bluuebunny/crossref_metadata_2025 huggingface dataset:
Nerves Immunoreactive to Vasoactive Intestinal Polypeptide in the Porcine Female Genital Tract
Authors: Rodriguez-Martinez H.
Published: July 2008

The immunoreactivity of vasoactive intestinal polypeptide (VIP) was localized at the light-microscopical level in cryostat sections using a peroxidase-antiperoxidase technique or at the electron-microscopical (EM) level in glutaraldehyde-fixed, resin-embedded sections, using an immunogold technique, of tissue samples from the genital tract of cycling pigs. X-ray micro-analysis of glutaraldehyde-dichromate-fixed sections was used to discriminate nor-adrenaline-containing nerves. VIP immunoreactivity was localized to nerves associated to some degree with epithelial cells, blood vessels and non-vascular smooth muscle. VIP nerves were most concentrated in the cervix and the uterus, localized in the submucosa, the muscle layers and the adventitia. Nerve profiles were also seen accompanying blood vessels in the endometrium, running close to the uterine glands. In the oviduct, VIP nerves had a similar localization though less dense. At the EM level, the immunogold localization confirmed the above-mentioned results, VIP being localized in synaptic vesicles. Nerve terminals without VIP reactivity had an EM appearance of cholinergic nerve terminals or were chrome positive (noradrenaline-containing) at X-ray micro-analysis, thus being adrenergic terminals. It is concluded that the porcine female genital tract is well innervated, along with adrenergic and cholinergic components, by VIP-containing nerves.
Size Control of Au Nanoparticles on TiO2 and Al2O3 by DP Urea: Optical Absorption and Electron Microscopy as Control Probes
Authors: Reyes-Esqueda Jorge Alejandro , Salvador Amado Bautista , Zanella Rodolfo
Published: July 2008

Gold nanoparticles supported on TiO2 and Al2O3 were prepared by using the deposition-precipitation with urea (DP Urea) method. The control of the particle size was achieved by varying both, the stirring time during the deposition-precipitation (DP) procedure
and the conditions of thermal treatment. We focused mainly on the stirring time and the treatment temperature, although gas flow and type of atmosphere also influence importantly the particle's size and shape, as we shall show. The optical response of metallic nanoparticles is given by its
surface plasmon resonance and its position and shape depends strongly on the size and the shape of the nanoparticle, as well as on its surrounding. Then, we followed the control of the nanoparticles size by using mainly optical absorption measurements, which gave us account of the size and
the shape of the nanoparticles and the effect of the support on their optical response. These optical results were compared to, and supported with, TEM micrographs of our samples.
Synthesis and Properties of Nanocrystalline Copper Indium Oxide Thin Films Deposited by Rf Magnetron Sputtering
Authors: Singh Mandeep , Singh V. N. , Mehta B. R.
Published: July 2008

Nanocrystalline copper indium oxide (CuInO2) thin films with particle size ranging from 25 nm to 71nm have been synthesized from a composite target using reactive Rf magnetron sputtering technique. X-ray photoelectron spectroscopy (XPS) combined with glancing angle X-ray
diffraction (GAXRD) analysis confirmed the presence of delafossite CuInO2 phase in these films. The optical absorption studies show the presence of two direct band gaps at 3.3 and 4.3 eV, respectively. The resistance versus temperature measurements show thermally activated hopping
with activation energy of 0.84 eV to be the conduction mechanism.
Upconversion White Light Devices: Ln3+-Tridoped NaYF4 Nanoparticles and PVP Modified Films
Authors: Dong Biao , Song Hongwei , Qin Ruifei , Bai Xue , Lu Shaozhe , Ren Xinguang , Pan Guohui , Zhang Hui , Wang Fang , Fan Libo
Published: July 2008

Upconversion (UC) white light hybrid thin films containing Ln3+-tridoped (Yb3+, Er3+ and Tm3+) NaYF4 nanoparticles and poly(vinyl pyrrolidone) (PVP, Mw ≈ 1300 000) were prepared by a spin-coating method and
characterized by X-ray diffraction (XRD), field emission scanning electron micrograph (FE-SEM) and Fourier transform infrared spectra (FT-IR). White light was generated by two different lanthanide ions, Er3+ (red and green) and Tm3+ (blue) under excitation by a 980-nm
laser diode. Due to the modification of PVP to the UC populating processes, the color stability of the white light in the hybrid films was remarkably improved.
Nanoparticles of Pd: Synthesis by Microwave-Solvothermal Method and Optical Properties
Authors: Li Dongsheng , Komarneni Sridhar
Published: July 2008

Well-dispersed Pd nanoparticles were synthesized by microwave-assisted solvothermal technique using methanol and ethanol. Particle size and morphology were controlled mainly by the reaction temperature. Particle size of Pd nanoparticles was controlled in the range of 2 to 11 nm by manipulating
the reaction conditions. The Pd nanoparticles were characterized by transmission electron microscopy for particle size and shape and UV-Vis spectroscopy for optical properties. UV-Vis spectra showed that synthesized Pd nanoparticles stabilized with PVP had absorption bands at around 280 to
290 nm.
AFM Anodization Lithography on Transparent Conductive Substrates
Authors: Yamamoto Takamichi , Maekawa Hideki , Yamamura Tsutomu
Published: July 2008

