bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of Trace Elements in the Study of Oil-Source Correlation and Hydrocarbon Migration in the Tarim Basin, China
Authors: Jiao Weiwei , Yang Haijun , Zhao Yue , Zhang Haizu , Zhou Yuanyuan , Zhang Jie , Xie Qilai
Published: January 2011

Oil source and hydrocarbon migration are critical in the study of hydrocarbon accumulation. Under the complicated conditions of hydrocarbon accumulation, traditional organic geochemistry has its limitation. Therefore, the purpose of this study is to try a new way to investigate hydrocarbon accumulation and migration. The occurrence of trace elements in crude oil and their activation and migration were studied. The fingerprint of trace elements was discussed. Our results indicate that rare earth elements and transition metals could be used for study of oil-source under the complicated conditions of hydrocarbon accumulation and migration. V/Ni ratio was a specific indicator in tracing hydrocarbon migration pathway. Tarim Basin, a typical complex superimposed basin in west China was studied. The result indicated that crude oil from the Ordovician in Tazhong (central Tarim) low uplift was characterized by mixed sources. The contributions of individual sources differed from formation to formation and from block to block. The distribution of underground fluid was significantly controlled by large-scale strike-slip faults. Our study result is consistent with the knowledge of field geologists. Application of trace elements as indicators is an effective method to study hydrocarbon accumulation and migration.
Research on Stratigraphic Division and Sand Bed Correlation Based on “Three Instantaneous” Attribute Spectra of Logging Data
Authors: Xu Jingling , Liu Luofu , Wang Guiwen , Su Benyu
Published: January 2011

The stratigraphic division and sand bed correlation are an important and difficult work for exploration and development of oil-gas field. The application of “three instantaneous” attribute spectrum of logging data on the research of stratigraphic division and sand bed correlation is carried out first time by the authors. In the method, mainly Hilbert-Huang transformation was used to extract the three attributes from logging data (natural gamma ray, Acoustic, and so on), i.e. “instantaneous frequency”, “instantaneous amplitude” and “instantaneous phase”, and then the technology of high-resolution profile reconstruction was adopted to reconstruct the “three instantaneous” attribute spectrum, to reveal the geological response characteristics on each depth of the internal formation, and to clearly reflect the variation characteristics of geological phenomena in the formation. The sequence boundary is scaled according to the alternating change of “three instantaneous” attribute energy spectrum, the migration cycle changes and distribution characteristics of attribute spectrum energy cluster of different frequency components are used to scale the stratigraphic units of different sizes and the response characteristics of sand and mud, and then the oscillation change trend and distribution information of “three instantaneous” attribute spectra energy cluster from low frequency to high frequency is utilized to do the division and correlation of formation and sand body, and to depict geological characteristics of formation internal. From the change and distribution of attribute spectrum energy cluster, the boundary of different sequence grade and distribution of sand bed in stratigraphic sequence can be clearly found. Then, sequence division and single sand body identification of all levels are realized. The single sand body isochronous correlation is compared under the control of all levels sequence division. The research results of this paper promote sedimentary reservoir bed and sequence stratigraphy development toward quantification and digitalization, and provide a new method for geological studies.
Characteristics of Fluid Inclusions and its Significance to the Coaliferous Gas Reservoirs of the Xujiahe Formation in the Central Sichuan Basin, China
Authors: Tao Shizhen , Zou Caineng , Wang Zecheng , Gong Yanjie , Gao Xiaohui , Wu Xiaoqi , Lin Senhu
Published: January 2011

In the central Sichuan Basin, the maturity of source rocks in the Xujiahe Formation of the Upper Triassic is not high, with Ro values ranging from 0.8% to 1.2%. However, the gas reservoirs nowadays show characteristics of high gas-oil ratios and low condensate oil content (3.8–91.9 g/m3 on average). There are abundant gas hydrocarbon inclusions developed in the reservoir, with few liquid hydrocarbon inclusions, which indicates that the coal measures gave priority to gas rather than oil. In the fluid inclusion group, the CH4 and C2H6 contents are 79.62–96.42% and about 10% respectively, while the content of C3H8 ranges from 3% to 5%. The carbon isotope values are δ13C1= −44.59 ∼ −39.31‰, δ13C2= −24.82 ∼ −28.05‰, δ13C3= −21.39‰, δ13C4= −22.05 ∼ −20.2‰, δ13Cco2= −9.14 ∼ −13.86‰. The component and isotope compositions of gas in fluid inclusions coincide with those in the reservoirs, indicating that the gas hydrocarbon in the fluid inclusions can represent the residual gas in the reservoirs. The coal-measure source rocks can generate gas all the time during its burial process. The formation of salt-water inclusions associated with the gas inclusions can be divided into three stages. Firstly, the subsidence stage was at 170∼100 Ma, with the temperature of 70∼120°C. Secondly, the deep burial stage was during 100∼60 Ma, with the temperature of 120∼150°C. Thirdly, the uplift stage was at 60∼0 Ma, with the temperature of 90∼120°C. The time range reflected from gas inclusion is very wide, showing that the coal measures gave priority to gas hydrocarbon and can generate and expel gas continuously in a long period.
Comparison of the Biodiesel Quality Produced from Refined Sunflower (Helianthus Annuus L) Oil and Waste Cooking Oil
Authors: Saydut Abdurrahman , Kafadar Aylin Beycar , Tonbul Yalcin , Kaya Canan , Aydin Firat , Hamamci Candan
Published: January 2011

