bluuebunny/crossref_metadata_2025 huggingface dataset:
The relationship of vegetation to environmental factors in Wangsuk stream and Gwarim reservoir in Korea: II. Soil environments
Authors: Kwon Gi Jin , Lee Bo Ah , Nam Jong Min , Kim Jae Geun
Published: June 2006

This paper presents a quantitative account of vegetation–soil environmental factor relationships in the Wangsuk stream (WS) and the Gwarim reservoir (GR) in Korea. Vegetation and the following soil variables were investigated in May, August and October 2004: pH, conductivity, water content, organic matter, total nitrogen content, NH4–N content, PO4–P content, total Ca, Mg, K, and Na content, extractable Ca, Mg, K and Na content, soil texture, distance from the channel, and elevation above water level. Species richness, diversity and ratio of hydrophyte occupation in WS were different from those in GR. Species richness was higher in WS, whereas the ratio of hydrophyte occupation was higher in GR. There were large temporal and spatial variations in plant distribution in the riparian and aquatic zones of WS but only slight variations in those of GR. These differences might have arisen from differences in flooding regime, distance from the stream channel related to elevation above water level, and soil properties such as soil texture and available nutrients. The median values of organic matter, total nitrogen, NH4–N, PO4–P and extractable Ca, Mg, K and Na contents in the soil were higher in GR than in WS. Sandy loam and loamy sand were common soil types in WS and clay loam and sandy clay loam in GR. Ten vegetation groups in WS and six in GR were identified using TWINSPAN. DCCA indicated that the distance from the stream channel was most strongly related to plant distribution and this reflected the spatial distribution of plant species in WS. In both WS and GR, NH4–N content in soil and soil texture were important factors for the distribution of species in May, August and October. Spatial and temporal heterogeneity of soil variables were related to species distribution.
Wintering bird communities in newly‐formed wetland in the Yangtze River estuary
Authors: Ma Zhijun , Gan Xiaojing , Choi Chiyeung , Jing Kai , Tang Shimin , Li Bo , Chen Jiakuan
Published: June 2006

We compared wintering bird communities and their habitats among three shoals at Jiuduansha, a newly‐formed wetland in the Yangtze River estuary. The highest species richness and diversity were recorded in Shangsha, which is the highest shoal, and the highest abundance and lowest species diversity were recorded in Xiasha, which is the lowest shoal. Shangsha had the largest abundance of perching birds whereas Xiasha was the most abundant in waterbirds. Bird assemblages showed different associations with the different habitat types—perching birds were favored by reed (Phragmites australis) communities, shallow water foragers and dabbling ducks preferred sea‐bulrush (Scirpus mariqueter) communities, and moist‐soil foragers and gulls showed a preference for bare intertidal zones. All bird assemblages, however, avoided the smooth cordgrass (Spartina alterniflora) communities, which are dominated by an alien invasive plant. The composition of avian communities was related to habitat types at the three shoals. Our results suggest that the newly‐formed tidelands can provide suitable habitats for waterbirds and that the lower tidelands can attract more waterfowl than the higher tidelands. Because the shoal with low species diversity could have exclusive bird species, conservation efforts should not concentrate only on the area with high species diversity. The estuarine wetlands should be considered as a whole when conservation strategies are designed. The alien invasive plant should, moreover, be effectively controlled, to provide suitable habitats for birds.
Vascular cognitive impairment: Today and tomorrow
Authors: Chui Helena Chang
Published: June 2006

Vascular cognitive impairment (VCI) is the phenotypic outcome of a cascade of events: vascular risk factors lead to vascular disease, which causes vascular brain injury (VBI) in networks important for cognition. Both VCI and Alzheimer's disease (AD) increase exponentially with age, and their interactions are common and controversial. The ability of current consensus criteria to distinguish VCI from AD is limited. Currently, the primary and secondary prevention of VCI is essentially the same for stroke, whereas symptomatic treatment of VCI is similar to AD. An emerging database suggests that VBI contributes significantly to mild VCI and can accelerate the appearance of dementia when AD pathology is mild. Early evidence suggests that the adverse effects of VBI are submerged once AD pathology spreads into isocortex. Recently, epidemiologic studies reported associations between vascular risk factors and clinically diagnosed AD as well as stroke. If hypertension, diabetes, and hyperlipidemia truly accelerate β‐amyloidosis and tauopathy, as well as VBI, the importance of their early identification and treatment will be greatly magnified.
A review of the “State of the Art” on Mild Cognitive Impairment: The Fourth Annual Symposium
Authors: Bain Lisa J.
Published: June 2006

The fourth Annual Mild Cognitive Impairment (MCI) Symposium, held at the Eden Roc Hotel in Miami Beach Florida on February 24 and 25, 2006, brought together some 150 neuropsychologists, neurologists, and other specialists in the field to discuss the latest research on issues related to the diagnosis and progression of MCI across the broad range of cognitive and functional impairments that comprise its various subtypes. Four mini‐symposia were convened on the topics of Cognitive Reserve and MCI, the Genetics and Proteomics of Cognitive Decline, Pathogenesis of Vascular/Metabolic Cognitive Impairment, and Systemic and Psychiatric Considerations in MCI. In addition, 2 keynote addresses were delivered; one on the Rotterdam Study and the other a review of clinical trials in MCI. Participants in the symposium also discussed whether the time has come to revise current diagnostic criteria for Alzheimer's disease.
Alzheimer's Association Research Roundtable Meeting on Mild Cognitive Impairment: What have we learned?
Authors: Grundman Michael , Petersen Ronald C. , Bennett David A. , Feldman Howard H. , Salloway Stephen , Visser Pieter Jelle , Thal Leon J. , Schenk Dale , Khachaturian Zaven , Thies William ,   Alzheimer's Association Research Roundtable
Published: June 2006

