bluuebunny/crossref_metadata_2025 huggingface dataset:
Yield, characteristics and composition of oil‐ Type hybrid sunflower seed grown in north dakota
Authors: Dreher M. L. , Roath W. W. , Holm E. T. , D'Appolonia B.
Published: May 2008

Oil‐type sunflower seed hybrids grown in North Dakota were evaluated for yield, seed characteristics and composition. The study consisted of 74 hybrids grown at Casselton, ND, during 1981. Mean analytical values were: yield (x = 2047 kg/hectare), seed weight (x = 9.9 g/200 seed), test weight (x = 40.3 kg/hectare), hull (x = 26.7%), embryo (x =73.7%), oil (x = 45.3%), protein (x = 20.8%), ash (x = 3.5%), lysine (x = 4.5 g/100 g protein) and chlorogenic acid (x = 2.0%). Increasing the lysine content of hybrid sunflower protein appears to have possibilities for further study. The mean chlorogenic acid content was slightly lower than levels previously reported.
Studies on the antioxidants XVIII: Oxidation product of tertiary butyl hydroquinone (TBHQ) (I)
Authors: Kurechi T. , Aizawa M. , Kunugi A.
Published: May 2008

To explain the mechanism of antioxidants, it is important to know their chemical changes during the process of their prevention of autoxidation. Therefore, we have carried out a series of studies on these changes. In this study, the chemical structures and antioxidative activities of the oxides isolated by irradiation with ultraviolet rays were examined by using tertiary butyl hydroquinone (TBHQ). Two of the isolated products were identified as follows: one was a golden needle crystal, 2‐tert‐butyl‐p‐benzoquinone, and the other was a white prism‐like crystal, 2,2‐dimethyl‐5‐hydroxy‐2,3‐dihydrobenzo(b)furan, which was formed by dehydrogenation of the OH group and the methyl group in the rearranged tert‐butyl group at theortho position, so that furan rings were formed in the molecules. When the stability of these two products was tested on three different basic oils by the active oxygen method (AOM), quinone did not show any antioxidative activity, but the benzofuran derivative showed a strong antioxidative activity on lard and methyl oleate.
Studies on the Antioxidants XIX: Photooxidation products of tertiary butyl hydroquinone (TBHQ) (bdII)
Authors: Kurechi T. , Kunugi A.
Published: May 2008

A series of studies have been made with a view to pursuing the fate of antioxidant molecules during the antioxidation processes. In this study following that reported in the preceding paper, tertiary butyl hydroquinone (TBHQ) in benzene solution was irradiated with ultraviolet rays and the chemical structure and antioxidative activities of the resulting photooxidation products were examined. They were identified as the following three compounds: 2‐(2‐[3′‐tert‐butyl‐4′‐hydroxyphenoxy] ‐ 2‐methyl‐1 ‐propyl)hydroquinone, which was a dimer of the intermediate generated by photorearrangement of the tert‐butyl group and the substrate TBHQ, 2‐(2‐hydroxy‐2‐methyl‐l‐propyl)hydroquinone, which was formed by interaction of the rearranged tert‐butyl group with water, and2‐ tert‐ butyl‐ 4‐ ethoxy‐phenol, which was formed from a secondary decomposition of the dimer. All of the resulting oxidation products showed antioxidative activity on methyl oleate, soybean oil and lard in the stability test by the active oxygen method (AOM).
Analysis of sucrose mono‐ And diesters prepared from triglycerides containing C12‐C18 Fatty Acids
Authors: Gupta R. K. , James K. , Smith F. J.
Published: May 2008

A quantitative gas liquid Chromatographic method of analysis for sucrose mono‐ and diesters, prepared from naturally occurring triglycerides, is described. For esters containing predominantly C16C1s alkyl groups, a common calibration curve was obtained. Calibration standards were prepared by column chromatography using silica gel adsorbent. Methods of analysis for the major impurities present in the sucrose mono‐ and diesters are also described.
A contribution to the discussion of the glyceride structure of stearic‐rich animal depot fats
Authors: Hilditch T. P.
Published: May 2008

Comparative study of the constituent glycerides of a number of ox, sheep, and pig body fats which have been investigated in the Liverpool laboratories reveals that, while there is considerable accordance between the values observed for the trisaturated and monounsaturated groups of glycerides with those calculated from probability considerations, there is complete divergence between the latter and the values observed for the di‐ and triunsaturated glycerides.

The views on animal body fat glyceride structure developed and maintained by Hilditch and co‐workers are shown to be in harmony with the arithmetical relationships referred to (Table I), while they do not require the postulate that enzyme synthesis of glycerides should differ fundamentally in animal and in vegetable cells.

It is shown that apparent resemblance in the proportions of the four categories of saturated and unsaturated glycerides to those calculated on probability considerations may arise in a number of different ways, and that such resemblance has not necessarily any bearing on the mode of glyceride structure observed in fats.