A major hurdle in commercialization of biodiesel from vegetable oil, in comparison to petroleum-based diesel fuel, is its cost of manufacturing, primarily the raw material cost. Waste cooking oil is one of the economical sources for biodiesel production. NaOH and KOH catalyzed processes for prepared of biodiesel expressed of fatty acid methyl ester were comparatively studied for refined sunflower ( Helianthus annuus L) oil and waste cooking oil. Transesterification was carried out using 100% excess methanol; i.e. molar ratio of methanol to oil is 6:1 and catalyst concentration of 0.5% at 60°C. Fuel properties and specifications such as viscosity, flash point, cloud point, pour point, density, cetane number, and acidic value are determined and compared to each other and petroleum diesel. This study characterizes the fuel properties of biodiesel produced from refined sunflower oil and waste cooking oil using two different catalysts (NaOH and KOH) to provide a comprehensive understanding of biodiesels.
Petrology and Geochemistry of the Jurassic Coals in Southwestern Ordos Basin, China
Authors: Wang Xibo
Published: January 2011

This study is related to seven Jurassic bituminous coal samples collected from four mines of the Huanglong coalfield, southwestern Ordos Basin, China. Petrological and geochemical characteristics of these samples were investigated. The results show that these Jurassic coals are high in inertinite (54 vol. %), followed by vitrinite (31.7 vol.%) and liptinite (3.7 vol.%). The mineralogy of the coals is dominated by illite, kaolinite, quartz, calcite, pyrite, and less siderite, feldspar, goyazite, anatase, illite-smectite, dolomite, and marcasite. These coals are low in sulfur (0.18–0.71%). With the exception of the No. 4 coal from the Dafosi mine, in which the total sulfur is 1.32% and the pyritic sulfur is up to 0.78%. Compared to common Chinese coals, the Jurassic coals are much high in CaO (2.12%), MgO (0.26%), P2O5 (0.21%), Sr (591 μg/g), Ba (476 μg/g), and F (187 μg/g). The excess P, Sr, and Ba in the BMF-2 and BMF-4 are mainly present in goyazite-gorceixite series minerals (goyazite). The content of rare earth elements ranges from 32.2 to 154 μg/g (mean 80.6 μg/g). The chondrite-normalized distribution pattern is typically characterized by the enrichment of LREE over HREE. And the high anomaly Eu value (0.86) of these Jurassic coals was probably inherited from its source detrital rocks.
Adsorption Thermodynamics of Methyl Orange from Aqueous Solution onto a Hyper-Cross-Linked Polystyrene Resin Modified with Phenolic Hydroxy Groups
Authors: Huang Jianhan
Published: January 2011

A novel hyper-cross-linked polystyrene resin, HJ-P01, was prepared and its structure characterized via nitrogen adsorption/desorption isotherms, its residual chlorine content and its Fourier-transform infrared (FT-IR) spectrum. The adsorption isotherms of Methyl Orange from aqueous solution onto HJ-P01 resin were subsequently measured and the corresponding thermodynamic parameters calculated. The results indicated that HJ-P01 resin possessed a micro-/meso-porous structure, with its surface being chemically modified by phenolic hydroxy groups. The resin was capable of the effective adsorption of Methyl Orange from aqueous solution, although its adsorption capacity decreased with increasing temperature. The adsorption isotherms could be fitted by the Freundlich isotherm model and the adsorption was shown to be a spontaneous, exothermic process leading to a more ordered system.
Adsorption of Lead(II) Ions onto Magnetite Nanoparticles
Authors: Wang Xue Song , Lu Hai Jie , Zhu Lei , Liu Fei , Ren Jun Jun
Published: January 2011

Magnetite nanoparticles were applied for the removal of lead(II) ions from aqueous solution as a function of pH, contact time, supporting electrolyte concentration and initial analytical Pb(II) ion concentration. The highly crystalline nature of the magnetite structure with pore diameters of ca. 10 nm was characterized by transmission electron microscopy (TEM) and X-ray diffractometry (XRD). The surface area was determined as 115.3 m2/g. The surface chemical properties of magnetite in aqueous solution at 25 °C were investigated.

Batch experiments were carried out to determine the adsorption kinetics and adsorption mechanism of Pb(II) ions by the magnetite nanoparticles. The adsorption of Pb(II) ions was mainly governed by surface complexation, with the adsorption process being pH-dependent. In NaCl solutions, Pb(II) ion adsorption increased with increasing ionic strength; however, in NaClO4 solutions, Pb(II) ion adsorption exhibited little dependence on the ionic strength of the solution.

Kinetic studies were performed to understand the mechanistic steps involved in the adsorption process. The adsorption kinetic data for Pb(II) ions were best fitted by the fractional power equation. The Langmuir and Freundlich adsorption isotherms were applicable to the equilibrium adsorption process and the corresponding constants were evaluated. The maximum adsorption capacity (qm) calculated from the Langmuir isotherm was found to be 0.1105 mmol/g for Pb(II) ions at a pH value of 5.0 and at 25 °C.
Control of Iron(III) Scaling in Industrial Cooling Water Systems by the Use of Maleic Anhydride–Ammonium Allylpolyethoxy Sulphate Dispersant
Authors: Fu Change , Zhou Yuming , Huang Jingyi , Xie Hongtao , Liu Guangqing , Wu Wendao , Sun Wei
Published: January 2011

