsequent formation of orogenic salients and recesses. A semianalytical model shows that the observed brittle deformations potentially involved a significant thickness of the carbonate sedimentary cover, thereby reducing the lithosphere flexural rigidity and enhancing its bending aptitude.
Impact of hydroclimatic fluctuations on the soil water balance
Authors: Daly E. , Porporato A.
Published: June 2006

We analyze the propagation of daily fluctuations in rainfall and potential evapotranspiration to soil moisture dynamics, using a stochastic model that accounts for these two different forms of hydroclimatic variability. The pulsing, intermittent behavior of daily precipitation is described by a compound Poisson process that models the unpredictability of both frequency and amount of rainfall events, while fluctuations in potential evapotranspiration that act continuously in time are assumed to be Gaussian. The resulting model for the soil water balance is thus a stochastic differential equation, forced by a state‐dependent compound Poisson noise and a multiplicative Gaussian noise. Steady state probability distribution functions (pdfs) of soil moisture are obtained analytically along with the equations for the expected water balance and its variability. The multiplicative effect of temporal fluctuations in potential evapotranspiration on soil moisture reduces the soil water losses caused by evapotranspiration compared to the case when they are not present. Most importantly, the analysis also shows that because of their different forms and state dependence the impact of rainfall variability on soil moisture dynamics is much more significant than that of potential evapotranspiration, the fluctuations of which do not affect appreciably the soil moisture statistical properties.
Viroids: an Ariadne's thread into the RNA labyrinth
Authors: Daròs José‐Antonio , Elena Santiago F , Flores Ricardo
Published: June 2006

Viroids are structurally, functionally and evolutionarily different from viruses. Despite their small, non‐protein‐encoding, single‐stranded circular RNA genome, viroids can infect higher plants and cause certain diseases. Members of the two viroid families, Pospiviroidae and Avsunviroidae, have evolved to usurp the transcriptional machinery of their host nuclei and chloroplasts, respectively, in which replication proceeds through a rolling‐circle mechanism involving RNA polymerization, cleavage and ligation. Remarkably, viroids subvert certain DNA‐dependent RNA polymerases to transcribe RNA templates, and, in the family Avsunviroidae, post‐transcriptional cleavage is catalysed by hammerhead ribozymes. Viroids are models for studying RNA evolution and for analysing RNA transport in plants, because they can move intracellularly, intercellularly through plasmodesmata and to distal parts of the plant through the vascular system. Viroids elicit RNA‐silencing phenomena, which might mediate some of their biological properties, including pathogenesis. As some viroids behave as catalytic RNAs, they are regarded as remnants of the RNA world.
Nature of the breakdown in the Stokes-Einstein relationship in a hard sphere fluid
Authors: Kumar Sanat K. , Szamel Grzegorz , Douglas Jack F.
Published: June 2006

Molecular dynamics simulations of high density hard sphere fluids clearly show a breakdown of the Stokes-Einstein equation (SE). This result has been conjectured to be due to the presence of mobile particles, i.e., ones which have the propensity to “hop” distances that are integer multiples of the interparticle distance. We conclusively show that the sedentary particles, i.e., ones complementary to the “hoppers,” obey the SE relationship to a good approximation, even though the fluid as a whole violates the SE equation at high densities. These results support the notion that the unusual diffusive behavior of supercooled liquids is dominated by the hopping particles.
Assessment of a simple correction for the long-range charge-transfer problem in time-dependent density-functional theory
Authors: Neugebauer Johannes , Gritsenko Oleg , Baerends Evert Jan
Published: June 2006

