bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth kinetics and thermal stability of a self-formed barrier layer at Cu-Mn∕SiO2 interface
Authors: Koike J. , Haneda M. , Iijima J. , Otsuka Y. , Sako H. , Neishi K.
Published: August 2007

A thin diffusion barrier was self-formed by annealing at an interface between a Cu-Mn alloy film and a SiO2 substrate. The growth of the barrier layer followed a logarithmic rate law, which represents field-enhanced growth mechanism in the early stage and self-limiting growth behavior in the late stage. The barrier layer was stable at 450 °C for 100 h and at 600 °C for 10 h. The interface diffusivity was estimated from the morphology change of the barrier layer at 600 °C and was found to be smaller than the grain-boundary diffusivity of bulk Cu.
Energy relaxation of InN thin films
Authors: Jang D.-J. , Lin G.-T. , Wu C.-L. , Hsiao C.-L. , Tu L. W. , Lee M.-E.
Published: August 2007

The energy relaxation of InN thin films has been studied by ultrafast time-resolved photoluminescence technique. The obtained carrier cooling curves can be explained by carriers releasing excessive energy through the carrier–LO-phonon interaction. The extracted effective phonon emission times decrease as the photoexcited carrier concentration reduces and come close to the theoretical prediction of 23fs at small carrier concentration. The reduction of energy loss rate at high photoexcited carrier density is attributed to the hot phonon effect.
Study of organic thin film transistor with polymethylmethacrylate as a dielectric layer
Authors: Huang Tsung-Syun , Su Yan-Kuin , Wang Po-Cheng
Published: August 2007

The properties of pentacene-based organic thin film transistors (OTFTs) with polymethylmetha-crylate (PMMA) as a dielectric layer have been investigated. The concentration of PMMA was about 8wt% with toluene as solvent. The pentacene film on PMMA dielectric layer displays high thin film quality according to results of x-ray diffraction scan and atomic force microscopy. The crystalline size was about 33.96nm and the grain size was about 1000–1500nm. The pentacene-based OTFTs with PMMA as a dielectric layer exhibited excellent electric characteristics, including a high mobility of 0.241cm2∕Vs or larger, an on/off current ratio of 104 or larger, and the threshold voltage of less than −6.3V.
Nonlinear nonresonant forces by radio-frequency waves in plasmas
Authors: Gao Zhe , Fisch Nathaniel J. , Qin Hong , Myra J. R.
Published: August 2007

Nonresonant forces by applied rf waves in plasmas are analyzed. Along the background dc magnetic field, the force arises from the gradient of the ponderomotive potential. Only when the dc magnetic field is straight, however, is this parallel force completely consistent with that from the single particle picture, where the ponderomotive force depends on the gradients of rf fields only. Across the dc magnetic field, besides the ponderomotive force from the particle picture, additional Reynolds stress and polarization stress contribute to the total force. For waves with frequency much lower than the cyclotron frequency, the perpendicular forces from the particle and fluid pictures can have opposite signs. In plasmas with a symmetry angle (e.g., toroidal systems), nonresonant forces cannot drive net flow or current in the flux surface, but the radial force may influence macroscopic behavior of plasma. Moreover, nonresonant forces may drive flow or current in linear plasmas or in a localized region of toroidal plasmas.
Single quantum dot spectroscopy using a fiber taper waveguide near-field optic
Authors: Srinivasan Kartik , Painter Oskar , Stintz Andreas , Krishna Sanjay
Published: August 2007

Photoluminescence spectroscopy of single InAs quantum dots at cryogenic temperatures (∼14K) is performed using a micron-scale optical fiber taper waveguide as a near-field optic. A lower bound on the measured collection efficiency of quantum dot spontaneous emission into the fundamental guided mode of the fiber taper is estimated at 0.1%, and spatially resolved measurements with ∼600nm resolution are obtained by varying the taper position with respect to the sample and using the fiber taper for both the pump and collection channels.
Investigation into the mechanical contact behavior of single asperities using static atomistic simulations
Authors: Jeng Yeau-Ren , Kao Wei-Cheng , Tsai Ping-Chi
Published: August 2007

This study employs an atomic-scale model to investigate mechanical contact behaviors of a single asperity, particularly those which take place beyond the elastic limit threshold. The results obtained from the current model are found to be in good agreement with the predictions yielded by continuum theory as the contact behavior of the asperity transits from fully elastic to elastoplastic contact interface. Furthermore, the result shows that adhesion within the single asperity has the negligible influence during the loading stage; however, the adhesion force leads to the sizable clusters of copper atoms on the rigid plate during the unloading stage.
Prediction of polar ordered oxynitride perovskites
Authors: Caracas Razvan , Cohen R. E.
Published: August 2007

Using a materials by design approach, the authors find a class of ordered oxynitride piezoelectrics with perovskite structure. They predict that ordered YSiO2N and YGeO2N are characterized by large nonlinear optic responses and by some of the largest polarizations known to date.
High-indium-content InGaAs metal-oxide-semiconductor capacitor with amorphous LaAlO3 gate dielectric
Authors: Goel N. , Majhi P. , Tsai W. , Warusawithana M. , Schlom D. G. , Santos M. B. , Harris J. S. , Nishi Y.
Published: August 2007

