bluuebunny/crossref_metadata_2025 huggingface dataset:
Overproduction of Penicillin-Binding Protein 2 and Its Inactive Variants Causes Morphological Changes and Lysis inEscherichia coli
Authors: Legaree Blaine A. , Adams Calvin B. , Clarke Anthony J.
Published: May 2007

Penicillin-binding protein 2 (PBP 2) has long been known to be essential for rod-shaped morphology in gram-negative bacteria, includingEscherichia coliandPseudomonas aeruginosa. In the course of earlier studies withP. aeruginosaPBP 2, we observed thatE. coliwas sensitive to the overexpression of its gene,pbpA. In this study, we examinedE. colioverproducing bothP. aeruginosaandE. coliPBP 2. Growth of cells entered a stationary phase soon after induction of gene expression, and cells began to lyse upon prolonged incubation. Concomitant with the growth retardation, cells were observed to have changed morphologically from typical rods into enlarged spheres. Inactive derivatives of the PBP 2s were engineered, involving site-specific replacement of their catalytic Ser residues with Ala in their transpeptidase module. Overproduction of these inactive PBPs resulted in identical effects. Likewise, overproduction of PBP 2 derivatives possessing only their N-terminal non-penicillin-binding module (i.e., lacking their C-terminal transpeptidase module) produced similar effects. However,E. colioverproducing engineered derivatives of PBP 2 lacking their noncleavable, N-terminal signal sequence and membrane anchor were found to grow and divide at the same rate as control cells. The morphological effects and lysis were also eliminated entirely when overproduction of PBP 2 and variants was conducted withE. coliMHD79, a strain lacking six lytic transglycosylases. A possible interaction between the N-terminal domain of PBP 2 and lytic transglycosylases in vivo through the formation of multienzyme complexes is discussed.
Two Genes Encoding Protein Kinases of the HstK Family Are Involved in Synthesis of the Minor Heterocyst-Specific Glycolipid in the Cyanobacterium
Anabaena
sp. Strain PCC 7120
Authors: Shi Lei , Li Jian-Hong , Cheng Yong , Wang Li , Chen Wen-Li , Zhang Cheng-Cai
Published: May 2007

The filamentous cyanobacterium
Anabaena
sp. strain PCC 7120 can fix N
2
under oxic conditions, and the activity of nitrogen fixation occurs exclusively in heterocysts, cells differentiated from vegetative cells in response to a limitation of a combined-nitrogen source in the growth medium. At the late stages of heterocyst differentiation, an envelope layer composed of two glycolipids is formed to limit the entry of oxygen so that the oxygen-sensitive nitrogenase can function. The genome of
Anabaena
sp. strain PCC 7120 possesses a family of 13 genes (the
hstK
family), all encoding proteins with a putative Ser/Thr kinase domain at their N termini and a His-kinase domain at their C termini. In this study, we showed that the double mutant D4.3 strain, in which two members of this gene family,
pkn44
(all1625) and
pkn30
(all3691), were both inactivated, failed to fix N
2
in the presence of oxygen (Fox
−
). In an environment without oxygen, a low level of nitrogenase activity was detectable (Fix
+
). Heterocyst development in the mutant D4.3 was delayed by 24 h and arrested at a relatively early stage without the formation of the glycolipid layer (Hgl
−
). Only the minor species of the two heterocyst-specific glycolipids (HGLs) was missing in the mutant. We propose that DevH, a putative transcription factor, coordinates the synthesis of both HGLs, while Pkn44/Pkn30 and the previously characterized PrpJ may represent two distinct regulatory pathways involved in the synthesis of the minor HGL and the major HGL, respectively.
Complex Interplay between Type 1 Fimbrial Expression and Flagellum-Mediated Motility of Uropathogenic
Escherichia coli
Authors: Lane M. Chelsea , Simms Amy N. , Mobley Harry L. T.
Published: May 2007

Type 1 fimbriae and flagella have been previously shown to contribute to the virulence of uropathogenic
Escherichia coli
(UPEC) within the urinary tract. In this study, the relationship between motility and type 1 fimbrial expression was tested for UPEC strain CFT073 by examining the phenotypic effect of fimbrial expression on motility and the effect that induction of motility has on type 1 fimbrial expression. While constitutive expression of type 1 fimbriae resulted in a significant decrease in motility and flagellin expression (
P
< 0.0001), a loss of type 1 fimbrial expression did not result in increased motility. Additionally, hypermotility and flagellar gene over- and underexpression were not observed to affect the expression of type 1 fimbriae. Hence, it appeared that the relationship between type 1 fimbrial expression and motility is unidirectional, where the overexpression of type 1 fimbriae dramatically affects motility and flagellum expression but not vice versa. Moreover, the constitutive expression of type 1 fimbriae in UPEC cystitis isolate F11 and the laboratory strain
E. coli
K-12 MG1655 also resulted in decreased motility, suggesting that this phenomenon is not specific to CFT073 or UPEC in general. Lastly, by analyzing the repression of motility caused by constitutive type 1 fimbrial expression, it was concluded that the synthesis and presence of type 1 fimbriae at the bacterial surface is only partially responsible for the repression of motility, as evidenced by the partial restoration of motility in the CFT073
fim
L-ON Δ
fimAICDFGH
mutant. Altogether, these data provide further insight into the complex interplay between type 1 fimbrial expression and flagellum-mediated motility.
Identification of a Novel Streptococcal Gene Cassette Mediating SOS Mutagenesis in
Streptococcus uberis
Authors: Varhimo Emilia , Savijoki Kirsi , Jalava Jari , Kuipers Oscar P. , Varmanen Pekka
Published: May 2007

