bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and characterization of uniform radiopaque polystyrene microspheres for X‐ray imaging by a single‐step swelling process
Authors: Galperin Anna , Margel David , Margel Shlomo
Published: June 2006

Uniform radiopaque polystyrene microspheres of ∼2.3 ± 0.2 μm were prepared by a single‐step swelling of 2.3 ± 0.2 μm polystyrene template microspheres, dispersed in an aqueous solution with methylene chloride emulsion droplets containing 2,3,5‐triiodobenzoylethyl ester. After completing the swelling process, the methylene chloride was evaporated in order to lock the 2,3,5‐triiodobenzoylethyl ester in the polystyrene microspheres. The influence of the weight ratio [2,3,5‐triiodobenzoylethyl ester]/[polystyrene] on the % of entrapped 2,3,5‐triiodobenzoylethyl ester was elucidated. Characterization of the radiopaque polystyrene microspheres was accomplished by light microscope, FTIR, TGA, SEM, XPS, and elemental analysis. The radiopacity of the microspheres was demonstrated by an imaging technique based on X‐ray absorption usually used in hospitals. This novel method of encapsulation of 2,3,5‐triiodobenzoylethyl ester within polystyrene microspheres by a single‐step swelling process may be used as a model for encapsulation of various hydrophobic radiopaque drugs within uniform polystyrene template particles of various diameters for different X‐ray imaging needs, e.g., blood pool, body organs, embolization, dental composition, implants, protheses, and nanocomposites. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
Molecular cloning and characterization of alpha‐class glutathione S‐transferase gene from the liver of silver carp, bighead carp, and other major chinese freshwater fishes
Authors: Liao Wan‐Qin , Liang Xu‐Fang , Wang Lin , Lei La‐Mei , Han Bo‐Ping
Published: June 2006

Two full‐length cDNAs encoding glutathione S‐transferase (GST) were cloned and sequenced from the hepatopancreas of planktivorous silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis). The silver carp and bighead carp GST cDNA were 920 and 978 bp in length, respectively, and both contained an open reading frame that encoding 223 amino acids. Partial GST cDNA sequences were also obtained from the liver of grass carp (Ctenopharyngodon idellus), crucian carp (Carassius auratu), mud carp (Cirrhinus molitorella), and tilapia (Oreochromis nilotica). All these GSTs could be classified as alpha‐class GSTs on the basis of their amino acid sequence identity with other species. The three‐dimensional structure of the silver carp GST was predicted using a computer program, and was found to fit the classical two‐domain GST structure. Using the genome walker method, a 875‐bp 5′‐flanking region of the silver carp GST gene was obtained, and several lipopolysaccharide (LPS) response elements were identified in the promoter region of the phytoplanktivorous fish GST gene, indicating that the GST gene expression of this fish might be regulated by LPS, released from the toxic blue‐green algae producing microcystins. To compare the constitutive expression level of the liver GST gene among the six freshwater fishes with completely different tolerance to microcystins, beta‐actin was used as control and the ratio GST/beta‐actin mRNA (%) was determined as 130.7 ± 6.6 (grass carp), 103.1 ± 8.9 (bighead carp), 92.6 ± 15.0 (crucian carp), 72.3 ± 7.8 (mud carp), 58.8 ± 11.5 (silver carp), and 33.6 ± 13.7 (tilapia). The constitutive expression level of the liver GST gene clearly shows that all the six freshwater fishes had a negative relationship with their tolerance to microcystins: high‐resistant fishes (phytoplanktivorous silver carp and tilapia) had the lowest tolerance to microcystins and the high‐sensitive fish (herbivorous grass carp) had the highest tolerance to microcystins. Taken together with the reciprocal relationship of constitutive and inducible liver GST expression level in some of the tested fish species to microcystin exposure, a molecular mechanism for different microcystin detoxification abilities of the warm freshwater fishes was discussed. © 2006 Wiley Periodicals, Inc. J Biochem Mol Toxicol 20:114–126, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20125
Systematic QM/MM investigation of factors that affect the cytochrome P450‐catalyzed hydrogen abstraction of camphor
Authors: Altun Ahmet , Shaik Sason , Thiel Walter
Published: June 2006

The hydrogen abstraction reaction of camphor in cytochrome P450cam has been investigated in the native enzyme environment by combined quantum mechanical/molecular mechanical (QM/MM) calculations and in the gas phase by density functional calculations. This work has been motivated by contradictory published QM/MM results. In an attempt to pinpoint the origin of these discrepancies, we have systematically studied the factors that may affect the computed barriers, including the QM/MM setup, the optimization procedures, and the choice of QM region, basis set, and protonation states. It is found that the ChemShell and QSite programs used in the published QM/MM calculations yield similar results at given geometries, and that the discrepancies mainly arise from two technical issues (optimization protocols and initial system preparation) that need to be well controlled in QM/MM work. In the course of these systematic investigations, new mechanistic insights have been gained. The crystallographic water 903 placed near the oxo atom of Compound I lowers the hydrogen abstraction barrier by ca. 4 kcal/mol, and thus acts as a catalyst for this reaction. Spin density may appear at the A‐propionate side chain of the heme if the carboxylate group is not properly screened, which might be expected to happen during protein dynamics, but not in static equilibrium situations. There is no clear correlation between the computed A‐propionate spin density and the hydrogen abstraction barrier, and hence, no support for a previously proposed side‐chain mediated transition state stabilization mechanism. Standard QM/MM optimizations yield an A‐propionate environment close to the X‐ray structure only for protonated Asp297, and not for deprotonated Asp297, but the computed barriers are similar in both cases. An X‐ray like A‐propionate environment can also be obtained when deprotonated Asp297 is included in the QM region and His355 is singly protonated, but this Compound II‐type species with a closed‐shell porphyrin ring has a higher hydrogen abstraction barrier and should thus not be mechanistically relevant. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 1324–1337, 2006
Photodynamic therapy of brain tumors—A work in progress
Authors: Muller Paul J. , Wilson Brian C.
Published: June 2006