In the present study, AFM anodization lithography was carried out on transparent conductive oxide substrates for the first time. ITO glasses were utilized as the transparent substrates. The surface of the ITO glass substrate was organically modified using the SAM (self-assembled monolayer)
method. The wettability of the surfaces was controlled by changing the organic molecule used in the SAM method. An arbitrary nanopattern was fabricated using AFM anodization lithography on the organically modified ITO glass surface. Hydrophilic-hydrophobic nanopatterns on transparent substrates
are potentially useful for optical observations of various substances adsorbed on nanostructures.
Synthesis and Characterization of ZnO Nano-Plant-Like Electrodes
Authors: Tiwari Ashutosh , Snure Michael
Published: July 2008

Dye-sensitized solar cells (DSSCs) have received considerable attention as a cost-effective alternative to conventional inorganic solar cells. These cells operate on a process similar to photosynthesis, the process by which green plants generate chemical energy from sunlight. A thick
semiconductor nanoparticle film provides a large surface area for the adsorption of energy by light harvesting organic dye molecules which then "inject" electrons into the nanostructured semiconductor electrode. This process is accompanied by a charge transfer to the dye from an electron donor
mediator supplied by an electrolyte, resetting the cycle. A significant increase in the long term stability and the efficiency of DSSCs has been realized during the last few years. However, still the current nanoparticle-based DSSCs suffer from the trap-limited diffusion transport mechanism
of electrons, a slow mechanism that limits the device efficiency, especially at longer wavelengths. Recently we have developed a new version of the dye-sensitized cells in which the traditional electrode (sintered nanoparticle film) is replaced by a specially designed ZnO electrode possessing
an exotic 'nanoplant-like' morphology. This advance fixes a major efficiency limiting factor in current nanoparticle-based DSSCs. The direct electrical pathway, provided by the interconnected nanoplants, provides rapid collection of carriers generated throughout the device, and significantly
enhances the conversion efficiency of the system over that of sintered nanoparticle based solar cells.
Effects Intracerebral Microinjection and Intraperitoneal Injection of [60]Fullerene on Brain Functions Differ in Rats
Authors: Yamada Takashi , Jung Duk-Young , Sawada Rumi , Matsuoka Atsuko , Nakaoka Ryusuke , Tsuchiya Toshie
Published: July 2008

Fullerenes are condensed ring aromatic compounds with extended π systems and unique cage structures. Fullerenes are used for medical devices such as carbon nanotubes because they are very flexible and suitable for drug delivery systems. Recently, fullerene derivatives and
tube-shaped materials have been used for neuroregeneration studies, and we expect that fullerenes and carbon nanotubes have potential uses as materials in novel medical devices targeting the brain. However, little information on the effects of fullerenes on brain function is available; thus,
we examined the effects of [60]fullerene (C60) on the central nervous system in this study. In a V79 cell colony Asia, the IC50 of C60 was 1620 μg/ml. In an in vivo study, 0.25 mg/kg B.W. of C60 was injected into the lateral brain
ventricle or abdominal cavity of rats. The intracerebral injection of C60 increased the locomotor behavior of the rats on days 1 and 30 after the injection. The intraperitoneal injection of C60 did not change the locomotor behavior of rats acutely, but it was decreased
on day 30. The intracerebral injection of C60 affected monoamine concentrations in the rat brain. In particular, serotonin turnover rates were increased in the hypothalamus, cerebral cortex, striatum, and hippocampus, and dopamine turnover rates were increased in the hypothalamus,
cerebral cortex, and striatum. The intraperitoneal injection of C60 decreased only the dopamine turnover rate in the hippocampus. These results suggest that intracerebral injection of C60 had different effects on the central nervous system than intraperitoneal injection.
In conclusion, it was suggested that fullerene did not cross the blood-brain barrier. The intracerebral injection of C60 affected neurotransmission in the brain widely, and the monoamine dysbolism might be related to changes in locomotor activity.
Physics Behind the Oscillation of Pressure Tensor Autocorrelation Function for Nanocolloidal Dispersions
Authors: Wang Tao , Wang Xinwei , Luo Zhongyang , Cen Kefa
Published: July 2008

In this work, extensive equilibrium molecular dynamics simulations are conducted to explore the physics behind the oscillation of pressure tensor autocorrelation function (PTACF) for nanocolloidal dispersions, which leads to strong instability in viscosity calculation. By reducing the
particle size and density, we find the intensity of the oscillation decreases while the frequency of the oscillation becomes higher. Careful analysis of the relationship between the oscillation and nanoparticle characteristics reveals that the stress wave scattering/reflection at the particle-liquid
interface plays a critical role in PTACF oscillation while the Brownian motion/vibration of solid particles has little effect. Our modeling proves that it is practical to eliminate the PTACF oscillation through suppressing the acoustic mismatch at the solid-liquid interface by designing special
nanoparticle materials. It is also found when the particle size is comparable with the wavelength of the stress wave, diffraction of stress wave happens at the interface. Such effect substantially reduces the PTACF oscillation and improves the stability of viscosity calculation.
Microwave Permittivity, Permeability, and Absorption of Ni Nanoplatelet Composites
Authors: Huang Juanjuan , Qin Yong , Li Jiangong , Jiang Xingdong , Ma Fei
Published: July 2008

