Phospho-dependent modulation of potassium chloride co-transporter KCC2

The neuronal-specific potassium chloride co-transporter 2, KCC2, is a major chloride extruder in brain. The expression of KCC2 during neuronal development is fundamental to the switch of GABAergic response from excitatory to inhibitory. Malfunction of KCC2 can cause impairment of chloride homeostasis in neurons and is implicated in neurological disorders such as epilepsy. To date the role of protein phosphorylation in the regulation of KCC2 remains elusive. In this thesis, direct phosphorylation of KCC2 by PKC and Src tyrosine kinase was shown in vitro and in cultured neurons using the radioactive isotope 32P. Single mutation of serine residue at position 940 in the intracellular domain of KCC2 (Ser940) to alanine (S940A) blocked the phosphorylation of KCC2 under PKC activation. However, tyrosine phosphorylation of KCC2 was shown to not affect Tyr1087, the putative tyrosine kinase phosphorylation site. To better understand phosphorylation of KCC2 at Ser940, a phospho-specific antibody against this residue - namely p-S940 - was developed. Interestingly, agents inhibiting PKC and phosphatases altered signal of p-S940, indicating involvement of PKC, phosphatase-1 (PP1) and phosphatase-2A (PP2A) in the regulation of Ser940 phosphorylation. In an in vitro method using p-S940, it was shown that PP1 and PP2A dephosphorylated KCC2

Perception Analysis of Industrialized Building System (IBS) Implementation for G7 Contractors in Kuching, Sarawak

Industrialized Building System (IBS) is one of the initiatives underpinning the green construction zeitgeist. A myriad of advantages can be associated with adopting IBS in construction, including inter alia, improved construction quality and productivity, minimisation of construction waste, optimisation of construction materials on-site, enhanced environmental sustainability, and many others. In spite of these advantageous propositions, there is exist a gap in the exposure towards IBS construction methods, particularly in the city of Kuching, Sarawak, as compared to more familiar conventional methods. Thus, the purpose of this study is to identify the issues and challenges experienced by contractors in their IBS endeavour as well as to propose a framework of solution. Moreover, this study investigated the impact of IBS adoption by G7 contractors registered with the Construction Industry Development Board (CIDB) of Sarawak. Data of this study was collected via questionnaires distributed to the G7 contractors and subsequently analysed using descriptive and mean analysis. Results obtained from the study suggested that IBS construction method enhances the efficiency of construction for speedier completions, which recorded the highest ranking. Conversely, lowering the costs of construction through optimisation of materials registered the lowest ranking, suggesting that contractors do not necessarily perceive IBS as having a cost-saving ability. This study showed that IBS helps to improve the efficiency of the construction process. However, respondents were still uncertain that adopting IBS can reduce costs. This corresponds to the finding in which the most significant challenge perceived by the contractors was related to cost. This suggested a lack of integration between the different stakeholders, especially during the design stage, often resulting in the need for redesign works that required additional costs when IBS is to be adopted. In this regard, it was not a surprise to find that “promotions” obtained the top ranking as a solution in overcoming the IBS challenges. Hence, support from both the government and the private sector needs to be garnered and diligently promoted, so that the adoption of IBS in the Sarawak construction industry can be properly enhanced

Tunneling gap of laterally separated quantum Hall states

We use a method of matched asymptotics to determine the energy gap of two counter-propagating, strongly interacting, quantum Hall edge states. The microscopic edge state dispersion and Coulomb interactions are used to precisely constrain the short-distance behavior of an integrable field theory, which then determines the low energy spectrum. We discuss the relationship of our results to the tunneling measurements of Kang et al., Nature 403, 59 (2000).Comment: 4 pages, 1 figur

Coulomb gap in one-dimensional disordered electronic systems

We study a one-dimensional system of spinless electrons in the presence of a long-range Coulomb interaction (LRCI) and a random chemical potential at each site. We first present a Tomonaga-Luttinger liquid (TLL) description of the system. We use the bosonization technique followed by the replica trick to average over the quenched randomness. An expression for the localization length of the system is then obtained using the renormalization group method and also a physical argument. We then find the density of states for different values of the energy; we get different expressions depending on whether the energy is larger than or smaller than the inverse of the localization length. We work in the limit of weak disorder where the localization length is very large; at that length scale, the LRCI has the effect of reducing the interaction parameter K of the TLL to a value much smaller than the noninteracting value of unity.Comment: Revtex, 6 pages, no figures; discussions have been expanded in several place

The mechanism of striation formation in plasma display panels

Despite the high pressure employed in plasma display panels, the energy balance of low-energy electrons is found to be dominated by inelastic collisions, and the resulting nonlocal electron kinetics plays a key role in the striation formation. Surface charge accumulation on the anode dielectric, however, is also needed for striations to form. It is the combined effect of surface charges and nonlocal electron kinetics that results in the striation formation in plasma display panel cells. Two-dimensional fluid simulations, which assume local electron kinetics, and two-dimensional particle-in-cell Monte Carlo collision simulations with a bare conducting anode show that striations do not form if either the nonlocal electron kinetics or the surface charge accumulation is not considered