Background and Objectives

PDT has been used in the treatment of malignant brain tumors. This communication updates our series of unselected malignant gliomas treated with Photofrin‐PDT.

Study Design and Methods

We examined the records of 112 patients with malignant gliomas, metastatic brain tumors and meningiomas treated with Photofrin‐PDT at St. Michael's Hospital, Toronto. These patients were treated prior to the onset of ongoing randomized trials in Photofrin PDT or had pathology that excluded them from such trials.

Results

The overall post‐PDT survival of 96 patients with supratentorial gliomas was 42 weeks, with a 40 and 22% 1‐ and 2‐year survival, respectively. The greater the degree of oligodendroglial involvement the longer was the survival. Seventy‐five percent of patients had no significant post‐operative complications.

Conclusions

Photofrin‐PDT was safe. However, higher light doses than were used in these patients may be required for improved responses. Lasers Surg. Med. 38:384–389, 2006. © 2006 Wiley‐Liss, Inc.
Multicell tumor spheroids in photodynamic therapy
Authors: Madsen Steen J. , Sun Chung‐Ho , Tromberg Bruce J. , Cristini Vittorio , De Magalhães Nzola , Hirschberg Henry
Published: June 2006

Background and Objectives

Multicell spheroids (MCSs) represent a simple in vitro system ideally suited for studying the effects of a wide variety of investigational treatments including photodynamic therapy (PDT).

Study Design/Materials and Methods

In the first section of this review study, an overview of the current literature on MCS in PDT will be presented. Knowledge of basic PDT parameters has been gained from numerous MCS studies, in particular, the mechanisms of sensitizer photobleaching have been elucidated. MCSs have also proven useful for the study of complex PDT treatment regimens including multiple treatments and combined therapies involving PDT and ionizing radiation or hyperthermia. The purpose of the second part of this review is to present results from recent studies in our laboratory aimed at developing MCS models suitable for investigating tumor cell invasion and angiogenesis—processes characteristic of high‐grade gliomas.

Results and Conclusion

To that end, progress has recently been made to develop a more accurate in vivo brain tumor model consisting of biopsy‐derived human tumor spheroids implanted into the brains of immunodeficient rats. Finally, recent work suggests that computer simulations may prove useful to describe the growth of MCS and predict the effects of investigational therapies including PDT. Such in silico models have made a number of counterintuitive predictions that have been verified in vitro and, as such, could guide the development of improved therapeutics. Lasers Surg. Med. 38:555–564, 2006. © 2006 Wiley‐Liss, Inc.
Nature: A rich source for developing multifunctional agents. tumor‐imaging and photodynamic therapy
Authors: Pandey Ravindra K. , Goswami Lalit N. , Chen Yihui , Gryshuk Amy , Missert Joseph R. , Oseroff Allan , Dougherty Thomas J.
Published: June 2006

The purpose of this review is to call attention in the use of chlorophyll‐a and bacteriochlorophyll‐a to develop more than 600 photosensitizers (λ max 660 nm–800 nm) during the last 15 years (1990–2005) at the Photodynamic Therapy Center, Roswell Park Cancer Institute, Buffalo. This article mainly includes the chemistry, preclinical results, and brief clinical data of some of the most effective photosensitizers. The utility of the tumor‐avid photosensitizers in developing multimodality agents (imaging and therapy) is also presented. Lasers Surg. Med. 38:445–467, 2006. © 2006 Wiley‐Liss, Inc.
Local physiological changes during photodynamic therapy
Authors: Busch Theresa M.
Published: June 2006

Background and Objective

Herein an overview is provided of the causes, consequences, and significance of photodynamic therapy (PDT)‐mediated effects on tumor oxygenation and blood flow during illumination.

Study Design/Materials and Methods

Techniques particularly valuable to this research have included tissue oxygen tension measurement by the Eppendorf pO2 Histograph; spatial quantification of hypoxia by EF3 and EF5; and tissue oxygenation/blood flow monitoring by diffuse reflectance/correlation spectroscopy.

Results

Severe hypoxia was measured in vivo during PDT and is shown to be a consequence of photochemical oxygen consumption and/or compromised vascular perfusion. Oxygen depletion can be controlled by treatment regimen, occurs in a spatially‐definable pattern, and is therapy‐limiting. PDT‐induced changes in tumor oxygenation during illumination are correlated with outcome. In PDT‐treated tissues, blood flow also is determined by treatment regimen and correlates with treatment response.