The Ni nanoplatelets with an average diameter of 75 nm and an average thickness of 10 nm are coated with MnO2 by a simple solution phase chemical method. The MnO2-coated Ni nanoplatelets are dispersed in paraffin wax to form the composite samples of the magnetic
filler dispersed in the nonmagnetic insulating matrix. The effect of the Ni nanoplatelet volume fraction on the complex permittivity, complex permeability, and microwave absorption of the composites has been studied in the frequency range of 0.1–10 GHz. The complex permittivity of the
composites with different volume fractions of the Ni nanoplatelets is almost constant in the 0.1–10 GHz frequency range. The complex permeability of the composites shows several resonance peaks. Besides the natural resonance peak, the exchange resonance peaks are observed. The composite
with 17% volume fraction of Ni nanoplatelets has excellent microwave absorption properties of a minimum reflection loss value −31 dB at 9.1 GHz for a thickness of 2 mm and a broad absorption bandwidth of 2.3–10 GHz (R < −10 dB). The Ni nanoplatelets are a possible
candidate as high performance microwave absorption filler. For the Ni nanoplatelet composites, the magnetic loss is the dominant term for microwave absorption.
Selective Growth of Vertically Aligned Carbon Nanotubes by Double Plasma Chemical Vapour Deposition Technique
Authors: Cabral Gil , Titus Elby , Misra D. S. , Gracio J.
Published: July 2008

The selective growth of vertically aligned carbon nanotubes (VACNTs) on large area copper substrates was carried out using a double plasma hot-filament chemical vapour deposition system. Three independent power supplies were used to produce two glow discharges within the vacuum reactor.
The generation of two glow discharges and the efficient utilization of the electric fields, by controlling the key process parameters, enabled the production of VACNTs. Morphology, density and structure of carbon nanotubes were characterized using Scanning Electron Microscopy and Raman Spectroscopy.
Static and Dynamic Magnetic Properties of Co Nanoparticles
Authors: Srinath S. , Poddar P. , Sidhaye Deepti S. , Prasad B. L. V. , Gass J. , Srikanth H.
Published: July 2008

Co nanoparticles have been synthesized using wet-chemical methods. As-synthesized particles show a sharp low temperature peak in zero-field cooled (ZFC) magnetization well below the blocking transition temperature and this feature is associated with surface spin disorder. We have investigated
the dynamic magnetic properties of Co using ac susceptibility and resonant RF transverse susceptibility (TS). We also studied the memory and relaxation effects in these nanoparticle systems. From these measurements we show a typical blocking behavior of an assembly of superparamagnetic nanoparticles
with a wide distribution of blocking temperatures. The transverse susceptibility measurements on these particles show the presence of anisotropy even above the blocking temperature. The role of surface anisotropy and the size distribution of the particles on the observed memory and magnetic
relaxation effects are discussed.
Optical Characterization of Oxide Encapsulated Silicon Nanowires of Various Morphologies
Authors: King Sharon M. , Chaure Shweta , Krishnamurthy Satheesh , Blau Werner J. , Colli Alan , Ferrari Andrea C.
Published: July 2008

The optical properties of four different silicon nanowire structures were investigated. Two of the samples consisted of spheres of nanocrystalline silicon en-capsulated by silicon oxide nanowires, with other two consisting of crystalline silicon nanowires coated by silicon oxide shells.
The nanostructures produced by oxide assisted growth consisted of spheres of crystalline silicon encapsulated by silicon oxide shells. The absorption and photoluminescence of the different structures of the sample are investigated. The emitting species responsible for photoluminescence across
the visible spectrum are discussed.
Excimer Laser Irradiation Effects on Soft Magnetic Properties of Sputtered Iron Nitride Thin Films
Authors: Dubey Ranu , Gupta Ajay , Phase D. M. , Prakash Ram
Published: July 2008

Effect of pulse laser irradiation on soft magnetic properties of reactively sputtered iron nitride thin film has been studied. The as-deposited films exhibit large coercivity in the range 54 Oe to 148 Oe. Laser irradiation results in remarkable decrease in the coercivity of the films,
the minimum value achieved being 8 Oe. X-ray diffraction measurements evidence structural relaxation in the films, resulting in densification. Surface roughness of the films exhibits only a marginal increase after laser irradiation. The observed decrease in the coercivity may be attributed
to the relaxation of some quenched-in stresses associated with structural relaxation in the films. Irradiation as a function of energy density of laser pulse shows that an optimum energy density is required to achieve the best soft magnetic properties, which can vary from sample to sample.
Silicon Nanocluster Prepared Using Ion Beam Mixing Technique
Authors: Warang Trupti N. , Joshi K. U. , Kothari D. C.
Published: July 2008

In this work, we present the results of modification of absorption band gap of Silicon nanoclusters (Si-nc) prepared by ion beam mixing on pre-irradiated fused silica. 30keV Ar+ ions at fluences of 5 × 1016 to 4 × 1017 cm−2
were used to create defects in fused silica glass before introducing Si atoms in the substrate. Si was introduced in the substrates by ion beam mixing using 30keV Ar+ ions at fluence 1 × 1017 cm−2. From UV-Vis absorption spectra, band-gap of Si-nc
has been determined for samples prepared at different ion beam-mixing parameters. The absorption edge shifts towards higher energies and size of the silicon nanoclusters decreases with an increase in ion beam fluence used for pre-mixing irradiation.
Infrared Spectroscopy and Elastic Properties of Nanocrystalline Mg–Mn Ferrites Prepared by Co-Precipitation Technique
Authors: Pathak T. K. , Buch J. J. U. , Trivedi U. N. , Joshi H. H. , Modi K. B.
Published: July 2008

