bluuebunny/crossref_metadata_2025 huggingface dataset:
Neuroscience and accelerator mass spectrometry
Authors: Palmblad Magnus , Buchholz Bruce A. , Hillegonds Darren J. , Vogel John S.
Published: February 2005

Accelerator mass spectrometry (AMS) is a mass spectrometric method for quantifying rare isotopes. It has had a great impact in geochronology and archaeology and is now being applied in biomedicine. AMS measures radioisotopes such as 3H, 14C, 26Al, 36Cl and 41Ca, with zepto‐ or attomole sensitivity and high precision and throughput, allowing safe human pharmacokinetic studies involving microgram doses, agents having low bioavailability or toxicology studies where administered doses must be kept low (<1 µg kg−1). It is used to study long‐term pharmacokinetics, to identify biomolecular interactions, to determine chronic and low‐dose effects or molecular targets of neurotoxic substances, to quantify transport across the blood–brain barrier and to resolve molecular turnover rates in the human brain on the time‐scale of decades. We review here how AMS is applied in neurotoxicology and neuroscience. Copyright © 2005 John Wiley & Sons, Ltd.
Effect of chronic morphine exposure on the synaptic plasma‐membrane subproteome of rats: a quantitative protein profiling study based on isotope‐coded affinity tags and liquid chromatography/mass spectrometry
Authors: Prokai Laszlo , Zharikova Alevtina D. , Stevens Stanley M.
Published: February 2005

The effect of chronic morphine exposure on the synaptic plasma‐membrane subproteome in rats was studied by the isotope‐coded affinity tag (ICAT) method coupled with capillary reversed‐phase liquid chromatography/electrospray ionization mass spectrometry and tandem mass spectrometry. ICAT‐labeled tryptic peptides of synaptic membrane proteins were successfully identified using tandem mass spectrometry in conjunction with protein database searching. Several important synaptic plasma‐membrane proteins displayed significant regulation changes as a result of chronic morphine exposure in vivo. In particular, an integral membrane protein Na+/K+ ATPase (α‐subunit) involved in regulation of the cell membrane potential by controlling sodium and potassium ion permeability was downregulated by 39 ± 2%. This result was in excellent agreement with the reduction in electrogenic Na+, K+ pumping due to about 40% downregulation of Na+/K+ ATPase α3‐isoform in myenteric S‐neurons of morphine‐exposed guinea‐pigs measured by others via immunohistochemistry. The decrease in the abundance of non‐erythroid αII‐spectrin in the synaptic plasma‐membrane fraction was also observed, which was hypothetically associated with the breakdown of the protein due to the upregulation of the proteolytic enzyme caspase‐3 upon chronic morphine exposure. Copyright © 2005 John Wiley & Sons, Ltd.
Quantitative peptidomics of mouse pituitary: comparison of different stable isotopic tags
Authors: Che Fa‐Yun , Fricker Lloyd D.
Published: February 2005

Determining the relative levels of neuropeptides in two samples is important for many biological studies. An efficient, sensitive and accurate technique for relative quantitative analysis involves tagging the peptides in the two samples with isotopically distinct labels, pooling the samples and analyzing them using liquid chromatography/mass spectrometry (LC/MS). In this study, we compared two different sets of isotopic tags for analysis of endogenous mouse pituitary peptides: succinic anhydride with either four hydrogens or deuteriums and [3‐(2,5‐dioxopyrrolidin‐1‐yloxycarbonyl)propyl]trimethylammonium chloride with either nine hydrogens or deuteriums. These two labels react with amines and impart either a negative charge (succinyl) or a positive charge (4‐trimethylammoniumbutyryl (TMAB)). Every endogenous mouse pituitary peptide labeled with the light TMAB reagent eluted from the C18 reversed‐phase column at essentially the same time as the corresponding peptide labeled with the heavy reagent. Most of the peptides labeled with succinyl groups also showed co‐elution of the heavy‐ and light‐labeled forms on LC/MS. The mass difference between the heavy and light TMAB reagents (9 Da per label) was larger than that of the heavy and light succinyl labels (4 Da per label), and for some peptides the larger mass difference provided more accurate determination of the relative abundance of each form. Altogether, using both labels, 82 peptides were detected in Cpefat/fat mouse pituitary extracts. Of these, only 16 were detected with both labels, 41 were detected only with the TMAB label and 25 were detected only with the succinyl label. A number of these peptides were de novo sequenced using low‐energy collisional tandem mass spectrometry. Whereas the succinyl group was stable to the collision‐induced dissociation of the peptide, the TMAB‐labeled peptides lost 59 Da per H9 TMAB group. Several peptides identified in this analysis represent previously undescribed post‐translational processing products of known pituitary prohormones. In conclusion, both succinyl and TMAB isotopic labels are useful for quantitative peptidomics, and together these two labels provide more complete coverage of the endogenous peptides. Copyright © 2005 John Wiley & Sons, Ltd.
Polycondensations of Bisphenol‐A with Diphosgene or Triphosgene in Water‐Free Organic Solvents
Authors: Kricheldorf Hans R. , Böhme Sigrid , Schwarz Gert
Published: February 2005

Summary: Bisphenol‐A was polycondensed with diphosgene and excess pyridine in a mixture of dry dichloromethane and 1,4‐dioxane. The stoichiometry was varied to optimize the molecular weight. According to MALDI‐TOF mass spectra the fraction of cyclic polycarbonates increased with higher molecular weights. Analogous results were obtained with triphosgene. When pyridine was replaced by triethylamine, diethyl carbamoyl chloride was formed and an excess of diphosgene (plus triethylamine) yielded polycarbonates having one or two diethylcarbamate endgroups. However, the content of cycles increased again with the molecular weight and peaked for the sample with the maximum molecular weight. 1H NMR endgroup analyses confirmed the interpretation of the MALDI‐TOF mass spectra. SEC measurement indicated high polydispersity indices (around 7) for samples rich in cycles.

