bluuebunny/crossref_metadata_2025 huggingface dataset:
The Stratigraphy and Fire History of the Kutai Peatlands, Kalimantan, Indonesia
Authors: Hope Geoffrey , Chokkalingam Unna , Anwar Syaiful
Published: October 2005

The equatorial peatlands of the Kutai lowland of eastern Kalimantan are generally 4–10 m in thickness but some sections exceed 16 m in depth. The deposition of peat commenced about 8000 yrs ago after shallow flooding of the basin by the Mahakam River. The earliest vegetation is aPandanusswamp which grades upwards to swamp forest dominated by dipterocarps. The peatland has expanded laterally and rivers have maintained narrow levee-channel tracks through the swamp, which has grown vertically in balance with river accretion. Historical fires are associated with extreme El Niño years of drought, but human agency is important. The fires of 1982–1983 and 1997–1998 burnt up to 85% of the vegetation on the peatland. Although charcoal analyses show that fire has occurred throughout the history of the peatland, it is rare in forests remote from rivers until the last 3000 years and only common within the last millennium. Fires are earlier and more frequent in sites accessible from waterways, and floodplains have been widely burnt down to water table or below, forming extensive lakes.
Evidence and features of magnetospheric particle leakage on days 30–36, 1995: Wind, Geotail, and IMP 8 observations compared
Authors: Anagnostopoulos G. C. , Efthymiadis D. , Sarris E. T. , Krimigis S. M.
Published: October 2005

Simultaneous observations from the Geotail, IMP 8, and Wind spacecrafts during periods of energetic particle activity, studied previously far upstream from the Earth's bow shock, are used in this paper to resolve ambiguities between the leakage and Fermi models as the potential mechanism of such upstream events. CNO flux enhancements were observed at the current sheet (IMP 8 and Geotail), during intense substorm activity, before detection of a typical upstream Wind ion event rich in heavy ion species on day 31, 1995; the plasma sheet CNO flux enhancement was observed during times of a corotating interaction region with a seed population rich in CNO ion species. In addition, the features of energetic ion events observed on days 32–36, 1995, near the Earth's bow shock (Geotail and IMP 8) suggest that magnetospheric leakage of energetic particles is a much more likely source of the observed upstream ions than Fermi acceleration. Such features, observed during periods of high values of geomagnetic index Kp (3–5+), are the presence of upstream energetic electrons and ionospheric O+ ions, the dawn–dusk asymmetry of energetic ions and electrons, the anisotropic upstream ion distributions, the inverse energy dispersion of ion intensities, etc. A much higher percentage of electron‐associated ion events found near the magnetosphere/bow shock (Geotail) than in the far upstream region (Wind) suggests a rigidity‐dependent propagation in the upstream region. Furthermore, a systematic hardening of ion spectra over the whole energy range ∼0.05 to ∼1.00 MeV observed by IMP 8 near the bow shock suggests that the same particle distribution dominated the ion responses during the typical Wind event of day 34, 1995. The above results point out that the joint analysis of observations from all three spacecrafts can help to resolve a number of the ambiguities concerning the origin of upstream ion events on days 30–36, 1995, posed by the analysis of observations made by a distant spacecraft (Wind) alone.
Historical land use changes and mesoscale summer climate on the Swiss Plateau
Authors: Schneider Nicolas , Eugster Werner
Published: October 2005

The impacts of historical land use changes on the Swiss Plateau on the summer climate were investigated. The land use changes consist primarily of a conversion of wetlands with extended peat soils into highly productive agricultural lands. We used the “Lokal‐Modell” of the Consortium for Small‐Scale Modeling to conduct several 1‐month‐long high‐resolution simulations (1.5 × 1.5 km2) with present and past landscape conditions. The past land use was reconstructed from historical maps (1800–1850) over a relatively small perturbed area of ≈400 km2 embedded in an otherwise unchanged present‐day landscape. The documented changes in land use and land cover lead to a daytime cooling of up to 0.3°C and a nocturnal warming of the same magnitude, thereby decreasing the diurnal temperature range by 0.6°C. The alteration of the radiation budget and the surface energy balance leads to a shallower daytime mixed layer under present compared to past conditions, with a reduction in the convective upward transport of moisture. The cloud coverage over the study area decreased by up to 5% on average under present conditions. The regional precipitation is most strongly affected in the mean downwind areas and not so much over the area of land use changes. Because of orographic effects in the downwind area a decrease in precipitation in lower‐elevation areas was modeled, while precipitation in the adjacent higher‐elevation downwind areas increased. In contrast to our expectations the soil water status did not play a dominant role in this area because of the high water table. Even under present conditions the availability of soil moisture and the accessibility of the groundwater to plant roots is, on average, still not a limiting factor for plant transpiration.
Description and sensitivity analysis of a limb scattering ozone retrieval algorithm
Authors: Loughman R. P. , Flittner D. E. , Herman B. M. , Bhartia P. K. , Hilsenrath E. , McPeters R. D.
Published: October 2005

