One-Dimensional Population Density Approaches to Recurrently Coupled Networks of Neurons with Noise

Mean-field systems have been previously derived for networks of coupled, two-dimensional, integrate-and-fire neurons such as the Izhikevich, adapting exponential (AdEx) and quartic integrate and fire (QIF), among others. Unfortunately, the mean-field systems have a degree of frequency error and the networks analyzed often do not include noise when there is adaptation. Here, we derive a one-dimensional partial differential equation (PDE) approximation for the marginal voltage density under a first order moment closure for coupled networks of integrate-and-fire neurons with white noise inputs. The PDE has substantially less frequency error than the mean-field system, and provides a great deal more information, at the cost of analytical tractability. The convergence properties of the mean-field system in the low noise limit are elucidated. A novel method for the analysis of the stability of the asynchronous tonic firing solution is also presented and implemented. Unlike previous attempts at stability analysis with these network types, information about the marginal densities of the adaptation variables is used. This method can in principle be applied to other systems with nonlinear partial differential equations.Comment: 26 Pages, 6 Figure

Solid-state dye-sensitized solar cells based on ZnO nanoparticle and nanorod array hybrid photoanodes

The effect of ZnO photoanode morphology on the performance of solid-state dye-sensitized solar cells (DSSCs) is reported. Four different structures of dye-loaded ZnO layers have been fabricated in conjunction with poly(3-hexylthiophene). A significant improvement in device efficiency with ZnO nanorod arrays as photoanodes has been achieved by filling the interstitial voids of the nanorod arrays with ZnO nanoparticles. The overall power conversion efficiency increases from 0.13% for a nanorod-only device to 0.34% for a device with combined nanoparticles and nanorod arrays. The higher device efficiency in solid-state DSSCs with hybrid nanorod/nanoparticle photoanodes is originated from both large surface area provided by nanoparticles for dye adsorption and efficient charge transport provided by the nanorod arrays to reduce the recombinations of photogenerated carriers

If you can't beat 'em, join 'em: Malaysia's accession to the ATS

The request to define consequences of Malaysia‟s 2011 accession to the Antarctic Treaty system has been opened up to a broader discussion of potential consequences. This presentation and report examines four different aspects of this discussion in relation to politics, economics, social and symbolic factors and scientific research undertaken. The section on politics reviews developments from the past and the factors leading to Malaysia‟s accession to the ATS. The section on economics analyses overall monetary support and the value of decisions around accession, such as entry and exit costs. Social values in relation to environmentalism are discussed, as are the politics of inclusion and exclusion to decisionmaking processes. An overview of Malaysian Antarctic science is given alongside a discussion of Malaysia‟s consistent interest in resources. Indications for future developments within Malaysia and their relationship to working in Antarctica, are discussed

Characterization of rainbow trout (Oncorhynchus mykiss) and fathead minnow (Pimephales promelas) cell lines as models to study pulp and paper effluent effects in fish

The effects of aquatic toxicants on fish growth and development have been well-documented, in contrast to the changes in gene expression that necessarily precede them. Many of these toxicants are exogenous compounds that possess the ability to mimic steroid hormones or inhibit normal endocrine functions, which are known as endocrine disrupting compounds (EDCs). The Law laboratory previously obtained mRNA expression data indicating that exposure to aquatic effluents from a combined news/kraft pulp and paper mill changed the expression of genes associated with EDC exposure in the livers of fathead minnows (Pimephales promelas). Societal desire to reduce the use of animals in toxicity testing has encouraged the development and use of in vitro systems, including vertebrate cell models. In this study, the gene expression of the rainbow trout (Oncorhynchus mykiss) liver cell line RTL-W1 and the fathead minnow liver cell line FHM-L was examined following effluent exposure. In the RTL-W1 and FHM-L cell lines, 24 h exposure to effluents was sufficient for assessing changes in gene expression, with maximum changes observed between 4 and 6 h after exposure. Both cell lines showed upregulation of the estrogenic and androgenic-related genes, but this upregulation did not follow any consistent pattern in any of the effluent treatments. However, both lines were responsive to toxic compounds in the effluents in a time-dependent fashion, as indicated by the induction of cytochrome P450 1A (CYP1A). The expression of CYP1lA was gradually up-regulated over time, peaking between 4 and 6 h after exposure and declining thereafter. Secondary treatment effectively removed toxic compounds from the effluent, as demonstrated by the decrease in fold induction of CYP1A mRNA levels after 6 h of exposure to combined mill outfall effluent compared to that of cells exposed to untreated and secondary treated kraft effluents This work, along with subsequent correlation analysis of gene expression in cell lines to that in the parent tissue, begins to validate fish cell lines as predictors of changes in aquatic vertebrate health upon exposure to pulp and paper mill effluents and represents a critical step towards the Law lab goal of developing their use as a complement to whole fish life cycle testing that is currently employed in ecotoxicology studies