The failure of the time-dependent density-functional theory to describe long-range charge-transfer (CT) excitations correctly is a serious problem for calculations of electronic transitions in large systems, especially if they are composed of several weakly interacting units. The problem is particularly severe for molecules in solution, either modeled by periodic boundary calculations with large box sizes or by cluster calculations employing extended solvent shells. In the present study we describe the implementation and assessment of a simple physically motivated correction to the exchange-correlation kernel suggested in a previous study [O. Gritsenko and E. J. Baerends J. Chem. Phys. 121, 655 (2004)]. It introduces the required divergence in the kernel when the transition density goes to zero due to a large spatial distance between the “electron” (in the virtual orbital) and the “hole” (in the occupied orbital). A major benefit arises for solvated molecules, for which many CT excitations occur from solvent to solute or vice versa. In these cases, the correction of the exchange-correlation kernel can be used to automatically “clean up” the spectrum and significantly reduce the computational effort to determine low-lying transitions of the solute. This correction uses a phenomenological parameter, which is needed to identify a CT excitation in terms of the orbital density overlap of the occupied and virtual orbitals involved. Another quantity needed in this approach is the magnitude of the correction in the asymptotic limit. Although this can, in principle, be calculated rigorously for a given CT transition, we assess a simple approximation to it that can automatically be applied to a number of low-energy CT excitations without additional computational effort. We show that the method is robust and correctly shifts long-range CT excitations, while other excitations remain unaffected. We discuss problems arising from a strong delocalization of orbitals, which leads to a breakdown of the correction criterion.
Photoionization of helium nanodroplets doped with rare gas atoms
Authors: Kim Jeong Hyun , Peterka Darcy S. , Wang Chia C. , Neumark Daniel M.
Published: June 2006

Photoionization of He droplets doped with rare gas atoms (Rg=Ne, Ar, Kr, and Xe) was studied by time-of-flight mass spectrometry, utilizing synchrotron radiation from the Advanced Light Source from 10to30eV. High resolution mass spectra were obtained at selected photon energies, and photoion yield curves were measured for several ion masses (or ranges of ion masses) over a wide range of photon energies. Only indirect ionization of the dopant rare gas atoms was observed, either by excitation or charge transfer from the surrounding He atoms. Significant dopant ionization from excitation transfer was seen at 21.6eV, the maximum of He 2pP1 absorption band for He droplets, and from charge transfer above 23eV, the threshold for ionization of pure He droplets. No Ne+ or Ar+ signal from droplet photoionization was observed, but peaks from HenNe+ and HenAr+ were seen that clearly originated from droplets. For droplets doped with Rg=Kr or Xe, both Rg+ and HenRg+ ions were observed. For all rare gases, Rg2+ and HenRgm+ (n,m⩾1) were produced by droplet photoionization. Mechanisms of dopant ionization and subsequent dynamics are discussed.
Frequency stabilized radio-frequency generator for driving ion traps and other capacitive loads
Authors: Chang B. T. , Mitchell T. B.
Published: June 2006

We report the design and performance of a simple radio-frequency generator, suitable for driving capacitive loads such as ion traps in the few to thousand picofarad range. The oscillation frequency can be phase locked to an external reference oscillator, providing excellent frequency stabilization. Amplitude control circuits allow the oscillations to be rapidly started and stopped.
Confocal three dimensional tracking of a single nanoparticle with concurrent spectroscopic readouts
Authors: Cang Hu , Wong Chung M. , Xu C. Shan , Rizvi Abbas H. , Yang Haw
Published: June 2006

We present an apparatus that noninvasively tracks a moving nanoparticle in three dimensions while providing concurrent sequential spectroscopic measurements. The design, based on confocal microscopy, uses a near-infrared laser and a dark-field condenser for illumination of a gold nanoparticle. By monitoring the scattered light from the nanoparticle and using a piezoelectric stage, the system was able to continuously bring the diffusive particle in a glycerol/water solution back to the focal volume with spatial resolution and response time of less than 210nm and a millisecond, respectively.
Guided wave transduction experiment using a circular magnetostrictive patch and a figure-of-eight coil in nonferromagnetic plates
Authors: Cho Seung Hyun , Lee Ju Seung , Kim Yoon Young
Published: June 2006

When an alternating magnetic field by a figure-of-eight coil is applied to a circular magnetostrictive patch bonded to a plate, ultrasonic guided waves can be effectively generated and measured. Wave experiments with two transducers consisting of the coil and the patch show that the magnitude and type of the measured waves depend on the magnetic field directions of the wave transmitting and receiving coils; a first-order theory was derived to explain the direction-dependent phenomena. The relation between the patch size and the frequency of the maximum signal output was also investigated.
Unified equation for the strength of bulk metallic glasses
Authors: Yang B. , Liu C. T. , Nieh T. G.
Published: June 2006

In the present study, a conceptual approach to evaluate the strength of metallic glass systems is proposed from a free volume point of view. Based on the physical analogy between the plastic deformation and glass transition, the strength of amorphous structures was found to depend on both the localized shear mechanism and the atomic cohesive energy. Interestingly, we find that the strength at the ambient temperature (T0) can be determined by the glass transition temperature (Tg) and molar volume (V), and can be specifically predicted by a unified parameter of (Tg−T0)∕V. The predicted strength was unambiguously verified from experimental data reported for a number of metallic glass systems.
Terahertz radiation emission from GaMnAs
Authors: Héroux J. B. , Ino Y. , Kuwata-Gonokami M. , Hashimoto Y. , Katsumoto S.
Published: June 2006