In an attempt to control iron(III) scaling in industrial cooling water systems, a maleic anhydride (M)/ammonium allylpolyethoxy sulphate (S) copolymer (MSn, n = 5, 9, 13, 20) was examined as an environmentally friendly dispersant. The synthesized MSn copolymer was characterized by Fouriertransform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The ability of MSn to disperse iron(III) increased as the value of n increased from 5 to 13; however, the ethylene oxide chain in MS20 was so long that the molecule readily curled and hence its dispersion capability towards iron(III) decreased. It was also shown that MS13 exhibited the best dispersion activity towards iron(III), with ca. 28% light transmittance being achieved when the dosage of MS13 was 10 mg/ℓ. The proposed dispersion suggests the formation of a core–shell superstructure, with interactions between various kinds of iron ions and the side-chain oxygen atoms of ethylene oxide being the principal means whereby iron(III) may be dispersed in cooling water systems.
Biosorption of Chromium(III) and Copper(II) Ions onto Marine Alga Sargassum sp. in a Fixed-bed Column
Authors: Silva E.A. , Vaz L.G.L. , Veit M.T. , Fagundes-Klen M.R. , Cossich E.S. , Tavares C.R.G. , Cardozo-Filho L. , Guirardello R.
Published: January 2011

The simultaneous biosorption of chromium(III) and copper(II) ions onto Sargassum sp. alga in a fixed-bed column reactor was investigated. Experiments were undertaken to determine the effect of the feed concentration (1, 2, 3 and 6 mequiv/ℓ) and the composition of the metal ion solution [0.25, 0.50 and 0.75 Cu(II)/Cr(III) ratio] on the behaviour of the breakthrough curves. A mathematical model was applied to describe the biosorption in a fixed-bed column. Equilibrium was described in this model in terms of a binary Langmuir-type adsorption process, together with mass transfer in the biosorbent based on the Linear Driving Force (LDF) model. The partial differential equations for the system were solved numerically by the finite volume method. The proposed mathematical model for the biosorption process provided a satisfactory description of the dynamics of metal ion removal in the column relative to the experimental data obtained. The adsorptive capacity of the biomass for Cr(III) ions in the binary system was greater than that for Cu(II) ions. The developed model could provide a useful tool for the optimization of Cr(III) and Cu(II) ion removal processes by Sargassum sp. biomass and the design of the corresponding fixed-bed columns.
Sonic Quality in the Living Environment Traditional and Recent Urban Structures: Learning from the Past
Authors: Debache-Benzagouta Samira
Published: January 2011

During the last 50 years, most Islamic countries have lost their urban and architectural heritage; they opted for a contemporary urban structure imported from Western countries; and, as a result, they lost their identity and missed the opportunity to preserve their valuable Islamic architectural heritage. Our cities are losing their historic styles and the impact of modernisation has led to a rupture of continuity between the inherited morphology and more recent urban structure.

On the other hand, Western designers are impressed by Medinas and old cities; they are seeking and investigating established techniques and ways of construction which have proved their effectiveness and success.

It seems that we have forgotten that traditional architecture proved its effectiveness in reducing heat, cold, noise, humidity, etc., inside buildings; that is an important message for modern designers. Our architectural heritage is a force that should link and connect past, present and future communities.

This study investigates the acoustic comfort and design intentions of the traditional house; it compares techniques used for reducing noise in traditional local buildings and modern apartments and identifies how to integrate sonic quality to architectural design. This may provide an alternative approach for designers and developers who are able to create architecture that will be the heritage of tomorrow. Our research focuses on objective sound levels, in different indoor and outdoor spaces. In conjunction with these measures, we correlate the use patterns in different zones of the buildings and the effect of noise on the inhabitants. Our intention is to present a multidisciplinary study on sonic quality in housing and public spaces and to promote traditional ways of construction.
Propagation of Rich Premixed Polydisperse Spray Flames
Authors: Greenberg J. B. , Kagan L. S. , Sivashinsky G. I.
Published: January 2011

A new numerical study of rich laminar polydisperse spray flame propagation in a two-dimensional channel is presented, within the framework of a thermal-diffusional model. Two different polydisperse sprays having the same Sauter mean diameter were considered. Attention is focused on the development of spray induced instabilities and the way they are sensitive to the initial droplet size distribution. Previous work in this field was based on linear stability analyses. The current work allows nonlinear stability aspects to be captured. It was found that both cellular and oscillating instabilities can develop, depending on the evaporation coefficient of the liquid fuel. However, the transitions from planar propagation to cellular propagation and from the latter to oscillating propagation occur at different critical values of the evaporation coefficient depending on what the initial droplet size distribution actually is. Therefore, use of the Sauter mean diameter to represent a polydisperse spray can be misleading in the current context and the real size distribution must be considered.
Rigorous Derivation of an Unclosed Mean G-Equation for Statistically 1D Premixed Turbulent Flames
Authors: Sabel'nikov Vladimir A. , Lipatnikov Andrei N.
Published: January 2011

A promising approach to simulating premixed turbulent combustion in gas turbine and spark ignition engines consists of tracking an average flame surface in an average velocity field. Although such an approach is widely used both within RANS and LES framework, the basic substantiation of the corresponding kinematic (or level set, or mean Gt) equation has not yet been elaborated well. The goal of the present paper is to derive such an equation in a straight forward manner from the well-known G-equation for tracking an infinitely thin flame sheet (flamelet) in a turbulent flow in the simplest case of a statistically one-dimensional premixed turbulent flame. The derived equation clarifies the physical meaning of (i) the speed of the self-propagation of the mean flame surface and (ii) the mean flow velocity used to track the surface. In order for the mean flame speed to be equal to the turbulent burning velocity, the velocity used to track the mean flame should differ from the mean flow velocity at the flame surface. In the simplest case of a statistically one-dimensional (planar or spherical) premixed turbulent flame, the former velocity is equal to the extrapolation of the mean velocity profile in the fresh gas to the mean flame surface. An extension of the aforementioned kinematic equation to a general three-dimensional case is discussed.
Characteristics of Oscillating Flames in a Coaxial Confined Jet
Authors: Cha Min Suk , Chung Suk Ho
Published: January 2011