The biological changes that occur in the brains of Alzheimer's disease (AD) patients are thought to begin long before the onset of clinical symptoms. Although current therapeutic agents have been approved only for patients with mild to moderate AD, Alzheimer‐type pathology in patients with mild to moderate AD is already quite advanced. One impetus for the development of the concept of mild cognitive impairment (MCI) was the attempt to recognize AD early in its clinical expression and to determine whether it is possible through therapeutic interventions to improve the memory impairment at this stage or delay further progression to dementia. To this end, several clinical trials have been conducted in patients with MCI. On September 8 and 9, 2004 a meeting of the Alzheimer's Association Research Roundtable was held at which experts in the field of MCI convened to review the collective experience from these trials and to consider potential approaches that might improve MCI clinical trials in the future. This article summarizes the presentations and discussions of that meeting.
Ganyu casual labour, famine and HIV/AIDS in rural Malawi: causality and casualty
Authors: Bryceson Deborah Fahy
Published: June 2006

Over the past ten years, Malawian peasant farming households have endured a number of material and life-threatening setbacks. The absence of subsidised fertiliser loans to farmers continues to trouble villagers a decade after their removal. Yields of both food and cash crops have been declining. Farming households' earnings from agricultural exports and remittances have decreased. The creeping and then intensified incidence of HIV/AIDS infection has led to widespread debility and death, compounded by a serious famine in 2001–03. During the famine and its aftermath, ganyu casual labour gained in importance as a source of income, especially for women and youth from poor rural households. Field evidence suggests that the highly exploitative contractual terms that employers offered widened the gap between the haves and have-nots, and fuelled the risks of contracting HIV/AIDS. Ganyu, representing an established form of labour based on mutual economic benefit between exchange agents stretching back over a century, has become synonymous with degradation and despair for the working poor.
The status and habitat of Karamoja Apalis Apalis karamojae in the Wembere Steppe, Sukumaland, Tanzania
Authors: SHAW PHILIP , MUNGAYA ELIAS
Published: June 2006

Karamoja Apalis Apalis karamojae is a globally Vulnerable warbler, restricted to north-east Uganda, north-central Tanzania and southern Kenya. Here, we describe its status and habitat in the Wembere Steppe, Sukumaland, Tanzania, an unprotected area of seasonally inundated grassland bordered partly by Acacia scrub. Although its habitat in the steppe was thought likely to span c. 175 km north–south during the 1960s to 1970s, we found the apalis to be patchily distributed over a distance of only 102 km north–south. Distance sampling yielded a density estimate of c. 7–16 birds km−2; equivalent to c. 3–7 pairs km−2, after juveniles (18% of the population) were excluded, and assuming that all adults were paired. The species occupied a very narrow foraging niche, feeding almost exclusively in Whistling Thorn Acacia drepanolobium, which accounted for 66% of woody stems in the study area, but for 95% of stems in the immediate vicinity of apalis sightings. Half of all individuals were encountered in the tallest, densest stands of A. drepanolobium, which covered less than 6% of the study area. Signs of scrub clearance, pruning and browsing were widespread in the steppe, and may have intensified during 1967–2002, when the human population in surrounding districts increased at a mean rate of c. 2–4% per year. Further research is required to determine whether our findings are representative of the species in other seasons and at other sites.
Distribution and abundance of forest birds in low-altitude habitat on Hawai'i Island: evidence for range expansion of native species
Authors: SPIEGEL CALEB S. , HART PATRICK J. , WOODWORTH BETHANY L. , TWEED ERIK J. , LeBRUN JAYMI J.
Published: June 2006

The Hawaiian honeycreepers are thought to be limited primarily to middle- and high-altitude wet forests due to anthropogenic factors at lower altitudes, especially introduced mosquitotransmitted avian malaria. However, recent research has demonstrated that at least one native species, the Hawai'i 'Amakihi (Hemignathus virens virens), is common in areas of active malaria transmission. We examined the current distribution and abundance of native and exotic forest birds within approximately 640 km2 of low-altitude (0–326 m) habitat on south-eastern Hawai'i Island, using roadside variable circular plot (VCP) at 174 stations along eight survey transects. We also re-surveyed 90 stations near sea level that were last surveyed in 1994–1995. Overall, introduced species were more abundant than natives; 11 exotic species made up 87% of the total individuals detected. The most common exotic passerines were Japanese White-eye (Zosterops japonicus), House Finch (Carpodacus mexicanus) and Northern Cardinal (Cardinalis cardinalis). Two native species, Hawai'i 'Amakihi and 'Apapane (Himatione sanguina), comprised 13% of the bird community at low altitudes. Hawai'i 'Amakihi were the most common and widespread native species, being found at 47% of stations at a density of 4.98 birds/ha (95% CI 3.52–7.03). 'Amakihi were significantly associated with 'ohi'a (Metrosideros polymorpha)-dominated forest. 'Apapane were more locally distributed, being found at only 10% of stations. Re-surveys of 1994–1995 transects demonstrated a significant increase in 'Amakihi abundance over the past decade. This work demonstrates a widespread recovery of Hawai'i 'Amakihi at low altitude in southeastern Hawai'i. The changing composition of the forest bird community at low-altitudes in Hawai'i has important implications for the dynamics of avian malaria in low-altitude Hawai'i, and for conservation of Hawai'i's lowland forests.
Taxonomy is important in conservation: a preliminary reassessment of Philippine species-level bird taxonomy
Authors: PETERSON A. TOWNSEND
Published: June 2006