The well‐established fact that mixed glycerides produced at high temperatures by synthesis or by acyl interchange approximate to “random” (probability) distribution also has no bearing upon the matter of the structure of mixed glycerides produced by the synthetic action of enzymes at or near atmospheric temperatures in the living cell.
Sodium palmitate in organic liquids as studied by X‐ray diffraction
Authors: Marsden Sullivan S.
Published: May 2008

The descendent phases of systems of sodium palmitate in 11 organic compounds have been studied by x‐ray diffraction. These consist of: 1. sodium palmitate in one of the three gamma crystalline forms; 2. an unknown component which may be a lamellar liquid crystal; and 3. the free organic compound.
Minor oil‐producing crops of the united states
Authors: Kester E. B.
Published: May 2008

Conclusion

This discussion of minor oil‐bearing crops by no means includes all that were considered and might conceivably have deserved treatment or at least passing mention. Omitted were seeds contained in agricultural products from which, in all likelihood, oil could never be obtained economically. Justification for such reasoning can in most cases be found in the scattered status of an industry processing the commodity from which the oil bearing part is derived, or the low magnitude of processing operationsvs. that of retail sales. For example, the seeds of watermelon, cantaloupe, and a wide assortment of berries were not included. A vast number of seeds of wild plants could have been discussed, but unless concentration of growth occurs either naturally or as a result of domestication or unless the derived oil seems to have outstanding characteristics, such as that of gopher plant seeds or jojoba beans, it is useless to consider them seriously as oil sources. Certain grain screenings such as water grass, which occurs plentifully in rice, were omitted because their oil content is too low for profitable recovery.

The evaluation of oils must usually be made on the same basis as the commoner bulk oils of commerce which they most closely resemble. As a rule vegetable oils differ from each other only in their contents of individually combined acids and their distribution in the oil as triglycerides or in having a high percentage of an unusual acid such as elaeostearic or hydnocarpic acid. Important variations, however, may occur in content of minor constituents such as oil‐soluble vitamins, antioxidants, or prooxidants, and it must be recognized that no oil can be completely evaluated until quantitative measurements covering such substances have been made where their presence is indicated.
The keeping quality of elaïdinated fats
Authors: Bertram S. H.
Published: May 2008

The causes of the considerably better keeping quality of elaïdinated oils and fats have been investigated through the rate of peroxide formation. They are physical as well as chemical in nature. The more solid composition of elaïdinated fats is the physical cause.

Traces of selenium have been proved to behave as a strong antioxidation agent. The elimination of traces of metals in the course of the process of elaïdination with Se also has a very favorable influence.

The elaïdo configuration of the unsaturated acids, however, has been shown to be the principal factor in retarding oxidation.
Model checking Duration Calculus: a practical approach
Authors: Meyer Roland , Faber Johannes , Hoenicke Jochen , Rybalchenko Andrey
Published: May 2008

Model checking of real-time systems against Duration Calculus (DC) specifications requires the translation of DC formulae into automata-based semantics. The existing algorithms provide a limited DC coverage and do not support compositional verification. We propose a translation algorithm that advances the applicability of model checking tools to realistic applications. Our algorithm significantly extends the subset of DC that can be checked automatically. The central part of the algorithm is the automatic decomposition of DC specifications into sub-properties that can be verified independently. The decomposition is based on a novel distributive law for DC. We implemented the algorithm in a tool chain for the automated verification of systems comprising data, communication, and real-time aspects. We applied the tool chain to verify safety properties in an industrial case study from the European Train Control System (ETCS).
Determination of Free Fatty Acids in Edible Oils with the Use of a Variable Filter Array IR Spectrometer
Authors: Li Yue , García‐González Diego L. , Yu Xiuzhu , van de Voort Frederik R.
Published: May 2008

The feasibility of employing a portable variable filter array (VFA) IR spectrometer equipped with a transmission flow cell to quantitatively analyze edible oils or biodiesel feedstocks for free fatty acids (FFA) was evaluated. The approach to FFA determination employed was based on a previously reported FTIR method that involves the extraction of FFAs into methanol containing the base NaHNCN, which converts the FFAs to their salts, followed by measurement of the carboxylate absorbance at ~1,573 cm−1 in the spectrum of the methanol phase. When this methodology was implemented on the low‐resolution VFA‐IR spectrometer, the analytical performance was comparable to that of conventional FTIR instrumentation at FFA concentrations of <1%. However, at higher FFA levels, the relatively weak pulsed IR source of the VFA‐IR spectrometer was found to provide insufficient energy for accurate measurement of the carboxylate absorption superimposed on the strong methanol absorption at ~1,450 cm−1. By changing the extraction solvent to ethanol (EtOH), good spectra and calibrations could be obtained over an FFA range of 0–5%, having an overall SD of ±0.07% FFA. Based on this assessment, a VFA‐IR spectrometer provides an economical instrumental means for at‐line monitoring of FFA levels in crude and refined edible oils and biodiesel feedstocks, capable of analyzing ~20–30 prepared samples per hour.
Synthesis and Structural Analysis of Structured Triacylglycerols with CLA Isomers in the sn‐2‐ Position
Authors: Blasi Francesca , Cossignani Lina , Bosi Ancilla , Maurelli Silvia , D’Arco Gilda , Fiorini Dennis , Simonetti Maria Stella , Damiani Pietro
Published: May 2008