We present the theoretical basis for an algorithm that retrieves vertical profiles of ozone concentration using measurements of light scattered from the limb of the atmosphere. Simulated radiances at wavelengths between 300 and 675 nm are inverted using the optimal estimation technique, producing a retrieved ozone number density profile between 10 and 55 km. A detailed sensitivity analysis of this ozone retrieval algorithm follows. The largest source of ozone retrieval error is tangent height misregistration (i.e., instrument pointing error), which is relevant throughout the altitude range of interest and produces retrieval errors on the order of 10–20% due to a tangent height registration error of 0.5 km. The retrieved profile is shifted in altitude relative to the true profile, with very little distortion of the profile shape. Sensitivity to stratospheric aerosol is also a significant source of error, with errors of 5–8% for altitudes less than 40 km under background aerosol conditions when an aerosol‐free atmosphere is assumed by the algorithm. Using an incorrect a priori ozone estimate can produce errors up to 15% at altitudes near 10 km, but the a priori profile has little influence above that level. Addressing these error sources (e.g., with better instrument pointing knowledge, introduction of reliable aerosol information, and better instrument signal‐to‐noise to reduce the importance of the a priori ozone estimate, respectively) is the key to significantly improving the retrieval accuracy. Further improvement would then be limited by several secondary error sources that produce retrieval errors at the 5% level.
Sandwave migration predictor based on shape information
Authors: Knaapen M. A. F.
Published: October 2005

Migration of offshore seabed waves, which endangers the stability of pipelines and communication cables, is hard to measure. The migration rates are small compared to the measurement errors. Here, sandwave migration rates are determined from the change in the crest position deduced from long time series of bathymetric echo‐sounding data. The crests are identified as local extremes in a bathymetric profile, after low‐pass filtering. This approach is applied to both two‐dimensional data and to profiles along pipelines. A consistent migration rate of several meters per year is found. A strong correlation between the sandwave shape and the migration rate is translated in a migration predictor. The predictor assumes that the sandwaves migrate in the direction of the steepest slope, following a quadratic relation with the asymmetry. Furthermore, it is included that longer waves travel faster but higher waves travel slower. The predictor is calibrated against data from nine areas and validated using three additional areas. An error analysis using markers shows that the error of the predictor is small compared to the noise in the individual crest position observations.
El Niño variability off Peru during the last 20,000 years
Authors: Rein Bert , Lückge Andreas , Reinhardt Lutz , Sirocko Frank , Wolf Anja , Dullo Wolf‐Christian
Published: October 2005

Here we present a high‐resolution marine sediment record from the El Niño region off the coast of Peru spanning the last 20,000 years. Sea surface temperature, photosynthetic pigments, and a lithic proxy for El Niño flood events on the continent are used as paleo–El Niño–Southern Oscillation proxy data. The onset of stronger El Niño activity in Peru started around 17,000 calibrated years before the present, which is later than modeling experiments show but contemporaneous with the Heinrich event 1. Maximum El Niño activity occurred during the early and late Holocene, especially during the second and third millennium B.P. The recurrence period of very strong El Niño events is 60–80 years. El Niño events were weak before and during the beginning of the Younger Dryas, during the middle of the Holocene, and during medieval times. The strength of El Niño flood events during the last millennium has positive and negative relationships to global and Northern Hemisphere temperature reconstructions.
Role of the Kazerun Fault Zone in the formation and deformation of the Zagros Fold‐Thrust Belt, Iran
Authors: Sepehr M. , Cosgrove J. W.
Published: October 2005

The Kazerun Fault is a N‐S trending fault zone, which obliquely truncates the NW‐SE trending Zagros Fold‐Thrust Belt. This active fault zone is an ancient structural lineament which has controlled the structure, sedimentation, and subsidence of the central part of the Zagros since the Early Cambrian and has had an influence on the formation of the hydrocarbon system of the belt. The Kazerun Fault limited the distribution of the Cambrian Hormuz salt (the major decollement horizon that separates the Precambrian basement from the thick sedimentary cover) to the west. Its later reactivation with other N‐S trending fault zones (e.g., the Izeh Fault Zone) during the Cretaceous resulted in major sedimentary thickness and facies variations along the belt. This study presents a new interpretation for the evolution of the Kazerun Fault Zone based on field evidence and a review of various published and unpublished data. It is argued that at the surface, the fault zone is delineated by four north‐south trending segments and that marked differences occur in the distribution of deformation on either side of the fault segments in the Late Tertiary. During this time these segments acted as transfer faults (lateral ramps) linking different segments of the Zagros deformation fronts.
Two‐phase versus mixed‐flow perspective on suspended sediment transport in turbulent channel flows
Authors: Muste M. , Yu K. , Fujita I. , Ettema R.
Published: October 2005

The present paper reports results obtained with image velocimetry to provide new insights into the two‐phase nature of sediment‐laden flows. The resulting two‐phase flow perspective is compared with the traditional mixed‐flow (or combined phase) perspective that treats sediment‐laden flows essentially as flow of a single fluid. The insights are from flume experiments entailing the use of fully suspended natural sand and neutrally buoyant particles conveyed in a turbulent open channel flow of water. They confirm that suspended particles (irrespective of particle density) may affect a turbulent flow throughout its depth. Suspended particles modify flow turbulence, the main effects quantified being decreases in the bulk water velocity and in the von Kárman constant, while the flow's friction velocity remains approximately constant. Comparison of the results obtained with the two particle densities reveals differences in particle influences on water flow. In the flows conveying sand the characteristics of water and particle movement are strongly coupled, yet distinct; that is, there is a lag in the mean velocity between local water and particle movement, and intensities of water turbulence differ from intensities of particle motion turbulence. These results confirm and extend prior two‐phase flow perspectives on suspended‐particle transport and indicate the inaccuracies in some assumptions associated with the mixed fluid formulation of suspended‐particle transport.
A simple scheme for climate feedback analysis
Authors: Yokohata T. , Emori S. , Nozawa T. , Tsushima Y. , Ogura T. , Kimoto M.
Published: October 2005

