bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial bias in field‐estimated unsaturated hydraulic properties
Authors: Holt Robert M. , Wilson John L. , Glass Robert J.
Published: December 2002

We use a Monte Carlo approach to explore the potential impact of observation and inversion model errors on the spatial statistics of field‐estimated unsaturated hydraulic properties. For this analysis we simulate tension infiltrometer measurements in a series of idealized realities, each consisting of spatially correlated random property fields. We consider only simple measurement errors that can be easily modeled. We show that estimated hydraulic properties are strongly biased by small, simple observation and inversion model errors. This bias can lead to order‐of‐magnitude errors in spatial statistics and artificial cross correlation between measured properties. The magnitude of bias varies with the true mean of the property field, the type of error considered, and the type of spatial statistic. We find no unique indicators of bias as property values may appear reasonable and spatial statistics may look realistic. Our results suggest new concerns for geostatisticians, stochastic modelers, and unsaturated zone practitioners who are unaware of the potential impact of spatial bias in field‐estimated properties.
Electro-Optic Measurement Using High-Quality 4-dimethylamino-N-methyl-4-stilbazolium Tosylate (DAST) Crystal
Authors: Adachi Hiroaki , Nagaoka Kazuaki , Tsunesada Fumi , Yoshimura Masashi , Mori Yusuke , Sasaki Takatomo , Sasaki Ai-ichiro , Nagatsuma Tadao , Ochiai Yuta , Fukasaku Noboru
Published: December 2002

We evaluated the electro-optic (EO) properties of 4-dimethylamino-N-methyl-4-stilbazolium tosylate (DAST) crystals by external EO probing. The EO signal power obtained from the DAST crystal increased by 8 dB compared to that obtained from the KTiOPO4 (KTP) crystal at 90 kHz. The larger EO signal power obtained from the DAST crystal was almost constant at low frequencies (30 Hz to 90 kHz), whereas the KTP crystal could not respond below 180 Hz. We also observed excellent signals at all measured points due to the high crystallinity of the crystal grown by the slope nucleation method (SNM).
Activity of the A3 adenosine receptor gene promoter in transgenic mice: characterization of previously unidentified sites of expression
Authors: Yaar Ron , Lamperti Edward D , Toselli Paul A , Ravid Katya
Published: December 2002

Sites of A3 adenosine receptor gene expression have not been fully explored nor has this gene's promoter activity been confirmed in vivo. Transgenic mice were generated in which 2.3 kb upstream of the transcriptional start site of the mouse A3 adenosine receptor was coupled to a β‐galactosidase reporter gene. Selective transgene expression was detected in testis and brain as well as at other sites in which A3 adenosine receptor message has not been previously reported, including retinal ganglion cells and smooth muscle cells of the cerebrospinal vasculature. Our study suggests that this promoter may be useful in the selective targeting of gene expression to specific tissues.
Properties of the chaperonin complex from the halophilic archaeon Haloferax volcanii
Authors: Large Andrew T , Kovacs Eszter , Lund Peter A
Published: December 2002

The halophilic archaeon Haloferax volcanii has three genes encoding type II chaperonins, named cct1, cct2 and cct3. We show here that the three CCT proteins are all expressed but not to the same level. All three proteins are further induced on heat shock. The CCT proteins were purified by ammonium sulphate precipitation, sucrose gradient centrifugation and hydrophobic interaction chromatography. This procedure yields a high molecular mass complex (or complexes). The complex has ATPase activity, which is magnesium dependent, low salt‐sensitive and stable to at least 75°C. Activity requires high levels of potassium ions and was reduced in the presence of an increasing concentration of sodium ions.
Molecular characterization of a two‐domain form of the neuronal voltage‐gated P/Q‐type calcium channel α12.1 subunit
Authors: Arikkath Jyothi , Felix Ricardo , Ahern Christopher , Chen Chien-Chang , Mori Yasuo , Song Inseon , Shin Hee-Sup , Coronado Roberto , Campbell Kevin P
Published: December 2002

We characterized the neuronal two‐domain (95kD‐α12.1) form of the α12.1 subunit of the voltage‐gated calcium channels using genetic and molecular analysis. The 95kD‐α12.1 is absent in neuronal preparations from CACNA1A null mouse demonstrating that α12.1 and 95kD‐α12.1 arise from the same gene. A recombinant two‐domain form (α1AI‐II) of α12.1 associates with the β subunit and is trafficked to the plasma membrane. Translocation of the α1AI‐II to the plasma membrane requires association with the β subunit, since a mutation in the α1AI‐II that inhibits β subunit association reduces membrane trafficking. Though the α1AI‐II protein does not conduct any voltage‐gated currents, we have previously shown that it generates a high density of non‐linear charge movements [Ahern et al., Proc. Natl. Acad. Sci. USA 98 (2001) 6935–6940]. In this study, we demonstrate that co‐expression of the α1AI‐II significantly reduces the current amplitude of α12.1/β1a/α2δ channels, via competition for the β subunit. Taken together, our results demonstrate a dual functional role for the α1AI‐II protein, both as a voltage sensor and modulator of P/Q‐type currents in recombinant systems. These studies suggest an in vivo role for the 95kD‐α12.1 in altering synaptic activity via protein–protein interactions and/or regulation of P/Q‐type currents.
Localisation and regulation of the eIF4E‐binding protein 4E‐BP3
Authors: Kleijn Miranda , Scheper Gert C , Wilson Mary L , Tee Andrew R , Proud Christopher G
Published: December 2002

