bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural investigation of GaAs1−xBix/GaAs multiquantum wells
Authors: Tominaga Yoriko , Kinoshita Yusuke , Oe Kunishige , Yoshimoto Masahiro
Published: October 2008

GaAs 1 − x Bi x / GaAs multiquantum wells (MQWs) have been grown in the layer-by-layer mode of molecular beam epitaxy. A well-defined multilayered structure of the MQWs has been confirmed by cross-sectional transmission microscopy and high-resolution x-ray diffraction measurements. Photoluminescence has been observed from GaAs1−xBix/GaAs MQW at room temperature. The MQW structures have been confirmed to be thermally stable even after annealing up to 800 °C, although they need to be grown at a low temperature (350–400 °C) for Bi incorporation.
High temperature electron spin relaxation in bulk GaAs
Authors: Oertel S. , Hübner J. , Oestreich M.
Published: October 2008

Temperature and electron density dependent measurements of the electron spin relaxation in bulk GaAs are performed using time- and polarization-resolved photoluminescence spectroscopy. The electron spin relaxation time is dominated in the high temperature regime by the D’yakonov-Perel’ [M. I. D’yakonov and V. I. Perel’, Sov. Phys. Solid State 13, 3023 (1972)] spin relaxation mechanism and decreases for negligible electron densities from 42 ps at 300 K to 20 ps at 400 K. The measured spin relaxation times are compared with numerical calculations which include electron-phonon momentum scattering and have no adjustable parameters.
Temperature characteristics and development of field-induced phase transition in relaxor ferroelectric Pb(Mg1/3Nb2/3)0.87Ti0.13O3 ceramics
Authors: Peräntie J. , Hagberg J. , Uusimäki A. , Jantunen H.
Published: October 2008

Ferroelectric phase inducing threshold electric field Eth and its temperature dependence were determined in relaxor ferroelectric 0.87Pb(Mg1/3Nb2/3)O3−0.13PbTiO3 (PMN–13PT) ceramics by measuring dielectric response on a dc field pulse. Evolution of the induced ferroelectricity was observed by means of polarization measurements. An inducing threshold field was found to have a minimum of Eth,min=1.55 kV/cm at T=−5 °C. In contrast to pure PMN, which shows a minimum threshold field near the depolarization temperature, the temperature of the minimum threshold field differs by an amount of ΔT=23 °C from the depolarization temperature Tdp=18 °C in PMN-13PT.
Optical constants of silicon in near infrared region
Authors: Mendeleyev V. Ya. , Skovorodko S. N. , Lubnin E. N. , Prosvirikov V. M.
Published: October 2008

Refractive index (n) and extinction coefficient (χ) spectra for n-type silicon with impurity concentrations Ni=2.3×1012 cm−3 and Ni=4.5×1018 cm−3 are determined from measured reflectance and transmittance of silicon samples in the 0.7–1.8 μm range. In the 0.81–0.92 μm range, the spectra have a region of the anomalous dispersion and peaks, which are associated with interband transitions. It was found that the increase in Ni leads to increasing n and χ in the ranges of 0.70–0.81 and 0.90–1.80 μm, respectively, and decreasing n in the 0.86–1.80 μm range. For Ni=2.3×1012 cm−3, χ depends slightly on wavelength in the 1.15–1.8 μm range.
Improvement in carrier transport and recombination of white phosphorescent organic light-emitting devices using a composite blue emitter
Authors: Lee Meng-Ting , Lin Jin-Sheng , Chu Miao-Tsai , Tseng Mei-Rurng
Published: October 2008

We demonstrate high-efficiency white phosphorescent organic light-emitting devices (PHOLEDs) based on a yellow and composite blue emitters. The composite blue emitter is constructed from a wide-band-gap host, organometallic iridium dopant, and a carrier-transporting material. Under the same driving current density and emissive color, the current efficiency of the white PHOLEDs can be enhanced by a factor of 1.4 comparing to that of using typical blue emitter composed of host and dopant only. Attaching an outcoupling enhancement film onto glass substrate, the white PHOLEDs with a current efficiency of 47 cd/A, a power efficiency of 32 lm/W, and a CIEx,y (CIE: Commission Internationale d'Eclairage) of (0.40,0.44) at a practical brightness of 1000 cd/m2 can be achieved.
Optical excitation and characterization of gigahertz acoustic resonances in optical fiber tapers
Authors: Kang Myeong Soo , Brenn André , Wiederhecker Gustavo S. , Russell Philip St.J.
Published: October 2008

Transverse acoustic resonances at gigahertz frequencies are excited by electrostriction in the few-micrometer-thick waists of low-loss optical fiber tapers of up to 40 cm long. A pump-probe technique is used in which the resonances are excited by a train of optical pulses and probed in a Sagnac interferometer. Strong radially symmetric acoustic resonances are observed and the dependence of their frequencies on taper thickness is investigated. Such easily reconfigurable acousto-optic interactions may have applications in the high-frequency mode locking of fiber lasers.
Spin-splitting in an AlxGa1−xN/GaN nanowire for a quantum-ring interferometer
Authors: Lo Ikai , Pang Wen-Yuan , Chen Yen-Liang , Hsu Yu-Chi , Chiang Jih-Chen , Lin Wei-Hsin , Chiu Wan-Ting , Tsai Jenn-Kai , Chen Chun-Nan
Published: October 2008