Streptococci have been considered to lack the classical SOS response, defined by increased mutation after UV exposure and regulation by LexA. Here we report the identification of a potential self-regulated SOS mutagenesis gene cassette in the
Streptococcaceae
family. Exposure to UV light was found to increase mutations to antibiotic resistance in
Streptococcus uberis
cultures. The mutational spectra revealed mainly G:C→A:T transitions, and Northern analyses demonstrated increased expression of a Y-family DNA polymerase resembling UmuC under DNA-damaging conditions. In the absence of the Y-family polymerase,
S. uberis
cells were sensitive to UV light and to mitomycin C. Furthermore, the UV-induced mutagenesis was almost completely abolished in cells deficient in the Y-family polymerase. The gene encoding the Y-family polymerase was localized in a four-gene operon including two hypothetical genes and a gene encoding a HdiR homolog. Electrophoretic mobility shift assays demonstrated that
S. uberis
HdiR binds specifically to an inverted repeat sequence in the promoter region of the four-gene operon. Database searches revealed conservation of the gene cassette in several
Streptococcus
species, including at least one genome each of
Streptococcus pyogenes
,
Streptococcus agalactiae
,
Streptococcus mitis
,
Streptococcus sanguinis
, and
Streptococcus thermophilus
strains. In addition, the
umuC
operon was localized in several mobile DNA elements of
Streptococcus
and
Lactococcus
species. We conclude that the
hdiR-umuC
-ORF3-ORF4 operon represents a novel gene cassette capable of mediating SOS mutagenesis among members of the
Streptococcaceae
.
What Is the Benefit to
Escherichia coli
of Having Multiple Toxin-Antitoxin Systems in Its Genome?
Authors: Tsilibaris Virginie , Maenhaut-Michel Geneviève , Mine Natacha , Van Melderen Laurence
Published: May 2007

The
Escherichia coli
K-12 chromosome encodes at least five proteic toxin-antitoxin (TA) systems. The
mazEF
and
relBE
systems have been extensively characterized and were proposed to be general stress response modules. On one hand,
mazEF
was proposed to act as a programmed cell death system that is triggered by a variety of stresses. On the other hand,
relBE
and
mazEF
were proposed to serve as growth modulators that induce a dormancy state during amino acid starvation. These conflicting hypotheses led us to test a possible synergetic effect of the five characterized
E. coli
TA systems on stress response. We compared the behavior of a wild-type strain and its derivative devoid of the five TA systems under various stress conditions. We were unable to detect TA-dependent programmed cell death under any of these conditions, even under conditions previously reported to induce it. Thus, our results rule out the programmed-cell-death hypothesis. Moreover, the presence of the five TA systems advantaged neither recovery from the different stresses nor cell growth under nutrient-limited conditions in competition experiments. This casts a doubt on whether TA systems significantly influence bacterial fitness and competitiveness during non-steady-state growth conditions.
Transcription Activation by the DNA-Binding Domain of the AraC Family Protein RhaS in the Absence of Its Effector-Binding Domain
Authors: Wickstrum Jason R. , Skredenske Jeff M. , Kolin Ana , Jin Ding J. , Fang Jianwen , Egan Susan M.
Published: May 2007

The
Escherichia coli
l
-rhamnose-responsive transcription activators RhaS and RhaR both consist of two domains, a C-terminal DNA-binding domain and an N-terminal dimerization domain. Both function as dimers and only activate transcription in the presence of
l
-rhamnose. Here, we examined the ability of the DNA-binding domains of RhaS (RhaS-CTD) and RhaR (RhaR-CTD) to bind to DNA and activate transcription. RhaS-CTD and RhaR-CTD were both shown by DNase I footprinting to be capable of binding specifically to the appropriate DNA sites. In vivo as well as in vitro transcription assays showed that RhaS-CTD could activate transcription to high levels, whereas RhaR-CTD was capable of only very low levels of transcription activation. As expected, RhaS-CTD did not require the presence of
l
-rhamnose to activate transcription. The upstream half-site at
rhaBAD
and the downstream half-site at
rhaT
were found to be the strongest of the known RhaS half-sites, and a new putative RhaS half-site with comparable strength to known sites was identified. Given that cyclic AMP receptor protein (CRP), the second activator required for full
rhaBAD
expression, cannot activate
rhaBAD
expression in a Δ
rhaS
strain, it was of interest to test whether CRP could activate transcription in combination with RhaS-CTD. We found that RhaS-CTD allowed significant activation by CRP, both in vivo and in vitro, although full-length RhaS allowed somewhat greater CRP activation. We conclude that RhaS-CTD contains all of the determinants necessary for transcription activation by RhaS.
Multicellular Development in
Myxococcus xanthus
Is Stimulated by Predator-Prey Interactions
Authors: Berleman James E. , Kirby John R.
Published: May 2007

Myxococcus xanthus
is a predatory bacterium that exhibits complex social behavior. The most pronounced behavior is the aggregation of cells into raised fruiting body structures in which cells differentiate into stress-resistant spores. In the laboratory, monocultures of
M. xanthus
at a very high density will reproducibly induce hundreds of randomly localized fruiting bodies when exposed to low nutrient availability and a solid surface. In this report, we analyze how
M. xanthus
fruiting body development proceeds in a coculture with suitable prey. Our analysis indicates that when prey bacteria are provided as a nutrient source, fruiting body aggregation is more organized, such that fruiting bodies form specifically after a step-down or loss of prey availability, whereas a step-up in prey availability inhibits fruiting body formation. This localization of aggregates occurs independently of the basal nutrient levels tested, indicating that starvation is not required for this process. Analysis of early developmental signaling
relA
and
asgD
mutants indicates that they are capable of forming fruiting body aggregates in the presence of prey, demonstrating that the stringent response and A-signal production are surprisingly not required for the initiation of fruiting behavior. However, these strains are still defective in differentiating to spores. We conclude that fruiting body formation does not occur exclusively in response to starvation and propose an alternative model in which multicellular development is driven by the interactions between
M. xanthus
cells and their cognate prey.
Dysembryoplastic neuroepithelial tumours: clinical, proliferative and apoptotic features
Authors: Duggal N , Taylor R , Zou G Y , Hammond R R
Published: May 2007

