bluuebunny/crossref_metadata_2025 huggingface dataset:
On a model for the temporal oscillations in the Belousov-Zhabotinsky reaction
Authors: Murray J. D.
Published: February 2004

The detailed chemical mechanism for the temporal oscillations in the Belousov-Zhabotinsky reaction, which was suggested by Field, Körös, and Noyes [J. Am. Chem. Soc. 94, 8649 (1972)], has been reconsidered by Field and Noyes [J. Chem. Phys. 60, 1877(1974)], who suggest a simplified five step scheme to explain the chemical behavior that is observed. Their reaction equations are discussed here, and a method for finding bounds for closed stable trajectories in the phase space of the dimensionless concentrations of the HBrO2, Br−, and Ce(IV) is given. Simple bounds are obtained and compared with the numerical solution found by Field and Noyes. The existence of such bounds proves that the equations suggested by Field and Noyes are globally stable for large enough disturbances from the steady state and provide necessary conditions for the existence of bounded temporal oscillations.
Light scattering of spheroids. III. Depolarization of the scattered light
Authors: Heller W. , Nakagaki M.
Published: February 2004

The effect of the magnetic dipole and electric quadrupole upon the depolarization of light scattered by spheroids that are not very small compared to the wavelength is investigated. It is found that the three degrees of depolarization, ρu, ρσ, and ρπ, differ appreciably in their response to changes in the parameter values α (related to spheroid size), p (axial ratio), and m (relative refractive index). These differences should allow one to determine both molecular weight and physical dimensions of nonspherical macromolecular scatterers and the volume and dimensions of compact, nonspherical, colloidal particles conclusively from depolarization measurements within a wide dimensional range not accessible to the classical Rayleigh-Gans theory of depolarization.
Fluctuations in chemical reactions around the steady states
Authors: Saitô Nobuhiko
Published: February 2004

Birth-and-death type master equations for linear chemical reactions in closed and open systems are solved to discuss the properties of fluctuations. For nonlinear chemical reactions the generating functions of the probability of number fluctuation are usually second order differential equations, and a method for obtaining the moments of fluctuations is presented with applications to simple examples. The deterministic kinetic equation is valid for large systems and the second moments are the same as those of Poisson distributions in open systems treated here, while for the higher moments this is not always the case.
Statistical thermodynamics of nucleation. Theory of homogeneous condensation
Authors: Derjaguin B. V.
Published: February 2004

Essential difficulties of the nucleation theory have been considered, especially those of calculating the number of droplets forming per unit time ν during the condensation of vapor. A more general statistical method using the Gibbs' grand ensemble as the basis has been shown in the case of moderate supersaturations to allow, in a very strict and general manner, the determination of ν, a pre-exponential factor inclusive. For a particular case of rarefied vapor, the pre-exponential factor coincides with that found by Frenkel.
Electron correlation in excited states and term splittings in the carbon-I isoelectronic sequence
Authors: Sinanoğlu Oktay , Skutnik Bolesh J.
Published: February 2004

The theory of electron correlation in excited states is used in evaluating spectroscopic quantities exemplified by the calculation of term level splittings among excited states of the carbon-I isoelectronic sequence. Agreement with experiment is generally better than 10%, which is 4–25 times better than that achieved by conventional Hartree-Fock (HF) calculations and 2–10 times better than that achieved by standard multiconfigurational HF calculations.
Energy transfer from the resonance states Ar(1P1) and Ar(3P1) to ethylene
Authors: Hurst G. S. , Wagner E. B. , Payne M. G.
Published: February 2004

A study has been made of the quenching of the 1P1 and 3P1 resonance states of the argon atom by ethylene using a resonance fluorescence technique. Excited atoms were created by a pulsed beam of 2-MeV protons. The measured values of the rate constants are 10.3×10−10 and 5.6×10−10 cm3 molecule−1 · sec−1 for the 1P1 and 3P1 states, respectively. These compare with the calculated values of 10.3×10−10 and 5.4×10−10 cm3 molecule−1 · sec−1 for the respective states using the theory of Watanabe and Katsuura.
Distorted atoms in molecules (DAM) model for ordinary covalent molecules. II. Force constants for H2, LiH, and BeH+ as well as medium range repulsion of H + H(3Σu) and He + He
Authors: Kirtman B. , Chang S. Y. , Scott W. R.
Published: February 2004

The distorted atoms in molecules valence-bond model is used to determine potential energy curves near equilibrium for H2, LiH, and BeH+ as well as in the medium range repulsive region for H+H(3Σu) and He+He. It is shown that the force constants that we obtain by numerical differentiation are, in principle, equal to those that would be found by double perturbation theory. The usual (single) perturbation method, however, contains a first-order error. Our values for all force constants including the anharmonic ones lie within 10% of experiment except for k2 of BeH+. The somewhat larger (20%) error in the latter case is probably due to omission of ionic-covalent mixing.
What is the best expression of the second-order sum-over-state perturbation energy based on the Hartree-Fock wavefunction?
Authors: Nakatsuji Hiroshi
Published: February 2004