An Al0.18Ga0.82N/GaN heterostructure was used to fabricate a ballistic nanowire with a wire width of 200 nm by focused ion beam. We observed the beating Shubnikov–de Haas oscillations in the nanowire with a spin-splitting energy of (2.4±0.3) meV. Based on the results, we proposed a spin-Hall quantum-ring interferometer made of AlxGa1−xN/GaN nanowires for spintronic applications.
Direct measurements of the energy flux due to chemical reactions at the surface of a silicon sample interacting with a SF6 plasma
Authors: Dussart R. , Thomann A. L. , Pichon L. E. , Bedra L. , Semmar N. , Lefaucheux P. , Mathias J. , Tessier Y.
Published: October 2008

Energy exchanges due to chemical reactions between a silicon surface and a SF6 plasma were directly measured using a heat flux microsensor (HFM). The energy flux evolution was compared with those obtained when only few reactions occur at the surface to show the part of chemical reactions. At 800 W, the measured energy flux due to chemical reactions is estimated at about 7 W cm−2 against 0.4 W cm−2 for ion bombardment and other contributions. Time evolution of the HFM signal is also studied. The molar enthalpy of the reaction giving SiF4 molecules was evaluated and is consistent with values given in literature.
Photoreflectance of InN and InN:Mg layers: An evidence of Fermi level shift toward the valence band upon Mg doping in InN
Authors: Kudrawiec R. , Suski T. , Serafińczuk J. , Misiewicz J. , Muto D. , Nanishi Y.
Published: October 2008

Photoreflectance (PR) has been applied to study the energy-gap related absorption in undoped and Mg-doped InN layers. This technique, due to its sensitivity to built-in electric fields, enables studies of the Fermi level position inside an InN bulk. Narrow PR resonance at 0.68 eV has been observed in the unintentionally doped n-InN layer at 10 K. Due to Mg doping this resonance broadens drastically and exhibits the Franz–Keldysh oscillations typical for band-to-band absorption in a region with strong band bending. Such changes in PR spectra are evidences of a strong Fermi level shift toward the valence band due to Mg doping in the probed bulklike region of a sample.
Ferromagnetism induced by defect complex in Co-doped ZnO
Authors: Liu En-Zuo , He Yan , Jiang J. Z.
Published: October 2008

The effect of Al donor and O vacancy (VO) on the magnetic properties of Co-doped ZnO has been studied by first-principles calculations. It is found that only Al donor cannot induce ferromagnetism (FM) in Co-doped ZnO but can provide additional electrons, which results in the enhancement of Fermi level. The presence of VO makes the Co empty 3d-t2g minority state broadened, and a t2g-VO hybrid level at the conduction band minimum forms. The combination of Al donor and VO results in a charge transfer to the Co empty 3d-t2g minority states, which induces a strong carrier-mediated FM interaction. Our results give an explanation for the controversial magnetic properties of (Co, Al)-codoped ZnO reported in the literature.
Effect of increased surface area of stainless steel substrates on the efficiency of dye-sensitized solar cells
Authors: Yun Ho-Gyeong , Jun Yongseok , Kim Jongdae , Bae Byeong-Soo , Kang Man Gu
Published: October 2008

In order to increase the electrical contact area between TiO2 particles and stainless steel (StSt) substrates of the dye-sensitized solar cells (DSSCs), StSt foil was roughened electrochemically using sulfuric acid with some additives. Compared with the DSSC with nontreated StSt substrate, DSSC with this roughened StSt substrate showed a 33% increase in light-to-electricity conversion efficiency with negligible effect on open circuit voltage (Voc) and fill factor. Electrochemical impedance spectroscopy clearly confirmed that the increased performance was due to a decreased electrical resistance at the TiO2/StSt interface.
Ideal laminate theory for water transport analysis of metal-coated polymer films
Authors: Jang Changsoo , Cho Young-Rae , Han Bongtae
Published: October 2008

We propose and validate a diffusion model, based on the ideal laminate theory (ILT), to describe water transport through metal-coated polymer films for barrier applications. The physical properties required for numerical implementation are studied. The analysis reveals that the solubility of the metallic coating is not required for an accurate water transport analysis, which makes the ILT-based model practical. The model is implemented numerically and the results are compared with the experimentally measured transient water weight gain of PET films with Al and Cr coatings to corroborate the validity of the model.
12
W
peak-power 10ps duration optical pulse generation by gain switching of a single-transverse-mode GaInN blue laser diode
Authors: Kono Shunsuke , Oki Tomoyuki , Miyajima Takao , Ikeda Masao , Yokoyama Hiroyuki
Published: October 2008

We have generated optical pulses at 405nm from a single-transverse-mode GaInN blue laser diode under intensive gain-switching operation with a minimum pulse duration of less than 8ps. The maximum optical peak power was as high as 12W with a pulse width of 10ps. The peak power obtained is the highest value for optical pulses ever generated from a single transverse-mode GaInN laser diode.
Crystallographically oriented Zn nanocrystals formed in ZnO by Mn+-implantation
Authors: Li Y. J. , Zhang B. , Lu W. , Wang Y. , Zou J.
Published: October 2008

