bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced view of the “tropical Atlantic ozone paradox” and “zonal wave one” from the in situ MOZAIC and SHADOZ data
Authors: Sauvage B. , Thouret V. , Thompson A. M. , Witte J. C. , Cammas J.‐P. , Nédélec P. , Athier G.
Published: January 2006

Ozone vertical profiles from the Measurements of Ozone from Airbus In‐service Aircraft (MOZAIC) program over Africa are used to complement pictures of the wave‐one pattern and the “tropical Atlantic paradox” identified through soundings in the Southern Hemisphere Additional Ozonesondes (SHADOZ) network. The Atlantic paradox refers to a greater tropospheric ozone column amount over the South Atlantic than the North Atlantic during the West African biomass burning season. SHADOZ and MOZAIC data from 1998–2002 and 1997–2004, respectively, are used to show that these two phenomena are linked. The combined data are used to address the following: Does the (continental) MOZAIC data modify the appearance of the paradox? Do lower tropospheric MOZAIC data lead to new conclusions about ozone in the wave‐one maximum region? During December, January, and February (DJF), the lower troposphere over Africa exhibits a higher ozone signal in the burning hemisphere, that is, north of the equator, so the “paradox” does not appear over the African continent. The MOZAIC data set over Africa highlights another component of the wave‐one feature when the tropospheric ozone mixing ratio is viewed in zonal cross section. The lower troposphere makes a nonnegligible contribution to the regionally higher ozone column during the biomass burning periods of each hemisphere (DJF) for West Africa and June, July, and August (JJA) for the central Africa region. A southern preference for the wave‐one character, previously deduced from satellite data, is confirmed with a stronger maximum in September, October, and November (SON). Both the paradox and wave‐one phenomena are consistent with a view that the African continent is a major source of biomass burning and lightning emissions.
Space Weather and Alexander von Humboldt's Kosmos
Authors: Schlegel Kristian
Published: January 2006

German scientist Alexander von Humboldt (1769–1859) did not know or use the modern term “space weather.” Nevertheless, several corresponding phenomena, such as the Sun and sunspots, geomagnetism, and aurorae, are extensively discussed in his famous work Kosmos, a set of five volumes published between 1845 and 1962. Humboldt, who studied at universities in Frankfurt/Oder, Göttingen, Hamburg, Freiburg, and Jena, was already an acknowledged scholar when he wrote Kosmos, and kept close and lively contact with the most influential scientists of his time. Therefore his work is a thorough review of the knowledge at the middle of the nineteenth century.
P2X7Receptor Modulation on Microglial Cells and Reduction of Brain Infarct Caused by Middle Cerebral Artery Occlusion in Rat
Authors: Melani Alessia , Amadio Susanna , Gianfriddo Marco , Vannucchi Maria G , Volontè Cinzia , Bernardi Giorgio , Pedata Felicita , Sancesario Giuseppe
Published: January 2006

Adenosine 5′-triphosphate outflow increases after an ischemic insult in the brain and may induce the expression of P2X7receptors in resting microglia, determining its modification into an activated state. To assess the effects of P2X7receptor blockade in preventing microglia activation and ameliorating brain damage and neurological impairment, we delivered the P2 unselective antagonist Reactive Blue 2 to rats after middle cerebral artery occlusion. In sham-operated animals, devoid of brain damage, double immunofluorescence verified the absence of P2X7immunoreactivity on resting microglia, astrocytes, and neurons, identified, respectively, by OX-42, glial fibrillary acid protein, and neuronal nuclei (NeuN) immunoreactivity. After ischemia, vehicle-treated rats showed monolateral sensorimotor deficit and tissue damage in striatum and frontoparietal cortex. Moreover, P2X7immunoreactivity was de novo expressed on activated microglia in infarcted and surrounding areas, as well as on a reactive form of microglia, resting in shape but P2X7immunoreactive, present in ipsi- and contralateral cingulate and medial frontal cortex. Reactive Blue 2 improved sensorimotor deficit and restricted the volume of infarction, without preventing the expression of P2X7, but inducing it in the microglia of contralateral frontal and parietal cortex and striatum, which had lost reciprocal connections with the remote infarct area. De novo expression of P2X7occurred in both activated and reactive microglia, suggesting their differentiated roles in the area of infarct and in remote regions. Reactive Blue 2 reduced ischemic brain damage, likely blocking the function of activated microglia in the infarct area, but in the remote brain regions promoted the expression of P2X7on reactive microglia, developing defense and reparative processes.
Increases in Oxygen Consumption without Cerebral Blood Volume Change during Visual Stimulation under Hypotension Condition
Authors: Nagaoka Tsukasa , Zhao Fuqiang , Wang Ping , Harel Noam , Kennan Richard P , Ogawa Seiji , Kim Seong-Gi
Published: January 2006

The magnitude of the blood oxygenation level-dependent (BOLD) signal depends on cerebral blood flow (CBF), cerebral blood volume (CBV) and cerebral metabolic rate of oxygen (CMRO2). Thus, it is difficult to separate CMRO2 changes from CBF and CBV changes. To detect the BOLD signal changes induced only by CMRO2 responses without significant evoked CBF and CBV changes, BOLD and CBV functional magnetic resonance imaging (fMRI) responses to visual stimulation were measured under normal and hypotension conditions in isoflurane-anesthetized cats at 4.7T. When the mean arterial blood pressure (MABP) decreased from 89±10 to 50±1 mm Hg (mean±standard deviation, n = 5) by infusion of vasodilator sodium nitroprusside, baseline CBV in the visual cortex increased by 28.4%±8.3%. The neural activity-evoked CBV increase in the visual cortex was 10.8%±3.9% at normal MABP, but was negligible at hypotension. Positive BOLD changes of +1.8%±0.5% (gradient echo time = 25 ms) at normal MABP condition became prolonged negative changes of 1.2%±0.3% at hypotension. The negative BOLD response at hypotension starts approximately 1 sec earlier than positive BOLD response, but similar to CBV change at normal MABP condition. Our finding shows that the negative BOLD signals in an absence of CBV changes are indicative of an increase in CMRO2. The vasodilator-induced hypotension model simplifies the physiological source of the BOLD fMRI signals, providing an insight into spatial and temporal CMRO2 changes.
Gauging Recovery after Hemorrhagic Stroke in Rats: Implications for Cytoprotection Studies
Authors: MacLellan Crystal L , Auriat Angela M , McGie Steven C , Yan Reginia HY , Huynh Hang D , De Butte Maxine F , Colbourne Frederick
Published: January 2006