In this study we present a simple scheme for the diagnosis of the strength of climate feedback. The scheme is based on straightforward calculations using the conventional output of a general circulation model (GCM), and evaluates the major radiative feedbacks concerning the surface, clear‐sky atmosphere, and clouds. We place an emphasis on evaluating shortwave (SW) feedbacks. Assumptions involved in extracting the SW surface feedback are validated by accurate calculations and considered to be acceptable. The performance of our scheme is demonstrated via a doubled CO2 experiment. Compared to conventional methods, we can evaluate SW feedbacks more accurately while the evaluation of LW feedbacks is essentially similar between the two methods. The ready application of our scheme to the output of various GCMs should be of great use for multi‐model ensemble analyses, which contribute to reducing the uncertainty in future climate projections.
Multiple scattering effects due to hydrometeors on precipitation radar systems
Authors: Battaglia A. , Ajewole M. O. , Simmer C.
Published: October 2005

Space‐borne radars are invaluable tools for characterizing clouds and precipitation. At higher frequencies (like those used for the TRMM PR or envisaged for GPM radars) attenuation due to hydrometeors increasingly becomes a relevant issue. Simultaneously when dealing with active sensors, multiple scattering effects could be significant due to the simultaneous increase of the optical thickness and the single scattering albedo of the hydrometeors with frequency. In this study, we investigate multiple scattering due to rainfall and graupel on radar returns for nadir observations at 13 and 35 GHz. A numerical approach, based on the forward fully polarized Monte Carlo technique, which incorporates a Gaussian antenna pattern function with varying beam‐widths, is adopted in the study. Results reveal that multiple scattering effects are driven by the interplay between the antenna footprint, the medium scattering coefficient and the depth traveled inside the medium. The multiple scattering effects are generally negligible at 13 GHz for typical space‐borne and air‐borne systems while they are relevant to space‐borne but almost negligible in air‐borne configurations at 35 GHz.
Retrieving optically thick ice cloud microphysical properties by using airborne dual‐wavelength radar measurements
Authors: Wang Zhien , Heymsfield Gerald M. , Li Lihua , Heymsfield Andrew J.
Published: October 2005

An algorithm to retrieve optically thick ice cloud microphysical property profiles is developed by using the GSFC 9.6 GHz ER‐2 Doppler Radar (EDOP) and the 94 GHz Cloud Radar System (CRS) measurements aboard the high‐altitude ER‐2 aircraft. In situ size distribution and total water content data from the CRYSTAL‐FACE field campaign are used for the algorithm development. To reduce uncertainty in calculated radar reflectivity factors (Ze) at these wavelengths, coincident radar measurements and size distribution data are used to guide the selection of mass‐length relationships and to deal with the density and nonspherical effects of ice crystals on the Ze calculations. The algorithm is able to retrieve microphysical property profiles of optically thick ice clouds, such as deep convective and anvil clouds, which are very challenging for single‐wavelength radar and lidar. Examples of retrieved microphysical properties for deep convective clouds are presented, which show that EDOP and CRS measurements provide rich information to study cloud structure and evolution. Good agreement between IWPs derived from an independent submillimeter‐wave radiometer, CoSSIR, and dual‐wavelength radar measurements indicates accuracy of the IWC retrieved from the dual‐wavelength radar algorithm.
Intravenous IGF‐I receptor antisense reduces IGF‐IR expression and diminishes pressor responses to angiotensin II in conscious normotensive rats
Authors: Nguyen Tien Thuy , White Paul James
Published: October 2005

Given the variety of cardiovascular effects of insulin‐like growth factor‐I (IGF‐I), we investigated the effects of a functional deficit in IGF‐I signalling in the conscious rat cardiovascular system using intravenous IGF‐I receptor antisense (AS, 0.5 nmol) treatment.

Insulin‐like growth factor‐I receptor (IGF‐IR) immunoreactivity was reduced in IGF‐IR AS‐treated tail arteries. Western immunoblot analysis demonstrated a decrease in cardiac IGF‐IR in IGF‐IR AS‐treated rats; treatment reduced the expression of IGF‐IR to 83±6% of that in samples from vehicle‐treated rats, compared to 99±3% for a control, full‐mismatch oligonucleotide (MM‐18) or 100% (vehicle).

IGF‐IR AS treatment had no effect on resting blood pressure during the 14‐day treatment period.

Pressor responses (as measured by increase in systolic arterial pressure) to angiotensin II (AngII) gradually decreased over 2 weeks treatment with IGF‐IR AS (5 × 0.5 nmol per intravenous injection, 2 weeks), and were significantly reduced at treatment day 14 compared to day 7 (2.7‐fold rightward shift). IGF‐IR AS treatment caused a significant rightward shift in the angiotensin II (AngII) dose–response compared to both vehicle and full‐mismatch treated rats (4.0‐fold shift compared to vehicle, P<0.01, n=6–14).

There was a significant decrease in cardiac angiotensin II type 1 receptor (AT1R) expression in AS‐treated rats compared to vehicle‐treated rats; cardiac AT1R was decreased to 80±6% in comparison to 100%. AT1R immunoreactivity was also reduced in IGF‐IR AS‐treated tail arteries.

