Measurement of the CP asymmetry and branching fraction of B0-->rho0K0

We present a measurement of the branching fraction and time-dependent CP asymmetry of B(0)-->rho0K0. The results are obtained from a data sample of 227x10(6) Upsilon(4S)-->BB decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at Stanford Linear Accelerator Center. From a time-dependent maximum likelihood fit yielding 111+/-19 signal events, we find B(B(0)-->rho0K0)=(4.9+/-0.8+/-0.9)x10(-6), where the first error is statistical and the second systematic. We report the measurement of the CP parameters S(rho)(0)K(0)S=0.20+/-0.52+/-0.24 and C(rho)(0)K(0)S=0.64+/-0.41+/-0.20.

Observation of B-->eta'K* and evidence for B+-->eta'rho+

We present an observation of B-->eta'K*. The data sample corresponds to 232x10(6) BB[over ] pairs collected with the BABAR detector at the PEP-II asymmetric-energy B factory at the Stanford Linear Accelerator Center. We measure the branching fractions (in units of 10(-6)) B(B(0)-->eta'K*0)=3.8+/-1.1+/-0.5 and B(B+-->eta'K*+)=4.9(1.7)(+1.9)+/-0.8, where the first error is statistical and the second systematic. A simultaneous fit results in the observation of B-->eta'K* with B(B-->eta'K*)=4.1(-0.9)(+1.0)+/-0.5. We also search for B-->eta'rho and eta'f(0)(980)(f(0)-->pi+pi-) with results and 90% confidence level upper limits B(B+-->eta'rho+)=8.7(-2.8-1.3)(+3.1+2.3) (<14), B(B(0)-->eta'rho0)<3.7, and B(B(0)-->eta'f(0)(980)(f(0)-->pi+pi-))<1.5. Charge asymmetries in the channels with significant yields are consistent with zero.

Observation of CP violation in B --> eta'K0 decays

We present measurements of the time-dependent CP-violation parameters S and C in B(0) --> eta(')K(0) decays. The data sample corresponds to 384 x 10(6) BB pairs produced by e(+)e(-) annihilation at the Upsilon(4S). The results are S=0.58+/-0.10+/-0.03 and C=-0.16+/-0.07+/-0.03. We observe mixing-induced CP violation with a significance of 5.5 standard deviations in this b --> s penguin dominated mode.

Observation of a Charmed Baryon Decaying to D;{0}p at a Mass Near 2.94 GeV/c;{2}

A search for charmed baryons decaying to D(0)p reveals two states: the Lambdac(2880)+ baryon and a previously unobserved state at a mass of [2939.8+/-1.3(stat)+/-1.0(syst)] MeV/c2 and with an intrinsic width of [17.5+/-5.2(stat)+/-5.9(syst)] MeV. Consistent and significant signals are observed for the K(-)pi(+) and K(-)pi(+)pi(-)pi(+) decay modes of the D0 in 287 fb(-1) annihilation data recorded by the BABAR detector at a center-of-mass energy of 10.58 GeV. There is no evidence in the D+p spectrum of doubly charged partners. The mass and intrinsic width of the Lambdac(2880)+ baryon and relative yield of the two baryons are also measured.

Measurements of branching fraction, polarization, and charge asymmetry of B(+/-)-->rho(+/-)rho(0) and a search for B(+/-)-->rho(+/-)f(0)(980)

We measure the branching fraction (B), polarization (f(L)), and CP asymmetry (A(CP)) of B(+/-)-->rho(+/-)rho(0) decays and search for the decay B(+/-)-->rho(+/-)f(0)(980) based on a data sample of 231.8 x 10(6) Upsilon(4S)-->BB decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. In B(+/-)-->rho(+/-)rho(0) decays we measure B=(16.8+/-2.2+/-2.3) x 10(-), f(L)=0.905+/-0.042(-0.027)(+0.023), and A(CP)=-0.12+/-0.13+/-0.10, and find an upper limit on the branching fraction of B(+/-)-->rho(+/-)f(0)(980)(-->pi(+)pi(-)) decays of 1.9 x 10(-6) at 90% confidence level.

Observation of B(+)-->phiphiK(+) and evidence for B(0)-->phiphiK(0) below eta(c) threshold

We report measurements of the decays B(+)-->phiphiK(+) and B(0)-->phiphiK(0) using a sample of 231 x 10(6) BB pairs collected with the BABAR detector at the PEP-II asymmetric-energy B factory at the Stanford Linear Accelerator Center. The branching fractions are measured to be B(B(+)-->phiphiK(+))=(7.5+/-1.0(stat)+/-0.7(syst)) x 10(-6) and B(B(0)-->phiphiK(0))=(4.1(-1.4)(+1.7)(stat)+/-0.4(syst)) x 10(-6) for a phiphi invariant mass below 2.85 GeV/c(2).

Observation of an excited charm baryon Omega c* decaying to Omega c0gamma

We report the first observation of an excited singly charmed baryon Omega c* (css) in the radiative decay Omega c0gamma, where the Omega c0 baryon is reconstructed in the decays to the final states Omega(-)pi+, Omega(-)pi+pi0, Omega(-)pi+pi(-)pi+, and Xi(-)K(-)pi+pi+. This analysis is performed using a data set of 230.7 fb(-1) collected by the BABAR detector at the PEP-II asymmetric-energy B factory at the Stanford Linear Accelerator Center. The mass difference between the Omega c* and the Omega c0 baryons is measured to be 70.8+/-1.0(stat)+/-1.1(syst) MeV/c2. We also measure the ratio of inclusive production cross sections of Omega c* and Omega c0 in e+e(-) annihilation.

Search for D0-D0 mixing and branching-ratio measurement in the decay D0-->K+ pi- pi0

We analyze 230.4 fb;{-1} of data collected with the BABAR detector at the PEP-II e;{+}e;{-} collider at SLAC to search for evidence of D0-D[over ];{0} mixing using regions of phase space in the decay D;{0}-->K;{+}pi;{-}pi;{0}. We measure the time-integrated mixing rate R_{M}=(0.023_{-0.014};{+0.018}(stat.)+/-0.004(syst.))%, and R_{M}<0.054% at the 95% confidence level, assuming CP invariance. The data are consistent with no mixing at the 4.5% confidence level. We also measure the branching ratio for D;{0}-->K;{+}pi;{-}pi;{0} relative to D;{0}-->K;{-}pi;{+}pi;{0} to be (0.214+/-0.008(stat.)+/-0.008(syst.))%.