Successful clinical translation of prospective cytoprotectants will likely occur only with treatments that improve functional recovery in preclinical (rodent) studies. Despite this assumption, many rely solely on histopathologic end points or the use of one or two simple behavioral tests. Presently, we used a battery of tests to gauge recovery after a unilateral intracerebral hemorrhagic stroke (ICH) targeting the striatum. In total, 60 rats (N = 15 per group) were stereotaxically infused with 0 (SHAM), 0.06 (MILD lesion), 0.12 (MODERATE lesion), or 0.18 U (SEVERE lesion) of bacterial collagenase. This created a range of injury akin to moderate (from SEVERE to MODERATE or MODERATE to MILD lesion size ∼30% reduction) and substantial cytoprotection (SEVERE to MILD lesion size—51% reduction). Post-ICH functional testing occurred over 30 days. Tests included the horizontal ladder and elevated beam tests, swimming, limb-use asymmetry (cylinder) test, a Neurologic Deficit Scale, an adhesive tape removal test of sensory neglect, and the staircase and single pellet tests of skilled reaching. Most tests detected significant impairments (versus SHAM), but only a few (e.g., staircase) frequently distinguished among ICH groups and none consistently differentiated among all ICH groups. However, by using a battery of tests we could behaviorally distinguish groups. Thus, preclinical testing would benefit from using a battery of behavioral tests as anything less may miss treatment effects. Such testing must be based on factors including the type of lesion, the postoperative delay and the time required to complete testing.
A Metabolomic Approach to Ionotropic Glutamate Receptor Subtype Function: A Nuclear Magnetic Resonancein vitroInvestigation
Authors: Rae Caroline , Moussa Charbel El-Hajj , Griffin Julian L , Parekh Sapan B , Bubb William A , Hunt Nicholas H , Balcar Vladimir J
Published: January 2006

A range of behaviours are elucidated via ionotropic glutamate receptors (iGluR). In this work, we examined the acute activation of iGluRs by a range of receptor ligands and effectors to see whether distinguishable metabolic sequelae were elucidated by the activity. We used a guinea-pig brain cortical tissue slice model using targeted receptor ligands ((RS)-(tetrazol-5-yl)glycine (TZG), (5S,10R)-(+)-5-methyl-10, 11-dihydro-5H-dibenzo[ a, d]cyclohepten-5, 10-imine maleate (MK-801, dizocilpine), cis-4-[phosphomethyl]-piperidine-2-carboxylic acid (CGS 19755), (RS)-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, (2S, 3S, 4S)-2-carboxy-4-(1-methylethenyl)-3-pyrrolidineacetic acid (kainate) and D-serine (D-Ser), as well as compounds (quinolinic acid and kynurenic acid (KynA)) involved in some neuroinflammatory responses. The data were derived using13C and1H NMR spectroscopy, and analysed by metabolomic approaches and multivariate statistics. The metabolic effects of agonists at the three major classes of iGluR were easily separated from each other using this method. The classical N-methyl-D-aspartate receptor agonist TZG and the antagonist CGS 19755 produced excitatory and inhibitory metabolic responses, respectively, while the blocker MK-801 resulted in a significant decrease in net metabolism and produced the largest decrease in all metabolite pool sizes seen by any glutamatergic ligand we have studied. Quinolinic acid and KynA produced similar acute metabolic responses, which were unlike those to TZG or CGS 19755, but similar to that of D-Ser. D-Ser was highly stimulatory of net flux into the Krebs cycle. These data show that the metabolic response to iGluR perturbation in vitro is a sensitive discriminator of function.
Traumatic Brain Injury in Mice Deficient in Bid: Effects on Histopathology and Functional Outcome
Authors: Bermpohl Daniela , You Zerong , Korsmeyer Stanley J , Moskowitz Michael A , Whalen Michael J
Published: January 2006

Bid is a proapoptotic member of the Bcl-2 family that mediates cell death by caspase-dependent and-independent pathways. We tested mice genetically deficient in Bid in a controlled cortical impact (CCI) model to examine the hypothesis that Bid contributes to cell death and functional outcome after traumatic brain injury. After CCI, truncated Bid (15 kDa) was robustly detected in cortical brain homogenates of wild-type mice. Bid –/– mice had decreased numbers of cortical cells with acute plasmalemma injury at 6 h (wild type (WT), 1721 ± 124; Bid –/–, 1173 ± 129 cells/ × 200 field; P < 0.01), decreased numbers of cells expressing cleaved caspase-3 in the dentate gyrus at 48 h (WT, 113 ± 15; Bid–/–, 65 ± 9 cells/ × 200 field; P < 0.05), and reduced lesion volume at 12 days (Bid –/–, 5.9 ± 0.4 mm3; WT, 8.4±0.4 mm3; P < 0.001), but did not differ from WT mice at later times after injury regarding lesion size (30 days) or brain tissue atrophy (40 days). Compared with naïve mice, injured mice in both groups performed significantly worse on motor and Morris water maze (MWM) tests; however, mice deficient in Bid did not differ from WT in postinjury motor and MWM performance. The data show that Bid deficiency decreases early posttraumatic brain cell death and tissue damage, but does not reduce functional outcome deficits after CCI in mice.
Biphasic Role of Nuclear Factor-kB on Cell Survival and COX-2 Expression in SOD1 Tg Astrocytes after Oxygen Glucose Deprivation
Authors: Lee Yong-Sun , Song Yun Seon , Giffard Rona G , Chan Pak H
Published: January 2006