Aims:

Dysembryoplastic neuroepithelial tumours (DNTs) have been considered benign lesions characterised by a chronic, indolent clinical course. Previous studies have suggested that increased proliferation rates may be balanced by corresponding rates of apoptosis. The objective of this study was to determine whether a correlation exists between histological features and indices of proliferation/apoptosis.

Methods:

Fourteen consecutive surgical specimens meeting the histological criteria for DNT were retrospectively reviewed for evidence of aggressive histological features, including anaplasia, mitotic activity, and Ki67 labelling. Immunohistochemistry was performed semiquantitatively to evaluate and compare proliferation (Ki76) and apoptosis (TUNEL). The clinical course of the patients was also reviewed.

Results:

Atypical histological features were demonstrated in the glial component of select complex DNTs. TUNEL indices, however, had negligible correlation with proliferative indices. A balance between cell proliferation and apoptosis was not evident particularly in those cases displaying aggressive histological features.

Conclusions:

While there is no clearly defined clinical or pathological pattern to indicate aggressive growth of DNTs, elevated proliferative indices coupled with atypical histological features in complex DNTs should be taken into consideration in determining the aggressiveness of surgical extirpation and follow-up until experience with these uncommon tumours is greater.
Scots pine ectomycorrhizal fungal inoculum potential and dynamics in podzol-specific humus, eluvial and illuvial horizons one and four growth seasons after forest clear-cut logging
Authors: Heinonsalo Jussi , Sen Robin
Published: May 2007

The aims of this microcosm-based study were to characterize Scots pine ectomycorrhizal (EcM) inoculum potential in humus (O) and underlying eluvial (E) and illuvial (B) mineral podzol soil horizons and to compare the inoculum potential 1 and 4 years following clear-cut logging. The specific horizons were collected from a Scots pine control uncut stand, the adjacent interface zone (3–10 m from the forest edge), and the adjoining clear-cut area. The highest Simpson's reciprocal diversity indices (SRDI) of ectomycorrhizal morphotypes and polymerase chain reaction – internal transcribed spacer – restriction fragment length polymorphism (PCR-(ITS)-RFLP) taxa were detected in the humus and E horizon. The B horizon supported the lowest SRDI, but the community consisted of mycorrhizas representing active rhizomorph-forming species. Identified RFLP taxa, confirmed via ITS sequence analysis, highlighted horizon specificity for some genera and species. With respect to clear-cutting impacts, the most dominant ectomycorrhizal morphotypes detected and diversity indices were the same irrespective of the sampling time, which strongly indicates that inoculum potential is maintained up to four growth seasons after the clearcut. No forest treatment dependent differences in Scots pine seedling biomass were detected, but, compared with humus, significantly reduced biomass was recorded in deeper mineral soil horizons. The data are discussed in relation with recent vertical profile studies and forest silvicultural practices.
Pollination and seed production in western white pine
Authors: Owens John N. , Fernando Danilo D.
Published: May 2007

The reproductive biology of western white pine ( Pinus monticola Dougl. ex D. Don) at the Saanich seed orchard (SSO; a coastal seedling seed orchard) and the Kalamalka seed orchard (KSO; an interior clonal seed orchard) is described. Seed-cone development and morphology determine seed potential and affect filled seed production. Seed potential was high, commonly over 200 seeds per cone and filled seeds per cone averaged 50–60 at both orchards in 1999 from open pollinations combined with operational supplemental mass pollinations (OP-SMP). Filled seeds per cone at SSO in 2004 averaged 115 with open pollinations and OP-SMP. About 30% of ovules aborted before pollination. Another 25% aborted probably because of self-incompatibility at fertilization. Seed efficiency (SEF) was only 5% at KSO with open pollination but increased to 30% with OP-SMP. SEF was the same at SSO with or without OP-SMP. Reproductive success was very low at KSO without OP-SMP but increased to about 10%, similar to that of SSO, with OP-SMP. The optimal time for control pollinations was at cone stages 4 and 5 and optimal amount of pollen per pollination bag was 0.3–0.4 mL. Western white pine is a very good seed producer and can be easily managed in seed orchards to give very high seed production per cone and per tree.
Predominant paternal inheritance pattern of light-energy processing adaptive traits in red and black spruce hybrids
Authors: Major John E. , Barsi Debby C. , Mosseler Alex , Rajora Om P. , Campbell Moira
Published: May 2007