Flame characteristics when a non-premixed n-butane jet is ejected into a coaxial cylindrical tube are investigated experimentally. Flame stability depends mainly on the characteristics of flame propagation as well as air entrainment which depend on the jet momentum and on the distance between the nozzle exit and the base of a confined tube. As flow rate increases, the flame lifts off from a nozzle attached diffusion flame and a stationary lifted flame can be stabilized. The liftoff height increases nearly linearly with the average velocity at the nozzle exit. The lifted flame has a tribrachial flame structure, which consists of a rich premixed flame, a lean premixed flame, and a diffusion flame, all extending from a single location. As flow rate further increases, periodically oscillating flames are observed inside the confined tube. Once flame oscillation occurs, the flame undergoes relatively stable oscillation such that it has nearly constant oscillation amplitude and frequency. The criteria of flame oscillation are mapped as functions of nozzle diameter, the distance between nozzle and tube, and jet velocity. This type of flame oscillation can be characterized by Strouhal number in terms of flame oscillation amplitude, frequency, and jet velocity. Buoyancy driven flame oscillation which is one of the viable mechanism for flame oscillation is modeled and the results agrees qualitatively with experimental results, suggesting that the oscillation is due to periodic blowoff and flashback under the influence of buoyancy.
Modeling and Control of a Hovering Mini Tail-Sitter
Authors: Bilodeau Pierre-Richard , Wong Franklin
Published: January 2011

A systematic approach to characterize and control the attitude of a hovering tail-sitter mini-aerial vehicle (TS-MAV) is developed. A model of the TS-MAV dynamics is formulated by decoupling and linearizing a nonlinear model based on quaternions. Identification of the model parameters was carried out using a prediction error method and flight test data. Two control structures were synthesized to examine the benefits of using an anti-windup proportional-integral regulator in the inner control loop rather than in the outer control loop. It was found that a regulator in the inner loop reduced overshoot and eliminated an unstable pole. Flight tests with a TS-MAV test bed showed that a nine percent overshoot was reduced to zero thereby demonstrating the enhanced responsiveness of the vehicle using this control strategy.
Non-Line-of-Sight Indoor Localization of Micro Air Vehicles Using First-Arrival Sound
Authors: Mak Lin Chi , Furukawa Tomonari
Published: January 2011

This paper presents a technique and its system that localizes a rotary-wing Micro Air Vehicle (MAV) in indoor environments even under Non-Line-of-Sight (NLoS) conditions. The technique is based on the system with the MAV having a wireless microphone and a ground station having multiple microphones. The technique identifies the location of the MAV in two-dimensional space by measuring the Time-of-Arrival (ToA) of acoustic signals caused by the rotation of blades at the MAV. The technique then applies an iterative algorithm that corrects the NLoS errors and computes the true ToA based on maps of known indoor environments in a computationally inexpensive manner. To suppress noise in the received signals and thus improve the robustness of ToA estimation, the generalized cross-correlation with phase transform and a bandpass filter is derived and applied. The performance of the proposed technique was examined experimentally by its comparison with three existing ToA-based localization techniques. Experimental results show the superiority of the proposed technique, demonstrating its potential for aiding indoor MAVs in autonomous navigation.
Vector Field Guidance for Path following of MAVs in Three Dimensions for Variable Altitude Maneuvers
Authors: Meenakshisundaram Vaitheeswaran S. , Gundappa Venkatanarayana K. , Kanth B. Sashi
Published: January 2011

This paper uses the vector field approach to represent both the desired ground track heading and the vertical flight path angle to navigate unmanned aerial vehicles onto the desired path. The path following is realized in 3-dimensions, thus allowing the aircraft to navigate longitudinally as well as laterally, unlike the current approaches which require the aircraft to maintain a constant altitude. This results in an increase in the maneuverability (like overflying a hill) of the vehicle allowing it to navigate over various terrains and terrain following. Methods for following straight lines in 3-dimensional space are demonstrated through numerical simulations.
Efficient and green synthesis of new polycyclic procyanidin derivatives via tandem dinucleophilic addition of indolin-2-thiones to flavylium salts
Authors: Moghaddam Firouz Matloubi , Foroushani Behzad Koushki , Saeidian Hamdollah , Nourian Saghar , Mirjafary Zohreh , Kiamehr Mostafa
Published: January 2011

The green synthesis of a new series of polycyclic procyanidin derivatives has been achieved in good yields by tandem dinucleophilic addition of indolin-2-thiones to flavylium salts. The procedure is efficient and simple, and the substrates are easily available.
Coercive Forms of Sexual Risk and Associated Violence Perpetrated by Male Partners of Female Adolescents
Authors: Silverman Jay G. , McCauley Heather L. , Decker Michele R. , Miller Elizabeth , Reed Elizabeth , Raj Anita
Published: January 2011

CONTEXT: Partner violence is associated with STDs among female adolescents, but the mechanisms underlying this association remain unclear. Sexually coercive and deceptive behaviors of male partners that increase female STD risk may be factors in this relationship.

