bluuebunny/crossref_metadata_2025 huggingface dataset:
Chronic Viral Hepatitis and Hepatocellular Carcinoma
Authors: Barazani Yagil , Hiatt Jonathan R. , Tong Myron J. , Busuttil Ronald W.
Published: April 2007

Background

Hepatocellular carcinoma (HCC) is the third leading cause of death from malignancy worldwide, and its increasing incidence parallels rising global rates of hepatitis B (HBV) and hepatitis C (HCV).

Methods

This retrospective review was undertaken to identify differences in the epidemiology and tumor characteristics of 255 patients with HCC due to chronic HBV (n = 105) or HCV (n = 150).

Results

Hepatitis B patients were predominantly Asian (84%), whereas HCV patients were predominantly Caucasian (72%; p < 0.0001). Hepatitis B patients exhibited stronger family histories of liver disease (54%) and HCC (33%), whereas HCV risk factors included blood transfusion (56%), intravenous drug abuse (31%), and alcohol consumption (44%; p < 0.0001 for all comparisons). Pretreatment laboratory values showed lower albumin and platelet levels but higher bilirubin and AST levels in HCV versus HBV patients (p < 0.0001 to 0.01). As cirrhosis was present in nearly all HCV patients, but only in 79% of HBV patients, HCV patients had more stigmata of portal hypertension, including ascites (65%), varices (86%), splenomegaly (77%), and encephalopathy (41%; p < 0.0002 for all comparisons). Although tumors in HBV patients were larger (7.3 cm versus 5.1 cm; p = 0.0001) and more frequently bilobar, the tumor grade, number of tumors, and metastases were similar for both groups. Hepatitis C patients received less treatment, including chemoembolization and surgical resection. The 5‐year survival was higher in HBV patients compared to HCV patients (56% versus 36%, p = 0.046).

Conclusions

Patients with HBV‐ and HCV‐related HCC have different epidemiologic, clinical, and survival characteristics. More HCV patients presented with advanced cirrhosis, received less aggressive treatment, and experienced lower 5‐year survival.
Attenuation of Kupffer Cell Function in Acute on Chronic Liver Injury Enhanced Engraftment of Transplanted Hepatocytes
Authors: Yuan Ray‐Hwang , Chen Hui‐Ling , Chen Huey‐Ling , Hsu Ming‐Kung , Lee Po‐Huang , Chang Mei‐Hwei
Published: April 2007

Background

The present study was designed to elucidate the relationship of engraftment efficiency of transplanted cells and Kupffer cell function in mice with acute on chronic liver injury and acute liver injury.

Methods

The recipient dipeptidyl peptidase IV knockout (DPPIV–/–) mice were divided into two groups: (1) the acute on chronic liver injury group (CCl4/APAP group) that received CCl4 (1 ml/kg) twice a week for 4 weeks following one dose of acetaminophen (APAP), 600 mg/kg; (2) the acute liver injury group (APAP‐only group) that received a single dose of APAP at 600 mg/kg. DPPIV+/+ hepatocytes were transplanted 24 h after APAP intoxication. Engraftment efficiency was evaluated at day 7 and day 14 after transplantation. The tumor necrosis factor‐α (TNF‐α) mRNA expression level of Kupffer cells immediately before cell transplantation was compared between the two groups before and after lipopolysaccharide (LPS, 100 ng/ml) stimulation.

Results

The number of transplanted cells and clusters in each 100× microscopic field were higher in the CCl4/APAP group at both day 7 (21.5 ± 6.3 versus 8.3 ± 4.0, p < 0.001; 14.9 ± 4.6 versus 6.6 ± 3.4, p < 0.001, respectively) and day 14 (17.3 ± 4.4 versus 10.2 ± 3.3, p = 0.001; 12.6 ± 3.2 versus 7.9 ± 1.6, p = 0.004, respectively). After LPS stimulation, the expression level of TNF‐α was lower (175.7 ± 54.6 versus 465.6 ± 64.2, p = 0.002), and the increment of TNF‐α expression was also less significant in the CCl4/APAP group (1.5‐fold versus 6.5‐fold, p = 0.014).

Conclusions

Chronic liver injury desensitized Kupffer cells and reduced TNF‐α expression, two results that correlated with the increased engraftment of transplanted cells.
Sustainable use of tropical forests by reduced‐impact logging in Deramakot Forest Reserve, Sabah, Malaysia
Authors: Lagan Peter , Mannan Sam , Matsubayashi Hisashi
Published: April 2007

In pursuance of economic growth and development, logging has exhausted the natural timber resource in the tropical rainforest of Sabah, Malaysia. Realizing the forest depletion, the Sabah Forestry Department, with technical support from the German Agency for Technical Cooperation, begun developing a management system with the intent of managing all commercial forest reserves in a way that mimics natural processes for sustainable production of low volume, high quality, and high priced timber products in 1989. As dictated by a forest management plan based on forest zoning, about 51,000 ha of the entire area is set aside for log production and 4,000 ha for conservation in Deramakot Forest Reserve, Sabah, Malaysia. This Forest Management Plan has served as the blueprint for operational work and biodiversity conservation in Deramakot to the present. A strict protection area is set aside for biodiversity conservation within the reserve. A reduced‐impact logging system is being employed for harvesting with minimal impacts on the physical environment. Deramakot Forest Reserve was certified as “well managed” by an international certification body, the Forest Stewardship Council, in 1997 and is the first natural forest reserve in Southeast Asia managed in accordance with sustainable forestry principles. In addition to providing a “green premium,” certification provides easier market access, evidence of legality, multi‐stakeholder participation, conservation of biodiversity and best forest management practices, particularly reduced‐impact logging techniques. Deramakot Forest Reserve is the flagship of the Sabah Forestry Department and serves as a symbol of what can be achieved with political support and institutional commitment.
Functional spatial scale of community composition change in response to windthrow disturbance in a deciduous temperate forest
Authors: Hirao Toshihide , Murakami Masashi , Oguma Hiroyuki
Published: April 2007