Alpha taxonomy involves delineation of the basic unit of biology: the species. The concepts by which we define species, however, have been controversial, with several alternatives competing at present, some creating fewer and some more species units, depending on interpretation of species limits. Although it is tempting to assume that species concepts would have little interaction with the geographic foci of species richness and endemism — and some have so argued — this assumption does not withstand careful analysis. In this paper, I develop a first-pass assessment of Philippine bird taxonomy under an alternative species concept, and compare the results with the traditional biological species concept lists. Differences between the two lists were dramatic, but not just in numbers of species; rather, new, previously unrecognized or previously underappreciated foci of endemism were noted. A thorough understanding of the taxonomic basis of species lists is therefore critical to conservation planning.
Tectonolithification of sandstone prior to the onset of seismogenic subduction zone: Evidence from tectonic mélange of the Shimanto Belt, Japan
Authors: Hashimoto Y. , Nakaya T. , Ito M. , Kimura G.
Published: June 2006

The deformation and diagenetic processes in sandstone blocks in underthrusted tectonic mélange from the Shimanto Belt, Japan, were analyzed to understand the onset of seismogenesis in subduction zones. The earliest deformation is characterized by “web” cataclasis with grain size reduction in association with ubiquitously developed microshears. A porosity of about 10 ± 3% is estimated for this stage. Subsequently, pore cementation of the sandstone by calcite, quartz, and chlorite occurred, together with pressure solution along the web margin. The porosity suggests a depth of about 3 km below seafloor. Finally, the sandstones were boudinaged, and tension gashes were filled by quartz veins in the neck of the boudins. At this stage, cementation was fully accomplished, and the porosity of the sandstone was reduced to less than a few percent. The final deformation was due to shear parallel to the layering. P‐T conditions for the final necking were about 150–190°C and 150–200 MPa, coinciding with the upper part of the seismogenic zone. Our study on the mélange suggests that relative plate motion is partitioned in time and space in a plate boundary zone.
Sr and87Sr/86Sr in rivers draining the Deccan Traps (India): Implications to weathering, Sr fluxes, and the marine87Sr/86Sr record around K/T
Authors: Das Anirban , Krishnaswami S. , Kumar Anil
Published: June 2006

The concentration of dissolved Sr and its87Sr/86Sr has been measured in the headwaters of the Krishna River System and west flowing Western Ghat rivers, all of which have their drainage almost entirely in the Deccan Traps. The Sr concentration follows that of Ca and Mg with Sr/Ca and Sr/Mg ratios similar to that of Deccan basalts, suggesting that all these alkaline earths are released to waters nearly congruently from the Deccan basalts during chemical weathering. The87Sr/86Sr range from 0.70614 to 0.70986, within that reported for the Deccan basalts. The dissolved Sr flux from the Deccan calculated from the measured data is ∼1.35 × 108moles yr−1, ∼0.4% of the global riverine flux, which is nearly the same as the proportion of area covered by Deccan basalts relative to the global drainage. The flux, however, is a factor of ∼3 lower than that reported for the Narmada‐Tapti‐Wainganga (NTW) rivers draining the northern Deccan. This difference in Sr flux among rivers draining the various regions of Deccan could be natural spatial/temporal variations and/or due to supply of Sr to NTW rivers from nonbasaltic sources. Model calculations on the role of emplacement and weathering of Deccan on marine Sr isotope evolution around KTB and late Tertiary show that Deccan basalts can be an important contributor to the decline in87Sr/86Sr during these periods. It is shown that to account for the pre‐KTB dip in87Sr/86Sr, the flux requirement from Deccan at that time would have to be several times the contemporary flux with87Sr/86Sr of 0.705–0.708. Considering that the area of Deccan at KTB was about thrice the present area and that the weathering rate of Deccan basalts may have been much higher in early stages following eruption, such high fluxes at about KTB seem feasible. The disproportionately higher flux requirement for Sr is similar to that invoked to explain the pre‐KTB decrease in187Os/188Os. The calculations also show that the supply of unradiogenic Sr from basalts can have significant control on the long‐term, ∼66 to ∼55 Ma, decline of marine87Sr/86Sr.
Hydroacoustic events located at the intersection of the Atlantis (30°N) and Kane (23°40′N) Transform Faults with the Mid‐Atlantic Ridge
Authors: Williams Clare M. , Stephen Ralph A. , Smith Deborah K.
Published: June 2006