The structure and electrical properties of LaAlO3∕n-In0.53Ga0.47As metal-oxide-semiconductor capacitors deposited by molecular-beam epitaxy were investigated. Transmission electron microscopy revealed a sharp interface between the dielectric and InGaAs. Postdeposition annealing at 440–500°C significantly reduced the capacitive equivalent thickness and frequency dispersion. A hysteresis of 15mV–0.1V, a dielectric permittivity of 17±1, and a dielectric strength of ∼4.3MV∕cm were measured. Additionally, a high loss in the parallel conductance and gate-bias independence in the inversion region was observed, implying the fast generation rate of minority carriers in In0.53Ga0.47As.
Defects around self-organized InAs quantum dots measured by slow positron beam
Authors: Meng X. Q. , Chen Z. Q. , Jin P. , Wang Z. G. , Wei Long
Published: August 2007

Self-organized InAs quantum dots (QDs) have been fabricated by molecular beam epitaxy. The authors try to use a slow positron beam to detect defects in and around self-organized QDs, and point defects are observed in GaAs cap layer above QDs. For the self-organized InAs QDs without strain-reducing layer, it is free of defects. However, by introducing a strain-reducing layer, the density of point defects around larger sized InAs QDs increased. The above results suggest that low energy positron beam measurements may be a good approach to detect depth profiles of defects in QD materials.
Large polarization and enhanced magnetic properties in BiFeO3 ceramic prepared by high-pressure synthesis
Authors: Su W. N. , Wang D. H. , Cao Q. Q. , Han Z. D. , Yin J. , Zhang J. R. , Du Y. W.
Published: August 2007

The BiFeO3 ceramics were prepared by sol-gel method (BFO-1) and high-pressure synthesis (BFO-2). X-ray diffraction showed that these ceramics are almost of single phase. It is difficult to observe a ferroelectric loop of BFO-1 even at an electric field of 6kV∕cm. Compared to BFO-1, the high-pressure synthesized one has higher resistivity, higher density, and better crystallization. Under an applied electric field of 120kV∕cm, the values of remanent polarization and the coercive field are 46μC∕cm2 and 73kV∕cm, respectively. At room temperature, a magnetic hysteresis loop with enhanced magnetization can be observed in BFO-2.
Focal length modulation based on a metallic slit surrounded with grooves in curved depths
Authors: Shi Haofei , Du Chunlei , Luo Xiangang
Published: August 2007

According to the numerical calculation, the relative phase of emitting light scattered by surface plasmon in a single subwavelength metallic groove can be modulated by the groove depth. The focal length of the slit-groove-based focusing structures can be adjusted in certain value if the groove depths are arranged in traced profile. With the regulation of the groove depth profile, it is possible to modify the focus position in the precision of nanoscale without increasing the size of the nanodevice. The simulation results verify that the method is effective for the design of nano-optical devices such as optical microprobes.
Phase-matched second-harmonic generation in cross-linking polyurethane films by thermal-assisted optical poling
Authors: Si Jinhai , Hirao Kazuyuki
Published: August 2007

Phase-matched second-harmonic generation (SHG) in thermal-cross-linking polyurethane films was demonstrated using a thermal-assisted nonresonant optical poling technique. During the seeding process, samples heated in an oven were irradiated simultaneously by coherent superposition of the 1300nm fundamental and 650nm second-harmonic lights of a femtosecond laser. The photoinduced second-order optical nonlinearity of the polymer films seeded at elevated temperatures kept stable at room temperature. The measurements for the dependence of SHG on the film thickness showed that a χ(2) grating that satisfied the phase-matching condition for SHG was optically induced in the polymer films.
Nanomechanical displacement detection using fiber-optic interferometry
Authors: Azak N. O. , Shagam M. Y. , Karabacak D. M. , Ekinci K. L. , Kim D. H. , Jang D. Y.
Published: August 2007

We describe a fiber-optic interferometer to detect the motion of nanomechanical resonators. In this system, the primary technical challenge of aligning the fiber-optic probe to nanometer-scale resonators is overcome by simply monitoring the scattered light from the devices. The system includes no free-space optical components, and is thus simple, stable, and compact with an estimated displacement sensitivity of ∼0.3pm∕Hz at optical power levels of ∼0.75mW.
Nondestructive analysis of threading dislocations in GaN by electron channeling contrast imaging
Authors: Picard Y. N. , Caldwell J. D. , Twigg M. E. , Eddy C. R. , Mastro M. A. , Henry R. L. , Holm R. T. , Neudeck P. G. , Trunek A. J. , Powell J. A.
Published: August 2007

Threading dislocations in metal-organic chemical-vapor grown GaN films were imaged nondestructively by the electron channeling contrast imaging (ECCI) technique. Comparisons between ECCI and cross-sectional transmission electron microscopy indicated that pure edge dislocations can be imaged in GaN by ECCI. Total threading dislocation densities were measured by ECCI for various GaN films on engineered 4H-SiC surfaces and ranged from 107to109cm−2. A comparison between the ultraviolet electroluminescent output measured at 380nm and the total dislocation density as measured by ECCI revealed an inverse logarithmic dependence.
3
ω
method to measure thermal properties of electrically conducting small-volume liquid
Authors: Choi Sun Rock , Kim Joonwon , Kim Dongsik
Published: August 2007