Community dynamics in local habitats are affected by landscape characteristics such as the area and connectivity of surrounding habitats at a functional spatial scale where the community responds to landscape structure. However, the functional spatial scale at which community composition is affected by landscape structure has never been explored. We assessed the functional spatial scales of composition change in birds and in three types of arthropod communities (canopy, forest‐floor and flying ones) with regard to landscape heterogeneity resulting from a large typhoon in a temperate forest of Japan. We examined the effects of tree‐fall disturbance on the communities at various spatial scales, with special attention to compositional evenness. The spatial scale of the best‐fitting model, which was selected from models fitted to the disturbance area at stepwise spatial scales, was interpreted as the community‐specific functional spatial scale. The composition of all communities studied was all significantly dependent on gap area. The functional spatial scale was highest in birds (370 m in radius), intermediate in flying arthropods (90 m) and lowest in canopy and forest‐floor arthropods (10 m). This result may reflect typical dispersal ability and the spatial range of resource use in the community. Compositional changes in each community were consistent with theory regarding traits and responses of component taxa, although the enhancement of evenness was observed only in the arthropod communities. These results imply that management and reserve selection based on functional spatial scales can be effective in the conservation of biodiversity and ecosystem services at the community level.
Effects of forest‐pasture edge on C, N and P associated with Caesalpinia eriostachys, a dominant tree species in a tropical deciduous forest in Mexico
Authors: Toledo‐Aceves Tarin , García‐Oliva Felipe
Published: April 2007

Forest fragmentation in tropical ecosystems can alter nutrient cycling in diverse ways. We have analysed the effects of the forest‐pasture edge on nutrient soil dynamics in a tropical deciduous forest (TDF) in Mexico. In two remnant forest fragments, both larger than 10 ha, litterfall, litter and soil samples associated to the tree Caesalpinia eriostachys were collected at five distances from the pasture edge into the inner forest (10 m in the pasture and 0–10, 30–40, 70–80 and 100–110 m towards the forest interior). We measured the concentrations of carbon (C), nitrogen (N) and phosphorus (P) in litterfall, surface litter and soil, and soil microbial C (Cmic) and microbial N (Nmic). Soil nutrient concentrations and Cmic and Nmic were lower in the pasture soils than in the forest soil samples. Total C and N pools, and Cmic and Nmic in the pasture were lower than in the forest. In contrast, net N immobilization and the increase in Nmic from rain to dry season increased from the edge to the inner forest. Soil P concentration was lower in the pasture and at the first distance class in the forest margin (0–10 m) than in the sites located further into the forest, while litter P concentration had the inverse pattern. Litterfall P was also reduced near the edge and increased towards the forest interior. As a consequence, litterfall C:P and N:P ratios decreased from the edge to the inner forest. These results suggest that the forest–pasture edge disrupts P dynamics within the first 10 m in the forest. Thus, plants' use of nutrients and productivity could be altered in the edge of fragmented forests.
Operative Findings in Reoperation of Patients with Cubital Tunnel Syndrome
Authors: Mackinnon Susan E. , Novak Christine B.
Published: April 2007

The purpose of this study was to report the operative findings in patients who underwent a secondary operation for cubital tunnel syndrome. A chart review was performed of 100 patients who had undergone a secondary operation for cubital tunnel syndrome by one surgeon. The mean age was 48 years (standard deviation 13.5 years). The most common complaint after primary surgery was increased symptoms in the ulnar nerve distribution ( n=55) and pain in the medial antebrachial cutaneous nerve distribution ( n=55). The most common operative findings included a medial antebrachial cutaneous nerve neuroma ( n=73) and a distal kink of the ulnar nerve ( n=57). This kink was noted as the nerve moved from its transposed position anterior to the medical epicondyle to its native position within the flexor carpi ulnaris. This study suggests that during primary surgery for cubital tunnel syndrome care should be given to avoid injury to the medial antebrachial cutaneous nerve, distal kinking of the ulnar nerve with transposition and pressure on the transposed nerve by the fascial flaps or tendinous bands.
Deposition of Free Cholesterol in the Blood Vessels of Patients with Coronary Artery Disease: a Possible Novel Mechanism for Atherogenesis
Authors: Couto Ricardo D. , Dallan Luís A. O. , Lisboa Luiz A. F. , Mesquita Carlos H. , Vinagre Carmen G. C. , Maranhão Raul C.
Published: April 2007