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Ink‐Jet Printing of Metallic Nanoparticles and Microemulsions
Authors: Kamyshny Alexander , Ben‐Moshe Matti , Aviezer Shai , Magdassi Shlomo
Published: February 2005

Summary: Two types of ink‐jet inks are presented: ink containing an aqueous dispersion of silver nanoparticles and an oil‐in‐water microemulsion‐based ink. The metallic ink contains nanoparticles of silver, which are formed in the presence of an ionic polymeric stabilizer. Sintering of the printed image obtained with the use of such silver‐based inks at temperatures as low as 300 °C results in formation of patterns possessing noticeable conductivity. The microemulsion inks are based on a thermodynamically stable microemulsion, in which the dispersed oil phase is a volatile solvent containing a water‐insoluble colorant. After contact of the jetted ink droplets with a substrate, nanodroplets of the microemulsion are converted into nanoparticles of the solubilized colorant. In some cases, it was found that the evaporation of microemulsion ink droplets leads to formation of rings composed of ordered nanoparticles.

Scheme of ink‐jet printing of an oil‐in‐water microemulsion followed by conversion of the nanodroplets into nanoparticles, caused by quick evaporation of the solvent within the microemulsion droplets. Therefore, the ink behaves as a dye‐based ink prior to printing, but after printing it behaves like a pigment‐based ink.

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Scheme of ink‐jet printing of an oil‐in‐water microemulsion followed by conversion of the nanodroplets into nanoparticles, caused by quick evaporation of the solvent within the microemulsion droplets. Therefore, the ink behaves as a dye‐based ink prior to printing, but after printing it behaves like a pigment‐based ink.
A compact wideband omnidirectional cross‐plate monopole antenna
Authors: Wong Kin‐Lu , Wu Chih‐Hsien , Chang Fa‐Shian
Published: February 2005

A novel cross‐plate monopole antenna formed by two orthogonal step‐shaped metal plates is presented. The antenna occupies a compact cross‐sectional area and yet provides a wide operating bandwidth (lower‐to‐upper‐edge frequency ratio larger than 1:6) with omnidirectional or near‐omnidirectional radiation patterns. Details of the proposed antenna are described, and a prototype is constructed and studied. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 492–494, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20676
Design and performance of a novel broadband uniplanar balanced subharmonic mixer
Authors: Choi Sung Tae , Kim Yong Hoon
Published: February 2005

A novel wideband uniplanar balanced subharmonic mixer is proposed and demonstrated. The mixer is based on the broadband tapered coplanar‐waveguide (CPW) DC‐block filter, and the in‐phase and out‐of‐phase T‐junctions are interconnected through a pair of quarter‐wavelength slotlines. The fabricated subharmonic mixer has an RF bandwidth of more than one octave from 12 to 28 GHz with a conversion loss ranging from 8.5 to 12.5 dB for LO signals from 6.1 to 14.1 GHz with a power level of 9.5 dBm. The measured LO‐to‐RF, LO‐to‐IF, and RF‐to‐IF isolations are better than 15.5, 34, and 26.6 dB, respectively. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 508–510, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20681
Application of left‐handed media in distributed amplifiers
Authors: Eccleston K. W.
Published: February 2005

A combination of left‐handed and conventional right‐handed media transmission lines is used in place of conventional right‐handed media transmission lines in a single‐ended dual‐fed distributed amplifier. This approach results in increased bandwidth and circuit size reduction. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 527–530, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20686
A new element design for an axis‐independent, tunable, negative‐permeability artificial meta‐material
Authors: Ouyang Gong , Jandhyala Vikram
Published: February 2005

A new meta‐material element that can realize axis‐independent negative permeability is proposed and analyzed. The element is constructed as an intuitive 3D analog of the well‐known flat split‐ring structure (SRR). Unlike the SRR, the proposed element exhibits negative permeability for three preferred coordinate axes, and therefore enables meta‐material applications such as focusing and efficient radiation from electrically small structures in multiple directions within the same structure. In addition, it is shown that the addition of lumped‐circuit components to the element enables both tunability and functionality at very small sizes, far from the intrinsic resonance of the structure itself. The designed element is then simulated rigorously using a previously reported integral‐equation technique that includes the ability to model linear and nonlinear tuning elements attached to the meta‐material elements. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 530–533, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20687
26‐GHz pHEMT VCO MMIC
Authors: Wen Yu , Xiaowei Sun , Rong Qian , Yimen Zhang
Published: February 2005

A wide tuning range and high‐output‐power 26‐GHz pHEMT voltage‐controlled oscillator (VCO) MMIC based on a 0.25‐μm GaAs pHEMT process is presented. The active‐biasing technique has been adopted to reduce the chip size and to increase the bandwidth of operation, and maximum negative resistance has been chosen in order to obtain high output power. The measured (with the chip in a test fixture) oscillating frequency is 25.7 ± 0.7 GHz and the output power is 11 ± 1 dBm (with test fixture loss considered). The fabricated VCO MMIC chip size is 1.5 × 1.0 mm. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 550–552, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20694
Hyper‐CK‐emia as the sole manifestation of myotonic dystrophy type 2
Authors: Merlini Luciano , Sabatelli Patrizia , Columbaro Marta , Bonifazi Emanuela , Pisani Valerio , Massa Roberto , Novelli Giuseppe
Published: February 2005