The cap‐binding protein eIF4E‐binding protein 3 (4E‐BP3) was identified some years ago, but its properties have not been investigated in detail. In this report, we investigated the regulation and localisation of 4E‐BP3. We show that 4E‐BP3 is present in the nucleus as well as in the cytoplasm in primary T cells, HEK293 cells and HeLa cells. 4E‐BP3 was associated with eIF4E in both cell compartments. Furthermore, 4E‐BP3/eIF4E association in the cytoplasm was regulated by serum or interleukin‐2 starvation in the different cell types. Rapamycin did not affect the association of eIF4E with 4E‐BP3 in the cytoplasm or in the nucleus.
A directional electron transfer regulator based on heme‐chain architecture in the small tetraheme cytochrome c from Shewanella oneidensis
Authors: Harada Erisa , Kumagai Jiro , Ozawa Kiyoshi , Imabayashi Shinichiro , Tsapin Alexandre S , Nealson Kenneth H , Meyer Terrance E , Cusanovich Michael A , Akutsu Hideo
Published: December 2002

The macroscopic and microscopic redox potentials of the four hemes of the small tetraheme cytochrome c from Shewanella oneidensis were determined. The microscopic redox potentials show that the order of reduction is from hemes in the C‐terminal domain (hemes 3 and 4) to the N‐terminal domain (heme 1), demonstrating the polarization of the tetraheme chain during reduction. This makes heme 4 the most efficient electron delivery site. Furthermore, multi‐step reduction of other redox centers through either heme 4 or heme 3 is shown to be possible. This has provided new insights into the two‐electron reduction of the flavin in the homologous flavocytochrome c–fumarate reductase.
Brown adipocytes are novel sites of expression and regulation of adiponectin and resistin
Authors: Viengchareun Say , Zennaro Maria-Christina , Pascual-Le Tallec Laurent , Lombes Marc
Published: December 2002

Adiponectin and resistin, two recently identified adipocyte‐specific secretory factors, are able to modulate insulin actions in target tissues. To investigate their expression and hormonal regulation in brown adipocytes, we used the brown adipocyte cell line T37i, which, beside uncoupling protein expression, secretes leptin. Adiponectin and resistin mRNA were detected as a function of cell differentiation. Both transcripts were expressed at relatively high levels in differentiated T37i cells, reaching maximal levels on day 7, while resistin expression drastically fell afterwards. These stable transcripts (t
1/2>8 h) were differentially regulated by factors involved in insulin responsiveness. Insulin and thiazolidinedione, a peroxisome proliferator‐activated receptor γ agonist, stimulated resistin expression two‐ to four‐fold in differentiated T37i cells, whereas adiponectin mRNA levels increased 1.5–2‐fold. In contrast, dexamethasone and isoproterenol reduced by two‐fold the level of adiponectin and resistin transcripts in differentiated T37i cells. This study provides the first direct evidence that differentiated brown adipocytes are endocrine cells capable of expressing adiponectin and resistin. The complex hormonal regulation of their expression in brown adipocytes clearly differs from that reported in white adipose tissue, pointing to differential physiological and pathophysiological implications of brown fat in energy homeostasis.
Cdc42 and Rac1 are necessary for autotaxin‐induced tumor cell motility in A2058 melanoma cells
Authors: Jung In Duk , Lee Jangsoon , Yun Seong Young , Park Chang Gyo , Choi Wahn Soo , Lee Hyang Woo , Choi Oksoon H , Han Jeung Whan , Lee Hoi Young
Published: December 2002

Autotaxin (ATX) is a strong motogen that can increase invasiveness and angiogenesis. In the present study, we investigated the signal transduction mechanism of ATX‐induced tumor cell motility. Unlike N19RhoA expressing cells, the cells expressing N17Cdc42 or N17Rac1 showed reduced motility against ATX. ATX activated Cdc42 and Rac1 and increased complex formation between these small G proteins and p21‐activated kinase (PAK). Furthermore, ATX phosphorylated focal adhesion kinase (FAK) that was not shown in cells expressing dominant negative mutants of Cdc42 or Rac1. Collectively, these data strongly indicate that Cdc42 and Rac1 are essential for ATX‐induced tumor cell motility in A2058 melanoma cells, and that PAK and FAK might be also involved in the process.
14‐3‐3 binding to the IGF‐1 receptor is mediated by serine autophosphorylation1
Authors: Parvaresch Susan , Yesilkaya Tanju , Baer Kristin , Al-Hasani Hadi , Klein Helmut W
Published: December 2002

The phosphoserine‐binding 14‐3‐3 proteins have been implicated in playing a role in mitogenic and apoptotic signaling pathways. Binding of 14‐3‐3 proteins to phosphoserine residues in the C‐terminus of the insulin‐like growth factor‐1 receptor (IGF‐1R) has been described to occur in a variety of cell systems, but the kinase responsible for this serine phosphorylation has not been identified yet. Here we present evidence that the isolated dimeric insulin‐like growth factor‐1 receptor kinase domain (IGFKD) contains a dual specific (i.e. tyrosine/serine) kinase activity that mediates autophosphorylation of C‐terminal serine residues in the enzyme. From the total phosphate incorporation of ∼4 mol per mol kinase subunit, 1 mol accounts for serine phosphate. However, tyrosine autophosphorylation proceeds more rapidly than autophosphorylation of serine residues (t
1/2∼1 min vs. t
1/2∼5 min). Moreover, dot‐blot and far‐Western analyses reveal that serine autophosphorylation of IGFKD is sufficient to promote binding of 14‐3‐3 proteins in vitro. The proof that dual kinase activity of IGFKD is necessary and sufficient for 14‐3‐3 binding was obtained with an inactive kinase mutant that was phosphorylated on serine residues in a stoichiometric reaction with the catalytically active enzyme. Thus, the IGF‐1R itself might be responsible for the serine autophosphorylation which leads to recognition of 14‐3‐3 proteins in vivo.
The gene for domains rearranged methyltransferase (DRM2) in Arabidopsis thaliana plants is methylated at both cytosine and adenine residues
Authors: Ashapkin Vasili V , Kutueva Lyudmila I , Vanyushin Boris F
Published: December 2002