We have improved in a stepwise manner the second-order sum-over-state perturbation energy which is written in the infinite sum over singly excited configurations based on the Hartree-Fock (HF) zeroth-order wavefunction. Firstly, the conventional equation [Eq. (10)] is shown to be dependent on the unitary transformations among singly excited configurations. The best unitary transformation gives the Tamm-Dancoff (or singly excited configuration interaction) approximation of the excited states. The resultant equation [Eq. (25)] includes in a simple form all of the coupling terms between different singly excited configurations. As a restrictive special case, this unitary transformation leads to the modified HF orbitals of Silverstone-Huzinaga and Morokuma-Iwata. Secondly, it is shown that the second-order energy of the coupled HF theory can also be written in a simple sum-over-state perturbation formula. The resultant equation [Eq. (50)] does not require an iterative solution. Moreover, it is shown that this is the best possible expression of the second-order energy based on the HF zeroth-order wavefunction. As a restrictive special case, this treatment produces new improved modified HF operators which are thought to be superior to those hitherto given.
Geometric double-perturbation expansion of the coupled Hartree-Fock second-order energy
Authors: Nakatsuji H. , Musher J. I.
Published: February 2004

The second-order energy of the coupled perturbed Hartree-Fock (CHF) theory is expanded explicitly into the sum with respect to the electron-correlation corrections. In a matrix form, the expansion is exactly geometric. The correlation effect included in the CHF theory has two origins: one represents the so-called first-order correlation energies intrinsic to the unperturbed ground and excited states, and the other represents the correlation effect induced by the external perturbation. The matrix geometric expansion reduces under some approximation to an ordinary scalar geometric series. This gives a basis for the geometric approximation of the CHF energy proposed empirically by Schulman and Musher. Exactly the same arguments also apply to the second-order energy of the singly excited CI method, simply by neglecting the perturbation-induced correlation effect.
Kinetics and thermodynamics of association reactions of CO+• and HCO+ with CO and of N2+• and N2H+ with N2 between 120 and 650 °K
Authors: Meot-Ner M. , Field F. H.
Published: February 2004

We conducted a comparative study of the kinetic and thermodynamic parameters of the association reactions of the radical ions CO+• and N2+• and of the even electron ions HCO+ and N2H+ with Co and N2, respectively. The studies were conducted by the technique of pulsed high-pressure mass spectrometry. We obtained the values of ΔH=11.7 kcal/mole and ΔS=20.9 e.u. for the dissociation of the complex HCO+ · CO and ΔH=14.5 kcal/mole, ΔS=20.4 e.u. for the dissociation of the complex N2H+ · N2. Both enthalpies are significantly smaller than the binding energies in the analogous complexes of the radical ions CO+• and N2+•. We measured the rate constants for the association reaction leading to these ion-molecule complexes and obtained the following results: HCO++2CO→HCO+ · CO+CO, k328=0.61×10−29 cc2/molecule2 · sec; N2H++2N2→N4H++N2, k329=0.54×10−29; CO++2CO → C2O2+•+CO, k328=19.8×10−29 and N2+• + 2N2 → N4+•+ N2, k328=7.9×10−29. A direct correlation between the thermodynamic and kinetic parameters is seen in that the more exothermic reactions of the radical ions proceed significantly faster than the less exothermic reactions of the even-electron ions. The temperature dependences of the reactions reported over the wide temperature ranges applied demonstrates unequivocally that the rate constants follow the functional form k =CTn. n was found to be ≈−1.5 for the reactions of the radical ions, and ≈−3 for the reactions of the even-electron ions. A small negative deviation from linearity in the plots of log k vs log T for some of the reactions indicates that a small positive activation energy (≤0.2 kcal/mole) may be present in these highly exothermic reactions. The meaning of the results of our kinetic studies are discussed in the framework of energy-transfer theory and transition-state theory concepts.
Vibrational excitation of HCl by electron impact
Authors: Center R. E. , Chen Hao-Lin
Published: February 2004

Measurements have been made of the vibrational excitation rate constant of HCl excited by electron impact. The experiments were performed in a uniform electron beam sustained discharge over the range of average electron energies from 0.8 to 1.7 eV. A mean value of (1.2±0.4)×10−8 cm3/sec was obtained corresponding to a cross section of several Å2. It was also determined that the vibrational excitation by electron impact was predominantly to the first vibrational level with only 20% probability of exciting the second or higher levels.
Kinetics of the reactions of N2H+, N4+, and N3+ with H2O in the gas phase
Authors: Bierbaum Veronica M. , Kaufman Frederick
Published: February 2004

The flowing afterglow technique has been used to study the bimolecular reactions of water vapor with three nitrogen-containing ions, N2H+, N4+, and N3+ at 296°K. The N2H+ undergoes a fast proton transfer reaction with water (k=2.77×10−9 cm3 sec−1), N4+ rapidly charge transfers with water (k=1.88×10−9 cm3 sec−1), while N3+ participates in a slower rearrangement reaction (k=2.57×10−10 cm3 sec−1) to form the product ion H2NO+. The experimental technique is briefly reviewed, the production processes of the reactant ions are described, and the data are discussed and compared with other experimental results.
Higher-order long-range interactions between rare gas and hydrogen atoms
Authors: Stwalley William C.
Published: February 2004