Observation of a new Ds meson decaying to DK at a mass of 2.86 GeV/c2

We observe a new D_{s} meson with mass (2856.6+/-1.5_{stat}+/-5.0_{syst}) MeV/c;{2} and width (48+/-7_{stat}+/-10_{syst}) MeV/c;{2} decaying into D0K+ and D;{+}K_{S};{0}. In the same mass distributions, we also observe a broad structure with mass (2688+/-4_{stat}+/-3_{syst}) MeV/c;{2} and width (112+/-7_{stat}+/-36_{syst}) MeV/c;{2}. To obtain this result, we use 240 fb;{-1} of data recorded by the BABAR detector at the PEP-II asymmetric-energy e;{+}e;{-} storage rings at the Stanford Linear Accelerator Center running at center-of-mass energies near 10.6 GeV.

Measurement of the B-->pi l nu branching fraction and determination of absolute value of V(ub) with tagged B mesons

We report a measurement of the B-->pi l nu branching fraction based on 211 fb(-1) of data collected with the BABAR detector. We use samples of B0 and B+ mesons tagged by a second B meson reconstructed in a semileptonic or hadronic decay and combine the results assuming isospin symmetry to obtain B(B(0)-->pi- l+ nu) = (1.33+/-0.17stat+/-0.11syst) x 10(-4). We determine the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element absolute value V(ub) by combining the partial branching fractions measured in ranges of the momentum transfer squared and theoretical calculations of the form factor. Using a recent lattice QCD calculation, we find absolute value V(ub) = (4.5+/-0.5stat+/-0.3syst(+0.7) -0.5FF x 10(-3), where the last error is due to the normalization of the form factor.

Measurements of branching fractions, polarizations, and direct CP-violation asymmetries in B-->rhoK* and B-->f0(980)K* decays

We report searches for B-meson decays to the charmless final states rhoK* and f0(980)K* with a sample of 232x10(6) BB pairs collected with the BABAR detector at the PEP-II e+e- collider. We measure in units of 10(-6) the following branching fractions, where the first error quoted is statistical and the second systematic, or upper limits are given at the 90% confidence level: B(B+-->rho0K*+)<6.1, B(B+-->rho+K*0)=9.6+/-1.7+/-1.5, B(B0-->rho-K*+)<12.0, B(B0-->rho0K*0)=5.6+/-0.9+/-1.3, B(B+-->f0(980)K*+)=5.2+/-1.2+/-0.5, and B(B0-->f0(980)K*0)<4.3. For the significant modes, we also measure the fraction of longitudinal polarization and the charge asymmetry: fL(B+-->rho+K*0)=0.52+/-0.10+/-0.04, fL(B0-->rho0K*0)=0.57+/-0.09+/-0.08, ACP(B+-->rho+K*0)=-0.01+/-0.16+/-0.02, ACP(B0-->rho0K*0)=0.09+/-0.19+/-0.02, and ACP(B+-->f0(980)K*+)=-0.34+/-0.21+/-0.03.

Measurement of branching fractions and charge asymmetries in B decays to an eta meson and a K* meson

We present measurements of branching fractions and charge asymmetries for the decays B-->etaK*, where K* indicates a spin 0, 1, or 2 Kpi system. The data sample corresponds to 344x10(6) BB pairs collected with the BABAR detector at the PEP-II asymmetric-energy e+ e- collider at SLAC. We measure the branching fractions (in units of 10(-6): B(B0-->etaK*0(892))=16.5+/-1.1+/-0.8, B(B+-->etaK*+(892))=18.9+/-1.8+/-1.3, B(B0-->eta(Kpi)0*0)=11.0+/-1.6+/-1.5, B(B+-->eta(Kpi)0*+)=18.2+/-2.6+/-2.6, B(B0-->etaK2*0(1430))=9.6+/-1.8+/-1.1, and B(B+-->etaK2*+(1430))=9.1+/-2.7+/-1.4. We also determine the charge asymmetries for all decay modes.

Observation of B+ --> K0K+ and B0 --> K0K0

We report observations of the b --> d penguin-dominated decays B+ --> K0K+ and B0 --> K0K0 in 316 fb(-1) of e+ e- collision data collected with the BABAR detector. We measure the branching fractions B(B+ --> K0K+) = (1.61+/-0.44+/-0.09) x 10(-6) and B(B0 --> K0K0 = (1.08+/-0.28+/-0.11) x 10(-6) and the CP-violating charge asymmetry A(CP)(K0K+) = 0.10+/-0.26+/-0.03. Using a vertexing technique previously employed in several analyses of all-neutral final states containing kaons, we report the first measurement of time-dependent CP-violating asymmetries in B0 --> K(S)0K(S)0, obtaining S = -1.28(-0.73-0.16)(+0.80+0.11) and C = -0.40+/-0.41+/-0.06. We also report improved measurements of the branching fraction B(B+ --> K0 pi+) = (23.9+/-1.1+/-1.0) x 10(-6) and CP-violating charge asymmetry A(CP)(K0 pi+) = -0.029+/-0.039+/-0.010.

Measurement of the branching fraction and photon energy moments of B-->Xs gamma and A(CP)(B --> X(s+d gamma))

The photon spectrum in B-->Xs gamma decay, where Xs is any strange hadronic state, is studied using a data sample of 88.5 x 10(6) e+ e- --> Upsilon(4S) --> BB decays collected by the BABAR experiment at the Stanford Linear Accelerator Center. The partial branching fraction, DeltaB(B --> Xs gamma) = (3.67+/-0.29(stat)+/-0.34(syst)+/-0.29(model)) x 10(-4), the first moment <E gamma> = 2.288+/-0.025+/-0.017+/-0.015 GeV, and the second moment E2(gamma) = 0.0328+/-0.0040+/-0.0023+/-0.0036 GeV2 are measured for the photon energy range 1.9 GeV < E gamma < 2.7 GeV. They are also measured for narrower E gamma ranges. The moments are then fit to recent theoretical calculations to extract the heavy quark expansion parameters m(b) and mu2(pi) and to extrapolate the partial branching fraction to E gamma > 1.6 GeV. In addition, the direct CP asymmetry A(CP)(B-->X(s+d gamma) is measured to be -0.110+/-0.115(stat)+/-0.017(syst).