A cholesterol‐rich nanoemulsion (LDE) that mimics the composition of low‐density lipoprotein (LDL) acquires apoE in the plasma and is taken‐up by the cells by LDL receptors. In this study, to verify whether free cholesterol (FC) and the cholesteryl ester (CE) components of LDL are taken‐up differently by the vessels. LDE labeled with 3H‐cholesterol and 14C‐cholesteryl oleate was injected into 20 coronary artery disease patients 24 h before a scheduled myocardial coronary artery bypass grafting. The plasma kinetics of both radiolabels was determined from plasma samples collected over 24 h, and fragments of vessels discarded during surgery were collected and analyzed for radioactivity. LDE FC was removed faster than CE. The radioactive counting of LDE CE was greater than that of LDE FC in the blood, but the uptake of FC was markedly greater than that of CE in all fragments: fivefold greater in the aorta (p = 0.04), fourfold greater in the internal thoracic artery (p = 0.03), tenfold greater in the saphenous vein (p = 0.01) and threefold in the radial artery (p = 0.05). In conclusion, the greater removal from plasma of FC compared with CE and the remarkably greater vessel tissue uptake of FC compared with CE suggests that, in the plasma, FC dissociates from the nanoemulsion particles and precipitates in the vessels. Considering LDE as an artificial nanoemulsion model for LDL, our results suggest that dissociation of FC from lipoprotein particles and deposition in the vessel wall may play a role as an independent mechanism in atherogenesis.
Macadamia Nut Consumption Modulates Favourably Risk Factors for Coronary Artery Disease in Hypercholesterolemic Subjects
Authors: Garg Manohar L. , Blake Robert J. , Wills Ron B. H. , Clayton Edward H.
Published: April 2007

Macadamia nuts are rich source of monounsaturated fats (oleic and palmitoleic acids) and contain polyphenol compounds, therefore, their consumption can be expected to impart health benefits to humans. This study was conducted to examine the effects of consuming macadamia nuts in hypercholesterolemic male individuals on plasma biomarkers of oxidative stress, coagulation and inflammation. Seventeen hypercholesterolemic male subjects were given macadamia nuts (40–90 g/day), equivalent to 15% energy intake, for a period of 4 weeks. As expected, monounsaturated fatty acids (16:1n‐7, 18:1n‐9 and 20:1n‐9) were elevated in the plasma lipids of all volunteers following intervention with macadamia nuts. Plasma markers of inflammation (leukotriene, LTB4) and oxidative stress (8‐isoprostane) were significantly lower (1,353 ± 225 vs. 1,030 ± 129 pg/mL and 876 ± 97 vs. 679 ± 116 pg/mL, respectively) within 4 weeks following macadamia nut intervention. There was a non‐significant (23.6%) reduction in the plasma TXB2/PGI2 ratio following macadamia nut consumption. This study demonstrates, for the first time, that short‐term macadamia nut consumption modifies favourably the biomarkers of oxidative stress, thrombosis and inflammation, the risk factors for coronary artery disease, despite an increase in dietary fat intake. These data, combined with our previous results on cholesterol‐lowering effects of macadamia nuts, suggest that regular consumption of macadamia nuts may play a role in the prevention of coronary artery disease.
Plasma Lipoproteins and Triacylglycerol are Predictors of Small, Dense LDL Particles
Authors: Tsimihodimos Vasilis , Gazi Irene , Kostara Christina , Tselepis Alexandros D. , Elisaf Moses
Published: April 2007

Recently published data suggest that the assessment of LDL subfraction profiles may contribute to the determination of the cardiovascular risk. In this study, we tested the ability of various metabolic parameters to estimate the presence or the preponderance of small, dense LDL particles (sdLDL). One hundred and fifty individuals attending the Outpatient Clinics of the University Hospital of Ioannina for suspected metabolic abnormalities were included in the study. Individuals were excluded if they were found to be diabetic or if they had a history of cardiovascular disease. Patients with thyroid dysfunction, liver or kidney diseases as well as those receiving drugs that may interfere with lipids or glucose metabolism were also excluded from the study. The ability of the various parameters to identify individuals with pattern B LDL phenotype or, alternatively, with measurable quantities of sdLDL particles was tested with the calculation of the areas under the ROC curves. The ratio of triglycerides to HDL‐C was the best predictor of the presence of the pattern B LDL phenotype. Nevertheless, when the variable of interest was the presence of measurable quantities of sdLDL subfractions, the ratio of apoB to apoAI had the best predictive ability. In conclusion the ratios of apoB to apoAI and of triglycerides to HDL‐C can reliably predict the presence of measurable quantities of sdLDL particles and of the pattern B LDL phenotype, respectively. However, since the quantitative determination of sdLDL concentrations may contribute to the determination of the cardiovascular risk, whereas the role of the LDL particle size remains controversial, apoB to apoAI ratio could provide more valuable information compared to markers that simply predict the presence of the pattern B LDL phenotype.
The role of small RNAs in abiotic stress
Authors: Phillips Jonathan R. , Dalmay Tamas , Bartels Dorothea
Published: April 2007

It was recently discovered that plants respond to environmental stress not only with a specific gene expression programme at the mRNA and protein level but also small RNAs as response modulators play an important role. The small RNAs lead to cleavage or translational inhibition of mRNAs via complementary target sites. Different examples are described where small RNAs have been shown to be involved in stress responses. A link between hormonal action and small RNA activities has frequently been observed thus coupling exogenous factors with endogenous transmitters. Using the CDT‐1 gene from the desiccation tolerant plant Craterostigma plantagineum as an example, it is discussed that generation of novel small RNAs could be an evolutionary pathway in plants to adapt to extreme environments.
Some specific features of genesis of microdiamonds of octahedral and cubic habit from kimberlites of the Udachnaya pipe (Yakutia) inferred from carbon isotopes and main impurity defects
Authors: Reutsky V.N. , Zedgenizov D.A.
Published: April 2007

