bluuebunny/crossref_metadata_2025 huggingface dataset:
Atmospheric Chemistry Experiment (ACE) Arctic stratospheric measurements of NOx during February and March 2004: Impact of intense solar flares
Authors: Rinsland Curtis P. , Boone Chris , Nassar Ray , Walker Kaley , Bernath Peter , McConnell John C. , Chiou Linda
Published: June 2005

Solar occultation measurements recorded in the Arctic by the Atmospheric Chemistry Experiment (ACE) Fourier transform spectrometer show elevated volume mixing ratios of NO and NO2 in the upper stratosphere from mid‐February to late March 2004. Mixing ratios of NO exceeded 1.3 ppmv (10−6 parts per million by volume) during mid‐February and are higher than any values previously reported in the Arctic during late winter and early spring. The elevated NOx (NO + NO2) mixing ratios likely resulted from particle emissions by intense solar flares that occurred the previous October and November followed by NOx production and downward transport to the upper stratospheric vortex where the elevated levels persisted due to the long lifetime of NOx during darkness in polar winter and early spring. The descent and the NOx decrease rates in the upper stratospheric vortex are estimated from an analysis of the time series. The measured descent rate is compared with previous observations and model predictions.
Dimensional analysis of observed structures using multipoint magnetic field measurements: Application to Cluster
Authors: Shi Q. Q. , Shen C. , Pu Z. Y. , Dunlop M. W. , Zong Q.‐G. , Zhang H. , Xiao C. J. , Liu Z. X. , Balogh A.
Published: June 2005

A new method is described to analyze the dimensional character of observed structures using multipoint magnetic field measurements of four or more spacecraft. The technique can provide three directions along which the magnetic field has the minimum, intermediate, and maximum derivatives if the magnetic gradient tensor G = ∇ at every moment has been estimated by multipoint measurements. It follows that the structure's dimensionality and the variation direction can be directly determined. Both Cluster observations and simulations have shown that it is feasible to obtain the invariant axis orientation for two‐dimensional structures such as flux tubes, and to find the normal directions for one‐dimensional structures such as discontinuities. One advantage of this method is that these directions can be determined instantaneously, point by point in the time series, and so can be tracked through each observed structure. The analysis tool provides us a new perspective of the observed structures in the space.
Evidence for rotationally driven plasma transport in Saturn's magnetosphere
Authors: Hill T. W. , Rymer A. M. , Burch J. L. , Crary F. J. , Young D. T. , Thomsen M. F. , Delapp D. , André N. , Coates A. J. , Lewis G. R.
Published: June 2005

Radial convective transport of plasma in a rotation‐dominated magnetosphere implies alternating longitudinal sectors of cooler, denser plasma moving outward and hotter, more tenuous plasma moving inward. The Cassini Plasma Spectrometer (CAPS) has provided dramatic new evidence of this process operating in the magnetosphere of Saturn. The inward transport of hot plasma is accompanied by adiabatic gradient and curvature drift, producing a V‐shaped dispersion signature on a linear energy‐time plot. Of the many (∼100) such signatures evident during the first two Cassini orbits, we analyze a subset (48) that are sufficiently isolated to allow determination of their ages, widths, and injection locations. Ages are typically <10.8 hr (Saturn's rotation period) but range up to several rotation periods. Widths are typically <1 RS (Saturn's radius) but range up to several RS. Injection locations are randomly distributed in local time and in Saturnian longitude. The apex of the V sometimes coincides with a localized density cavity in the cooler background plasma, and usually coincides with a localized diamagnetic depression of the magnetic field strength. These signatures are fully consistent with the convective motions that are expected to result from the centrifugal interchange instability.
Experientialism, Materialism, and the Pursuit of Happiness
Authors: Van Boven Leaf
Published: June 2005

Previous research indicates that materialistic aspirations are negatively associated with happiness and psychological health. Recent research extends these findings by demonstrating that allocating discretionary resources toward life experiences makes people happier than allocating discretionary resources toward material possessions. Respondents to various surveys have indicated that purchases made with the intention of acquiring life experiences make them happier than purchases made with the intention of acquiring material possessions. Thinking about experiential purchases has also been shown to produce more positive feelings than thinking about material purchases. Other studies suggest that experiential purchases make people happier because they are more open to positive reinterpretations, are more resistant to disadvantageous comparisons, and foster successful social relationships more than material purchases.
What we know about Leadership
Authors: Hogan Robert , Kaiser Robert B.
Published: June 2005

This article reviews the empirical literature on personality, leadership, and organizational effectiveness to make 3 major points. First, leadership is a real and vastly consequential phenomenon, perhaps the single most important issue in the human sciences. Second, leadership is about the performance of teams, groups, and organizations. Good leadership promotes effective team and group performance, which in turn enhances the well-being of the incumbents; bad leadership degrades the quality of life for everyone associated with it. Third, personality predicts leadership—who we are is how we lead—and this information can be used to select future leaders or improve the performance of current incumbents.
Positive Psychology's Two Cultures
Authors: Bacon Steven F.
Published: June 2005

The rise of positive psychology has contributed to the scientific study of human strengths and virtues. This article identifies two types of character strengths: focus strengths, exemplified by creativity, and balance strengths, exemplified by wisdom. Which type we pursue influences how we organize our personal and professional lives, including choices about what we do, where we do it, and what values we promote as professional practitioners, researchers, and teachers. G. A. Kimble (1984) identified two cultures of psychology based on members’ commitments to scientific or humanistic values. In a similar manner, two cultures of positive psychology, defined by the focus-balance distinction, are suggested here. Additional implications of the focus-balance distinction are discussed.
The tetraspanin D6.1A and its molecular partners on rat carcinoma cells
Authors: CLAAS Christoph , WAHL Joachim , ORLICKY David J. , KARADUMAN Handan , SCHNÖLZER Martina , KEMPF Tore , ZÖLLER Margot
Published: June 2005