Conclusions

Photodynamic therapy creates distinct, measurable changes in tumor oxygen and blood flow during illumination. These physiological changes may ultimately affect treatment efficacy. Lasers Surg. Med. 38:494–499, 2006. © 2006 Wiley‐Liss, Inc.
Control of pesticide residues by liquid chromatography‐mass spectrometry to ensure food safety
Authors: Picó Yolanda , Font Guillermina , José Ruiz María , Fernández Mónica
Published: June 2006

Liquid chromatography‐mass spectrometry (LC‐MS) has become an invaluable technique for the control of pesticide residues to ensure food safety. After an introduction about the regulations that highlights its importance to meet the official requirements on analytical performance, the different mass spectrometers used in this field of research, as well as the LC‐MS interfaces and the difficulties associated with quantitative LC‐MS determination, are discussed. The ability to use practical data for quantifying pesticides together with the option of obtaining structural information to identify target and non‐target parent compounds and metabolites are discussed. Special attention is paid to the impact of sample preparation and chromatography on the ionization efficiency of pesticides from food. The last section is devoted to applications from a food safety point of view. © 2006 Wiley Periodicals, Inc.
Quantitative and qualitative differences in protein expression between papillary thyroid carcinoma and normal thyroid tissue
Authors: Brown Lewis M. , Helmke Steve M. , Hunsucker Stephen W. , Netea‐Maier Romana T. , Chiang Simon A. , Heinz David E. , Shroyer Kenneth R. , Duncan Mark W. , Haugen Bryan R.
Published: June 2006

In order to better understand basic mechanisms of tumor development and identify potential new biomarkers, we have performed difference gel electrophoresis (DIGE) and peptide mass fingerprinting on pooled protein extracts from patients with papillary thyroid carcinoma (PTC) compared with matched normal thyroid tissue. Image analysis of DIGE gels comparing PTC and matched normal thyroid tissue protein indicated that 25% of the protein spots were differentially expressed at a 2.5‐fold cutoff and 35% at two‐fold. Comparison between two different pools of protein from normal thyroid tissues revealed differential protein expression of only 4% at 2.5‐fold and 6% at two‐fold cutoff. One hundred ninety‐two protein spots were identified by MALDI‐TOFMS, representing 90 distinct proteins. Excluding albumin, globins and thyroglobulin, imaging software determined 31 proteins to be differentially expressed at the two‐fold (or greater) level. Individual gel comparisons (PTC vs. matched normal) from five patients established that 15/31 (48%) of these proteins exhibited statistically significant differential expression. Previously identified molecular markers in this group of proteins include cathepsin B, cytokeratin 19, and galectin‐3. Novel differentially expressed proteins include S100A6, moesin, HSP70 (BiP), peroxiredoxin 2, protein phosphatase 2, selenium binding protein 1, vitamin D binding protein, and proteins involved in mitochondrial function. The use of two‐dimensional gel electrophoresis (2DGE) revealed a significantly altered protein mass and/or pI in 10%–15% of proteins, suggesting alternatively spliced forms and other posttranslational modification of proteins revealed by this approach. We confirmed S100A6 as a potentially useful biomarker using immunohistochemical analysis (85% sensitivity and 69% specificity for distinguishing benign from malignant thyroid neoplasms). In summary, proteomic analysis of PTC using DIGE and mass spectrometry has confirmed several known biomarkers, uncovered novel potential biomarkers, and provided insights into global pathophysiologic changes in PTC. Many of the differences observed would not have been detected by genomic or other proteomic approaches. © 2006 Wiley‐Liss, Inc.
Temperature and solvent dependent NMR studies on mangiferin and complete NMR spectral assignments of its acyl and methyl derivatives
Authors: Faizi Shaheen , Zikr‐ur‐Rehman Sadia , Ali Muhammad , Naz Aneela
Published: June 2006

By employing concerted 1 and 2D NMR techniques, exact NMR spectral assignments have been made of the acyl (2–7) and methyl (8 and 9) derivatives of mangiferin (1) isolated from the leaves of Bombax ceiba. Derivatives 2, 8 and 9 have been reported in literature, while 3–7 represent new compounds. The acetates 2 and 3 were found to be unstable and were converted into the same penta‐acetate 4 at room temperature. Extensive NMR studies on mangiferin (1) and its derivatives showed that H‐4 exchanges with deuterium of the solvent molecule more easily. This exchange under acidic conditions occurred at that position (C‐4) where electrophilic substitution reactions can easily take place. This is the first report describing the exchange of C‐4 proton of mangiferin (1), or any other xanthone, with deuterium of solvent molecules. Copyright © 2006 John Wiley & Sons, Ltd.
SodaConstructing knowledge through exploratoids
Authors: Svarovsky Gina Navoa , Shaffer David Williamson
Published: June 2006

In this article, we describe a preliminary study that integrates research on engineering design activities for K‐12 students with work on microworlds as learning tools. Here, we extend these bodies of research by exploring whether—and how—authentic recreations of engineering practices can help students develop conceptual understanding of physics. We focus on the design–build–test (DBT) cycle used by professional engineers in simulation‐based rapid modeling. In this experiment, middle‐school students worked for 10 hr during a single weekend to solve engineering design challenges using SodaConstructor, a Java‐based microworld, as a simulation environment. As a result of the experiment, students learned about center of mass. Our data further suggest that in the process of simulation‐based modeling, rapid iterations of the DBT cycle progressively linked students' interest in the design activities and understanding of the concept of center of mass. We suggest that these rapid iterations of the DBT cycle functioned as exploratoids: short fragments of exploratory action in a microworld that cumulatively develop interest in and understanding of important scientific concepts. © 2006 Wiley Periodicals, Inc. J Res Sci Teach
Do antidepressants influence mood patterns? A naturalistic study in bipolar disorder
Authors: Bauer M. , Rasgon N. , Grof P. , Glenn T. , Lapp M. , Marsh W. , Munoz R. , Suwalska A. , Baethge C. , Bschor T. , Alda M. , Whybrow P.C.
Published: June 2006

