1,433 research outputs found

    Local and regional heterogeneity underlying hippocampal modulation of cognition and mood.

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    While the hippocampus has been classically studied for its role in learning and memory, there is significant support for a role of the HPC in regulating emotional behavior. Emerging research suggests these functions may be segregated along the dorsoventral axis of the HPC. In addition to this regional heterogeneity, within the HPC, the dentate gyrus is one of two areas in the adult brain where stem cells continuously give rise to new neurons. This process can influence and be modulated by the emotional state of the animal, suggesting that adult neurogenesis within the DG may contribute to psychiatric disorders and cognitive abilities. Yet, the exact mechanism by which these newborn neurons influence behavior remains unknown. Here, we will examine the contribution of hippocampal neurogenesis to the output of the HPC, and suggest that the role of neurogenesis may vary along the DV axis. Next, we will review literature indicating that anatomical connectivity varies along the DV axis of the HPC, and that this underlies the functional segregation along this axis. This analysis will allow us to synthesize novel hypotheses for the differential contribution of the HPC to cognition and mood

    Direct recovering of surface structure characterized by an Nth degree polynomial equation using the UOFF approach

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    There are two different approaches for estimation of structure and/or motion of objects in the computer vision community today. One is the feature correspondence method, and the other is the optical flow method [1]. There are many difficulties and limitations encountered with the feature correspondence method, while the optical flow method is more feasible, but requires a substantial amount of extra calculations if the optical flow is to be computed as an intermediate step. Direct methods have been developed [2-4], that use the optical flow approach, but avoid computing the full optical flow field as an intermediate step for recovering structure and motion. The unified optical flow field theory was recently established in [5]. It is an extension of the optical flow (UOFF) [1] to stereo imagery. Based on the UOFF, a direct method is developed to reconstruct an Alpha shape surface structure characterized by an third degree polynomial equation, and a Sphere surface characterized by a second degree polynomial [6]. This thesis work uses the methods developed in [5,6], to reconstruct the third degree polynomial describing a surface. The main difference from the simulation results obtained in [6], is that in this case, one of the two surfaces tested is a third order, unbounded surface, and that tbe image gradients are computed directly from the image data, with no prior knowledge of the surface gray function distribution. Another important difference is that the gray levels of the surface are quantized in this work; i.e., the computations are done using integer image data, not the continuous gray levels as in [6]. These differences contribute to proving that the UOFF technique can be used in a practical manner, and with good results. Further discussions of the contributions of this work are included in the last chapter

    Analysis of Shear Wall with Openings Using Solid65 Element

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    The use of shear wall-buildings is quite common in some earthquake prone regions. During seismic excitation, they contribute in absorbing moments and shear forces and reduce torsional response. Usually, architectural design leads to the existence of doors and windows within shear walls. Previous researches on the behavior of shear walls with openings assumed elastic analysis utilizing shell and brick elements. The present work adopts nonlinear finite element analysis using solid65 element. The analysis comprises both material and geometric nonlinearities. Solid65 element models the nonlinear response of concrete material based on a constitutive model for the triaxial behavior of concrete after Williams and Warnke. Five shear wall models with different opening sizes are analyzed. A sixth model of a solid shear wall is also presented to compare the analysis results. The paper studies the effect of the size of the openings on the behavior of the reinforced concrete shear walls. The study indicates that openings of small dimensions yield minor effects on the response of shear walls with respect to both normal stresses along the base level of shear walls and maximum drift. Cantilever behavior similar to that of a solid shear wall takes place and analogous to that of coupled shear walls. On the other hand, when openings are large enough, shear walls behave as connected shear walls, exhibiting frame action behavior

    Development of Reduced Chemical Kinetic Models for the Numerical Simulation of Combustion and Emissions Behavior of Representative Conventional and Bio-derived Fuels

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    The study addresses two of the main challenges facing combustion modeling for transportation fuels: simultaneous simulation of non-related combustion problems and reducing the computational cost of the modeling process itself. To address the first challenge, researchers determine a characteristic flame time from thermal diffusivity and laminar burning velocity. Researchers examine parametric dependence of flame time and ignition delay time on pressure, temperature and equivalence ratio for methane, based on validated chemical kinetic mechanisms. The study reveals flame time and ignition delay time show similar temperature dependence, flame time has stronger dependence on equivalence ratio and weaker dependence on pressure than ignition delay time. The study also establishes a correlation to predict flame time, and subsequently, burning velocity, based on knowledge of the relevant auto ignition time. Differences between methane, propane and ethanol are also explored. Researchers address the second challenge in a chemical kinetic modeling study of the high-temperature ignition behavior of Tetrahydrofuran (THF), a promising second-generation transportation biofuel. The study implements a Stochastic Species Elimination (SSE) reduction approach to develop multiple skeletal versions of a detailed chemical kinetic model of THF from the literature based on ignition delay time simulations at various pressures and temperatures. The developed skeletal versions are combined into a global skeletal model. The study uses ignition delay time simulations using detailed and skeletal models, with good agreement observed at higher temperatures. Next, researchers use sensitivity analysis to identify the most important reactions responsible for the performance of the skeletal model. Finally, they perform reaction rate parameter modification for such reactions in order to improve the agreement of detailed and reduced model predictions with literature experimental ignition data. This work contributes toward improved understanding and modeling of the oxidation kinetics of conventional and bio-derived transportation biofuels, as well as the estimation of laminar burning velocity that can be encountered in turbulent combustion simulations. This would ultimately contribute into the design of cleaner and more efficient transportation systems, and support the testing and adoption of novel fuels as additives and/or replacement to conventional non-renewable fossil fuel