The nanostructural characteristics of ZnO implanted with Mn+ to doses ranging from 1×1015to1×1017cm−2 are systematically studied for both as-implanted and postannealed cases. The detailed structural characterizations confirmed that the Mn+ implantation and postannealing result in (1) the formation of crystallographically orientated Zn nanocrystals in the ZnO matrix and (2) Mn atoms occupy the Zn sites in ZnO.
Carrier mobility, structural order, and solar cell efficiency of organic heterojunction devices
Authors: Street R. A.
Published: October 2008

The loss mechanisms limiting solar cell efficiency in organic heterojunction photodiodes are discussed. We show that the energy loss when the exciton is split, and absence of Langevin recombination at the interface, are related to the magnitude of the electron-phonon interaction and the wavefunction extent of the electron and hole. In contrast to several recent publications, it is argued that well-ordered, high mobility organic materials will provide higher efficiency cells.
Evolution of infrared photoreflectance lineshape with temperature in narrow-gap HgCdTe epilayers
Authors: Shao Jun , Ma Lili , Lü Xiang , Lu Wei , Wu Jun , Zha F.-X. , Wei Y.-F. , Li Z.-F. , Guo S.-L. , Yang J.-R. , He Li , Chu J.-H.
Published: October 2008

Temperature-dependent (11–290K) infrared photoreflectance (PR) measurements are performed on as-grown arsenic-doped HgCdTe epilayers in a midinfrared spectral region. Main PR features near bandedge manifest clear evolution of lineshape with temperature, of which the fittings identify besides a band-band process several below-gap processes. Analyses show that these features are due to photomodulation-induced screening of donor-acceptor pairs and photomodulation of band- impurity and band-band reflectance, their intensities correlate to the joint concentration of the involved energetic states. Temperature-dependent infrared PR may be a right optical spectroscopy for identifying impurity levels in semiconductors such as HgCdTe with high-density impurities.
In situ measurement of the permittivity of helium using microwave NbN resonators
Authors: Grabovskij G. J. , Swenson L. J. , Buisson O. , Hoffmann C. , Monfardini A. , Villégier J.-C.
Published: October 2008

By measuring the electrical transport properties of superconducting NbN quarter-wave resonators in direct contact with a helium bath, we have demonstrated a high-speed and spatially sensitive sensor for the permittivity of helium. In our implementation an ∼10−3mm3 sensing volume is measured with a bandwidth of 300kHz in the temperature range of 1.8–8.8K. The minimum detectable change in the permittivity of helium is calculated to be ∼6×10−11ϵ0∕Hz1∕2 with a sensitivity of the order of 10−13ϵ0∕Hz1∕2 easily achievable. Potential applications include operation as a fast, localized helium thermometer and as a transducer in superfluid hydrodynamic experiments.
The correlation between pentatomic and heptatomic carbon rings and stress of hydrogenated amorphous carbon films prepared by dc-pulse plasma chemical vapor deposition
Authors: Wang Qi , Wang Chengbing , Wang Zhou , Zhang Junyan , He Deyan
Published: October 2008

Hydrogenated diamondlike carbon films were prepared at different reactive times by dc-pulse plasma chemical vapor deposition technique. The thickness of the film increased significantly with the reactive time, and the stress is just 0.9GPa when the thickness of the film increased to 2μm. The structure analysis by high resolution transmission electron microscopy, Raman spectroscopy, x-ray photoelectron spectroscopy, and Fourier transform infrared spectra revealed a close relationship between the residual compressive stress and the microstructure of the films, which nanometer scale curved graphite sheets with pentatomic and heptatomic rings bestowed the film lower stress.
Low voltage and very high efficiency deep-blue phosphorescent organic light-emitting devices
Authors: Eom Sang-Hyun , Zheng Ying , Chopra Neetu , Lee Jaewon , So Franky , Xue Jiangeng
Published: October 2008

We report on very high efficiency deep-blue phosphorescent organic light-emitting devices (PHOLEDs) based on iridium(III) bis(4′,6′-difluorophenylpyridinato)tetrakis(1-pyrazolyl)borate (FIr6). Dual emissive layers consisting of an N,N′-dicarbazolyl-3,5-benzene layer doped with 4wt% FIr6 and a p-bis(triphenylsilyly)benzene layer doped with 25wt% FIr6 were employed to maximize exciton generation on FIr6 molecules. Combined with the p-i-n device structure, we achieved a low turn-on voltage of 3.2V and very high power efficiencies of 25±2lm∕W at 100cd∕m2 and 20±2lm∕W at 1000cd∕m2 for such deep-blue PHOLEDs with peak emission at a wavelength of 458nm.
Near-ultraviolet excitable orange-yellow Sr3(Al2O5)Cl2:Eu2+ phosphor for potential application in light-emitting diodes
Authors: Tang Yu-Sheng , Hu Shu-Fen , Ke Wei-Chih , Lin Chun Che , Bagkar Nitin C. , Liu Ru-Shi
Published: October 2008

Sr 3 ( Al 2 O 5 ) Cl 2 phosphor doped with Eu2+ was prepared by a soli-state reaction. This phosphor emits a broad orange-yellow luminescence with a peak wavelength of 620nm and a full width at half maximum of about 175nm under near-ultraviolet (NUV) excitation at ∼400nm. Yellow light-emitting diodes (LEDs) for general lighting were fabricated by combining Sr3(Al2O5)Cl2:Eu2+ phosphor with an NUV chip. The phosphor-converted LEDs had a color temperature of about 2300K and their color rendering index was 74.
Reduction in dark current using resonant tunneling barriers in quantum dots-in-a-well long wavelength infrared photodetector
Authors: Barve A. V. , Shah S. Y. , Shao J. , Vandervelde T. E. , Shenoi R. V. , Jang W.-Y. , Krishna S.
Published: October 2008