In cytoplasm, nuclear factor-k(NF-kB) is associated with the inhibitory protein, IkBα. On activation by H2O2, IkBα is phosphorylated and degraded, exposing the nuclear localization signals on the NF-kB heterodimer. Cyclooxygenase-2 (COX-2), which mediates prostaglandin synthesis during inflammation, is induced by oxidative stress mediated by NF-kB. We investigated whether the NF-kB signaling pathway affected cell death and COX-2 expression after hypoxia-induced oxidative stress in wild-type (WT) and copper/zinc-superoxide dismutase transgenic (SOD1 Tg) astrocytes. In WT astrocytes, phospho-IkBα was highly expressed after oxygen-glucose deprivation (OGD) and 2 h of reperfusion, concomitant with the decrease in kBa. The NF-kB p50 level increased similarly in WT and SOD1 Tg astrocytes (1.2-/1.4-fold) after OGD. Electrophoretic mobility shift assay showed higher DNA-binding activity of NF-kB p50 in WT than in SOD1 Tg astrocytes 6 h after 4 h of OGD. The COX-2 level was induced by 2.7- and 1.3-fold after OGD in WT and SOD1 Tg astrocytes, and an antioxidant protected both groups against OGD injury. Superoxide dismutase transgenic cells were 23% more protective against OGD injury than WTs when assessed by lactate dehydrogenase release. However, transfection of NF-kB small interfering RNAs in SOD1 Tg astrocytes aggravated cell death and increased COX-2 expression. These results suggest that the NF-kB signaling pathway induced COX-2 expression and promoted cell death in WTs after OGD injury; however, NF-kB activation protected cells and decreased COX-2 expression in SOD1 Tg astrocytes. This biphasic role of NF-kB might be coordinately regulated by reactive oxygen species levels in astrocytes, thereby functioning as a regulator of cell death/survival.
Resveratrol Mimics Ischemic Preconditioning in the Brain
Authors: Raval Ami P , Dave Kunjan R , Perez-Pinzon Miguel A
Published: January 2006

Recent studies in a variety of species including mammals showed that resveratrol ( trans-3, 5, 4″-trihydroxystibene) treatment and caloric restriction increased silent information regulator 2/sirtuin 1 activity, which mediated increase in life span/cell survival. Resveratrol is a naturally occurring phytoalexin and a well-documented cardioprotective agent. Similarly, ischemic preconditioning (IPC) has been shown to be both cardio- and cerebroprotective against subsequent ischemic insults. A major emphasis in this field is to understand the molecular mechanisms that mediate this phenomenon. The goal of this study was to define whether resveratrol can emulate IPC neuroprotection against cerebral ischemia. Employing an in vitro model of cerebral ischemia, the organotypic hippocampal slice culture, we report that resveratrol pretreatment mimics IPC via the SIRT1 pathway. Blockade of SIRT1 activation by sirtinol after IPC or resveratrol pretreatment abolished their neuroprotection. A better understanding of the mechanisms by which resveratrol induces ischemic tolerance in a prophylactic manner may provide a novel therapy against stroke or neurosurgical procedures.
Gene Expression in Blood Changes Rapidly in Neutrophils and Monocytes after Ischemic Stroke in Humans: A Microarray Study
Authors: Tang Yang , Xu Huichun , Du Xin Li , Lit Lisa , Walker Wynn , Lu Aigang , Ran Ruiqiong , Gregg Jeffrey P , Reilly Melinda , Pancioli Art , Khoury Jane C , Sauerbeck Laura R , Carrozzella Janice A , Spilker Judith , Clark Joseph , Wagner Kenneth R , Jauch Edward C , Chang Dongwoo J , Verro Piero , Broderick Joseph P , Sharp Frank R
Published: January 2006

Ischemic brain and peripheral white blood cells release cytokines, chemokines and other molecules that activate the peripheral white blood cells after stroke. To assess gene expression in these peripheral white blood cells, whole blood was examined using oligonucleotide microarrays in 15 patients at 2.4 ± 0.5, 5 and 24 h after onset of ischemic stroke and compared with control blood samples. The 2.4 h blood samples were drawn before patients were treated either with tissue-type plasminogen activator (tPA) alone or with tPA plus Eptifibatide (the Combination approach to Lysis utilizing Eptifibatide And Recombinant tPA trial). Most genes induced in whole blood at 2 to 3 h were also induced at 5 and 24 h. Separate studies showed that the genes induced at 2 to 24 h after stroke were expressed mainly by polymorphonuclear leukocytes and to a lesser degree by monocytes. These genes included: matrix metalloproteinase 9; S100 calcium-binding proteins P, A12 and A9; coagulation factor V; arginase I; carbonic anhydrase IV; lymphocyte antigen 96 (cluster of differentiation (CD)96); monocarboxylic acid transporter (6); ets-2 (erythroblastosis virus E26 oncogene homolog 2); homeobox gene Hox 1.11; cytoskeleton-associated protein 4; N-formylpeptide receptor; ribonuclease-2; N-acetylneuraminate pyruvate lyase; BCL6; glycogen phosphorylase. The fold change of these genes varied from 1.6 to 6.8 and these 18 genes correctly classified 10/15 patients at 2.4 h, 13/15 patients at 5h and 15/15 patients at 24 h after stroke. These data provide insights into the inflammatory responses after stroke in humans, and should be helpful in diagnosis, understanding etiology and pathogenesis, and guiding acute treatment and development of new treatments for stroke.
Nonlinear Analysis of Blood Cell Flux Fluctuations in the Rat Brain Cortex during Stepwise Hypotension Challenge
Authors: Herman Peter , Eke Andras
Published: January 2006