Nanoparticles having particle size in the range 25–40 nm for compositions x = 0.0, 0.2, 0.4 and 0.5 of MgxMn1−xFe2O4 spinel ferrite system have been prepared by chemical co-precipitation route. The microstructure,
infrared spectral and elastic properties have been studied by means of energy dispersive analysis of X-rays (EDAX), transmission electron microscopy (TEM), X-ray diffraction (XRD) and infrared spectroscopic (IR) measurements, before (W) and after high temperature annealing A(W).
The force constants for tetrahedral and octahedral sites determined by infrared spectral analysis, lattice constant and X-ray density values by X-ray diffraction pattern analysis; have been used to calculate elastic constants. The magnitude of force constant and elastic moduli for nanocrystalline
W-samples are found to be larger as compared to coarse grained A(W)-samples. The results have been explained in the light of redistribution of cations and as a result change in mean ionic charge for such cationic sites, elastic energy and grain size reduction effect of Nanoparticles.
Investigations on Silicon/Amorphous-Carbon and Silicon/Nanocrystalline Palladium/Amorphous-Carbon Interfaces
Authors: Roy M. , Sengupta P. , Tyagi A. K. , Kale G. B.
Published: July 2008

Our previous work revealed that significant enhancement in sp3-carbon content of amorphous carbon films could be achieved when grown on nanocrystalline palladium interlayer as compared to those grown on bare silicon substrates. To find out why, the nature of interface formed
in both the cases has been investigated using Electron Probe Micro Analysis (EPMA) technique. It has been found that a reactive interface in the form of silicon carbide and/silicon oxy-carbide is formed at the interface of silicon/amorphous-carbon films, while palladium remains primarily in
its native form at the interface of nanocrystalline palladium/amorphous-carbon films. However, there can be traces of dissolved oxygen within the metallic layer as well. The study has been corroborated further from X-ray photoelectron spectroscopic studies.
Study of Self-Organized CdS Q-Dots
Authors: Kaushik Diksha , Sharma Madhulika , Sharma A. B. , Pandey R. K.
Published: July 2008

Self-organized cadmium sulfide quantum dots assembled using wet synthesis route on glass/ITO as well as Si(100) substrates have been investigated, using X-ray diffraction and transmission electron microscopy. The quantum dots have been shown to grow with a strong (111) orientation with
narrow size distribution. Self-organized growth of the quantum dots was examined by high resolution imaging with an atomic force microscope. It is shown that increased self-organization is obtained on silicon substrate. The role of surfactant in imparting self-organization has been invoked
to explain the observed morphological features. The as grown Q-dots exhibited size dependent blue shift in the absorption edge. The luminescence behavior of the quantum dots self-organized on glass/ITO as well as Si(100) substrate has also been examined. It is shown that substantial enhancement
in luminescence yield is obtained for quantum dots grown on silicon substrate. A model to explain the observed luminescence enhancement has also been presented.
Electron Field Emission from Graphitic Nanoflakes Grown Over Vertically Aligned Carbon Nanotubes
Authors: Chhoker S. , Arora S. K. , Srivastava P. , Vankar V. D.
Published: July 2008

Single step growth of self-assembled graphitic nanoflakes (GNF) over carbon nanotubes (CNT) on iron coated silicon(100) substrates is reported. These nanostructures were grown by varying the deposition time in a microwave plasma enhanced chemical vapor deposition reactor using acetylene,
hydrogen and argon as reactant gases. Scanning electron microscope (SEM) studies of the deposited carbon films revealed that with increase in deposition time from 3 minutes to 6 minutes, the surface topography of the films transformed from one dimensional cylindrical nanostructure to flat-shaped
two-dimensional nanoflakes. Carbon film deposited for 5 minutes showed improved surface coverage as compared to films deposited for 6 minutes i.e., surface area of the CNT film covered with nanoflakes increased as compared to carbon film deposited for higher durations. Field emission studies
of films deposited at 5 minutes and 6 minutes showed increase in turn-on field, required for electron emission, from 2.7 V/μm to 2.9 V/μm respectively. However, such a combination of one dimension carbon and two dimension carbon may prove useful in applications where high
surface area films are required.
Shape and Size Distribution of Molecular Beam Epitaxy Grown Self-Assembled Ge Islands on Si (001) Substrates
Authors: Singha R. K. , Das S. , Das K. , Majumdar S. , Dhar A. , Ray S. K.
Published: July 2008

We have performed a series of annealing experiments with Ge islands on Si (001) grown by molecular beam epitaxy, in order to clarify issues related to island stability and coarsening. The shape and size distribution of nanoislands as a function of annealing time at a temperature of
650 °C have been studied. Optical phonons from Raman spectra have been used as efficient probes to study the evolution of Si1−xGex islands. Both the alloy composition and residual strain in the islands have been determined from the phonon frequencies
and Raman intensities. The experimental results are in good agreement with the strain relaxation estimated using X-ray rocking curves. The results indicate that the shape and size distribution of Ge islands are controlled via structural and compositional changes through strain relaxation by
the periodic creation and extinction of tiny nanocrystals.
Poly(ethylene) Glycol/Single-Walled Carbon Nanotube Composites
Authors: Chakraborty Amit K. , Coleman Karl S.
Published: July 2008