This prospective, longitudinal study compared the frequency and pattern of mood changes between outpatients receiving usual care for bipolar disorder who were either taking or not taking antidepressants. One hundred and eighty-two patients with bipolar disorder self-reported mood and psychiatric medications for 4 months using a computerized system (ChronoRecord) and returned 22,626 days of data. One hundred and four patients took antidepressants, 78 did not. Of the antidepressants taken, 95% were selective serotonin or norepinephrine reuptake inhibitors, or second-generation antidepressants. Of the patients taking an antidepressant, 91.3% were concurrently taking a mood stabilizer. The use of antidepressants did not influence the daily rate of switching from depression to mania or the rate of rapid cycling, independent of diagnosis of bipolar I or II. The primary difference in mood pattern was the time spent normal or depressed. Patients taking antidepressants frequently remained in a subsyndromal depression. In this naturalistic study using self-reported data, patients with bipolar disorder who were taking antidepressants—overwhelmingly not tricyclics and with a concurrent mood stabilizer—did not experience an increase in the rate of switches to mania or rapid cycling compared to those not taking antidepressants. Antidepressants had little impact on the mood patterns of bipolar patients taking mood stabilizers.
Evidence for a secretory pathway Ca2+‐ATPase in sea urchin spermatozoa
Authors: Gunaratne Herath Jayantha , Vacquier Victor D.
Published: June 2006

Plasma membrane, sarco‐endoplasmic reticulum and secretory pathway Ca2+‐ATPases (designated PMCA, SERCA and SPCA) regulate intracellular Ca2+ in animal cells. The presence of PMCA, and the absence of SERCA, in sea urchin sperm is known. By using inhibitors of Ca2+‐ATPases, we now show the presence of SPCA and Ca2+ store in sea urchin sperm, which refills by SPCA‐type pumps. Immunofluorescence shows SPCA localizes to the mitochondrion. Ca2+ measurements reveal that ∼75% of Ca2+ extrusion is by Ca2+ ATPases and 25% by Na+ dependent Ca2+ exchanger/s. Bisphenol, a Ca2+ ATPase inhibitor, completely blocks the acrosome reaction, indicating the importance of Ca2+‐ATPases in fertilization.
Involvement of in the abnormal hyperphosphorylation of tau and its reversal by Memantine
Authors: Chohan Muhammad Omar , Khatoon Sabiha , Iqbal Inge-Grundke , Iqbal Khalid
Published: June 2006

The activity of protein phosphatase (PP)‐2A, which regulates tau phosphorylation, is compromised in Alzheimer disease brain. Here we show that the transient transfection of PC12 cells with inhibitor‐2 of PP2A causes abnormal hyperphosphorylation of tau at Ser396/Ser404 and Ser262/Ser356. This hyperphosphorylation of tau is observed only when a sub‐cellular shift of takes place from the nucleus to the cytoplasm and is accompanied by cleavage of into a 20 kDa fragment. Memantine, an un‐competitive inhibitor of N‐methyl‐d‐aspartate receptors, inhibits this abnormal phosphorylation of tau and cell death and prevents the inhibition of PP2A activity in vitro. These findings demonstrate novel mechanisms by which regulates the intracellular activity of PP2A and phosphorylation of tau, and by which Memantine modulates PP2A signaling and inhibits neurofibrillary degeneration.
Systems theory for geospace plasma dynamics
Authors: Vassiliadis Dimitris
Published: June 2006

This is a tutorial review on systems theory and its applications to space plasma physics and, more broadly, on geophysics. With its basis on the state representation of a plasma the theory is widely applicable, but it is of particular interest for dynamical, nonlinear, or out‐of‐equilibrium regimes that cannot be represented by traditional microscopic modeling. Two distinct, but closely related, branches of the theory are applied when the plasma dynamics is traced to first principles and when it needs to be derived from experimental data. A framework of modeling methods is presented in order of increasing complexity: enumeration of the effective degrees of freedom, measurement of the linear dynamics and stability, and generalization to their nonlinear counterparts. The relation between symmetries in the plasma system and modes in its structure and response is discussed. Signal processing methods are presented, illustrated by examples, and their relative merits and limitations are discussed. The dynamical framework provides a new approach alongside the traditional perturbative and statistical‐mechanical methodologies and is directly relevant to the development of space weather applications.
Visualization of particle behavior within a porous medium: Mechanisms for particle filtration and retardation during downward transport
Authors: Yoon Joon Sik , Germaine John T. , Culligan Patricia J.
Published: June 2006