Ecophysiological traits related to light-energy processing and freezing tolerance are important adaptive traits in plants. Our goal was to investigate the pattern of inheritance of these traits in hybrids using controlled intra- and inter-specific crosses of red spruce ( Picea rubens Sarg.) (RS) and black spruce ( Picea mariana (Mill.) BSP) (BS). Our initial working hypothesis was that expected hybrid index categories could be a predictor of adaptive traits. Species results of dark-adapted photochemical efficiency (Fv/Fm) and light-adapted light-energy processing traits, quantum yield (YLD), thermal dissipation efficiency (qN), and chlorophyll fluorescence (Fpc), were consistent with previously published open-pollinated, species provenance results. Initially, YLD, qN, and Fpc, showed an additive inheritance pattern, evident by average hybrid index 50 having a mid-parent value. Because of various crosstypes of the hybrid families, parental analysis, testing male, female, and interaction effects, and having three categories (pure RS, pure BS, and hybrid spruce), revealed significant male and nonsignificant female and interactive effects. Underlying the averaged additive results was a significant species-specific paternal inheritance pattern. Crosses with BS males had 13.7% higher YLD (P = 0.001), 15.4% lower qN (P = 0.008), and 43.0% higher Fpc (P = 0.096) than crosses with either RS or hybrid males. Fv/Fm showed a nonadditive or parental species pattern. Parental analysis of Fv/Fm showed significant male, female, and male × female interaction effects, and further analysis supports a largely species-specific and paternally inherited trait. Freezing tolerance revealed a mixed model of inheritance dominated by species effects. Total dry mass was positively correlated with YLD, and negatively correlated with Fv/Fm and qN, suggesting a biological tradeoff. We know of no other studies in trees demonstrating paternal inheritance of ecophysiological processes that affect adaptation and fitness.
Comparison of thinning and prescribed fire restoration treatments to Sierran mixed-conifer historic conditions
Authors: North Malcolm , Innes Jim , Zald Harold
Published: May 2007

Thinning and prescribed fire are widely used to restore fire-suppressed forests, yet there are few studies of their effectiveness in Sierran mixed-conifer forest. We compared stand conditions in replicated plots before and after a combination of thinning and burning treatments against a reconstruction of the same forest in 1865. The historical forest had 67 stems/ha (trees ≥5 cm DBH), equal percentages of shade-tolerant and -intolerant tree species, stems randomly distributed at the stand scale, and a flat diameter distribution across size classes. The pretreatment forest averaged 469 stems/ha, which comprised 84% shade-tolerant and 14% shade-intolerant species, were highly clustered, and had a reverse-J-shaped diameter distribution. Thinning treatments failed to approximate historical composition, spatial pattern, or diameter distribution. Treatments left too many small trees, removed too many intermediate-sized trees (50–75 cm DBH), and retained a reverse-J-shaped diameter distribution. Current old growth comprises fewer large trees than historical conditions, suggesting that treatments should retain more intermediate-sized trees to provide for future large-tree recruitment. Understory thinning with prescribed fire significantly reduced stem density and produced a spatial pattern closest to historical conditions. Mixed-conifer restoration needs thinning prescriptions that vary by species and flexible rather than rigid upper diameter limits to retain some trees in all size classes.
Spring-flowering herbaceous plant species of the deciduous forests of eastern Canada and 20th century climate warming
Authors: Houle Gilles
Published: May 2007

Increases in the emission of greenhouse gases, particularly during the second half of the 20th century, have been associated with climate warming at the global scale. High latitude areas have been reported to be particularly sensitive to such changes, with significant impacts on plant phenology. The objectives of the present study were to (i) estimate changes in the flowering dates of 18 spring-flowering herbaceous plant species typical of the deciduous forests of eastern North America in three areas of eastern Canada (Gatineau–Ottawa, Montréal, and Québec) from 1900 to 2000 and (ii) associate these changes with those of annual and spring local temperatures. My results show a 2–6 days advance in flowering date over 100 years, depending on the region considered (corresponding to a ~2–3 days advance per 1 °C); these values are somewhat lower than those published in other studies, but still support the increasing body of literature on the effects of climate warming on plant phenology. Shifts in flowering phenology were particularly evident for Montréal, a large metropolitan region; this suggests that global climate warming, and its effects on plant phenology, may be exacerbated by local conditions, particularly those associated with large urban areas. Furthermore, species-specific responses to climate warming, as those presented here, might lead to significant changes in community composition and ecosystem functions.
ON THE ENERGY OF A BOSE–EINSTEIN CONDENSATE IN AN OPTICAL LATTICE
Authors: AFTALION AMANDINE
Published: May 2007

In this paper, we study the Gross–Pitaevskii energy of a Bose–Einstein condensate in the presence of an optical lattice, modeled by a periodic potential V(x3) in the third direction. We study a simple case where the wells of the potential V correspond to regions where V vanishes, and are separated by small intervals of size δ where V is large. According to the intensity of V, we determine the limiting energy as δ tends to 0. In the critical case, the periodic potential approaches a sum of delta functions and the limiting energy has a contribution due to the value of the wave function between the wells. The proof relies on Gamma convergence type techniques.
SECURITY OF "ASYMMETRICAL QUANTUM KEY DISTRIBUTION PROTOCOL"
Authors: LI CHUAN-MING , HWANG TZONELIH , LEE KUO-CHANG
Published: May 2007

In 2002, Li presented an asymmetrical quantum key distribution protocol which utilizes the correlations of Einstein-Podolsky-Rosen (EPR) pairs to establish a session key between two participants. Li claimed that an eavesdropper Eve cannot prevent his existence from being found by participants. However, this study shows that the session key can be obtained by Eve without being detected.
ON DIRECTLY SOLVING SCHRÖDINGER EQUATION FOR ${\rm H}^+_2$ ION BY GENETIC ALGORITHM
Authors: SAHA RAJENDRA , BHATTACHARYYA S. P.
Published: May 2007