We investigate the characteristics of T‐phase events located at the ends of two segments of the Mid‐Atlantic Ridge. Our motivations for the study were to understand whether T‐phase locations represent earthquake epicenters (and thus whether accurate geological inferences can be made from their spatial patterns) and to understand further the relationship between T‐phase event characteristics and earthquake properties. We examine the characteristics of 158 T‐phase events with respect to both event location water depth and source to receiver distance. The propagation paths of the T‐phases are also modeled to study the effects of encountering seafloor topography. We find that existing models for T‐phase excitation and propagation cannot explain adequately all of our observations. The amplitudes (Received Levels) of T‐phases at the hydrophones show no dependence on event water depths, in contrast to current excitation models which predict a decrease in event magnitude with increasing water depth. The Received Levels are observed to decrease with increasing source to receiver distance, and events from the two study areas exhibit different trends in relative Received Levels between hydrophones, once attenuation is taken into account. Our acoustic ray trace model is able to reproduce similar trends in relative amplitudes at the hydrophones based on 1‐D topography between the event and each hydrophone, but the variances in both the observed data and model are high. We observe a pattern of short T‐phase onset times for shallow water events and long onset times for deep water events, where onset time is defined as the time interval between the appearance of the T‐phase envelope above the ambient noise and its first peak. This suggests that the onset time may be a function of several variables, including efficiency of energy conversion based on local topography, efficiency of propagation based on event water depth, and hypocentral depth in the crust. The results of this study underscore the complexity of T‐phase excitation and propagation and argue that current models of T‐phase excitation and propagation need to be improved to explain the observed characteristics of T‐phase data.
Application of spheroid models to account for aerosol particle nonsphericity in remote sensing of desert dust
Authors: Dubovik Oleg , Sinyuk Alexander , Lapyonok Tatyana , Holben Brent N. , Mishchenko Michael , Yang Ping , Eck Tom F. , Volten Hester , Muñoz Olga , Veihelmann Ben , van der Zande Wim J. , Leon Jean‐Francois , Sorokin Michael , Slutsker Ilya
Published: June 2006

The possibility of using shape mixtures of randomly oriented spheroids for modeling desert dust aerosol light scattering is discussed. For reducing calculation time, look‐up tables were simulated for quadrature coefficients employed in the numerical integration of spheroid optical properties over size and shape. The calculations were done for 25 bins of the spheroid axis ratio ranging from ∼0.3 (flattened spheroids) to ∼3.0 (elongated spheroids) and for 41 narrow size bins covering the size parameter range from ∼0.012 to ∼625. The look‐up tables were arranged into a software package, which allows fast, accurate, and flexible modeling of scattering by randomly oriented spheroids with different size and shape distributions. In order to evaluate spheroid model and explore the possibility of aerosol shape identification, the software tool has been integrated into inversion algorithms for retrieving detailed aerosol properties from laboratory or remote sensing polarimetric measurements of light scattering. The application of this retrieval technique to laboratory measurements by Volten et al. (2001) has shown that spheroids can closely reproduce mineral dust light scattering matrices. The spheroid model was utilized for retrievals of aerosol properties from atmospheric radiation measured by AERONET ground‐based Sun/sky‐radiometers. It is shown that mixtures of spheroids allow rather accurate fitting of measured spectral and angular dependencies of observed intensity and polarization. Moreover, it is shown that for aerosol mixtures with a significant fraction of coarse‐mode particles (radii ≥ ∼1 μm), the nonsphericity of aerosol particles can be detected as part of AERONET retrievals. The retrieval results indicate that nonspherical particles with aspect ratios ∼1.5 and higher dominate in desert dust plumes, while in the case of background maritime aerosol spherical particles are dominant. Finally, the potential of using AERONET derived spheroid mixtures for modeling the effects of aerosol particle nonsphericity in other remote sensing techniques is discussed. For example, the variability of lidar measurements (extinction to backscattering ratio and signal depolarization ratio) is illustrated and analyzed. Also, some potentially important differences in the sensitivity of angular light scattering to parameters of nonspherical versus spherical aerosols are revealed and discussed.
Improved Reperfusion and Neuroprotection by Creatine in a Mouse Model of Stroke
Authors: Prass Konstantin , Royl Georg , Lindauer Ute , Freyer Dorette , Megow Dirk , Dirnagl Ulrich , Stöckler-Ipsiroglu Gerda , Wallimann Theo , Priller Josef
Published: June 2006

Stroke leads to energy failure and subsequent neuronal cell loss. Creatine and phosphocreatine constitute a cellular energy buffering and transport system, and dietary creatine supplementation was shown to protect neurons in several models of neurodegeneration. Although creatine has recently been found to reduce infarct size after cerebral ischemia in mice, the mechanisms of neuroprotection remained unclear. We provide evidence for augmented cerebral blood flow (CBF) after stroke in creatine-treated mice using a magnetic resonance imaging (MRI)-based technique of CBF measurement (flow-sensitive alternating inversion recovery-MRI). Moreover, improved vasodilatory responses were detected in isolated middle cerebral arteries obtained from creatine-treated animals. After 3 weeks of dietary creatine supplementation, minor changes in brain creatine, phosphocreatine, adenosine triphosphate, adenosine diphosphate and adenosine monophosphate levels were detected, which did not reach statistical significance. However, we found a 40% reduction in infarct volume after transient focal cerebral ischemia. Our data suggest that creatine-mediated neuroprotection can occur independent of changes in the bioenergetic status of brain tissue, but may involve improved cerebrovascular function.
Cortical δ-Opioid Receptors Potentiate K+ Homeostasis During Anoxia and Oxygen–Glucose Deprivation
Authors: Chao Dongman , Donnelly David F , Feng Yin , Bazzy-Asaad Alia , Xia Ying
Published: June 2006