A technique for visualizing particle transport in the interior of a porous medium is presented. The technique, which includes the construction of a translucent medium and the use of laser‐induced fluorescence for particle tracking, was used to examine the behavior of a dilute suspension of negatively charged, micron‐sized particles in the interior of uniform glass bead packs during one‐dimensional, downward flow. Particle behavior as a function of pore fluid velocity and bead surface roughness was observed at both the macroscopic and microscopic levels. Experimental results show that particle filtration occurred only at solid‐solid contact points (contact filtration) in smooth bead packs, while particle filtration occurred at the top of bead surfaces (surface filtration) as well as at solid‐solid contact points in rough bead packs. Particle contact filtration was the result of physical straining at solid‐solid contact points, while surface filtration was the result of particles interlocking on surface asperities. In both smooth and rough bead packs the filtration capacity of the medium decreased with the pore fluid velocity. In smooth bead packs the filtration capacity was approximately invariant with transport distance, while in the rough bead packs the filtration capacity showed a decrease with transport distance. This decrease was attributed to the early surface filtration of larger particles as a result of gravitational sedimentation. The accumulation of reversibly attached particles was observed even when particle pore fluid concentrations were stable.
On microinstabilities in the foot of high Mach number perpendicular shocks
Authors: Matsukiyo S. , Scholer M.
Published: June 2006

Microinstabilities excited in the foot of a supercritical perpendicular shock wave are investigated. A two‐dimensional full particle simulation with periodic boundary conditions in both directions using the physical ion to electron mass ratio is performed as a proxy for the foot region where incoming and specularly reflected ions overlap. The simulation shows that six types of different instabilities are excited in a time period shorter than ion gyroperiod of the reflected ions. The most dominant instability is the modified two‐stream instability, which leads to strong parallel electron heating through a so‐called two step instability and to ion phase space holes.
Numerical modeling of the 26 November 1999 Vanuatu tsunami
Authors: Ioualalen M. , Pelletier B. , Watts P. , Regnier M.
Published: June 2006

On 26 November 1999, at 1321 UT, central Vanuatu was struck by a large offshore earthquake (Mw 7.5) followed by a tsunami that killed five people and caused significant damage to nearshore structures, mainly at Martelli Bay, south Pentecost Island. The tsunami is simulated using the Geowave model. The Tsunami Open and Progressive Initial Conditions System (TOPICS) source component of the model simulates the initial water column deformation, and the propagation and runup are simulated with the FUNWAVE fully nonlinear Boussinesq and dispersive model. A special effort was made on the construction of the computational grid through comprehensive bathymetry data sets obtained especially from two multibeam bathymetric surveys performed after the earthquake and tsunami. Three different tsunami sources have been considered. The first one is the fault rupture itself, the second is a landslide located east of Ambrym Island, and the third source is a submarine structure within the Selwyn Strait that will be considered as a landslide, however, with a large uncertainty because it could be a result of lava deposit as well. It is found that the earthquake‐derived tsunami source fits most of the postsurvey observations, in particular the overall wave amplitudes (up to 6–7 m observed and simulated). The timing of the tsunami is also satisfactory when objective interpretation of the eyewitnesses is processed. Thus it is found that the hypothetical landslide‐derived tsunami contributions are not necessary to predict the tsunami. This is because they do not help in the tsunami timing but also because their wave amplitude contributions are one order of magnitude lower than that of the earthquake source.
Variations of Mars gravitational field based on the NASA/Ames general circulation model
Authors: Sanchez Braulio V. , Rowlands D. D. , Haberle Robert M.
Published: June 2006

The NASA/Ames general circulation model (GCM) has been used to compute time series for the variations in the Stokes coefficients expressing Mars' gravitational field in spherical harmonics. The sources of the variations are changes in the mass distribution of the atmosphere and changes in the planetary ice caps. The latter are due mainly to the condensation and sublimation of CO2 on the surface of Mars. Variations were obtained for coefficients up to degree and order 40, which is the maximum allowed by the spatial definition of the model. The time series covered a period of a full Martian year of 669 sols with a time step of 1.5 hours. The time series were analyzed by means of fast Fourier transforms. The largest variations occur in C10 corresponding to a 27.5‐mm displacement of the center of mass in the z‐direction. Other geoidal variations are C30 (17.7 mm), C20 (11.4 mm) and C50 (10.0 mm). The main harmonics are annual, (1/2)‐annual and (1/3)‐annual. Most of the power is due to ice caps variations. Mars Global Surveyor trajectory runs with and without the above orbit perturbations yield RMS differences in total position which range between 4.44 and 17.39 m over a 7‐day arc, depending on the season. A 7‐day simulated tracking data least squares solution in which some level of the perturbations is absorbed into initial state parameters yields RMS differences between 0.35 and 0.78 m in total position.
Spatial variability in river sediments and its link with river channel geometry
Authors: Rubin Yoram , Lunt Ian A. , Bridge John S.
Published: June 2006

This study explores the link between spatial variability within fluvial sedimentary strata and river channel geometry. This link is then used to determine the macrodispersion coefficients for solute transport in groundwater flow in river deposits. In doing that we combine concepts from sedimentology, geostatistics, and the stochastic‐Lagrangian theory of subsurface transport. It is proposed to analyze the spatial variability of river sediments in terms of transition probabilities. The transition probabilities can be determined from the averages and variances of the lengths of stratasets and their volumetric fractions using concepts developed by Carle and Fogg (1996) and Ritzi (2000). Strataset length scales are shown to correlate well with the geometry of the river channel and its bed forms and can be determined indirectly from aerial photogrammetry, and, more directly, through surface ground penetrating radar surveys. Stratal dimensions can also be related, using Lagrangian transport analysis, to macrodispersivity of subsurface transport. This allows relationships between the geometry of river channels and subsurface transport parameters of associated fluvial deposits. For demonstration the longitudinal macrodispersivity in a compound bar deposit in the gravelly, braided Sagavanirktok River was investigated.
Global gridded data set of the oxygen isotopic composition in seawater
Authors: LeGrande Allegra N. , Schmidt Gavin A.
Published: June 2006