A 49‐year‐old man had an 8‐year history of persistent, isolated elevation of serum creatine kinase (hyper‐CK‐emia) without muscle symptoms, and no electromyographic evidence of myotonia; his muscle biopsy showed features reminiscent of myotonic dystrophy (DM), with morphometric findings consistent with those described in DM type 2 (DM2). Genetic studies excluded mutations in the DM type 1 (DM1) gene, but revealed a CCTG repeat expansion in the ZNF9 gene, which is associated with DM2. Our data suggest that in asymptomatic patients with persistent hyper‐CK‐emia, DM2 should be considered in the differential diagnosis. Muscle Nerve, 2005
Synthesis of long‐chain‐branched polyethylene by ethylene homopolymerization with a novel nickel(II) α‐diimine catalyst
Authors: Zou Hao , Zhu Fang Ming , Wu Qing , Ai Jiao Yan , Lin Shang An
Published: February 2005

Long‐chain‐branched polyethylene with a broad or bimodal molecular weight distribution was synthesized by ethylene homopolymerization via a novel nickel(II) α‐diimine complex of 2,3‐bis(2‐phenylphenyl)butane diimine nickel dibromide ({[2‐C6H4(C6H5)]NC(CH3)C(CH3)N[2‐C6H4(C6H5)]}NiBr2) that possessed two stereoisomers in the presence of modified methylaluminoxane. The influences of the polymerization conditions, including the temperature and Al/Ni molar ratio, on the catalytic activity, molecular weight and molecular weight distribution, degree of branching, and branch length of polyethylene, were investigated. The resultant products were confirmed by gel permeation chromatography, gas chromatography/mass spectrometry, and 13C NMR characterization to be composed of higher molecular weight polyethylene with only isolated long‐branched chains (longer than six carbons) or with methyl pendant groups and oligomers of linear α‐olefins. The long‐chain‐branched polyethylene was formed mainly through the copolymerization of ethylene growing chains and macromonomers of α‐olefins. The presence of methyl pendant groups in the polyethylene main chain implied a 2,1‐insertion of the macromonomers into [Ni]H active species. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1325–1330, 2005
Polyamide–polyester multiblock copolymers by chain‐coupling reactions of carboxy‐terminated polymers with phenylene and pyridylene bisoxazolines
Authors: Néry Laurent , Lefebvre Hervé , Fradet Alain
Published: February 2005

Polyamide–polyester multiblock copolymers were synthesized through the reaction of α,ω‐dicarboxy polyamides and polyesters with various arylene bis(2‐oxazoline)s. 2,2′‐(2,6‐Pyridylene)bis(2‐oxazoline) was very reactive and yielded multiblock copolymers with number‐average molar masses ranging from 15,000 to 25,000 after 30 min of reaction in the bulk at 200 °C. The molar masses and thermal properties of the resulting random multiblock copolymers (glass‐transition temperature, melting temperature, and melting enthalpy) were close to those of their alternating homologues prepared by conventional polycondensation between diamino polyamides and dicarboxy polyesters. This showed that the presence of coupling agent moieties in the polymer chains did not exert a significant influence on the block copolymer morphology. The chain‐coupling method showed several advantages over conventional polycondensation: a much shorter reaction time, a lower temperature, no byproducts, and easy control of the final copolymer properties through the mass ratio of the starting oligomers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1331–1341, 2005
The extent of myocardial damage assessed by contrast‐enhanced MRI is a major determinant of N‐BNP concentration after myocardial infarction
Authors: Cochet Alexandre , Zeller Marianne , Cottin Yves , Robert‐Valla Clothilde , Lalande Alain , L'Huilllier Isabelle , Comte Alexandre , Walker Paul M. , Desgres Jean , Wolf Jean‐Eric , Brunotte François
Published: February 2005

Aims:

To evaluate the relationship between N‐terminal Pro‐Brain Natriuretic Peptide (N‐BNP) level and contrast‐enhanced MRI in patients after acute myocardial infarction (MI).

Methods:

Eighty‐two patients were studied. Venous blood samples were obtained 3 days after MI and MRI was performed from 2 to 7 days after MI, with determination of left ventricular function and acquisition of perfusion data after injection of gadolinium‐DTPA. First‐pass images (FPI) and Delayed contrast‐enhanced (CE) images were analyzed using a 17‐segment model, and the extent of transmurality was determined by a visual score.

Results:

Univariate analysis showed that age (P<0.001), sex (P<0.02), Left Ventricular Ejection Fraction (LVEF) <45% (P<0.002), creatinine (P<0.05) and delayed CE‐MR images (P<0.006) were predictors of a supramedian N‐BNP level. FPI was not a predictor in this univariate analysis (P<0.078). In a multivariate model, only age, LVEF <45% and delayed CE‐MRI were associated with an increased N‐BNP level.

Conclusion:

After MI, high N‐BNP levels are dependent on the LVEF but also on the myocardial infarct size derived from the delayed CE‐MR images.
Relation of sex, age and concomitant diseases to drug prescription for heart failure in primary care in Europe
Authors: Muntwyler Jorg , Cohen‐Solal Alain , Freemantle Nick , Eastaugh Joanne , Cleland John G. , Follath Ferenc
Published: February 2005

Aim:

To study the role of sex, age and concomitant diseases for prescription of cardiovascular drugs among patients with heart failure cared for in the community.