Theoretical values for the multipole polarizabilities and like atom van der Waals coefficients C6, C8, and C10 are used with the Kramer-Herschbach combination rules to calculate C8 and C10 for unlike atoms in the set (H, He, Ne, Ar, Kr, Xe). It is argued that in most cases these values are the most accurate available and should be good to ∼±10%.
Interactions between intracellular Na+ levels and saxitoxin production in Cylindrospermopsis raciborskii T3
Authors: Pomati Francesco , Rossetti Carlo , Manarolla Gianluca , Burns Brendan P. , Neilan Brett A.
Published: February 2004

Saxitoxin (STX) is the most potent representative among the paralytic shellfish poisoning (PSP) toxins, which are highly selective Na+channel-blocking alkaloids. This study investigated, in cultures of the cyanobacteriumCylindrospermopsis raciborskiiT3, the effects of pH, salt, amiloride and lidocaine hydrochloride on total cellular levels of Na+and K+ions and STX accumulation. Both Na+levels and intracellular STX concentrations increased exponentially in response to rising alkalinity. NaCl inhibited cyanobacterial growth at a concentration of 10 mM. In comparison with osmotically stressed controls, however, NaCl promoted STX accumulation in a dose-dependent manner. A correlation was seen in the time-course of both total cellular Na+levels and intracellular STX for NaCl, amiloride and lidocaine exposure. The increase in cellular Na+induced by NaCl at 10 mM was coupled with a proportional accumulation of STX. The two Na+channel-blocking agents amiloride and lidocaine had opposing effects on both cellular Na+levels and STX accumulation. Amiloride at 1 mM reduced ion and toxin concentrations, while lidocaine at 1 μM increased the total cellular Na+and STX levels. The effects of the channel-blockers were antagonistic and dependent on an alkaline pH. The results presented suggest that, inC. raciborskiiT3, STX is responsive to cellular Na+levels. This may indicate that either STX metabolism or the toxin itself could be linked to the maintenance of cyanobacterial homeostasis. The results also enhance the understanding of STX production and the ecology of PSP toxin-producing cyanobacteria.
The fate of extracellular proteins tagged by the SsrA system of Bacillus subtilis
Authors: Kolkman Marc A. B. , Ferrari Eugenio
Published: February 2004

In bacteria, SsrA, a highly conserved RNA molecule, functions in a mechanism meant to rescue stalled ribosomes. In this process, a peptide tag encoded by SsrA is cotranslationally added to truncated polypeptides, thereby targeting these molecules for proteolytic degradation, at least when they stay inside the cell. This study examined the fate of two extracellular proteins that were tagged by the SsrA system of Bacillus subtilis. Gene constructs encoding human interleukin-3 (hIL-3) fused to a signal peptide and B. subtilis
α-amylase, both lacking an in-frame stop codon, were used as models to achieve ribosome stalling and activation of the SsrA system. Introduction of these gene constructs into B. subtilis led to tagging of the gene products by SsrA RNA. The tagged protein products bound to antibodies that were raised against the proteolysis tag encoded by B. subtilis SsrA [(A)GKTNSFNQNVALAA]. The apolar C-terminal SsrA-tag does not function as a specific signal for proteolytic degradation of SsrA-tagged amylase directly after trans-translation or during the secretion process. Also, SsrA-tagged amylase appeared to be very stable once outside the cell. In contrast, hIL-3 molecules tagged with the native, apolar SsrA-tag were considerably less stable than hIL-3 molecules that received a negatively charged control tag. Not one specific protease, but several non-specific proteases seem to play a role in the rapid degradation of SsrA-tagged hIL-3. The polarity of the C-terminus of heterologous hIL-3 protein proved to be an important determinant for protein stability when produced by B. subtilis. As observed previously in Escherichia coli and B. subtilis, SsrA tagging also occurs frequently in normally growing Gram-positive bacilli and it appears that intracellular proteins are the predominant natural substrates of SsrA.
Regulation of RcsA by the ClpYQ (HslUV) protease in Escherichia coli
Authors: Kuo Mei-Shiue , Chen Kuei-Peng , Wu Whi Fin
Published: February 2004

Escherichia coliClpYQ protease and Lon protease possess a redundant function for degradation of SulA, a cell division inhibitor. An experimental cue implied that the capsule synthesis activator RcsA, a known substrate of Lon, is probably a specific substrate for the ClpYQ protease. This paper shows that overexpression of ClpQ and ClpY suppresses the mucoid phenotype of alonmutant. Since thecpsB(wcaB) gene, involved in capsule synthesis, is activated by RcsA, the reporter constructcpsB–lacZwas used to assay forβ-galactosidase activity and thus follow RcsA stability. The expression ofcpsB–lacZwas increased in double mutants oflonin combination withclpQor/andclpYmutation(s) compared with the wild-type orlonsingle mutants. Overproduction of ClpYQ or ClpQ decreasedcpsB–lacZexpression. Additionally, a PBAD–rcsAfusion construct showed quantitatively that an inducible RcsA activatescpsB–lacZexpression. The effect of RcsA oncpsB–lacZexpression was shown to be influenced by the ClpYQ activities. Moreover, arcsARed–lacZtranslational fusion construct showed higher activity of RcsARed–LacZ in aclpQ clpYstrain than in the wild-type. By contrast, overproduction of cellular ClpYQ resulted in decreasedβ-galactosidase levels of RcsARed–LacZ. Taken together, the data indicate that ClpYQ acts as a secondary protease in degrading the Lon substrate RcsA.
Expression and complexity of the PRT1 multigene family of Pneumocystis carinii
Authors: Ambrose H. E. , Keely S. P. , Aliouat E. M. , Dei-Cas E. , Wakefield A. E. , Miller R. F. , Stringer J. R.
Published: February 2004