Central neurons are extremely vulnerable to hypoxic/ischemic insult, which is a major cause of neurologic morbidity and mortality as a consequence of neuronal dysfunction and death. Our recent work has shown that δ-opioid receptor (DOR) is neuroprotective against hypoxic and excitotoxic stress, although the underlying mechanisms remain unclear. Because hypoxia/ischemia disrupts ionic homeostasis with an increase in extracellular K+, which plays a role in neuronal death, we asked whether DOR activation preserves K+ homeostasis during hypoxic/ischemic stress. To test this hypothesis, extracellular recordings with K+-sensitive microelectrodes were performed in mouse cortical slices under anoxia or oxygen–glucose deprivation (OGD). The main findings in this study are that (1) DOR activation with [D-Ala2, D-Leu5]-enkephalinamide attenuated the anoxia- and OGD-induced increase in extracellular K+ and decrease in DC potential in cortical slices; (2) DOR inhibition with naltrindole, a DOR antagonist, completely abolished the DOR-mediated prevention of increase in extracellular K+ and decrease in DC potential; (3) inhibition of protein kinase A (PKA) with N-(2-[p-bromocinnamylamino]-ethyl)-5-isoquinolinesulfonamide dihydrochloride had no effect on the DOR protection; and (4) inhibition of protein kinase C (PKC) with chelerythrine chloride reduced the DOR protection, whereas the PKC activator (phorbol 12-myristate 13-acetate) mimicked the effect of DOR activation on K+ homeostasis. These data suggest that activation of DOR protects the cortex against anoxia- or ODG-induced derangement of potassium homeostasis, and this protection occurs via a PKC-dependent and PKA-independent pathway. We conclude that an important aspect of DOR-mediated neuroprotection is its early action against derangement of K+ homeostasis during anoxia or ischemia.
Focusing of laser-generated ion beams by a plasma cylinder: Similarity theory and the thick lens formula
Authors: Gordienko S. , Baeva T. , Pukhov A.
Published: June 2006

It is shown that plasma-based optics can be used to guide and focus highly divergent laser-generated ion beams. A hollow cylinder is considered, which initially contains a hot electron population. Plasma streaming toward the cylinder axis maintains a focusing electrostatic field due to the positive radial pressure gradient. The cylinder works as a thick lens, whose parameters are obtained from similarity theory for freely expanding plasma in cylindrical geometry. Because the lens parameters are energy dependent, the lens focuses a selected energy range of ions and works as a monochromator. Because the focusing is due to the quasineutral part of the expanding plasma, the lens parameters depend on the hot electron temperature Te only, and not their density.
Nonlinear coupling between breathing and quadrupole-like oscillations in the transport of mismatched beams in continuous magnetic focusing fields
Authors: Simeoni W. , Rizzato F. B. , Pakter R.
Published: June 2006

A nonlinear analysis of the transport of breathing beams considering nonaxisymmetric perturbations is performed. It is shown that large-amplitude breathing oscillations of an initially round beam may couple nonlinearly to quadrupole-like oscillations, such that the excess energy initially constrained to the axisymmetric breathing oscillations is allowed to flow back and forth between breathing and quadrupole-like oscillations. In this case, the beam develops an elliptical shape with a possible increase in its size along one direction as the beam is transported. This is a highly nonlinear phenomenon that occurs for large mismatch amplitudes on the order of 100% and is found to be particularly relevant for space-charge-dominated beams with K≳k0ϵ, where K is the beam perveance, k0 is the vacuum phase advance per unit axial length, and ϵ is the emittance of the beam. A simple model based on mapping techniques is used to clarify the mechanism that leads to the energy exchange between the modes and is tested against results from direct integration of the envelope equations.
Low-frequency electron dynamics in the near field of a Hall effect thruster
Authors: Albarède L. , Mazouffre S. , Bouchoule A. , Dudeck M.
Published: June 2006

Time-resolved electrostatic probe measurements were performed in the near field of a SPT100-ML Hall effect thruster in order to investigate electron properties changes on a microsecond time scale. Such measurements allow one to monitor the electron temperature Te, the electron density ne, as well as the plasma potential Vp during a time period that corresponds to one cycle of a breathing-type plasma oscillation with f≈15–30kHz. Although Te(t) stays constant in time, ne(t) and Vp(t) oscillate with the discharge current waveform frequency. The observed time delay between ne and anode discharge current (Ida) waveforms, which is of approximately 7μs, is linked to the ion transit time from the ionization layer to the probed near-field region. The same time gap is measured between Vp(t) and Ida(t), however Vp(t) and ne(t) are in phase opposition. The electron density reaches its highest value at the very moment ions are ejected out of the thruster discharge chamber, which also corresponds to the instant the cathode potential is the most negative. Such a behavior images the need for ion beam neutralization. Further, it is shown that there is a strong correlation between the electron dynamics and the presence of high frequency (HF) plasma oscillations in the megahertz range: HF fluctuations are the strongest when ne is the highest.
Spatial imaging and mechanical control of spin coherence in strained GaAs epilayers
Authors: Knotz H. , Holleitner A. W. , Stephens J. , Myers R. C. , Awschalom D. D.
Published: June 2006

The effect of uniaxial tensile strain on spin coherence in n-type GaAs epilayers is probed using time-resolved Kerr rotation, photoluminescence, and optically detected nuclear magnetic resonance spectroscopies. The band gap, electron spin lifetime, electron g factor, and nuclear quadrupole splitting are simultaneously imaged over millimeter scale areas of the epilayers for continuously varying values of strain. All-optical nuclear magnetic resonance techniques allow access to the strain-induced nuclear quadrupolar resonance splitting in field regimes not easily addressable using conventional optically detected nuclear magnetic resonance.
Low threshold amplified spontaneous emission from near-infrared dye-doped polymeric waveguide
Authors: Yamashita K. , Kuro T. , Oe K. , Yanagi H.
Published: June 2006