The methylation patterns of cytosine and adenine residues in the Arabidopsis thaliana gene for domains rearranged methyltransferase (DRM2) were studied in wild‐type and several transgene plant lines containing antisense fragments of the cytosine DNA‐methyltransferase gene METI under the control of copper‐inducible promoters. It was shown that the promoter region of the DRM2 gene is mostly unmethylated at the internal cytosine residue in CCGG sites whereas the 3′‐end proximal part of the gene coding region is highly methylated. The DRM2 gene was found to be also methylated at adenine residues in some GATC sequences. Cytosine methylation in CCGG sites and adenine methylation in GATC sites in the DRM2 gene are variable between wild‐type and different transgenic plants. The induction of antisense METI constructs with copper ions in transgene plants in most cases leads to further alterations in the DRM2 gene methylation patterns.
The protease core of the muscle‐specific calpain, p94, undergoes Ca2+‐dependent intramolecular autolysis
Authors: Rey Michelle A , Davies Peter L
Published: December 2002

Limb girdle muscular dystrophy type 2A is linked to a skeletal muscle‐specific calpain isoform known as p94. Isolation of the intact 94‐kDa enzyme has been difficult to achieve due to its rapid autolysis, and uncertainty has arisen over its Ca2+‐dependence for activity. We have expressed a C‐terminally truncated form of the enzyme that comprises the protease core (domains I and II) along with its insertion sequence, IS1, and N‐terminal leader sequence, NS. This 47‐kDa p94I‐II mini‐calpain was stable during purification. In the presence of Ca2+, p94I‐II cleaved itself within the NS and IS1 sequences. Mapping of the autolysis sites showed that NS and IS1 have the potential to be removed without damage to the protease core. Ca2+‐dependent autolysis must be an intramolecular event because the inactive p94I‐II C129S mutant was not cleaved by incubation with wild‐type p94I‐II. In addition, the rate of autolysis of p94I‐II was independent of the concentration of the enzyme.
Uncoupling protein and alternative oxidase of Dictyostelium discoideum: occurrence, properties and protein expression during vegetative life and starvation‐induced early development
Authors: Jarmuszkiewicz Wiesawa , Behrendt Maciej , Navet Rachel , Sluse Francis E.
Published: December 2002

In this study we show that mitochondria of Dictyostelium discoideum contain both alternative oxidase (AOX) and uncoupling protein (UCP). AOX was stimulated by purine mononucleoside and was monomeric. UCP was stimulated by free fatty acids and was poorly sensitive to GTP. Both proteins collaborated in energy dissipation when activated together. AOX expression in free‐living ameboid cells decreased strongly from exponential to stationary phase of growth but much less during starvation‐induced aggregation. In contrast, UCP expression was constant in all conditions indicating permanent need. Our results suggest that AOX could play a role in cell differentiation, mainly by protecting prespore cells from programmed cell death.
Modeling the dynamics of sediment transport and resuspension in the northern Adriatic Sea
Authors: Wang X. H. , Pinardi N.
Published: December 2002

A coupled Adriatic Sea General Circulation and sediment transport model was used to study the dynamics of coarse and fine sediment transport and resuspension in the Northern Adriatic Sea. The sediment sizes of coarse (>50 μm) and fine (<50 μm) materials were sorted by their settling velocities. The bottom boundary layer (BBL) was discretized by a vertical sigma coordinate system with high resolution, and the wave‐current interaction mechanism was considered. The sediment distributions and fluxes under various forcing conditions such as the Po River plume, the Bora and Scirocco wind stress and the surface waves were studied by process oriented numerical simulations. The conclusions are that maximum northward sediment transport occurs under the forcing by the Po River plume with the Scirocco wave resuspension. The largest southward sediment transport was due to the combined effect of the Po River plume and the Bora wind‐forcing under the Bora wave conditions. A realistic forcing numerical experiment was also conducted for November 1994 when the full range of forcing functions were experienced by the region. This study shows that wave‐driven sediment resuspension is an important resuspension mechanism in the shallow coastal areas of the Northern Adriatic Sea, and contributes significantly to the complexity of the sediment distribution and flux features in the region.
Marine and anthropogenic aerosols at Punta Del Hidalgo, Tenerife, and the aerosol nitrate number paradox
Authors: McGovern F. M. , Nunes M. J. , Raes F. , Gonzales‐Jorge H.
Published: December 2002