Tetraspanins function as molecular organizers of multi-protein complexes by assembling primary complexes of a relatively low mass into extensive networks involved in cellular signalling. In this paper, we summarize our studies performed on the tetraspanin D6.1A/CO-029/TM4SF3 expressed by rat carcinoma cells. Primary complexes of D6.1A are almost indistinguishable from complexes isolated with anti-CD9 antibody. Indeed, both tetraspanins directly associate with each other and with a third tetraspanin, CD81. Moreover, FPRP (prostaglandin F2α receptor-regulatory protein)/EWI-F/CD9P-1), an Ig superfamily member that has been described to interact with CD9 and CD81, is also a prominent element in D6.1A complexes. Primary complexes isolated with D6.1A-specific antibody are clearly different from complexes containing the tetraspanin CD151. CD151 is found to interact only with D6.1A if milder conditions, i.e. lysis with LubrolWX instead of Brij96, are applied to disrupt cellular membranes. CD151 probably mediates the interaction of D6.1A primary complexes with α3β1 integrin. In addition, two other molecules were identified to be part of D6.1A complexes at this higher level of association: type II phosphatidylinositol 4-kinase and EpCAM, an epithelial marker protein overexpressed by many carcinomas. The characterization of the D6.1A core complex and additional more indirect interactions will help to elucidate the role in tumour progression and metastasis attributed to D6.1A.
Characterization of a novel human sperm-associated antigen 9 (SPAG9) having structural homology with c-Jun N-terminal kinase-interacting protein
Authors: JAGADISH Nirmala , RANA Ritu , SELVI Ramasamy , MISHRA Deepshikha , GARG Manoj , YADAV Shikha , HERR John C. , OKUMURA Katsuzumi , HASEGAWA Akiko , KOYAMA Koji , SURI Anil
Published: June 2005

We report a novel SPAG9 (sperm-associated antigen 9) protein having structural homology with JNK (c-Jun N-terminal kinase)-interacting protein 3. SPAG9, a single copy gene mapped to the human chromosome 17q21.33 syntenic with location of mouse chromosome 11, was earlier shown to be expressed exclusively in testis [Shankar, Mohapatra and Suri (1998) Biochem. Biophys. Res. Commun. 243, 561–565]. The SPAG9 amino acid sequence analysis revealed identity with the JNK-binding domain and predicted coiled-coil, leucine zipper and transmembrane domains. The secondary structure analysis predicted an α-helical structure for SPAG9 that was confirmed by CD spectra. Microsequencing of higher-order aggregates of recombinant SPAG9 by tandem MS confirmed the amino acid sequence and mono atomic mass of 83.9 kDa. Transient expression of SPAG9 and its deletion mutants revealed that both leucine zipper with extended coiled-coil domains and transmembrane domain of SPAG9 were essential for dimerization and proper localization. Studies of MAPK (mitogenactivated protein kinase) interactions demonstrated that SPAG9 interacted with higher binding affinity to JNK3 and JNK2 compared with JNK1. No interaction was observed with p38α or extracellular-signal-regulated kinase pathways. Polyclonal antibodies raised against recombinant SPAG9 recognized native protein in human sperm extracts and localized specifically on the acrosomal compartment of intact human spermatozoa. Acrosome-reacted spermatozoa demonstrated SPAG9 immunofluorescence, indicating its retention on the equatorial segment after the acrosome reaction. Further, anti-SPAG9 antibodies inhibited the binding of human spermatozoa to intact human oocytes as well as to matched hemizona. This is the first report of sperm-associated JNK-binding protein that may have a role in spermatozoa–egg interaction.
A statherin and calcium enriched layer at the air interface of human parotid saliva
Authors: PROCTOR Gordon B. , HAMDAN Sawsan , CARPENTER Guy H. , WILDE Peter
Published: June 2005

Parotid saliva placed in 35-mm-diameter tissue culture dishes developed increasing surface viscoelasticity at the interface with air. A surface layer became visible with time, and was collected and analysed by protein electrophoresis which indicated that a single protein (pI 4.2; molecular mass approx. 6 kDa) predominated. Western blot analysis demonstrated that the major protein band reacted with an antiserum directed against the C-terminal of the calcium-binding salivary protein statherin. Matrix-assisted laser-desorption ionization–time-of-flight MS analysis gave a molecular mass of 5380 Da for the protein, corresponding to the molecular mass of statherin. Staining of film protein in electrophoresis gels was compared with statherin synthesized on a solid phase, and the mean statherin content of film formed from 1 ml of parotid saliva was measured as 7 nmol. The mean calcium content of the surface layer was 250 nmol. Surface rheology was greatly decreased in the presence of EDTA, whereas surface tension of saliva was unaffected by calcium chelation, suggesting that protein accumulated at the surface was unaffected. The results suggest that a layer rich in statherin forms at the interface of saliva and air, and that the surface rheology developed is dependent upon protein interactions mediated by calcium. The surface layer may enhance the function of saliva as a protective layer on the mucosal surfaces and teeth.
Molecular and biochemical characterization of an endo-β-1,3-glucanase from the pinewood nematode Bursaphelenchus xylophilus acquired by horizontal gene transfer from bacteria
Authors: KIKUCHI Taisei , SHIBUYA Hajime , JONES John T.
Published: June 2005