The present research deals with the chemical esterification of the sn‐2‐ position of sn‐1,3‐diacylglycerol (sn‐1,3‐DAG) with 9cis,11trans (c9,t11) and 10trans,12cis (t10,c12) conjugated linoleic acid (CLA) isomers to obtain structured triacylglycerols (TAG); the sn‐1,3‐DAG substrates were produced from extra virgin olive oil by means of enzymatic reactions while CLA isomers were obtained using a three‐step procedure based on alkaline hydrolysis of sunflower oil, urea purification of linoleic acid (LA) and alkaline isomerization of LA. The results showed good levels of CLA incorporation in structured TAG at the tested temperatures: 37.5% at 4 °C and 39.1% at 14 °C. To evaluate the incorporation of CLA isomers in sn‐2‐ position of sn‐1,3‐DAG structural analysis of the newly synthesized TAG was carried out using an enzymatic and a chemical method. The results of the structural analysis also showed up the occurrence of acyl migration. The pancreatic lipase method allowed the direct determination of the fatty acid composition of TAG sn‐2‐ position but this enzymatic method showed different results (p < 0.05) in respect to the chemical one; this occurrence could be due to an acylic specificity of the lipase. High incorporation of CLA isomers in sn‐2‐ position of TAG was observed, 77.0% at 4 °C and 81.5% at 14 °C, considering the results of the chemical procedure.
Temporary decrease in daytime F‐region peak electron density due to eastward electric field penetration during magnetic storm
Authors: Jin H. , Maruyama T.
Published: May 2008

While a prompt penetration of an eastward electric field during a magnetic storm is known to increase the F‐region electron density, observations have shown that the F‐region peak density (NmF2) sometimes decreases before it increases, although total electron content (TEC) begins increasing immediately after the electric field penetration. We investigated potential mechanisms of the observed NmF2 decrease as well as of the TEC increase. Simulation showed that increased upward or downward diffusion flux in the topside ionosphere caused by layer uplift temporarily reduces the F‐region density at midlatitudes (mechanism A). In addition, the E × B motion toward an outer L shell region leads to flux tube expansion and plasma dilution, which also contribute to the NmF2 decrease (mechanism B). The TEC increase can be attributed to quick plasma production below the uplifted F2 peak. Simulation also showed that penetration events with an electric field magnitude greater than several mV/m can cause such a phenomenon. We also examined preferable conditions for this phenomenon, and found that degree of NmF2 decrease tends to become significant due to effect of mechanism A if a prompt electric field penetration occurs in the early morning or if the plasma temperature is high enough in the topside ionosphere.
Mechanisms of basal ice formation in polar glaciers: An evaluation of the apron entrainment model
Authors: Fitzsimons Sean , Webb Nicola , Mager Sarah , MacDonell Shelley , Lorrain Regi , Samyn Denis
Published: May 2008

Previous studies of polar glaciers have argued that basal ice can form when these glaciers override and entrain ice marginal aprons that accumulate adjacent to steep ice cliffs. To test this idea, we have studied the morphology, structure, composition, and deformation of the apron and basal ice at the terminus of Victoria Upper Glacier in the McMurdo dry valleys, which are located on the western coast of the Ross Sea at 77°S in southern Victoria Land, Antarctica. Our results show that the apron has two structural elements: an inner element that consists of strongly foliated ice that has a steep up‐glacier dip, and an outer element that lacks a consistent foliation and has a down‐glacier, slope‐parallel dip. Although strain measurements show that the entire apron is deforming, the inner element is characterized by high strain rates, whereas relatively low rates of strain characterize the outer part of the apron. Co‐isotopic analyses of the ice, together with analysis of solute chemistry and sedimentary characteristics, show that the apron is compositionally different from the basal ice. Our observations show that aprons may become deformed and partially entrained by advancing glaciers. However, such an ice marginal process does not provide a satisfactory explanation for the origin of basal ice observed at the ice margin. Our interpretation of the origin of basal ice is that it is formed by subglacial processes, which are likely to include deformation and entrainment of subglacial permafrost.
Current systems in the Jovian magnetosphere
Authors: Moriguchi Tadanori , Nakamizo Aoi , Tanaka Takashi , Obara Takahiro , Shimazu Hironori
Published: May 2008

The plasma dynamics in the Jovian magnetosphere is characterized by rapid rotation of the planet. In this paper, a new magnetohydrodynamic (MHD) simulation scheme is developed to precisely calculate the current systems in the Jovian magnetosphere and to relate them with the plasma dynamics. A field‐aligned current (FAC) pattern that is expected for the ionosphere to drive the corotation is reproduced in the present simulation result with current away from the ionosphere at lower latitudes and current toward the ionosphere at higher latitudes. In the magnetospheric region, a thin equatorial current sheet with eastward current flowing around Jupiter (ring current) dominates in the middle magnetosphere. By tracing current lines, it is found that the upward FAC on the low‐latitude side in the ionosphere is first connected to the ring current and then to the Chapman‐Ferraro current through the plasma sheet current. Downward FAC in the high‐latitude ionosphere is spirally connected to the tail lobe. From the distribution of J·E, the places of dynamo and energy consumption region are investigated to understand the energy balance associated with the corotation by magnetosphere‐ionosphere (M‐I) current system. From these analyses, the FAC, ring current, the Chapman‐Ferraro current and plasma distribution in the Jovian magnetosphere are understood as a self‐consistently organized structure through corotation and confinement. In addition, some interesting field‐line structures and plasmoid formation are found by tracing the magnetic field line.
Relating permeability to the structural setting of a fault‐controlled hydrothermal system in southeast Oregon, USA
Authors: Anderson Todd R. , Fairley Jerry P.
Published: May 2008