Methods and Results:

In 15 European countries, a survey was conducted during 1999 and 2000 among 1363 primary care physicians who included 8256 patients with symptoms of heart failure. Predictors of drug prescription were assessed with multivariate logistic regression. Overall prescription rates for ACE‐inhibitors/angiotensin receptor blockers (ACE‐I/ARB), beta‐blockers, digitalis, diuretics and oral anticoagulants were 69%, 30%, 41%, 75% and 18%. Women had no reduced likelihood to receive ACE‐I/ARB and beta‐blockers (odds ratio [OR]=0.96 [95% CI 0.87–1.06] and 1.02 [0.92–1.13], respectively), but prescription of oral anticoagulants was decreased (OR=0.74, 95% CI 0.65–0.84). Compared to patients <65 years of age, ACE‐I/ARB prescription did not materially decline up to 75–85 years (R=0.91, 95% CI 0.81–1.04), whereas beta‐blocker prescription was already significantly decreased in this age category (OR=0.49, 95% CI 0.43–0.56). There was no general under‐prescription of evidence‐based cardiovascular drugs in patients with concomitant diseases.

Conclusions:

Among heart failure patients cared for in the community advanced age strongly predicts decreased prescription of beta‐blockers. Female sex and comorbidity is not associated with a consistent underutilization of evidence‐based cardiovascular drugs.
Guiding and optimization of resynchronization therapy with dynamic three‐dimensional echocardiography and segmental volume–time curves: a feasibility study
Authors: Krenning Boudewijn J. , Szili‐Torok Tamas , Voormolen Marco M. , Theuns Dominic A.M.J. , Jordaens Luc J. , Lancée Charles T. , de Jong Nico , van der Steen Anton F.W. , Ten Cate Folkert J. , Roelandt Jos R.T.C.
Published: February 2005

Objective:

To assess a new approach for guiding and hemodynamic optimization of resynchronization therapy, using three‐dimensional (3D) transthoracic echocardiography.

Background:

Resynchronization therapy for heart failure provides the greatest hemodynamic benefit when applied to the most delayed left ventricular (LV) site. Currently, the ideal LV pacing site is selected according to acute invasive hemodynamic assessment and/or tissue Doppler imaging.

Methods:

A total of 16 patients with advanced heart failure and an implanted biventricular pacemaker were included in this study. Transthoracic apical LV images at equidistant intervals were obtained using a prototype, fast‐rotating second harmonic transducer to reconstruct 3D LV datasets during sinus rhythm (SR), right ventricular (RV) apical and biventricular pacing mode. A semi‐automated contour analysis system (4D LV analysis, TomTec, Germany) was used for segmental wall motion analysis and identification of the most delayed contracting segment and calculation of global LV function.

Results:

Data acquisition duration was 10 s and analyzable 3D images were obtained in 12 patients. Of these patients, data during SR were available in 9 and during biventricular pacing in 11. The greatest contraction delay during SR was found in the anterior and antero‐septal segments in five of nine patients. Biventricular pacing resulted in reduction of the contraction delay in seven of eight patients. The global LV function did not change significantly.

Conclusion:

3D echocardiography with appropriate analytic software allows detection of the most delayed LV contracting segment and can be used to select the optimal pacing site during resynchronization therapy.
WRKY group IId transcription factors interact with calmodulin
Authors: Park Chan Young , Lee Ju Huck , Yoo Jae Hyuk , Moon Byeong Cheol , Choi Man Soo , Kang Yun Hwan , Lee Sang Min , Kim Ho Soo , Kang Kyu Young , Chung Woo Sik , Lim Chae Oh , Cho Moo Je
Published: February 2005

Calmodulin (CaM) is a ubiquitous Ca2+‐binding protein known to regulate diverse cellular functions by modulating the activity of various target proteins. We isolated a cDNA encoding AtWRKY7, a novel CaM‐binding transcription factor, from an Arabidopsis expression library with horseradish peroxidase‐conjugated CaM. CaM binds specifically to the Ca2+‐dependent CaM‐binding domain (CaMBD) of AtWRKY7, as shown by site‐directed mutagenesis, a gel mobility shift assay, a split‐ubiquitin assay, and a competition assay using a Ca2+/CaM‐dependent enzyme. Furthermore, we show that the CaMBD of AtWRKY7 is a conserved structural motif (C‐motif) found in group IId of the WRKY protein family.
Histone deacetylase inhibitor BL1521 induces a G1‐phase arrest in neuroblastoma cells through altered expression of cell cycle proteins
Authors: Ouwehand Krista , de Ruijter Annemieke J.M. , van Bree Chris , Caron Huib N. , van Kuilenburg André B.P.
Published: February 2005

Histone deacetylase inhibitors (HDACi) have been discovered as potential drugs for cancer treatment. The effect of BL1521, a novel HDACi, on the cell cycle distribution and the induction of apoptosis was investigated in a panel of MYCN single copy and MYCN amplified neuroblastoma cell lines. BL1521 arrested neuroblastoma cells in the G1 phase and induced up to 30% apoptosis. Downregulation of CDK4, upregulation of p21WAF1/CIP1 and an increase of hypophosphorylated retinoblastoma protein were observed, indicating a possible mechanism for the cell‐cycle arrest. BL1521 also induced downregulation of p27, which may underlie the observed induction of apoptosis.
A System for Dispensing Sub-Milligram Doses of Active Pharmaceutical Powders for Early Stage Solubility Assays
Authors: Kane Nathan R. , Broce Brad , Gonzalez-Zugasti Javier , Lewis Wendy Pryce , LeQuesne Martin , Lemmo Anthony V.
Published: February 2005