We report the use of resonant tunneling (RT) assisted barriers to reduce the dark current in quantum dots-in-a-well (DWELL) infrared photodetectors. Designed RT barriers allow energy-selective extraction of photoexcited carriers while blocking a continuum of energies. Over two orders of magnitude reduction in the dark current in the RT-DWELL device over a control sample without RT-DWELL at 77K has been demonstrated. Specific detectivity (D*) of 3.6×109cmHz1∕2W−1 at 77K at λpeak=11μm with a conversion efficiency of 5.3% was obtained in the RT-DWELL device. D* for the RT-DWELL device is five times higher than that of the control sample.
Different optical absorption edges in AlN bulk crystals grown in m- and c-orientations
Authors: Lu P. , Collazo R. , Dalmau R. F. , Durkaya G. , Dietz N. , Sitar Z.
Published: October 2008

AlN single crystals were grown on m-plane (101¯0) and c-plane (0001¯) AlN seeds under identical growth conditions. The m-plane AlN crystals exhibited substantially lower oxygen incorporation, ∼1018cm−3, than the c-plane crystals, ∼1019cm−3. By investigating optical transmission spectra, m-plane AlN had absorption bands at 4.05 and 4.35eV, while c-plane AlN had an absorption band edge at 4.85eV. These below bandgap absorption bands strongly correlate with the reported transitions related to Al vacancy-impurity complexes, such as the complex of an Al vacancy and two oxygen atoms, (VAl–2ON)1− and the complex of an Al vacancy and one oxygen atom, (VAl–ON)2−, becoming the major cause for the poor, below bandgap optical transparency (α>200cm−1) of these crystals.
Highly efficient, deep-blue phosphorescent organic light emitting diodes with a double-emitting layer structure
Authors: Fukagawa H. , Watanabe K. , Tsuzuki T. , Tokito S.
Published: October 2008

We have demonstrated a highly efficient, deep-blue organic light-emitting diode (OLED) using a host material with a high triplet energy. The OLED device that we have prepared utilizes a phosphorescent guest material, iridium(III)bis(4′,6′,-difluorophenylpyridinato)tetrakis(1-pyrazolyl)borate, exhibits a peak quantum efficiency of about 15.7%. We employed a double-emitting layer (DEL) structure that distributes the carrier recombination region within the device. In this DEL structure, the emission mechanism is such that the energy transfers from the host material in one emitting layer, and the other emitting layer provides for direct charge trapping in the guest material. This DEL structure proved to be quite useful in achieving the reported device characteristics.
Growing up in the New New York: Youth Space, Citizenship, and Community Change in a Hyperglobal City
Authors: Driskell David , Fox Carly , Kudva Neema
Published: October 2008

We describe a participatory-action research program through which a group of young people in Jackson Heights, Queens, navigates an emergent youth geography defined by the shifting patterns and dynamics of immigration as well as by ongoing processes of adultification, neglect, and active exclusion. In this terrain, space, place and citizenship are intertwined in new and complex ways, especially for young people who are in the process of forming their identity as individuals and citizens. Through their work and actions in place, they demonstrate that, even in an environment where public space has been significantly eroded, place not only can continue to be central to the lives of young people, but also can provide the locus for an expanded citizenship.
Organisational Archetypes for Dutch Housing Associations
Authors: Gruis Vincent
Published: October 2008

Since the Dutch government strongly reduced its control of housing associations in the 1990s, the housing associations have been developing different organisational strategies. In this paper I present a theoretical classification of organisational archetypes for housing associations, based on a distinction between prospectors and defenders, and between housing associations with a relatively strong social orientation and those with a more business-like, commercial, orientation. The four resulting organisational archetypes are worked out on the basis of their range of activities, innovations, organisational structure, available expertise (human resources), strategic management systems, and their approach towards local accountability. Furthermore, the archetypes are illustrated and tested by case studies. It is concluded that the distinction between prospectors and defenders is applicable to the housing associations, but that the distinction between social and commercial orientation is harder to apply to practice.
Photodynamic Therapy: Porphyrins and Phthalocyanines as Photosensitizers
Authors: Moreira Leonardo Marmo , Vieira dos Santos Fábio , Lyon Juliana Pereira , Maftoum-Costa Maira , Pacheco-Soares Cristina , Soares da Silva Newton
Published: October 2008