This work presents a method to measure the thermal conductivity and heat capacity of electrically conducting small-volume liquid samples using the 3ω technique. A mathematical model of heat transfer is derived to determine the thermal properties from the 3ω signal considering the device geometry. In order to validate the model, an experimental apparatus has been designed and set up to measure the thermal properties (thermal conductivity and heat capacity) of seven different liquid samples. The results show good agreement with other literature values, demonstrating that the suggested method is effective for measuring the thermal properties of electrically conducting liquids. More importantly, the result with a sample volume of 1μl demonstrates the resolution of the thermal conductivity as precise as 0.01% which corresponds to a thermal-conductivity change of 10−4W∕mK in the case of water-based solutions.
Brillouin study of acoustic phonon confinement in GeO2 nanocubes
Authors: Li Y. , Lim H. S. , Ng S. C. , Kuok M. H. , Ge M. Y. , Jiang J. Z.
Published: August 2007

Brillouin light scattering from several aggregates of monodisperse GeO2 nanocubes has been measured. Six well-resolved spectral peaks are observed whose frequencies scale as 1∕L, where L is the cube edge length. A finite element analysis of the eigenvibrations of a free nanocube reveals that the peaks are due to acoustic phonon confinement. Simulations show that the lowest-energy mode has a predominantly torsionallike character. The elastic constants of the nanocubes are found to be much lower than those of bulk GeO2.
Nanomovement of azo polymers induced by metal tip enhanced near-field irradiation
Authors: Ishitobi Hidekazu , Tanabe Mamoru , Sekkat Zouheir , Kawata Satoshi
Published: August 2007

Nanomovement of azo polymers induced by metal tip enhanced near-field illumination was studied. A protrusion with 47nm full width at half maximum was induced with a resolution beyond the diffraction limit. At the top of the protrusion, an anisotropic movement occurs in a direction nearly parallel to the polarization of the incident light, and suggests the existence at the tip end of not only a longitudinal but also a lateral component of the electric field of light. The anisotropic photofluidity and the optical gradient force played important roles in the process of the light induced polymer movement.
Improving carrier transport and light emission in a silicon-nanocrystal based MOS light-emitting diode on silicon nanopillar array
Authors: Lin Gong-Ru , Lin Chun-Jung , Kuo Hao-Chung
Published: August 2007

A silicon-nanocrystal (nc-Si) based metal-oxide-semiconductor light-emitting diode (MOSLED) on Si nanopillar array with size, height, and density of 30nm, 350nm, and 2.8×1010cm−2, respectively, is characterized. The nanopillar roughened Si surface contributes to the improved turn-on characteristics by enhancing Fowler-Nordheim tunneling and reducing effective barrier height, providing the MOSLED a maximum optical power of 0.7μW obtained at biased current of 375μA. The optical intensity, turn-on current, and power-current slope of nc-Si MOSLED on high-aspect-ratio Si nanopillar array are 140μW∕cm2, 5μA, 2±0.8mW∕A, respectively. A maximum external quantum efficiency of 0.1% is reported.
Nonthermal plasma synthesis of size-controlled, monodisperse, freestanding germanium nanocrystals
Authors: Gresback Ryan , Holman Zachary , Kortshagen Uwe
Published: August 2007

Germanium nanocrystals may be of interest for a variety of electronic and optoelectronic applications including photovoltaics, primarily due to the tunability of their band gap from the infrared into the visible range of the spectrum. This letter discusses the synthesis of monodisperse germanium nanocrystals via a nonthermal plasma approach which allows for precise control of the nanocrystal size. Germanium crystals are synthesized from germanium tetrachloride and hydrogen entrained in an argon background gas. The crystal size can be varied between 4 and 50nm by changing the residence times of crystals in the plasma between ∼30 and 440ms. Adjusting the plasma power enables one to synthesize fully amorphous or fully crystalline particles with otherwise similar properties.
Copper-doped CdTe films with improved hole mobility
Authors: Ma Zhixun , Yu Kin Man , Liu Lei , Wang Lan , Perry Dale L. , Walukiewicz Wladek , Yu Peter , Mao Samuel S.
Published: August 2007

Copper-doped CdTe films have been grown by the laser epitaxy approach. X-ray diffraction, Rutherford backscattering, and photoreflectance spectroscopy were utilized to characterize the CdTe:Cu films. Structural analysis suggests that the growth of CdTe:Cu on GaAs(100) is initiated along the (100) orientation, which changes to the (111) direction after the film thickness exceeds 400nm. Hall effect measurements indicate that copper doping can achieve hole mobility over 150cm2∕Vs at room temperature.
Suppression of surface segregation and heavy arsenic doping into silicon during selective epitaxial chemical vapor deposition under atmospheric pressure
Authors: Ikuta Tetsuya , Fujita Shigeru , Iwamoto Hayato , Kadomura Shingo , Shimura Takayoshi , Watanabe Heiji , Yasutake Kiyoshi
Published: August 2007

The authors investigated the effects of the growth rate and temperature on the surface segregation during in situ As-doped selective epitaxial growth under atmospheric pressure. It was confirmed that high growth rate and high temperature suppress surface segregation. A film with a high As concentration (7.5×1019at.∕cm3) and a smooth surface was obtained by optimizing these conditions.
The lutein epoxide cycle in higher plants: its relationships to other xanthophyll cycles and possible functions
Authors: García-Plazaola Jose I. , Matsubara Shizue , Osmond C. Barry
Published: August 2007