We report the cloning and functional characterization of an endo-β-1,3-glucanase from the pinewood nematode Bursaphelenchus xylophilus acquired by horizontal gene transfer from bacteria. This is the first gene of this type from any nematode species. We show that a similar cDNA is also present in another closely related species B. mucronatus, but that similar sequences are not present in any other nematode studied to date. The B. xylophilus gene is expressed solely in the oesophageal gland cells of the nematode and the protein is present in the nematode's secretions. The deduced amino acid sequence of the gene is very similar to glycosyl hydrolase family 16 proteins. The recombinant protein, expressed in Escherichia coli, preferentially hydrolysed the β-1,3-glucan laminarin, and had very low levels of activity on β-1,3-1,4-glucan, lichenan and barley β-glucan. Laminarin was degraded in an endoglucanase mode by the enzyme. The optimal temperature and pH for activity of the recombinant enzyme were 65 °C and pH 4.9. The protein is probably important in allowing the nematodes to feed on fungi. Sequence comparisons suggest that the gene encoding the endo-β-1,3-glucanase was acquired by horizontal gene transfer from bacteria. B. xylophilus therefore contains genes that have been acquired by this process from both bacteria and fungi. These findings support the idea that multiple independent horizontal gene transfer events have helped in shaping the evolution of several different life strategies in nematodes.
In vivo DNase I-mediated footprinting analysis along the human bradykinin B1 receptor (BDKRB1) gene promoter: evidence for cell-specific regulation
Authors: ANGERS Martin , DROUIN Régen , BACHVAROVA Magdalena , PARADIS Isabelle , BISSELL Brad , HIROMURA Makoto , USHEVA Anny , BACHVAROV Dimcho
Published: June 2005

By applying in vivo dimethyl sulphate and UV light type C-footprinting analysis, we previously showed that specific DNA sequences in the −1349/+42 core promoter region of the inducible human BDKRB1 (bradykinin B1 receptor) gene correlated with its transcriptional activity. In the present study we used the highly sensitive DNase I in vivo footprinting approach to delineate more precisely the functional domains of the BDKRB1 gene promoter in human SMCs (smooth muscle cells). Human lymphocytes that do not express a functional BDKRB1 were also studied as a reference using dimethyl sulphate, UV light type C and DNase I treatments. An obvious difference was found in the DNase I-footprinting patterns between cellular systems that express a functional BDKRB1 (SMCs) in comparison with human lymphocytes, where randomly distributed nucleosome-like footprinting patterns were found in the bulk of the core promoter region studied. Gel-shift assays and expression studies pointed to the implication of the YY1 and a TBP/TFIIB (TATA-box-binding protein/transcription factor IIB) transcription factor in the regulation of BDKRB1 gene expression in SMCs and possible YY1 involvement in the mechanisms of nuclear factor κB-mediated regulation of the receptor expression. No significant changes in the promoter foot-printing pattern were found after treatment with interleukin-1β or serum (known BDKRB1 gene inducers), indicating that definite regulatory motifs could exist outside the BDKRB1 gene core promoter region studied.
Defective thermoregulation, impaired lipid metabolism, but preserved adrenergic induction of gene expression in brown fat of mice lacking C/EBPβ
Authors: CARMONA M. Carmen , HONDARES Elayne , RODRÍGUEZ DE LA CONCEPCIÓN M. Luisa , RODRÍGUEZ-SUREDA Víctor , PEINADO-ONSURBE Julia , POLI Valeria , IGLESIAS Roser , VILLARROYA Francesc , GIRALT Marta
Published: June 2005

C/EBPβ (CCAAT/enhancer-binding protein β) is a transcriptional regulator of the UCP1 (uncoupling protein-1) gene, the specific marker gene of brown adipocytes that is responsible for their thermogenic capacity. To investigate the role of C/EBPβ in brown fat, we studied the C/EBPβ-null mice. When placed in the cold, C/EBPβ−/− mice did not maintain body temperature. This cold-sensitive phenotype occurred, although UCP1 and PGC-1α (peroxisome-proliferator-activated receptor γ co-activator-1α) gene expression was unaltered in brown fat of C/EBPβ−/− mice. The UCP1 gene promoter was repressed by the truncated inhibitory C/EBPβ isoform LIP (liver-enriched transcriptional inhibitory protein, the truncated inhibitory C/EBPβ isoform). Since C/EBPβ-null mice lack both C/EBPβ isoforms, active LAP (liver-enriched transcriptional activatory protein, the active C/EBPβ isoform) and LIP, the absence of LIP may have a stronger effect than the absence of LAP upon UCP1 gene expression. Gene expression for UCP2 and UCP3 was not impaired in all tissues analysed. In primary brown adipocytes from C/EBPβ−/− mice, induction of gene expression by noradrenaline was preserved. In contrast, the expression of genes related to lipid storage was impaired, as was the amount of triacylglycerol mobilized after acute cold exposure in brown fat from C/EBPβ−/− mice. LPL (lipoprotein lipase) activity was also impaired in brown fat, but not in other tissues of C/EBPβ−/− mice. LPL protein levels were also diminished, but this effect was independent of changes in LPL mRNA, suggesting that C/EBPβ is involved in the post-transcriptional regulation of LPL gene expression in brown fat. In summary, defective thermoregulation owing to the lack of C/EBPβ is associated with the reduced capacity to supply fatty acids as fuels to sustain brown fat thermogenesis.
Sphingosine 1-phosphate analogue recognition and selectivity at S1P4 within the endothelial differentiation gene family of receptors
Authors: INAGAKI Yuichi , PHAM TrucChi T. , FUJIWARA Yuko , KOHNO Takayuki , OSBORNE Daniel A. , IGARASHI Yasuyuki , TIGYI Gabor , PARRILL Abby L.
Published: June 2005