It is generally accepted that high‐permeability pathways are required to bring hydrothermal fluids to the surface from depth at elevated temperatures, and these pathways are commonly associated with faulting. The orientation and mode of fractures that develop as a result of fault slip are dependent on the state of stress and the geometry of the fault system, which in turn control the near‐fault permeability structure. We hypothesize that temperature data collected in fault‐controlled hydrothermal systems may be used to delineate the extent of the near‐surface breakdown region of the controlling fault, and may provide insight regarding the fault geometry and stress field. Here we present a geostatistical analysis of 1550 ground and spring temperature measurements in an area of active hydrothermal discharge located at Mickey Hot Springs in southeast Oregon. Indicator kriging was used to treat heterogeneity across the site prior to in‐category simulation of temperature as a continuous variable. The analysis indicates that zones of high, medium, and low temperature at the site arise from different physical mechanisms, which we propose are related to the underlying modes of fracturing and the dominant mechanisms of heat and mass transport (i.e., by advection or diffusion). The findings of this study suggest that thermal‐hydrologic data of the type presented here may be useful for understanding fault zone characteristics, and for developing conceptual models of fault‐controlled fluid flow.
Propagation and reflection of gravity waves in a meridionally sheared wind field
Authors: Huang Kai Ming , Zhang Shao Dong , Yi Fan
Published: May 2008

Although the properties of gravity waves propagating in a vertically sheared flow have been extensively studied, the effects of a horizontally sheared wind on gravity wave propagations were seldom reported. In this paper, according to the linear theory, the characteristics of gravity wave reflection in a meridionally sheared zonal background wind field are discussed, which are evidently different from those of wave reflected by a vertically sheared flow. By numerical simulations, we present the whole process of a gravity wave packet reflection in a meridionally sheared wind. When the wave reaches the reflecting level, the zonal disturbance velocity in the evanescent region shows an evanescent wave configuration, which is consistent with the Airy function form predicted by the linear theory; while the meridional disturbance velocity exhibits rather different wave structures. The wave number spectra of zonal and meridional disturbance velocities also show different characteristics in the reflection process. The energy center of the wave packet is reflected in a position nearer than the reflecting level predicted by the linear theory. While the wave propagates along (against) the meridionally sheared wind, the meridional perturbation kinetic energy and total wave energy decrease (increase), whereas, the zonal perturbation kinetic energy increases (decreases); and an energy exchange between the wave potential and wave kinetic energies can be observed. Earth rotation has a slight influence on the energy transfer between the wave and the background flow. If the wind shear beyond the reflecting level isn't strong enough, part components of the incident wave may steadily penetrate across the reflecting level, and yields a transmission wave. A large amplitude gravity wave propagating in a meridionally sheared wind can obviously induce a mean flow, which strengthens slightly the wave reflection, indicating that the transmission rate slightly decreases with the increasing amplitude of the incident wave. This differs from the reflection of waves in a vertical sheared wind field, in which the mean flow induced by the large amplitude wave significantly enhances the wave transmission effect. In the meridionally sheared flow, the transmission rate seems to mainly depend on the sheared wind and the parameters and spectral components of the incident waves.
On associations between the 11‐year solar cycle and the Indian Summer Monsoon system
Authors: Claud Chantal , Duchiron Bertrand , Terray Pascal
Published: May 2008

In this observational study, the associations between the characteristics of the Indian Summer Monsoon (ISM) and the 11‐year solar cycle have been investigated using a statistical analysis. A rather complex picture, with considerable spatial variation, has been observed. The most striking features appear in August and to some extent in July, where for higher solar activity, precipitation is reduced over the equatorial Indian Ocean and increased over the western Pacific Ocean and to a lesser extent over part of the Indian subcontinent. In terms of mechanisms, it is suggested that these associations result from a combination of effects: on one side, an effect which maximizes in July–August with warmer temperatures in the lower stratosphere for maximum solar activity, and is consistent with a reduction of the convective activity in the equatorial region and an enhancement in off‐equatorial regions; on the other side, a modulation of the mean sea level pressure fields, with a more southerly position of the monsoon trough in June, and a northwestward shift of the Mascarene High in July–August consistent with a stronger monsoon circulation. High solar activity could also cool the February–March SST in the southern Indian Ocean, which weakens the subsequent monsoon. Observations over the period 1871–2001 confirm these associations. As a result of the reported mechanisms, the 11‐year solar cycle has poor skill for foreshadowing the ISM as a whole. However, the associations, occurring on the timescale of months, provide a new insight and would be of considerable interest for further modeling studies.
Interannual variability of evapotranspiration and energy exchange over an annual grassland in California
Authors: Ryu Youngryel , Baldocchi Dennis D. , Ma Siyan , Hehn Ted
Published: May 2008