IGF‐IR AS treatment resulted in structural changes in both the heart and aortae, with small but significant differences observed between left ventricle/bodyweight ratios of AS and both vehicle‐ and MM‐18‐treated rats (n=8, P<0.05). Aortic cross‐sectional areas of AS‐treated rats were significantly lower than MM‐18‐ and vehicle‐treated rats (27.4±5.7% reduction of vehicle‐treated samples, n=8, P<0.01).

The results of this study suggest that an induced loss of IGF‐IR, while not affecting resting blood pressure, has a predominantly inhibitory effect on vascular response to vasoconstrictor agents including angiotensin II. This may occur through downstream effects on AT1R expression, via modulation of the expression of receptors for other vasoactive signalling molecules, or via changes in myocyte proliferation.

British Journal of Pharmacology (2005) 146, 935–941. doi:10.1038/sj.bjp.0706378
Role of the PKC/CPI‐17 pathway in enhanced contractile responses of mesenteric arteries from diabetic rats to α‐adrenoceptor stimulation
Authors: Mueed Irem , Zhang Lili , MacLeod Kathleen M
Published: October 2005

Protein kinase C (PKC) may contribute to enhanced contractile responses of arteries from streptozotocin‐diabetic rats to stimulation of G‐protein coupled receptors. This was investigated by comparing the effects of PKC inhibitors on contractile responses of mesenteric arteries from diabetic and age‐matched control rats to noradrenaline (NA) and endothelin‐1 (ET‐1). The effects of NA and ET‐1 on the distribution of three isoforms of PKC implicated in contraction were also determined. In addition, the effect of NA on phosphorylation of CPI‐17, a substrate for PKC, was investigated.

Contractile responses of endothelium‐denuded arteries from diabetic rats to NA were enhanced, but were normalized by PKC inhibition. In contrast, contractile responses to ET‐1 were not significantly different, and were blocked to a similar extent by PKC inhibition, in arteries from control and diabetic rats.

NA produced only a small increase in particulate levels of PKCɛ in control arteries (to 125±8% of levels in untreated arteries), but a significant increase in particulate PKCα (to 190±22%) and a much greater increase in particulate PKCɛ (to 230±19%) in arteries from diabetic rats. ET‐1 increased particulate PKCα and ɛ to a similar extent in arteries from control and diabetic rats.

NA significantly enhanced CPI‐17 phosphorylation from a basal level of 22±10 to 71±7% of total in arteries from diabetic rats, and this was prevented by PKC inhibition. NA had no detectable effect on CPI‐17 phosphorylation in arteries from control rats.

These data suggest that NA‐induced activation of PKC and CPI‐17, its downstream target, is selectively enhanced in arteries from diabetic rats, and mediates the enhanced contractile responses to this agonist.

British Journal of Pharmacology (2005) 146, 972–982. doi:10.1038/sj.bjp.0706398
Inhibition of RhoA/Rho kinase pathway is involved in the beneficial effect of sildenafil on pulmonary hypertension
Authors: Guilluy Christophe , Sauzeau Vincent , Rolli‐Derkinderen Malvyne , Guérin Patrice , Sagan Christine , Pacaud Pierre , Loirand Gervaise
Published: October 2005

Inhibition of the type 5 phosphodiesterase and inhibition of Rho kinase are both effective in reducing pulmonary hypertension (PH). Here we investigate whether Rho kinase inhibition is involved in the beneficial effect of the type 5 phosphodiesterase inhibitor sildenafil on PH.

Chronic hypoxia‐induced PH in rats is associated with an increase in RhoA activity in pulmonary artery that was maximal after 2 days (10.7±0.9‐fold increase,n=6,P<0.001). The activity of Rho kinase assessed by measuring the level of myosin phosphatase target subunit 1 (MYPT1) phosphorylation was also increased (5.7±0.8‐fold over control,n=8).

Chronic fasudil (30 mg kg−1 day−1; 14 days) and sildenafil (25 mg kg−1 day−1; 14 days) treatments reduced PH and pulmonary cardiovascular remodelling, and inhibited the MYPT1 phosphorylation in pulmonary artery from hypoxic rats by 82.3±3% (n=4) and by 76.6±2% (n=4), respectively.

The inhibitory effect of sildenafil (10 μM) on MYPT1 phosphorylation was demonstrated by the loss of actin stress fibres in vascular smooth muscle cells. However,in vitrokinase assays indicated that sildenafil had no direct inhibitory action on Rho kinase activity.

Sildenafil treatment induced increased RhoA phosphorylation and association to its cytosolic inhibitory protein, guanine dissociation inhibitor (GDI) in pulmonary artery.

We propose that sildenafil inhibits RhoA/Rho kinase‐dependent functions in pulmonary artery through enhanced RhoA phosphorylation and cytosolic sequestration by GDI. The inhibition of intracellular events downstream of RhoA thus participates in the beneficial effect of sildenafil on PH.

British Journal of Pharmacology(2005)146, 1010–1018. doi:10.1038/sj.bjp.0706408
Plant cannabinoids: a neglected pharmacological treasure trove
Authors: Mechoulam Raphael
Published: October 2005

Most of the cannabinoids in Cannabis sativa L. have not been fully evaluated for their pharmacological activity. A publication in this issue presents evidence that a plant cannabinoid, Δ9‐tetrahydrocannabivarin is a potent antagonist of anandamide, a major endogenous cannabinoid. It seems possible that many of the non‐psychoactive constituents of this plant will be of biological interest.