Several xanthophyll cycles have been described in photosynthetic organisms. Among them, only two are present in higher plants: the ubiquitous violaxanthin (V) cycle, and the taxonomically restricted lutein epoxide (Lx) cycle, whereas four cycles seem to occur in algae. Although V is synthesised through the β-branch of the carotenoid biosynthetic pathway and Lx is the product of the α-branch; both are co-located in the same sites of the photosynthetic pigment-protein complexes isolated from thylakoids. Both xanthophylls are also de-epoxidised upon light exposure by the same enzyme, violaxanthin de-epoxidase (VDE) leading to the formation of zeaxanthin (Z) and lutein (L) at comparable rates. In contrast with VDE, the reverse reaction presumably catalysed by zeaxanthin epoxidase (ZE), is much slower (or even inactive) with L than with antheraxanthin (A) or Z. Consequently many species lack Lx altogether, and although the presence of Lx shows an irregular taxonomical distribution in unrelated taxa, it has a high fidelity at family level. In those plants which accumulate Lx, variations in ZE activity in vivo mean that a complete Lx-cycle occurs in some (with Lx pools being restored overnight), whereas in others a truncated cycle is observed in which VDE converts Lx into L, but regeneration of Lx by ZE is extremely slow. Accumulation of Lx to high concentrations is found most commonly in old leaves in deeply shaded canopies, and the Lx cycle in these leaves is usually truncated. This seemingly anomalous situation presumably arises because ZE has a low but finite affinity for L, and because deeply shaded leaves are not often exposed to light intensities strong enough to activate VDE. Notably, both in vitro and in vivo studies have recently shown that accumulation of Lx can increase the light harvesting efficiency in the antennae of PSII. We propose a model for the truncated Lx cycle in strong light in which VDE converts Lx to L which then occupies sites L2 and V1 in the light-harvesting antenna complex of PSII (Lhcb), displacing V and Z. There is correlative evidence that this photoconverted L facilitates energy dissipation via non-photochemical quenching and thereby converts a highly efficient light harvesting system to an energy dissipating system with improved capacity to engage photoprotection. Operation of the α- and β-xanthophyll cycles with different L and Z epoxidation kinetics thus allows a combination of rapidly and slowly reversible modulation of light harvesting and photoprotection, with each cycle having distinct effects. Based on the patchy taxonomical distribution of Lx, we propose that the presence of Lx (and the Lx cycle) could be the result of a recurrent mutation in the epoxidase gene that increases its affinity for L, which is conserved whenever it confers an evolutionary advantage.
Viewpoint: Avoiding common pitfalls of chlorophyll fluorescence analysis under field conditions
Authors: Logan Barry A. , Adams William W. , Demmig-Adams Barbara
Published: August 2007

The determination of chlorophyll fluorescence emission is a powerful tool for assessing the status of PSII and the allocation of absorbed light to photosynthesis v. photoprotective energy dissipation. The development of field-portable fluorometers has enabled growing numbers of scientists to measure fluorescence emission from plants in diverse field settings. However, the ease of operation of contemporary fluorometers masks the many challenges associated with collecting meaningful and interpretable fluorescence signals from leaves exposed to relevant environmental conditions. Here, we offer methodological advice aimed at, but not limited to, the non-specialist for the proper measurement of fluorescence parameters, with an emphasis on avoiding common errors in the use of fluorescence under field conditions. Chief among our suggestions is (1) to delay use of automatically calculated fluorescence parameters, presented by the instrument software, until raw data ‘traces’ have been carefully inspected to ensure the integrity of findings, and (2) to combine chlorophyll fluorescence analysis, as a rapid, preliminary method of assessing plant responses to stress, with additional methods of characterising the system of interest (e.g. gas exchange, foliar pigment composition, thylakoid protein composition).
β-Glucuronidase activity in seedlings of the parasitic angiosperm Cusctua pentagona: developmental impact of the β-glucuronidase inhibitor saccharic acid 1,4-lactone
Authors: Schoenbeck Mark A. , Swanson Gabriel A. , Brommer Sydney J.
Published: August 2007

Endogenous plant β-glucuronidase (β-GUS) activity was detected in germinating seeds, seedlings, stems, flowers and haustoria of the parasitic angiosperm Cuscuta pentagona Engelm. In vitro characterisation of this activity showed it to have an acidic pH optimum, similar to previously characterised plant activities, and a sensitivity to the β-GUS inhibitor saccharic acid 1,4-lactone (SAL). Application of SAL to seeds immediately after chemical scarification resulted in a significant developmental delay and, frequently, in the total arrest of seedling growth. In contrast, application of SAL subsequent to the emergence of the radicle did not produce a significant effect on the development of the seedling. Thus, the distribution of activity and the developmentally contingent potency of SAL in inhibiting growth suggest a role for β-GUS at an early stage of seed germination or seedling growth. Further, the inability of the inhibitor to prevent subsequent shoot elongation suggests that at least some plant growth processes do not require this activity, or that it is required only at minimal levels and is unaffected by the application of SAL.
Reproductive synchrony of three sympatric species of wobbegong shark (genus Orectolobus) in New South Wales, Australia: reproductive parameter estimates necessary for population modelling
Authors: Huveneers Charlie , Walker Terence I. , Otway Nicholas M. , Harcourt Robert G.
Published: August 2007