Microdiamonds (crystals smaller than 1 mm) of octahedral and cubic habit from Udachnaya kimberlite pipe (Yakutia) have been compared in order to distinguish genetic features inferred from carbon isotopic composition and impurity defects. Microdiamonds of cubic habit from the Udachnaya kimberlite pipe have a fibrous internal structure and a high content of nitrogen impurity (400–3000 ppm). Octahedral microdiamonds from the same deposit are distinguished by a low nitrogen content of 0 to 500 ppm and zoning structure. The isotopic composition of carbon (δ13C is –4.7‰ for octahedra and –4.5‰ for cuboids) suggests a common source of carbon for these morphologic groups. The studied characteristics can be due to crystallization of octahedra from carbon dissolved in the melt, and cuboids, under the conditions of the hampered diffusion of carbon.
Geochemical evolution of Late Eocene-Oligocene magmatism in the Schmidt Peninsula (Northern Sakhalin)
Authors: Rasskazov S.V. , Simanenko V.P. , Malinovsky A.I. , Yasnygina T.A.
Published: April 2007

The Middle Cenozoic evolution of magmatism in the Schmidt Peninsula between 37 and 25 Ma began with eruptions of subalkaline and moderately alkaline andesite, latite, trachyandesite, and trachyrhyolite lavas and ended with subvolcanic intrusions of highly alkaline strongly undersaturated essexites. According to trace-element data, magmatism evolved from melting of a mantle source in the zone of ocean-continent plate convergence to small-degree partial melting in lithospheric mantle at the final stage. This succession is generally typical of Late Cenozoic continental-margin magmatism in southeastern Russia. The similarity in the Middle and Late Cenozoic stages of magmatism is evidence for their individual significance.
Women in Huang Zunxian's Riben zashi shi (Poems On Miscellaneous Subjects from Japan)
Authors: Lynn Richard John
Published: April 2007

Poems about women from the Riben zashi shi (Poems on Miscellaneous Subjects from Japan) by Huang Zunxian constitute about ten per cent of the collection as a whole; most are translated and annotated here. These poems and Huang's own attached commentaries create a fascinating mixture of fact, sensibility, and interest that attempts both to describe Japanese women in terms of variations on the traditional cultural roles and characteristics of Chinese women and to account for who they then were and how they behaved in terms of the general process of modernisation/westernisation, which then, during the early Meiji era, was transforming practically all aspects of Japanese life. As with other subjects, a strong sense of the tension between tradition and modernity underlies such poems, leaving the reader at times with a suspension of resolution between them and at others with the hope that the present could lead to a more hopeful future. In either case, the relationship between the sexes is examined with wit and insight, and the changes that this relationship were then undergoing are treated as an integral and inevitable dimension of the modernisation process.
Impact on the ocean of extreme Greenland Sea heat loss in the HadCM3 coupled ocean‐atmosphere model
Authors: Grist Jeremy P. , Josey Simon A. , Sinha Bablu
Published: April 2007

The ocean response to air‐sea flux variability in the Greenland Sea is investigated using a 1000 year run of the coupled ocean‐atmosphere model HadCM3. Evaluation of the density flux reveals that net heat flux anomalies have a greater impact on surface density changes than anomalies in both net evaporation and ice melt/formation. Averaged over the Greenland Sea, the annual mean density flux due to heat loss is 1.8 × 10−6 kg m−2 s−1, an order of magnitude greater than the net evaporation and the ice melt and formation terms, which are −0.1 and −0.2 × 10−6 kg m−2 s−1, respectively. Extreme winter heat loss events reach 250 W m−2 and are associated with reduced ice cover and anomalously strong northerly airflow over the Greenland Sea. They result in enhanced convection and modify the properties of deep water flowing south through the Denmark Strait. The deep water transport increases by about 30% when the strongest and weakest heat loss events are compared, and there is a corresponding reduction in temperature and salinity by up to 2.3°C and 0.38 psu. We also find significant correlations between deep western basin temperatures at 60°, 55°, and 49°N and the Greenland Sea heat flux anomalies which peak at lags of up to 4 years with the time delay increasing toward more southerly latitudes. Our results suggest that Greenland Sea heat flux variability is a key variable for understanding recent observations of significant interannual variability in Denmark Strait transport characteristics.
Laser beam propagation through inertial confinement fusion hohlraum plasmas
Authors: Froula D. H. , Divol L. , Meezan N. B. , Dixit S. , Neumayer P. , Moody J. D. , Pollock B. B. , Ross J. S. , Suter L. , Glenzer S. H.
Published: April 2007