Results from analysis of aerosol ion composition and condensation nuclei (CN) concentration measurements carried out at the second Aerosol Characterization Experiment (ACE‐2) Tenerife site, in the eastern North Atlantic subtropical region between July 1995 and May 1997, are described. Sea‐salt derived Na+ dominated the samples having an average concentration of 2.4 μg m−3. Extensive anthropogenic influences are evident with average non‐sea‐salt sulfate (nssSO42−) and nitrate (NO3−) concentration values of 2.1 μg m−3 and 1.3 μg m−3 respectively. High levels of these species are linked to air mass transport from Europe: observed as short‐term (2–3 days) pollution peaks. The pollution peaks overlie a summertime maximum in background levels. From comparison with Southern Hemisphere data, it is estimated that ∼80% of the observed nssSO42− originated from anthropogenic sources. Regression analysis shows a high degree of linearity between the NO3− and CN concentration, which is stronger than found with between NssSO42− and CN concentration. This is considered paradoxical as in the maritime atmosphere NO3− has primarily been found in supermicron size range linked to sea‐salt, while nssSO42− and CN are primarily considered to be submicron aerosol. The CN:NO3− linearity is considered to arise from NO3− formation and transport processes over ocean regions.
Hydration, dehydration, and the total hydrogen budget of the 1999/2000 winter Arctic stratosphere
Authors: Herman R. L. , Drdla K. , Spackman J. R. , Hurst D. F. , Popp P. J. , Webster C. R. , Romashkin P. A. , Elkins J. W. , Weinstock E. M. , Gandrud B. W. , Toon G. C. , Schoeberl M. R. , Jost H. , Atlas E. L. , Bui T. P.
Published: December 2002

Stratospheric H2O, CH4, and H2 measured during the 1999/2000 Arctic winter are used to examine the total hydrogen budget and to quantify hydration and dehydration within the Arctic polar vortex. The mean volume mixing ratio of equivalent water, H2Oeq = H2O + 2*CH4, was found to be 7.38 ± 0.11 ppmv in the vortex and 7.35 ± 0.10 ppmv in the extravortex and vortex edge regions, implying insignificant net loss of H2O from the 50–90 hPa layer of the Arctic stratosphere. However, isolated occurrences of hydration and dehydration were observed on several flights. In particular, an average dehydration of 0.31 ppmv was encountered for 440 km along the NASA ER‐2 aircraft flight path on 27 January 2000 (0.63 ppmv maximum dehydration). Diabatic back‐trajectory calculations indicate that this dehydrated air parcel may have encountered temperatures below the ice frost point two weeks earlier. In addition to these isolated events, measurements of equivalent water indicated a decrease with altitude throughout the lower stratospheric vortex and vortex edge. Potential causes of this altitude dependence are quantified.
Semianalytical solutions of radioactive or reactive solute transport in variably fractured layered media
Authors: Moridis George J.
Published: December 2002

In this paper, semianalytical solutions are developed for the problem of transport of radioactive or reactive solute tracers through a layered system of heterogeneous fractured media with misaligned fractures. The tracer transport equations in the nonflowing matrix account for (1) diffusion, (2) surface diffusion, (3) mass transfer between mobile and immobile water fractions, (4) linear kinetic or equilibrium physical, chemical, or combined sorption or colloid filtration, and (5) radioactive decay or first‐order chemical reactions. The tracer transport equations in the fractures account for the same processes, in addition to advection and hydrodynamic dispersion. Any number of radioactive decay daughter products (or products of a linear, first‐order reaction chain) can be tracked. The solutions, which are analytical in the Laplace space, are numerically inverted to provide the solution in time and can accommodate any number of fractured and/or porous layers. The solutions are verified using analytical and numerical solutions for limiting cases of solute and colloid transport through fractured and porous media. The effect of important parameters on the transport of 3H, 99Tc, 237Np, and 239Pu (and its daughters) is investigated in several test problems involving layered geological systems of varying complexity.
Atmospheric biomarkers of subsurface life on Mars
Authors: Summers Michael E. , Lieb B. Joseph , Chapman Emily , Yung Yuk L.
Published: December 2002

If life exists beneath the Martian surface similar to terrestrial bacteria that rely upon chemical reactions involving H2and/or CO as energy sources, then it may be possible to infer its existence by observing metabolic by‐products that would appear as trace gases in the Martian atmosphere. We have studied the fate of organic trace gases in the Martian atmosphere and find that most have very short chemical lifetimes, however CH4has a chemical lifetime of about 300 yrs and thus it will tend to be uniformly distributed in the Martian atmosphere. Using the current observational upper limit on atmospheric CH4we deduce that its flux, from all sources, into the Martian atmosphere must be at least 105times less than terrestrial value. If there are abiotic sources of CH4on Mars then the biological component of the CH4must be even less.
Model of the energization of outer‐zone electrons by whistler‐mode chorus during the October 9, 1990 geomagnetic storm
Authors: Summers D. , Ma C. , Meredith N. P. , Horne R. B. , Thorne R. M. , Heynderickx D. , Anderson R. R.
Published: December 2002

Relativistic (>1 MeV) ‘killer electrons’ are frequently generated in the Earth's inner magnetosphere during the recovery phase of a typical magnetic storm. We test the hypothesis that the energization of electrons takes place by means of stochastic gyroresonant interaction between lower‐energy (several 100 keV) seed electrons and whistler‐mode chorus waves. We develop a model kinetic equation for the electron energy distribution, and utilize both electron and whistler‐mode wave data at L = 4 for a typical geomagnetic storm (on October 9, 1990) from instruments carried on the Combined Release and Radiation Effects Satellite (CRRES). Our model solutions are found to match well with the CRRES profiles of the electron flux. We conclude that the mechanism of stochastic acceleration by whistler‐mode turbulence is a viable candidate for generating killer electrons, not only for the storm considered, but for similar storms with a several‐day recovery phase containing prolonged substorm activity.
Distribution of fine‐scale shear in the deep waters of the North Pacific obtained using expendable current profilers
Authors: Nagasawa Maki , Hibiya Toshiyuki , Niwa Yoshihiro , Watanabe Michio , Isoda Yutaka , Takagi Shogo , Kamei Yoshihiko
Published: December 2002