Observation of e(+)e(-) annihilation into the C = +1 hadronic final states rho(0)rho(0) and phirho(0)

We report the first observation of e(+)e(-) annihilation into states of positive C parity, namely, rho(0)rho(0) and phirho(0). The two states are observed in the pi(+)pi(-)pi(+)pi(-) and K(+)K(-)pi(+)pi(-) final states, respectively, in a data sample of 225 fb(-1) collected by the BABAR experiment at the Positron-Electron Project II e(+)e(-) storage rings at energies near sqrt[s]=10.58 GeV. The distributions of costheta(*), where theta(*) is the center-of-mass polar angle of the phi meson or the forward rho(0) meson, suggest production by two-virtual-photon annihilation. We measure cross sections within the range |costheta(*)|<0.8 of sigma(e(+)e(-)-->rho(0)rho(0))=20.7+/-0.7(stat)+/-2.7(syst) fb and sigma(e(+)e(-)-->phirho(0))=5.7+/-0.5(stat)+/-0.8(syst) fb.

Measurement of the spin of the omega(-) hyperon

A measurement of the spin of the Omega(-) hyperon produced through the exclusive process Xi(c)(0)-->Omega(-)K(+) is presented using a total integrated luminosity of 116 fb(-1) recorded with the BABAR detector at the e(+)e(-) asymmetric-energy B factory at SLAC. Under the assumption that the Xi(c)(0) has spin 1/2, the angular distribution of the Lambda from Omega(-)-->LambdaK(-) decay is inconsistent with all half-integer Omega(-) spin values other than 3/2. Lower statistics data for the process Omega(c)(0)-->Omega(-)pi(+) from a 230 fb(-1) sample are also found to be consistent with Omega(-) spin 3/2. If the Xi(c)(0) spin were 3/2, an Omega(-) spin of 5/2 could not be excluded.

Distribution of sorbed phenanthrene and pyrene in different humic fractions of soils and importance of humin

Contributions of fulvic-humic acids (FA/HA) and humin (HM) to sorption of phenanthrene (PHE) and pyrene (PYR) in a soil were differentiated using a humic separation procedure after multi-concentration sorption experiments. It was found that the amount of solutes in FA/HA did not change significantly after 48 h, while that in HM increased continuously and slowly up to the end of the experimental period (720 h), indicating that HM was the main region for slow sorption. Based on the fitting results using Freundlich equation, it was found that nonlinearity of both solutes was greater in HM than in FA/HA, consistent with the sorption characteristics of individually extracted HA and HM in a separate experiment. The observed nonlinearity of the solute distribution was confirmed by using three other soil samples with organic carbon contents ranging from 0.7 to 7.9%. Distribution dynamics of PHE and PYR among various fractions were also discussed.

Observation of B0 meson decay to a 1 +/(1260)pi /+

We present a measurement of the branching fraction of the decay B(0)-->a1 (+/)(1260)pi(/+) with a1 (+/)(1260)-->pi(/+)pi(+/)pi(+/). The data sample corresponds to 218 x 10(6) BB[over ] pairs produced in e+e- annihilation through the Upsilon(4S) resonance. We measure the branching fraction Beta(B(0)-->a1(+/)(1260)pi(/+))Beta(a1(+/)(1260)-->pi(/+)pi(+/)pi(+/)) = (16.6+/1.9+/1.5) x 10(-6), where the first error quoted is statistical and the second is systematic.

Search for T, CP, and CPT violation in B0-B0 mixing with inclusive dilepton events

We report the results of a search for T, CP, CPT, and violation in B0-B0 mixing using an inclusive dilepton sample collected by the BABAR experiment at the PEP-II factory. Using a sample of 232 x 10(6) BB pairs, we measure the T and CP violation parameter |q/p| - 1 = (-0.8 +/- 2.7(stat) +/- 1.9(syst) x 10(-3), and the CPT and CP parameters Imz = (13.9 +/- 7.3(stat) +/- 3.2(syst)) x 10(-3) and Delta Gamma x Rez = (7.1 +/- 3.9(stat) +/- 2.0(stat)) x 10(-3) ps(-1). The statistical correlation between the measurements of Imz and Delta Gamma x Rez is 76%.

Observation of Upsilon(4S) decays to pi(+)pi(-)Upsilon(1S) and pi(+)pi(-)Upsilon(2S)

Observation of Upsilon(4S) decays to pi(+)pi(-)C and pi(+)pi(-)Upsilon(2S)We present the first measurement of Upsilon(4S) decays to pi(+)pi(-)Upsilon(1S) based on a sample of 230 x 106(4S) mesons collected with the BABAR detector. We measure the product branching fractions Beta(Upsilon(4S) --> pi(+)pi(-)Upsilon(1S)) x BetaUpsilon(1S) --> mu(+)mu(-) = (2.23 +/- 0.25(stat) +/- 0.27(syst))x 10(-6) and Beta(Upsilon(4S) --> pi(+)pi(-)Upsilon(2S) x Beta(Upsilon(2S) --> mu(+)mu(-))=(1.69 +/-0.26(stat) +/- 0.20(syst)) x 10(-)6, from which we derive the partial widths Gamma(Upsilon(4S) --> pi(+)pi(-)Upsilon(1S))=(1.8 +/-0.4) keV and Gamma(Upsilon(4S) --> pi(+)pi(-)Upsilon(2S))=(2.7 +/- 0.8) keV.