We present a new 3‐dimensional 1° × 1° gridded data set for the annual mean seawater oxygen isotope ratio (δ18O) to use in oceanographic and paleoceanographic applications. It is constructed from a large set of observations made over the last 50 years combined with estimates from regional δ18O to salinity relationships in areas of sparse data. We use ocean fronts and water mass tracer concentrations to help define distinct water masses over which consistent local relationships are valid. The resulting data set compares well to the GEOSECS data (where available); however, in certain regions, particularly where sea ice is present, significant seasonality may bias the results. As an example application of this data set, we use the resulting surface δ18O as a boundary condition for isotope‐enabled GISS ModelE to yield a more realistic comparison to the isotopic composition of precipitation data, thus quantifying the ‘source effect’ of δ18O on the isotopic composition of precipitation.
Computation of Young’s moduli for chiral single-walled carbon nanotubes
Authors: Leung A. Y. T. , Yongdong Wu , Weifang Zhong
Published: June 2006

An energy-equivalent model is proposed to establish the computational formula of Young’s modulus for chiral single-walled carbon nanotubes (SWCNTs). First, the total system potential energy is obtained using the principle of molecular mechanics. Then, the computing formula of Young’s modulus of chiral SWCNT is obtained by comparing the total molecular potential energy with the strain energy of a corresponding thin cylinder. It is found that Young’s modulus of a chiral SWCNT is affected both by its diameter and chiral angle.
Multiscale approach to CO2 hydrate formation in aqueous solution: Phase field theory and molecular dynamics. Nucleation and growth
Authors: Tegze György , Pusztai Tamás , Tóth Gyula , Gránásy László , Svandal Atle , Buanes Trygve , Kuznetsova Tatyana , Kvamme Bjørn
Published: June 2006

A phase field theory with model parameters evaluated from atomistic simulations/experiments is applied to predict the nucleation and growth rates of solid CO2 hydrate in aqueous solutions under conditions typical to underwater natural gas hydrate reservoirs. It is shown that under practical conditions a homogeneous nucleation of the hydrate phase can be ruled out. The growth rate of CO2 hydrate dendrites has been determined from phase field simulations as a function of composition while using a physical interface thickness (0.85±0.07nm) evaluated from molecular dynamics simulations. The growth rate extrapolated to realistic supersaturations is about three orders of magnitude larger than the respective experimental observation. A possible origin of the discrepancy is discussed. It is suggested that a kinetic barrier reflecting the difficulties in building the complex crystal structure is the most probable source of the deviations.
Monolithic parallel linear compliant mechanism for two axes ultraprecision linear motion
Authors: Choi Kee-Bong , Kim Doo-Hyeong
Published: June 2006

In this study, a new parallel linear compliant mechanism is presented for two axes ultraprecision linear motion. The compliant mechanism for ultraprecision motion is chiefly implemented by monolithically machined flexures. Therefore, considerable interest has focused on a compliant mechanism structure based on flexures. The design of a parallel linear compliant mechanism for two linear motions based on flexures requires that the compliant mechanism has a structure to reduce rotational parasitic motion. In addition, the flexures should be deformed by the bending moment rather than axial force. In order to satisfy these requirements, a compliant mechanism consisting of quad-symmetric simple parallel linear springs and quad-symmetric double compound linear springs is proposed. The compliant mechanism is designed using a mathematical model and analyzed by the finite element method. The compliant mechanism is integrated with piezoelectric elements for driving forces and capacitance-type displacement sensors into an ultraprecision stage for two linear motions. Experiments demonstrate the performance of the ultraprecision stage implemented by the compliant mechanism.
Linear scaling calculation of maximally localized Wannier functions with atomic basis set
Authors: Xiang H. J. , Li Zhenyu , Liang W. Z. , Yang Jinlong , Hou J. G. , Zhu Qingshi
Published: June 2006

We have developed a linear scaling algorithm for calculating maximally localized Wannier functions (MLWFs) using atomic orbital basis. An O(N) ground state calculation is carried out to get the density matrix (DM). Through a projection of the DM onto atomic orbitals and a subsequent O(N) orthogonalization, we obtain initial orthogonal localized orbitals. These orbitals can be maximally localized in linear scaling by simple Jacobi sweeps. Our O(N) method is validated by applying it to water molecule and wurtzite ZnO. The linear scaling behavior of the new method is demonstrated by computing the MLWFs of boron nitride nanotubes.
Compact radiometric microwave calibrator
Authors: Fixsen D. J. , Wollack E. J. , Kogut A. , Limon M. , Mirel P. , Singal J. , Fixsen S. M.
Published: June 2006