Blood flow through a region of interest in the brain cortex (cerebral blood flow (CBF)) as measured by laser-Doppler flowmetry (LDF) shows a complex temporal pattern, which can be either merely random or a manifestation of segmental chaotic dynamics of vasomotion-induced flowmotion in the arterial tree, a deterministic phenomenon; or that of a fractal, self-similar correlation order that emerges from the set of segmental perfusion events on statistical ground. Fractal content (F%) was determined by coarse-graining spectral analysis and their self-similar exponent, H, estimated by bridge-detrended Scaled Windowed Variance (bdSWV) method and a variant of the power Spectral Density method (lowPSDw,e). Chaotic dynamics were assessed by computing the correlation dimension (Dcorr) and the largest Lyapunov exponent (Λmax) on unfiltered raw and surrogate datasets. In 10 Sprague–Dawley rats anesthetized by halothane, CBF was measured through the thinned calvarium by the LDF method. Blood pressure (BP) was reduced from 100 to 40 mm Hg in steps of 20 mm Hg maintained for 2 mins by the lower body negative pressure method. Fractal and chaotic patterns coexisted in tissue perfusion. CBF did not show autoregulation. At every BP step, F% remained high (72% to 88%) and was independent of BP. Laser-Doppler flowmetry signals proved to be nonstationary fractional Brownian motions. Their Hs by bdSWV and lowPSDw,e (0.29 ± 0.006 and 0.25 ± 0.012, respectively) were independent of BP. Neither Dcorr nor Λmax varied with hypotension. Their values were characteristic of a chaotic system, but surrogate data analysis rendered some of them inconclusive. Hence, CBF fluctuations can be regarded as a robust phenomenon that is not abolished even by sustained hypotension at 40 mm Hg.
Brain Protection at the Blood–Cerebrospinal Fluid Interface Involves a Glutathione-Dependent Metabolic Barrier Mechanism
Authors: Ghersi-Egea Jean-François , Strazielle Nathalie , Murat Audrey , Jouvet Anne , Buénerd Annie , Belin Marie-Françoise
Published: January 2006

The choroid plexuses (CPs) form a protective interface between the blood and the ventricular cerebrospinal fluid (CSF). To probe into the pathways by which CPs provide brain protection, we sought to evaluate the efficiency of glutathione conjugation in this barrier as a mechanism to prevent the entry of blood-borne electrophilic, potentially toxic compounds into the CSF, and we investigated the fate of the resulting metabolites. Rat CPs, as well as human CPs from both fetal and adult brains, displayed high glutathione-S-transferase activities. Using an in vitro model of the blood-CSF barrier consisting of choroidal epithelial cells cultured in a two-chambered device, we showed that glutathione conjugation can efficiently prevent the entry of 1-chloro-2,4-dinitrobenzene (CDNB) into the CSF, a model for electrophilic compounds. The duration of this enzymatic protection was set by the concentration of CDNB to which the epithelium was exposed, and this barrier effect was impaired only on severe epithelial intracellular glutathione and cysteine depletion. The conjugate was excreted from the choroidal cells in a polarized manner, mostly at the blood-facing membrane, via a high-capacity transport process, which is not a rate-limiting step in this detoxification pathway, and which may involve transporters of the ATP-binding cassette c(Abcc) and/or solute carrier 21 (Slc21) families. Supplying the choroidal epithelium at the blood-facing membrane with a therapeutically relevant concentration of N-acetylcysteine sustained this neuroprotective effect. Thus, glutathione conjugation at the CP epithelium coupled with the basolateral efflux of the resulting metabolites form an efficient blood-CSF enzymatic barrier, which can be enhanced by pharmacologically increasing glutathione synthesis within the epithelial cells.
Dose–Response Effect of Tetracyclines on Cerebral Matrix Metalloproteinase-9 after Vascular Endothelial Growth Factor Hyperstimulation
Authors: Lee Chanhung Z , Yao Jianhua S , Huang Yong , Zhai Wenwu , Liu Weizhong , Guglielmo B Joseph , Lin Emil , Yang Guo-Yuan , Young William L
Published: January 2006

Brain arteriovenous malformations (BAVMs) are a potentially life-threatening disorder. Matrix metalloproteinase (MMP)-9 activity was greatly increased in BAVM tissue specimens. Doxycycline was shown to decrease cerebral MMP-9 activities and angiogenesis induced by vascular endothelial growth factor (VEGF). In the present study, we determined the dose-response effects of doxycycline and minocycline on cerebral MMP-9 using our mouse model with VEGF focal hyperstimulation delivered with adenoviral vector (AdVEGF) in the brain. Mice were treated with doxycycline or minocycline, respectively, at 1, 5, 10, 30, 50, or 100 mg/kg/day through drinking water for 1 week. Our results have shown that MMP-9 messenger ribonucleic acid (mRNA) expression was inhibited by doxycycline starting at 10 mg/kg/day ( P < 0.02). Minocycline showed more potent inhibition on MMP-9 mRNA expression, starting at 1 ( P < 0.005) and further at more than 30 ( P < 0.001) mg/kg/day. At the enzymatic activity level, doxycycline started to suppress MMP-9 activity at 5 mg/kg/day ( P < 0.001), while minocycline had an effect at a lower dose, 1 mg/kg/day ( P < 0.02). The inhibition of cerebral MMP-9 mRNA and activity were highly correlated with drug levels in the brain tissue. We also assessed the potential relevant signaling pathway in vitro to elucidate the mechanisms underlying the MMP-9 inhibition by tetracyclines. In vitro, minocycline, but not doxycycline, inhibits MMP-9, at least in part, via the extracellular signaling-related kinase 1/2 (ERK1/2)-mediated pathway. This study provided the evidence that the tetracyclines inhibit stimulated cerebral MMP-9 at multiple levels and are effective at very low doses, offering great potential for therapeutic use.
Persistent Tolerance to Oxygen and Nutrient Deprivation and N-methyl-D-Aspartate in Cultured Hippocampal Slices from Hibernating Arctic Ground Squirrel
Authors: Ross Austin P , Christian Sherri L , Zhao Huiwen W , Drew Kelly L
Published: January 2006