Pneumocystis carinii has a multigene family, PRT1, that encodes proteins with homology to KEX2-like proteases. PRT1 genes cluster with MSG genes near the telomeres and, like MSG, PRT1 proteins seem to be surface-expressed. The clustering of PRT1 and MSG genes suggested that expression of the two multigene families might be coordinated. Studying gene expression in P. carinii has been hampered by the lack of a culture system, and by lack of clonality in P. carinii populations in naturally infected rats, the host of this fungus. Heterogeneity can be reduced, however, by low-dose intratracheal inoculation, which can produce P. carinii populations dominated by organisms derived from a single progenitor. To study PRT1 expression, nude rats were inoculated with approximately 10 P. carinii each. The clonality of the P. carinii populations from inoculated rats was assessed by analysis of the UCS locus, a site in the genome that is known to be very heterogeneous in naturally infected rats, but nearly homogeneous in rats infected by low-dose intratracheal inoculation. Each of the populations had the same MSG gene at the UCS locus in at least 80 % of the organisms. To investigate PRT1 gene expression, RNA was amplified using primers that amplify numerous PRT1 genes. Seventy-four cloned cDNAs were sequenced, including at least 12 clones from each population of P. carinii. Many differently expressed PRT1 sequences were identified in each population, and a total of 45 different sequences were detected. However, the same PRT1 sequence was present in 15 of 74 plasmids and was found in 3 of the 5 P. carinii populations, suggesting that some PRT1 genes may be either more commonly expressed or expressed at a higher level. These data show that many members of the PRT1 gene family can be expressed in populations of P. carinii derived from few progenitors and suggest that the regulation of this family is different from that governing expression of the MSG gene family.
Absence of Yersinia pestis-specific DNA in human teeth from five European excavations of putative plague victims
Authors: Gilbert M. Thomas P. , Cuccui Jon , White William , Lynnerup Niels , Titball Richard W. , Cooper Alan , Prentice Michael B.
Published: February 2004

This study reports the results of a collaborative study undertaken by two independent research groups to (a) confirm recent PCR-based detection of Yersinia pestis DNA in human teeth from medieval plague victims in France, and (b) to extend these observations over five different European burial sites believed to contain plague victims dating from the late 13th to 17th centuries. Several different sets of primers were used, including those previously documented to yield positive results on ancient DNA extracts. No Y. pestis DNA could be amplified from DNA extracted from 108 teeth belonging to 61 individuals, despite the amplification of numerous other bacterial DNA sequences. Several methods of extracting dentine prior to the DNA extraction were also compared. PCR for bacterial 16S rDNA indicated the presence of multiple bacterial species in 23 out of 27 teeth DNA extracts where dentine was extracted using previously described methods. In comparison, positive results were obtained from only five out of 44 teeth DNA extracts for which a novel contamination-minimizing embedding technique was used. Therefore, high levels of environmental bacterial DNA are present in DNA extracts where previously described methods of tooth manipulation are used. To conclude, the absence of Y. pestis-specific DNA in an exhaustive search using specimens from multiple putative European plague burial sites does not allow us to confirm the identification of Y. pestis as the aetiological agent of the Black Death and subsequent plagues. In addition, the utility of the published tooth-based ancient DNA technique used to diagnose fatal bacteraemias in historical epidemics still awaits independent corroboration.
Transcriptome and proteome analysis of Bacillus subtilis gene expression in response to superoxide and peroxide stress
Authors: Mostertz Jörg , Scharf Christian , Hecker Michael , Homuth Georg
Published: February 2004

The Gram-positive soil bacteriumBacillus subtilisresponds to oxidative stress by the activation of different cellular defence mechanisms. These are composed of scavenging enzymes as well as protection and repair systems organized in highly sophisticated networks. In this study, the peroxide and the superoxide stress stimulons ofB. subtiliswere characterized by means of transcriptomics and proteomics. The results demonstrate that oxidative-stress-responsive genes can be classified into two groups. One group encompasses genes which show similar expression patterns in the presence of both reactive oxygen species. Examples are members of the PerR and the Fur regulon which were induced by peroxide and superoxide stress. Similarly, both kinds of stress stimulated the activation of the stringent response. The second group is composed of genes primarily responding to one stimulus, like the members of the SOS regulon which were particularly upregulated in the presence of peroxide, and many genes involved in sulfate assimilation and methionine biosynthesis which were only induced by superoxide. Several genes encoding proteins of unknown function could be assigned to one of these groups.
Identification of proteins in the exosporium of Bacillus anthracis
Authors: Redmond Caroline , Baillie Leslie W. J. , Hibbs Stephen , Moir Arthur J. G. , Moir Anne
Published: February 2004