Synergistic computational and experimental studies provided previously unforeseen details concerning the structural basis of S1P (sphingosine 1-phosphate) recognition by the S1P4 G-protein-coupled receptor. Similarly to reports on the S1P1 receptor, cationic and anionic residues in the third transmembrane domain (R3.28 and E3.29 at positions 124 and 125) form ion pairs with the phosphate and ammonium of S1P, and alanine mutations at these positions abolished specific S1P binding, S1P-induced receptor activation and cell migration. Unlike findings on the S1P1 receptor, no cationic residue in the seventh transmembrane domain interacts with the phosphate. Additionally, two previously undiscovered interactions with the S1P polar headgroup have been identified. Trp186 at position 4.64 in the fourth transmembrane domain interacts by a cation-π interaction with the ammonium group of S1P. Lys204 at position 5.38 forms an ion pair with the S1P. The S1P4 and S1P1 receptors show differences in binding-pocket shape and electrostatic distributions that correlate with the published structure–activity relationships. In particular, the binding pocket of mS1P4 (mouse S1P4) has recognition sites for the anionic phosphate and cationic ammonium groups that are equidistant from the end of the non-polar tail. In contrast, the binding pocket of hS1P1 (human S1P4) places the ammonium recognition site 2 Å (1 Å=0.1 nm) closer to the end of the non-polar tail than the phosphate recognition site.
Sarcolipin and phospholamban mRNA and protein expression in cardiac and skeletal muscle of different species
Authors: VANGHELUWE Peter , SCHUERMANS Marleen , ZÁDOR Ernö , WAELKENS Etienne , RAEYMAEKERS Luc , WUYTACK Frank
Published: June 2005

The widely held view that SLN (sarcolipin) would be the natural inhibitor of SERCA1 (sarcoplasmic/endoplasmic-reticulum Ca2+-ATPase 1), and PLB (phospholamban) its counterpart for SERCA2 inhibition is oversimplified and partially wrong. The expression of SLN and PLB mRNA and protein relative to SERCA1 or SERCA2 was assessed in ventricle, atrium, soleus and EDL (extensor digitorum longus) of mouse, rat, rabbit and pig. SLN protein levels were quantified by means of Western blotting using what appears to be the first successfully generated antibody directed against SLN. Our data confirm the co-expression of PLB and SERCA2a in cardiac muscle and the very low levels (in pig and rabbit) or the absence (in rat and mouse) of PLB protein in the slow skeletal muscle. In larger animals, the SLN mRNA and protein expression in the soleus and EDL correlates with SERCA1a expression, but, in rodents, SLN mRNA and protein show the highest abundance in the atria, which are devoid of SERCA1. In the rodent atria, SLN could therefore potentially interact with PLB and SERCA2a. No SLN was found in the ventricles of the different species studied, and there was no compensatory SLN up-regulation for the loss of PLB in PLB−/− mouse. In addition, we found that SLN expression was down-regulated at the mRNA and protein level in the atria of hypertrophic hearts of SERCA2b/b mice. These data suggest that superinhibition of SERCA by PLB-SLN complexes could occur in the atria of the smaller rodents, but not in those of larger animals.
Mitochondrial reactive oxygen species regulate the temporal activation of nuclear factor κB to modulate tumour necrosis factor-induced apoptosis: evidence from mitochondria-targeted antioxidants
Authors: HUGHES Gillian , MURPHY Michael P. , LEDGERWOOD Elizabeth C.
Published: June 2005

ROS (reactive oxygen species) from mitochondrial and non-mitochondrial sources have been implicated in TNFα (tumour necrosis factor α)-mediated signalling. In the present study, a new class of specific mitochondria-targeted antioxidants were used to explore directly the role of mitochondrial ROS in TNF-induced apoptosis. MitoVit E {[2-(3,4-dihydro-6-hydroxy-2,5,7,8-tetramethyl-2H-1-benzopyran-2-yl)ethyl]triphenylphosphonium bromide} (vitamin E attached to a lipophilic cation that facilitates accumulation of the antioxidant in the mitochondrial matrix) enhanced TNF-induced apoptosis of U937 cells. In time course analyses, cleavage and activation of caspase 8 in response to TNF were not affected by MitoVit E, whereas the activation of caspase 3 was significantly increased. Furthermore, there was an increased cleavage of the proapoptotic Bcl-2 family member Bid and an increased release of cytochrome c from mitochondria, in cells treated with TNF in the presence of MitoVit E. We considered several mechanisms by which MitoVit E might accelerate TNF-induced apoptosis including mitochondrial integrity (ATP/ADP levels and permeability transition), alterations in calcium homoeostasis and transcription factor activation. Of these, only the transcription factor NF-κB (nuclear factor κB) was implicated. TNF caused maximal nuclear translocation of NF-κB within 15 min, compared with 1 h in cells pretreated with MitoVit E. Thus the accumulation of an antioxidant within the mitochondrial matrix enhances TNF-induced apoptosis by decreasing or delaying the expression of the protective antiapoptotic proteins. These results demonstrate that mitochondrial ROS production is a physiologically relevant component of the TNF signal-transduction pathway during apoptosis, and reveal a novel functional role for mitochondrial ROS as a temporal regulator of NF-κB activation and NF-κB-dependent antiapoptotic signalling.
Immunodetection of the expression of microsomal proteins encoded by the glucose 6-phosphate transporter gene
Authors: SENESI Silvia , MARCOLONGO Paola , KARDON Tamas , BUCCI Giovanna , SUKHODUB Andrey , BURCHELL Ann , BENEDETTI Angelo , FULCERI Rosella
Published: June 2005