Hibernating Arctic ground squirrel (hAGS), Spermophilus parryii, survive profound decreases in cerebral perfusion during torpor and return to normal blood flow during intermittent rewarming periods without neurologic damage. Hibernating AGS tolerate traumatic brain injury in vivo, and acute hippocampal slices from hibernating animals tolerate oxygen and glucose deprivation. It remains unclear, however, if neuroprotection results from intrinsic tissue properties or from differences in response to acute trauma associated with slice preparation. The goal of this work was therefore to determine whether an intrinsic tissue tolerance persists in chronic culture of AGS hippocampal slices at 37 °C. A second goal was to address N-methyl-D-aspartate (NMDA) receptor involvement and channel arrest as potential mechanisms of intrinsic tissue tolerance. Baseline neuronal survival and tolerance to oxygen and nutrient deprivation (OND), an in vitro model of ischemia–reperfusion, were assessed in the CA1 region of hippocampal slices from juvenile, hAGS and interbout euthermic AGS (ibeAGS). Early in culture (insult onset at 3 h), slices from both hAGS and ibeAGS tolerate OND (4h deprivation followed by 20 h recovery) and 500 μmol/L NMDA plus 20 mmol/L KCl. Later in culture (insult onset at 24 h), tolerance persists in slices from hAGS but not in slices from ibeAGS. Ouabain (Na+K+ATPase inhibitor) administered 24 h in culture enhances survival of slices from hAGS (assessed 24h later). Thus, tolerance to OND in slices from hAGS is due to intrinsic tissue properties likely involving NMDA receptors and ion channel arrest.
Vertically integrated thin-film color sensor arrays for advanced sensing applications
Authors: Steibig H. , Street R. A. , Knipp D. , Krause M. , Ho J.
Published: January 2006

A three-color sensor array based on a vertically integrated thin-film structure is reported. The complete color information can be detected at the same position of a sensor array without using optical filters. The sensors consist of a multilayer thin-film system utilizing amorphous silicon and its alloys. The spectral sensitivity of the sensors is controlled by the optical properties of the materials and the applied bias voltage. The color sensors were integrated with amorphous silicon readout electronics to realize a large area thin-film three color sensor array. The working principle of the thin-film sensor arrays is presented with a discussion of the spectral sensitivity and the pixel cross talk.
Ultrafast heterogeneous electron transfer reactions: Comparative theoretical studies on time- and frequency-domain data
Authors: Wang Luxia , Willig Frank , May Volkhard
Published: January 2006

Recent theoretical studies on linear absorption spectra of dye-semiconductor systems [perylene attached to nanostructured TiO2, L. Wang et al., J. Phys. Chem. B 109, 9589 (2005)] are extended here in different respects. Since the systems show ultrafast photoinduced heterogeneous electron transfer the time-dependent formulation used to compute the absorbance is also applied to calculate the temporal evolution of the sub-100fs charge injection dynamics after a 10fs laser-pulse excitation. These studies complement our recent absorption spectra fit for two perylene bridge-anchor group TiO2 systems. Moreover, the time-dependent formulation of the absorbance is confronted with a frequency-domain description. The latter underlines the central importance of the self-energy caused by the coupling of the dye levels to the semiconductor band continuum. The used model is further applied to study the effect of different parameters such as (1) the dependence on the reorganization energies of the involved intramolecular transitions, (2) the effect of changing the transfer integral which couples the excited dye state with the band continuum, and (3) the effect of the concrete form of the semiconductor band density of states. Emphasis is also put on the case where the charge injection level of the dye is near or somewhat below the band edge. This nicely demonstrates the change from a structureless absorption to a well-resolved vibrational progression including characteristic shifts of the absorption lines which are a direct measure for the dye-semiconductor coupling.
Nonlinear fingering dynamics of reaction-diffusion acidity fronts: Self-similar scaling and influence of differential diffusion
Authors: Lima D. , D’Onofrio A. , De Wit A.
Published: January 2006

Nonlinear interactions between chemical reactions and buoyancy-driven Rayleigh-Taylor instability of reaction-diffusion acidity fronts of the chlorite-tetrathionate (CT) reaction are studied theoretically in a vertical Hele-Shaw cell or a porous medium. To do so, we perform a numerical integration of a two-variable reaction-diffusion model of the CT system coupled through an advection term to Darcy’s law ruling the evolution of the velocity field of the fluid. The fingering dynamics of these chemical fronts is characterized by the appearance of several fingers at onset. These fingers then undergo coarsening and eventually merge to form one single symmetric finger. We study this asymptotic dynamics as a function of the three dimensionless parameters of the problem, i.e., the Damköhler number Da, the diffusivity ratio δ of the two chemical species, and the Rayleigh number Ra constructed here on the basis of the width Ly of the system. For moderate values of Ra, the asymptotic single finger is shown to have self-similar scaling properties while above a given value of Ra, which depends on the other values of the parameters, tip splitting comes into play. Increasing the difference of diffusivities of the two chemical species (i.e., increasing δ) leads to more efficient coarsening and smaller asymptotic fingers. Experimental procedures to verify our predictions are proposed.
Visible spectrum light-emitting transistors
Authors: Dixon F. , Chan R. , Walter G. , Holonyak N. , Feng M. , Zhang X. B. , Ryou J. H. , Dupuis R. D.
Published: January 2006