British Journal of Pharmacology (2005) 146, 913–915. doi:10.1038/sj.bjp.0706415
The crucial role of metal ions in neurodegeneration: the basis for a promising therapeutic strategy
Authors: Gaeta Alessandra , Hider Robert C
Published: October 2005

The variety of factors and events involved in neurodegeneration renders the subject a major challenge. Neurodegenerative disorders include a number of different pathological conditions, which share similar critical metabolic processes, such as protein aggregation and oxidative stress, both of which are associated with the involvement of metal ions. In this review, Alzheimer's disease, Parkinson's disease and prion disease are discussed, with the aim of identifying common trends underlying these devastating neurological conditions. Chelation therapy could be a valuable therapeutic approach, since metals are considered to be a pharmacological target for the rationale design of new therapeutic agents directed towards the treatment of neurodegeneration.

British Journal of Pharmacology (2005) 146, 1041–1059. doi:10.1038/sj.bjp.0706416
Analytic energy gradients of the optimized effective potential method
Authors: Wu Qin , Cohen Aron J. , Yang Weitao
Published: October 2005

The analytic energy gradients of the optimized effective potential (OEP) method in density-functional theory are developed. Their implementation in the direct optimization approach of Yang and Wu [Phys. Rev. Lett. 89, 143002 (2002)] and Wu and Yang [J. Theor. Comput. Chem. 2, 627 (2003)] are carried out and the validity is confirmed by comparison with corresponding gradients calculated via numerical finite difference. These gradients are then used to perform geometry optimizations on a test set of molecules. It is found that exchange-only OEP (EXX) molecular geometries are very close to the Hartree-Fock results and that the difference between the B3LYP and OEP-B3LYP results is negligible. When the energy is expressed in terms of a functional of Kohn-Sham orbitals, or in terms of a Kohn-Sham potential, the OEP becomes the only way to perform density-functional calculations and the present development in the OEP method should play an important role in the applications of orbital or potential functionals.
First-passage approach for permeable traps
Authors: Vaughn Mark W.
Published: October 2005

Many reactive processes in complex materials involve absorption of diffusing molecules. Recently, there has been interest in particle interaction with partially absorbing (or permeable) traps. Here, we present a simple and efficient method for accounting for the non-diffusion-limited reaction of particles when the flux of particles to the trap is governed by surface permeability. The trapping probability is determined from a one-dimensional Green’s function, which results in a simple algebraic expression. This expression, which applies in the region immediately adjacent to the trap, is then used with a first-passage approach far from the trap. When applied to a suspension of permeable traps, the method is seen to give accurate results over the concentration range. The method is applied to the competition of reactive particles in a suspension of permeable spheres with a reactive continuous phase.
A quantum-classical approach to the photoabsorption spectrum of pyrazine
Authors: Puzari Panchanan , Swathi Rotti S. , Sarkar Biplab , Adhikari Satrajit
Published: October 2005

We have used the time-dependent discrete variable representation (TDDVR) method to simulate the photoabsorption spectrum of pyrazine. The time-dependent molecular dynamics of pyrazine after excitation to the S2 electronic state is considered as a benchmark to investigate the S2 absorption spectrum. We have carried out the dynamics on a basic four-mode model of pyrazine with the inclusion of five major modes as well as the rest of the vibrational modes as bath modes. Investigations reveal the effect of bath modes such as energy and population transfer from the subsystem to the bath. Calculated results demonstrate excellent agreement with traditional quantum-mechanical findings during the entire propagation and converge to the exact quantum results when enough gridpoints are used. It appears that TDDVR, as a numerical quantum dynamics methodology, is a good compromise between accuracy and speed.
Operating principle of polymer insulator organic thin-film transistors exposed to moisture
Authors: Bäcklund T. G. , Österbacka R. , Stubb H. , Bobacka J. , Ivaska A.
Published: October 2005

The operating principle of a hygroscopic insulator field-effect transistor has been investigated. The semiconductor poly(3-hexylthiophene) shows an increased conductivity after applying the poly(vinylphenol) (PVP) insulator, which is attributed to an interfacial dipole layer caused by the permanent dipole moment in PVP. The effects of solvents on the transistor device indicate that low molecular weight protic solvents such as water, methanol, and ethanol affect the I-V characteristics significantly, in contrast to 1-propanol and aprotic solvents such as acetonitrile. The presence of a protic solvent inside the device insulator gives rise to an ion-assisted modulation of the transistor source-drain current.
Raman spectroscopy characterization of titania nanoparticles produced by flame pyrolysis: The influence of size and stoichiometry
Authors: Li Bassi A. , Cattaneo D. , Russo V. , Bottani C. E. , Barborini E. , Mazza T. , Piseri P. , Milani P. , Ernst F. O. , Wegner K. , Pratsinis S. E.
Published: October 2005

A systematic study of the shift and linewidth of the Eg Raman peak at 144cm−1 of anatase TiO2 nanopowders, produced by a flame aerosol technique, is here presented. The analysis was performed as a function of the crystal domain size and of the degree of oxidation. In the nanopowders, a clear contribution of the stoichiometry defects to the peak shift was evidenced, while the peak width seems to be less affected by the oxygen content. The Raman peak behavior due to size reduction has been interpreted in the framework of a phonon quantum confinement model. A critical review of the different approaches to this model, adopted in the literature to explain the behavior of the anatase Raman spectra as a function of the domain size, is presented. In particular, the hypothesis of a three-dimensional isotropic model for the dispersion relations is discussed. This analysis evidences general limits in the application of the phonon confinement model to the study and characterization of nanoparticles and nanostructured materials, showing how an uncritical use of the confinement theory can yield distorted results.
Dynamic compaction of porous silica powder
Authors: Borg John P. , Chapman David J. , Tsembelis Kostas , Proud William G. , Cogar John R.
Published: October 2005