The calibration methods for the ARCADE II instrument are described and the accuracy estimated. The Steelcast coated aluminum cones which comprise the calibrator have a low reflection while maintaining 94% of the absorber volume within 5mK of the base temperature (modeled). The calibrator demonstrates an absorber with the active part less than one wavelength thick and only marginally larger than the mouth of the largest horn and yet black (less than −40dB or 0.01% reflection) over five octaves in frequency.
Si nanocrystals in a distributed feedback laser cavity
Authors: Dohnalová K. , Pelant I. , Gilliot P. , Crégut O. , Hönerlage B.
Published: June 2006

We investigate an optically induced distributed-feedback cavity, containing a densely packed luminescent silicon nanocrystal layer in a SiO2 based matrix as active medium. In the presence of optical feedback, we have observed a nonlinear increase in the spectrally resolved emission intensity on the blue emission wing, which consists of two main contributions: (i) a broad amplified region around 550nm, showing fast photoluminescence decay around 100ns, depending on the excitation intensity, and (ii) a narrower peak located at about 580nm. The latter exhibits a spectral shift, which varies with the cavity tuning.
Feasibility study of superresolution continuous-wave electron paramagnetic resonance imaging
Authors: Hirata Hiroshi , Wakana Michi , Susaki Hitoshi
Published: June 2006

In this letter, we report that superresolution continuous-wave electron paramagnetic resonance (cw-EPR) imaging is feasible for enhancing spatial resolution in images of unpaired electrons. We demonstrate one-dimensional superresolution EPR imaging for phantoms of 1,1-diphenyl-2-picrylhydrazyl (DPPH) powder with a 650MHz cw-EPR imager. The spatial resolution was improved up to fivefold with iterative deconvolution techniques. Our superresolution EPR imaging includes two-stage postprocessing, i.e., noniterative deconvolution for measured EPR spectra and iterative deconvolution processing for a blurred EPR image profile with the point spread function of the low-pass window function being applied.
Tuneable magnetic susceptibility of nanocrystalline palladium
Authors: Drings Harald , Viswanath Raghavan N. , Kramer Dominik , Lemier Christian , Weissmüller Jörg , Würschum Roland
Published: June 2006

A charge-induced reversible variation of the paramagnetic susceptibility χ of Pd is reported. In situ charging was performed by means of a nanocrystallite-electrolyte composite. The charge-induced variation of χ is analyzed taking into account the modification of the charge carrier density by surface charging and the effect of charge-induced pressure on the nanocrystallites. The present studies may open up the way to switchable ferromagnetism.
Origin of detection wavelength tuning in quantum dots-in-a-well infrared photodetectors
Authors: Vukmirović Nenad , Indjin Dragan , Ikonić Zoran , Harrison Paul
Published: June 2006

A theoretical investigation is performed in order to understand the origin of change of the operating wavelength of quantum dots-in-a-well photodetectors when the well width is varied. The energy levels and wave functions were found using the eight-band strain dependent k∙p model and the intraband optical absorption spectrum was calculated in the dipole approximation within the framework of first order perturbation theory. It was found that the pure effect of changes of well width cannot be responsible for the shifts of the peaks observed in experiment [Raghavan et al., J. Appl. Phys. 96, 1036 (2004)], which are therefore ascribed to unintentional changes in dot dimensions.
Non-meanfield deterministic limits in chemical reaction kinetics
Authors: Lee DeVille R. E. , Muratov Cyrill B. , Vanden-Eijnden Eric
Published: June 2006

A general mechanism is proposed by which small intrinsic fluctuations in a system far from equilibrium can result in nearly deterministic dynamical behaviors which are markedly distinct from those realized in the meanfield limit. The mechanism is demonstrated for the kinetic Monte Carlo version of the Schnakenberg reaction where we identified a scaling limit in which the global deterministic bifurcation picture is fundamentally altered by fluctuations. Numerical simulations of the model are found to be in quantitative agreement with theoretical predictions.
Variation in protein abundance profiles in the M. semitendinosus of lambs bred from sires selected on the basis of growth and muscling potential
Authors: McDonagh M. B. , Ferguson K. L. , Bacic A. , Gardner G. E. , Hegarty R. S.
Published: June 2006

Relative abundance of proteins localised in the nuclear-enriched, total cell membrane and cytosolic fractions of the semitendinosus muscle was compared between lambs bred from control (C), high muscling (M), and high growth rate (G) sires. In total, 31 proteins were identified whose abundance was differentially regulated between sire type. Differences in hind-limb muscle development between M lambs and C and G lambs were reflected in levels of proteins that regulate or function in cellular mechanisms of protein and energy metabolism. Despite no apparent difference in hind-limb muscle growth in G lambs compared to C, G lambs exhibited marked differences in proteins involved in regulation and function of energy metabolism. These results detail pathways that can be specifically targeted to enhance muscle accretion and growth in lambs. The development of means to manipulate these cellular mechanisms may yield greater gains in muscle accretion and growth rate than breeding on the basis for genetic capacity alone.
Indices of cellular development in muscles of lambs are influenced by sire estimated breeding values and pastoral nutritional system
Authors: Greenwood P. L. , Gardner G. E. , Hegarty R. S.
Published: June 2006