Visible radiative recombination in the base layer of AlGaInP∕InGaP light-emitting transistors (LETs) is reported. For this form of transistor, which previously has not existed, and with an emitter area of 100×100μm2, we demonstrate a current gain β (β≡ΔIC∕ΔIB) of 3.5 for the device operating in the common-emitter configuration. The LET In0.49Ga0.51P base recombination radiation is centered in the visible at λ=650nm (red emission).
Photorefractive nematic liquid crystals with gain of constant sign under alternating voltage
Authors: Kesti Tero , Golemme Attilio
Published: January 2006

Two-beam coupling gain of constant sign was observed in hybrid planar/homeotropic nematic cells under a nonbiased square-wave ac field. Charge photogeneration was induced by using one layer of photoconducting polymer. With writing beams of equal intensities, gains up to 6% were observed in ∼10μm thick samples when the amplitude of the applied field was of the order of 1Vμm−1 at 10Hz. The gain decreased gradually when the frequency was increased, vanishing above 100Hz.
Role of intrinsic defects in the electronic and optical properties of α-HgI2
Authors: Ayres F. , Assali L. V. C. , Machado W. V. M. , Justo J. F.
Published: January 2006

We investigated the role of intrinsic defects in the electronic and optical properties of mercuric iodide using ab initio methods. The calculations were performed using the total energy all electron methodology, considering full atomic relaxation. We computed the band structure, spin, formation and transition energies, and the dielectric function of isolated iodine and mercury vacancies in several charge states. Our results were compared to available experimental data on photoluminescence and photoplasticity in HgI2. We propose a microscopic model which can explain most of the data on those luminescent centers, unifying experimental results which suggested conflicting conclusions.
Vacuum electron field emission from SnO2 nanowhiskers annealed in N2 and O2 atmospheres
Authors: Luo Suhua , Chu Paul K. , Di Zengfeng , Zhang Miao , Liu Weili , Lin Chenglu , Fan Jiyang , Wu Xinglong
Published: January 2006

The field emission properties of SnO2 nanowhiskers were observed to change after annealing under O2 and N2. The electron current increased significantly from the sample annealed in N2 and the threshold field decreased from 3.17V∕μm of the as-grown sample to 2.59V∕μm of the annealed sample. The mechanism of the field emission enhancement was explored using Fourier transform infrared spectroscopy and x-ray photoelectron spectroscopy (XPS). The results reveal that after annealing in N2, the amount of Sn–O bonds decreased and N atoms were introduced onto the surface. The binding energies of Sn 3d and O 1s determined by high resolution XPS analysis show a shift of 0.55 and 0.47eV, respectively, toward the high energy side. This shows that the electron emission enhancement arises from a decrease in the work function. The changes in the field emission effect from the sample annealed in O2 are different and a possible mechanism is also proposed.
Control of magnetic anisotropy and magnetic patterning of perpendicular Co∕Pt multilayers by laser irradiation
Authors: Schuppler C. , Habenicht A. , Guhr I. L. , Maret M. , Leiderer P. , Boneberg J. , Albrecht M.
Published: January 2006

We report an approach to altering the magnetic properties of (111) textured Co∕Pt multilayer films grown on sapphire (0001) substrates in a controlled way using single-pulse laser irradiation. The as-grown films reveal a strong perpendicular magnetic anisotropy induced by interfacial anisotropy. We show that laser irradiation can chemically mix the multilayer structure particularly at the interfaces, hence reducing the perpendicular magnetic anisotropy and coercivity in a controlled manner depending on laser fluence. As a result, perpendicular films can also be magnetically patterned into hard and soft magnetic regions using a regular two-dimensional lattice of polystyrene particles acting as an array of microlenses.
Detection of nano-confined DNA using surface-plasmon enhanced fluorescence
Authors: Cloutier Sylvain G. , Lazareck Adam D. , Xu Jimmy
Published: January 2006

Surface-plasmon resonance (SPR)-induced enhanced fluorescence was used to detect the presence of fluorescent TOTO-1 bis-intercalated lambda-DNA complexes introduced into a periodic nanopore array. As we show, the proposed technique allows a high detection sensitivity by providing a strong fluorescence-signal efficiency from nano-confined fluorescent complexes. This novel platform could be used for sensing applications, or to detect and investigate the unique behaviors of nano-confined molecular systems.
Conductance quantization and the 0.7×2e2∕h conductance anomaly in one-dimensional hole systems
Authors: Danneau R. , Clarke W. R. , Klochan O. , Micolich A. P. , Hamilton A. R. , Simmons M. Y. , Pepper M. , Ritchie D. A.
Published: January 2006

We have studied ballistic transport in a one-dimensional (1D) channel formed using surface gate techniques on a back-gated, high-mobility, bilayer two-dimensional hole system. At millikelvin temperatures, robust conductance quantization is observed in the quantum wire formed in the top layer of the bilayer system, without the gate instabilities that have hampered previous studies of 1D hole systems. Using source drain bias spectroscopy, we have measured the 1D subband spacings, which are 5–10 times smaller than in comparable GaAs electron systems, but 2–3 times larger than in previous studies of 1D holes. We also report the first observation of the anomalous conductance plateau at G=0.7×2e2∕h in a 1D hole system.
Observation of the flux-antiflux boundary propagation during magnetization reversal in Bi2Sr2CaCu2O8+δ with single vortex resolution
Authors: Schwarz A. , Pi U. H. , Liebmann M. , Wiesendanger R. , Khim Z. G. , Kim D. H.
Published: January 2006