The dynamic compaction characteristics of a porous silicon dioxide (SiO2) powder are reported. The initial specific volumes of the samples were either V00=1.30, 4.0, or 10.0cm3∕g whereas the silicon dioxide has a matrix specific volume of V0=0.455cm3∕g. The impact velocity ranges from 0.25to1.0km∕s and the shock incident pressure on the silica ranges from 0.77to2.25GPa. The shock velocity–particle velocity exhibited a linear relationship within this range. Although these tests represent the low end of dynamic compaction, the dynamic tests compare favorably to extrapolated data available in the open literature. Theoretical pressure–particle velocity and shock velocity–particle velocity curves were generated using a P-α compaction curve. The P-α compaction curve accurately represented the pressure–particle velocity and shock velocity–particle velocity Hugoniot curves for the low specific volume powder, specifically V00=1.30cm3∕g. However, the P-α compaction curve did not accurately represent the pressure–particle velocity or the shock velocity–particle velocity Hugoniot curves for the high specific volume powder, specifically V00=4.0 or 10.0cm3∕g. For the high specific volume powders the wave dynamics appears to be more complicated than is predicted by a single linear wave over the impact velocity and specific volume range investigated.
Cryogenic scanning Hall-probe microscope with centimeter scan range and submicron resolution
Authors: Dinner Rafael B. , Beasley M. R. , Moler Kathryn A.
Published: October 2005

We have constructed a scanning Hall-probe microscope that combines a 1×4cm scan range with 200 nm positioning resolution by coupling stepper motors to high-resolution drivers and reducing gears. The instrument is uniquely suited for efficient magnetic imaging of mesoscopic devices, media, and materials, operating from 4 K to room temperature with fast turn-around time. Its potential for studying dissipation in coated conductors—high-Tc superconducting tapes—is demonstrated via model systems. We image an entire sample of YBa2Cu3O7−δ, then zoom in to individual fluxons. Flux penetration into a single artificial grain boundary is imaged with 4×10−3G∕Hz field resolution and 25μs time resolution by averaging over cycles of ac driving current. Using the resulting magnetic movie, we map out ac power losses.
Structural and photoluminescence properties of porous GaP formed by electrochemical etching
Authors: Tomioka Katsuhiro , Adachi Sadao
Published: October 2005

The structural and optical properties of porous GaP have been studied by scanning electron microscopy, spectroscopic ellipsometry, and photoluminescence (PL) spectroscopy. Porous GaP layers were fabricated by anodic etching in HF:H2O:C2H5OH=1:1:2 electrolyte on n-type (100) and (111)A substrates. The morphology of the porous GaP layer is found to depend strongly on the surface orientation. Apart from the red emission band at ∼1.7eV, a supra-band-gap (EgX) emission has been clearly observed on the porous GaP (111)A sample. The anodic porous layer on the (100) substrate, on the other hand, has shown only the red emission at 300K and both red and green donor-acceptor pair emissions at low temperatures. The correlation between the PL properties and the porous morphology is discussed. An optical transition model is also proposed for the explanation of the PL emission properties of the porous GaP samples.
Nonlinear diffraction and second-harmonic generation enhancement in silicon-opal photonic crystals
Authors: Fedyanin A. A. , Aktsipetrov O. A. , Kurdyukov D. A. , Golubev V. G. , Inoue M.
Published: October 2005

Nonlinear diffraction in three-dimensional silicon-filled photonic crystals of opals is studied. Efficient backward second-harmonic generation (SHG) is observed in the specular direction upon the fundamental radiation reflection from the (111) face of the face-centered-cubic opal lattice. Tuning the fundamental wavelength across the photonic band gap (PBG) results in the 20-times increase of the second-harmonic intensity. The SHG peak has the width of approximately 20nm and is located at the long-wavelength edge of the PBG.
Instability of rotating magnetic field driven flow in a counter-rotating cylinder
Authors: Pedchenko Alexander , Grants Ilmārs
Published: October 2005

We present experimental and numerical results concerning the instability of a liquid metal flow driven by a rotating magnetic field in a finite rotating cylinder. We observe that counter-rotation of the container with respect to the direction of field rotation may have a pronounced stabilizing or destabilizing action depending on the relative rotation rate. The flow is stabilized if the mechanical counter-rotation is relatively strong. The rotating magnetic field then just slows slightly the core of the flow. As a result, the angular momentum increases with the radial position in a vertical side layer and the Rayleigh stability criterion is satisfied. The flow stays stable so far as it rotates in the direction of the container. A rapid transition takes place almost immediately after reversal of the azimuthal flow direction in a narrow region around the axis of the container. The flow is considerably destabilized at a relatively low counter-rotation of the container. This is observed as a linear instability island or a pronounced increase of fluctuating velocity at low or high control parameter values, respectively.
An eddy-viscosity based near-wall treatment for coarse grid large-eddy simulation
Authors: Templeton Jeremy A. , Medic Gorazd , Kalitzin Georgi
Published: October 2005