Determinations of from inclusive semileptonic decays with reduced model dependence

We report two novel determinations of /|Vub/ with reduced model dependence, based on measurements of the mass distribution of the hadronic system in semileptonic B decays. Events are selected by fully reconstructing the decay of one B meson and identifying a charged lepton from the decay of the other B meson from Upsilon(4S)-->BB events. In one approach, we combine the inclusive B-->Xulambdav rate, integrated up to a maximum hadronic mass mX<1.67 GeV/c2, with a measurement of the inclusive B-->Xsgamma photon energy spectrum. We obtain /Vub/=(4.43+/-0.38stat+/-0.25syst+/-0.29theo) x 10-3. In another approach we measure the total B-->Xulambdav rate over the full phase space and find /Vub/=(3.84+/-0.70stat+/-0.30syst+/-0.10theo) x 10-3.

Contamination of rivers in Tianjin, China by polycyclic aromatic hydrocarbons

Tianjin urban/industrial complex is highly polluted by some persistent organic pollutants. In this study, the levels of 16 priority polycyclic aromatic hydrocarbons (PAHs) were tested in sediment, water, and suspended particulate matter (SPM) samples in 10 rivers in Tianjin. The total concentration of 16 PAHs varied from 0.787 to 1943 microg/g dry weight in sediment, from 45.81 to 1272 ng/L in water, and from 0.938 to 64.2 microg/g dry weight in SPM. The levels of PAHs in these media are high in comparison with values reported from other river and marine systems. Variability of total concentrations of PAHs in sediment, water, and SPM from nine different rivers is consistent with each other. No obvious trends of total PAHs concentration variations were found between upstream and downstream sediment, water, and SPM samples for most rivers, which indicate local inputs and disturbances along these rivers. The spatial distributions of three-phase PAHs are very similar to each other, and they are also similar to those found in topsoil. However, their chemical profiles are significantly different from that of topsoil. The change of profiles is consistent with the different aqueous transport capability of 16 PAHs. Low molecular weight PAHs predomination suggests a relatively recent local source and coal combustion source of PAHs in the study area.

Structures and stability of medium silicon clusters. II. Ab initio molecular orbital calculations of Si12–Si20

Ab initio all-electron molecular-orbital calculations are carried out to study the structures and relative stability of low-energy silicon clusters (Si(n),n = 12-20). Selected geometric isomers include those predicted by Ho et al. [Nature (London) 392, 582 (1998)] based on an unbiased search with tight-binding/genetic algorithm, as well as those found by Rata et al. [Phys. Rev. Lett. 85, 546 (2000)] based on density-functional tight-binding/single-parent evolution algorithm. These geometric isomers are optimized at the Møller-Plesset (MP2) MP2/6-31G(d) level. The single-point energy at the coupled-cluster single and double substitutions (including triple excitations) [CCSD(T)] CCSD(T)/6-31G(d) level for several low-lying isomers are further computed. Harmonic vibrational frequency analysis at the MP2/6-31G(d) level of theory is also undertaken to assure that the optimized geometries are stable. For Si12-Si17 and Si19 the isomer with the lowest-energy at the CCSD(T)/6-31G(d) level is the same as that predicted by Ho et al., whereas for Si18 and Si20, the same as predicted by Rata et al. However, for Si14 and Si15, the vibrational frequency analysis indicates that the isomer with the lowest CCSD(T)/6-31G(d) single-point energy gives rise to imaginary frequencies. Small structural perturbation onto the Si14 and Si15 isomers can remove the imaginary frequencies and results in new isomers with slightly lower MP2/6-31G(d) energy; however the new isomers have a higher single-point energy at the CCSD(T)/6-31G(d) level. For most Si(n) (n = 12-18,20) the low-lying isomers are prolate in shape, whereas for Si19 a spherical-like isomer is slightly lower in energy at the CCSD(T)/6-31G(d) level than low-lying prolate isomers.

Sample purification for analysis of organochlorine pesticides in sediment and fish muscle

The methods of sample purification for determinations of organochlorine pesticides (OCPs) in sediment and fish muscle were investigated in this study. A two-step procedure with preliminary cleanup and florisil column fraction was adopted. The working conditions of florisil column were firstly optimized. As to preliminary cleanup, liquid-liquid extraction by mixture of dimethyl formamide (DMF) and hexane and sulphonation by concentrated sulfuric acid were applied respectively and compared for the studied samples. The results indicated that liquid-liquid distribution could effectively separate lipids from fish muscle extracts, while failed in elimination of chlorophyll extracted from the relicts of hydrophytes in the sediment sample. In view of the sample appearance and clarity of gas chromatogram, sulphonation was more suitable to purify the sediment sample, however, the recoveries of the spiked standards were poor. The use of eluting solvent with stronger polarity could improve the corresponding recoveries significantly. Due to complete loss of Dieldrin, Endrin, and Endrin aldehyde after sulphonation, this pretreatment was improper to the three components. Sulfur, as the particular disturbing element in sediment, could be removed sufficiently by addition of activated copper powder. The relevant detection limits of the selected methods for OCPs in the studied substrates were also provided.

[Investigation on genotype constitution of different Plasmodium vivax isolates and its geographical distribution in China]

OBJECTIVE

To investigate the population constitution and geographical distribution of Plasmodium vivax in China using molecular technique.

METHODS

Blood-spot filter paper samples with related epidemiological data were collected from vivax malaria patients living in malarious area of 10 provinces (autonomous region) in China. Semi-nested- or nested-allelic-specific PCR genotyping method was used to identify CSP genotypes, families and types of Plasmodium vivax of each isolate from these patients.

RESULTS

Of 384 field isolates of Plasmodium vivax, 258 temperate zone family strains were identified, including 14 allelic variant genotypes spreading among 10 sampling provinces; allelic variants sized less than 731 bp were only seen in 5 provinces in southern China; 79 tropical zone family strains including 5 genotypes were also distributed in 5 provinces of southern China south to 25 degrees N. lat; and 14 PV Type-2 strains including 2 genotypes were found in some areas of Hainan and Yunnan Provinces. In addition, 33 isolates from genotype-mixed infections were revealed.