A study of the laser-plasma interaction processes have been performed in plasmas that are created to emulate the plasma conditions in indirect drive inertial confinement fusion targets. The plasma emulator is produced in a gas-filled hohlraum; a blue 351-nm laser beam propagates along the axis of the hohlraum interacting with a high-temperature (Te=3.5keV), dense (ne=5×1020cm−3), long-scale length (L∼2mm) plasma. Experiments at these conditions have demonstrated that the interaction beam produces less than 1% total backscatter resulting in transmission greater than 90% for laser intensities less than I<2×1015Wcm−2. The bulk plasma conditions have been independently characterized using Thomson scattering where the peak electron temperatures are shown to scale with the hohlraum heater beam energy in the range from 2keV to 3.5keV. This feature has allowed us to determine the thresholds for both backscattering and filamentation instabilities; the former measured with absolutely calibrated full aperture backscatter and near backscatter diagnostics and the latter with a transmitted beam diagnostics. Comparing the experimental results with detailed gain calculations for the onset of significant laser scattering processes shows a stimulated Brillouin scattering threshold (R=10%) for a linear gain of 15; these high temperature, low density experiments produce plasma conditions comparable to those along the outer beams in ignition hohlraum designs. By increasing the gas fill density (ne=1021cm−3) in these targets, the inner beam ignition hohlraum conditions are accessed. In this case, stimulated Raman scattering dominates the backscattering processes and we show that scattering is small for gains less than 20 which can be achieved through proper choice of the laser beam intensity.
Insights into the algebraic structure of Lorenz-like systems using feedback circuit analysis and piecewise affine models
Authors: Letellier Christophe , Amaral Gleison F. V. , Aguirre Luis A.
Published: April 2007

The characterization of chaotic attractors has been a widely addressed problem and there are now many different techniques to define their nature in a rather accurate way, at least in the case of a three-dimensional system. Nevertheless, the link between the structure of the ordinary differential equations and the topology of their solutions is still missing and only a few necessary conditions on the algebraic structure are known today. By using a feedback circuit analysis, it is shown that it is possible to identify the relevant terms of the equations, that is, the terms that really contribute to the structure of the phase portrait. Such analysis also provides some guidelines for constructing piecewise affine models. Moreover, equivalence classes can be defined on the basis of the active feedback circuits involved.
High-temperature magnetic-field-induced activation of room-temperature ferromagnetism in Ce1−xNixO2
Authors: Thurber A. , Reddy K. M. , Punnoose A.
Published: April 2007

We report room-temperature ferromagnetism in nickel doped ceria (Ce1−xNixO2) powders prepared using the sol-gel process. Magnetometry studies on as-prepared samples reveal a weak ferromagnetic (FM) behavior in the range 0<x<0.04 (8.6×10−4μB∕Ni ion for 4%). For x>0.04, the FM magnetization steadily decreases for increased dopant concentration. The weak FM behavior of the samples improved dramatically after undergoing high-temperature (⩽500°C) activation in the presence of an external magnetic field (H⩽1T). The magnitude of the improvement, which was very reproducible, was strongest for 10% Ni doped CeO2 with saturation magnetization Ms increasing by 600 times. Curie temperatures of the activated samples varied in the 597–646K range depending on the Ni concentration and preparation conditions. X-ray diffraction studies did not reveal any noticeable structural changes as a result of the activation process.
Magnetic properties of aluminum-substituted R–T deuterides Ho6(Fe,Al)23Dz
Authors: Ostoréro J. , Guillot M.
Published: April 2007

The influence of deuteration on the magnetic properties of aluminum-substituted R6Fe23−xAlxDz compounds (R=Ho,Y; x=0,5; z=10,16) has been investigated by magnetization measurements in the temperature range of 5–350K under a magnetic field of up to 90kOe. In comparison to the parent alloys, a large increase of the Fe magnetic moment μFe, much larger in yttrium than in holmium compounds, is observed upon deuteration. The magnetic exchange coupling NHo–Fe between the R and Fe sublattices was estimated from the slope of the field-induced transitions of the magnetization M isotherms in the vicinity of the compensation temperature Tcomp. The values of NHo–Fe and Tcomp decrease with insertion of deuterium, indicating a weakening in R–T coupling. The different results are analyzed within the frame of the Néel ferrimagnetic model taking into account the noncolinearity of the Ho and Fe sublattices magnetizations. The Ho–Ho and Fe–Fe magnetic interactions and the canting angle θ(θ⪡10°) are then determined. In Al-substituted deuterides, the presence of the rare-earth Ho “stabilizes” the ferrimagnetism.
Nonlinear plasma response to a slowly varying electrostatic wave, and application to stimulated Raman scattering
Authors: Bénisti Didier , Gremillet Laurent
Published: April 2007

The nonlinear electronic susceptibility induced by an electrostatic wave slowly varying in space and time, which is the key parameter for the kinetic modeling of stimulated Raman scattering (SRS), is derived analytically. When calculating the real part of the susceptibility, by making the adiabatic approximation, account is taken of the amplitude dependence of the wave frequency. Then, the “loss of resonance” of a plasma wave is found to occur at much larger amplitudes than has been predicted by Rose and Russel [H. A. Rose and D. A. Russell, Phys. Plasmas 11, 4784 (2001)] using the constant-frequency approximation. The imaginary part of the susceptibility, from which is deduced the Landau damping rate of the plasma wave, is derived using two different approaches (perturbative or not) depending on the wave amplitude. It is shown to be a nonlocal function of the wave amplitude, which underlines the importance of interspeckle interactions in SRS.
Transient enhancement of thermocapillary flow in a two-dimensional cavity by a surfactant
Authors: Hanumanthu Ram , Stebe Kathleen J.
Published: April 2007