At early stages of drug development, the solubility of compounds is an important screening criterion. However, because scientists lack the automated tools needed to perform comprehensive early stage solubility studies, they are only able to perform a small number of experiments by hand, thus exploring only a fraction of the potential formulation design space. To allow a larger formulation design space to be explored at relatively early stages of pharmaceutical development (when 100 mg of a prototype compound is available), TransForm has created the AquaSFinX™ and SFinX™ micro-solubility platforms. In this article, a novel solid deposition system is described which is an enabling component of TransForm's solubility platforms. Given 100 mg of a starting material, the deposition system can dispense over six hundred 50-μg plugs of powder into 384-well or 1,536-well plates with well openings as small as 1.5 mm. Currently no commercial powder deposition system can provide this functionality. Including the time required to characterize and run the system, the dispense times range from around 2 minutes per dose for small runs involving 100 mg of starting material, to 18 seconds per dose for larger runs involving a gram or more of starting material.
Hybrid Valve Structure for High-Throughput, Low-Volume Liquid-Handling Applications
Authors: Doktycz Mitchel J. , Johnson James E. , Cornett Mary J.
Published: February 2005

A hybrid valve that integrates precision microfluidics for fluid routing, high-speed valving for fluid switching, and reagent-jetting devices for metering the fluid dispenses is described. The hybrid valve enables parallel switching between aspiration and dispense modes for multiple sample streams. This unique valve structure addresses many of the concerns with handling microscale volumes, including efficient use of samples, degradation of ink jet valves and speed of operation. A broad range of volumes can be manipulated with excellent reproducibility. The hybrid valve can be configured for a variety of applications. Pick-and-place aspiration and dispensing of unique reagents and rapid dispensing of a common reagent are possible. Together these features lead to higher-speed transfer of smaller volumes of reagent.
Mosquito®: An Accurate Nanoliter Dispensing Technology
Authors: Jenkins Joby , Cook Matthew
Published: February 2005

Mosquito® from TTP LabTech Ltd. is an innovative nanoliter dispenser that combines the liquid transfer capability of a fixed head pipette with the elimination of cross-contamination, using disposable tips. For many applications required in genomics, proteomics and drug discovery, Mosquito can reduce assay cost by minimizing reagent and sample usage.
Role of topography in facilitating coexistence of trees and grasses within savannas
Authors: Kim Yeonjoo , Eltahir Elfatih A. B.
Published: February 2005

The factors and processes that may explain the observed coexistence of trees and grasses in savannas are not well understood. Here we propose a new hypothesis that addresses this issue. We hypothesize that “variations in elevation at relatively short horizontal scales of ∼1 km force similar variations in soil moisture and thus create significantly different hydrologic niches within any large area. Under water‐limited conditions the relatively wet valleys favor trees, while the relatively dry hills favor grasses. This coexistence of trees and grasses is only possible for a window of climatic conditions that are characteristic of savannas.” To test this hypothesis, numerical simulations are performed for the region of West Africa using a model that simulates vegetation dynamics, the Integrated Biosphere Simulator (IBIS), and a distributed hydrologic model, Systeme Hydrologique Europeen (SHE). IBIS is modified to include the groundwater table (GWT) as a lower boundary. The spatial distribution of GWT is simulated by SHE. At 9°N the model simulates trees even when the GWT is assumed to be infinitely deep; at 13°N the model simulates grasses even when the capillary fringe of the GWT reaches the surface. However, for the transitional climate, at 11°N, trees are simulated when the GWT is at ∼2.5 m from the surface, but grasses are simulated when the GWT is deeper than 2.5 m. These results suggest that the variability of soil moisture forced by topography can be a determinant factor of vegetation distribution within savannas. Furthermore, they confirm that this role of topography can be significant only in a certain climatic window characteristic of savannas.
An aggregate drought index: Assessing drought severity based on fluctuations in the hydrologic cycle and surface water storage
Authors: Keyantash John A. , Dracup John A.
Published: February 2005

An aggregate drought index (ADI) has been developed, and evaluated within three diverse climate divisions in California. The ADI comprehensively considers all physical forms of drought (meteorological, hydrological, and agricultural) through selection of variables that are related to each drought type. Water stored in large surface water reservoirs was also included. Hydroclimatic monthly data for each climate division underwent correlation‐based principal component analysis (PCA), and the first principal component was deseasonalized to arrive at a single ADI value for each month. ADI time series were compared against the Palmer Drought Severity Index (PDSI) to describe two important droughts in California, the 1976–1977 and 1987–1992 events, from a hydroclimatological perspective. The ADI methodology provides a clear, objective approach for describing the intensity of drought and can be readily adapted to characterize drought on an operational basis.
Groundwater management institutions to protect riparian habitat
Authors: Orr Patricia , Colby Bonnie
Published: February 2005

Groundwater pumping affects riparian habitat when it causes the water table to drop beyond the reach of riparian plants. Riparian habitat provides services that are not directly traded in markets, as is the case with many environmental amenities. There is no direct market where one may buy or sell the mix of services provided by a riparian corridor. The objective of this article is to review groundwater management mechanisms and assess their strengths and weaknesses for preserving the ecological integrity of riparian areas threatened by groundwater pumping. Policy instruments available to those concerned with the effects of groundwater pumping on riparian areas fall into three broad categories: (1) command and control (CAC), (2) incentive‐based economic instruments, and (3) cooperative/suasive strategies. The case of the San Pedro River illustrates multiple and overlapping strategies applied in an ongoing attempt to reverse accumulating damage to a riparian ecosystem. Policy makers in the United States can choose among a broad menu of policy options to protect riparian habitat from groundwater pumping. They can capitalize on the clarity of command‐and‐control strategies, the flexibility and less obtrusive nature of incentive‐based economic strategies, and the benefits that collaborative efforts can bring in the form of mutual consideration. While collaborative problem solving and market‐based instruments are important policy tools, experience indicates that a well‐formulated regulatory structure to limit regional groundwater pumping is an essential component of an effective riparian protection strategy.
Physiographical space‐based kriging for regional flood frequency estimation at ungauged sites
Authors: Chokmani K. , Ouarda T. B. M. J.
Published: February 2005