CONCLUSION

At present, area north to 25 degrees N. lat. of the country is the sole area prevalent for Plasmodium vivax family strains of temperate zone; there is overlapping distribution of P. v. of temperate zone family and tropical zone family of this parasite in the southern China south to 25 degrees N. lat; where the most complex isolate constitution is in Yunnan and Hainan Provinces, and PV Type-2 strains have been found in some areas of the two provinces. Besides, there were 2 groups of genotype with distinct geographic distribution feature within the temperate zone family.

[Concomitant pulmonary nocardiosis and Hodgkin's disease: importance of long-term treatment]

A 32-year-old patient taking corticosteroid therapy for 10 months for autoimmune hemolytic anemia developed Hodgkin's disease and concomitant acute pulmonary nocardiosis. After treatment with imipenen and amikacin for 15 days, which was adapted to susceptibility tests, multiple-drug chemotherapy using the ABVD protocol (doxorubicin, bléomycin, vinblastine, dacarbazine) was given without recurrence of the pulmonary infection. Antibiotic prophylaxis using a minocycine-erythromycin combination was continued for 8 months. We discuss the importance of long-term treatment based on data in the literature.

Evidence for protection of nitrogenase from O(2) by colony structure in the aerobic diazotroph Gluconacetobacter diazotrophicus

Gluconacetobacter diazotrophicus is an endophytic diazotroph of sugarcane which exhibits nitrogenase activity when growing in colonies on solid media. Nitrogenase activity of G. diazotrophicus colonies can adapt to changes in atmospheric partial pressure of oxygen (pO(2)). This paper investigates whether colony structure and the position of G. diazotrophicus cells in the colonies are components of the bacterium's ability to maintain nitrogenase activity at a variety of atmospheric pO(2) values. Colonies of G. diazotrophicus were grown on solid medium at atmospheric pO(2) of 2 and 20 kPa. Imaging of live, intact colonies by confocal laser scanning microscopy and of fixed, sectioned colonies by light microscopy revealed that at 2 kPa O(2) the uppermost bacteria in the colony were very near the upper surface of the colony, while the uppermost bacteria of colonies cultured at 20 kPa O(2) were positioned deeper in the mucilaginous matrix of the colony. Disruption of colony structure by physical manipulation or due to 'slumping' associated with colony development resulted in significant declines in nitrogenase activity. These results support the hypothesis that G. diazotrophicus utilizes the path-length of colony mucilage between the atmosphere and the bacteria to achieve a flux of O(2) that maintains aerobic respiration while not inhibiting nitrogenase activity.

Solution structure of a viral DNA repair polymerase

DNA polymerase X (Pol X) from the African swine fever virus (ASFV) specifically binds intermediates in the single-nucleotide base-excision repair process, an activity indicative of repair function. In addition, Pol X catalyzes DNA polymerization with low nucleotide-insertion fidelity. The structural mechanisms by which DNA polymerases confer high or low fidelity in DNA polymerization remain to be elucidated. The three-dimensional structure of Pol X has been determined. Unlike other DNA polymerases, Pol X is formed from only a palm and a C-terminal subdomain. Pol X has a novel palm subdomain fold, containing a positively charged helix at the DNA binding surface. Purine deoxynucleoside triphosphate (dNTP) substrates bind between the palm and C-terminal subdomain, at a dNTP-binding helix, and induce a unique conformation in Pol X. The purine dNTP-bound conformation and high binding affinity for dGTP-Mg(2+) of Pol X may contribute to its low fidelity.

Response of the endophytic diazotroph Gluconacetobacter diazotrophicus on solid media to changes in atmospheric partial O(2) pressure

Gluconacetobacter diazotrophicus is an N(2)-fixing endophyte isolated from sugarcane. G. diazotrophicus was grown on solid medium at atmospheric partial O(2) pressures (pO(2)) of 10, 20, and 30 kPa for 5 to 6 days. Using a flowthrough gas exchange system, nitrogenase activity and respiration rate were then measured at a range of atmospheric pO(2) (5 to 60 kPa). Nitrogenase activity was measured by H(2) evolution in N(2)-O(2) and in Ar-O(2), and respiration rate was measured by CO(2) evolution in N(2)-O(2). To validate the use of H(2) production as an assay for nitrogenase activity, a non-N(2)-fixing (Nif(-)) mutant of G. diazotrophicus was tested and found to have a low rate of uptake hydrogenase (Hup(+)) activity (0.016 +/- 0.009 micromol of H(2) 10(10) cells(-1) h(-1)) when incubated in an atmosphere enriched in H(2). However, Hup(+) activity was not detectable under the normal assay conditions used in our experiments. G. diazotrophicus fixed nitrogen at all atmospheric pO(2) tested. However, when the assay atmospheric pO(2) was below the level at which the colonies had been grown, nitrogenase activity was decreased. Optimal atmospheric pO(2) for nitrogenase activity was 0 to 20 kPa above the pO(2) at which the bacteria had been grown. As atmospheric pO(2) was increased in 10-kPa steps to the highest levels (40 to 60 kPa), nitrogenase activity decreased in a stepwise manner. Despite the decrease in nitrogenase activity as atmospheric pO(2) was increased, respiration rate increased marginally. A large single-step increase in atmospheric pO(2) from 20 to 60 kPa caused a rapid 84% decrease in nitrogenase activity. However, upon returning to 20 kPa of O(2), 80% of nitrogenase activity was recovered within 10 min, indicating a "switch-off/switch-on" O(2) protection mechanism of nitrogenase activity. Our study demonstrates that colonies of G. diazotrophicus can fix N(2) at a wide range of atmospheric pO(2) and can adapt to maintain nitrogenase activity in response to both long-term and short-term changes in atmospheric pO(2).