The present work is focussed on the principles of photodynamic therapy (PDT), emphasizing the photochemical mechanisms of reactive oxygen species formation and the consequent biochemical processes generated by the action of reactive oxygen species on various biological macromolecules and organelles. This paper also presents some of the most used photosensitizers, including Photofrin, and the new prototypes of photosensitizers, analysing their physicochemical and spectroscopic properties. At this point, the review discusses the therapeutic window of absorption of specific wavelengths involving first- and second-generation photosensitizers, as well as the principal light sources used in PDT. Additionally, the aggregation process, which consists in a phenomenon common to several photosensitizers, is studied. J-aggregates and H-aggregates are discussed, along with their spectroscopic effects. Most photosensitizers have a significant hydrophobic character; thus, the study of the types of aggregation in aqueous solvent is very relevant. Important aspects of the coordination chemistry of metalloporphyrins and metallophthalocyanines used as photosensitizers are also discussed. The state-of-the-art in PDT is evaluated, discussing recent articles in this area. Furthermore, macrocyclic photosensitizers, such as porphyrins and phthalocyanines, are specifically described. The present review is an important contribution, because PDT is one of the most auspicious advances in the therapy against cancer and other non-malignant diseases.
N,N-Dialkyl-N′-Chlorosulfonyl Chloroformamidines in Heterocyclic Synthesis. Part VII 4-Dialkylamino[1,2,3,5]Benzoxathiadiazepine Dioxides and 4-Dialkylamino-[2,1,3,5]Benzothiatriazepine Dioxides
Authors: Cablewski Teresa , Forsyth Craig M. , Francis Craig L. , Liepa Andris J. , Tran Victor
Published: October 2008

N,N-dialkyl-N′-chlorosulfonyl chloroformamidines 1 reacted with 2-aminophenols 2 to give 4-dialkylamino[1,2,3,5]benzoxathiadiazepine dioxides 3, which are examples of a new ring system. Reaction of 1 with 1,2-diaminobenzenes 7 afforded 4-dialkylamino[2,1,3,5]benzothiatriazepine dioxides 8 and 9, which are new derivatives of a rare ring system. Some N-alkyl and N-acyl derivatives of 3 and 8 were prepared to demonstrate the potential of these compounds as novel scaffolds for synthetic and medicinal chemistry.
Potential of three aquatic predators to control mosquitoes in the presence of alternative prey: a comparative experimental assessment
Authors: Kumar R. , Muhid P. , Dahms H.-U. , Tseng L.-C. , Hwang J.-S.
Published: October 2008

Predator-induced control of pests depends on the predator’s preference for the target pest over naturally co-occurring prey species. We compared the larvivorous efficiency of three common freshwater predators: mosquitofish (Gambusia affinis; Baird and Girard, 1854), dragonfly naiads (Zyxomma petiolatum; Rambur, 1842) and copepods (Mesocyclops aspericornis; Daday, 1906) on different instars and the relative abundances of the mosquito Anopheles stephensi (Liston, 1901) in the presence of alternative cladoceran prey, either Moina macrocopa (Straus, 1820) or Daphnia similoides (Hudec, 1991). Larval removal rate decreased with increasing larval size and instar stage. The maximum consumption rate was by mosquitofish, followed by dragonfly naiads and copepods. The presence of either of the alternative prey significantly reduced larval consumption by all three predators, except in the D. similoides–mosquito larvae combination for naiads. Mosquitofish and copepods preferred early instars of the mosquito. Prey selectivity indices for early mosquito instars against D. similoides did not differ between mosquitofish and copepods, whereas naiads had significantly lower index values than the other two predators. Considering the negative impacts of mosquitofish on native assemblages, that is, its invasiveness and its lower selectivity for mosquito larvae, our results suggest that the feasibility of using copepods in large-scale control programs needs to be evaluated.
Temporal trends in benthic macrofauna composition in response to seasonal variation in a tropical coastal lagoon, Celestun, Gulf of Mexico
Authors: Hernández-Guevara Norma A. , Pech Daniel , Ardisson Pedro-Luis
Published: October 2008

Aquatic habitats in some tropical coastal environments can change seasonally, causing changes in the community structure of the benthic macrofauna. A tropical coastal lagoon, the Celestun lagoon, on the north-west Yucatan peninsula, was sampled seasonally and faunal, water and sediment data were compared with conditions during the 1994–1995 weather cycle across a grid of 12 sites distributed along the lagoon’s salinity gradient. Habitat variation was expressed as physical factors associated with the water column (e.g. salinity) and bottom sediments (e.g. interstitial salinity, texture), whereas the benthic community response was assessed through changes in species composition, diversity and dominance. Taxonomic dominance varied according to changes in seasonal habitat characteristics. During the season of strong northerly winds (‘nortes’), molluscs dominated and polychaetes almost disappeared. Polychaetes then recovered during the dry season, becoming as common as crustaceans and molluscs. Finally, during the rainy season, polychaetes became the dominant group and molluscs declined. A conceptual model summarising the community structure changes associated with key physical and biotic factors is proposed. The results indicate that the benthic community of the Celestun lagoon is a resilient one, largely driven by natural weather variability in this tropical ecosystem to a greater extent than previously suggested.
Do lowland habitats represent barriers to dispersal for a rainforest mayfly, Bungona narilla, in south-east Queensland?
Authors: McLean Alison J. , Schmidt Daniel J. , Hughes Jane M.
Published: October 2008

Long-distance dispersal might be an important mechanism for the maintenance of aquatic insect populations in heterogeneous landscapes. However, these events can be difficult to measure by direct observation because the techniques can be time-consuming, expensive and technically difficult. When dispersal results in gene flow within and between populations, patterns of variation can be detected by genetic methods. The levels of population genetic structuring and the relationship between gene flow and geographical distance were assessed in the mayfly species Bungona narilla (Harker, 1957) in rainforest streams in south-east Queensland that are separated by lowland habitats. An analysis of molecular variance based on mitochondrial DNA data, using a fragment of the cytochrome oxidase I gene, revealed significant differentiation between regions, suggesting that maternal gene flow was restricted. A nested clade analysis revealed patterns of historical (contiguous) range expansions and recent restricted gene flow along with some long-distance dispersal events. Our analyses have shown that populations of B. narilla are significantly structured throughout the species range in south-east Queensland and that the low elevation habitats separating the northern and southern populations are restricting gene flow to some extent.
Photodegradation, interaction with iron oxides and bioavailability of dissolved organic matter from forested floodplain sources
Authors: Howitt Julia A. , Baldwin Darren S. , Rees Gavin N. , Hart Barry T.
Published: October 2008