Terahertz radiation is observed from ferromagnetic GaMnAs samples excited with 400nm wavelength pump pulses and is related to the sample magnetization M. The emission can be explained by the strong influence of M on the photogenerated carrier motion, a phenomenon related to the dc anomalous Hall effect. Results illustrate the potential of ferromagnetic materials to be used as compact terahertz sources emitting in a direction normal to the surface.
Photoemission study of the poly(3-hexylthiophene)/Au interface
Authors: Lyon J. E. , Cascio A. J. , Beerbom M. M. , Schlaf R. , Zhu Y. , Jenekhe S. A.
Published: June 2006

The interface between the conjugated polymer poly(3-hexylthiophene) (P3HT) and Au was investigated using photoemission spectroscopy. Electrospray thin film deposition was used to deposit P3HT on a polycrystalline Au thin film in several steps without breaking the vacuum. In between deposition steps, x-ray photoemission spectroscopy and ultraviolet photoemission spectroscopy measurements were carried out. The resulting series of spectra allowed the determination of the orbital lineup at the interface. The results indicate that the P3HT interface has a smaller hole injection barrier (0.59eV) than comparably structured oligothiophene contacts.
Universal single-phonon variable range hopping conduction for inorganic semiconducting polycrystalline films
Authors: Myong Seung Yeop , Lim Koeng Su
Published: June 2006

Mott [Philos. Mag. 19, 835 (1969)] established the single-phonon variable range hopping conduction from occupied to unoccupied localized states in disordered materials at low temperatures by assuming a constant localized density of states at the Fermi level. However, recent researches have reported that this behavior can also be observed in the polycrystalline films with an exponential tail state distribution in the gap. If the carrier concentration is lower than a critical value for a semiconductor-to-metal transition, in a low temperature region polycrystalline films exhibit percolation hopping through band tail states with an exponential distribution. We revisit various hopping conductions for inorganic semiconducting polycrystalline films.
Direct imaging of propagation and damping of near-resonance surface plasmon polaritons using cathodoluminescence spectroscopy
Authors: van Wijngaarden J. T. , Verhagen E. , Polman A. , Ross C. E. , Lezec H. J. , Atwater H. A.
Published: June 2006

Cathodoluminescence imaging spectroscopy is used to determine the propagation distance of surface plasmon polaritons near the surface plasmon resonance on both silver and gold films. Surface plasmon polaritons are generated by a focused (diameter of 5nm) electron beam spot in the metal and coupled out through a grating. By gradually varying the distance between the excitation spot and the grating the damping is probed. Propagation lengths as small as several hundred nanometers are probed, and an increase in propagation length is observed if the wavelength is increased above resonance. The measured data are compared with the calculated propagation lengths taking into account both absorption in the film and leakage radiation, and it is found that other loss mechanisms appear to be significant as well.
Comparison of epitaxial thin layer GaN and InP passivations on InGaAs∕GaAs near-surface quantum wells
Authors: Aierken A. , Riikonen J. , Sormunen J. , Sopanen M. , Lipsanen H.
Published: June 2006

The optical properties of the in situ epitaxial GaN and InP passivated InGaAs∕GaAs near-surface quantum wells, which were fabricated by metal organic vapor phase epitaxy, are investigated. Low-temperature photoluminescence (PL), time-resolved photoluminescence, and photoreflectance are used to study the passivation effect. Both GaN and InP passivations are observed to significantly enhance the PL intensity and carrier lifetime and to reduce the surface electrical fields. Comparison of the methods shows that the epitaxial InP passivation is more effective. However, epitaxial GaN and nitridation methods are comparable with InP passivation.
Impact of Zr addition on properties of atomic layer deposited HfO2
Authors: Triyoso D. H. , Hegde R. I. , Schaeffer J. K. , Roan D. , Tobin P. J. , Samavedam S. B. , White B. E. , Gregory R. , Wang X.-D.
Published: June 2006