METHODS: A sample of 356 females aged 14–20 who attended adolescent health clinics in Greater Boston between April and December 2006 were assessed for physical and sexual violence perpetrated by male partners and for exposure to sexual risk factors. Adjusted logistic regression models were used to examine the associations between intimate partner violence and standard sexual risk behaviors (e.g., multiple partnerships) and coercive or deceptive sexual risk factors (e.g., coerced condom nonuse).

RESULTS: More than two‐fifths of the sample had experienced intimate partner violence. In adjusted analyses, adolescents reporting intimate partner violence were more likely than others to report standard sexual risk behaviors—multiple partners, anal sex and unprotected anal sex (odds ratios, 1.7–2.2). They also were more likely to report coercive or deceptive sexual risk factors—partner sexual infidelity, fear of requesting condom use, negative consequences of condom request, and coerced condom nonuse (2.9–5.3).

CONCLUSION: The high prevalence of intimate partner violence against young women attending adolescent clinics strongly indicates the need to target this population for abuse‐related interventions. This need is underlined by the observed association between partner violence and sexual risk involving coercion or deception by male partners. Clinic‐based STD and pregnancy prevention efforts should include assessment of sexual risk factors that are beyond the control of young women, particularly for those experiencing abuse.
Polycrystalline Modeling of the Effect of Texture and Dislocation Microstructure on Anisotropic Thermal Creep of Pressurized Zr-2.5Nb Tubes
Authors: Li W. , Holt R. A. , Tracy S.
Published: January 2011

We have investigated the thermal creep of cold-worked Zr-2.5Nb tubes for a range of textures and stress states. The creep tests were performed on internally pressurized thin-wall standard (ratio of axial and transverse stress R≈0.5) and end-loaded (ratio of axial and transverse stress, 0.25<R<0.75) capsules 10 mm in diameter×40 mm long×0.5 mm wall-thickness at a stress of 300 MPa at 350°C where dislocation creep is the dominant operating mechanism. The tests showed an obvious correlation of anisotropic creep with the texture under different stress states. A self-consistent visco-plastic polycrystalline model based solely upon crystallographic texture showed a poor correlation with experimental results for radial basal textures, similar to that found previously for in-reactor creep. Hence texture alone is not sufficient to accurately predict the creep anisotropy. A modified self-consistent model is introduced to take into account different pre-existing anisotropic dislocation distributions (from cold-work) in different crystal orientations. Much better agreement with the experimental creep anisotropy was found, indicating that individual dislocation distributions in grains with different orientations are important in controlling the creep anisotropy. The predicted effect on creep anisotropy of introducing dislocation structures by a radically different strain path is very large.
Necessity is the Mother of Invention: Reconstructing Missing Sensory Information in Multiple, Concurrent Reference Frames for Eye–Hand Coordination
Authors: Tagliabue Michele , McIntyre Joseph
Published: January 2011

When aligning the hand to grasp an object, the CNS combines multiple sensory inputs encoded in multiple reference frames. Previous studies suggest that when a direct comparison of target and hand is possible via a single sensory modality, the CNS avoids performing unnecessary coordinate transformations that add noise. But when target and hand do not share a common sensory modality (e.g., aligning the unseen hand to a visual target), at least one coordinate transformation is required. Similarly, body movements may occur between target acquisition and manual response, requiring that egocentric target information be updated or transformed to external reference frames to compensate. Here, we asked subjects to align the hand to an external target, where the target could be presented visually or kinesthetically and feedback about the hand was visual, kinesthetic, or both. We used a novel technique of imposing conflict between external visual and gravito-kinesthetic reference frames when subjects tilted the head during an instructed memory delay. By comparing experimental results to analytical models based on principles of maximum likelihood, we showed that multiple transformations above the strict minimum may be performed, but only if the task precludes a unimodal comparison of egocentric target and hand information. Thus, for cross-modal tasks, or when head movements are involved, the CNS creates and uses both kinesthetic and visual representations. We conclude that the necessity of producing at least one coordinate transformation activates multiple, concurrent internal representations, the functionality of which depends on the alignment of the head with respect to gravity.
Vascularization of Cytochrome Oxidase-Rich Blobs in the Primary Visual Cortex of Squirrel and Macaque Monkeys
Authors: Keller Anna Lena , Schüz Almut , Logothetis Nikos K. , Weber Bruno
Published: January 2011

The close correlation between energy supply by blood vessels and energy consumption by cellular processes in the brain is the basis of blood flow-related functional imaging techniques. Regional differences in vascular density can be detected using high-resolution functional magnetic resonance imaging. Therefore, inhomogeneities in vascularization might help to identify anatomically distinct areas noninvasivelyin vivo. It was reported previously that cytochrome oxidase-rich blobs in the striate cortex of squirrel monkeys are characterized by a notably higher vascular density (42% higher than interblob regions). However, blobs have so far never been identifiedin vivoon the basis of their vascular density. Here, we analyzed blobs of the primary visual cortex of squirrel monkeys and macaques with respect to the relationship between vascularization and cytochrome oxidase activity. By double staining with cytochrome oxidase enzyme histochemistry to define the blobs and collagen type IV immunohistochemistry to quantify the blood vessels, a close correlation between oxidative metabolism and vascularization was confirmed and quantified in detail. The vascular length density in cytochrome oxidase blobs was on average 4.5% higher than in the interblob regions, a difference almost one order of magnitude smaller than previously reported. Thus, the vascular density that is closely associated with local average metabolic activity is a structural equivalent of cerebral metabolism and blood flow. However, the quantitative differences in vascularization between blob and interblob regions are small and below the detectability threshold of the noninvasive hemodynamic imaging methods of today.
Activation of TREK Currents by the Neuroprotective Agent Riluzole in Mouse Sympathetic Neurons
Authors: Cadaveira-Mosquera Alba , Ribeiro Sandro J. , Reboreda Antonio , Pérez Montse , Lamas J. Antonio
Published: January 2011