Photochemical degradation of dissolved organic matter (DOM) can influence food webs by altering the availability of carbon to microbial communities, and may be particularly important following periods of high DOM input (e.g. flooding of forested floodplains). Iron oxides can facilitate these reactions, but their influence on subsequent organic products is poorly understood. Degradation experiments with billabong (= oxbow lake) water and river red gum (Eucalyptus camaldulensis) leaf leachate were conducted to assess the importance of these reactions in floodplain systems. Photochemical degradation of DOM in sunlight-irradiated quartz tubes (with and without amorphous iron oxide) was studied using gas chromatography and UV-visible spectroscopy. Photochemical reactions generated gaseous products and small organic acids. Bioavailability of billabong DOM increased following irradiation, whereas that of leaf leachate was not significantly altered. Fluorescence excitation-emission spectra suggested that the humic component of billabong organic matter was particularly susceptible to degradation, and the source of DOM influenced the changes observed. The addition of amorphous iron oxide increased rates of photochemical degradation of leachate and billabong DOM. The importance of photochemical reactions to aquatic systems will depend on the source of the DOM and its starting bioavailability, whereas inputs of freshly formed iron oxides will accelerate the processes.
Corrigendum to: Effects of sewage discharges on microbial components in tropical coastal waters (Senegal, West Africa)
Authors: Bouvy Marc , Briand Enora , Boup Maimouna M. , Got Patrice , Leboulanger Christophe , Bettarel Yvan , Arfi Robert
Published: October 2008

Coastal ecosystems are frequently submitted to anthropogenic pressure but little is known about how the dynamics of aquatic communities can be altered. The impact of urban and industrial discharges on microbial plankton was studied in Hann Bay near Dakar (Senegal) on the Atlantic Ocean. Spatial patterns were studied using three transects, with a total of 20 stations, during two periods in May and November (before and after the seasonal upwelling), revealing a clear contrast between near shore stations and the intermediate and seaward stations. In November, phytoplankton were associated with dissolved nutrient availability (e.g. with nitrate, r = 0.76) whereas in May, phytoplankton were more correlated with microbial variables (e.g. with heterotrophic nanoflagellates, r = 0.63). Most samples (40) failed to meet the quality levels for the faecal indicator bacteria (FIB) defined by the European Union bathing water quality directive. The topography plays a major role in water circulation explaining the presence of FIB at the seaward stations. The high prevalence of FIB during the two periods suggests chronic pollution and a potential risk to recreational swimmers and fish consumers in Hann Bay. Thus, as demonstrated in various temperate systems, the decline of water quality constitutes a serious problem in many West African countries.
Age, growth, and mortality of wahoo, Acanthocybium solandri, from the Atlantic coast of Florida and the Bahamas
Authors: McBride Richard S. , Richardson Adam K. , Maki Kristin L.
Published: October 2008

Wahoo, Acanthocybium solandri, constitute an economically important fishery for many coastal nations, but assessment of this living marine resource is hampered by a lack of basic life history information. The present study demonstrates that wahoo in the western North Atlantic Ocean are short lived, grow rapidly in their first year, achieve a very large size, and have high mortality rates. The largest individuals were female and the sex ratio was significantly female-biased (298 females: 223 males: 54 unknown sex). An edge analysis showed that annuli formed primarily during winter–spring, which supported the use of sectioned otoliths for ageing wahoo. Wahoo lived a median of 1.3 years, a mean of 1.8 years, and a maximum of 9.3 years (n = 469). They had a high instantaneous mortality rate (Z = 0.98), and they grew rapidly and to a large size; von Bertalanffy growth parameters were: L∞ = 1701 mm fork length (FL), K = 0.381, to = –1.63. Females had a very similar maximum age relative to males (maximum age 9.3 v. age 9.1 years), and they had a slightly, but not significantly, lower mortality (Z = 0.91 v. 1.1) than males. Females grew slightly, although not significantly, larger than males (L∞ = 1797 v. 1555 mm FL, maximum observed = 1804 v. 1585 mm FL). Presumably the piscivorous nature of wahoo feeding, as noted by others, fuels these fast growth rates. Comparative data are very limited but it appears that the survival rate of wahoo in the western Atlantic Ocean is not different now than in the 1960s.
Effects of slight salinity increases on Moina micrura (Cladocera) populations: field and laboratory observations
Authors: Santangelo Jayme M. , Bozelli Reinaldo L. , Rocha Adriana de M. , Esteves Francisco de A.
Published: October 2008