An eddy-viscosity-based near-wall treatment is proposed to enable large-eddy simulations (LES) to be performed on coarse grids. This formulation consists of imposing wall stress boundary conditions and an eddy viscosity in the near-wall region. The wall stress and eddy viscosity have a Reynolds-averaged Navier-Stokes-like character and are obtained from an averaged velocity profile of a resolved LES of channel flow at Reτ=395. Both are tabulated and are used for the instantaneous quantities. The tabulated eddy viscosity is further corrected using the resolved turbulent stress. Numerical results for flow in a channel at several Reynolds numbers ranging from Reτ=395 to Reτ=10000 are presented.
Electrical properties of compacted assembly of copper oxide nanoparticles
Authors: Bose Anindita , Basu Soumen , Banerjee Sourish , Chakravorty Dipankar
Published: October 2005

Cu 2 O nanoparticles with diameters in the range 6.0-8.6nm were prepared by a chemical method. Both dc and ac electrical properties were measured on a compacted nanoparticle assembly. dc electrical resistivity in the temperature range 140-300K was found to arise due to a variable range hopping conduction mechanism. The ac resistivity variation as a function of frequency (in the range 10kHzto3MHz) and temperature (range 220–320K) was explained on the basis of the power-law exponent in percolating clusters. The interfacial amorphous phase of the nanoparticle assembly appears to control the electrical behavior of the system.
Effect of Cu deficiency on the optical bowing of chalcopyrite CuIn1−xGaxSe2
Authors: Han Sung-Ho , Hasoon Falah S. , Pankow Joel W. , Hermann Allen M. , Levi Dean H.
Published: October 2005

Optical bowing coefficients are used to describe the band gap variation of a composite semiconductor alloy. It is known to be related to the electronic structure and the lattice deformation in the semiconductor alloys. Spectroscopic ellipsometry study shows that the optical bowing coefficient of slightly Cu-poor polycrystalline Cu0.9In1−xGaxSe2 is larger than that of stoichiometric polycrystalline CuIn1−xGaxSe2 and band gaps are larger when Cu becomes poor. This can be explained by an increase in valence band offset due to reduced p-d coupling and an increase of perturbation potential ΔV due to lattice deformation.
High-magnetic-moment core-shell-type FeCo–Au∕Ag nanoparticles
Authors: Bai Jianmin , Wang Jian-Ping
Published: October 2005

We developed a physical technique combining an on-line sputtering/evaporation process with an integrated nanocluster deposition process to prepare core-shell-type nanoparticles. High-magnetic-moment (Fe60Co40)coreAushell and (Fe60Co40)coreAgshell superparamagnetic nanoparticles with controllable particle size of 10–20 nm and Au∕Ag shell thickness of 1–3 nm were prepared by using this method. Au shell is not only functional for the potential biocompatibility but also the key to prevent the oxidation of FeCo nanoparticles. Saturation magnetization of (Fe60Co40)coreAushell nanoparticles was found three times higher than that of iron oxide nanoparticles. This technique enables us to control independently the dimensions of core and shell and select individually materials for core and shell for any other core-shell-type nanoparticles.
Effect of B content on nanostructure evolution and twinning deformation of nanocrystallite in nc-Ti(N,B)∕a-(TiB2,BN) nanocomposite thin films
Authors: Lu Y. H. , Xu Z. K. , Chen Haydn , Shen Y. G. , Li K. Y.
Published: October 2005

Nanostructure evolution and deformation of nanocrystallites in nanocrystalline (nc-) Ti(N,B)/amorphous (a-) (TiB2,BN) thin films were investigated by high resolution transmission electron microscopy. The results indicated that the incorporation of B into TiN led to the formation of the nanocomposite that consists of nc-Ti(N,B) grains embedded in an amorphous matrix. Increasing B content accelerated not only the formation of more [200]-oriented grains but also the twining deformation in nanocrystallites. The deformation was enhanced with increasing B content, which was attributed to the decrease of grain size with increasing B content and the formation of nc-Ti(N,B) solid solution by dissolving B into the TiN lattice.
Subwavelength microwave resonators exhibiting strong coupling to radiation modes
Authors: Stuart Howard R. , Tran Cuong
Published: October 2005

We demonstrate a subwavelength spherical resonator at microwave frequencies designed to mimic the electromagnetic behavior of a negative permittivity sphere. The structure, which has a radius of ∼λ∕12 (where λ is the resonant wavelength), consists of an axially symmetric array of noninterconnected conducting elements forming a resonant spherical object. The structure exhibits many of the properties inherent to negative permittivity spherical resonators, the most notable being a very strong coupling to radiation modes despite being much smaller than the wavelength. This characteristic is quantified by the radiation Q-factor, which was observed to be near 1.5 times the theoretical limit in some of the measured samples, matching the performance achievable in a negative permittivity sphere of comparable electrical size. These resonators may find application in the design of electrically small antennas, as well as in the experimental “simulation,” at microwave frequencies, of nanophotonic device concepts based upon localized plasmon resonances in metal nanoparticles.
High-temperature and low-threshold midinfrared interband cascade lasers
Authors: Yang Rui Q. , Hill Cory J. , Yang B. H.
Published: October 2005