Recent numerical experiments [Hibiya et al., 1996, 1998, 2002] predicted that the energy cascade across the internal wave spectrum down to small dissipation scales was under strong control by parametric subharmonic instabilities that transfer energy from the low vertical wave number, double‐inertial frequency wave band to a high vertical wave number, near‐inertial frequency wave band. To test whether or not the numerically predicted energy cascade process is actually dominant in the real deep ocean, we deployed a total of 106 expendable current profilers over a large area in the North Pacific to examine the spatial distribution of high vertical wave number (vertical wavelength ∼25 m) shear. At midlatitudes, significant enhancement of the 25 m vertical shear was found over prominent generation regions of semidiurnal internal tides such as the Hawaiian Ridge and the Izu‐Ogasawara Ridge where the semidiurnal tidal frequency exceeds twice the local inertial frequency. At high latitudes, in contrast, no significant enhancement of the 25 m vertical shear was found to occur even over another prominent generation region of semidiurnal internal tides, the Aleutian Ridge, where the semidiurnal tidal frequency is less than twice the local inertial frequency. We find that the spatial distribution of the intensity of the 25 m vertical shear correlates very well with that of the low vertical wave number, double‐inertial frequency internal wave energy numerically predicted by Nagasawa et al. [2000] and Niwa and Hibiya [2001a, 2001b]. This is the first in situ evidence for the dominant role of parametric subharmonic instability in transferring deep ocean internal wave energy down to small dissipation scales. This study provides a theoretical framework for future attempts to determine the large‐scale structure of mixing over the world's oceans.
Role of the ocean in the decadal climate change in the North Pacific
Authors: Masuda Shuhei
Published: December 2002

I have investigated features of decadal climate variability in the North Pacific and clarified the role of the ocean in controlling them, by analyzing historical data sets and executing experiments with a low‐order model. Detailed investigation of the variability of the wintertime Aleutian low and water temperature in the subarctic frontal region implies a new scenario for the mechanism of the decadal variability. The decadal variability can be interpreted as the transition process between two stable states (cold and warm period) in midlatitude atmosphere. When the transition to a cold period occurs, sea surface temperature in the subarctic frontal region begins to be lowered not only through the surface processes but by westward propagation of cold anomaly from eastern subarctic region as a baroclinic Rossby wave. As a result, the meridional gradient of sea surface heat flux (∂yQ0) decreases its magnitude and then the forcing of the Aleutian low is weakened. When this weakening exceeds a threshold, the transition from a cold to a warm period occurs abruptly. After the transition to a warm period, ∂yQ0, in turn, increases its magnitude through the opposite processes to cause the reverse transition. The timescale of this cycle is mainly determined by the propagation speed of a baroclinic Rossby wave. The El Niño and Southern Oscillation variability both in the atmosphere and ocean can also affect the timescale by causing the thresholds for transitions to be temporarily exceeded. Experiments with a four‐variable low‐order model support the proposed mechanism of the decadal variability.
A Honeycomb Network of a Paddlewheel-type Dirhodium Complex in Two Oxidation States and Pinning of the Oxidation States
Authors: Takazaki Yasuaki , Yang Zhiyong , Ebihara Masahiro , Inoue Katsuya , Kawamura Takashi
Published: December 2002

The reaction of a mixture of [Rh2(acam)4(H2O)2] (Hacam = acetamide) and its radical cation salt with sodium chloride in an aqueous solution gave a mixed-valent 2-D honeycomb crystal of [{Rh2(acam)4}3(μ3-Cl)2]n·4nH2O. The oxidation states of the dirhodium units are pinned at each of the crystal sites by hydrogen bonding with solvate-water molecules.
Identification of neuropeptide FF‐related peptides in human cerebrospinal fluid by mass spectrometry
Authors: Burlet-Schiltz Odile , Mazarguil Honoré , Sol Jean-Christophe , Chaynes Patrick , Monsarrat Bernard , Zajac Jean-Marie , Roussin Anne
Published: December 2002

Several neuropeptide FF (NPFF)‐related peptides, known as modulators of the opioid system, have been previously characterized in bovine and rodent brain. Reverse‐phase high pressure liquid chromatography (HPLC) fractions of a human with normal pressure hydrocephalus cerebrospinal fluid (CSF), co‐migrating with NPFF‐related synthetic peptides, were characterized by capillary HPLC coupled on‐line to nanospray ion trap tandem mass spectrometry. Two peptides present in the pro‐NPFFA precursor, NPAF (AGEGLNSQFWSLAAPQRF‐NH2) and NPSF (SLAAPQRF‐NH2), were identified. The monitoring of NPFF‐related peptides in human CSF can be helpful to understand their roles in pain sensitivity.
Relationship between protein kinase C and derepression of different enzymes
Authors: Salgado A.P.C , Schuller D , Casal M , Leão C , Leiper F.C , Carling D , Fietto L.G , Trópia M.J , Castro I.M , Brandão R.L
Published: December 2002