Glucose 6-phosphate transport has been well characterized in liver microsomes. The transport is required for the functioning of the glucose-6-phosphatase enzyme that is situated in the lumen of the hepatic endoplasmic reticulum. The genetic deficiency of the glucose 6-phosphate transport activity causes a severe metabolic disease termed type 1b glycogen storage disease. The cDNA encoding a liver transporter for glucose 6-phosphate was cloned and was found to be mutated in patients suffering from glycogen storage disease 1b. While related mRNAs have been described in liver and other tissues, the encoded protein(s) has not been immunologically characterized yet. In the present study, we report (using antibodies against three different peptides of the predicted amino acid sequence) that a major protein encoded by the glucose 6-phosphate transporter gene is expressed in the endoplasmic reticulum membranes of rat and human liver. The protein has an apparent molecular mass of approx. 33 kDa using SDS/PAGE, but several lines of evidence indicate that its real molecular mass is 46 kDa, as expected. The glucose 6-phosphate transporter protein was also immunodetected in kidney microsomes, but not in microsomes derived from human fibrocytes, rat spleen and lung, and a variety of cell lines. Moreover, little or no expression of the glucose 6-phosphate transporter protein was found in liver microsomes obtained from three glycogen storage disease 1b patients, even bearing mutations that do not directly interfere with protein translation, which can be explained by a (proteasome-mediated) degradation of the mutated transporter.
The capsular polysaccharide biosynthesis of Streptococcus pneumoniae serotype 8: functional identification of the glycosyltransferase WciS (Cap8H)
Authors: SAKSOUK Nehmé , PELOSI Ludovic , COLIN-MOREL Pierre , BOUMEDIENNE Manel , ABDIAN Patricia L. , GEREMIA Roberto A.
Published: June 2005

CPS (capsular polysaccharide) is a major virulence factor in Streptococcus pneumoniae. Biosynthesis of CPS RU (repeat unit) proceeds by sequential transfer of sugar residues from the appropriate sugar donor to an activated lipid carrier by committed GTs (glycosyltransferases). While the nucleotide sequence of many cps loci is already known, the real substrate specificity of the hypothetical GTs, as well as the sequence of sugar addition is unclear. In the present paper, we report the biochemical characterization of one α-galactosyltransferase, WciS (Cap8H), a member of GT family 4. This enzyme is implicated in the tetrasaccharide RU biosynthetic pathway of Strep. pneumoniae CPS 8 ([→4)-α-D-Glcp-(1→4)-α-D-Galp-(1→4)-β-D-GlcAp-(1→4)-β-D-Glcp-(1→]n). Expression of WciS–His6 in Escherichia coli BL21 (DE3) strains or BL21 (DE3)/ΔgalU strain resulted in synthesis of a 39 kDa membrane-associated protein identified by N-terminal sequencing and recognized by anti-His6-tag antibody. This protein was capable of adding a galactose residue cellobiuronic acid [β-D-GlcAp-(1→4)-D-Glcp]-pyrophosphate-polyprenol from UDP-Gal. The newly added galactose residue is removed by α-galactosidase, indicating that WciS is a retaining GT. Our results suggest that WciS catalyses the addition of the third sugar residue of the CPS 8 RU. The recombinant WciS–His6 was solubilized and purified as a soluble multimer, opening the way for structural studies.
Ras plasma membrane signalling platforms
Authors: HANCOCK John F. , PARTON Robert G.
Published: June 2005

The plasma membrane is a complex, dynamic structure that provides platforms for the assembly of many signal transduction pathways. These platforms have the capacity to impose an additional level of regulation on cell signalling networks. In this review, we will consider specifically how Ras proteins interact with the plasma membrane. The focus will be on recent studies that provide novel spatial and dynamic insights into the micro-environments that different Ras proteins utilize for signal transduction. We will correlate these recent studies suggesting Ras proteins might operate within a heterogeneous plasma membrane with earlier biochemical work on Ras signal transduction.
High-accuracy, midinfrared (450cm−1⩽ω⩽4000cm−1) refractive index values of silicon
Authors: Chandler-Horowitz Deane , Amirtharaj Paul M.
Published: June 2005