The impact of Zr addition on microstructure of HfO2 after high temperature processing was investigated using Rutherford backscattering, x-ray diffraction (XRD), transmission electron microscopy, and atomic force microscopy (AFM). The ZrO2 content in the films was varied from ∼25% to 75%. XRD analysis shows that adding >50% ZrO2 leads to partial stabilization of tetragonal phase of the HfxZr1−xO2 alloy. AFM images revealed smaller grains with Zr addition. Conducting AFM showed more uniform and tighter tunneling current distribution in HfxZr1−xO2 compared to HfO2. Constant capacitance-voltage stressing performed on HfO2 and HfxZr1−xO2 metal-oxide-semiconductor capacitors indicated reduced charge trapping with Zr addition.
Controlled assembly of polymer nanofibers: From helical springs to fully extended
Authors: Shin Min Kyoon , Kim Sun I. , Kim Seon Jeong
Published: June 2006

We describe simple procedures for fabricating single polymeric helical nanofibers and converting these helical nanofibers into linearly oriented nanofibers using a modified electric field in an electrospinning system. Helical structures were made from a solution of poly(2-acrylamido-2-methyl-1-propanesulfonic acid) in water and ethanol by bending instability of electrospinning. By newly introducing parallel subelectrodes that change an ordinary electric field into a splitting electric field, it was elucidated that the tensional electrostatic forces caused by a modified electric field have an important effect on the transformation of helical structures.
Effects of strain on the optimal annealing temperature of GaInNAsSb quantum wells
Authors: Yuen Homan B. , Bank Seth R. , Bae Hopil , Wistey Mark A. , Harris James S.
Published: June 2006

Dilute nitride alloys have required postgrowth annealing to improve their luminescent efficiency. There exists an optimal annealing temperature that results in the highest photoluminescence intensity. Several series of GaInNAsSb samples with varying indium and antimony contents were grown to examine the effects of compositional and strain changes on this optimal annealing temperature. We show that a relationship exists between this temperature and the lattice strain of GaInNAsSb quantum wells. As strain increases in these alloys, the optimal annealing temperature decreases. Higher optimal anneal temperatures are found with lower lattice strain. This has important ramifications for the design of long-wavelength GaInNAsSb devices.
Control of carrier transport in organic semiconductors by aluminum doping
Authors: Wang Z. J. , Wu Y. , Zhou Y. C. , Zhou J. , Zhang S. T. , Ding X. M. , Hou X. Y. , Zhu Z. Q.
Published: June 2006

Control of carrier transport in organic semiconductors by aluminum doping is realized in organic light-emitting devices (OLEDs) for which electroluminescence can sensitively reflect the status of carrier transport. It is found that an Al-doped layer with proper thickness (∼1–10nm) may block hole transport completely and enhance electron transport to some extent regardless of its location in the organic carrier transport layers. Improvement in the efficiency of OLEDs with an aluminum cathode is achieved upon the introduction of a very thin (∼3nm) Al-doped region near the light-emitting area. The current efficiency obtained with such Al-doped devices is about 30% higher than that with undoped devices.
Superior electrical properties of crystalline Er2O3 films epitaxially grown on Si substrates
Authors: Chen S. , Zhu Y. Y. , Xu R. , Wu Y. Q. , Yang X. J. , Fan Y. L. , Lu F. , Jiang Z. M. , Zou J.
Published: June 2006

Crystalline Er2O3 thin films were epitaxially grown on Si (001) substrates. The dielectric constant of the film with an equivalent oxide thickness of 2.0nm is 14.4. The leakage current density as small as 1.6×10−4A∕cm2 at a reversed bias voltage of −1V has been measured. Atomically sharp Er2O3∕Si interface, superior electrical properties, and good time stability of the Er2O3 thin film indicate that crystalline Er2O3 thin film can be an ideal candidate of future electronic devices.
Characterisation and immunolocalisation of a pollen-specific calmodulin-binding protein from rice
Authors: Zhang Qiusheng , Zhang Jingjing , Yang Daichang , Li Yangsheng , Li Shaoqing , Zhu Yingguo
Published: June 2006