Spores of Bacillus anthracis, the causative agent of anthrax, possess an exosporium. As the outer surface layer of these mature spores, the exosporium represents the primary contact surface between the spore and environment/host and is a site of spore antigens. The exosporium was isolated from the endospores of the B. anthracis wild-type Ames strain, from a derivative of the Ames strain cured of plasmid pXO2−, and from a previously isolated pXO1−, pXO2− doubly cured strain, B. anthracis UM23Cl2. The protein profiles of SDS-PAGE-separated exosporium extracts were similar for all three. This suggests that avirulent variants lacking either or both plasmids are realistic models for studying the exosporium from spores of B. anthracis. A number of loosely adsorbed proteins were identified from amino acid sequences determined by either nanospray-MS/MS or N-terminal sequencing. Salt and detergent washing of the exosporium fragments removed these and revealed proteins that are likely to represent structural/integral exosporium proteins. Seven proteins were identified in washed exosporium: alanine racemase, inosine hydrolase, ExsF, CotY, ExsY, CotB and a novel protein, named ExsK. CotY, ExsY and CotB are homologues of Bacillus subtilis outer spore coat proteins, but ExsF and ExsK are specific to B. anthracis and other members of the Bacillus cereus group.
Multiplication of an ancestral gene encoding secreted fungalysin preceded species differentiation in the dermatophytes Trichophyton and Microsporum
Authors: Jousson Olivier , Léchenne Barbara , Bontems Olympia , Capoccia Sabrina , Mignon Bernard , Barblan Jachen , Quadroni Manfredo , Monod Michel
Published: February 2004

Dermatophytes are human and animal pathogenic fungi which cause cutaneous infections and grow exclusively in the stratum corneum, nails and hair. In a culture medium containing soy proteins as sole nitrogen source a substantial proteolytic activity was secreted byTrichophyton rubrum,Trichophyton mentagrophytesandMicrosporum canis. This proteolytic activity was 55–75 % inhibited byo-phenanthroline, attesting that metalloproteases were secreted by all three species. Using a consensus probe constructed on previously characterized genes encoding metalloproteases (MEP) of the M36 fungalysin family inAspergillus fumigatus,Aspergillus oryzaeandM. canis, a five-memberMEPfamily was isolated from genomic libraries ofT. rubrum,T. mentagrophytesandM. canis. A phylogenetic analysis of genomic and protein sequences revealed a robust tree consisting of five main clades, each of them including aMEPsequence type from each dermatophyte species. EachMEPtype was remarkably conserved across species (72–97 % amino acid sequence identity). The tree topology clearly indicated that the multiplication ofMEPgenes in dermatophytes occurred prior to species divergence. In culture medium containing soy proteins as a sole nitrogen source secreted Meps accounted for 19–36 % of total secreted protein extracts; characterization of protein bands by proteolysis and mass spectrometry revealed that the three dermatophyte species secreted two Meps (Mep3 and Mep4) encoded by orthologous genes.
Light-regulated asexual reproduction in Paecilomyces fumosoroseus
Authors: Sánchez-Murillo Rosa Icela , de la Torre-Martínez Mayra , Aguirre-Linares Jesús , Herrera-Estrella Alfredo
Published: February 2004

The entomopathogenic fungus Paecilomyces fumosoroseus has been successfully used in the control of several insect pests. Asexually produced spores (conidia) are the means for dispersal and transmission of the entomopathogen; upon contact with the insect cuticle they germinate and penetrate the host. In model fungal systems it has been found that phototropism, resetting of the circadian rhythm, the induction of carotenogenesis and the development of reproductive structures are controlled by blue light. The effect of light quality on conidial yield of P. fumosoroseus was investigated. Incubation in total darkness resulted in continued vegetative growth and lack of reproductive structures. In contrast, growth of the fungus in continuous illumination or under a night–day regime resulted in prolific formation of conidiophores bearing abundant mature conidia. Conidiation was photoinduced in competent mycelia by a single pulse of blue light and colonies were competent only after they had grown at least 72 h under total darkness. The fluence–response curves generated with blue light indicated that the minimal fluence required for the photomorphogenetic response was 180 μmol m−2 and the half-maximal response was at 400 μmol m−2. A fluence of 540 μmol m−2 was enough to saturate the system, inducing the maximum production of 2·12×108 conidia per colony. Higher light intensities markedly decreased conidiation, suggesting the occurrence of a process of adaptation. The authors propose the existence of a dual light-perception system with at least two photoreceptors in P. fumosoroseus, one promoting and one inhibiting conidiation.
Deregulation of Listeria monocytogenes virulence gene expression by two distinct and semi-independent pathways
Authors: Milenbachs Lukowiak Andrea , Mueller Kimberly J. , Freitag Nancy E. , Youngman Philip
Published: February 2004