This study examined influences of sire (n = 9) estimated breeding values (EBVs), sire-group (Muscle, Growth, and Control), and nutrition (low and high quality and availability pasture) from birth to slaughter at ~8 months of age on indices of muscle cellularity and transcriptional and translational capacity in 56 castrate lambs. Effects of nutritional systems to 8 months of age were greater, overall, than those due to EBVs or sire-group. Amount of DNA increased with increasing EBV for post-weaning eye muscle depth (PEMD or Muscle EBV) in longissimus but not in semimembranosus and semitendinosus muscles, while Muscle EBV also had an inverse association with concentration of DNA. Protein to DNA and RNA to DNA were related positively to Muscle EBV, the associations being strongest for the semitendinosus muscle. Post-weaning weight (PWWT or Growth) EBV correlated positively with the RNA to DNA ratio and, among high but not low nutrition lambs, was inversely related to concentration of muscle DNA, whereas post-weaning fat depth (PFAT or Fat) EBV was correlated positively with RNA concentration. Overall, the magnitude of effects of sire-group was less than for sire EBVs, presumably due to differing selection pressures for muscling, fatness, and growth. High nutrition lambs had more protein to DNA than low nutrition lambs in the longissimus and semitendinosus muscles, but not in the semimembranosus muscle. In low compared with high nutrition lambs, concentration of DNA was greater in the longissimus and semitendinosus muscles. Total amount of DNA was reduced by more in low compared with high nutrition in the longissimus and semimembranosus than in the semitendinosus, and amount of protein was reduced by more in low compared with high nutrition in the longissimus than in the other two muscles. We conclude that genetic selection for eye muscle depth in sheep has differing effects on cellular characteristics of the longissimus, semimembranosus, and semitendinosus muscles, and has greater effects on muscle cellular characteristics than genetic selection for post-weaning weight or fat depth.
Preface: Genetic improvement of lamb—industry issues and the need for integrated research
Authors: Pethick D. W. , Warner R. D. , Banks R. G.
Published: June 2006

This paper provides an introduction to the special edition of the Australian Journal of Agricultural Research dedicated to an integrated research program to understand the effects of genetic selection for live animal traits (growth, muscle, and fatness) that determine carcass and meat attributes. Combined with this are the effects of nutritional status of the dam and growing lamb. The reasons for, and general approach of, the research is outlined.
Revision of Nicrophorus in part: new species and inferred phylogeny of the nepalensis-group based on evidence from morphology and mitochondrial DNA (Coleoptera:Silphidae:Nicrophorinae)
Authors: Sikes Derek S. , Trumbo Stephen T. , Madge Ronald B.
Published: June 2006

Carrion beetles of the genus Nicrophorus Fabricius, 1775 (Silphidae) are well known for their biparental brood care and monopolisation of small vertebrate carcasses in subterranean crypts. Although the taxonomy of New World species has received modern attention, the fauna of Asia, primarily of the nepalensis-group of species, has not. Herein we revise this species-group and describe as new the following seven species: Nicrophorus charon Sikes & Madge (Sulawesi), Nicrophorus herscheli Sikes & Madge (Sumatra), Nicrophorus insignis Sikes & Madge (Flores Island), Nicrophorus melissae Sikes & Madge (Nepal, Bhutan), Nicrophorus reticulatus Sikes & Madge (Guadalcanal), Nicrophorus schawalleri Sikes & Madge (Gansu, Shaanxi, Sichuan Province) and Nicrophorus trumboi Sikes & Madge (Nepal, Bhutan). We obtained a preliminary phylogeny using morphology and mtDNA (COII). This was inferred using maximum likelihood and Bayesian methods with the Mkv and GTR+I+G models (parsimony was rejected by the Akaike information criterion for being excessively parameter-rich). The phylogenetic signal in the morphological dataset was not strong and results were confounded by a ‘long-branch’ species, N. reticulatus. The signal was stronger in the combined dataset and the COII-only dataset. The molecular phylogeny supported the new status of species N. trumboi and N. melissae. Support was found for a mainland origin of the group with subsequent radiations into the Malay Archipelago.
Molecular phylogeny of the bumble bee subgenus Pyrobombus (Hymenoptera:Apidae:Bombus) with insights into gene utility for lower-level analysis
Authors: Cameron Sydney A. , Hines Heather M. , Williams Paul H.
Published: June 2006

Comprising nearly 20% of all bumble bees, the subgenus Pyrobombus is distributed across diverse habitats in the Northern Hemisphere and exhibits considerable morphological and behavioural variation relative to other subgenera. Its size and variation have led to questions concerning its monophyly and intrasubgeneric relationships, but too few known morphological synapomorphies and insufficient taxon sampling have precluded robust answers to these questions. To obtain a robust phylogeny of the group, we obtained DNA sequences for 36 of the 43 species from four genes (mitochondrial 16S rRNA and three nuclear genes: elongation factor – 1α (EF-1α), long wavelength rhodopsin (LW Rh or opsin) and arginine kinase (ArgK)). Both Bayesian and parsimony phylogenies are well resolved and indicate a monophyletic Pyrobombus when assessed against representatives of 20 additional subgenera. The more conserved nuclear genes, especially EF-1α and ArgK, provided good support across all of the taxonomic levels examined, whereas support of the more rapidly evolving mt16S was restricted mostly to close relationships at the tips of the tree. The exon regions of ArgK were the most conserved and may be promising for higher-level phylogenetics. We discuss species relationships within Pyrobombus and its sister-group, Bombus s.s. + Alpinobombus, in relation to previous taxonomic studies.