In this paper, we present results of a numerical study of the effect of insoluble surfactants on thermocapillary flow in a two-dimensional slot. For surfactant-laden systems, there are pronounced nonlinearities in the surface tension dependence on both temperature and surface concentration, some of which create interesting phenomena that cannot be captured by the linear limit used in prior work. Our work focuses on two regimes of nonlinear coupling between the surface tension, surface concentration, and surface temperature. First, we address a surfactant that forms a monolayer in a single surface phase. Second, we discuss a regime in which surfactants transiently enhance thermocapillary flow, rather than oppose it. This occurs for long chain surfactants with small headgroups that form liquid-expanded (LE) and liquid-condensed (LC) phases, e.g., (insoluble) long-chain carboxylic-acids under conditions where their headgroups are not disassociated. Results indicate that a surfactant in LE/LC coexistence initially enhances thermocapillary flow in a slot, creating a surface convective flux that rapidly convects surfactant toward the cold region and depletes the warm region. However, the convection of surfactant quickly drives the surface concentration out of LE/LC coexistence and into LE (in the depleted region) and LC (in the cold region). Thereafter, the rapid initial flow is again quenched by the usual circumstance of a surfactant in a single surface phase exerting an opposing Marangoni stress that stagnates the interface. At high surface Peclet numbers, no steady-state thermocapillary flow is sustained.
Device modeling of light-emitting ambipolar organic semiconductor field-effect transistors
Authors: Smith D. L. , Ruden P. P.
Published: April 2007

Recent experiments have demonstrated ambipolar channel conduction and light emission in conjugated polymer field-effect transistors (FETs). The devices have source∕drain contacts fabricated using metals with different work functions. Negative charge carriers are injected from a low work-function metal contact and positive charge carriers from a high work-function contact. In the ambipolar mode of operation, the gate potential lies between the potentials of the electron and hole injecting contacts, so that electrons dominate the channel conductance near the electron injecting contact and holes dominate channel conductance near the hole injecting contact. The injected charge carriers propagate along the FET channel and recombine in regions where both types of carriers are present. The location and intensity of maximum recombination and light emission is controlled by the voltages applied to the transistor terminals. In this paper a device model for ambipolar organic field-effect transistors based on the gradual channel approximation is presented. The model includes the effect of charge carrier trapping through density dependent mobilities. The resulting nonlinear differential equation for the channel potential is solved numerically. The results of the device model are in good agreement with the published experimental data.
Alfvén wave driven compressional fluctuations in shear flows
Authors: Kaghashvili Edisher Kh.
Published: April 2007

The nature of driven linear compressible fluctuations is studied when there is an Alfvén wave propagating in the medium characterized by an inhomogeneous velocity field. This Brief Communication is an extension of our recent study [E. Kh. Kaghashvili et al., Phys. Plasmas 13, 112107 (2006)] in which analytical solutions were presented revealing a nature of driven compressional waves accurately in a low β-plasma. Here, this assumption is removed and analytical solutions that accurately describe compressional waves in the general case are obtained. While the solutions of the driven waves in a long run follow the WKB description, the main goal here is to study an initiation and evolution of compressible disturbances at earlier times. The purpose of this Brief Communication is to derive the formal solutions for compressional fluctuations driven by the initial Alfénic spectrum.
Luminescence quenching by photoionization and electron transport in a LaAlO3:Ce3+ crystal
Authors: van der Kolk E. , de Haas J. T. M. , Bos A. J. J. , van Eijk C. W. E. , Dorenbos P.
Published: April 2007

A combined photoconductivity, absorption, and thermoluminescence study was performed to understand the absence of luminescence from Ce3+ in LaAlO3:Ce3+. It is demonstrated that the absence of luminescence is the result of Ce3+ ionization from the 5d excited states, which are all located in the conduction band. Ce3+ ionization is accompanied by the formation of several broad absorption and photoconductivity bands, which are assigned to electron traps. A time and temperature dependent optical investigation of these traps reveals the conditions under which electrons are transferred from Ce3+ to traps and vice versa, from traps back to Ce4+. The observed difference in energy needed to thermally or optically release electrons from traps is qualitatively explained in terms of the location of the ground and excited states of the electron traps with respect to the conduction band.
Analytical full-field solutions of a magnetoelectroelastic layered half-plane
Authors: Lee Jui-Mu , Ma Chien-Ching
Published: April 2007

This study presents Green’s functions for a transversely isotropic magnetoelectroelastic layered half-plane subjected to generalized concentrated forces and screw dislocations applied either to the layer or the half-plane. Explicit closed-form solutions of the full fields for the coupled problem are obtained using the Fourier-transform method and the series expansion technique. The complete solutions for this problem include only the simplest solutions obtained from an infinite magnetoelectroelastic medium with generalized concentrated forces and generalized screw dislocations. The solutions include Green’s function for applied loadings in an infinite medium and an infinite number of image singularities are induced to satisfy the boundary and interface conditions. It is shown that the physical meaning of the solution is the image method. The mathematical method used in this study provides an automatic determination for the locations and magnitudes of all image singularities. The closed-form solutions are functions of material properties, the thickness of the layer, the generalized concentrated forces, and screw dislocations. Numerical results for the full-field distributions of stresses, electrical displacements, magnetic inductions, strains, electric fields, and magnetic fields, in the layered half-plane medium are presented and discussed in detail.
Property characterization of AlN thin films in composite resonator structure
Authors: Chen Qingming , Qin Lifen , Wang Qing-Ming
Published: April 2007