Reproductive parameters of three closely-related sympatric species of wobbegong (Orectolobus ornatus, O. maculatus and O. halei) off New South Wales (NSW) were investigated to contribute to a biological basis for the management of a commercial fishery targeting wobbegongs. Estimates of the onset of maturity based on ovary condition were 729 mm, 1117 mm, and 1591 mm total length (TL) for O. ornatus, O. maculatus and O. halei respectively. The length at which 50% of the male population is mature based on clasper calcification was 803 mm, 1282 mm and 1784 mm TL for O. ornatus, O. maculatus and O. halei, respectively, and was similar to female onset of maturity based on uterus condition and to TL-at-maternity. These species of wobbegong had synchronous, triennial reproductive cycles. Follicles took 2 years to enlarge before ovulation. During the first year, follicles remained small, and then grew rapidly during the second year before ovulation during November. Gestation lasted ~10–11 months and parturition occurred during September–October. Mean litter sizes were nine (s.e. 0.5) and 21 (s.e. 1.5) for O. ornatus and O. maculatus, respectively, and increased with female total length in O. ornatus. Pregnant O. ornatus and O. maculatus were frequently caught in northern NSW and no pregnant wobbegongs, or females with large, yolky follicles were captured south of Sydney. Differences in the reproductive conditions of wobbegongs caught in northern and central NSW suggested geographically dependent reproductive behaviour. Knowledge of the reproductive parameters provided in this paper is necessary for adequate fisheries management and species conservation assessments.
Does adding wood to agricultural streams enhance biodiversity? An experimental approach
Authors: Lester Rebecca E , Wright Wendy , Jones-Lennon Michelle
Published: August 2007

Riparian clearing and the removal of wood from channels have affected many streams in agricultural landscapes. As a result, these streams often have depauperate in-stream wood loads, and therefore decreased habitat complexity and lower levels of in-stream biodiversity. The introduction of wood was investigated as a possible rehabilitation technique for agricultural streams. Wood was re-introduced to eight streams in two separate high-rainfall, intensively grazed regions of Victoria, Australia and the effect on aquatic macroinvertebrate communities was measured. The addition of wood increased overall family richness and the richness of most functional feeding groups occupying edge and benthic habitats within the stream. Wood addition led to less overlap between benthic and edge macroinvertebrate communities, suggesting increased habitat heterogeneity within the stream ecosystem. Of all sampled habitats, wood supported the greatest density of families and was colonised by all functional feeding groups. Wood habitats also had the highest overall richness and supported the most taxa that were sensitive to disturbance. These findings suggest that re-introducing wood to agricultural streams is an appropriate rehabilitation technique where those streams are affected by reduced habitat complexity. Additional work is needed to confirm these findings over larger spatial and temporal scales.
Community-based sexual health care works: a review of the ACT outreach program
Authors: Sturrock Christine J. , Currie Marian J. , Vally Hassan , O'Keefe Elissa J. , Primrose Ruth , Habel Philip , Schamburg Kevin , Bowden Francis J.
Published: August 2007

Background: Men who have sex with men, sex workers, youth and university students are at increased risk for sexually transmissible infections (STI) and blood-borne viruses (BBV) and are therefore targets for sexual health services. In recognition of this, a collaborative project offering sexual health care in various outreach settings frequented by these groups was developed. Methods: Data collected by clinicians during consultations in five outreach venues (a sex-on-premises venue, a community AIDS organisation, a university campus, brothels and a youth centre) between 2002 and 2005 were analysed. Results: During 119 clinics (~547 clinician hours), 313 individuals (205 males and 108 females) received education and/or testing. Of those screened, 6.0% (15/249) were positive for chlamydia and 12.7% (9/71) tested positive for hepatitis C (HCV) antibodies. No new cases of hepatitis B (HBV) or HIV were identified and 37.2% (71/191) of patients reported never having been previously tested for HIV. Seroprevalence of hepatitis A and HBV antibodies were 53.8% (91/169) and 52.1% (135/259), respectively. More than half of all four groups reported inconsistent use of condoms and 8.6% reported intravenous drug use. Conclusions: Collaborations between agencies to provide outreach services facilitate community-based sexual health education and screening for groups at higher risk of STI and BBV. The database audit showed that through these outreach services cases of chlamydia and HCV that may have remained undetected were identified. The results also highlight the need for continuing hepatitis vaccination, testing, health promotion and education in these populations.
Prevalence of sexually transmissible infections (STI) among male patients with STI in Denpasar and Makassar, Indonesia: are symptoms of urethritis sufficient to guide syndromic treatment?
Authors: Davies Stephen C. , Madjid Baedah , Pardohudoyo Sutaryo , Wiraguna Anak Agung G. P. , Patten Jane H. , Upadisari Luh Putu
Published: August 2007

Background: There are few data on sexually transmissible infections in men in Indonesia. We conducted a prevalence study and compared symptoms alone with clinical signs to manage urethritis. Methods: We recruited symptomatic male patients at public clinics, and used standardised questionnaires, examinations and laboratory tests. Results: We recruited 273 men and the prevalences were Neisseria gonorrhoeae 18.2%, Chlamydia trachomatis 10.1%, and positive syphilis serology 5.2%. Four cases of HIV were detected. Urethral symptoms detected 91.7% of N. gonorrhoeae and/or C. trachomatis, and positive predictive value (PPV) was 41.8%, compared with clinical confirmation (sensitivity 86.1%, PPV 37.6%). Conclusions: Most cases of syphilis were asymptomatic, supporting routine screening for syphilis. Urethral symptoms predicted infection with N. gonorrhoeae/C. trachomatis better than clinical signs.
Knowledge and awareness of human papillomavirus (HPV): attitudes towards HPV vaccination among a representative sample of women in Victoria, Australia
Authors: Pitts Marian K. , Dyson Suzanne J. , Rosenthal Doreen A. , Garland Suzanne M.
Published: August 2007