Snapshots of the flux distribution during magnetization reversal of a high-temperature superconductor Bi2Sr2CaCu2O8+δ single crystal in the presence of artificial columnar defects were recorded using magnetic force microscopy. Thereby, the flux-antiflux boundary width and its displacement by annihilation of individual vortex-antivortex pairs could be visualized. In general the flux density follows Bean’s model. However, step dislocations with a strongly anisotropic pinning behavior lead locally to a nonmonotonous flux distribution and result in a delay of the boundary propagation.
Light-induced bioactive TiO2 surface
Authors: Liu Xuanyong , Zhao Xiaobing , Ding Chuanxian , Chu Paul K.
Published: January 2006

We have achieved bioactivity enhancement of nanostructured titania using ultraviolet (uv) light irradiation. The titania coating fabricated by nanoparticle plasma spraying consists of a nano-TiO2 coating surface composed of primarily nanosized anatase. After irradiation by ultraviolet light in air for 24 h, the as-sprayed and UV-irradiated TiO2 coatings were soaked in simulated body fluids (SBF) to investigate their bioactivity. The UV-illuminated TiO2 coating induced bonelike apatite formation on the surface whereas no apatite could be detected on the as-sprayed TiO2 coating. The formation of oxygen vacancies at the two-coordinated bridging sites by UV illumination is believed to result in the conversion of the corresponding Ti4+ sites to Ti3+ sites, which are favorable to the dissociation of water in the SBF and subsequent formation of Ti-OH and an apatite layer. Our results reveal that the surface bioactivity of titania coatings can be induced by UV illumination.
Review: Environmental biology and crop improvement
Authors: Passioura John B.
Published: January 2006

The average yield of Australia’s major grain crop, wheat, rose at its
fastest rate ever during the last decade. The environmental biology behind
this advance was predominantly ecological and nutritional — endemic root
diseases were controlled through better management of inoculum levels, and the
consequently healthier crops were more responsive to fertiliser, especially
nitrogen. Applying nitrogen fertilisers became less risky; farmers used much
more and thereby achieved much higher yields. Despite Australia’s
reputation for being drought prone, its crop yields have not hitherto been
typically limited by water — poor health and poor nutrition have been
more influential. Improvements in the management of health and nutrition have
resulted in many crops now being limited by water, so the effectiveness with
which that water is used in producing grain has become more important —
capturing more of it, using it effectively in producing photosynthate, and
ensuring that a large fraction of that photosynthate is converted into grain.
Further improvement will come from the steady 1% per year achieved by
breeders, overlain by agronomic advances based on deeper ecophysiological
understanding of the interaction between roots and soil biota, how roots
access resources in the subsoil, and the basis of spatial variation in yield
across a paddock.
Dual targeting ability of targeting signals is dependent on the nature of the mature protein
Authors: Chew Orinda , Whelan James
Published: January 2006

The targeting ability of three signals previously shown to support the import of passenger proteins into both mitochondria and chloroplasts was investigated with authentic mitochondrial or chloroplastic proteins. An in vitro dual import assay that maintained import specificity showed that the ability of dual signals to support mitochondrial and chloroplastic import depended on the nature of the passenger protein. All dual targeting signals supported import of their native mature protein as a passenger into both mitochondria and chloroplasts. However the glutathione reductase targeting signal only supported mitochondrial import with the mitochondrial protein alternative oxidase, and chloroplast import with the small subunit of ribulose-1,5-bisphosphate carboxylase / oxygenase. The Arabidopsis histidyl-tRNA synthetase targeting signal only supported mitochondrial import with the alternative oxidase as a passenger, but the small subunit of ribulose-1,5-bisphosphate carboxylase / oxygenase was imported into both mitochondria and chloroplasts. The Arabidopsis asparaginyl-tRNA synthetase supported import of alternative oxidase and the small subunit of ribulose-1,5-bisphosphate carboxylase / oxygenase into both mitochondria and chloroplasts. Analysis of the targeting signals of all known dual targeted proteins using targeting predictions indicates that most of them are more strongly predicted to be chloroplast-targeted. Secondary structure predictions indicate the ability of most dual targeted signals to form both α-helical and β-sheet-type structures, a feature of mitochondrial and plastid targeting signals, respectively. Thus, it appears that a major determinant of dual targeting ability is the nature of the mature or passenger protein.
Colletotrichum gloeosporioides infection induces differential expression of glutathione S-transferase genes in Malva pusilla
Authors: Dean J. Doug , Goodwin Paul H. , Hsiang Tom
Published: January 2006

Among a collection of 840 expressed sequence tags of Malva pusilla leaves infected with Colletotrichum gloeosporioides f. sp. malvae (Cgm), a total of four different glutathione S-transferase (GST) (EC 2.5.1.18) genes were identified, each showing a different pattern of expression following infection. MpGSTU1 and MpGSTU2 were members of the class tau GSTs, MpGSTF1 was a member of the class phi GSTs, and MpGSTZ1 belonged to the class zeta GSTs. Infection by Cgm occurs by a hemibiotrophic process with an initial biotrophic phase preceding the necrotrophic phase and the appearance of symptoms. Expression of MpGSTZ1 progressively increased during infection, corresponding directly with the growth of the pathogen. Expression of MpGSTU2 was similar to that of MpGSTZ1, except for a greater increase during the late necrotrophic phase. MpGSTU1 expression remained relatively constant throughout the infection, whereas MpGSTF1 expression was induced primarily during the conversion from the biotrophic to necrotrophic phases of infection. Incubation of healthy mallow leaves in the dark resulted in decreased expression of MpGSTF1 and MpGSTU1, but not MpGSTZ1 and MpGSTU2. The differential expression patterns indicate that these mallow GST genes play a variety of roles in healthy and fungal-infected leaf tissue. The nucleotide sequences reported in this paper have been submitted to GenBank under the accession numbers AY206003, AY206001, AY206002, AY206000 and AY205999.
Corroboreethrips, a new genus of minute apterous thrips (Insecta : Thysanoptera : Phlaeothripinae) from the bark of Australian Acacia trees
Authors: Mound Laurence A. , Moritz Gerald
Published: January 2006