The PKC1 gene in the yeast Saccharomyces cerevisiae encodes for protein kinase C which is known to control a MAP kinase cascade consisting of different kinases: Bck1, Mkk1 and Mkk2, and Mpk1. This cascade affects the cell wall integrity but the phenotype of pkc1Δ mutants suggests additional targets that have not yet been identified [Heinisch et al., Mol. Microbiol. 32 (1999) 671–680]. The pkc1Δ mutant, as opposed to other mutants in the MAP kinase cascade, displays defects in the control of carbon metabolism. One of them occurs in the derepression of SUC2 gene after exhaustion of glucose from the medium, suggesting an involvement of Pkc1p in the derepression process that is not shared by the downstream MAP kinase cascade. In this work, we demonstrate that Pkc1p is required for the increase of the activity of enzymatic systems during the derepression process. We observed that Pkc1p is involved in the derepression of invertase and alcohol dehydrogenase activities. On the other hand, it seems not to be necessary for the derepression of the enzymes of the GAL system. Our results suggest that Pkc1p is acting through the main glucose repression pathway, since introduction of an additional mutation in the PKC1 gene in yeast strains already presenting mutations in the HXKII or MIG1 genes does not interfere with the typical derepressed phenotype observed in these single mutants. Moreover, our data indicate that Pkc1p participates in this process through the control of the cellular localization of the Mig1 transcriptional factor.
PEGylation of microspheres generates a heterogeneous population of particles with differential surface characteristics and biological performance
Authors: Gbadamosi J.K , Hunter A.C , Moghimi S.M
Published: December 2002

Surface PEGylation of polystyrene microspheres with methoxy‐poly(ethylene glycol)‐5000 (mPEG‐5000) generated a heterogeneous population of entities that differed in surface characteristics and in vitro biological performance (phagocytosis and complement activation). Surface heterogeneity was determined by hydrophobic interaction chromatography, measurements of particle electrophoretic mobility in a defined field and adlayer thickness of the projected mPEG chains. The particle population separation by hydrophobic interaction chromatography demonstrated a remarkable linear relationship between the particle zeta potential and phagocytosis by J774 A1 macrophage‐like cells. Microsphere populations bearing a predominant surface of mPEG molecules as high‐density mushroom–brush intermediate and/or brush configuration were most resistant to phagocytosis and activated the human complement system poorly. Conversely, those populations with predominant surface mPEGs in a mushroom regime were potent activators of the complement system and were prone to phagocytosis. Therefore, surface heterogeneity explains why a fraction of intravenously injected ‘long‐circulating’ nanoparticles is cleared rapidly by macrophages of the reticuloendothelial system. Hydrophobic interaction chromatography can readily assess the extent of surface heterogeneity of PEGylated particulate drug delivery systems and pre‐select particles with optimal retention times in the blood. These observations may also be relevant with respect to successful surface camouflaging of cells, drug depots and implantable devices.
CCl4‐induced acute liver injury in mice is inhibited by hepatocyte growth factor overexpression but stimulated by NK2 overexpression
Authors: Otsuka Toshiyuki , Takagi Hitoshi , Horiguchi Norio , Toyoda Mitsuo , Sato Ken , Takayama Hisashi , Mori Masatomo
Published: December 2002

Hepatocyte growth factor (HGF) inhibits acute liver injury. NK2 acts as an antagonist to HGF in vitro, but its in vivo function has reached no consensus conclusions. We have investigated in vivo effects of HGF and NK2 on CCl4‐induced acute liver injury. Elevation of the serum alanine aminotransferase level and extension of centrilobular necrosis were inhibited in HGF transgenic mice but were promoted in NK2 transgenic mice. Hepatocyte proliferation after liver injury was not inhibited in NK2 transgenic mice. Thus, this study indicates that HGF inhibits liver injury, and NK2 antagonizes HGF on liver injury, however, NK2 may not antagonize HGF on hepatocyte proliferation.
The tertiary amine local anesthetic dibucaine binds to the membrane skeletal protein spectrin
Authors: Mondal Mousumi , Chakrabarti Abhijit
Published: December 2002

The quinoline‐based tertiary amine dibucaine has been shown to bind the membrane skeletal protein spectrin with a dissociation constant of 3.5×10−5 M at 25°C. Such binding is detected by monitoring the quenching of the tryptophan fluorescence intensity with increasing concentrations of dibucaine only and not with the benzene‐based local anesthetics procaine, tetracaine and lidocaine. Binding of dibucaine also indicated changes in the tertiary structure of spectrin indicated by a circular dichroism spectrum in the near‐UV region due to absorption of the aromatic side chains. The thermodynamic parameters associated with the binding indicated the interaction of dibucaine and spectrin to be enthalpy‐driven and insensitive to an increase in the ionic strength of the buffer.
Reliability of transmembrane predictions in whole‐genome data
Authors: Käll Lukas , Sonnhammer Erik L.L
Published: December 2002

Transmembrane prediction methods are generally benchmarked on a set of proteins with experimentally verified topology. We have investigated if the accuracy measured on such datasets can be expected in an unbiased genomic analysis, or if there is a bias towards ‘easily predictable’ proteins in the benchmark datasets. As a measurement of accuracy, the concordance of the results from five different prediction methods was used (TMHMM, PHD, HMMTOP, MEMSAT, and TOPPRED). The benchmark dataset showed significantly higher levels (up to five times) of agreement between different methods than in 10 tested genomes. We have also analyzed which programs are most prone to make mispredictions by measuring the frequency of one‐out‐of‐five disagreeing predictions.
On the effect of random errors in gridded bathymetric compilations
Authors: Jakobsson Martin , Calder Brian , Mayer Larry
Published: December 2002