A physiographical space‐based kriging method is proposed for regional flood frequency estimation. The methodology relies on the construction of a continuous physiographical space using physiographical and meteorological characteristics of gauging stations and the use of multivariate analysis techniques. Two multivariate analysis methods were tested: canonical correlation analysis (CCA) and principal components analysis. Ordinary kriging, a geostatistical technique, was then used to interpolate flow quantiles through the physiographical space. Data from 151 gauging stations across the southern part of the province of Quebec, Canada, were used to illustrate this approach. In order to evaluate the performance of the proposed method, two validation techniques, cross validation and split‐sample validation, were applied to estimate flood quantiles corresponding to the 10, 50, and 100 year return periods. Results of the proposed method were compared to those produced by a traditional regional estimation method using the canonical correlation analysis. The proposed method yielded satisfactory results. It allowed, for instance, for estimating the 10 year return period specific flow with a coefficient of determination of up to 0.78. However, this performance decreases with the increase in the quantile return period. Results also showed that the proposed method works better when the physiographical space is defined using canonical correlation analysis. It is shown that kriging in the CCA physiographical space yields results as precise as the traditional estimation method, with a fraction of the effort and the computation time.
Interdecadal Arctic Oscillation in twentieth century climate simulations viewed as internal variability and response to external forcing
Authors: Yukimoto Seiji , Kodera Kunihiko
Published: February 2005

Interdecadal variations similar to the Arctic Oscillation (AO) are investigated for internal variability (INTV) and response to external forcing (REXT) in an ensemble simulation of twentieth century climate. The significant trend in REXT implies that a sizeable part of the observed AO trend in recent decades can also be attributed to anthropogenic forcing. INTV is characterized by a barotropic dipole of zonal wind anomalies and associated wave propagation, suggesting a mechanism similar to the month‐to‐month AO. Its thermal structure can be attributed to dynamic processes. REXT exhibits a thermal structure that can be explained by responses to the forcing due to increased greenhouse gases. A westerly wind anomaly in the stratosphere as a thermal response corresponds to anomalies in wave propagation and meridional circulation that are similar to INTV, which may induce the AO‐like annular pattern.
Regional distribution of absorbing efficiency of dust aerosols over India and adjacent continents inferred using satellite remote sensing
Authors: Deepshikha S. , Satheesh S. K. , Srinivasan J.
Published: February 2005

The investigations as part of ACE‐Asia have demonstrated that dust we observe may not be just dust, but it may be dust mixed with other aerosols. Consequently dust radiative forcing (even its sign) has a large uncertainty due to the lack of database on complex spatial and temporal pattern of dust radiative properties. To accurately predict the impact of dust aerosols on climate the spatial and temporal distribution of dust radiative properties is essential. Here, we propose a method to infer regional distribution of dust radiative properties using satellite remote sensing (infrared and visible/UV channels) and demonstrate its application. Our studies show that dust in desert areas is low absorbing type while those transported to other locations having anthropogenic activities are significantly more absorbing than pure dust aerosols. This provides a strong evidence for the possible mixing of dust aerosols with other aerosols such as black carbon.
In situ airborne measurements of aerosol optical properties during photochemical pollution events
Authors: Mallet M. , Van Dingenen R. , Roger J. C. , Despiau S. , Cachier H.
Published: February 2005

Dry aerosol optical properties (scattering, absorbing coefficients, and single scattering albedo) were derived from in situ airborne measurements during two photochemical pollution events (25 and 26 June) observed during the Experience sur Site pour Contraindre les Modeles de Pollution atmospherique et de Transport d'Emissions (ESCOMPTE) experiment. Two flights were carried out during daytime (one during the morning and one at noon) over a domain, allowing the investigation of how an air pollution event affects the particle optical properties. Both horizontal distribution and vertical profiles are presented. Results from the horizontal mapping show that plumes of enhanced scattering and absorption are formed in the planetary boundary layer (PBL) during the day in the sea breeze–driven outflow of the coastal urban‐industrial area of Marseille–Fos de Berre. The domain‐averaged scattering coefficient (at 550 nm) over land σs changes from 35 (28) Mm−1 during land breeze to 63 (43) Mm−1 during sea breeze on 25 June (26 June), with local maxima reaching > 100 Mm−1. The increase in the scattering coefficient is associated with new particle formation, indicative of secondary aerosol formation. Simultaneously, the domain‐averaged absorption coefficient increases from 5.6 (3.4) Mm−1 to 9.3 (8.0) Mm−1. The pollution plume leads to strong gradients in the single scattering albedo ωo over the domain studied, with local values as low as 0.73 observed inside the pollution plume. The role of photochemistry and secondary aerosol formation during the 25 June case is shown to increase ωo and to make the aerosol more ‘reflecting’ while the plume moves away from the sources. The lower photochemical activity, observed in the 26 June case, induces a relatively higher contribution of black carbon, making the aerosol more absorbing. Results from vertical profiles at a single near‐urban location in the domain indicate that the changes in optical properties happen almost entirely within the PBL. No significant variation of σs, σa, and ωo is observed in the upper layer (1–3 km), where the aerosol optical properties are considered to be well mixed.
Large‐scale sandbox experiment on longitudinal effective dispersion in heterogeneous porous media
Authors: Jose Surabhin C. , Rahman M. Arifur , Cirpka Olaf A.
Published: February 2005