We have investigated near-infrared light amplification in a dye-doped polymeric waveguide structure under optical pumping. Amplified spontaneous emission (ASE) at ∼800nm was observed in poly(vinyl-pyrrolidone) thin film with organic dye LDS798. The ASE threshold energy was as low as ∼12μJ∕cm2, which is about one-tenth of previously reported values for infrared-dye-doped polymeric waveguides. This low threshold ASE comes from a large Stokes shift of LDS798, in which the self-absorption of emission is suppressed.
High quality thin GaN templates grown by hydride vapor phase epitaxy on sapphire substrates
Authors: Martin D. , Napierala J. , Ilegems M. , Butté R. , Grandjean N.
Published: June 2006

The growth by hydride vapor phase epitaxy (HVPE) of high quality thin GaN layers (d=8μm) on c-plane sapphire substrates with dislocation densities lower than 2×108cm−2 is demonstrated using a two-step process similar to that of metal organic vapor phase epitaxy (MOVPE). Ex situ surface preparation and nucleation layer thickness are shown to be critical factors in achieving these high quality epilayers as they allow controlling the polarity and the dislocation density, respectively. Furthermore, we demonstrate that in situ reflectivity monitoring applied to HVPE is a powerful technique for rapidly optimizing the growth parameters. As a result, thin HVPE-grown GaN layers with state of the art MOVPE GaN quality are obtained as demonstrated through structural and optical characterizations.
Direct measurement of spatial distortions of charge density waves in K0.3MoO3
Authors: Du Chao-hung , Lee Yen-Ru , Lo Chung-Yu , Lin Hsiu-Hau , Chang Shih-Lin , Tang Mau-Tsu , Stetsko Yuri P. , Lee Jey-Jau
Published: June 2006

Using x-ray scattering and multiple diffraction on a charge density wave (CDW) material, K0.3MoO3, under applied voltages, we demonstrate that the occurrence of nonlinear conductivity caused by the periodic media is through the internal deformation of the CDW lattice, i.e., a phase jump of 2π, as the applied voltage exceeds the threshold. From the evolution of the measured peak width of satellite reflections as a function of the field strength, we also report that the CDW lattice can be driven to move and undergo a dynamic phase transition from the disordered pinning state to ordered moving solid state and then to disordered moving liquid.
AlN thin film as waveguide for shear acoustic waves
Authors: Martin F. , Muralt P.
Published: June 2006

A set of shear acoustic waves in the 78–195MHz range composed of a surface skimming bulk wave and highly resolved shear acoustic plate modes has been simultaneously excited in a thin ST-cut quartz plate by means of transducers with a 1μm thick sputtered AlN thin film used as a waveguiding layer. The effect of coating the transducers face with AlN is shown to increase the propagation speed of the first 13 plate modes in the ST-cut quartz, but then to decreases the propagation speed of plate modes higher than the 14th.
Effects of a freshwater canal discharge on an ovoviviparous isopod inhabiting an exposed sandy beach
Authors: Lozoya Juan Pablo , Defeo Omar
Published: June 2006

The present study evaluates the effects of an artificial freshwater discharge (Canal Andreoni) on the ecology of the ovoviviparous isopod Excirolana armata. Bimonthly, 17 environmental variables plus isopod abundance, biomass, fecundity, growth and mortality were compared between three sites: ‘Barra del Chuy’ (undisturbed), at 13 km from the canal, ‘Coronilla’ (moderately disturbed), at 1 km, and ‘Andreoni’ (grossly disturbed), at the canal mouth. Environmental (salinity, slope, beach width, and swash width) and some biological (isopod abundance, biomass and growth rates) variables significantly decreased towards Canal Andreoni. Salinity was the most important explanatory variable of spatial trends in isopod biomass. However, the reproductive output, fecundity, survival and individual weight were not affected, suggesting that E. armata is regulated by density-dependent and abiotic factors operating together: the former were more intense on undisturbed conditions, whereas the latter prevailed in impacted ones. Internal brooding counteracts the effect of fresh water, which explains the lack of effect of environmental harshness on reproductive traits.
Macroinvertebrate communities in willow (Salix spp.) and reed beds (Phragmites australis) in central Victorian streams in Australia
Authors: Jayawardana J. M. C. K. , Westbrooke Martin , Wilson Michael , Hurst Cameron
Published: June 2006

Exotic willows (Salix spp.) are widespread riparian tree species of rivers in temperate Australia and New Zealand. Despite being considered as a weed of national significance, little is known about the habitat value of willows and the impact on aquatic biota of vegetation change following willow management programmes. Macroinvertebrate fauna in root habitats of willows and Phragmites australis habitats were examined in three central Victorian rivers to understand the effect of such littoral habitat changes on macroinvertebrates. Data were analysed using Partially Nested Factorial ANOVA with season, river and habitat as main effects. Habitat structure had a significant effect (P < 0.05) on macroinvertebrate community assemblage. However, effect of habitat was not consistent among seasons. The greatest community differences among habitats were observed during winter and least separation during autumn. Taxa responsible for community differences among habitats were also identified. Species richness and abundance did not show consistent variation among habitats over different rivers or seasons. This study provided some indication of the macroinvertebrate community changes that would take place in situations where riparian vegetation changes takes place from willows to P. australis.
Ontogenetic shifts in the distribution and reproductive patterns of Australian anchovy (Engraulis australis) determined by otolith microstructure analysis
Authors: Dimmlich W. F. , Ward T. M.
Published: June 2006