Solution structure of the catalytic domain of gammadelta resolvase. Implications for the mechanism of catalysis

The site-specific DNA recombinase, gammadelta resolvase, from Escherichia coli catalyzes recombination of res site-containing plasmid DNA to two catenated circular DNA products. The catalytic domain (residues 1-105), lacking a C-terminal dimerization interface, has been constructed and the NMR solution structure of the monomer determined. The RMSD of the NMR conformers for residues 2-92 excluding residues 37-45 and 64-73 is 0.41 A for backbone atoms and 0.88 A for all heavy atoms. The NMR solution structure of the monomeric catalytic domain (residues 1-105) was found to be formed by a four-stranded parallel beta-sheet surrounded by three helices. The catalytic domain (residues 1-105), deficient in the C-terminal dimerization domain, was monomeric at high salt concentration, but displayed unexpected dimerization at lower ionic strength. The unique solution dimerization interface at low ionic strength was mapped by NMR. With respect to previous crystal structures of the dimeric catalytic domain (residues 1-140), differences in the average conformation of active-site residues were found at loop 1 containing the catalytic S10 nucleophile, the beta1 strand containing R8, and at loop 3 containing D67, R68 and R71, which are required for catalysis. The active-site loops display high-frequency and conformational backbone dynamics and are less well defined than the secondary structures. In the solution structure, the D67 side-chain is proximal to the S10 side-chain making the D67 carboxylate group a candidate for activation of S10 through general base catalysis. Four conserved Arg residues can function in the activation of the phosphodiester for nucleophilic attack by the S10 hydroxyl group. A mechanism for covalent catalysis by this class of recombinases is proposed that may be related to dimer interface dissociation.

[Comparison analysis between potential and actual pattern of artificial oases in arid region]

Based on theoretical analysis and demonstration research, the conception of potential pattern in the agriculture landscape of artificial oases in Xinjiang arid region and its analysis unit were discussed. The potential landscape pattern was defined as the one composed by spatial units with basic characteristics and properties which had no change or less change with the time. In agriculture landscape, soil was found to be a relatively stable element, and hence, different soil classification unit could be used to analyze the potential landscape pattern. A case study was carried out to analyze the potential and actual pattern of the artificial cases in Shihezi reclamation area by using the indexes of diversity, evenness, aggregation, mean patch elongation, patch shape fragmentation and mean patch fractal dimension. The result showed that the landscape pattern changed orderly from the potential to actual pattern, and the potential pattern could be used as the absolute criterion for researches on pattern changes in agriculture landscape.

Structural basis for the topological specificity function of MinE

Correct positioning of the division septum in Escherichia coli depends on the coordinated action of the MinC, MinD and MinE proteins. Topological specificity is conferred on the MinCD division inhibitor by MinE, which counters MinCD activity only in the vicinity of the preferred midcell division site. Here we report the structure of the homodimeric topological specificity domain of Escherichia coli MinE and show that it forms a novel alphabeta sandwich. Structure-directed mutagenesis of conserved surface residues has enabled us to identify a spatially restricted site on the surface of the protein that is critical for the topological specificity function of MinE.

Central afferent pathways conveying nociceptive input to the hypothalamic paraventricular nucleus as revealed by a combination of retrograde labeling and c-fos activation

Previous data have shown that noxious thermal stimulation of the hind leg in the anesthetized rat causes c-fos activation in the paraventricular nucleus of the hypothalamus (PVN); in other brain nuclei, including the cathecholaminergic cell groups of the caudal medulla; and in the adenohypophysis. Stimulation was followed by adrenocorticotropic hormone plasma release but did not provoke cardiovascular changes. In the current study, the afferent central pathways conveying the nociceptive input to the PVN were studied throughout the brain by using double labeling for the Fos-protein and the retrograde tracer cholera toxin subunit B (CTb) injected into the PVN. Although double labeling occurred in several hypothalamic nuclei, the periaqueductal gray, the lateral parabrachial area, and the catecholaminergic medullary groups, high rates of double labeling occurred only in the cells of the A1 region of the ventrolateral medulla ( approximately 83% of CTb-labeled cells expressing c-fos). Further triple labeling with tyrosine hydroxylase (TH) revealed that > 80% of the double-labeled cells were TH-immunoreactive. The spinal cord had the usual strong c-fos expression but showed no retrograde labeling from the PVN. Noxious stimulation caused corticosterone plasma release. To ascertain a possible link of spinofugal neurons with the A1 cells, biotinylated dextran amine was injected into the spinal dorsal horn. Numerous anterogradely labeled fibers with bouton-like structures were observed, with the latter apposed to double- and triple-labeled cells in the A1 region. It is suggested that a dysynaptic route relayed in the A1 region conveys the nociceptive somatic input from the spinal cord to the PVN. Noxious stimulation may act as a systemic stressor, activating the hypothalamic-pituitary-adrenal axis.

Solution structure of the single-strand break repair protein XRCC1 N-terminal domain

XRCC1 functions in the repair of single-strand DNA breaks in mammalian cells and forms a repair complex with beta-Pol, ligase III and PARP. Here we describe the NMR solution structure of the XRCC1 N-terminal domain (XRCC1 NTD). The structural core is a beta-sandwich with beta-strands connected by loops, three helices and two short two-stranded beta-sheets at each connection side. We show, for the first time, that the XRCC1 NTD specifically binds single-strand break DNA (gapped and nicked). We also show that the XRCC1 NTD binds a gapped DNA-beta-Pol complex. The DNA binding and beta-Pol binding surfaces were mapped by NMR and found to be well suited for interaction with single-strand gap DNA containing a 90 degrees bend, and for simultaneously making contacts with the palm-thumb of beta-Pol in a ternary complex. The findings suggest a mechanism for preferential binding of the XRCC1 NTD to flexible single-strand break DNA.

[The isolation of microbe producing biosurfactants]

Microorganisms capable of producing biosurfactants can be isolated by a series of steps including hydrocarbon enrichment culture, hemolytic activity assay on blood agar plates and oil displacement activity assay etc. Ten strains(including bacteria, yeasts and fungi) were isolated with higher surface activity from 1000 samples from soil, sludge, waste water etc. Two strains of bacteria produced rhamnolipids and trehaloselipids respectively. One strain of bacterium produced long chain unsaturated carboxylic acid and another produced azelaic acid. Two strains of yeasts produced lipopolysaccharides with excellent emulsification property.

[Clinical application of 96 hours' rapid skin tissue expanding technique]

OBJECTIVE

To reduce expansion course, diminish complications and improve expanding effect in skin tissue expander treatment.