Background: A vaccine program is underway to protect women against human papillomavirus (HPV) and thus cervical cancer. Previous studies have reported very low levels of HPV knowledge and there has been concern that preventative vaccines might not be readily accepted, given that HPV is transmitted sexually and the optimal time for vaccination is before sexual debut. Methods: A computer-assisted telephone survey was carried out with a representative sample of 1100 women aged 18 to 61 years, randomly selected from households in Victoria, Australia, to investigate knowledge and attitudes about HPV and attitudes towards HPV vaccination. Results: Half of the participants (51%) had heard of HPV; most reported learning about it from the media. Most women indicated they would trust their general practitioner (96.3%), a gynaecologist or specialist doctor (99.6%), or a women’s health service (97.0%) for information about HPV. Few women (11.9%) had ever sought information about HPV and only 14.8% of the total sample had ever discussed HPV with a friend. Strong support was found for vaccination in general and there was also significant support for a HPV vaccine. Conclusion: The present study documents ways in which women learn about HPV and indicates the potential for success of a vaccination program.
Modelling the population-level impact of vaccination on the transmission of human papillomavirus type 16 in Australia
Authors: Regan David G. , Philp David J. , Hocking Jane S. , Law Matthew G.
Published: August 2007

Background:
Vaccines are now available to prevent the development of cervical cancer from genital human papillomavirus (HPV) infection. The decision to vaccinate depends on a vaccine’s cost-effectiveness. A rigorous cost-effectiveness model for vaccinated individuals is presented in a companion paper; this paper investigates the additional benefits the community might receive from herd immunity.
Methods:
A mathematical model was developed to estimate the impact of a prophylactic vaccine on transmission of HPV type 16 in Australia. The model was used to estimate the expected reduction in HPV incidence and prevalence as a result of vaccination, the time required to achieve these reductions, and the coverage required for elimination. The modelled population was stratified according to age, gender, level of sexual activity and HPV infection status using a differential equation formulation. Clinical trials show that the vaccine is highly effective at preventing persistent infection and pre-cancerous lesions. These trials do not, however, provide conclusive evidence that infection is prevented altogether. The possible modes of vaccine action were investigated to see how vaccination might change the conclusions.
Results:
The model predicts that vaccination of 80% of 12-year-old girls will eventually reduce HPV 16 prevalence by 60–100% in vaccinated and 7–31% in unvaccinated females. If 80% of boys are also vaccinated, reductions will be 74–100% in vaccinated and 86–96% in unvaccinated females. A campaign covering only 12-year-old girls would require 5–7 years to achieve 50% of the eventual reduction. With a catch-up campaign covering 13–26-year-olds, this delay would be reduced to only 2 years. Unrealistically high coverage in both sexes would be required to eliminate HPV 16 from the population. Under pessimistic assumptions about the duration of vaccine-conferred immunity, HPV 16 incidence is predicted to rise in some older age groups.
Conclusions:
Mass vaccination with a highly effective vaccine against HPV 16 has the potential to substantially reduce the incidence and prevalence of infection. Catch-up vaccination offers the potential to substantially reduce the delay before the benefits of vaccination are observed. A booster vaccination might be required to prevent an increase in incidence of infection in women over 25 years of age.
Gamma oscillations dynamically couple hippocampal CA3 and CA1 regions during memory task performance
Authors: Montgomery Sean M. , Buzsáki György
Published: August 2007

The hippocampal formation is believed to be critical for the encoding, consolidation, and retrieval of episodic memories. Yet, how these processes are supported by the anatomically diverse hippocampal networks is still unknown. To examine this issue, we tested rats in a hippocampus-dependent delayed spatial alternation task on a modified T maze while simultaneously recording local field potentials from dendritic and somatic layers of the dentate gyrus, CA3, and CA1 regions by using high-density, 96-site silicon probes. Both the power and coherence of gamma oscillations exhibited layer-specific changes during task performance. Peak increases in the gamma power and coherence were found in the CA3–CA1 interface on the maze segment approaching the T junction, independent of motor aspects of task performance. These results show that hippocampal networks can be dynamically coupled by gamma oscillations according to specific behavioral demands. Based on these findings, we propose that gamma oscillations may serve as a physiological mechanism by which CA3 output can coordinate CA1 activity to support retrieval of hippocampus-dependent memories.
CD200 and its receptor, CD200R, modulate bone mass via the differentiation of osteoclasts
Authors: Cui Weiguo , Cuartas Esteban , Ke Juan , Zhang Qing , Einarsson Halldor B. , Sedgwick Jonathon D. , Li Jun , Vignery Agnès
Published: August 2007