Schrödinger equation (SE) is sought to be solved directly for the ground state of [Formula: see text] ion by invoking genetic algorithm (GA). In one approach the internuclear distance (R) is kept fixed, the corresponding electronic SE for [Formula: see text] is solved by GA at each R and the full potential energy curve (PEC) is constructed. The minimum of the PEC is then located giving Ve and Re. Alternatively, Ve and Re are located in a single run by allowing R to vary simultaneously while solving the electronic SE by genetic algorithm. The performance patterns of the two strategies are compared.
MODELLING COLLABORATION NETWORKS BASED ON NONLINEAR PREFERENTIAL ATTACHMENT
Authors: ZHOU TAO , WANG BING-HONG , JIN YING-DI , HE DA-REN , ZHANG PEI-PEI , HE YUE , SU BEI-BEI , CHEN KAN , ZHANG ZHONG-ZHI , LIU JIAN-GUO
Published: May 2007

In this paper, we propose an alternative model for collaboration networks based on nonlinear preferential attachment. Depending on a single free parameter "preferential exponent", this model interpolates between networks with a scale-free and an exponential degree distribution. The degree distribution in the present networks can be roughly classified into four patterns, all of which are observed in empirical data. And this model exhibits small-world effect, which means the corresponding networks are of very short average distance and highly large clustering coefficient. More interesting, we find a peak distribution of act-size from empirical data which has not been emphasized before. Our model can produce the peak act-size distribution naturally that agrees with the empirical data well.
ISOTROPIC NEGATIVELY-REFRACTING ATOMIC-VAPOR MEDIUM
Authors: SHEN JIAN QI
Published: May 2007

A new scenario to realize negative refraction with a photonic-resonant vapor material that can exhibit both electric and magnetic responses via multilevel quantum coherence is suggested. Compared with the previous method of artificial composite metamaterial, where the mechanism was considered by means of classical electromagnetic theory and the materials produced have anisotropic millimetre-scale composite structures, the present scheme suggested within the framework of quantum optics can be used to design and fabricate isotropic negatively-refracting materials with atomic-scale microscopic structure units. Such an advantage may lead to a potentially important application in the techniques of superlens and perfect imaging.
STUDIES OF THE LOCAL STRUCTURE AND THE g FACTORS FOR THE ORTHORHOMBICTi3+CENTER IN YAP
Authors: LIN JI-ZI , WU SHAO-YI , FU QIANG , ZHANG HUA-MING
Published: May 2007

The local structure and the g factors for the orthorhombic Ti3+center in YAP are theoretically studied from the perturbation formulas of the g factors gx, gyand gzfor a 3d1ion in orthorhombic symmetry based on the cluster approach. The observed large anisotropy of the g factors may be attributed to the significant low-symmetrical (tetragonal and orthorhombic) distortion near the Al3+site occupied by the impurity Ti3+. The calculated g factors in this work show reasonable agreement with the experimental data.
SCHEME FOR QUANTUM CLONING AND QUANTUM INFORMATION PROCESSING WITH TRAPPED IONS
Authors: ZHAN ZHI-MING
Published: May 2007

In this paper, a scheme is presented to implement the 1→2 universal quantum cloning machine (UQCM) with trapped ions. In this way, we also show that quantum information can be directly transferred from one ion to another. The distinct advantage of the scheme lies in the fact that it does not use the vibrational mode as the data bus. The vibrational mode is only virtually excited, which makes our scheme insensitive to heating, provided the system remains in the Lamb–Dicke regime.
QUANTUM ENTANGLEMENT OF COUPLED ANHARMONIC STRETCHES IN MOLECULES H2O AND SO2
Authors: HOU XI-WEN , CHEN JING-HUA , WAN MING-FANG , MA ZHONG-QI
Published: May 2007

Quantum entanglement of anharmonic stretches in molecules H 2 O and SO 2 is studied in terms of the reduced-density linear entropy with initial squeezed vacuum states and thermal states. It is shown that the entropy of both kinds of initial states with a small amplitude [Formula: see text] is quasi-periodic with the period of thermal states being larger than that of squeezed vacuum states for each molecule. The entropy evolution of both kinds of initial states with a larger amplitude [Formula: see text] is irregular. For each kind of initial state, the frequency of oscillation of the entropy for SO 2 is larger than that for H 2 O . That can be useful in quantum computing based on vibrational states in H 2 O and SO 2.
ON THE HADRONIC EQUATION OF STATE
Authors: HARTNACK C. , OESCHLER H. , AICHELIN JÖRG
Published: May 2007

The stiffness of the hadronic equation of state (EoS) has been extracted from the production rate of K+ mesons in heavy ion collisions around 1 A GeV incident energy. The data are best described with a compressibility coefficient κ around 200 MeV, a value which is usually called "soft". This is concluded from a detailed comparison of the results of transport theories with the experimental data.
FROM QED SPARKS TO QCD LIGHTNING: (OR HOW I SURVIVED W. GREINER'S 70TH BIRTHDAY PARTY)
Authors: GYULASSY MIKLOS
Published: May 2007

In celebration of Walter Greiner's 70th birthday and half century of physics, I discuss some of our collaborative work starting with nonlinear vacuum polarization in over-critical QED, early attempts to justify nuclear hydrodynamics via two-stream pionic instabilities, frustrations with the imperfect hadronic world, and recent works pondering the "perfect fluidity" of the sQGP discovered at RHIC.
SIGNATURES FOR BLACK HOLE PRODUCTION FROM HADRONIC OBSERVABLES AT THE LARGE HADRON COLLIDER
Authors: HUMANIC THOMAS J. , KOCH BENJAMIN , STÖCKER HORST
Published: May 2007