We report on the interannual variability of evapotranspiration (E) and energy exchange of an annual grassland in the Mediterranean climate zone of California. They were measured directly with the eddy covariance technique over a 6‐year period that spanned between July 2001 and June 2007 and experienced a large range in precipitation (376 mm to 888 mm). Despite a two‐fold range in precipitation, annual E ranged much less, between 266 mm and 391 mm. We found that pronounced energy‐limited and water‐limited periods occurred within the same year. In the water‐limited period, monthly integrated E scaled negatively with solar radiation and was restrained by precipitation. In the energy‐limited period, on the other hand, the majority of E scaled positively with solar radiation (Rg) and was confined by potential E (Ep). E was most sensitive to the availability of soil moisture during the transition to the senescence period rather than onset of the greenness period, causing annual E to be strongly modulated by growing season length. Bulk surface conductance scaled consistently with Priestley‐Taylor α coefficient regardless of interannual and seasonal variability of precipitation, E, and solar radiation.
Mineralogical composition of sands in Meridiani Planum determined from Mars Exploration Rover data and comparison to orbital measurements
Authors: Rogers A. D. , Aharonson O.
Published: May 2008

Constraints on the mineralogical composition of low‐albedo, low‐sulfur sands at Meridiani Planum are determined from Mars Exploration Rover (MER) Opportunity Miniature Thermal Emission Spectrometer (Mini‐TES), Mössbauer, and Alpha Proton X–Ray Spectrometer measurements. Results of this work show that the sand is olivine basaltic in composition, with minor amounts of sulfate and a high‐silica phase (glass or secondary amorphous silica). Measurements from all three instruments indicate that pyroxene is twice as abundant as olivine, and that the pyroxene composition is dominated by the low‐calcium variety. The volume abundance of olivine is constrained to be 10–15%. Results from detailed analyses of MER data are used to ground truth the spectral emissivity and mineral abundances derived from orbit with Mars Global Surveyor TES data. TES‐derived mineral abundances are within 5% of those derived from MER data, which is generally within the statistical errors associated with TES‐derived phase abundances. The agreement lends support to global‐ and regional‐scale variations in mineralogical composition determined from TES data in previous studies. An alternative method of least squares minimization is used for modeling the TES and Mini‐TES data; the benefits of this method are demonstrated by comparison with conventional least squares techniques previously used by TES data users.
Regional partitioning for wildfire regime characterization
Authors: Fiorucci Paolo , Gaetani Francesco , Minciardi Riccardo
Published: May 2008

Wildfire regime characterization is an important issue for wildfire managers especially in densely populated areas where fires threaten communities and property. The ability to partition a region by articulating differences in timing, frequency, and intensity of the phenomena among different zones allows wildfire managers to allocate and position resources in order to minimize wildfire risk. Here we investigate “wildfire regimes” in areas where the ecoregions are difficult to identify because of their variability and human impact. Several studies have asserted that wildfire frequency‐area relationships follow a power law distribution. However, this power law distribution, or any heavy‐tailed distribution, may represent a set of wildfires over a certain region only because of the data aggregation process. We present an aggregation procedure for the selection of homogeneous zones for wildfire characterization and test the procedure using a case study in Liguria on the northwest coast of Italy. The results show that the estimation of the power law parameters provides significantly different results depending on the way the area is partitioned into its various components. These finds also show that it is possible to discriminate between different wildfire regimes characterizing different zones. The proposed procedure has significant implications for the identification of ecoregion variability, putting it in a more mathematical basis.
Isotopic composition (δ13C, δ18O) in wood and cellulose of Siberian larch trees for early Medieval and recent periods
Authors: Sidorova Olga V. , Siegwolf Rolf T. W. , Saurer Matthias , Naurzbaev Mukhtar M. , Vaganov Eugene A.
Published: May 2008

We related tree ring width (TRW) and isotopic composition (δ13C, δ18O) of wood and cellulose from four larch trees (Larixcajanderi Mayr.) to climate parameters. The material was sampled in northeastern Yakutia [70°N–148°E] for the recent (AD 1880–2004) and early Medieval (AD 900–1000) periods. During the recent period June, July, and August air temperatures were positively correlated with δ13C and δ18O of wood and cellulose, while July precipitation was negatively correlated. Furthermore, the vapor pressure deficit (VPD) of July and August was significantly correlated with δ13C of wood and cellulose, but VPD had almost no influence on δ18O. Comparative analyses between mean isotope values for the (AD 900–1000) and (AD 1880–2004) periods indicate similar ranges of climatic conditions, with the exception of the period AD 1950–2004. While isotopic ratios in cellulose are reliably related to climatic variables, during some periods those in whole wood showed even stronger relationships. Strong positive correlations between δ18O of cellulose and Greenland ice‐core (GISP2) data were detected for the beginning of the Medieval period (r = 0.86; p < 0.05), indicating the reliability of isotope signals in tree rings for large‐scale reconstructions.
A Southern Hemisphere footprint in American Midwest precipitation
Authors: Penland Cécile , Matrosova Ludmila
Published: May 2008

A non‐normal filter is used to isolate the El Niño signal in tropical south Atlantic sea surface temperatures (SSTs). In boreal fall, the resulting index is significantly anticorrelated with precipitation in the American Midwest two to three seasons later. The phenomenological reasons for the relationship are explored in this article.
California Current System response to late Holocene climate cooling in southern California
Authors: Fisler J. , Hendy I. L.
Published: May 2008