Salinity is a well-recognised factor that shapes population dynamics and community structure through direct and indirect effects. The responses of Moina micrura (Cladocera) to slight salinity increases (up to 6.0) were evaluated through laboratory manipulative experiments and field observations at Cabiúnas lagoon (Rio de Janeiro, Brazil). From the field data, a positive relationship between M. micrura density and salinity was observed, whereas the opposite was found for other co-occurring microcrustaceans. Life-table observations from laboratory experiments showed better performance of individuals exposed to control conditions (no salt addition) and 1.0 and 2.0 of salinity. The difference between field and laboratory results may be explained considering possible direct and indirect effects of salinity on M. micrura populations. Salinity may have direct negative physiological effects in individuals. However, under natural conditions, M. micrura might benefit from reduced invertebrate predation and interspecific competition. This balance between negative and positive effects of salinity is probably more positive under natural conditions, explaining the success of M. micrura in Cabiúnas lagoon under mild salinity conditions. Although salinity negatively affects many species living in freshwater systems, slight increases may be beneficial for some species under natural conditions.
Metacognition in Taiwan: Students' calibration of comprehension and performance
Authors: Zabrucky Karen M. , Agler Lin‐Miao L. , Moore DeWayne
Published: October 2008

Researchers have increasingly investigated the role played by metacognition in students' learning and performance. Metacognition is comprised of metacognitive knowledge and metacognitive experiences, and both components of metacognition are viewed as being important to learning and performance in academic settings. Metacognitive experiences involve, in part, students' awareness of progress on cognitive tasks. Such awareness is critical to learning, for students may fail to spend additional time reviewing or studying material if they believe they have understood the material adequately. In the present study we examined Taiwanese students' ability to assess their comprehension of passages following reading as well as their ability to predict the number of questions they would be able to answer about passage content. Following an actual test on the material, students were asked to assess how many questions they felt they answered correctly about a passage (postdiction). Students were able to predict comprehension and test performance at better than chance levels and were more accurate at postdiction than prediction. Students with better performance, as measured by comprehension test scores, were better at both prediction and postdiction of comprehension performance. However, students' self‐assessments of general calibration ability did not relate to their test performance. The metacomprehension skills of Taiwanese students were quite similar to those previously found for western students, but also diverged in some respects.
Sex differences in psychological effects of exercise
Authors: Hülya Aşçı F.
Published: October 2008

The purpose of this study was to investigate sex differences in psychological effects of exercise on university students. University students (73 female and 65 male) were randomly assigned to experimental and control groups by equating sex in each group. The experimental group participated in step dance sessions of 50 min per day, 3 days per week for 10 weeks with 60–80% of their heart rate reserves. Throughout the 10‐week period, the lecture control group was told not to participate in any organized or structured exercise and participated in a lecture that was about the physiological and psychological benefits of exercise. Self‐concept, belief in external control, and trait anxiety of the groups were measured before and after the exercise program. A significant improvement in the psychological variables after the exercise program and more improvement for female exercise participants were expected. Analysis revealed no significant initial differences in self‐concept, belief in external control, and trait anxiety between the two groups or between males and females, other than family and moral/ethical self. Repeated measures analysis of variance revealed that exercise led to less belief in external control and significant improvement in physical self and identity dimensions of self‐concept for the experimental group compared to the control group. However, there was no significant difference in trait anxiety between the two groups after exercise (p>.05). Analysis also revealed that changes in belief in external control, trait anxiety, and self‐concept did not differ with regard to sex. Males and females showed no difference in their improvement on trait anxiety, belief in external control, and most dimensions of self‐concept during the 10 weeks. Only changes in personal and physical self throughout 10‐week period were different for males and females. Exerciser males improved their personal self and physical self scores more than female exercisers and male and female nonexercisers throughout the 10‐week period (p<.05).
Akt inhibition promotes autophagy and sensitizes PTEN-null tumors to lysosomotropic agents
Authors: Degtyarev Michael , De Mazière Ann , Orr Christine , Lin Jie , Lee Brian B. , Tien Janet Y. , Prior Wei W. , van Dijk Suzanne , Wu Hong , Gray Daniel C. , Davis David P. , Stern Howard M. , Murray Lesley J. , Hoeflich Klaus P. , Klumperman Judith , Friedman Lori S. , Lin Kui
Published: October 2008

Although Akt is known as a survival kinase, inhibitors of the phosphatidylinositol 3-kinase (PI3K)–Akt pathway do not always induce substantial apoptosis. We show that silencing Akt1 alone, or any combination of Akt isoforms, can suppress the growth of tumors established from phosphatase and tensin homologue–null human cancer cells. Although these findings indicate that Akt is essential for tumor maintenance, most tumors eventually rebound. Akt knockdown or inactivation with small molecule inhibitors did not induce significant apoptosis but rather markedly increased autophagy. Further treatment with the lysosomotropic agent chloroquine caused accumulation of abnormal autophagolysosomes and reactive oxygen species, leading to accelerated cell death in vitro and complete tumor remission in vivo. Cell death was also promoted when Akt inhibition was combined with the vacuolar H+–adenosine triphosphatase inhibitor bafilomycin A1 or with cathepsin inhibition. These results suggest that blocking lysosomal degradation can be detrimental to cancer cell survival when autophagy is activated, providing rationale for a new therapeutic approach to enhancing the anticancer efficacy of PI3K–Akt pathway inhibition.
Novel role for the LKB1 pathway in controlling monocarboxylate fuel transporters
Authors: Filippi Beatrice Maria , Alessi Dario R.
Published: October 2008