METHODS

We have chosen 38 cases of skin tissue defects of small and moderate areas, on which we have carried out 96 hours' rapid skin tissue expanding technique by altering the time and the amount of saline injected.

RESULTS

All skin tissue defects have been successfully repaired. Half a year later, the incisions were inconspicuous.

CONCLUSION

96 hours' rapid skin tissue expanding technique has the following advantages, it is simple and safe, economic and convenient, rapid and reliable. This technique tends to be mature. What is more, it is easy to be popularized. We regard it as an ideal rapid expansion technique.

[The effect of combined endocrine therapy on prostate and testis]

OBJECTIVE

To study the pathological changes of the effect of combined endocrine therapy on normal prostate, benign prostatic hyperplasia, prostatic adenocarcinoma and testis.

METHODS

11 radical prostatectomy specimens, 3 core-needle biopsies of prostate and 3 testes obtained after at least 3 months of enatone-flutamide inhibition therapy were studied. Step-section was performed on radical specimens and average 16 sections per case were reviewed. PSA, PSAP and AE1/AE3 were immunostained on 14 cases of prostate cancer and a comparative study pre- and post-treatment was made.

RESULTS

No residual tumor was recognized in 2 cases. Such characteristic changes were found in 9 cases as prominent acinar atrophy, decreased ratio of acini to stroma, stromal fibrosis, squamous metaplasia of carcinoma, cytoplasmic vaculation, nuclear shrinkage, and nucleolar shrinkage. No apparent change was discovered in 3 cases. Secretory epithelial atrophy and basal cell hyperplasia were the popular change in BPH and normal prostate. The expressions of both PSA and PSAP were markedly reduced in prostate carcinoma and nonneoplastic glands. Pathological downstaging of the tumor was not found statistically. Epithelial atrophy also existed in seminal vesicles and Leydig cells of the testes after hormone therapy.

CONCLUSIONS

Combined endocrine therapy results in histologically distinctive changes that can be found in both nonneoplastic and neoplastic prostate tissue. However, the drugs can not eradicate prostate cancer completely. Testis atrophy is the direct action of the therapy.

Crystal structure of an RNA 16-mer duplex R(GCAGAGUUAAAUCUGC)2 with nonadjacent G(syn).A+(anti) mispairs

G.A mispairs are one of the most common noncanonical structural motifs of RNA. The 1.9 A resolution crystal structure of the RNA 16-mer r(GCAGAGUUAAAUCUGC)2 has been determined with two isolated or nonadjacent G.A mispairs. The molecule crystallizes with one duplex in the asymmetric unit in space group R3 and unit cell dimensions a = b = c = 49.24 A and alpha = beta = gamma = 51.2 degrees. It is the longest known oligonucleotide duplex at this resolution and isomorphous to the 16-mer duplex with the C.A+ mispairs [Pan, et al., (1998) J. Mol. Biol. 283, 977-984]. The C.A+ mispair behaves like a wobble pair while the G.A+ does not. The G.A mispairs are protonated at N1 of the adenines as in the C.A+ mispairs, and two hydrogen bonds in the G(syn).A+(anti) conformation are formed. The syn guanine is stabilized by an intranucleotide hydrogen bond between the 2-amino and the 5'-phosphate groups. The G(syn).A+(anti) conformation can provide a different surface for recognition in the grooves compared to other G.A hydrogen bonding schemes. The major groove is widened between the two mispairs allowing access to ligands. One of the 3-fold axes is occupied by a sodium ion and a water molecule, while a second is occupied by another water molecule.

The dimerization and topological specificity functions of MinE reside in a structurally autonomous C-terminal domain

Correct placement of the division septum in Escherichia coli requires the co-ordinated action of three proteins, MinC, MinD and MinE. MinC and MinD interact to form a non-specific division inhibitor that blocks septation at all potential division sites. MinE is able to antagonize MinCD in a topologically sensitive manner, as it restricts MinCD activity to the unwanted division sites at the cell poles. Here, we show that the topological specificity function of MinE residues in a structurally autonomous, trypsin-resistant domain comprising residues 31-88. Nuclear magnetic resonance (NMR) and circular dichroic spectroscopy indicate that this domain includes both alpha and beta secondary structure, while analytical ultracentrifugation reveals that it also contains a region responsible for MinE homodimerization. While trypsin digestion indicates that the anti-MinCD domain of MinE (residues 1-22) does not form a tightly folded structural domain, NMR analysis of a peptide corresponding to MinE1-22 indicates that this region forms a nascent helix in which the peptide rapidly interconverts between disordered (random coil) and alpha-helical conformations. This suggests that the N-terminal region of MinE may be poised to adopt an alpha-helical conformation when it interacts with the target of its anti-MinCD activity, presumably MinD.

Crystal structure of an RNA octamer duplex r(CCCIUGGG)2 incorporating tandem I.U wobbles

The crystal structure of the RNA octamer duplex r(CCCIUGGG)2has been elucidated at 2.5 A resolution. The crystals belong to the space group P21and have unit cell constants a = 33.44 A, b = 43.41 A, c = 49.39 A and beta = 104.7 degrees with three independent duplexes (duplexes 1-3) in the asymmetric unit. The structure was solved by the molecular replacement method and refined to an Rwork/Rfree of 0.185/0.243 using 3765 reflections between 8.0 and 2.5 A. This is the first report of an RNA crystal structure incorporating I.U wobbles and three molecules in the asymmetric unit. Duplex 1 displays a kink of 24 degrees between the mismatch sites, while duplexes 2 and 3 have two kinks each of 19 degrees and 27 degrees, and 24 degrees and 29 degrees, respectively, on either side of the tandem mismatches. At the I.U/U.I mismatch steps, duplex 1 has a twist angle of 33.9 degrees, close to the average for all base pair steps, but duplexes 2 and 3 are underwound, with twist angles of 24.4 degrees and 26.5 degrees, respectively. The tandem I.U wobbles show intrastrand purine-pyrimidine stacking but exhibit interstrand purine-purine stacking with the flanking C.G pairs. The three independent duplexes are stacked non-coaxially in a head-to-tail fashion to form infinite pseudo-continuous helical columns which form intercolumn hydrogen bonding interactions through the 2'-hydroxyl groups where the minor grooves come together.