New Holocene high‐resolution planktonic foraminiferal assemblage data from Santa Barbara Basin, California documents variability in ocean circulation as the California Current System responded to millennial‐scale climate change during late Holocene climatic cooling. Climatic variability increased at 4 ka when a series of extreme cool events (notably at 2.2, 1.5 and 0.8 ka) associated with glacial advance in the Pacific Northwest punctuated the predominantly warm Holocene. Simultaneously high subtropical species abundance suggests increased interannual variability (El Niño frequency/severity) or greater seasonality during the late Holocene. Planktonic foraminiferal assemblages indicate that the magnitudes of climatic shifts were greatest after 1.5 ka during an interval of extreme terrestrial hydrological variability in western North America and that the coolest interval of the Holocene in Santa Barbara Basin was coincident with the Little Ice Age.
Adsorption of water molecules inside a Au nanotube: A molecular dynamics study
Authors: Weng Meng-Hsiung , Lee Wen-Jay , Ju Shin-Pon , Chao Chien-Hsiang , Hsieh Nan-Kai , Chang Jee-Gong , Chen Hui-Lung
Published: May 2008

A molecular dynamics simulation of water molecules through a Au nanotube with a diameter of 20Å at bulk densities 0.8, 1, and 1.2g∕cm3 has been carried out. The water molecules inside a nanoscale tube, unlike those inside a bulk tube, have a confined effect. The interaction energy of the Au nanotube wall has a direct influence on the distribution of water molecules inside the Au tube in that the adsorption of the water molecules creates shell-like formations of water. Moreover, the high number of adsorbed molecules has already achieved saturation at the wall of the Au nanotube at three bulk densities. This work compares the distribution percentage profiles of hydrogen bonds for different regions inside the tube. The structural characteristics of water molecules inside the tube have also been studied. The results reveal that the numbers of hydrogen bonds per water molecule influence the orientational order parameter q. In addition, the phenomenon of a group of molecules bonded inside the tube can be observed as the number of hydrogen bonds increase.
Effect of flexibility on surface tension and coexisting densities of water
Authors: López-Lemus Jorge , Chapela Gustavo A. , Alejandre José
Published: May 2008

Molecular dynamics simulations of pure water at the liquid-vapor interface are performed using direct simulation of interfaces in a liquid slab geometry. The effect of intramolecular flexibility on coexisting densities and surface tension is analyzed. The dipole moment profile across the liquid-vapor interface shows different values for the liquid and vapor phases. The flexible model is a polarizable model. This effect is minor for liquid densities and is large for surface tension. The liquid densities increase from 2% at 300K to 9% at 550K when the force field is changed from a fully rigid simple point charge extended (SPCE) model to that of a fully flexible model with the same intermolecular interaction parameters. The increases in surface tension at both temperatures are around 11% and 36%, respectively. The calculated properties of the flexible models are closer to the experimental data than those of the rigid SPCE. The effect of the maximum number of reciprocal vectors (hzmax) and the surface area on the calculated properties at 300K is also analyzed. The coexiting densities are not sensitive to those variables. The surface tension fluctuates with hzmax with an amplitude larger than 10mNm−1. The effect of using small interfacial areas is slightly larger than the error in the simulations.
On models of certain p,q-algebra representations: The p,q-oscillator algebra
Authors: Sahai Vivek , Yadav Sarasvati
Published: May 2008

We construct one and two variable models of the p,q-oscillator algebra in terms of ladder operators. By using two p,q-analogs of the exponential function mapping, we show that matrix elements of these operators can be represented in terms of p,q-special functions. Further, we exhibit that these matrix elements satisfy certain biorthogonality relations.
Adsorption and electron-induced polymerization of methyl methacrylate on Ru(101¯)
Authors: Hedhili M. N. , Yakshinskiy B. V. , Wasielewski R. , Ciszewski A. , Madey T. E.
Published: May 2008

The adsorption and electron irradiation of methyl methacrylate (MMA) on a Ru(101¯0) surface have been studied using x-ray photoelectron spectroscopy (XPS), temperature programmed desorption (TPD), and low energy ion scattering. TPD analysis indicates that a monolayer of MMA chemisorbs and dissociates on the Ru(101¯0) surface. The reaction products observed upon heating include H2, CO, CO2, and a small amount of MMA. Physisorbed multilayers of MMA desorb at temperatures around 170K. Electron irradiation of physisorbed MMA at 140K leads to a modification of the MMA film: The XPS spectra show an increase in thermal stability of the film with retention of the MMA structure, and indicate that electron irradiation induces polymerization. An increase in the electron bombardment fluence induces a degradation of the formed polymerized species and leads to the accumulation of carbon on the Ru surface. These results are relevant to the accumulation of carbon on surfaces of Ru films that serve as capping layers on Mo∕Si multilayer mirrors used in extreme ultraviolet lithography.
Excited states and photodissociation of hydroxymethyl hydroperoxide
Authors: Eisfeld Wolfgang , Francisco Joseph S.
Published: May 2008

The structure of hydroxymethyl hydroperoxide (HOCH2OOH) (HMHP) has been examined using coupled cluster and multireference configuration interaction methods to study the excited states and probable photodissociation products. The results are compared to experiments. The vertical excitation energies for several excited states of HOCH2OOH are presented as well as the excited state energies along the O–O, O–H, C–O, and C–H dissociation pathways. The results help in the interpretation of experimental UV absorption spectra and elucidate the photodissociation mechanism of HMHP under tropospheric conditions.
Reversible folding simulation by hybrid Hamiltonian replica exchange
Authors: Xu Weixin , Lai Tingfeng , Yang Ye , Mu Yuguang
Published: May 2008