We address the problem of compiling bathymetric data sets with heterogeneous coverage and a range of data measurement accuracies. To generate a regularly spaced grid, we are obliged to interpolate sparse data; our objective here is to augment this product with an estimate of confidence in the interpolated bathymetry based on our knowledge of the component of random error in the bathymetric source data. Using a direct simulation Monte Carlo method, we utilize data from the International Bathymetric Chart of the Arctic Ocean database to develop a suitable methodology for assessment of the standard deviations of depths in the interpolated grid. Our assessment of random errors in each data set are heuristic but realistic and are based on available metadata from the data providers. We show that a confidence grid can be built using this method and that this product can be used to assess reliability of the final compilation. The methodology as developed here is applied to bathymetric data but is equally applicable to other interpolated data sets, such as gravity and magnetic data.
An in‐scene method for atmospheric compensation of thermal hyperspectral data
Authors: Young Stephen J. , Johnson B. Robert , Hackwell John A.
Published: December 2002

Interpretation of surface radiation characteristics by overhead hyperspectral imagery often requires a compensation of the measured radiance data for the absorption and emission effects of the intervening atmosphere. We describe a procedure that accounts for these effects by direct use of the hyperspectral radiance data without recourse to ancillary meteorological data or atmospheric modeling. This in‐scene atmospheric compensation (ISAC) procedure is applicable to a broad class of problems. The present work concerns terrestrial surface characterization by remote sensing in the 8–13 μm atmospheric window band. A complete ISAC analysis is carried out in two steps. In the first step, unscaled atmospheric compensation spectra (transmittance and upwelling radiance) are extracted from the data. The step is carried out by application of a specially designed, line‐fitting procedure to a scatterplot constructed from the hyperspectral data. The compensation spectra are defined in terms of the slope and intercept parameters of the line. In the second step, these unscaled compensation spectra are scaled to quantitative compensation spectra. Here, this step is carried out using the strength of absorption in the 11.7‐μm water band. The compensation procedure is demonstrated by application to hyperspectral imagery obtained with the Aerospace Corporation's Spatially Enhanced Broadband Array Spectrograph System (SEBASS) hyperspectral imaging sensor at the Department of Energy's (DOE) Atmospheric Radiation Measurement (ARM) facility. Example applications demonstrate the ability of the method to remove atmospheric spectral structure from the observed data and reveal the spectral structure intrinsic to the underlying surface. This removal is demonstrated both for near‐blackbody surfaces composed of grass and for surfaces containing limestone gravel and Red Clay soil.
Canadian Aerosol Module (CAM): A size‐segregated simulation of atmospheric aerosol processes for climate and air quality models 2. Global sea‐salt aerosol and its budgets
Authors: Gong S. L. , Barrie L. A. , Lazare M.
Published: December 2002

Size‐segregated sea‐salt aerosols were included as dynamic constituents in the third generation of the Canadian general circulation model (GCMIII) using the Canadian Aerosol Module (CAM). A 12‐bin sectional model was used to simulate wind‐dependent sea‐salt aerosol generation at the surface, diffusive, and advective transports, as well as wet and dry removals as a function of particle size. The dependence of model‐predicted atmospheric sea‐salt concentration on wind speed is weaker than the u3.41 dependence of sea‐salt emissions but nevertheless still significant. A comparison of GCMIII surface winds with European Centre for Medium‐Range Weather Forecasting reanalyzed winds was used to identify a globally averaged bias of modeled surface marine winds of 18%. After taking this into account, two‐year simulations were performed to study the atmospheric sea‐salt cycle. Comparisons of seasonal mean model predictions with observed sea‐salt mass concentrations at 24 marine observatories were in reasonable agreement (generally better than a factor of 2). The annual global sea‐salt flux is estimated to be 1.01 × 1013 kg with ∼32% from the Northern Hemisphere and with 98% in supermicron particles. Although emissions to the atmosphere of submicron sea‐salt particles larger than 0.2 μm radius make up only 2% of the total global emissions, they contribute significantly to the background aerosol mass and number concentrations in the marine atmosphere. Submicron sea‐salt aerosols contribute substantially to the total optical depth of the atmosphere over the open oceans. They account for 5–15% of total sea‐salt mass in air at the surface and 20% at 700 hPa. The global mass mean dry diameter of sea‐salt aerosols over oceans is 2.8 μm at the surface and 1.9 μm in the midtroposphere. Concentrations are highest in the roaring forties of the Southern Hemisphere and over the northern oceans from October to March. Residence times of sea‐salt aerosols were highly variable depending on size, vertical dispersion, and removal processes. The mean residence time for 7.7 μm and 0.4 μm particles in the marine boundary layer were in the range 0.3–10 hours and 80–360 hours, respectively.
Valley floor climate observations from the McMurdo dry valleys, Antarctica, 1986–2000
Authors: Doran Peter T. , McKay Christopher P. , Clow Gary D. , Dana Gayle L. , Fountain Andrew G. , Nylen Thomas , Lyons W. Berry
Published: December 2002