The concept of Large Extra Dimensions (LED) provides a way of solving the Hierarchy Problem which concerns the weakness of gravity compared with the strong and electro-weak forces. A consequence of LED is that miniature Black Holes (mini-BHs) may be produced at the Large Hadron Collider in p + p collisions. The present work uses the CHARYBDIS mini-BH generator code to simulate the hadronic signal which might be expected in a mid-rapidity particle tracking detector from the decay of these exotic objects if indeed they are produced. An estimate is also given for Pb + Pb collisions.
${\bar K}$-NUCLEAR DEEPLY BOUND STATES?
Authors: GAL AVRAHAM
Published: May 2007

Following the prediction by Akaishi and Yamazaki of relatively narrow [Formula: see text]-nuclear states, deeply bound by over 100 MeV where the main decay channel [Formula: see text] is closed, several experimental signals in stopped K- reactions on light nuclei have been interpreted recently as due to such states. In this talk I review (i) the evidence from K--atom data for a deep[Formula: see text]-nucleus potential, as attractive as [Formula: see text] at nuclear matter density, that could support such states; and (ii) the theoretical arguments for a shallow potential, [Formula: see text]. I then review a recent work by Mareš, Friedman and Gal in which [Formula: see text]-nuclear bound states are generated dynamically across the periodic table, using a RMF Lagrangian that couples the [Formula: see text] to the scalar and vector meson fields mediating the nuclear interactions. The reduced phase space available for [Formula: see text] absorption from these bound states is taken into account by adding a density- and energy-dependent imaginary term, underlying the corresponding [Formula: see text]-nuclear level widths, with a strength constrained by K--atom fits. Substantial polarization of the core nucleus is found for light nuclei, with central nuclear densities enhanced by almost a factor of two. The binding energies and widths calculated in this dynamical model differ appreciably from those calculated for a static nucleus. These calculations provide a lower limit of [Formula: see text] on the width of nuclear bound states for [Formula: see text] binding energy in the range [Formula: see text].
CALCULATION OF THE 3D INTERACTION GEOMETRY FOR TWO INTERLINKED χ(2) PROCESSES GENERATING ENTANGLED TRIPLETS
Authors: BONDANI MARIA , ALLEVI ALESSIA , ANDREONI ALESSANDRA
Published: May 2007

The geometrical conditions are analytically calculated in which two interlinked second-order nonlinear interactions generating entangled triplets are phase-matched in 3D. The interactions are the spontaneous parametric downconversion of an intense pump and the upconversion of a portion of the downconversion cones by a further pump. The calculation applies to type-I interactions occurring in uniaxial crystals and allows us to forecast positions and frequencies of the entangled triplets experimentally generated. The photon number statistics and the intensity correlations are also measured.
GHOST IMAGING WITH INTENSE CORRELATED LIGHT
Authors: DEGIOVANNI IVO PIETRO , CASTELLETTO STEFANIA , PUDDU EMILIANO , ANDREONI ALESSANDRA , BONDANI MARIA
Published: May 2007

We present a new ghost-imaging experiment that is realized by exploiting two intense correlated beams. The beams involved are signal and idler of a seeded parametric downconversion. The peculiarity of this scheme is that the seed field is an intense pseudo-thermal field generated by passing a laser beam through two rotating ground glass plates.
ENTROPY OPERATOR AND ASSOCIATED WIGNER FUNCTION
Authors: MOYA-CESSA HÉCTOR
Published: May 2007

We show how the entropy operators for two interacting systems may be calculated. In the case of the atom-field interaction, we obtain the associated Wigner function for the entropy operator for the quantized field.
NON-POSITIVE SEMIGROUP DYNAMICS IN CONTINUOUS VARIABLE MODELS
Authors: BENATTI F. , FLOREANINI R.
Published: May 2007

Non-positive, Markovian semigroups are sometimes used to describe the time evolution of subsystems immersed in an external environment. A widely adopted prescription to avoid the appearance of negative probabilities is to eliminate from the admissible initial conditions those density matrices that would not remain positive by the action of the semigroup dynamics. Using a continuous variable model, we show that this procedure leads to physical inconsistencies when two subsystems are considered and their initial state is entangled.
QUANTUM CONTROL THEORY FOR DECOHERENCE SUPPRESSION IN QUANTUM GATES
Authors: CALARCO T. , CIRONE M. A. , COZZINI M. , NEGRETTI A. , RECATI A. , CHARRON E.
Published: May 2007

We show how quantum optimal control theory can help achieve high-fidelity quantum gates in real experimental settings. We discuss several optimization methods (from iterative algorithms to optimization by interference and to impulsive control) and different physical scenarios (from optical lattices to atom chips and to Rydberg atoms).
EXPERIMENTAL ANALYSIS OF A SIMPLE LINEAR OPTICS PHASE GATE
Authors: SCHMID CH. , KIESEL N. , WEBER U. , URSIN R. , WEINFURTER H.
Published: May 2007

Linear optics two-qubit logic gates are essential tools in photonic quantum information. We describe a recently introduced simple conditional phase gate for photons, which relies on only one second order interference at a polarization dependent beam splitter, thereby making additional stability precautions dispensable. The improved quality of the gate is evaluated by performing full process tomography. The obtained process tomography data is fitted by a model based on experimental parameters of the setup which allows predictions on the performance of the gate in multi-photon experiments. .
GENERATION OF NARROW-BANDWIDTH SINGLE PHOTONS USING ELECTROMAGNETICALLY INDUCED TRANSPARENCY IN ATOMIC ENSEMBLES
Authors: WALTHER P. , EISAMAN M. D. , ANDRÉ A. , MASSOU F. , FLEISCHHAUER M. , ZIBROV A. S. , LUKIN M. D.
Published: May 2007