Structure of a 16-mer RNA duplex r(GCAGACUUAAAUCUGC)2 with wobble C.A+ mismatches

The crystal structure of a 16-mer, the longest known RNA duplex, has been determined at 2.5 A resolution. The hexadecamer r(GCAGACUUAAAUCUGC) contains isolated C.A/A.C mismatches with two hydrogen bonds. The two hydrogen bonds in the mismatches suggests that N1 of A is protonated even though the crystallization was done at neutral pH. Therefore, the C.A mismatch is a C.A+ wobble similar to the G.U wobble. The two C.A+ pairs are isolated by four Watson-Crick pairs and flanked by five Watson-Crick base-pairs on either sides. Kinks/bends of 20 degrees are observed at the wobble sites. The Watson-Crick base-pair A5.U26 on the 5'-side of the first C6.A27(+) wobble has a twist angle of 27 degrees compared to the 3'-side U7.A28 pair of 36 degrees. The twist angles are reversed (37 degrees and 26 degrees) in the second A11(+).C22 wobble because of the approximate dyad in the molecule, the flanking base-pair sequences are A.U pairs. The wobbles expand the major groove to 7.1 A/7.3 A. The duplexes form helical columns and are tightly packed around the 31-screw axis. The minor grooves of adjacent columns in juxtaposition interact through the O2' atoms and the anionic phosphate oxygen atoms.

[Primary epididymal tumors]

OBJECTIVE

To improve the diagnosis of primary epididymal tumors.

METHOD

In 23 primary epididymal tumors (22 benign and 1 malignant), 14 were adenomatoid tumors, 6 were leiomyomas, 1 was multiple fibrous pseudomonas and 1 was sclerosing hemangioma. Epididymal adenocarcinoma was seen in a 57-year-old man.

RESULT

Epididymal tumors might be easily misdiagnosed as epididymal tuberculosis, chronic epididymis and spermatocele. Apart from certain benign clinical characteristics, benign epididymal tumors could be diagnosed by B-ultrasonography and aspiration biopsy. Most malignant tumors of epididymis presented as rapidly growing scrotal masses and cured by the removal of tumors or the whole epididymis of the same side. 19 of 22 cases were free from recurrence.

CONCLUSION

Malignant epididymal tumors should be treated as malignant tumors of testis and their prognosis is extremely poor.

Crystal structure of d(GCGCGCG) with 5'-overhang G residues

The crystal structure of the DNA heptamer d(GCGCGCG) has been solved at 1.65 A resolution by the molecular replacement method and refined to an R-value of 0.184 for 3598 reflections. The heptamer forms a Z-DNA d(CGCGCG)2 with 5'-overhang G residues instead of an A-DNA d(GCGCGC)2 with 3'-overhang G residues. The overhang G residues from parallel strands of two adjacent duplexes form a trans reverse Hoogsteen G x G basepair that stacks on the six Z-DNA basepairs to produce a pseudocontinuous helix. The reverse Hoogsteen G x G basepair is unusual in that the displacement of one G base relative to the other allows them to participate in a bifurcated (G1)N2 . . . N7(G8) and an enhanced (G8)C8-H . . . O6(G1) hydrogen bond, in addition to the two usual hydrogen bonds. The 5'-overhang G residues are anti and C2'-endo while the 3'-terminal G residues are syn and C2'-endo. The conformations of both G residues are different from the syn/C3'-endo for the guanosine in a standard Z-DNA. The two cobalt hexammine ions bind to the phosphate groups in both GpC and CpG steps in Z(I) and Z(II) conformations. The water structure motif is similar to the other Z-DNA structures.

[Severe vascular injuries following total hip replacement]

Severe vascular injury following total hip replacement (THR) is very rare. It has an a incidence of 0.25% and poses a serious threat to the involved limb and the patient's life. Vascular structures affected include the external iliac artery and vein, femoral artery and vein. In 721 cases of THR 3 had vascular injuries. The first case sustained the injury of the external iliac vessel which was cut by the sharp edge of bone cement while removing the displaced prosthesis. The second had laceration of the iliac vein while a pneumatic drill was used in the anterion superior acetabulum, and the third had the cut injury of the femoral artery during resection of the capsular scar tissue. The understanding of the mechanisms and location of vascular injury during THR will help surgeons in early diagnosis and treatment of the injury.

Chemical sensory deafferentation abolishes hypothalamic pituitary activation induced by noxious stimulation or electroacupuncture but only decreases that caused by immobilization stress. A c-fos study

We have shown in previous c-fos studies that noxious stimulation or electroacupuncture in deeply anaesthetized rats activate the hypothalamic pituitary corticotrope axis in a specific way. C-fos expression was more pronounced in the arcuate than the paraventricular hypothalamic nuclei, and none occurred in the pituitary intermediate lobe. The absence of the usual autonomic responses to psychological stress, such as tachycardia or blood pressure elevation, suggested a specific action of the somatosensory input on the hypothalamic pituitary axis. To prove this hypothesis, c-fos expression was examined in the paraventricular, arcuate and other hypothalamic nuclei, the pituitary gland, and the A1 and A2 medullary catecholaminergic cell groups of animals deprived of nociceptive primary afferent input by neonatal capsaicin. After noxious stimulation or electroacupuncture, no c-fos enhancement occurred in any of those sites in capsaicin-treated animals, and there was no increased plasma release of adrenocorticotropic hormone. In contrast, the hypothalamic pituitary c-fos activation provoked by immobilization stress though markedly decreased, was not abolished by capsaicin, whereas plasma release of adrenocorticotropic hormone remained undiminished. These findings suggest that noxious stimulation or electroacupuncture act on the hypothalamic pituitary corticotrope axis through an exclusively physical effect depending on the noxious signal elicited in the somatosensory pathway. They also demonstrate the occurrence of a minor somatosensory physical component after forced immobilization, acting on the hypothalamic pituitary axis probably together with the prevalent component of emotional arousal elicited by this form of stress.