Upwelling systems can provide ideal conditions for survival and growth of larval fishes. However, these unstable environments are highly dispersive and mortalities can be high. Anchovies (Engraulis spp.) utilise a range of behavioural strategies to increase egg and larval survival. Ontogenetic shifts in distribution have been proposed for Australian anchovy (Engraulis australis), but no supporting otolith-based age studies have been published to date. The present study used otolith increment counts to age larval, juvenile and adult Australian anchovy, which spawn throughout South Australian gulf and shelf waters. Only fish up to 1 year of age occurred in the northern Spencer Gulf, where eggs and larvae in high densities are retained in a nursery area favourable to anchovies. The southern gulf area was inhabited by 1, 2 and 3 year olds. Older anchovy were found in offshore shelf waters, where upwelling occurs and larval survivorship may be high. We hypothesise that Australian anchovy move offshore with age to utilise the wide range of environments that provide suitable spawning and nursery areas for this species.
Upgrading antibiotic use within a class: Tradeoff between resistance and treatment success
Authors: Wang Y. Claire , Lipsitch Marc
Published: June 2006

Increasing resistance to antibiotics creates the need for prudent antibiotic use. When resistance to various antibiotics within a class is driven by stepwise accumulation of mutations, a dilemma may exist in regard to replacing an antibiotic that is losing effectiveness due to resistance with a new drug within the same class. Such replacement may enhance treatment success in the short term but promote the spread of highly resistant strains. We used mathematical models to quantify the tradeoff between minimizing treatment failures (by switching early) and minimizing the proliferation of the highly resistant strain (by delaying the switch). Numerical simulations were applied to investigate the cumulative prevalence of the highly resistant strain (Resistance) and the cumulative number of treatment failures (Failure) that resulted from following different antibiotic use policies. Whereas never switching to the new drug always minimizesResistanceand maximizesFailure, immediate switching usually maximizesResistanceand minimizesFailure. Thus, in most circumstances, there is a strict tradeoff in which early use of the new drug enhances treatment effectiveness while hastening the rise of high-level resistance. This tradeoff is most acute when acquired resistance is rare and the highly resistant strain is readily transmissible. However, exceptions occur when use of the new drug frequently leads to acquired resistance and when the highly resistant strain has substantial “fitness cost”; these circumstances tend to favor an immediate switch. We discuss the implications of these considerations in regard to antibiotic choices forStreptococcus pneumoniae.
Properties of mouse connexin 30.2 and human connexin 31.9 hemichannels: Implications for atrioventricular conduction in the heart
Authors: Bukauskas Feliksas F. , Kreuzberg Maria M. , Rackauskas Mindaugas , Bukauskiene Angele , Bennett Michael V. L. , Verselis Vytas K. , Willecke Klaus
Published: June 2006

Four connexins (Cxs), mouse (m)Cx30.2, Cx40, Cx43, and Cx45, determine cell–cell electrical signaling in mouse heart, and Cx43 and Cx45 are known to form unapposed hemichannels. Here we show that mCx30.2, which is most abundantly expressed in sinoatrial and atrioventricular nodal regions of the heart, and its putative human ortholog, human (h)Cx31.9, also form functional hemichannels, which, like mCx30.2 cell–cell channels, are permeable to cationic dyes up to ≈400 Da in size. DAPI uptake by HeLa cells expressing mCx30.2 was >10-fold faster than that by HeLa parental cells. In Ca
2+
-free medium, uptake of DAPI by HeLaCx30.2-EGFP cells was increased ≈2-fold, but uptake by parental cells was not affected. Conversely, acidification by application of CO
2
reduced DAPI uptake by HeLaCx30.2-EGFP cells but had little effect on uptake by parental cells. Cells expressing mCx30.2 exhibited higher rates of DAPI uptake than did cells expressing any of the other cardiac Cxs. Cardiomyocytes of 2-day-old rats transfected with hCx31.9-EGFP took up DAPI and ethidium bromide 5–10 times faster than wild-type cardiomyocytes. Mefloquine, a close derivative of quinine and quinidine that exhibits antimalarial and antiarrhythmic properties, reduced conductance of cell–cell junctions and dye uptake through mCx30.2 hemichannels with approximately the same affinity (IC
50
= ≈10 μM) and increased dependence of junctional conductance on transjunctional voltage. Unitary conductance of mCx30.2 hemichannels was ≈20 pS, about twice the cell–cell channel conductance. Hemichannels formed of mCx30.2 and hCx31.9 may slow propagation of excitation in the sinoatrial and atrioventricular nodes by shortening the space constant and depolarizing the excitable membrane.
Seaweed resources in Malaysia: Current status and future prospects
Authors: Phang S. M.
Published: June 2006

Malaysia has an extensive coastline fringed by numerous islands, providing various habitats for the proliferation of seaweeds. The first checklist of the marine benthic algae in Malaysia was published in 1991, together with a historical account of phycological research in the region. Regular collections of seaweeds resulted in several updates reporting new records and new species. The tally of Malaysian marine algae stands at 375 specific and infraspecific taxa.