In heterogeneous media the breakthrough curves observed at single points may differ significantly from those integrated over a control plane. While standard macrodispersion describes the spread of concentration averaged over the entire cross section, effective dispersion quantifies the average spread in the locally observed breakthrough curves. We perform a conservative tracer test in a 14‐m‐long sandbox filled heterogeneously with four types of silica sand. The filling resembles natural heterogeneities including the distribution of facies and micro‐structures within the various sand types. We use fluorescein as tracer, which we measure at 126 measurement points directly within the porous medium and at 19 levels in the outlet of the domain. We use fiber‐optic probes with a point‐like measurement tip for fluorescence intensity measurements. From the second central temporal moments of the locally obtained breakthrough curves we compute apparent effective dispersion coefficients, and from the average over all probes within a measurement plane we derive apparent macrodispersion coefficients. The effective dispersion coefficient is about two thirds of the macrodispersion coefficient. Considering the typical length scales of the heterogeneities, the experimental findings are qualitatively in agreement with linear stochastic theory.
Effect of Cholera Toxin and Cyclic Adenosine Monophosphate on Fluid–Phase Endocytosis, Distribution, and Trafficking of Endosomes in Rat Liver
Authors: Van Dyke Rebecca W.
Published: February 2005

In prior studies, we showed that cholera (CTX) and pertussis toxins (PTX) increase rat liver endosome acidification. This study was performed to characterize the effects of these toxins and cyclic adenosine monophosphate (cAMP) on endosome ion transport, fluid–phase endocytosis (FPE), and endosome trafficking in liver. In control liver, more mature populations of endosomes acidified progressively more slowly, but both toxins and cAMP caused retention of an early endosome acidification profile in maturing endosomes. CTX caused a density shift in endosomes, and all agents increased net FPE at time points from 5 to 60 minutes. By confocal microscopy, fluorescent dextrans first appeared in small vesicles at the hepatocyte sinusoidal membrane and trafficked rapidly to the pericanalicular area, near lysosomes and the trans–Golgi network (TGN). Prolonged exposure to these agents caused redistribution of many labeled vesicles to the perinuclear region, colocalized with markers of both early (EEA1 and transferrin receptor) and late (LAMP1) endosomes. We conclude that cAMP is the common agent that disrupted normal maturation and trafficking of endosomes and increased net FPE, in part via decreased diacytosis.
Risk Factors for Recurring Hepatocellular Carcinoma Differ According to Infected Hepatitis Virus—An Analysis of 236 Consecutive Patients With A Single Lesion
Authors: Koike Yukihiro , Shiratori Yasushi , Sato Shinpei , Obi Shuntaro , Teratani Takuma , Imamura Masatoshi , Hamamura Keisuke , Imai Yasuo , Yoshida Haruhiko , Shiina Shuichiro , Omata Masao
Published: February 2005

Patients with hepatocellular carcinoma (HCC) frequently experience intrahepatic HCC recurrence even after complete ablation of primary lesions. Because the oncogenic process may be different for hepatitis B viral (B–viral) and hepatitis C viral (C–viral) HCC, the present study was conducted to elucidate the factors contributing to HCC recurrence with respect to the infected hepatitis virus. Two hundred thirty–six patients with a single HCC lesion who underwent complete ablation of the tumor by PEIT and/or PMCT or surgical resection at Tokyo University and its affiliated hospitals from 1993 to 1997 were enrolled. The patients were classified into 3 groups: the B–viral group, C–viral group, and NBNC group. After complete removal of tumors, the patients were followed for a mean period of 39 months. The factors contributing to HCC recurrence were analyzed by univariate and multivariate analysis using the Cox proportional hazard model. The rate of intrahepatic recurrence in enrolled patients at 1, 3, and 5 years was 19%, 50%, and 64%, respectively. The intrahepatic recurrence rate in C–viral and B–viral HCC was higher than that in the NBNC–related HCC. Fibrosis staging, pathological grading of HCC, and serum AFP levels were significantly linked to intrahepatic recurrence by univariate analysis, and fibrosis staging was strongest in the multivariate analysis for C–viral HCC (P = .004). In contrast, fibrosis staging did not affect the recurrence in B–viral (P = .51) and NBNC–related (P = .77) HCC. Risk factors for HCC recurrence differed according to the infected viral state.
Tumor Necrosis Factor α Prevents Tumor Necrosis Factor Receptor—Mediated Mouse Hepatocyte Apoptosis, But Not Fas–Mediated Apoptosis: Role of Nuclear Factor–κB
Authors: Nagaki Masahito , Naiki Takafumi , Brenner David A. , Osawa Yosuke , Imose Motoaki , Hayashi Hideki , Banno Yoshiko , Nakashima Shigeru , Moriwaki Hisataka
Published: February 2005