Fusion of macrophages is an essential step in the differentiation of osteoclasts, which play a central role in the development and remodeling of bone. Osteoclasts are important mediators of bone loss, which leads, for example, to osteoporosis. Macrophage fusion receptor/signal regulatory protein α (MFR/SIRPα) and its ligand CD47, which are members of the Ig superfamily (IgSF), have been implicated in the fusion of macrophages. We show that CD200, which is not expressed in cells that belong to the myeloid lineage, is strongly expressed in macrophages at the onset of fusion. By contrast, the CD200 receptor (CD200R), which, like CD200, belongs to the IgSF, is expressed only in cells that belong to the myeloid lineage, including osteoclasts, and in CD4
+
T cells. Osteoclasts from CD200
−/−
mice differentiated at a reduced rate. Activation of the NF-κB and MAP kinase signaling pathways downstream of RANK, a receptor that plays a central role in the differentiation of osteoclasts, was depressed in these cells. A soluble recombinant protein that included the extracellular domain of CD200 rescued the fusion of CD200
−/−
macrophages and their activation downstream of RANK. Conversely, addition of a soluble recombinant protein that included the extracellular domain of CD200R or short-hairpin RNA-mediated silencing of the expression of CD200R prevented fusion. Thus CD200 engagement of the CD200R at the initiation of macrophage fusion regulated further differentiation to osteoclasts. Consistent with
in vitro
observations, CD200
−/−
mice contained fewer osteoclasts and accumulated more bone than CD200
+/+
mice. The CD200-CD200R axis is therefore a putative regulator of bone mass, via the formation of osteoclasts.
T cell activation requires mitochondrial translocation to the immunological synapse
Authors: Quintana Ariel , Schwindling Christian , Wenning Anna S. , Becherer Ute , Rettig Jens , Schwarz Eva C. , Hoth Markus
Published: August 2007

T helper (Th) cell activation is required for the adaptive immune response. Formation of the immunological synapse (IS) between Thcells and antigen-presenting cells is essential for Thcell activation. IS formation induces the polarization and redistribution of many signaling molecules; however, very little is known about organelle redistribution during IS formation in Thcells. We show that formation of the IS induced cytoskeleton-dependent mitochondrial redistribution to the immediate vicinity of the IS. Using total internal reflection microscopy, we found that upon stimulation, the distance between the IS and mitochondria was decreased to values <200 nm. Consequently, mitochondria close to the IS took up more Ca2+than the ones farther away from the IS. The redistribution of mitochondria to the IS was necessary to maintain Ca2+influx across the plasma membrane and Ca2+-dependent Thcell activation. Our results suggest that mitochondria are part of the signaling complex at the IS and that their localization close to the IS is required for Thcell activation.
Phycobilin:cystein-84 biliprotein lyase, a near-universal lyase for cysteine-84-binding sites in cyanobacterial phycobiliproteins
Authors: Zhao Kai-Hong , Su Ping , Tu Jun-Ming , Wang Xing , Liu Hui , Plöscher Matthias , Eichacker Lutz , Yang Bei , Zhou Ming , Scheer Hugo
Published: August 2007

Phycobilisomes, the light-harvesting complexes of cyanobacteria and red algae, contain two to four types of chromophores that are attached covalently to seven or more members of a family of homologous proteins, each carrying one to four binding sites. Chromophore binding to apoproteins is catalyzed by lyases, of which only few have been characterized in detail. The situation is complicated by nonenzymatic background binding to some apoproteins. Using a modular multiplasmidic expression-reconstitution assay in
Escherichia coli
with low background binding, phycobilin:cystein-84 biliprotein lyase (CpeS1) from
Anabaena
PCC7120, has been characterized as a nearly universal lyase for the cysteine-84-binding site that is conserved in all biliproteins. It catalyzes covalent attachment of phycocyanobilin to all allophycocyanin subunits and to cysteine-84 in the β-subunits of C-phycocyanin and phycoerythrocyanin. Together with the known lyases, it can thereby account for chromophore binding to all binding sites of the phycobiliproteins of
Anabaena
PCC7120. Moreover, it catalyzes the attachment of phycoerythrobilin to cysteine-84 of both subunits of C-phycoerythrin. The only exceptions not served by CpeS1 among the cysteine-84 sites are the α-subunits from phycocyanin and phycoerythrocyanin, which, by sequence analyses, have been defined as members of a subclass that is served by the more specialized E/F type lyases.
An inducible lambdoid prophage encoding cytolethal distending toxin (Cdt-I) and a type III effector protein in enteropathogenic
Escherichia coli
Authors: Asakura Masahiro , Hinenoya Atsushi , Alam Mohammad S. , Shima Kensuke , Zahid Shamim Hasan , Shi Lei , Sugimoto Norihiko , Ghosh A. N. , Ramamurthy T. , Faruque Shah M. , Nair G. Balakrish , Yamasaki Shinji
Published: August 2007

Cytolethal distending toxins (CDTs) are inhibitory cyclomodulins, which block eukaryotic cell proliferation and are produced by a diverse group of Gram-negative bacteria, including
Escherichia coli
strains associated with intestinal and extraintestinal infections. However, the mode of transmission of the toxin gene clusters among diverse bacterial pathogens is unclear. We found that Cdt-I produced by enteropathogenic
E. coli
strains associated with diarrhea is encoded by a lambdoid prophage, which is inducible and infectious. The genome of Cdt-I converting phage (CDT-1Φ) comprises 47,021 nucleotides with 60 predicted ORFs organized into six genomic regions encoding the head and tail, virulence, integrase, unknown functions, regulation, and lysis. The genomic organization of CDT-1Φ is similar to those of SfV, a serotype-converting phage of
Shigella flexneri
, and UTI89, a prophage identified in uropathogenic
E. coli
. Besides the
cdtI
gene cluster, the virulence region of CDT-1Φ genome contains sequences homologous to a truncated cycle inhibiting factor and a type 3 effector protein. Mutation analysis of susceptible
E. coli
strain C600 suggested that the outer membrane protein OmpC is a putative receptor for CDT-1Φ. CDT-1Φ genome was also found to integrate into the host bacterial chromosome forming lysogens, which produced biologically active Cdt-I. Furthermore, phage induction appeared to cause enhanced toxigenicity of the
E. coli
strains carrying lysogenic CDT-1Φ. Our results suggest that CDT-1Φ is the latest member of a growing family of lambdoid phages encoding bacterial cyclomodulins and that the phage may have a role in horizontal transfer of these virulence genes.
Effect of the nonreducing end of
Shigella dysenteriae
type 1 O-specific oligosaccharides on their immunogenicity as conjugates in mice
Authors: Pozsgay Vince , Kubler-Kielb Joanna , Schneerson Rachel , Robbins John B.
Published: August 2007