The last two decades have seen an increased interest in the commercial use of seaweeds, especially Eucheuma, Kappaphycus and Gracilaria. Eucheuma and Kappaphycus are cultured in Sabah where two factories for production of semi-refined carrageenan have been established. The inventory of Malaysian seaweeds continues. Ecological information is scarce and therefore biomass assessments of natural seaweed areas, productivity determination and phenological studies of important species should be encouraged. Only then can the status of the seaweed flora of Malaysia be assessed, and threatened species and habitats be identified.
Sustainable utilization and management of Mangrove ecosystems of Malaysia
Authors: Chong V. C.
Published: June 2006

Mangrove ecosystems of Malaysia are found largely on the west coast of Peninsular Malaysia, the southern coast of Sarawak and the eastern coast of Sabah. Malaysian mangroves are largely of the river-dominated type built on large deltaic plains, but intergrades of river-dominated and tide-dominated settings, drowned valley settings and carbonate settings are also found. Mangrove resources are exploited by humans for coastal protection, forestry products, fisheries, wildlife, agriculture, aquaculture, settlement, urban and industrial development, and ecotourism. Very often this exploitation is unsustainable, particularly when mangroves are converted for agriculture, aquaculture, urban, and industrial development. The overall loss in mangrove area due to these reasons is about 111,046 hectares or 16 percent, from 1973–2000. In spite of an exemplary management plan implemented for the Matang mangrove forest reserve, mangrove forests in the various states are unequally managed because there are conflicting interests due to management policies that are largely sectoral in nature. While sustainable management policies and guidelines are in place, it is still crucial how the State governments, which have power over land matters, implement Federal policies regarding mangrove conservation.
Marine capture fisheries
Authors: Gopinath N. , Puvanesuri S. S.
Published: June 2006

Marine capture fisheries constitute an important sector in the Malaysian economy; not only as a major food source but also as a generator of foreign exchange and employment. Rapid economic growth in recent years has resulted in a significant movement of rural manpower to industrial and urban centres, leaving a declining and aging population of fishers in the industry, particularly where the coastal fisheries are concerned. On the other hand, the offshore fishery is still relatively small though substantial Governmental efforts are being invested in pushing for a “blue water” fisheries fleet. The major problems in the growth of the offshore fishery relate not only to basic issues such as infrastructure, capital and skills, but also to the need to compete with advanced fishing nations such as Thailand, Philippines and Indonesia.

This report attempts to provide a broad overview of the fishing industry in Malaysia, particularly in relation to the health of the resources on which it is dependent. It also points out the constraints and contradictions in present resource management regimes and attempts to indicate a way forward in resolving some of them.
Coastal erosion and reclamation in Malaysia
Authors: Ghazali Nor Hisham M.
Published: June 2006

Reclamation, a human activity that can transform an entire environment in a relatively short time, epitomizes one of the pinnacles of engineering achievement—creation of new landmass. As demonstrated by the construction of the Chek Lap Kok and Kansai airports in Hong Kong and Japan respectively, whole new islands can be created in this way and, in the process, landscapes, eco-systems and livelihoods could be altered. Considering the potential and major implications, reclamation projects call for a comprehensive assessment of environmental impacts ranging from the direct to the residual, and from the quantifiable to the intangible. Reclamation works have been carried out along Malaysia's coast since the 1950s but it was only in the 1990s that it has captured much public attention, and mostly, due to the conceptual proposals of several large scale reclamation plans along the coast of Peninsular Malaysia facing the Straits of Malacca.

This chapter describes the history of erosion control and reclamation works in Malaysia and discusses the initiatives carried out to address the problems they pose.
Functional distribution of 𝐿(𝑠,𝜒_{𝑑}) with real characters and denseness of quadratic class numbers
Authors: Mishou Hidehiko , Nagoshi Hirofumi
Published: June 2006

We investigate the functional distribution of

L
L

-functions

L
(
s
,

χ
d

)

L(s, \chi _d)

with real primitive characters

χ
d

\chi _d

on the region

1

/

2
>
Re
⁡
s
>
1

1/2 > \operatorname {Re} s >1

as

d
d

varies over fundamental discriminants. Actually we establish the so-called universality theorem for

L
(
s
,

χ
d

)

L(s, \chi _d)

in the

d
d

-aspect. From this theorem we can, of course, deduce some results concerning the value distribution and the non-vanishing. As another corollary, it follows that for any fixed

a
,
b

a, b

with

1

/

2
>
a
>
b
>
1

1/2> a> b>1

and positive integers

r
′

,
m

r’, m

, there exist infinitely many

d
d

such that for every

r
=
1
,
2
,
⋯
,

r
′

r=1, 2, \cdots , r’

the

r
r

-th derivative

L

(
r
)

(
s
,

χ
d

)

L^{(r)} (s, \chi _d)

has at least

m
m

zeros on the interval

[
a
,
b
]

[a, b]

in the real axis. We also study the value distribution of

L
(
s
,

χ
d

)

L(s, \chi _d)

for fixed

s
s

with

Re
⁡
s
=
1

\operatorname {Re} s =1

and variable

d
d

, and obtain the denseness result concerning class numbers of quadratic fields.
Martingales and character ratios
Authors: Fulman Jason
Published: June 2006

Some general connections between martingales and character ratios of finite groups are developed. As an application we sharpen the convergence rate in a central limit theorem for the character ratio of a random representation of the symmetric group on transpositions. A generalization of these results is given for Jack measure on partitions. We also give a probabilistic proof of a result of Burnside and Brauer on the decomposition of tensor products.