Explorations of structure and choice in taxing capital gains in New Zealand : tax practitioners' perspectives / Alvin Cheng and Sue Yong

This paper explored the tax practitioners 'views on taxation of capital gains in New Zealand. An 8-page questionnaire was sent to 507 tax practitioners to discuss various tax issues relating to capital gains. The tax issues were taxation on property, rollover relief, indexation and several others. The findings overwhelmingly showed that a capital gains tax (CGT) was not supported by most tax practitioners, A plausible reason for the strong opposition to a CGT by the tax practitioners was attributable to the increased compliance costs and the interpretation surrounding the CGT legislation. The absence of a comprehensive CGT in New Zealand can potentially provide lucrative business opportunities for tax practitioners by advising their clients to convert taxable incomes into tax free capital gains. However there was no empirical evidence to suggest that the loss of tax revenue was due to such tax planning activities. This might be due to the uniqueness of certain types of gains, which would normally be regarded as capital in nature inforeign jurisdictions deemed to be income in New Zealand

Role of MicroRNAs in Human Skeletal Muscle Tissue Engineering In Vitro

<p>The development of a functional tissue-engineered human skeletal muscle model in vitro would provide an excellent platform on which to study the process of myogenesis, various musculoskeletal disease states, and drugs and therapies for muscle toxicity. We developed a protocol to culture human skeletal muscle bundles in a fibrin hydrogel under static conditions capable of exerting active contractions. Additionally, we demonstrated the use of joint miR-133a and miR-696 inhibition for acceleration of muscle differentiation, elevation of active contractile force amplitudes, and increasing Type II myofiber formation in vitro. </p><p>The global hypothesis that motivated this research was that joint inhibition of miR-133a and miR-696 in isolated primary human skeletal myoblasts would lead to accelerated differentiation of tissue-engineered muscle constructs with higher proportion of Type I myofibers and that are capable of significantly increased active contractile forces when subjected to electrical stimulus. The proposed research tested the following specific hypotheses: (1) that HSkM would require different culture conditions than those optimal for C2C12 culture (8% equine serum in differentiation medium on uncoated substrates), as measured by miR expression, (2) that joint inhibition of miR-133a and miR-696 would result in 2D human skeletal muscle cultures with accelerated differentiation and increased Type I muscle fibers compared to control and individual inhibition of each miR, as measured by protein and gene expression, (3) that joint inhibition of miR-133a and miR-696 in this functional 3D human skeletal muscle model would result in active contraction significantly higher than control and individual inhibition by each miR, as measured by isometric force testing, and finally (4) that specific co-culture conditions could support a lamellar co-culture model in 3D of human cord blood-derived endothelial cells (hCB-ECs) and HSkM capable of active contraction, as measured by isometric force testing and immunofluorescence. </p><p>Major results of the dissertation are as follows. Culture conditions of 100 &#956;g/mL growth factor reduced-Matrigel-coated substrates and 2% equine serum in differentiation medium were identified to improve human skeletal myoblast culture, compared to conditions optimal for C2C12 cell culture (uncoated substrates and 8% equine serum media). Liposomal transfection of human skeletal myoblasts with anti-miR-133a and anti-miR-696 led to increased protein presence of sarcomeric alpha-actinin and PGC-1alpha when cells were cultured in 2D for 2 weeks. Presence of mitochondria and distribution of fiber type did not change with miR transfection in a 2D culture. Joint inhibition also resulted in increased PPARGC1A gene expression after 2 weeks of 2D culture. For muscle bundles in 3D, results suggest there exists a myoblast seeding density threshold for the production of functional muscle. 5 x 106 myoblasts/mL did not produce active contraction, while 10 x 106 myoblasts/mL and above were successful. Of the seeding densities studied, 15 x 106 myoblasts/mL resulted in constructs that exerted the highest twitch and tetanus forces. Engineering of human skeletal muscle from transfected cells led to significant increases in force amplitude in joint inhibition compared to negative control (transfection with scrambled miR sequence). Joint inhibition in myoblasts seeded into 3D constructs led to decreased presence of slow myosin heavy chain and increased fast myosin heavy chain. Finally, co-culture of functional human skeletal muscle with human cord blood-derived endothelial cells is possible in 3.3% FBS in DMEM culture conditions, with significant increases in force amplitudes at 48 and 96 hours of co-culture.</p>Dissertatio