Single-walled carbon nanotubes have been shown to exhibit extraordinary electronic and mechanical properties. However, their relative inertness limits their use in many applications. Chemical functionalization can significantly modify their properties which, in addition to improving
their processibility, when mixed in polymers can enhance the overall mechanical and electrical properties of the composites. In this work, we present the results of our investigation on the chemical modification of single-walled carbon nanotubes with aryl groups containing nitro substituents,
and the incorporation of the modified nanotube material into a host matrix of poly(ethylene) glycol. The carbon nanotubes and composites were characterized by a combination of cyclic voltammetry, thermogravimetric analysis (TGA), Raman spectroscopy, Dynamic Mechanical Analysis (DMA) and electrical
resistance (I–V) measurements.
Structural Influence on the Magnetic and Electronic Properties of Annealed Fe/Al Multilayers
Authors: Brajpuriya R. , Tripathi S. , Sharma A. , Chaudhari S. M. , Shripathi T.
Published: July 2008

Temperature dependent magnetic and electronic properties of electron beam evaporated Fe/Al multilayer samples (MLS) with an average composition of Fe0.70A10.30 (MLS-A) and Fe0.50Al0.50 (MLS-B) have been investigated. A ferromagnetic behaviour
in MLS-A and nonmagnetic behaviour in MLS-B is obtained after annealing the multilayers at 400 °C. The different magnetic behaviours can be interpreted in terms of constant increase of Fe-3d and Al-3sp hybridization accompanied by an increased de-localization of the d-electrons
participating in the strong bonding of Fe with Al leading to formation of different Fe–Al phases (Fe3Al in MLS-A) and (FeAl in MLS-B) as suggested from valence band photoemission and X-ray diffraction measurements.
MeV Gold Ion Induced Sputtered Nanoparticles from Gold Nanostructures: Dependence of Incident Fluxand Temperature
Authors: Ghatak J. , Sundaravel B. , Nair K. G. M. , Satyam P. V.
Published: July 2008

The high-energy and heavy-ion induced sputtered particles from nanostructures under various conditions can result in variety of size distributions. 1.5 MeV Au2+ ions induced sputtering from isolated gold nanostructures deposited on silicon substrate have been studied as a
function of incident ion flux (dose rate) and the sputter particle catcher at low temperature. At higher fluxes, a bimodal distribution of the sputtered particles has been observed. Cross-sectional transmission electron microscopy and Rutherford backscattering spectrometry measurements showed
that the sputter particle size distribution depends on morphology at surface and interfaces. The results for the size distribution from a catcher at low temperature showed the less agglomeration of ejected clusters on the catcher grids, resulting in the lower-disperse size distribution.
Growth and Characterization of Manganese Doped Gallium Nitride Nanowires
Authors: Suresh Kumar V. , Kesavamoorthy R. , Kumar J.
Published: July 2008

Manganese doped GaN nanowires have been grown by chemical vapour transport method on sapphire (0001) substrates in the temperature range of 800–1050 °C. The surface features of nanowires have been investigated using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray
analysis (EDAX), Raman scattering studies and Electron Paramagnetic Resonance (EPR). SEM images showed that the morphology of the one dimensional materials included straight nanorods and nanowires around 70–80 nm. Raman spectrum showed the GaMnN vibrational modes at 380, 432 and 445
cm−1. EPR measurements were performed on Mn doped GaN nanowires in order to evaluate the magnetic behaviour.
Effect of Fuel to Oxidizer Ratio on the Structure, Micro Structure and EPR of Combustion Synthesized NiO Nanoparticles
Authors: Venkateswara Rao K. , Sunandana C. S.
Published: July 2008

In this work we describe the synthesis, micro structure (XRD, SEM) and EPR of NiO nanoparticles synthesized by urea-based combustion method using Ni nitrate as the source of Ni. We used fuel-to-oxidizer ratio (Ψ) as a control parameter to investigate how lattice parameter, particle
size and EPR susceptibility vary with Ψ = 0.25 to 2. Earlier we have studied NiO as a substitutional solute in MgO. The average particle size of NiO was estimated from the full width half maximum (gaussian and lorentzian fits) of the X-ray diffraction peaks of powders using Sherrer's formula
and Williamson-Hall plot. The particle size varies from 7 nm to 38 nm as Ψ is varied systematically. The surface areas were measured using BET method. FT-IR confirms the Ni-O crystalline bond formation. We also calculated porosity and strain in the NiO nanoparticles with varying Ψ.
EPR spectra have yielded the susceptibility of the NiO nanoparticles. Band gap of NiO was determined by UV-visible absorption edge.
Downslope Flows on a Low-Angle Slope and Their Interactions with Valley Inversions. Part I: Observations
Authors: Whiteman C. David , Zhong Shiyuan
Published: July 2008