Expression of the major virulence cluster inListeria monocytogenesis positively regulated by the transcription factor PrfA and is influenced by several environmental factors, including the presence of readily metabolized carbohydrates such as cellobiose and glucose. Although little is understood about the mechanisms through which environmental factors influence expression of the PrfA regulon, evidence for structural and functional similarities of PrfA to the CRP-FNR family of regulatory proteins suggests the possibility that PrfA activity could be modulated by a small molecule ligand. The identity of components of the PrfA-associated regulatory pathway was sought through the isolation of mutants that exhibit high levels of PrfA-controlled gene expression in the presence of cellobiose or glucose. Here are described the properties and preliminary genetic analysis in two different genetic loci,gcrandcsr, both unlinked by general transduction to the major virulence cluster. A mutation ingcrderegulates the expression of PrfA-controlled genes in the presence of several repressing sugars and other environmental conditions, a phenotype similar to that of a G145S substitution in PrfA itself. A mutation in thecsrlocus, withincsrA, results in a cellobiose-specific defect in virulence gene regulation. Gene products encoded by thecsrlocus share homology with proteins involved in the sensing and transport ofβ-glucosides in other bacteria. Mutations in bothgcrandcsrare required for full relief of cellobiose-mediated repression of the PrfA regulon. These results suggest the existence of two semi-independent pathways for cellobiose-mediated repression and further reconcile conflicting reports in previous literature concerning the repressive effects of carbohydrates on virulence gene expression inL. monocytogenes.
Accessibility of the peptide backbone of protein ligands is a key specificity determinant in Candida albicans SRS adherence
Authors: Gaur Nand K. , Klotz Stephen A.
Published: February 2004

Candida albicans displays a high degree of specificity in selecting and adhering to targets in vivo. The features of target recognition are poorly understood and likely to involve more than the mere chemical composition of the ligand. Using an adherence assay in which protein and peptide ligands are covalently coupled to magnetic beads, the authors have previously described a new adherence mechanism in C. albicans, henceforth referred to as SRS (stable, reversible, specific) adherence. It was previously demonstrated that C. albicans and Saccharomyces cerevisiae expressing agglutinin-like sequence 5 protein (Als5p, previously referred to as Ala1p or Ala1/Als5p) adhere to peptides containing patches of threonine, serine and alanine residues when these are located in the free end of immobilized peptides. The interaction with protein ligands in SRS adherence predominantly involves the formation of hydrogen bonds. Accordingly, this interaction may occur (1) to the peptide backbone of the protein ligand or (2) to the amino acid side chain with an appropriate functional group. Evidence is provided that the primary interaction occurs with the peptide backbone and the secondary interaction occurs with the side chain. The primary interaction with the peptide backbone is sufficient for adherence to occur, whereas the secondary interaction with a side chain possessing an appropriate functional group stabilizes the interaction. In agreement with these results, it is also demonstrated that proteins lacking secondary and tertiary structure, wherein the peptide backbone is sterically accessible, interact with C. albicans and S. cerevisiae expressing Als5p. C. albicans Als proteins are resistant to denaturation by harsh conditions that kill the yeast cells. The proposed interactions in SRS adherence have striking similarities with those of the molecular chaperone Hsp70, which specifically binds to non-native proteins and resists denaturation.
Mouse skin passage of Streptococcus pyogenes results in increased streptokinase expression and activity
Authors: Rezcallah Myrna S. , Boyle Michael D. P. , Sledjeski Darren D.
Published: February 2004

The plasminogen activator streptokinase has been proposed to be a key component of a complex mechanism that promotes skin invasion byStreptococcus pyogenes. This study was designed to compareskagene message and protein levels in wild-type M1 serotype isolate 1881 and a more invasive variant recovered from the spleen of a lethally infected mouse. M1 isolates selected for invasiveness demonstrated enhanced levels of active plasminogen activator activity in culture. This effect was due to a combination of increased expression of theskagene and decreased expression of thespeBgene. ThespeBgene product, SpeB, was found to efficiently degrade streptokinasein vitro.
Characterization of cyst cell formation in the purple photosynthetic bacterium Rhodospirillum centenum
Authors: Berleman James E. , Bauer Carl E.
Published: February 2004

Rhodospirillum centenum is an anoxygenic photosynthetic bacterium that is capable of differentiating into several cell types. When grown phototrophically in liquid, cells exhibit a vibrioid shape and have a single polar flagellum. When grown on a solid surface, R. centenum will differentiate into rod-shaped swarm cells that display numerous lateral flagella. Upon starvation for nutrients, R. centenum also forms desiccation-resistant cysts. In this study, it was determined that R. centenum has heat- and desiccation-resistance properties similar to other cyst-forming species. In addition, microscopic analyses of the morphological changes that occur during cyst cell development were performed. It was observed that R. centenum typically forms multi-celled clusters of cysts that contain from four to more than 10 cells per cluster. It was also determined that cell density has a minor effect on the percentage of cyst cells formed, with cell densities of 105–107 cells per 5 μl spot yielding the highest percentage of cyst cells. The striking similarities between the life cycle of R. centenum and the life cycle exhibited by Azospirillum spp. are discussed.
Two Classes of the Cdh1-Type Activators of the Anaphase-Promoting Complex in Plants: Novel Functional Domains and Distinct Regulation[W]
Authors: Tarayre Sylvie , Vinardell Joseé Maria , Cebolla Angel , Kondorosi Adam , Kondorosi Eva
Published: February 2004