We review recent experiments [M. D. Eisaman et al., Nature438 (2005) 837] demonstrating the generation of narrow-bandwidth single photons using a room-temperature ensemble of 87 Rb atoms. Our method involves creation of an atomic coherence via Raman scattering and projective measurement, followed by the coherent transfer of this atomic coherence onto a single photon using electromagnetically induced transparency (EIT). The single photons generated using this method are shown to have many properties necessary for quantum information protocols, such as narrow bandwidths, directional emission, and controllable pulse shapes. The narrow bandwidths of these single photons (~MHz), resulting from their matching to the EIT resonance (~MHz), allow them to be stored in narrow-bandwidth quantum memories. We demonstrate this by using dynamic EIT to store and retrieve the single photons in a second ensemble for storage times up to a few microseconds. We also describe recent improvements to the single-photon fidelity compared to the work by M. D. Eisaman in Nature438 (2005) 837. These techniques may prove useful in quantum information applications such as quantum repeaters, linear-optics quantum computation, and daytime free-space quantum communication.
THE VIP (VIOLATION OF THE PAULI EXCLUSION PRINCIPLE) EXPERIMENT
Authors: BARTALUCCI S. , BERTOLUCCI S. , BRAGADIREANU M. , CARGNELLI M. , CATITTI M. , CURCEANU (PETRASCU) C. , DI MATTEO S. , EGGER J.-P. , GUARALDO C. , ILIESCU M. , ISHIWATARI T. , LAUBENSTEIN M. , MARTON J. , MILOTTI E. , PIETREANU D. , PONTA T. , SIRGHI D. L. , SIRGHI F. , SPERANDIO L. , WIDMANN E. , ZMESKAL J.
Published: May 2007

The Pauli Exclusion Principle (PEP) represents one of the fundamental principles of the modern physics and our comprehension of the surrounding matter is based on it. Even if today there are no compelling reasons to doubt its validity, it still spurs a lively debate on its limits, as testified by the abundant contributions found in the literature and in topical conferences. We present a method of searching for possible small violations of PEP for electrons, through the search for "anomalous" X-ray transitions in copper atoms, produced by "fresh" electrons which can decay in a Pauli-forbidden transition to the 1s level, already occupied by two electrons. The VIP Experiment has the scientific goal to improve by four orders of magnitude the present limit on the probability of PEP violation for electrons, bringing it into the 10-30–10-31 region. Preliminary results, together with future plans, are presented.
ENTANGLEMENT, LOCALITY, AND SEPARABILITY: A TREATISE ON DIFFERENT VIEWPOINTS
Authors: KESSEMEIER THOMAS , KRÜGER THOMAS
Published: May 2007

Within the framework of a statistical interpretation of quantum mechanics, entanglement (in a mathematical sense) manifests itself in the non-separability of the statistical operator ρ representing the ensemble in question. In experiments, on the other hand, entanglement can be detected, in the form of non-locality, by the violation of Bell's inequality Δ ≤ 2. How can these different viewpoints be reconciled? We first show that (non-)separability follows different laws to (non-)locality, and, moreover, it is much more difficult to characterize as long as the mostly employed operational rather than an ontic definition of separability is used. In consequence, (i) "entanglement" has two different meanings which may or may not be realized simultaneously on one and the same ensemble, and (ii) we have to disadvise the use of the common separability definition which is still employed by the majority of the physical community.
High oxygen tension constricts epineurial arterioles of the rat sciatic nerve via reactive oxygen species
Authors: Sakai Noriko , Mizuno Risuke , Ono Nobuyuki , Kato Hiroyuki , Ohhashi Toshio
Published: May 2007

Microcirculation of the sheath of the rat sciatic nerve fiber was investigated by using an intravital microscope, and changes in the diameter of the epineurial arterioles in response to highly oxygenated Krebs-bicarbonate solution were evaluated. Superfusion of low-oxygen (0%) Krebs-bicarbonate solution (LKS) onto rat sciatic nerves did not affect changes in the diameter of the arterioles. Nifedipine, a Ca2+-channel blocker, caused a dose-dependent dilation of the epineurial arterioles in LKS. In contrast, superfusion of high-oxygen (21%) Krebs-bicarbonate solution (HKS) onto rat sciatic nerves significantly constricted the epineurial arterioles in a time-dependent manner. The HKS-induced constriction of the epineurial arterioles was significantly reduced by treatment with 120 U/ml superoxide dismutase (SOD) alone or 5,000 U/ml catalase alone. In the presence of 120 U/ml SOD plus 5,000 U/ml catalase, 10−4 M tempol, 10−6 M diphenyleneiodium, 2 × 10−4 M apocynin, or 10−6 M allopurinol, the HKS-induced constriction of the epineurial arterioles completely disappeared. These results suggest that superfusion of highly oxygenated solution onto rat sciatic nerves constricts the epineurial arterioles through reactive oxygen species (ROS), including superoxide and hydrogen peroxide, and that production of superoxide involves a NADPH oxidase- or xanthine oxidase-dependent pathway. In conclusion, ROS play significant roles in the regulation of microcirculation of rat sciatic nerves in vivo.
Are voltage-dependent ion channels involved in the endothelial cell control of vasomotor tone?
Authors: Figueroa Xavier F. , Chen Chien-Chang , Campbell Kevin P. , Damon David N. , Day Kathleen H. , Ramos Susan , Duling Brian R.
Published: May 2007