Stable smectic phase in suspensions of polydisperse colloidal platelets with identical thickness

6 pages, 6 figures.-- PACS nrs.: 61.30.Eb, 64.70.M−, 81.16.Dn, 82.70.Dd.-- ArXiv pre-print available at: http://arxiv.org/abs/0909.2625We report the nematic and smectic ordering in an aqueous suspension of monolayer α-Zirconium phosphate platelets possessing a high polydispersity in diameter but uniform thickness. We observe an isotropic-nematic transition as the platelet volume fraction increases, followed by the formation of a smectic, an elusive phase that has been rarely seen in discotic liquid crystals. The smectic phase is characterized by x-ray diffraction high-resolution transmission electron microscopy, and optical microscopy. The phase equilibria in this highly polydisperse suspension are rationalized in terms of a theoretical approach based on density-functional theory.Acknowledgment is made to the donors of ACS Petroleum Research Fund (Grant No. 45303-G7) and to the Dow Chemical Co. This work has been partly financed by start-up funds from Texas Engineering Experimental Station and Texas A&M University, by Grants No. NANOFLUID, No. MOSAICO, and No. S-0505/ESP-0299 from Comunidad Autónoma de Madrid (Spain), and Grants No. FIS2005-05243-C02-01, No. FIS2007-65869-C03-01, No. FIS2008-05865-C02-02, and No. FIS2007-65869-C03-C01 from Ministerio de Educación y Ciencia (Spain).Publicad

Advances of Machine Learning in Materials Science: Ideas and Techniques

In this big data era, the use of large dataset in conjunction with machine learning (ML) has been increasingly popular in both industry and academia. In recent times, the field of materials science is also undergoing a big data revolution, with large database and repositories appearing everywhere. Traditionally, materials science is a trial-and-error field, in both the computational and experimental departments. With the advent of machine learning-based techniques, there has been a paradigm shift: materials can now be screened quickly using ML models and even generated based on materials with similar properties; ML has also quietly infiltrated many sub-disciplinary under materials science. However, ML remains relatively new to the field and is expanding its wing quickly. There are a plethora of readily-available big data architectures and abundance of ML models and software; The call to integrate all these elements in a comprehensive research procedure is becoming an important direction of material science research. In this review, we attempt to provide an introduction and reference of ML to materials scientists, covering as much as possible the commonly used methods and applications, and discussing the future possibilities.Comment: 80 pages; 22 figures. To be published in Frontiers of Physics, 18, xxxxx, (2023

The 'questionableness' of things: opening up the conversation

The authors show, through its structure and form, what it means to open up a collaborative conversation. This chapter developed from a number of conversations that took place at the Fourth International Conference on Value and Virtue in Practice-Based Research, the twin themes of which were 'openness' and 'criticality'. These chance and often fleeting conversations focused on ideas explored in the keynote address that Jon delivered at the conference, but spanned out into a wider discussion of the relevance of those ideas within different areas of professional practice

Experimental study of bore-driven swash hydrodynamics on permeable rough slopes

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