Six new species are described in the new genus
Corroboreethrips: C. kallus, sp.
nov., C. siagonus, sp. nov.,
C. stomius, sp. nov.,
C. subsolanus, sp. nov.,
C. suspectus, sp. nov. and
C. zophus, sp. nov. They all live in cavities beneath
thin, split bark of slender branches on particular
Acacia tree species in arid parts of Australia, and two
species-pairs show a vicariant distribution between Queensland and Western
Australia. In life, adults of these minute black, wingless thrips are
remarkable in appearance, decorated with irregular rows of tiny white dots,
the product of numerous short, stout dorsal setae coated with a white waxy
substance. The structure of the antennae of these species is unique within the
Phlaeothripidae, with segments VII and VIII short and forming a small style
that is closely joined to segment VI, segment III produced basally into a
sleeve around the pedicel, and segment II strongly asymmetric. The mouth cone
varies in length among the six species more than in any other known thrips
genus. In two species it is relatively short, extending to the fore coxae, but
in two others it extends as far as the hind coxae and is thus relatively
longer than in any other phlaeothripid.
New Ampithoid Amphipods from Port Jackson, New South Wales, Australia (Crustacea : Amphipoda : Ampithoidae)
Authors: Poore Alistair G. B. , Lowry James K.
Published: January 2006

Seven species of ampithoid amphipods are reported from subtidal macroalgae
living in Port Jackson, Sydney, Australia. In the genus
Ampithoe the Indo–West Pacific species
Ampithoe kava Myers, 1985, is recorded for the first
time from Australia, and two new species, A. caddi, sp.
nov. and A. ngana, sp. nov., are described. One new
species ofCymadusa,C. munnu, sp.
nov., is described. The genera Exampithoe
(Melanesius), Peramphithoe and
Plumithoe are recorded for the first time from
Australian waters. The new species E.
(M.) kutti, sp. nov. and
Peramphithoe parmerong, sp. nov. are described, and
Plumithoe quadrimana (Haswell,
1879b), comb. nov. is redescribed and a neotype is
selected. New ecological and behavioural information is presented for these
species. A new key and diagnoses for all known genera of Ampithoidae are
presented. Paradusa Ruffo, 1969 is synonomised with
Cymadusa Savigny, 1816.Exampithoe
(Melanesius) gracilipes Ledoyer,
1984 is transferred to Exampithoe
(Exampithoe) and Cymadusa uncinata
Stout, 1912 and C. variata Sheard, 1936 are transferred
to Paragrubia.
The ground-dwelling leafhoppers Myerslopiidae, new family, and Sagmatiini, new tribe (Homoptera : Membracoidea)
Authors: Andrew K. G.
Published: January 2006

The world fauna of 28 leafhopper species living in moss or leaf litter
(formerly subfamily Myerslopiinae) belong to 3 unrelated tribes: (1)
Evansiolini (subfamily Megophthalminae) - 3 species of
Evansiola Metcalf from Juan Fernández Is (Chile);
(2) Sagmatiini, trib. nov. (subfamily Euacanthellinae) - one species of
Paulianiana Evans from Madagascar, 3 new species of
Sagmation, gen. nov. from Australia and New Caledonia,
and 6 species (5 new) of Myerslopella Evans from
Australia; (3) true Myerslopiini - 5 species of Myerslopia Evans from Chile
and New Zealand and 10 species of Pemmation, gen. nov.
from New Zealand. Myerslopiini are placed in the new family Myerslopiidae,
exhibiting a combination of cicadoid and cercopoid features not found in other
Membracoidea. Keys are presented to the genera and species of Sagmatiini, and
a phylogeny of the families of Membracoidea is proposed based on 35
synapomorphies.
A revision of the Pseudojaniridae Wilson, with a description of a new genus of Stenetriidae Hansen (Crustacea : Isopoda : Asellota)
Authors: Serov Peter A. , Wilson George D. F.
Published: January 2006

The discovery of asellotan isopod species resembling
Stenetrium, but with male pleopods like those in the
genus Pseudojanira Barnard, 1925 necessitated a
re-examination of the taxonomy of the family Pseudojaniridae Wilson, 1986.
Data presented in this paper support the assignment of the Pseudojaniridae to
the superfamily Stenetrioidea Hansen, 1905, thus eliminating the superfamily
Pseudojaniroidea Wilson. A new definition of the Stenetrioidea and a generic
key are provided. The genus Pseudojanira and its species
are revised, including a species-level key. A study of
Pseudojanira investigatoris Poore and Just, 1990 has
revealed two new cryptic species,
Pseudojanira fremantlensis, sp. nov. and
Pseudojanira justi, sp. nov. Some paratypes and other
specimens originally classified as
Pseudojanira investigatoris are reassigned to other
species. Descriptions of two new monotypic genera of the
Pseudojaniridae,
Schottea taupoensis, gen. nov., sp. nov.
andAdajinoperus tetanomorphus, gen. nov., sp. nov.
further expand the recognised morphological diversity of this family. A new
genus of Stenetriidae, Lexcenium, gen. nov., with two
new species, L. poorei, sp. nov. and
L. greenensis, sp. nov., provides additional evidence of
the diverse, non- homologous forms of the ‘stylet-like’ appendix
masculina within the superfamily.