Climate observations from the McMurdo dry valleys, East Antarctica are presented from a network of seven valley floor automatic meteorological stations during the period 1986 to 2000. Mean annual temperatures ranged from −14.8°C to −30.0°C, depending on the site and period of measurement. Mean annual relative humidity is generally highest near the coast. Mean annual wind speed increases with proximity to the polar plateau. Site‐to‐site variation in mean annual solar flux and PAR is due to exposure of each station and changes over time are likely related to changes in cloudiness. During the nonsummer months, strong katabatic winds are frequent at some sites and infrequent at others, creating large variation in mean annual temperature owing to the warming effect of the winds. Katabatic wind exposure appears to be controlled to a large degree by the presence of colder air in the region that collects at low points and keeps the warm less dense katabatic flow from the ground. The strong influence of katabatic winds makes prediction of relative mean annual temperature based on geographical position (elevation and distance from the coast) alone, not possible. During the summer months, onshore winds dominate and warm as they progress through the valleys creating a strong linear relationship (r2 = 0.992) of increasing potential temperature with distance from the coast (0.09°C km−1). In contrast to mean annual temperature, summer temperature lends itself quite well to model predictions, and is used to construct a statistical model for predicting summer dry valley temperatures at unmonitored sites.
Rifting in heterogeneous lithosphere: Inferences from numerical modeling of the northern North Sea and the Oslo Graben
Authors: Pascal C. , Cloetingh S. A. P. L.
Published: December 2002

Permian rifting and magmatism are widely documented across NW Europe. The different Permian basins often display contrasting structural styles and evolved in lithospheric domains with contrasting past evolution and contrasting thermotectonic ages. In particular, the Oslo Graben and the northern North Sea rift initiated in close areas of northern Europe. The Oslo Graben evolved in the cold and stable Precambrian lithosphere of Fennoscandia, whereas the northern North Sea rift took birth in freshly reworked Caledonian lithosphere. Huge volumes of magmatic rocks characterize the relatively narrow Oslo Graben. In contrast, little magmatism is documented for the wide northern North Sea rift. Differences in timing between both rifts are inferred but still debated. We present numerical thermomechanical models along a lithospheric E‐W section that involves both the Oslo Graben and the northern North Sea area. Because the modeled section crosses the boundary between Caledonian and Proterozoic provinces, thermal and compositional heterogeneities are considered. As is suggested by various geophysical data sets, we also consider lithospheric thickness heterogeneities in the Precambrian lithosphere. Modeling results suggest that the northern North Sea was on top of “weak” lithosphere very sensitive to far‐field stresses. Consequently, we suggest that rifting in the northern North Sea began as early as regional extension was effective (i.e., Late Carboniferous–Early Permian) and does not postdate the Oslo Graben as it is commonly assumed. Rifting in the “strong” Precambrian lithosphere is unexpected. Modeling results suggest that a pre‐existing lithospheric thickness contrast within the Fennoscandian lithosphere favored rifting in the Oslo Graben.
Estimating moisture contents in the vadose zone using cross‐borehole ground penetrating radar: A study of accuracy and repeatability
Authors: Alumbaugh David , Chang Ping Yu , Paprocki Lee , Brainard James R. , Glass Robert J. , Rautman Christopher A.
Published: December 2002

Experiments have been conducted to demonstrate the accuracy and precision of moisture content estimates derived from cross‐borehole ground penetrating radar (XBGPR) measurements made within the vadose zone. Both numerical simulations and field data demonstrate that although a certain amount of image smearing occurs under ideal conditions the general trends in the spatial variation of the moisture content can be estimated by a simple empirical transformation from images of electromagnetic (EM) wave velocity. The field results are verified by comparing the radar‐derived images of volumetric moisture content to neutron log derived values. When an appropriate site‐specific conversion from radar wave velocity to moisture content is applied, a root mean square (RMS) error of 2.0–3.1% volumetric moisture content exists between the two sets. Further comparison of the two different data sets along with analysis of plots of the ray density through each cell indicates that regions of high moisture content are better resolved than regions of low moisture and that most of the discrepancy between radar‐derived and neutron‐derived moisture contents occurs in regions of high moisture content. Better spatial resolution can be provided if dense station spacing is used. However, the amount of extra time required to acquire the extra data may limit the usefulness of the method. Repeatability measurements made with five data sets demonstrate that the precision error of the data acquisition system employed averages about 0.54 ns, which translates to about a 0.5% error in moisture content estimation.
Response of the antarctic circumpolar current transport to global warming in a coupled model
Authors: Bi Daohua , Budd William F. , Hirst Anthony C. , Wu Xingren
Published: December 2002

The transient and long‐term adjustment process of the Antarctic Circumpolar Current (ACC) in response to global warming in the CSIRO climate model is examined in an integration, which is run under increasing atmospheric CO2 following the IPCC/IS92a scenario to stabilisation at triple the initial CO2 concentration (3 × CO2). The ACC transport through Drake Passage shows an evident strengthening along with the CO2 increase and, in the subsequent period with stabilised 3 × CO2, it keeps increasing steadily after CO2 tripling for a few centuries until a maximum (151 Sv, 17% larger than the initial state) is reached. The strengthening of the ACC transport results from the warming‐induced enhancement of the meridional density gradient in the ocean interior across the ACC: it leads to a speedup of the upper layer zonal flow which outweighs the deceleration in the underlying layer caused by the weakening of the deep overturning off Antarctica.
Dilation bands: A new form of localized failure in granular media
Authors: Du Bernard Xavier , Eichhubl Peter , Aydin Atilla
Published: December 2002

We report a structure that is characterized by a localized increase in porosity or dilation within a tabular band of on average 1–2 mm thickness in porous, poorly consolidated sand. These dilation bands formed in predominantly opening‐mode and provide a sharp contrast to planar opening‐mode fractures or joints with two discrete surfaces in consolidated, low porosity brittle rock. Our observation of dilation bands, together with previously recognized shear and compaction bands, complete the spectrum of localized deformation modes along tabular bands in poorly consolidated sand and sandstone consistent with recent theoretical predictions of deformation localization in granular media.