    Intermediate Role of the Criterion of Focus on the Students Benefiting in the Relationship between Adopting the Criterion of Partnership and Resources and Achieving Community Satisfaction in the Palestinian Universities

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    The study aimed at identifying the intermediate role of the criterion of emphasis on students and beneficiaries in the relationship between adopting the criterion of partnership and resources and achieving the satisfaction of the society. The study used the analytical descriptive method. The study was conducted on university leadership in Al-Azhar, Islamic and Al-Aqsa Universities. The sample of the study consisted of (200) individuals, 182 of whom responded, and the questionnaire was used in collecting the data. The study reached a number of results, the most important of which were: The level of adoption by the Palestinian universities of the criterion of partnership and resources came to a large extent. The level of adoption by the Palestinian universities of the criterion of emphasis on the beneficiary students was very high. The criterion of partnership and resources to achieve the satisfaction of the community surrounding the Palestinian universities, the existence of a statistically significant impact of the adoption of the criterion of partnership and resources to strengthen the focus on students benefiting in Palestinian universities, The focus on the students benefiting from the satisfaction of the community surrounding the Palestinian universities, the existence of a statistically significant impact on the adoption of the criterion of partnership and resources to achieve the satisfaction of the community surrounding the Palestinian universities, The study presented a number of recommendations, most important of which are: Increase interest in the resource and partnership criterion through enhancing the university's resources and developing internal and external partnerships to serve the university and the society. Increase the focus on students and beneficiaries by providing an appropriate educational environment and academic programs that meet the needs of the labor market. Through the strengthening of existing community service centers and the establishment of new community centers, strengthening the partnership of industrial companies and promoting scientific research for the benefit of universities and society

    The Availability of the Resource Standard and Partnership as One of the Possibilities of Excellence in Palestinian Universities According to the European Model

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    The study aimed to identify the availability of the resource and partnership standard as one of the possibilities of excellence in Palestinian universities according to the European model. The study used the analytical descriptive method. The study was conducted on the university leadership at Al - Azhar and Islamic Universities, where the study population consisted of (282) individuals. The study sample consisted of (135) individuals, (119) of them responded, and the questionnaire was used in collecting the data. The study has reached a number of results, the most important of which is the existence of a high standard of resources and partnership in the Palestinian public universities operating in the southern governorates. The fields of the resource and partnership criteria were as follows: (79.8%) management of internal and external partnerships; management of technical resources (technology) (76.4%), Buildings, equipment and resources (76%), Finance Management (72.8%). The study presented a number of recommendations, the most important of which is: Increasing the interest of universities in applying the criteria of resources and partnership as one of the criteria of excellence, increasing the interest of universities in managing finance and obtaining funding for their various activities, periodic maintenance of buildings and equipment and ensuring their suitability to the requirements of the educational process

    The role of varicocele sclerotherapy in men with severe oligo-astheno-teratozoospermia

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    The aim of this study was to verify the role of antegrade scrotal sclerotherapy for the treatment of varicoceles in infertile men with severe oligo-astheno-teratozoospermia (OAT). The 59 patients with severe OAT in this study underwent antegrade scrotal sclerotherapy for the treatment of varicoceles. The outcome was assessed in terms of improvement in semen parameters and spontaneous conception rate. Semen parameters and reproductive hormones were evaluated before antegrade sclerotherapy (AS) and 6 months after AS. After an average follow-up time of 34.83.2 months, significant improvement was noted in the mean sperm concentration, motility and morphology in 36 patients (61%). Spontaneous pregnancy occurred in nine couples (15%). Six months after treatment, inhibin B levels were significantly higher (P<0.04), whereas follicle-stimulating hormone (FSH) levels were significantly lower (P<0.001) than before treatment. Antegrade internal spermatic vein sclerotherapy can significantly improve seminal parameters and hormonal parameters in men with severe OAT and may even result in spontaneous pregnancy in couples who would otherwise be candidates for intracytoplasmic sperm injection (ICSI)

    Settlement of a One Floor Building on Soft Clay Beside a Heavy Building

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    A one floor building was founded on a deposit of normally consolidated soft clay. It was constructed to annex an existing three storey high building founded on piles. After construction, tilting and settlements of the Annexe were detected relative to the existing building. Recorded absolute and differential settlements, monitored over a period of five years, were considerably high. It is shown here that this could be caused by the combined effect of high compressibility, confinement of clay layers and variations in pressure distribution below foundations
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