The Cdc20 and Cdh1/Fzr proteins are the substrate-specific activators of the anaphase-promoting complex (APC). In Medicago truncatula, the MtCcs52A and MtCcs52B proteins represent two subgroups of the Cdh1-type activators, which display differences in their cell cycle regulation, structure, and function. The ccs52A transcripts are present in all phases of the cell cycle. By contrast, expression of ccs52B is restricted to late G2-phase and M-phase, and its induced overexpression in BY2 cells inhibited mitosis. MtCcs52A is active in Schizosaccharomyces pombe and binds to the S. pombe APC, whereas MtCcs52B does not because of differences in the N-terminal region. We identified a new functional domain, the Cdh1-specific motif conserved in the Cdh1 proteins that, in addition to the C-box and the terminal Ile and Arg residues, was essential for the activity and required for efficient binding to the APC. Moreover, we demonstrate that cyclin-dependent kinase phosphorylation sites adjacent to the C-box may regulate the interaction with the APC. In the different plant organs, the expression of Mtccs52A and Mtccs52B displayed differences and indicated the involvement of the APC in differentiation processes.
Public awareness of patient rights, consent forms and advance statements
Authors: Dandy Julia
Published: February 2004

The subject of this study is the availability of, and access to, information concerning individuals’ end‐of‐life health situations. The sensitive issues surrounding this subject are considered in detail, and the restraints, primarily legal, placed upon information availability highlighted. Questionnaires and interviews were used to determine public and professional awareness of, and attitudes towards, the issues and were compared with a similar, albeit larger, survey conducted by the Department of Health. Complementary to this fieldwork, a review of current and proposed clinical policies, guidelines and legislation and of media commentary was undertaken. The study revealed much public confusion and ignorance about how people can influence the medical treatment they receive when seriously or terminally ill. The study revealed an urgent need for Government initiatives to provide more information on patient rights in relation to consent forms and advance statements.
diabCAL: evaluating computer‐aided learning for diabetes patient education
Authors: Berridge Emma‐Jane , Roudsari A.V.
Published: February 2004

The design and development of a computer‐aided learning tool for the education of patients with diabetes and for the training and support of practice nurses providing diabetes care have been previously reported. diabCAL is a broad and comprehensive learning tool, which can be accessed as a modular course or a desktop quick‐reference. Evaluation is central to the design process and can be formative, informing design and development throughout the lifecycle, or summative, assessing the value of the finished product. diabCAL was subject to rigorous evaluation at various stages during development, including: verification of curriculum content and structure, evaluation of navigation and evaluation of system content. A final hybrid formative‐summative evaluation assessed usability and acceptability of the system. Evaluations were conducted by technical experts and users, and findings of the final evaluation study, conducted by patients, confirmed that diabCAL was acceptable to most users – that is, interesting and perceived to be useful – even to those with little previous computer experience.
Some special nutritional properties of honey – a brief review
Authors: Al‐Qassemi Rasha , Robinson R.K.
Published: February 2004

Apart from highlighting the overall nutritional value of honey, this review draws attention to the potential importance of the oligosaccharide content of honey. The possible role of these compounds as prebiotics is emphasised, for a number of them have been found to stimulate species ofBifidobacteriumthat inhabit the human colon. It is suggested that the therapeutic properties of the anti‐oxidants in honey could be equally relevant, and the desirability of the growing practice of adding royal jelly to retail products is discussed briefly.
Career progression factors of Aboriginal executives in the Canada federal public service
Authors: Dwyer Rocky J.
Published: February 2004

The research examined the career progression factors of Aboriginal executives in Canada's federal public service to determine whether such factors as development opportunities, job assignments, education levels, mentoring, leadership experience, and networking increase the advancement of Aboriginal people to the executive category within the Canadian federal public service.
A factor approach to analysis of home maintenance outcomes and attributes of management successes in the owner‐occupied sector
Authors: Kangwa Joseph , Olubodun Femi
Published: February 2004

This paper seeks to explore and detect underlying relationships between identifiable attributes that are influential to successful outcomes of home maintenance activities. The study's approach is to identify, from the perspective of owner‐occupiers, the attributes that are influential on the successful outcomes of home maintenance activities. The study is primarily based on 186 questionnaire responses from a stratified random sample of owner‐occupiers taken from 12 local authority wards identified on the basis of a Ward Index of Multiple Deprivation. The intercorrelations among the attributes influential to the outcomes of home maintenance activities demanded the application of principal component analysis to determine the factors perceived to dictate home maintenance outcomes. This resulted in the extraction of nine significant factors, which combine to exert their influence on the quality of the maintenance activities in the owner‐occupied sector.
Post occupancy evaluation of a building employing windcatchers for summer ventilation
Authors: Elmualim Abbas Ali , Awbi H.B.
Published: February 2004

A combined windcatcher and light pipe (SunCatcher) was installed in the seminar room at the University of Reading, UK. Monitoring of indoor environment in real weather conditions was conducted to evaluate the application of windcatchers for natural ventilation. In addition, a subjective occupancy survey was undertaken. External weather conditions and internal indoor air quality indicators were recorded. The “tracer‐gas decay” method using SF6 was used to establish air change rate for various conditions. The results indicated that the ventilation rate achieved through the windcatcher depends on the difference between internal and external air temperatures, and on wind speed and direction, in agreement with other published work in the area. The indoor air quality parameters were found to be within acceptable levels when the windcatcher was in operation. The measured air change rate was between 1.5ac/h and 6.8ac/h. Occupants’ questionnaires showed 75 per cent satisfaction with the internal conditions and welcomed the installation of the systems in UK buildings.
Women executives: public and private sectors as sites of advancement?
Authors: Olsson Su , Pringle Judith K.
Published: February 2004