A broad-area midinfrared interband cascade (IC) laser has been demonstrated with a threshold current as low as ∼630A∕cm2 at 300K. Despite exhibiting a large specific thermal resistance (∼56Kcm2∕kW at 172K), the device delivered cw power near 200mW/facet at 500mA and at 83K and lased in cw mode up to 172K. A 0.5-mm-long laser delivered cw power of ∼253mW/facet at 400mA and at 82K, and had power efficiency as high as 26% at ∼80K. Narrow mesa stripe IC lasers had relatively higher threshold current density, yet lased at temperatures up to 237 and 350K in cw and pulsed modes, respectively. The feasibility of cw operation at higher temperatures and directions for improving IC laser performance are discussed based on the experimental data.
White cypress pine (Callitris glaucophylla): a review of its roles in landscape and ecological processes in eastern Australia
Authors: Thompson W. A. , Eldridge D. J.
Published: October 2005

Callitris glaucophylla (J.Thompson & L.Johnson, white cypress pine) woodlands are an important vegetation community over relatively large areas of continental eastern Australia. C. glaucophylla communities were originally reserved because of their value to the timber industry, but renewed attention is being placed on these woodlands because of their putative role in the conservation of native plants and animals. The pre-European distribution of C. glaucophylla was altered dramatically in the past century because of a combination of grazing by domestic livestock and feral animals, altered fire regimes and weed invasion. Today, the majority of C. glaucophylla woodlands are highly fragmented remnants, with many managed as formal forestry reserves. Selective logging during the past 30 years has led to a community that is dominated by single-aged stands, often at high densities, leading to the perception that C. glaucophylla communities are severely degraded and floristically depauperate. Increased interest in the structure and function of grassy woodlands in eastern Australia over the past decade has led to a re-evaluation of the importance of this vegetation community for habitat and for maintaining essential ecosystem processes. The timing of this review is appropriate because (1) much has been published on the ecological role of C. glaucophylla over the past decade in Australia, although mostly in unpublished reports, and (2) there is a need to resolve some of the conflicting issues relating to the value of C. glaucophylla woodlands for healthy soils and vegetation. Here, we review the ecological role of C. glaucophylla, with an emphasis on eastern Australia, drawing on a range of published and unpublished literature. We describe the characteristics and distribution of C. glaucophylla in eastern Australia, its role in soil and ecological processes, and the impacts of fire and grazing. Finally, we discuss the management of C. glaucophylla for a range of landuses.
Size/age distribution and vegetative recovery of Eucalyptus niphophila (snowgum, Myrtaceae) one year after fire in Kosciuszko National Park
Authors: Pickering Catherine Marina , Barry Kristy
Published: October 2005

Size/age distribution and vegetative regeneration were examined for 50 Eucalyptus niphophila Maiden & Blakely trees in each of eight subalpine sites in Kosciuszko National Park 1 year after the January–February 2003 bushfires. Trees sampled were generally large and mature, with an average of 2.5 trunks, lignotuber diameter of 54 cm and largest trunk diameter of 18 cm, with a few larger trees at all sites. Converting the girth of largest trunk into rough age estimates by using an existing regression formula gave an approximate minimum (~29 years), maximum (~186 years), median (~58 years) and average age of ~64 years (error of ~15 years). For trees with trunks after fire, 96.5% had lost all existing leaves. Nearly all trees (95%) had shoots from the lignotuber, but only 4.25% of trees had also epicormic shoots on trunks and stems. Size/age were related to some but not all measures of regeneration. In the future, existing trunks could senesce, with nearly all regrowth from the lignotubers. This could result in a change from open woodlands with large/old trees with a few trunks to closed woodlands of lower-growing trees with a mallee form.
Grassland species response to soil disturbance and nutrient enrichment on the Northern Tablelands of New South Wales
Authors: Chalmers A. , McIntyre S. , Whalley R. D. B. , Reid N.
Published: October 2005

An experiment was established in an area of long-grazed temperate grassland on the Northern Tablelands of New South Wales to investigate individual species response to mechanical soil disturbance and nutrient enrichment. Grazing was excluded for the duration of the experiment. The total species pool available in the experiment included 56 native and 24 exotic species recorded in the plots, as well as seven exotic species that were artificially introduced (i.e. sowing treatment). Eighteen months after treatment, total species richness was significantly lower under high soil disturbance (mean of 14.7 ± 0.85 species m–2) than under low (21.1 ± 0.67 species m–2) and moderately (21.7 ± 0.77 species m–2) disturbed conditions. Total species richness was not significantly affected by nutrient enrichment or sowing. Most of the annuals analysed were exotic and their relative cover increased with nutrient enrichment (Aira cupaniana Guss., Briza minor L. and Vulpia spp.), but was unresponsive to soil disturbance. Perennials showed varied responses, with the abundance of most decreasing with high soil disturbance and being unaffected by moderate soil disturbance levels. All four perennials favoured by high soil disturbance were exotic (Dactylis glomerata L., Lolium perenne L., Hypochaeris radicata L. and Sanguisorba minor Scop.); three of these were sown. Most perennials showed no significant response to nutrient enrichment, although the occurrence of a small number was either reduced (Aristida ramosa R.Br., A. warburgii Mez., H. radicata and S. minor) or increased (Carex inversa R.Br., D. glomerata, Fimbristylis dichotoma (L.) Vahl., Sporobolus creber De Nardi and Tricoryne elatior R.Br.). Most interactions (i.e. species response to one experimental factor depends on another experimental factor) occurred because few individuals survived on the severely soil-disturbed plots to respond to nutrient enrichment. However, in this particular grassland, the short-term response of most species to soil disturbance was independent of the level of nutrient enrichment.