Reversible foldings of a β-hairpin peptide, chignolin, by recently invented hybrid Hamiltonian replica exchange molecular dynamics simulations based on Poisson–Boltzmann model in explicit water are demonstrated. Initiated from extended structures the peptide folded and unfolded a couple of times in seven out of eight replica trajectories during 100 nanoseconds simulation. The folded states have the lowest all-atom root mean squared deviation of 1.3Å with respect to the NMR structures. At T=300K the occurrence of folded states was converged to 62% during 80ns simulation which agrees well with experimental data. Especially, a detailed structural evolution map was constructed based on 800 000 structural snapshots and from where a unique folding doorway emerges. Compared with 130ns standard replica exchange simulation using 24 replicas on the same system, the hybrid Hamiltonian replica exchange molecular dynamics simulation presents consistent results.
Magnetic fluid labyrinthine instability in Hele-Shaw cell with time dependent gap
Authors: Tatulchenkov A. , Cebers A.
Published: May 2008

The free surface instability of a magnetic fluid in the Hele-Shaw cell with a time dependent gap is theoretically and numerically studied. The numerical algorithm is based on the boundary integral equation technique previously developed. Numerical results illustrate the role of magnetic forces in the instability—they diminish the selected wavelength of the interface perturbations, lead to more pronounced tip splitting events, and select the mode by which the droplet restores the circular shape at large thickness of the gap, when the role of the capillary forces is larger.
Construction of a low-temperature thermodynamic measurement system for single crystal of molecular compounds under pressures
Authors: Kubota Osamu , Nakazawa Yasuhiro
Published: May 2008

An apparatus to obtain low-temperature thermodynamic information under high pressures for a tiny single crystal of molecular compounds was developed based on the ac technique. To detect small temperature oscillation of a sample inside the cramp-type pressure cell, we have used a small ruthenium oxide chip sensor as a thermometer. The adoption of the four-terminal method by the ac resistance bridge has made high-resolution detection of thermal anomaly possible in the low-temperature region. The constructed high-pressure thermodynamic system was mounted on a He3 refrigerator and we have succeeded to detect the thermal anomaly in relevant to magnetic order of single crystal sample of Mn4-cluster complex up to 1.05GPa. A distinct peak of the heat capacity and its upward shift with increasing pressures was observed using a tiny crystal of about 100μg. The high-pressure behavior of the discontinuity of heat capacity at the superconductive transition of 6mg of metal indium has also been detected by this apparatus. The details and performance of the technique are reported.
A high voltage programmable ramp generator
Authors: Upadhyay J. , Joshi M. J. , Deshpande P. P. , Sharma M. L. , Navathe C. P.
Published: May 2008

In this paper, a ramp generator with programmable slope is presented. It consists of a high voltage step generator, followed by integrator. The capacitor and inductor in the integrator are designed such that they can be varied by a microcontroller. This circuit generates two bipolar ramps with fastest speed <1ns and provides continuous speed variation from 6to30ns for a ramp of 500V. This is being developed as a part of automated streak camera for deflection of electron beam.
Residual currents detected with a correcting electrode in a modified Bayard–Alpert hot-cathode-ionization gauge
Authors: Saeki Hiroshi , Magome Tamotsu
Published: May 2008

A nude-type hot-cathode-ionization-gauge head with correcting electrode and shield tube, succeeded in reducing practical pressure-measurement errors caused by an influx of photoelectrons in a synchrotron radiation environment. In the development of this modified Bayard–Alpert hot-cathode-ionization gauge, experimental results showed that a basic ion current generated around the correcting electrode by emission from the gauge filament, was proportional to an emission current (less than 10% of the normal emission current) detected with a grid of correcting electrode, and that differences between estimated and measured basic ion currents in a pressure range of higher than 10−8Pa order meant pressure-independent residual currents detected with the correcting electrode. By using calculated forward x-ray currents, these results also showed that the estimated residual currents with the correcting electrode were mainly caused by x rays from the grid of the hot-cathode-ionization-gauge head and the grid of correcting electrode, and that the x-ray currents with the correcting electrode only caused by x rays from the grid of the hot-cathode-ionization-gauge head were about 11% of the nominal x-ray current of the ionization-gauge head. Furthermore, they may suggest that an expected residual current with the collector can be calculated by using the estimated residual current with the correcting electrode, and that this ionization gauge has an additional function to reduce pressure-measurement errors caused by residual currents, though it is necessary to test the ionization gauge in an extremely high-vacuum environment under the x-ray limit of the gauge.
Electronic structure and optical gain of wurtzite ZnO nanowires
Authors: Zhang Xiu-Wen , Li Jingbo , Li Shu-Shen , Xia Jian-Bai
Published: May 2008