Thermally driven downslope flows were investigated on a low-angle (1.6°) slope on the west side of the floor of Utah’s Salt Lake Valley below the Oquirrh Mountains using data from a line of four tethered balloons running down the topographic gradient and separated by about 1 km. The study focused on the evolution of the temperature and wind structure within and above the slope flow layer and its variation with downslope distance. In a typical situation, on clear, undisturbed October nights a 25-m-deep temperature deficit of 7°C and a 100–150-m-deep downslope flow with a jet maximum speed of 5–6 m s−1 at 10–15 m AGL developed over the slope during the first 2 h following sunset. The jet maximum speed and the downslope volume flux increased with downslope distance. The downslope flows weakened in the late evening as the stronger down-valley flows expanded to take up more of the valley atmosphere and as ambient stability increased in the lower valley with the buildup of a nocturnal temperature inversion. Downslope flows over this low-angle slope were deeper and stronger than has been reported previously by other investigators, who generally investigated steeper slopes and, in many cases, slopes on the sidewalls of isolated mountains where the downslope flows are not subject to the influence of nighttime buildup of ambient stability within valleys.
Effects of Future Climate and Biogenic Emissions Changes on Surface Ozone over the United States and China
Authors: Lin Jin-Tai , Patten Kenneth O. , Hayhoe Katharine , Liang Xin-Zhong , Wuebbles Donald J.
Published: July 2008

Future projections of near-surface ozone concentrations depend on the climate/emissions scenario used to drive future simulations, the direct effects of the changing climate on the atmosphere, and the indirect effects of changing temperatures and CO2 levels on biogenic ozone precursor emissions. The authors investigate the influence of these factors on potential future changes in summertime daily 8-h maximum ozone over the United States and China by comparing Model for Ozone and Related Chemical Tracers, version 2.4, (MOZART-2.4) simulations for the period 1996–2000 with 2095–99, using climate projections from NCAR–Department of Energy Parallel Climate Model simulations driven by the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios A1fi (higher) and B1 (lower) emission scenarios, with corresponding changes in biogenic emissions. The effect of projected climate changes alone on surface ozone is generally less than 3 ppb over most regions. Regional ozone increases and decreases are driven mainly by local warming and marine air dilution enhancement, respectively. Changes are approximately the same magnitude under both scenarios, although spatial patterns of responses differ. Projected increases in isoprene emissions (32%–94% over both countries), however, result in significantly greater changes in surface ozone. Increases of 1–15 ppb are found under A1fi and of 0–7 ppb are found under B1. These increases not only raise the frequency of “high ozone days,” but are also projected to occur nearly uniformly across the distribution of daily ozone maxima. Thus, projected future ozone changes appear to be more sensitive to changes in biogenic emissions than to direct climate changes, and the spatial patterns and magnitude of future ozone changes depend strongly on the future emissions scenarios used.
Continental Passive Microwave-Based Rainfall Estimation Algorithm: Application to the Amazon Basin
Authors: Biscaro Thiago S. , Morales Carlos A.
Published: July 2008

This paper presents a new statistical algorithm to estimate rainfall over the Amazon Basin region using the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI). The algorithm relies on empirical relationships derived for different raining-type systems between coincident measurements of surface rainfall rate and 85-GHz polarization-corrected brightness temperature as observed by the precipitation radar (PR) and TMI on board the TRMM satellite. The scheme includes rain/no-rain area delineation (screening) and system-type classification routines for rain retrieval. The algorithm is validated against independent measurements of the TRMM–PR and S-band dual-polarization Doppler radar (S-Pol) surface rainfall data for two different periods. Moreover, the performance of this rainfall estimation technique is evaluated against well-known methods, namely, the TRMM-2A12 [the Goddard profiling algorithm (GPROF)], the Goddard scattering algorithm (GSCAT), and the National Environmental Satellite, Data, and Information Service (NESDIS) algorithms. The proposed algorithm shows a normalized bias of approximately 23% for both PR and S-Pol ground truth datasets and a mean error of 0.244 mm h−1 (PR) and −0.157 mm h−1 (S-Pol). For rain volume estimates using PR as reference, a correlation coefficient of 0.939 and a normalized bias of 0.039 were found. With respect to rainfall distributions and rain area comparisons, the results showed that the formulation proposed is efficient and compatible with the physics and dynamics of the observed systems over the area of interest. The performance of the other algorithms showed that GSCAT presented low normalized bias for rain areas and rain volume [0.346 (PR) and 0.361 (S-Pol)], and GPROF showed rainfall distribution similar to that of the PR and S-Pol but with a bimodal distribution. Last, the five algorithms were evaluated during the TRMM–Large-Scale Biosphere–Atmosphere Experiment in Amazonia (LBA) 1999 field campaign to verify the precipitation characteristics observed during the easterly and westerly Amazon wind flow regimes. The proposed algorithm presented a cumulative rainfall distribution similar to the observations during the easterly regime, but it underestimated for the westerly period for rainfall rates above 5 mm h−1. NESDIS1 overestimated for both wind regimes but presented the best westerly representation. NESDIS2, GSCAT, and GPROF underestimated in both regimes, but GPROF was closer to the observations during the easterly flow.
Radar Measurement of Rainfall with and without Polarimetry
Authors: Ulbrich Carlton W. , Atlas David
Published: July 2008