The real and imaginary parts of the refractive index, n(ω) and k(ω), of silicon were measured as a function of photon frequency ω using Fourier transform infrared (FTIR) transmission spectral data. An accurate mechanical measurement of the wafer’s thickness, t, was required, and two FTIR spectra were used: one of high resolution (Δω=0.1to0.5cm−1) yielding a typical channel spectrum (Fabry–Perot fringes) dependent mainly on t and n(ω), and one of low resolution (Δω=4.0cm−1) yielding an absorption spectrum dependent mainly on t and k(ω). A procedure was developed to first get initial estimates for n(ω) for the high-resolution spectrum and then calculate k(ω) from the faster low-resolution spectrum with minimal measurement drift. Then both initial n and final k values were used together as starting point data for a fit to the high-resolution spectrum. A previously derived transmission formula for a convergent incident beam was used for the fit. The accuracy of n(ω) determined using this procedure is mostly dependent upon the measurement error in the sample thickness t and k(ω) is dominated by the accuracy of the absolute transmission values obtained from a sample-in and sample-out methods. Our results are compared with previously published values for n(ω) and k(ω) in the 450–4000-cm−1 spectral region. The reported uncertainty in n(ω) is ±10−4 absolute, a factor of 10 better than published values. The values of n(ω) range from 3.4400 at 4000cm−1 (λ=2.5μm) to 3.4169 at 450cm−1 (λ=22.222μm). The k(ω) values had a standard deviation of ⩽±3% and are in good agreement with previous measurements.
Packing density and structure effects on energy-transfer dynamics in argon collisions with organic monolayers
Authors: Day B. Scott , Morris John R.
Published: June 2005

A combined experimental and molecular-dynamics simulation study has been used to investigate energy-transfer dynamics of argon atoms when they collide with n-alkanethiols adsorbed to gold and silver substrates. These surfaces provide the opportunity to explore how surface structure and packing density of alkane chains affect energy transfer in gas-surface collisions while maintaining the chemical nature of the surface. The chains pack standing up with 12° and 30° tilt angles relative to the surface normal and number densities of 18.9 and 21.5Å2∕molecule on the silver and gold substrates, respectively. For 7-kJ∕mol argon scattering, the two surfaces behave equivalently, fully thermalizing all impinging argon atoms. In contrast, these self-assembled monolayers (SAMs) are not equally efficient at absorbing the excess translational energy from high-energy, 35 and 80kJ∕mol, argon collisions. When high-energy argon atoms are scattered from a SAM on silver, the fraction of atoms that reach thermal equilibrium with the surface and the average energy transferred to the surface are lower than for analogous SAMs on gold. In the case of argon atoms with 80kJ∕mol of translational energy scattering from long-chain SAMs, 60% and 45% of the atoms detected have reached thermal equilibrium with the monolayers on gold and silver surfaces, respectively. The differences in the scattering characteristics are attributed to excitation efficiencies of different types of surface modes. The high packing density of alkyl chains on silver restricts certain low-energy degrees of freedom from absorbing energy as efficiently as the lower-density monolayers. In addition, molecular-dynamics simulations reveal that the extent to which argon penetrates into the monolayer is related to packing density. For argon atoms with 80-kJ∕mol incident energy, we find 16% and 7% of the atoms penetrate below the terminal methyl groups of C10 SAMs on gold and silver, respectively.
Ground and excited states of the Rydberg radical H3O: Electron propagator and quantum defect analysis
Authors: Melin Junia , Ortiz J. V. , Martín I. , Velasco A. M. , Lavín C.
Published: June 2005

Vertical excitation energies of the Rydberg radical H3O are inferred from ab initio electron propagator calculations on the electron affinities of H3O+. The adiabatic ionization energy of H3O is evaluated with coupled-cluster calculations. These predictions provide optimal parameters for the molecular-adapted quantum defect orbital method, which is used to determine oscillator strengths. Given that the experimental spectrum of H3O does not seem to be available, comparisons with previous calculations are discussed. A simple model Hamiltonian, suitable for the study of bound states with arbitrarily high energies is generated by these means.
Simulation results on a resistive plate chamber for a bakelite thickness of 1mm up to 3mm
Authors: Rhee J. T. , Jamil M.
Published: June 2005

The performance of bakelite electrodes with thicknesses of 1, 2, and 3mm in a double-gap resistive plate chamber (RPC) have been tested by GEANT-based Monte Carlo simulation. Results show that the thickness of bakelite plays an important role in detecting particle signals. For checking the efficiency of these RPCs, gamma particles in the range 0.01–100MeV have been simulated through different bakelite setups. For an isotropic gamma source, a sensitivity sγ<3.5×10−2 at <100MeV by a 1mm bakelite double-gap RPC has been observed. For the same gamma source with a 2mm bakelite RPC, a sensitivity sγ<4.0×10−2 at <100MeV has been measured, whereas for 3mm bakelite RPC, sensitivity results were sγ<4.44×10−2 at <100MeV. Similar characteristics of bakelite electrodes have been observed for a parallel gamma source configuration.
Temperature dependent energy transfer in Ar–O3 collisions
Authors: Ivanov Mikhail V. , Schinke Reinhard
Published: June 2005

The energy transfer between argon atoms and ozone complexes O3*, excited in the region of the dissociation threshold, is calculated for fixed temperatures (100K⩽T⩽2500K) using classical trajectories. The internal energy of ozone is resolved in terms of vibrational and rotational energies. For all temperatures, energy flows from O3* to Ar. The vibrational energy transfer, relative to kBT, is very small below 500 K, but gradually increases towards high temperatures. The relative rotational energy transfer, on the other hand, monotonously decreases with T; around 1100 K it falls below the relative vibrational energy transfer. Thermally averaged cross sections for vibrational and rotational energy transfers are also calculated. The implications for the stabilization of ozone complexes in the energy transfer model are discussed.
Study of the Ar metastable atom population in a hollow cathode discharge by means of a hybrid model and spectrometric measurements
Authors: Baguer N. , Bogaerts A. , Donko Z. , Gijbels R. , Sadeghi N.
Published: June 2005