A novel calmodulin (CaM)-binding protein of rice (Oryza sativa pollen CaM-binding protein, OsPCBP) was isolated. It contains six tetratrcopeptide repeats (TPRs) with a molecular mass of ~76.7 kDa. Database searches show that OsPCBP is conserved in monocots and dicots. The results from CaM–agarose pull-down assays show that OsPCBP binds to CaM in a Ca2+-dependent manner and its CaM-binding domain (CBD) is located in a segment VSKGWRLLALVLSAQQRY. Northern blot and reverse transcription-polymerase chain reaction (RT-PCR) analysis have demonstrated that OsPCBP is a pollen-specific and late-expressed gene. Immunolocalisation showed that OsPCBP was localised in the amyloplast and intine during the late stage of pollen development. However, upon pollen hydration, there was some leakage of protein and the distribution of OsPCBP in the intine varied with the duration of hydration. After pollen germination, much OsPCBP was observed in the pollen tube wall. These results indicate the relationship of OsPCBP with starch accumulation and its involvement in pollen germination.
Systemic Potato virus X infection induces defence gene expression and accumulation of β-phenylethylamine-alkaloids in potato
Authors: Niehl Annette , Lacomme Christophe , Erban Alexander , Kopka Joachim , Krämer Ute , Fisahn Joachim
Published: June 2006

A better understanding of defence responses elicited during compatible plant–virus interactions is a current goal in plant pathology. We analysed defence responses during infection of Solanum tuberosum L. cv. Desiree with Potato virus X (PVX) at the transcript and metabolite level. A mostly unchanged primary metabolism reflects the compatible nature of this plant–virus interaction. Salicylic acid biosynthesis and expression of several defence genes including PR-1 and glutathione-S-transferase, which are involved in ethylene and reactive oxygen species dependent signalling, were highly up-regulated in upper-uninoculated (systemic) leaves of PVX-infected potato plants compared with mock-inoculated controls. Moreover, the β-phenylethylamine-alkaloids tyramine, octopamine, dopamine and norepinephrine were highly induced upon infection. β-phenylethylamine-alkaloids can contribute to active plant defence responses by forming hydroxycinnamic acid amides (HCAA), which are thought to increase cell wall stability by extracellular peroxidative polymerisation. Expression of tyramine-hydroxycinnamoyl transferase (THT) and apoplastic peroxidase (POD) was highly induced upon PVX infection in systemic leaves, which suggests synthesis and extracellular polymerisation of HCAA. Since cell-wall-bound ion concentrations could contribute to this process, we measured cell-wall-bound and total ion concentrations in PVX-infected and mock-inoculated leaves. The observed metabolic and transcriptional changes might represent a systemic acquired resistance response against subsequent pathogen challenge.
Global fire activity from two years of MODIS data
Authors: Csiszar Ivan , Denis Lynn , Giglio Louis , Justice Christopher O. , Hewson Jenny
Published: June 2006

Moderate Resolution Imaging Spectroradiometer (MODIS) on board the NASA Earth Observing System Terra and Aqua satellites provides global fire observations of unprecedented quality. This paper presents spatial and temporal distributions of active fires from 2001 and 2002, the first 2 years of the MODIS active fire data record. Monthly fire counts were analysed globally and within several regions of major fire activity and vegetation type. The global maximum of the annual cycle of fire activity for both years occurred in August; a combined result of burning during the dry season in the Southern Hemisphere tropics and the warm season over the Northern Hemisphere extratropics. The minimum of global fire activity occurred in March in both years. Burning in the tropics occurred mostly in savanna and shrubland areas with a high percentage of herbaceous vegetation. In the extratropics, fires were detected over croplands, grasslands and forests. The global total numbers of fire counts observed in 2001 and 2002 differed by less than 3%, but regionally significant differences were found between the two years in total and relative fire counts and in the timing of burning. Fire counts from daytime MODIS observations from Terra and Aqua also provided evidence of the diurnal cycle of fire activity. This analysis of ‘fire/no fire’ binary indicators is a first-order approximation of global spatio-temporal fire dynamics. For several applications, such as the estimation of pyrogenic emissions, further studies of burned area and fire characteristics are needed.
Ectodysplasin regulates the lymphotoxin-β pathway for hair differentiation
Authors: Cui Chang-Yi , Hashimoto Tsuyoshi , Grivennikov Sergei I. , Piao Yulan , Nedospasov Sergei A. , Schlessinger David
Published: June 2006