The electronic structure and optical gain of wurtzite ZnO nanowires are investigated in the framework of effective-mass envelope-function theory. We found that as the elliptical aspect ratio e increases to be larger than a critical value, the hole ground states may change from optically dark to optically bright. The optical gain of ZnO nanowires increases as the hole density increases. For elliptical wire with large e, the y-polarized mode gain can be several thousand cm−1, while the x-polarized mode gain may be 26 times smaller than the former, so they can be used as ultraviolet linearly polarized lasers.
Effects of spatial coherence distortion on terahertz time-domain spectroscopy
Authors: Théberge Francis , Châteauneuf Marc , Dubois Jacques
Published: May 2008

This letter reports the impacts of the spatial coherence distortion on the measured absorption spectra and the identification of materials analyzed by terahertz time-domain spectroscopy. It is shown that the deformation of the terahertz beam wave front can result into the overestimation of the electromagnetic absorption and even to the generation of artificial absorption peaks. Obtaining clear absorption spectra without artifacts is crucial for applications based on terahertz spectroscopy. A simple model is presented in order to predict the outcome spectrum from a terahertz beam distorted by a nonuniform sample analyzed through terahertz time-domain spectroscopy.
Low thermal conductivity and high thermoelectric figure of merit in n-type BaxYbyCo4Sb12 double-filled skutterudites
Authors: Shi X. , Kong H. , Li C.-P. , Uher C. , Yang J. , Salvador J. R. , Wang H. , Chen L. , Zhang W.
Published: May 2008

Filled skutterudites are one of the most promising thermoelectric materials for power generation applications. The choice and concentration of filler atoms are key aspects for achieving high thermoelectric figure of merit values. We report on the high temperature thermoelectric properties in the double-filled skutterudites BaxYbyCo4Sb12. The combination of Ba and Yb fillers inside the voids of the skutterudite structure provides a broad range of resonant phonon scattering and consequently a strong suppression in the lattice thermal conductivity is observed. A dimensionless thermoelectric figure of merit of 1.36 at 800K is achievable for n-type BaxYbyCo4Sb12.
Anomalous photocurrent in self-assembled InAs∕GaAs quantum dots
Authors: Monte A. F. G. , Qu Fanyao , Hopkinson M.
Published: May 2008

Carrier dynamics in self-assembled InAs∕GaAs quantum dots (QDs) is studied by photoluminescence (PL) and its complementary photocurrent (PC) spectroscopy. We found that carrier capture from the GaAs barriers, radiative recombination in InAs quantum dots, and tunneling among vertical QDs are very sensitive to applied bias voltage. An unusual behavior, by which the PL intensity presents steplike bias voltage dependence, has been observed. It is also consistently manifested in bias voltage dependent PC signals. We attribute this anomalous behavior to the interplay between the coupling of lateral QDs and tunneling among vertical ones.
Contrasting patterns of genetic structure and disequilibrium in populations of a stone-cased caddisfly (Tasimiidae) from northern and southern Australia
Authors: Schultheis Alicia Slater , Marchant Richard , Hughes Jane Margaret
Published: May 2008

In marine and freshwater invertebrate populations, microscale genetic differentiation or ‘genetic patchiness’ is thought to result from variation in the abundance and genetic composition of new recruits at a particular location. In the present study, the role of the adult emergence patterns in genetic patchiness was examined using mtDNA and two microsatellite loci to compare patterns of genetic differentiation in asynchronously (subtropical) and synchronously emerging (temperate) populations of the stone-cased caddisfly Tasimia palpata. A 550 base pair region of the mitochondrial cytochrome c oxidase subunit I gene (COI) was sequenced in at least 14 individuals from each population. Genetic structure was detected only at the reach scale in the subtropical populations and no genetic differentiation was detected in temperate populations. There were more deviations from Hardy–Weinberg equilibrium (HWE) in subtropical populations than in temperate populations where 44% and 12.5%, respectively, of tests for deviations from HWE were significant. Although distinct patterns of genetic structure and deviations from HWE were observed in the subtropical and temperate populations of T. palpata, no conclusive evidence was found to suggest that the differences are caused by differences in emergence patterns. We hypothesise that genetic patchiness must be caused by post-recruitment processes, most likely the preservation of oviposition ‘hotspots’ in subtropical streams.
Survival and behaviour of juvenile red rock lobster, Jasus edwardsii, on rocky reefs with varying predation pressure and habitat complexity
Authors: Mislan K. A. S. , Babcock Russ C.
Published: May 2008

The role of large predatory fish in coastal communities is generally unknown because of overfishing. In order to understand the direct and indirect impacts of these increased population sizes on coastal food chains, the effect of areas with more fish predators on the survival and behaviour of potential prey was assessed. Juvenile lobsters, Jasus edwardsii (10–20 mm carapace length), were tethered on rocky reefs inside and outside marine reserves in northeastern New Zealand to assess survival under differing predator densities. Since rocky reef habitats in northeastern New Zealand include zones of kelp forest and barren reef, a two-way factorial design was used to determine the effects of predators, habitat, and the interaction of these two factors on juvenile lobster survival. Overall, the results indicated that neither varying large fish density nor varying kelp density had direct impacts on the survival rate of juvenile lobsters. Laboratory manipulations demonstrated behavioural changes by juvenile lobsters such that when a large predatory fish was present, juvenile lobsters spent significantly less time moving, even when separated from the predator by a porous barrier. Thus areas with more fish predators may increase juvenile lobster survival but potentially at the cost of reduced feeding opportunities.