The role of the metastable Ar atoms in a 1-cm-diameter cylindrical hollow cathode discharge (HCD) is studied self-consistently based on a hybrid model and experimental measurements in the pressure range of 0.3–1Torr and currents of 1–10mA. The model comprises submodels based on the principles of Monte Carlo and fluid simulations. The Monte Carlo model describes the movement of the fast electrons, fast Ar and Cu atoms, and fast Ar+ and Cu+ ions as particles, while in the fluid model, the slow electrons, Ar+, Cu+ ions, Cu, and Ar metastable atoms are treated as a continuum. The population of the two metastable states within the 3p54s configuration (P23 and P03) were combined into one collective level, for which the continuity equation was written. Typical calculation results are, among others, the two-dimensional profiles of the production and the loss rates of Ar metastable atoms, as well as the metastable atom densities and fluxes throughout the complete HCD. Moreover, the calculated radial profiles (averaged over the axial direction) of the Ar metastable atom density are compared with experimental radial density profiles recorded by laser absorption spectroscopy. The relative importance of the different processes determining the Ar metastable population is analyzed, as well as the influence of pressure and voltage on them. Experimental results evidence the presence of the metastable atom production source at the cathode surface, probably originating from fast Ar+ ions and Ar atoms impinging on it. Comparison between experimental and calculated Ar metastable atom densities shows a good agreement at low pressures, but at 1Torr the calculated values differ by a factor of 2 from the measured ones. Several possible explanations for this discrepancy are discussed.
Annealing effect of ultrathin Ag films on Ni∕Pt(111)
Authors: Su C. W. , Yo H. Y. , Chen Y. J. , Shern C. S.
Published: June 2005

The epitaxial growth and alloy formation of Ag-capped layer on Ni∕Pt(111) surface were investigated using Auger electron spectroscopy, ultraviolet photoelectron spectroscopy, and low-energy electron diffraction. The growth of Ag on one ML Ni∕Pt(111) transforms from layer-by-layer mode into three-dimensional island mode after the growth of one atomic monolayer of Ag. The starting temperature for the alloy formation of Ni–Pt is dependent of the thickness of Ni films. The interface compositions after the high-temperature annealing were studied with the depth-profile analysis of Ar ion sputtering.
Modeling of transient nonequilibrium phenomena in an inductively coupled plasma under pulsed power conditions
Authors: Ye R. , Ishigaki T.
Published: June 2005

A time-dependent two-temperature model is developed to simulate the behavior of an argon radio frequency plasma under transient nonequilibrium conditions, with emphasis to shed light on the temporal and spatial evolution of the nonequilibrium phenomena occurring in pulsed power plasmas. The results show that the effects of changes in input power on the thermal nonequilibrium and the ionization nonequilibrium are most noticeable at the early stages of pulse on and off. The observed deviation from thermal equilibrium during pulsation is more pronounced in the fringes of the plasma and near the wall of the torch. In the central region, the influence is less significant and the plasma remains in a quasilocal thermal equilibrium state. The temporal evolution of the ionization nonequilibrium does not keep pace with that of the thermal nonequilibrium, and the relaxation process of the electron number density is slower and smoother. The effects of operating conditions on the transient behavior of the nonequilibrium situations under pulsed power conditions are also examined. It indicates that, for materials processing, a pulse duration between 2 and 10 ms is adequate for rf plasmas operated in pulse-modulated modes.
Beamline electrostatic levitator for in situ high energy x-ray diffraction studies of levitated solids and liquids
Authors: Gangopadhyay A. K. , Lee G. W. , Kelton K. F. , Rogers J. R. , Goldman A. I. , Robinson D. S. , Rathz T. J. , Hyers R. W.
Published: June 2005

Determinations of the phase formation sequence, crystal structures and the thermo-physical properties of materials at high temperatures are hampered by contamination from the sample container and environment. Containerless processing techniques, such as electrostatic (ESL), electromagnetic, aerodynamic, and acoustic levitation, are most suitable for these studies. An adaptation of ESL for in situ structural studies of a wide range of materials using high energy (30–130keV) x rays at a synchrotron source is described here. This beamline ESL (BESL) allows the in situ determination of the atomic structures of equilibrium solid and liquid phases, undercooled liquids and time-resolved studies of solid-solid and liquid-solid phase transformations. The use of area detectors enables the rapid acquisition of complete diffraction patterns over a wide range (0.5–14Å−1) of reciprocal space. The wide temperature range (300–2500K), containerless processing environment under high vacuum (10−7–10−8Torr), and fast data acquisition capability, make BESL particularly well suited for phase stability studies of high temperature solids and liquids. An additional, but important, feature of BESL is the capability for simultaneous measurements of a host of thermo-physical properties including the specific heat, enthalpy of transformation, solidus and liquidus temperatures, density, viscosity, and surface tension, all on the same sample during the structural measurements.
Hybrid correlation models based on active-space partitioning: Correcting second-order Møller–Plesset perturbation theory for bond-breaking reactions
Authors: Bochevarov Arteum D. , Sherrill C. David
Published: June 2005