Mutations in theEDAgene cause anhidrotic/hypohidrotic ectodermal dysplasia, a disorder characterized by defective formation of hair, sweat glands, and teeth in humans and in a mouse model, “Tabby” (Ta). The gene encodes ectodysplasin, a TNF ligand family member that activates the NF-κB-signaling pathway, but downstream targets and the mechanism of skin appendage formation have been only partially analyzed. Comparative transcription profiling of embryonic skin during hair follicle development in WT and Ta mice identified critical anhidrotic/hypohidrotic ectodermal dysplasia (EDA) effectors in four pathways, three already implicated in follicle formation. They includedShhand its effectors, as well as antagonists for the Wnt (Dkk4) and BMP (Sostdc1) pathways. The fourth pathway was unexpected, a variant NF-κB-signaling cascade based on lymphotoxin-β (LTβ)/RelB. Previously known to participate only in lymphoid organogenesis, LTβ was enriched in developing hair follicles of WT but not in Ta mice. Furthermore, in mice lacking LTβ, all three types of mouse hair were still formed, but all were structurally abnormal. Guard hairs became wavy and irregular, zigzag/auchen hairs lost their kinks, and in a phenocopy of features of Ta animals, the awl hairs doubled in number and were characteristically distorted and pinched. LTβ-null mice that received WT bone marrow transplants maintained mutant hair phenotypes, consistent with autonomous LTβ action in skin independent of its expression in lymphoid cells. Thus, as an EDA target, LTβ regulates the form of hair in developing hair follicles; and when EDA is defective, failure of LTβ activation can account for part of the Ta phenotype.
Neurocognitive development of the ability to manipulate information in working memory
Authors: Crone Eveline A. , Wendelken Carter , Donohue Sarah , van Leijenhorst Linda , Bunge Silvia A.
Published: June 2006

The ability to manipulate information in working memory is a key factor in cognitive development. Here, we used event-related functional MRI to test the hypothesis that developmental improvements in manipulation, relative to pure maintenance, are associated with increased recruitment of dorsolateral (DL) prefrontal cortex (PFC) and superior parietal cortex. Three age groups (8–12 years old, 13–17 years old, and 18–25 years old) performed an object-working memory task with separate maintenance and manipulation conditions. We found that 8- to 12-year-olds did not perform the task as well as adolescents or adults, particularly on trials requiring manipulation in addition to maintenance. In this study, no age differences were observed in the activation profile of ventrolateral PFC, a region associated with online maintenance. In contrast, unlike the older participants, 8- to 12-year-olds failed to recruit right DL PFC and bilateral superior parietal cortex during the delay period for manipulation relative to maintenance. This group difference was observed specifically during the delay period, while participants reordered items in working memory, and could not be accounted for by group differences in performance. Across participants, activation levels in right DL PFC and superior parietal cortex, but not ventrolateral PFC, were positively correlated with performance on manipulation trials. These results indicate that increased recruitment of right DL PFC and bilateral parietal cortex during adolescence is associated with improvements in the ability to work with object representations.
Evidence for helical structures in poly(1-olefin sulfones) by transmission electron microscopy.
Authors: Ruben G C , Stockmayer W H
Published: June 2006

Transmission electron microscope images were obtained of fractions of poly(1-tetradecene sulfone) and poly(cyclohexene sulfone) cast from very dilute solutions (0.007%, wt/vol) and rapidly freeze-dried on a mica surface. The samples were then vertically platinum-carbon (Pt-C) replicated with 9 +/- 0.3-A Pt-C and held together with 128 A of electron-transparent evaporated carbon. The Pt-C coating enlarges the molecular chain diameters by approximately 5 A, so that a single polysulfone chain has an apparent diameter of 9-12 A in the transmission electron microscope. Poly(1-tetradecene sulfone) forms short helical regions that show irregular helical turns of pitch 7-18 A, two to eight turns long with apparent helix diameters of 16-22 A. The n-C12H25 side chains were not obvious on the helices, but a few were visible on extended chain sections. In contrast, poly(cyclohexene sulfone) appears as a collection of Pt-C-coated single chains 10-12 A in diameter with no side-chain projections. The presence and absence of helical regions in these freeze-dried polysulfones thus reflects their solution conformations as long ago inferred on the basis of dielectric measurements.
A yeast protein phosphatase related to the vaccinia virus VH1 phosphatase is induced by nitrogen starvation.
Authors: Guan K , Hakes D J , Wang Y , Park H D , Cooper T G , Dixon J E
Published: June 2006