AlN thin films with c-axis orientation have been investigated for fabricating thin film bulk acoustic wave resonators in the past few years. Characterization of thin film material properties including density, elastic modulus, and piezoelectric coefficient is essential in processing study and for predicting the performance of the acoustic devices. In this paper, we present our results on the fabrication of highly c-axis oriented AlN thin films on Pt∕Ti∕Si (100) substrates by dc reactive magnetron sputtering method. The crystalline structure and the surface morphology of AlN films are characterized by x-ray diffraction and scanning electron microscopy. The effective piezoelectric coefficient d33eff of the AlN films was measured by a laser interferometer method and the piezoelectric coefficient d33 was estimated. A recently developed resonance spectrum method is applied to characterize the electromechanical properties of AlN thin films based on the input electrical impedance equation derived by one-dimensional transmission line theory for composite resonators. Using the experimental impedance spectrum data, the density and elastic constant of the piezoelectric AlN thin film in the four-layer composite resonator structure are evaluated. The calculated results reveal that the piezoelectric coefficient d33, density, and velocity of the c-axis oriented AlN thin film are 4.19pm∕V, 3187.3kg∕m3, and 10631m∕s, respectively.
Frequency-dependent nonlinear optical properties with explicitly correlated coupled-cluster response theory using the CCSD(R12) model
Authors: Neiss Christian , Hättig Christof
Published: April 2007

Response theory up to infinite order is combined with the explicitly correlated coupled-cluster singles and doubles model including linear-r12 corrections, CCSD(R12). The additional terms introduced by the linear-r12 contributions, not present in the conventional CCSD calculation, are derived and discussed with respect to the extra costs required for their evaluation. An implementation is presented up to the cubic response function for one-electron perturbations, i.e., up to frequency-dependent second hyperpolarizabilities. As first applications the authors computed the electronic polarizabilities and second hyperpolarizabilities of BH, N2, and formaldehyde and show that the improvement in the one-electron basis set convergence known from the R12 method for ground state energies is retained for higher-order optical properties. Frequency-dependent results are presented for the second hyperpolarizability of N2.
Calculation of the electric hypershielding at the nuclei of molecules in a strong magnetic field
Authors: Caputo M. C. , Ferraro M. B. , Pagola G. I. , Lazzeretti P.
Published: April 2007

The third-rank electric hypershielding at the nuclei of 14 small molecules has been evaluated at the Hartree-Fock level of accuracy, by a pointwise procedure for the geometrical derivatives of magnetic susceptibilities and by a straightforward use of its definition within the Rayleigh-Schrödinger perturbation theory. The connection between these two quantities is provided by the Hellmann-Feynman theorem. The magnetically induced hypershielding at the nuclei accounts for distortion of molecular geometry caused by strong magnetic fields and for related changes of magnetic susceptibility. In homonuclear diatomics H2, N2, and F2, a field along the bond direction squeezes the electron cloud toward the center, determining shorter but stronger bond. It is shown that constraints for rotational and translational invariances and hypervirial theorems provide a natural criterion for Hartree-Fock quality of computed nuclear electric hypershielding.
Optical properties of InGaN quantum dots grown by SiNx nanomasks
Authors: Huang L. L. , Chang H. J. , Chou Y. Y. , Wang C. H. , Chen T. T. , Chen Y. F. , Tsai J. Y. , Wang S. C. , Kuo H. C.
Published: April 2007

InGaN quantum dots (QDs) deposited on SiNx nanomasks have been investigated by atomic force microscopy, photoluminescence (PL), and photoluminescence excitation (PLE) measurements. It was found that the size of QDs can be well controlled by SiNx nanomasks, enabling the manipulation of quantum confinement effect. The PL spectra of InGaN QDs contain several fine structures, and the main peaks can be attributed to families of QDs with different sizes. The emission arising from InGaN QDs and GaN buffer layer can be clearly distinguished based on PLE measurement, which can be used to improve the interpretation in the previous reports. Our study indicates that the quantum confined Stark effect due to piezoelectric field plays a very important role in the optical properties of InGaN QDs, which is very useful for the application of optoelectronic devices.
Hairpin vortex organization in wall turbulence
Authors: Adrian Ronald J.
Published: April 2007

Coherent structures in wall turbulence transport momentum and provide a means of producing turbulent kinetic energy. Above the viscous wall layer, the hairpin vortex paradigm of Theodorsen coupled with the quasistreamwise vortex paradigm have gained considerable support from multidimensional visualization using particle image velocimetry and direct numerical simulation experiments. Hairpins can autogenerate to form packets that populate a significant fraction of the boundary layer, even at very high Reynolds numbers. The dynamics of packet formation and the ramifications of organization of coherent structures (hairpins or packets) into larger-scale structures are discussed. Evidence for a large-scale mechanism in the outer layer suggests that further organization of packets may occur on scales equal to and larger than the boundary layer thickness.
Stabilization of the second-order susceptibility induced in a sulfide chalcogenide glass by thermal poling
Authors: Zeghlache H. , Guignard M. , Kudlinski A. , Quiquempois Y. , Martinelli G. , Nazabal V. , Smektala F.
Published: April 2007