Møller–Plesset second-order (MP2) perturbation theory breaks down at molecular geometries which are far away from equilibrium. We decompose the MP2 energy into contributions from different orbital subspaces and show that the divergent behavior of the MP2 energy comes from the excitations located within a small (or sometimes even the minimal) active space. The divergent behavior of the MP2 energy at large interfragment distances may be corrected by replacing a small number of terms by their more robust counterparts from coupled-cluster (CCSD) theory. We investigated several schemes of such a substitution, and we find that a coupling between the active-space CCSD and the remaining MP2 amplitudes is necessary to obtain the best results. This naturally leads us to an approach which has previously been examined in the context of cost-saving approximations to CCSD for equilibrium properties by Nooijen [J. Chem. Phys. 111, 10815 (1999)]. The hybrid MP2–CCSD approach, which has the same formal scaling as conventional MP2 theory, provides potential curves with a correct shape for bond-breaking reactions of BH, CH4, and HF. The error of the MP2–CCSD method (measured against full configuration-interaction data) is smaller than that of MP2 at all interfragment separations and is qualitatively similar to that of full CCSD.
Gas temperature of capacitance spark discharge in air
Authors: Ono Ryo , Nifuku Masaharu , Fujiwara Shuzo , Horiguchi Sadashige , Oda Tetsuji
Published: June 2005

Capacitance spark discharge has been widely used for studying the ignition of flammable gas caused by electrostatic discharge. In the present study, the gas temperature of capacitance spark discharge is measured. The gas temperature is an important factor in understanding the electrostatic ignition process because it influences the reaction rate of ignition. Spark discharge is generated in air with a pulse duration shorter than 100ns. The discharge energy is set to 0.03–1mJ. The rotational and vibrational temperatures of the N2 molecule are measured using the emission spectrum of the N2 second positive system. The rotational and vibrational temperatures are estimated to be 500 and 5000K, respectively, which are independent of the discharge energy. This result indicates that most of the electron energy is consumed in the excitation of vibrational levels of molecules rather than the heating of the gas. The gas temperature after discharge is also measured by laser-induced fluorescence of OH radicals. It is shown that the gas temperature increases after discharge and reaches approximately 1000K at 3μs after discharge. Then the temperature decreases at a rate in the range of 8–35K∕μs depending on the discharge energy.
Analysis of γγ directional correlation data taken with a multi-detector system
Authors: Zevallos-Chávez J. Y. , Genezini F. A. , Zamboni C. B. , da Cruz M. T. F. , Martins M. N. , Vanin V. R. , Guimarães-Filho Z. O. , Pascholati P. R.
Published: June 2005

When performed with a multi-detector system, γγ directional correlation measurements need to be corrected differently for each independent detector pair, especially when those detectors have different active volumes and subtend different solid angles with respect to the radioactive source. We show here a method, which is suitable for setups containing dissimilar detectors. Successful tests were made for four γγ cascades, from Co60, Ba133 and Eu152.
Analytically continued Fock space multireference coupled-cluster theory: Application to the Πg2 shape resonance in e-N2 scattering
Authors: Sajeev Y. , Santra Robin , Pal Sourav
Published: June 2005

The technique of Fock space multireference coupled-cluster (FSMRCC) is applied for the first time to the correlated calculation of the energy and width of a shape resonance in an electron-molecule collision. The procedure is based upon combining a complex absorbing potential with FSMRCC theory. Accurate resonance parameters are obtained by solving a small non-Hermitian eigenvalue problem. The potential-energy curve of the Πg2 state of N2− is calculated using the FSMRCC and multireference configuration-interaction (MRCI) level of theories. Comparison with the single-determinant Hartree–Fock theory indicates that correlation effects are important in determining the behavior of the resonance state.
Extensions of representations of the CAR algebra to the Cuntz algebra O2—the Fock and the infinite wedge
Authors: Kawamura Katsunori
Published: June 2005

Fermions are expressed by polynomials of canonical generators of the Cuntz algebra O2 and they generate the U(1)-fixed point subalgebra A≡O2U(1) of O2 by the canonical gauge action. We extend the Fock and the infinite wedge representations of A to permutative representations of O2. By these extensions, the boson-fermion correspondence is rewritten by canonical generators of O2.
Dynamics of lithium ions in calcium bismuthate glasses
Authors: Dutta A. , Ghosh A.
Published: June 2005

Ion transport in Li2O–CaO–Bi2O3 glasses has been studied in the frequency range from 10Hzto2MHz and in the temperature range from 293to543K. The variation of the dc conductivity and the activation energy of these glasses with composition have been compared with those of binary lithium bismuthate glasses. It has been observed that the introduction of CaO in small amount does not effect the dc conductivity and the corresponding activation energy, but the larger amount of CaO changes them to some extent. The frequency-dependent conductivity has been studied using both conductivity and modulus formalisms. The values of the nonexponential parameter and frequency exponent are found to differ for the Li2O–CaO–Bi2O3 glasses from those for the binary Li2O–Bi2O3 glasses. The concentration of mobile Li+ ions does not change appreciably with the change in the Li2O as well as CaO content in the compositions. The increasing amount of CaO in the glass compositions for fixed Li2O content points out that CaO dilates the glass network, enhancing the migration of Li+ ions.
Ponderomotive electron acceleration using surface plasmon waves excited with femtosecond laser pulses
Authors: Irvine S. E. , Elezzabi A. Y.
Published: June 2005

We report on the ponderomotive acceleration of electrons using surface plasmon (SP) waves launched on Ag and Au films. High-energy electrons, up to 2 keV, are generated in the high spatial gradient of the SP field. Acceleration gradients of ∼8GeV∕m are produced using 30GW∕cm2, 800 nm amplified 30 fs laser pulses. Investigation of the photoemission characteristics of these metal films reveals a distinct transition between the multiphoton regime and a laser-induced field emission regime. Results of the experiment are in good agreement with those predicted with test particle code, which is based on finite-difference time-domain simulation and incorporates the Drude dielectric function and photoemission properties of the metallic films.