A phosphatase related to the vaccinia virus VH1 phosphatase has been cloned from Saccharomyces cerevisiae. The yeast phosphatase is related to the Schizosaccharomyces pombe cdc25 gene product and to a protein encoded by a mammalian open reading frame known as 3CH134, which is an immediate early gene responding to serum stimulation. The phosphatase activity of the yeast gene product appears to be restricted to the hydrolysis of phosphotyrosine-containing substrates, whereas the vaccinia phosphatase hydrolyzes both phosphoserine- and phosphotyrosine-containing substrates. The mRNA encoding the yeast phosphatase is dramatically induced by nitrogen starvation. Inactivation of the yeast phosphatase gene results in a decrease in growth rate.
Preferential repair of ionizing radiation-induced damage in the transcribed strand of an active human gene is defective in Cockayne syndrome.
Authors: Leadon S A , Cooper P K
Published: June 2006

Cells from patients with Cockayne syndrome (CS), which are sensitive to killing by UV although overall damage removal appears normal, are specifically defective in repair of UV damage in actively transcribed genes. Because several CS strains display cross-sensitivity to killing by ionizing radiation, we examined whether ionizing radiation-induced damage in active genes is preferentially repaired by normal cells and whether the radiosensitivity of CS cells can be explained by a defect in this process. We found that ionizing radiation-induced damage was repaired more rapidly in the transcriptionally active metallothionein IIA (MTIIA) gene than in the inactive MTIIB gene or in the genome overall in normal cells as a result of faster repair on the transcribed strand of MTIIA. Cells of the radiosensitive CS strain CS1AN are completely defective in this strand-selective repair of ionizing radiation-induced damage, although their overall repair rate appears normal. CS3BE cells, which are intermediate in radiosensitivity, do exhibit more rapid repair of the transcribed strand but at a reduced rate compared to normal cells. Xeroderma pigmentosum complementation group A cells, which are hypersensitive to UV light because of a defect in the nucleotide excision repair pathway but do not show increased sensitivity to ionizing radiation, preferentially repair ionizing radiation-induced damage on the transcribed strand of MTIIA. Thus, the ability to rapidly repair ionizing radiation-induced damage in actively transcribing genes correlates with cell survival. Our results extend the generality of preferential repair in active genes to include damage other than bulky lesions.
Book Review
Authors: Malcus P.
Published: June 2006

Doppler Ultrasound in Gynecology and Obstetrics. By Christof Sohn, Han Joacim Voigt and Klaus Vetter. Thieme Verlagsgruppe, Stuttgart. ISBN 3-13-135591-5. 221 pages. Price €99.
Sphenoid sinus craniopharyngioma simulating mucocele
Authors: Koral K. , Weprin B. , Rollins N. K.
Published: June 2006

We present a case of extracranial craniopharyngioma simulating a sphenoid sinus mucocele in a 12-year-old female who presented with progressive subacute left-sided visual disturbance. Although infrasellar craniopharyngioma is a rare entity, the presence of foci of calcification within the lesion is a useful finding for diagnosis.
Value of repeat ultrasound-guided fine-needle aspiration in nodules with benign cytological diagnosis
Authors: Shin J. H. , Han B.-K. , Ko K. , Choe Y. H. , Oh Y. L.
Published: June 2006

Purpose: To assess the value of repeat ultrasound-guided fine-needle aspiration (US-FNA) in nodules with benign cytological diagnosis.

Material and Methods: One-hundred-and-eighty-seven patients undergoing repeat US-FNA were included after a benign cytological diagnosis had been made by the initial US-FNA. They were divided into a re-aspiration group, who underwent repeat US-FNA within 6 months for a discordant pathological and clinico-radiological result, and a follow-up aspiration group, who underwent repeat US-FNA after 6 months without any clinical or radiological suspicion. The cancer rate in each group and the US findings of the later-diagnosed malignant nodules were assessed.

Results: Nine malignancies were verified in the 187 cases (4.8%) by repeat US-FNA or surgery. In 44 patients in the re-aspiration group, 6 malignancies were identified (13.6%), compared with 3 malignancies in the 143 patients in the follow-up aspiration group (2.1%) ( P<0.05). The later-diagnosed malignant nodules were an average of 1.0 cm in diameter; 66.7% were round; 66.7% were circumscribed; 100% were solid; 88.9% were hypoechoic; and 55.6% contained calcifications on US.

Conclusion: The follow-up of nodules with benign cytological diagnosis without clinico-radiological suspicion of malignancy is warranted using imaging surveillance rather than repeated US-FNA.