A question preoccupying many researchers is how signal transduction pathways control metabolic processes and energy production. A study by Jang et al. (Jang, C., G. Lee, and J. Chung. 2008. J. Cell Biol. 183:11–17) provides evidence that in Drosophila melanogaster a signaling network controlled by the LKB1 tumor suppressor regulates trafficking of an Sln/dMCT1 monocarboxylate transporter to the plasma membrane. This enables cells to import additional energy sources such as lactate and butyrate, enhancing the repertoire of fuels they can use to power vital activities.
Mortality Rates Associated With Multidrug-Resistant Acinetobacter baumannii Infection in Surgical Intensive Care Units
Authors: Daniels Titus L. , Deppen Stephen , Arbogast Patrick G. , Griffin Marie R. , Schaffner William , Talbot Thomas R.
Published: October 2008

A retrospective, propensity-matched cohort study was conducted to determine the mortality rate in patients with healthcare-associated infection (HAI) due to multidrug-resistant (MDR) Acinetobacter baumannii. The 28-day mortality rate for patients with MDR A. baumannii HAI was not significantly different than that for patients with non-MDR A. baumannii HAI. The median length of hospital stay before diagnosis of HAI was 4.5 days longer for patients with MDR A. baumannii infection than for patients with non-MDR A. baumannii infection (P <.001).
Surveillance for Surgical Site Infection (SSI) After Neurosurgery: Influence of the US or Brest (France) National Nosocomial Infection Surveillance Risk Index on SSI Rates
Authors: Lietard Claire , Thébaud Véronique , Besson Gérard , Lejeune Benoist
Published: October 2008

A total of 5,628 neurosurgical patients were observed in France to assess the occurrence of surgical site infection (SSI). Their risk of SSI was defined by calculating both the US National Nosocomial Infection Surveillance and the Brest National Nosocomial Infection Surveillance risk indexes. This study compares SSI rates stratified according to either the US or Brest (France) National Nosocomial Infection Surveillance risk index. The SSI rates were correlated with National Nosocomial Infection Surveillance data involving only local operation durations.
Linking Public Health and the Emergency Care Community: 7 Model Communities
Authors: Lerner E. Brooke , Cronin Michael , Schwartz Richard B. , Sanddal Teri L. , Sasser Scott M. , Czapranski Tim , Piazza Gina M. , Sheahan William D.
Published: October 2008

Public health and the emergency care community must work together to effectively achieve a state of community-wide disaster preparedness. The identification of model communities with good working relationships between their emergency care community and public health agencies may provide useful information on establishing and strengthening relationships in other communities. Seven model communities were identified: Boston, Massachusetts; Clark County, Nevada; Eau Claire, Wisconsin; Erie County, New York; Louisville, Kentucky; Livingston County, New York; and Monroe County, New York. This article describes these communities and provides a summary of common findings. Specifically, we recommend that communities foster respectful working relationships between agency leaders, hold regular face-to-face meetings, educate each other on their expertise and roles during a disaster, develop response plans together, work together on a day-to-day basis, identify and encourage a leader to facilitate these relationships, and share resources. (Disaster Med Public Health Preparedness. 2007;1:142–145)
Definition and Functions of Health Unified Command and Emergency Operations Centers for Large-scale Bioevent Disasters Within the Existing ICS
Authors: Burkle Frederick M. , Hsu Edbert B. , Loehr Michael , Christian Michael D. , Markenson David , Rubinson Lewis , Archer Frank L.
Published: October 2008

The incident command system provides an organizational structure at the agency, discipline, or jurisdiction level for effectively coordinating response and recovery efforts during most conventional disasters. This structure does not have the capacity or capability to manage the complexities of a large-scale health-related disaster, especially a pandemic, in which unprecedented decisions at every level (eg, surveillance, triage protocols, surge capacity, isolation, quarantine, health care staffing, deployment) are necessary to investigate, control, and prevent transmission of disease. Emerging concepts supporting a unified decision-making, coordination, and resource management system through a health-specific emergency operations center are addressed and the potential structure, function, roles, and responsibilities are described, including comparisons across countries with similar incident command systems. (Disaster Med Public Health Preparedness. 2007;1:135–141)
Addressing Gaps in Health Care Sector Legal Preparedness for Public Health Emergencies
Authors: Ransom Montrece McNeill , Goodman Richard A. , Moulton Anthony D.
Published: October 2008

Health care providers and their legal counsel play pivotal roles in preparing for and responding to public health emergencies. Lawyers representing hospitals, health systems, and other health care provider components are being called upon to answer complex legal questions regarding public health preparedness issues that most providers have not previously faced. Many of these issues are legal issues with which public health officials should be familiar, and that can serve as a starting point for cross-sector legal preparedness planning involving both the public health and health care communities. This article examines legal issues that health care providers face in preparing for public health emergencies, and steps that providers, their legal counsel, and others can take to address those issues and to strengthen community preparedness. (Disaster Med Public Health Preparedness. 2008;2:50–56)
Measuring Humanitarian Emergencies
Authors: Garfield Richard
Published: October 2008

The ability to monitor assistance, define humanitarian needs, and approach equity in the distribution of assistance has lagged behind the world’s growing commitment to responding to humanitarian emergencies. This article highlights relevant data sources to elucidate elements of an operational definition of humanitarian need. New and refined measures are proposed to assist in assessing the level of need among affected populations. An original measure that combines data on conflict and disasters to summarize the cumulative magnitude of 4 types of humanitarian threats is presented. (Disaster Med Public Health Preparedness. 2007;1:110–116)