Endemic and epidemic shigellosis, an acute invasive disease of the lower intestines, afflicts millions of people worldwide with an estimated one million fatalities per annum at a low infectious dose. Our approach to vaccine development against
Shigella
is based on the hypothesis that serum IgG antibodies to the O-specific polysaccharide (O-SP) domains of the LPS of these organisms confer protection to infection. The synthetic oligosaccharides corresponding to the tetrasaccharide repeating unit of the O-SP of
Shigella dysenteriae
type 1 covalently linked to human serum albumin elicited O-SP-specific IgG in mice. The antibody levels were a function of both the saccharide chain length and their loading on the protein. These synthetic saccharide conjugates elicited significantly higher levels of IgG anti O-SP than conjugates prepared with the O-SP from the bacteria. Here, we evaluated the influence of the nonreducing terminal monosaccharide on the serum antibody response. To this end, we prepared synthetic oligosaccharides comprising hexa- to tridecasaccharide fragments of the native O-SP, having one of the four monosaccharide residues that constitute the repeating unit at their termini and bound them to BSA by a single-point attachment. The conjugates contained an average of 19 saccharide chains per BSA. The synthetic oligosaccharides inhibited the binding of serum raised against whole bacteria to its LPS to a similar extent but lower than the native O-SP. The highest anti-LPS levels were elicited by conjugates having
N
-acetylglucosamine (10-mer) or galactose residues (7- and 11-mers) at their nonreducing termini.
Brain magnetic resonance imaging does not contribute to the diagnosis of chronic neuroborreliosis
Authors: Aalto A. , Sjöwall J. , Davidsson L. , Forsberg P. , Smedby Ö.
Published: August 2007

Background: Borrelia infections, especially chronic neuroborreliosis (NB), may cause considerable diagnostic problems. This diagnosis is based on symptoms and findings in the cerebrospinal fluid but is not always conclusive.

Purpose: To evaluate brain magnetic resonance imaging (MRI) in chronic NB, to compare the findings with healthy controls, and to correlate MRI findings with disease duration.

Material and Methods: Sixteen well-characterized patients with chronic NB and 16 matched controls were examined in a 1.5T scanner with a standard head coil. T1- (with and without gadolinium), T2-, and diffusion-weighted imaging plus fluid-attenuated inversion recovery (FLAIR) imaging were used.

Results: White matter lesions and lesions in the basal ganglia were seen in 12 patients and 10 controls (no significant difference). Subependymal lesions were detected in patients down to the age of 25 and in the controls down to the age of 43. The number of lesions was correlated to age both in patients (ρ = 0.83, P<0.01) and in controls (ρ = 0.61, P<0.05), but not to the duration of disease. Most lesions were detected with FLAIR, but many also with T2-weighted imaging.

Conclusion: A number of MRI findings were detected in patients with chronic NB, although the findings were unspecific when compared with matched controls and did not correlate with disease duration. However, subependymal lesions may constitute a potential finding in chronic NB.
Ultrasonography and core needle biopsy in the differential diagnosis of fibroadenoma and tumor phyllodes
Authors: Bode M. K. , Rissanen T. , Apaja-Sarkkinen M.
Published: August 2007

Background: The diagnosis of phyllodes tumors of the breast is challenging due to many similarities with common fibroadenomas.

Purpose: To determine the diagnostic accuracy of core needle biopsy in diagnosing phyllodes tumors and to analyze the ultrasonographic (US) features of phyllodes tumors and fibroadenomas.

Material and Methods: From 1999 to 2003, 1010 breast lesions underwent imaging-guided core needle biopsy. Of these, 57 fibroadenomas and 12 phyllodes tumors were removed surgically. The US and needle biopsy results of a total of 64 lesions (52 fibroadenomas and 12 phyllodes tumors) were further analyzed, compared, and correlated with surgical histological results.

Results: The median sonographic sizes of the phyllodes tumors and the fibroadenomas were 3.2 cm and 1.6 cm, respectively. At US, 58% of the phyllodes tumors (7/12) were classified as equivocal or suspicious of malignancy and 42% (5/12) as probably benign, while 54% of the fibroadenomas (28/52) were classified as probably benign and 46% (24/52) as equivocal. The sensitivity, specificity, and positive and negative predictive values of core needle biopsy histology regarding tumor phyllodes were 83%, 92%, 71%, and 96%, respectively.

Conclusion: Imaging-guided core needle biopsy was accurate in differentiating between fibroadenomas and phyllodes tumors. US classification was unreliable due to considerable overlap in the findings. Combined use of US feature analysis and needle biopsy may help to avoid the misinterpretation of phyllodes as fibroadenoma.