Background K2P channels play a key role in stabilizing the resting membrane potential, thereby modulating cell excitability in the central and peripheral somatic nervous system. Whole-cell experiments revealed a riluzole-activated current (IRIL), transported by potassium, in mouse superior cervical ganglion (mSCG) neurons. The activation of this current by riluzole, linoleic acid, membrane stretch, and internal acidification, its open rectification and insensitivity to most classic potassium channel blockers, indicated thatIRILflows through channels of the TREK [two-pore domain weak inwardly rectifying K channel (TWIK)-related K channel] subfamily. Whole-ganglia and single-cell reverse transcription-PCR demonstrated the presence of TREK-1, TREK-2, and TRAAK (TWIK-related arachidonic acid-activated K+channel) mRNA, and the expression of these three proteins was confirmed by immunocytochemistry in mSCG neurons.IRILwas enhanced by zinc, inhibited by barium and fluoxetine, but unaffected by quinine and ruthenium red, strongly suggesting that it was carried through TREK-1/2 channels. Consistently, a channel with properties identical with the heterologously expressed TREK-2 was recorded in most (75%) cell-attached patches. These results provide the first evidence for the expression of K2P channels in the mammalian autonomic nervous system, and they extend the impact of these channels to the entire nervous system.
CD45 Deficiency Drives Amyloid-β Peptide Oligomers and Neuronal Loss in Alzheimer's Disease Mice
Authors: Zhu Yuyan , Hou Huayan , Rezai-Zadeh Kavon , Giunta Brian , Ruscin Amanda , Gemma Carmelina , Jin JingJi , Dragicevic Natasa , Bradshaw Patrick , Rasool Suhail , Glabe Charles G. , Ehrhart Jared , Bickford Paula , Mori Takashi , Obregon Demian , Town Terrence , Tan Jun
Published: January 2011

Converging lines of evidence indicate dysregulation of the key immunoregulatory molecule CD45 (also known as leukocyte common antigen) in Alzheimer's disease (AD). We report that transgenic mice overproducing amyloid-β peptide (Aβ) but deficient in CD45 (PSAPP/CD45−/−mice) faithfully recapitulate AD neuropathology. Specifically, we find increased abundance of cerebral intracellular and extracellular soluble oligomeric and insoluble Aβ, decreased plasma soluble Aβ, increased abundance of microglial neurotoxic cytokines tumor necrosis factor-α and interleukin-1β, and neuronal loss inPSAPP/CD45−/−mice compared with CD45-sufficient PSAPP littermates (bearing mutant human amyloid precursor protein and mutant human presenilin-1 transgenes). After CD45 ablation,in vitroandin vivostudies demonstrate an anti-Aβ phagocytic but proinflammatory microglial phenotype. This form of microglial activation occurs with elevated Aβ oligomers and neural injury and loss as determined by decreased ratio of anti-apoptotic Bcl-xL to proapoptotic Bax, increased activated caspase-3, mitochondrial dysfunction, and loss of cortical neurons inPSAPP/CD45−/−mice. These data show that deficiency in CD45 activity leads to brain accumulation of neurotoxic Aβ oligomers and validate CD45-mediated microglial clearance of oligomeric Aβ as a novel AD therapeutic target.
Differential Electrophysiological Changes in Striatal Output Neurons in Huntington's Disease
Authors: André Véronique M. , Cepeda Carlos , Fisher Yvette E. , Huynh My , Bardakjian Nora , Singh Sumedha , Yang X. William , Levine Michael S.
Published: January 2011

There is considerable evidence that alterations in striatal medium-sized spiny neurons (MSSNs) giving rise to the direct (D1 receptor-expressing) and indirect (D2 receptor-expressing) pathways differentially contribute to the phenotype of Huntington's disease (HD). To determine how each subpopulation of MSSN is functionally affected, we examined spontaneous excitatory postsynaptic currents (sEPSCs) and dopamine (DA) modulation in two HD mouse models, the YAC128 and the BACHD (a bacterial-artificial chromosome). These mice also expressed enhanced green fluorescent protein (EGFP) under the control of the promoter for either DA D1 or D2 receptors to identify neurons. In early symptomatic YAC128 and BACHD mice, glutamate transmission was increased in both D1 and D2 MSSNs, but in different ways. D1 cells displayed increased sEPSC frequencies and decreased paired-pulse ratios (PPRs) while D2 cells displayed larger evoked glutamate currents but no change in sEPSC frequencies or PPRs. D1 receptor modulation of sEPSCs was absent in D1-YAC128 cells at the early symptomatic stage but was restored by treating the slices with tetrabenazine. In contrast, in fully symptomatic YAC128 mice, glutamate transmission was decreased specifically in D1 cells, and D1 receptor modulation was normal in D1-YAC128 cells. Behaviorally, early symptomatic mice showed increased stereotypies that were decreased by tetrabenazine treatment. Together, these studies support differential imbalances in glutamate and DA transmission in direct and indirect pathway MSSNs. Stereotypic behavior at an early stage could be explained by increased glutamate activity and DA tone in direct pathway neurons, whereas hypokinesia at later stages could result from reduced input onto these neurons.
Analysis of Development of Direction Selectivity in Retinotectum by a Neural Circuit Model with Spike Timing-Dependent Plasticity
Authors: Honda Minoru , Urakubo Hidetoshi , Tanaka Keiko , Kuroda Shinya
Published: January 2011