Tumor necrosis factor α (TNF–α) binding to the TNF receptor (TNFR) initiates apoptosis and simultaneously activates the transcription factor, nuclear factor–κB (NF–κB), which suppresses apoptosis by an unknown mechanism. Pretreatment with TNF–α or interleukin–1β (IL–1β), which activated NF–κB in the liver, dramatically prevented TNF–α–induced liver–cell apoptosis in D–galactosamine (GalN)–sensitized mice, but not anti–Fas antibody–induced hepatotoxicity. This protective effect of TNF–α continued for 5 hours after TNF–α administration, a time course similar to that found in NF–κB activation after TNF–α administration. In mice treated with adenoviruses expressing a mutant form of IκB, the antiapoptotic effect of TNF–α was inhibited in part. Prior TNF–α administration was not found to block the activation of caspase–8, although caspase–3 was inhibited in mice treated with TNF–α plus GalN/TNF–α compared with mice treated with GalN/TNF–α. These results indicate that TNFR and Fas independently regulate murine apoptotic liver failure, and that a rapid defense mechanism induced by the activation of NF–κB blocks death–signaling at the initiation stage of hepatic apoptosis mediated by TNFR, probably downstream of caspase–8, but not by Fas.
Mutations in the E2–Pephd and Ns5a Region of Hepatitis C Virus Type 1 and the Dynamics of Hepatitis C Viremia Decline During Interferon Alfa Treatment
Authors: Berg Thomas , Marques Andreas Mas , Höhne Marina , Wiedenmann Bertram , Hopf Uwe , Schreier Eckart
Published: February 2005

Both a double–stranded RNA–dependent protein kinase (PKR)–phosphorylation homology domain (PePHD) within the E2 protein and a PKR–binding domain within the nonstructural 5A (NS5A) protein of hepatitis C virus (HCV) genotype 1 isolates inhibit the function of the interferon alfa (IFN–α)–induced antiviral effector protein PKRin vitro. We investigated whether the mutational pattern of the E2 region (codons 618–681, including PePHD) of 81 HCV genotype 1–infected patients (HCV–1b [n = 54], HCV–1a [n = 27]) influences the response to IFN–α. Initial viral decline (ΔHCV RNA) was determined at week 1 hereby covering the effector reactions of IFN–α–mediated first phase and the immune–mediated second phase. ΔHCV RNA less than 50% (group 1); ΔHCV RNA greater than 50% but less than 90% (group 2); and ΔHCV RNA ≥90% (group 3) were differentiated. The PePHD region was highly conserved; the few mutations (5 patients) did not correlate with ΔHCV RNA or sustained virologic response to IFN–α. Within the flanking regions before and after PePHD (codons 618–681) 72 of 81 patients (89%) had 2.6 ± 0.17 mutations (median, 3; range, 1–8) that did not correlate with treatment response. Sequence analysis of the NS5A protein (codons 2,209–2,274, including interferon sensitivity determining region [ISDR]) in 39 of 81 patients showed a higher mean number of mutations in the ISDR (codons 2,209–2,248) in groups 2 (1.28 ± 0.43 [n = 18]) and 3 (1.89 ± 0.54 [n = 9]) than in group 1 (0.67 ± 0.19 [n = 12];P= .049 group 1 vs. 3) and a mutant type ISDR (e.g., ≥4 mutations) was significantly more frequent in sustained virologic responders than in nonresponders or relapsers (2 of 4 [50%] vs. 2 of 35 [6%];P= .045). Thus, NS5A appears to be functionally relevant in IFN–α–induced effector reactions.
Local correlation measures in atomic systems
Authors: Guevara Nicolais L. , Sagar Robin P. , Esquivel Rodolfo O.
Published: February 2005

The phenomenon of electron correlation in atomic systems is examined and compared from the statistical, information theoretic, and energetic perspectives. Local correlation measures, based on the correlation coefficient, information entropies, and idempotency measure, are compared to the correlation energy density. Analysis of these local measures reveals that the chemically significant valence region is responsible for the behavior of their respective global measures in contrast to the correlation energy density which has large contributions to the correlation energy from both the core and valence regions. These results emphasize the difference in the mechanisms inherent in the different perspectives, the similarity between the statistical, information entropic, and idempotency views, and provides further evidence for the use of information theoretic based quantities in studies of electron correlation.
Effects of colloid polydispersity on the phase behavior of colloid-polymer mixtures
Authors: Fasolo Moreno , Sollich Peter
Published: February 2005

We study theoretically the equilibrium phase behavior of a mixture of polydisperse hard-sphere colloids and monodisperse polymers, modeled using the Asakura–Oosawa model [S. Asakura and F. Oosawa, J. Chem. Phys. 22, 1255 (1954)] within the free volume approximation of H. N. W. Lekkerkerker, W. C. K. Poon, P. N. Pusey, A. Stroobants, and P. B. Warren [Europhys. Lett. 20, 559 (1992)]. We compute full phase diagrams in the plane of colloid and polymer volume fractions, using the moment free energy method. The intricate features of phase separation in pure polydisperse colloids combine with the appearance of polymer-induced gas-liquid coexistence to give a rich variety of phase diagram topologies as the polymer-colloid size ratio ξ and the colloid polydispersity δ are varied. Quantitatively, we find that polydispersity disfavors fluid-solid against gas-liquid separation, causing a substantial lowering of the threshold value ξc above which stable two-phase gas-liquid coexistence appears. Phase splits involving two or more solids can occur already at low colloid concentration, where they may be kinetically accessible. We also analyze the strength of colloidal size fractionation. When a solid phase separates from a fluid, its polydispersity is reduced most strongly if the phase separation takes place at low colloid concentration and high polymer concentration, in agreement with experimental observations. For fractionation in gas-liquid coexistence we likewise find good agreement with experiment, as well as with perturbative theories for near-monodisperse systems.