Raindrop size distributions (DSDs) for tropical convective storms are used to examine the relationships between the parameters of a gamma DSD, with special emphasis on their variation with the stage of the storm. Such a distinction has rarely been made before. Several storms from a variety of tropical locations are divided into storm stages according to the temporal dependence of their reflectivity factor Z, rainfall rate R, and median volume diameter D0. In most cases it is found that the DSD parameter D0 is approximately constant in time during the convective, or C, stage, which leads to a Z–R relation of the form Z = AR, that is, a linear relationship between Z and R. This finding implies the existence of equilibrium DSDs during the C stage. The convective stage is sometimes marked by pulsations in draft strength so that D0, R, and Z and associated values of the shape parameter μ decrease in a quasi-transition stage before increasing once more. Theoretical relations between the differential reflectivity ZDR and the ratio Z/R as functions of the DSD parameter μ are derived by assuming a gamma DSD and an accurate raindrop fall speed law. It is found that data derived from disdrometer observations lie along a μ = 5 isopleth for tropical continental C stages (Puerto Rico and Brazil) and along a μ = 12 isopleth for tropical maritime C stages [Tropical Ocean and Global Atmosphere Coupled Ocean–Atmosphere Response Experiment (TOGA COARE)]. Small values of μ that occur in the weak updraft intervals do not impact the rainfall measurements because they correspond to relatively small R. The latter features imply that the measurement of rainfall for the convective stages can be performed with standard polarimetry involving only two measurables rather than three, provided knowledge of μ is available a priori. A new rain parameter diagram is presented in which isopleths of the generalized number concentration and D0 are superimposed on the Z–R plot. It is proposed that it is possible to estimate D0 from climatological and observable storm structural features, which, with Z, provide estimates of R. Such an approach is necessary for use with conventional radars until polarimetric radars are more widely available.
Physical Modeling of Flow Field inside Urban Street Canyons
Authors: Li Xian-Xiang , Leung Dennis Y. C. , Liu Chun-Ho , Lam K. M.
Published: July 2008

The flow characteristics inside urban street canyons were studied in a laboratory water channel. The approaching flow direction was horizontal and perpendicular to the street axis. The street width was adjusted to form street canyons of aspect ratios 0.5, 1.0, and 2.0. The velocity field and turbulent intensity were measured with a laser Doppler anemometer at various locations within the street canyons, which were used to elucidate the flow pattern inside the street canyons. It was found that the previous numerical modeling results are in good agreement with the current experimental results at most locations. For the street canyon of aspect ratio 0.5, which belongs to the wake interference flow regime, the mean and fluctuating velocity components were more difficult to measure as compared with the other two cases because of its more complicated flow pattern. Some guidelines for numerical modeling were developed based on the measurement results. The data presented in this paper can also be used as a comprehensive database for the validation of numerical models.
On the Role of Snow Cover in Depressing Air Temperature
Authors: Mote Thomas L.
Published: July 2008

This study empirically examines the role of snow depth on the depression of air temperature after controlling for effect of temperature changes above the boundary layer. In addition, this study examines the role of cloud cover, solar elevation angle, and maximum snow-covered albedo on the temperature depression due to snow cover. The work uses a new dataset of daily, gridded snow depth, snowfall, and maximum and minimum temperatures for North America from 1960 to 2000 in conjunction with 850-hPa temperature data for the same period from the NCEP–NCAR reanalysis, version 1. The 850-hPa temperatures are used as a control to remove the effect of temperature changes above the boundary layer on surface air temperatures. Findings from an analysis of variance demonstrate that snow cover can result in daily maximum (minimum) temperature depressions on average of 4.5°C (2.6°C) for snow depths greater than 10 cm over the grasslands of central North America, but temperature depressions average only 1.2°C (1.1°C) overall. The temperature depression of snow cover is shown to be reduced by increased cloud cover and decreased maximum albedo, which is indicative of denser forest cover. The role of snow melting on temperature depression is further explored by comparing days with maximum temperatures above or below freezing.
On the Dynamics of the Slope Current System along the West European Margin. Part I: Analytical Calculations and Numerical Simulations with Steady-State Forcing
Authors: Friocourt Yann , Drijfhout Sybren , Blanke Bruno
Published: July 2008

The dynamics of the baroclinic slope current system along the western European margin in the Bay of Biscay and along the northern Iberian Peninsula are investigated in two different models, one analytical and one numerical. Investigated here is the hypothesis that the steady-state slope current system is driven by the large-scale meridional density gradients. An analysis of the observed density fields evidences a four-layer structure with meridional gradients of alternate signs, which is also found in the numerical model. The linear analytical model of the continental margin shows that such a density structure is enough to obtain a steady-state four-layer slope current system comparable to the observed annual mean circulation. The slope currents result from a balance between bottom friction and meridional density gradients. The numerical simulation with an ocean general circulation model forced only by the large-scale density gradients at the lateral boundaries presents a four-layer slope current system similar to the circulation obtained in the analytical model. The study confirms that the large-scale meridional density gradients are the main driving mechanism for the steady-state slope current system; the large seasonality of these currents, however, requires a more extended model, which is discussed in a companion paper (Part II).
Rapidly Intensifying Hurricane Guillermo (1997). Part I: Low-Wavenumber Structure and Evolution
Authors: Reasor Paul D. , Eastin Matthew D. , Gamache John F.
Published: July 2008