The development of direction selectivity in the visual system depends on visual experience. In the developingXenopusretinotectal system, tectal neurons (TNs) become direction selective through spike timing-dependent plasticity (STDP) after repetitive retinal exposure to a moving bar in a specific direction. We investigated the mechanism responsible for the development of direction selectivity in theXenopusretinotectal system using a neural circuit model with STDP. In this retinotectal circuit model, a moving bar stimulated the retinal ganglion cells (RGCs), which provided feedforward excitation to the TNs and interneurons (INs). The INs provided delayed feedforward inhibition to the TNs. The TNs also received feedback excitation from neighboring TNs. As a synaptic learning rule, a molecular STDP model was used for synapses between the RGCs and TNs. The retinotectal circuit model reproduced experimentally observed features of the development of direction selectivity, such as increase in input to the TN. The peak of feedforward excitation from RGCs to TNs shifted earlier as a result of STDP. Together with the delayed feedforward inhibition, a stronger earlier transient feedforward signal was generated, which exceeded the threshold of the feedback excitation from the neighboring TNs and resulted in amplification of input to the TN. The suppression of the delayed feedforward inhibition resulted in the development of orientation selectivity rather than direction selectivity, indicating the pivotal role of the delayed feedforward inhibition in direction selectivity. We propose a mechanism for the development of direction selectivity involving a delayed feedforward inhibition with STDP and the amplification of feedback excitation.
Functional Connectome of the Striatal Medium Spiny Neuron
Authors: Chuhma Nao , Tanaka Kenji F. , Hen René , Rayport Stephen
Published: January 2011

Dopamine system disorders ranging from movement disorders to addiction and schizophrenia involve striatal medium spiny neurons (MSNs), yet their functional connectivity has been difficult to determine comprehensively. We generated a mouse with conditional channelrhodopsin-2 expression restricted to medium spiny neurons and assessed the specificity and strength of their intrinsic connections in the striatum and their projections to the globus pallidus and the substantia nigra. In the striatum, medium spiny neurons connected with other MSNs and tonically active cholinergic interneurons, but not with fast-spiking GABA interneurons. In the globus pallidus, medium spiny neurons connected strongly with one class of electrophysiologically identified neurons, but weakly with the other. In the substantia nigra, medium spiny neurons connected strongly with GABA, but not with dopamine neurons. Projections to the globus pallidus showed solely D2-mediated presynaptic inhibition, whereas projections to the substantia nigra showed solely D1-mediated presynaptic facilitation. This optogenetic approach defines the functional connectome of the striatal medium spiny neuron.
Cytoplasmic Linker Proteins Regulate Neuronal Polarization through Microtubule and Growth Cone Dynamics
Authors: Neukirchen Dorothee , Bradke Frank
Published: January 2011

Axon formation is a hallmark of initial neuronal polarization. This process is thought to be regulated by enhanced microtubule stability in the subsequent axon and changes in actin dynamics in the future axonal growth cone. Here, we show that the microtubule end-binding proteins cytoplasmic linker protein (CLIP)-115 and CLIP-170 were enriched in the axonal growth cone and extended into the actin-rich domain of the growth cone. CLIPs were necessary for axon formation and sufficient to induce an axon. The regulation of axonal microtubule stabilization by CLIPs enabled the protrusion of microtubules into the leading edge of the axonal growth cone. Moreover, CLIPs positively regulated growth cone dynamics and restrained actin arc formation, which was necessary for axon growth. In fact, in neurons without CLIP activity, axon formation was restored by actin destabilization or myosin II inhibition. Together, our data suggest that CLIPs enable neuronal polarization by controlling the stabilization of microtubules and growth cone dynamics.
Tuning the Period of the Mammalian Circadian Clock: Additive and Independent Effects of CK1εTauand Fbxl3AfhMutations on Mouse Circadian Behavior and Molecular Pacemaking
Authors: Maywood Elizabeth S. , Chesham Johanna E. , Meng Qing-Jun , Nolan Patrick M. , Loudon Andrew S. I. , Hastings Michael H.
Published: January 2011

Circadian pacemaking in the suprachiasmatic nucleus (SCN) revolves around a transcriptional/posttranslational feedback loop in which period (Per) and cryptochrome (Cry) genes are negatively regulated by their protein products. Genetically specified differences in this oscillator underlie sleep and metabolic disorders, and dictate diurnal/nocturnal preference. A critical goal, therefore, is to identify mechanisms that generate circadian phenotypic diversity, through both single gene effects and gene interactions. The individual stabilities of PER or CRY proteins determine pacemaker period, and PER/CRY complexes have been proposed to afford mutual stabilization, although how PER and CRY proteins with contrasting stabilities interact is unknown. We therefore examined interactions between two mutations in male mice:Fbxl3Afh, which lengthens period by stabilizing CRY, andCsnk1εtm1Asil(CK1εTau), which destabilizes PER, thereby accelerating the clock. By intercrossing these mutants, we show that the stabilities of CRY and PER are independently regulated, contrary to the expectation of mutual stabilization. Segregation of wild-type and mutant alleles generated a spectrum of periods for rest-activity behavior and SCN bioluminescence rhythms. The mutations exerted independent, additive effects on circadian period, biased toward shorter periods determined byCK1εTau. Notably,Fbxl3Afhextended the duration of the nadir of the PER2-driven bioluminescence rhythm butCK1εTaureversed this, indicating that despite maintained CRY expression,CK1εTautruncated the interval of negative feedback. These results argue for independent, additive biochemical actions of PER and CRY in circadian control, and complement genome-wide epistatic analyses, seeking to decipher the multigenic control of circadian pacemaking.
Concerted Action of CB1 Cannabinoid Receptor and Deleted in Colorectal Cancer in Axon Guidance
Authors: Argaw Anteneh , Duff Gabriel , Zabouri Nawal , Cécyre Bruno , Chainé Natacha , Cherif Hosni , Tea Nicolas , Lutz Beat , Ptito Maurice , Bouchard Jean-François
Published: January 2011