In the microcirculation, longitudinal conduction of vasomotor responses provides an essential means of coordinating flow distribution among vessels in a complex network. Spread of current along the vessel axis can display a regenerative component, which leads to propagation of vasomotor signals over many millimeters; the ionic basis for the regenerative response is unknown. We examined the responses to 10 s of focal electrical stimulation (30 Hz, 2 ms, 30 V) of mouse cremaster arterioles to test the hypothesis that voltage-dependent Na+(Nav) and Ca2+channels might be activated in long-distance signaling in microvessels. Electrical stimulation evoked a vasoconstriction at the site of stimulation and a spreading, nondecremental conducted dilation. Endothelial damage (air bubble) blocked conduction of the vasodilation, indicating an involvement of the endothelium. The Navchannel blocker bupivacaine also blocked conduction, and TTX attenuated it. The Navchannel activator veratridine induced an endothelium-dependent dilation. The Navchannel isoforms Nav1.2, Nav1.6, and Nav1.9 were detected in the endothelial cells of cremaster arterioles by immunocytochemistry. These findings are consistent with the involvement of Navchannels in the conducted response. BAPTA buffering of endothelial cell Ca2+delayed and reduced the conducted dilation, which was almost eliminated by Ni2+, amiloride, or deletion of α1HT-type Ca2+(Cav3.2) channels. Blockade of endothelial nitric oxide synthase or Ca2+-activated K+channels also inhibited the conducted vasodilation. Our findings indicate that an electrically induced signal can propagate along the vessel axis via the endothelium and can induce sequential activation of Navand Cav3.2 channels. The resultant Ca2+influx activates endothelial nitric oxide synthase and Ca2+-activated K+channels, triggering vasodilation.
Expression of human glutathione S-transferase P1 mediates the chemosensitivity of osteosarcoma cells
Authors: Huang Gangxiong , Mills Lisa , Worth Laura L.
Published: May 2007

Chemoresistance is a major reason that patients with osteosarcoma fail to achieve a lasting chemotherapy response, and it contributes to disease relapse, progression, and death. Human glutathione S-transferase P1 (GSTP1), a phase II detoxification enzyme, contributes to chemoresistance in many cancers. However, the role of GSTP1 in osteosarcoma chemoresistance is ill defined. We hypothesized that GSTP1 has cytoprotective effects in human osteosarcoma. To assess this possibility, we used GSTP1 cDNA transfection or RNA interference to overexpress or suppress GSTP1 in osteosarcoma cells, and assessed the cytotoxic effect of chemotherapeutic agents on these cells. Our results showed that GSTP1 expression was up-regulated in osteosarcoma cells when they were treated with doxorubicin or cisplatin. GSTP1 overexpression in SAOS-2 osteosarcoma cells caused the cells to be more resistant to doxorubicin and cisplatin. In contrast, GSTP1 suppression in HOS cells caused more apoptosis and extensive DNA damage in response to doxorubicin and cisplatin. The cytotoxicity assay also showed that GSTP1 suppression caused a 2.5-fold increase in cell growth inhibition resulting from doxorubicin and cisplatin treatments [the IC50s are ∼0.16 μmol/L (doxorubicin) and 1.8 μmol/L (cisplatin) for parental HOS versus 0.06 μmol/L (doxorubicin) and 0.75 μmol/L (cisplatin) for GSTP1-silenced HOS]. Moreover, GSTP1 suppression decreased the activation of extracellular signal–regulated kinase 1/2, which is induced by cisplatin and doxorubicin. Taken together, these findings show that GSTP1 contributes to doxorubicin and cisplatin resistance in osteosarcoma, which may be mediated in part by the activation of extracellular signal–regulated kinase 1/2. Targeting of GSTP1 combined with chemotherapy may have synergistic therapeutic effects on osteosarcoma. [Mol Cancer Ther 2007;6(5):1610–9]
Cellular FLICE-inhibitory protein regulates chemotherapy-induced apoptosis in breast cancer cells
Authors: Rogers Katherine M.A. , Thomas Michelle , Galligan Leeona , Wilson Timothy R. , Allen Wendy L. , Sakai Hidekazu , Johnston Patrick G. , Longley Daniel B.
Published: May 2007

Combination treatment regimens that include topoisomerase-II–targeted drugs, such as doxorubicin, are widely used in the treatment of breast cancer. Previously, we showed that IFN-γ and doxorubicin cotreatment synergistically induced apoptosis in MDA435 breast cancer cells in a signal transducer and activator of transcription 1–dependent manner. In this study, we found that this synergy was caspase-8 dependent. In addition, we found that IFN-γ down-regulated the expression of the caspase-8 inhibitor cellular FLICE-inhibitory protein (c-FLIP). Furthermore, IFN-γ down-regulated c-FLIP in a manner that was dependent on the transcription factors signal transducer and activator of transcription 1 and IFN regulatory factor-1. However, IFN-γ had no effect on c-FLIP mRNA levels, indicating that c-FLIP was down-regulated at a posttranscriptional level following IFN-γ treatment. Characterization of the functional significance of c-FLIP modulation by small interfering RNA gene silencing and stable overexpression studies revealed it to be a key regulator of IFN-γ– and doxorubicin-induced apoptosis in MDA435 cells. Analysis of a panel of breast cancer cell lines indicated that c-FLIP was an important general determinant of doxorubicin- and IFN-γ–induced apoptosis in breast cancer cells. Furthermore, c-FLIP gene silencing sensitized MDA435 cells to other chemotherapies, including etoposide, mitoxantrone, and SN-38. These results suggest that c-FLIP plays a pivotal role in modulating drug-induced apoptosis in breast cancer cells. [Mol Cancer Ther 2007;6(5):1544–51]