A second-order susceptibility χ(2) is created by the thermal poling method in a bulk sample of Ga5Ge20Sb10S65 sulfide chalcogenide glass. We present experimental results focusing on the time-evolution properties of the created nonlinear layer. By cycling the poling operation on a sample, the generated second harmonic signal is improved, and the second-order nonlinearity is shown to be stable over several months. The χ(2) susceptibility profile is carefully reconstructed and its maximum value reaches 4–5 pm/V.
Evolution of the millimeter-wave collective Thomson scattering system of the high-field tokamak Frascati Tokamak Upgrade
Authors: Tartari U. , Grosso G. , Granucci G. , Gandini F. , Garavaglia S. , Grossetti G. , Simonetto A. , Mellera V. , Muzzini V. , Lubyako L. , Shalashov A. , Orsitto F. P. , Ciccone G. , Volpe F.
Published: April 2007

We first describe the improved receiving system of the diagnostic experiment of millimeter-wave collective Thomson scattering being run on the Frascati Tokamak Upgrade (FTU), and then discuss some peculiar problems and new operating procedures related to the investigation of strong anomalous spectra of nonthermal origin, many-orders-of-magnitude stronger than the ion thermal feature merged in them, systematically observed in the experimentation, and finally ascribed to a perturbation of the gyrotron that generates the probing beam. Arguments in favor of a more general valence of the solutions actuated for the specific case of FTU are finally given.
Magnetization and magnetoresistance of common alloy wires used in cryogenic instrumentation
Authors: Abrecht M. , Adare A. , Ekin J. W.
Published: April 2007

We present magnetization and magnetoresistance data at liquid-helium and liquid-nitrogen temperatures for wire materials commonly used for instrumentation wiring of specimens, sensors, and heaters in cryogenic probes. The magnetic susceptibilities in Systeme International units at 4.2 K were found to be: Manganin 1.25×10−2, Nichrome 5.6×10−3, and phosphor bronze −3.3×10−5, indicating that phosphor bronze is the most suitable for high-field applications. We also show the ferromagnetic hysteresis loop of Constantan wire at liquid-helium temperature. The magnetoresistance of these four wires was relatively small: the changes in resistance at 4 K due to a 10 T transverse magnetic field are –2.56% for Constantan, –2.83% for Manganin, +0.69% for Nichrome, and +4.5% for phosphor bronze, compared to about +188% for a typical copper wire under the same conditions.
Hybrid method coupling fluctuating hydrodynamics and molecular dynamics for the simulation of macromolecules
Authors: Giupponi G. , De Fabritiis G. , Coveney Peter V.
Published: April 2007

We present a hybrid computational method for simulating the dynamics of macromolecules in solution which couples a mesoscale solver for the fluctuating hydrodynamics (FH) equations with molecular dynamics to describe the macromolecule. The two models interact through a dissipative Stokesian term first introduced by Ahlrichs and Dünweg [J. Chem. Phys. 111, 8225 (1999)]. We show that our method correctly captures the static and dynamical properties of polymer chains as predicted by the Zimm model. In particular, we show that the static conformations are best described when the ratio σ∕b=0.6, where σ is the Lennard-Jones length parameter and b is the monomer bond length. We also find that the decay of the Rouse modes’ autocorrelation function is better described with an analytical correction suggested by Ahlrichs and Dünweg. Our FH solver permits us to treat the fluid equation of state and transport parameters as direct simulation parameters. The expected independence of the chain dynamics on various choices of fluid equation of state and bulk viscosity is recovered, while excellent agreement is found for the temperature and shear viscosity dependence of center of mass diffusion between simulation results and predictions of the Zimm model. We find that Zimm model approximations start to fail when the Schmidt number Sc≲30. Finally, we investigate the importance of fluid fluctuations and show that using the preaveraged approximation for the hydrodynamic tensor leads to around 3% error in the diffusion coefficient for a polymer chain when the fluid discretization size is greater than 50Å.
Laser-induced plasmas from the ablation of metallic targets: The problem of the onset temperature, and insights on the expansion dynamics
Authors: Bleiner Davide , Bogaerts Annemie , Belloni Fabio , Nassisi Vincenzo
Published: April 2007

Laser-induced plasmas are transient systems rapidly aging in few nanoseconds of evolution. Time-of-flight spectrometry allowed studying initial plasma characteristics based on frozen translational degrees of freedom, hence overcoming intrinsic limitations of optical spectroscopy. Experimental ion velocity distributions were reconstructed as developed during the longitudinal plasma expansion. The obtained onset plasma temperatures are in the range of ∼18–45eV depending on the ablated metals. Also the ion angular spreads were found to be a function of ablated metal, e.g., the narrowest for Fe, the broadest for Al, due to different collisional coupling in the plasma population.
Photoelectron imaging of copper and silver mono- and diamine anions
Authors: Sobhy M. A. , Castleman A. W.
Published: April 2007

The results of photoelectron imaging experiments of Cu and Ag mono- and diamine anions are reported. The photoelectron images were recorded at two photon energies, 800 and 527nm. The vertical detachment energies of CuNH2− and AgNH2− are lower than those of the respective atomic metal ion and are measured to be 1.11±0.05 and 1.23±0.05eV, respectively. By contrast, the electron detachment energies for Cu(NH2)2− and Ag(NH2)2− are higher than those of the corresponding metal ion and are determined to be 1.48±0.05 and 1.85±0.05eV, respectively. Energy-dependent photoelectron anisotropy parameters are also reported. The photodetachment of the Cu and Ag mono- and diamine anions exhibit a cos2θ angular dependence relative to the direction of the laser polarization. The nature of the chemical bonding and the symmetry of the highest occupied molecular orbitals are discussed in relevance to the measured anisotropy parameters.