Endocannabinoids (eCBs) are retrograde neurotransmitters that modulate the function of many types of synapses. The presence of eCBs, their CB1 receptor (CB1R), and metabolizing enzymes at embryonic and early postnatal periods have been linked to developmental processes such as neuronal proliferation, differentiation, and migration, axon guidance, and synaptogenesis. Here, we demonstrate the presence of a functional eCB system in the developing visual system and the role of CB1R during axon growth and retinothalamic development. Pharmacological treatment of retinal explants and primary cortical neuron cultures with ACEA, a selective CB1R agonist, induced a collapse of the growth cone (GC). Furthermore the application of AM251, a CB1R inverse agonist, to the neuronal cultures increased the surface area of GC.In vivo, intraocular injection of ACEA diminished retinal projection growth, while AM251 promoted growth and caused aberrant projections. In addition, compared with their wild-type littermates, CB1R-deficient adult mice revealed a lower level of eye-specific segregation of retinal projections in the dorsal lateral geniculate nucleus. Finally, we found that pharmacological modulation of CB1R affected the trafficking of Deleted in colorectal cancer (DCC) receptor to the plasma membrane in a PKA-dependent manner. Moreover, pharmacological inhibition or genetic inactivation of DCC abolished the CB1R-induced reorganization of the GC. Overall, these findings establish a mechanism by which the CB1R influences GC behavior and nervous system development in concerted action with DCC.
Crystal Structure of the Amyloid-β p3 Fragment Provides a Model for Oligomer Formation in Alzheimer's Disease
Authors: Streltsov Victor A. , Varghese Joseph N. , Masters Colin L. , Nuttall Stewart D.
Published: January 2011

Alzheimer's disease is a progressive neurodegenerative disorder associated with the presence of amyloid-β (Aβ) peptide fibrillar plaques in the brain. However, current evidence suggests that soluble nonfibrillar Aβ oligomers may be the major drivers of Aβ-mediated synaptic dysfunction. Structural information on these Aβ species has been very limited because of their noncrystalline and unstable nature. Here, we describe a crystal structure of amylogenic residues 18–41 of the Aβ peptide (equivalent to the p3 α/γ-secretase fragment of amyloid precursor protein) presented within the CDR3 loop region of a shark Ig new antigen receptor (IgNAR) single variable domain antibody. The predominant oligomeric species is a tightly associated Aβ dimer, with paired dimers forming a tetramer in the crystal caged within four IgNAR domains, preventing uncontrolled amyloid formation. Our structure correlates with independently observed features of small nonfibrillar Aβ oligomers and reveals conserved elements consistent with residues and motifs predicted as critical in Aβ folding and oligomerization, thus potentially providing a model system for nonfibrillar oligomer formation in Alzheimer's disease.
NrCAM Deletion Causes Topographic Mistargeting of Thalamocortical Axons to the Visual Cortex and Disrupts Visual Acuity
Authors: Demyanenko Galina P. , Riday Thorfinn T. , Tran Tracy S. , Dalal Jasbir , Darnell Eli P. , Brennaman Leann H. , Sakurai Takeshi , Grumet Martin , Philpot Benjamin D. , Maness Patricia F.
Published: January 2011

NrCAM is a neural cell adhesion molecule of the L1 family that has been linked to autism spectrum disorders, a disease spectrum in which abnormal thalamocortical connectivity may contribute to visual processing defects. Here we show that NrCAM interaction with neuropilin-2 (Npn-2) is critical for semaphorin 3F (Sema3F)-induced guidance of thalamocortical axon subpopulations at the ventral telencephalon (VTe), an intermediate target for thalamic axon sorting. Genetic deletion of NrCAM or Npn-2 caused contingents of embryonic thalamic axons to misproject caudally in the VTe. The resultant thalamocortical map of NrCAM-null mutants showed striking mistargeting of motor and somatosensory thalamic axon contingents to the primary visual cortex, but retinogeniculate targeting and segregation were normal. NrCAM formed a molecular complex with Npn-2 in brain and neural cells, and was required for Sema3F-induced growth cone collapse in thalamic neuron cultures, consistent with a vital function for NrCAM in Sema3F-induced axon repulsion. NrCAM-null mice displayed reduced responses to visual evoked potentials recorded from layer IV in the binocular zone of primary visual cortex (V1), particularly when evoked from the ipsilateral eye, indicating abnormal visual acuity and ocularity. These results demonstrate that NrCAM is required for normal maturation of cortical visual acuity, and suggest that the aberrant projection of thalamic motor and somatosensory axons to the visual cortex in NrCAM-null mutant mice impairs cortical functions.