There are significantly more New Zealand women in senior management positions in the public sector than in private businesses. This study draws on the experiences and perceptions of 30 women executives who have considerable managerial experience in either sector. Success factors for the individual women are outlined before the cultures of the public and private sectors are described. Through the eyes of respondents, the public and private sectors have distinguishable organizational cultures; both of which provide parallel but different sites for advancement. The private sector businesses have a focus on competition and the public sector has a strong ethos of service, in spite of restructuring. The findings are discussed in the context of a country that has strong women leadership in the political sphere.
Strategic planning and information use: the role of institutional leadership in the community college
Authors: Petrides Lisa A.
Published: February 2004

Community college presidents face a daunting challenge in trying to manage and guide an organization that is, by its nature, decentralized and bureaucratic in its decision‐making processes, and at the same time they face external demands for greater accountability and internal demands for information. Although technological systems can accomplish these kinds of data collection tasks easily, the implementation of such systems is itself problematic. In many ways, implementing new information and technology systems, when done effectively, mirrors the open‐ended, cross‐functional deliberative processes of strategic planning. This paper discusses how institutional leaders at community colleges have used the implementation of strategic planning processes to break down information silos, increase collaboration among units, streamline information and work processes, and provide greater access to both academic and operational information. While this process may be time‐consuming and disorderly, it is a promising tool for bringing about organizational change.
Assessing your strategic alternatives from both a market position and core competence perspective
Authors: Leavy Brian
Published: February 2004

The practice of strategic decision‐making has two major perspectives to help managers create and maintain competitive advantage in the face of a range of business challenges. One stresses market position and the other core competence. (1) Market position – the positioning approach to strategy development is associated mainly with the work of Michael Porter; strategic choice is focused primarily on the structure of the industry and how it might be shaped to advantage. The aim is to establish a “privileged”/hard‐to‐replicate position in an industry that is difficult to enter. (2) Core competence – the competence‐led perspective is associated with the work of C.K. Prahalad and Gary Hamel; strategic choice focuses primarily on assessing which distinctive competences should be built, then considers the market opportunities that would exploit them best. It may be tempting to use one approach or the other because the market position and core competence approaches do create perspectives that see things very differently, and their analytical methodologies offer different guidance. But instead of picking one over the other, the astute strategist may be best served to test out both perspectives and generate a wider range of options. This is shown in the article’s illustrations of corporate strategy in the multi‐business firm and strategic renewal. In sum, looking at your business from both approaches will generate two sets of contrasting perspectives and options for action. For many firms, this binocular vision of the available strategic options will lead to a better result than if either perspective was used alone.
Occupational attainment through Lebanon’s higher education: using individual, societal, structural and gender factors as predictors
Authors: Nasser Ramzi , Abouchedid Kamal
Published: February 2004

This study sought to analyze university graduate job attainment in Lebanon through an individualist, societal and structuralist perspectives. Differences appeared between females and males on factors that predicted occupational attainment. In concert with neo‐patriarchal discourse increased occupational attainment among males was significantly predicted by fathers’ occupational status. The data reported that male and female university degree type produced higher occupational attainment between male and female graduates. Further analysis would seek to understand graduate attitudes towards their occupational attainment along individualist, societal and structural dimensions.
European Gender Mainstreaming: Promises and Pitfalls of Transformative Policy1
Authors: WOODWARD ALISON
Published: February 2004

abstract Gender mainstreaming requires a radical redefinition of policy values and practices. This initial discussion explores the way the mainstreaming approach attempts to change the definitions of the situation so that equality in gender relations becomes an element at the point of departure. Factors that may affect whether gender mainstreaming will become an institutional innovation include the extent to which there is a commitment to a gender mission, the level of sophistication in terms of gender and policy issues in the administrative setting, the level of resistance to gender equality, and the extent to which gender experts play a role. This article investigates the role of these contextual factors as related to experiences in the European Union Commission and several states in Northern Europe.
A Note on Paradoxes in Economics
Authors: Andreozzi Luciano
Published: February 2004

A paradox is a proposition in (alleged) contrast with common sense. All science is replete with paradoxes. Economics is not an exception. This paper is focused on two widely discussed paradoxes: the Mandeville paradox (and the associated idea of an ‘invisible hand’) and the Prisoners' Dilemma (with the allied literature on market failures). The main tenet of this paper is that they cannot be simultaneously paradoxical, because they state one the opposite of the other. If common sense contrasts with Mandeville, then it must agree with the Prisoners' Dilemma and vice versa. This is what I term the ‘paradox of paradoxes’ in economics, which is a simple consequence of the rarely noticed principle that two opposing propositions cannot be paradoxical at the same time. A tentative way out from this impasse is presented. I claim that economists would gain a better understanding of their profession if they devoted more time to the study of the intuitive or folk economics.