The structure and evolution of rapidly intensifying Hurricane Guillermo (1997) is examined using airborne Doppler radar observations. In this first part, the low-azimuthal-wavenumber component of the vortex is presented. Guillermo’s intensification occurred in an environmental flow with 7–8 m s−1 of deep-layer vertical shear. As a consequence of the persistent vertical shear forcing of the vortex, convection was observed primarily in the downshear left quadrant of the storm. The greatest intensification during the ∼6-h Doppler observation period coincided with the formation and cyclonic rotation of several particularly strong convective bursts through the left-of-shear semicircle of the eyewall. Some of the strongest convective bursts were triggered by azimuthally propagating low-wavenumber vorticity asymmetries. Mesoscale budget analyses of axisymmetric angular momentum and relative vorticity within the eyewall are presented to elucidate the mechanisms contributing to Guillermo’s structural evolution during this period. The observations support a developing conceptual model of the rapidly intensifying, vertically sheared hurricane in which shear-forced mesoscale ascent in the downshear eyewall is modulated by internally generated vorticity asymmetries yielding episodes of anomalous intensification.
A Comparison of the Atmospheric Response to ENSO in Coupled and Uncoupled Model Simulations
Authors: Jha Bhaskar , Kumar Arun
Published: July 2008

In the Atmospheric Model Intercomparison Project (AMIP) simulations the sea surface temperatures (SSTs) are specified and the oceanic evolution consistent with air–sea interaction is not included. This omission could lead to errors in the atmospheric response to SSTs. At the same time, the AMIP experimental setup is well suited for investigating many aspects of climate variability (e.g., the attribution of the interannual atmospheric variability) and continues to be extensively used. As coupled El Niño–Southern Oscillation (ENSO) SST variability is a dominant factor in determining the predictable component of the observed interannual atmospheric variability, the difference in the atmospheric response to ENSO SSTs between AMIP and coupled simulations is investigated. The results indicate that the seasonal atmospheric response to ENSO between coupled and uncoupled integrations is similar, and the inclusion of oceanic evolution consistent with air–sea interaction does not play a dominant role. The analysis presented in this paper is one step toward assessing differences in atmospheric response to SSTs in coupled and uncoupled simulations, and is required to correctly interpret the results of AMIP simulations.
Contributions of Convectively Coupled Equatorial Rossby Waves and Kelvin Waves to the Real-Time Multivariate MJO Indices
Authors: Roundy Paul E. , Schreck Carl J. , Janiga Matthew A.
Published: July 2008

The real-time multivariate (RMM) Madden–Julian oscillation (MJO) indices have been widely applied to diagnose and track the progression of the MJO. Although it has been well demonstrated that the MJO contributes to the leading signals in these indices, the RMM indices vary erratically from day to day. These variations are associated with noise in the outgoing longwave radiation (OLR) and wind data used to generate the indices. This note demonstrates that some of this “noise” evolves systematically and is associated with other types of propagating modes that project onto the RMM eigenmodes. OLR and zonal wind data are filtered in the wavenumber–frequency domain for the MJO, convectively coupled equatorial Rossby (ER) waves, and convectively coupled Kelvin waves. The filtered data are then projected onto the RMM modes. An example phase space associated with these projections is presented. Linear regression is then applied to isolate the wave signals from random variations in the same bands of the wavenumber–frequency domain, and the regressed data are projected onto the RMM EOFs. Results demonstrate the magnitudes of the contributions of the systematically evolving signals associated with these waves to variations in the RMM principal components, and how these contributions vary with the longitude of the active moist deep convection coupled to the waves.
Alternate Site Pacing in Patients at Risk for Heart Failure
Authors: Manolis Antonis S. , Sakellariou Dimitrios , Andrikopoulos George K.
Published: July 2008

Cardiac pacing from the right ventricular apex is the most common site of cardiac pacing. During the last decade, several studies demonstrated the harmful effects of the iatrogenic left bundle branch block, which is observed in cardiac pacing from the right ven- tricular apex. These observations led to an interest in alternative right ventricular pacing sites aiming to achieve a more “physiological” pattern of ventricular activation. Alternate site pacing may involve His bun- dle, other right ventricular sites (outflow or septal sites), or left ventricular sites in either unifocal or bifo- cal or biventricular modes. Pacing from the right ven- tricular outflow tract has been studied extensively. Several studies showed that right ventricular outflow tract pacing has better hemodynamic effects and less harmful influence. Bifocal right ventricular (apical and outflow tract) pacing has been proposed for patients with heart failure where the coronary sinus approach to effect biventricular pacing turns out to be unsuccessful because of various reasons. Some studies examined left ventricular pacing alone as an alternative mode of pacing, and the results were quite encouraging but not conclusive. Finally, in heart failure patients not responding to biventricular pacing, the triple site pacing mode has been recently proposed. In triple site pacing, the leads are inserted in the right ventricular apex and outflow tract in conjunction with lateral left ventricular pacing. Improvement of exercise capacity and increased ejection fraction were observed with this triventricular pacing. Although more data from specifically designed randomized studies are needed, there are many alternative pacing sites, especially for patients at high risk of heart failure, which seems to be less harmful and better tolerated by the patients.
Repeat Offending and Repeat Victimization: Assessing Similarities and Differences in Psychosocial Risk Factors
Authors: Fagan Abigail A. , Mazerolle Paul
Published: July 2008

The overlap between victims and offenders is increasingly being recognized, with mounting evidence that victims and offenders have similar demographic characteristics, that victimization increases the likelihood of offending, and that offenders are at high risk for becoming victims of crime. Despite this evidence, there is limited research regarding the extent to which repeat victims are likely to be repeat offenders, and few studies have assessed whether predictors of repeat victimization and repeat offending are similar. Using data from a longitudinal study of young people in Brisbane, Australia, this study demonstrates that despite some overlap, there are some important differences in predictors of repeat offenders and repeat victims.