Stress-Minimizing Orthogonal Layout of Data Flow Diagrams with Ports

We present a fundamentally different approach to orthogonal layout of data flow diagrams with ports. This is based on extending constrained stress majorization to cater for ports and flow layout. Because we are minimizing stress we are able to better display global structure, as measured by several criteria such as stress, edge-length variance, and aspect ratio. Compared to the layered approach, our layouts tend to exhibit symmetries, and eliminate inter-layer whitespace, making the diagrams more compact

Multidimensional adaptive P-splines with application to neurons' activity studies

The receptive field (RF) of a visual neuron is the region of the space that elicits neuronal responses. It can be mapped using different techniques that allow inferring its spatial and temporal properties. Raw RF maps (RFmaps) are usually noisy, making it difficult to obtain and study important features of the RF. A possible solution is to smooth them using P-splines. Yet, raw RFmaps are characterized by sharp transitions in both space and time. Their analysis thus asks for spatiotemporal adaptive P-spline models, where smoothness can be locally adapted to the data. However, the literature lacks proposals for adaptive P-splines in more than two dimensions. Furthermore, the extra flexibility afforded by adaptive P-spline models is obtained at the cost of a high computational burden, especially in a multidimensional setting. To fill these gaps, this work presents a novel anisotropic locally adaptive P-spline model in two (e.g., space) and three (space and time) dimensions. Estimation is based on the recently proposed SOP (Separation of Overlapping Precision matrices) method, which provides the speed we look for. Besides the spatiotemporal analysis of the neuronal activity data that motivated this work, the practical performance of the proposal is evaluated through simulations, and comparisons with alternative methods are reported.</p

Multidimensional adaptive P-splines with application to neurons' activity studies

The receptive field (RF) of a visual neuron is the region of the space that elicits neuronal responses. It can be mapped using different techniques that allow inferring its spatial and temporal properties. Raw RF maps (RFmaps) are usually noisy, making it difficult to obtain and study important features of the RF. A possible solution is to smooth them using P-splines. Yet, raw RFmaps are characterized by sharp transitions in both space and time. Their analysis thus asks for spatiotemporal adaptive P-spline models, where smoothness can be locally adapted to the data. However, the literature lacks proposals for adaptive P-splines in more than two dimensions. Furthermore, the extra flexibility afforded by adaptive P-spline models is obtained at the cost of a high computational burden, especially in a multidimensional setting. To fill these gaps, this work presents a novel anisotropic locally adaptive P-spline model in two (e.g., space) and three (space and time) dimensions. Estimation is based on the recently proposed SOP (Separation of Overlapping Precision matrices) method, which provides the speed we look for. Besides the spatiotemporal analysis of the neuronal activity data that motivated this work, the practical performance of the proposal is evaluated through simulations, and comparisons with alternative methods are reported.Agencia Estatal de Investigación | Ref. MTM2017-82379-RAgencia Estatal de Investigación | Ref. PID2019-104901RB-I00Agencia Estatal de Investigación | Ref. RYC2019-027534-IInstituto de Salud Carlos III | Ref. RD16/0008/0003Xunta de Galicia | Ref. ED431G 2019/02Agencia Estatal de Investigación | Ref. SEV-2017-0718Eusko Jaurlaritza | Ref. BERC 2018-2021Universidade de Vigo/CISU

Highly reproducible alkali metal doping system for organic crystals through enhanced diffusion of alkali metal by secondary thermal activation

In this paper, we report an efficient alkali metal doping system for organic single crystals. Our system employs an enhanced diffusion method for the introduction of alkali metal into organic single crystals by controlling the sample temperature to induce secondary thermal activation. Using this system, we achieved intercalation of potassium into picene single crystals with closed packed crystal structures. Using optical microscopy and Raman spectroscopy, we confirmed that the resulting samples were uniformly doped and became K2picene single crystal, while only parts of the crystal are doped and transformed into K2picene without secondary thermal activation. Moreover, using a customized electrical measurement system, the insulator-to-semiconductor transition of picene single crystals upon doping was confirmed by in situ electrical conductivity and ex situ temperature-dependent resistivity measurements. X-ray diffraction studies showed that potassium atoms were intercalated between molecular layers of picene, and doped samples did not show any KH- nor KOH-related peaks, indicating that picene molecules are retained without structural decomposition. During recent decades, tremendous efforts have been exerted to develop high-performance organic semiconductors and superconductors, whereas as little attention has been devoted to doped organic crystals. Our method will enable efficient alkali metal doping of organic crystals and will be a resource for future systematic studies on the electrical property changes of these organic crystals upon doping. © 2018 The Author(s