The fruit fly Drosophila exhibits robust daily behavioral rhythms, which are driven by a network of circadian pacemaker neurons in the fly brain. The Narrow Abdomen (NA) sodium leak channel functions rhythmically in pacemaker neurons, downstream of the molecular circadian clock, to depolarize resting membrane potential and promote neuronal excitability. Loss of NA function (NA-LOF) strongly disrupts behavioral rhythms, and these behavioral phenotypes are consistent with decreased circadian neuronal activity. Yet despite some recent advances, the mechanisms of NA channel function and regulation in the circadian system are still not well understood. To further elucidate the role of the NA channel in the circadian neuronal network, we generated mutated versions of the NA transgene and assessed the effects of transgene expression in Drosophila circadian pacemaker neurons. Expression of a putative gain of function na transgene (na-GOF) in pacemaker neurons generates unique behavioral phenotypes, suggesting novel effects on neuronal excitability or/and the molecular circadian clock. Next, we investigated how NA-LOF and NA-GOF mutations affect circadian neuron activity through optical recording of fluorescent voltage and calcium sensors expressed in these neurons. Using the fluorescent voltage sensor ArcLight, we find that both NA-LOF and NA-GOF manipulations suppress spontaneous membrane activity in clock neurons in the Drosophila brain. This finding was surprising because the behavioral effects of NA-LOF and NA-GOF are quite distinct. However, the information provided from these spontaneous assays may be a combination of neuronal input and output, and in some cases information is combined from multiple cells. To further characterize the neurophysiological effects of NA channel manipulation, we next paired optical recording with pharmacology in brain explants. Here we find that both wild-type and NA-LOF DN1p clock neurons are strongly depolarized by the acetylcholine receptor agonist nicotine, while NA-GOF neurons show little response. This suggests that NA-GOF expression already depolarizes the membrane potential of these neurons. We also assessed intracellular calcium levels in the DN1p clock cells after applying the inhibitory neurotransmitter glutamate at either morning (peak) or evening (trough) timepoints. We find that wild-type DN1p neurons show a strong decrease in calcium at the peak timepoint and a much smaller decrease at the trough. In contrast, NA-GOF DN1p neurons show decreases at both timepoints, indicating that they have elevated calcium levels (and elevated activity) at the trough time. Through immunostaining, we find that NA-GOF expression alters the core clock protein PERIOD levels in sLNv and LNd neurons during early day. Taken together, this study shows that overexpression of NA-GOF ion channel in Drosophila pacemaker neurons induce unique behavioral phenotypes, likely by depolarizing membrane potential and increasing neuronal activity. We propose that these changes in neuronal activity may feedback to alter the oscillation of molecular clocks. While these transgenic studies have been informative, we have also established gene-editing methods in order to distinguish the effects of gene mutation from effects of overexpression. We have used the CRISPR-Cas9 system to target the endogenous na locus. In the initial step, we replaced na exons 1-13 with a fluorescent marker flanked by attP integration sites. Through subsequent integrase-mediated recombination, we hope to generate a series of na mutations of interest, including gain-of-function mutations, for future studies.

none

Micro-ring devices are based on resonance principle and inherently are wavelength selective. Thus it is an important optical component for WDM based applications. To fully utilize the available capacity in an optical network, large full spectral range (FSR) and narrow passband are key performance targets of ring device designs. In this paper we report the design and analysis results of micro-ring filters with 4000+ GHz FSR and 25 to 50 GHz passband, based on symmetric add-drop filter structure. We optimize the passband shape (using a box-like factor), drop loss coefficient and off-resonance through loss via the coupling coefficients and ring loss parameters.

Gold nanoshells (GNS) are a new class of nanoparticles that can be optically tuned to scatter or absorb light from the near-ultraviolet to near-infrared (NIR) region by varying the core (dielectric silica) /shell (gold) ratio. In addition to spectral tunability, GNS are inert and bioconjugatable making them potential labels for in vivo imaging and therapy of tumors. We report the use of GNS as exogenous contrast agents for enhanced visualization of tumors using narrow band imaging (NBI). NBI takes advantage of the strong NIR absorption of GNS to distinguish between blood and nanoshells in the tumor by imaging in narrow wavelength bands in the visible and NIR, respectively. Using tissue-simulating phantoms, we determined the optimum wavelengths to enhance contrast between blood and GNS. We then used the optimum wavelengths for ex-vivo imaging of tumors extracted from human colon cancer xenograft bearing mice injected with GNS. Systemically delivered GNS accumulated passively in tumor xenografts by enhanced permeability and retention (EPR) effect. Ex-Vivo NBI of tumor xenografts demonstrated tumor specific heterogeneous distribution of GNS with a clear distinction from the tumor vasculature. The results of the present study demonstrate the feasibility of using GNS as contrast agents to visualize tumor tissues using NBI technique. / text

InP obtained by metal-organic vapor phase epitaxy, with properties similar to GaAs, shows mobilities approaching the theoretical maxima at low temperatures. However, the corresponding values remain abnormally low at room temperature where a pronounced electronic excitation to the conduction band is observed simultaneously. This reduction of the mobility is attributed to the presence of deep centers that are electrically inactive at low temperatures but become excited when the temperature increases. A model based on an iterative solution to the Boltzmann equation and accounting for the usual scattering mechanisms, including inelastic interactions, is able to explain the data perfectly and shows that a very high mobility at low temperature is not a sufficient measure of the purity for this material. The binding energy of the deep centers depends on the organo-metalic source used for the growth. This links the solution of this problem to the purification of the chemicals. Depletion effects at the interfaces did not appear to be significant. (Abstract shortened by UMI.)

In the framework of the two-band (Dirac) model, we analyze the electronic structure of nanoscale systems, based on narrow-gap semiconductors of Pb,_xSnx (Se, S) type. Themain attention is paid to the influence of properties of the surface, encoded in appropriate boundary conditions, on the size-quantized spectrum. From this point of view we consider two types of systems: spherical (quantum dots) and quasi one-dimensional (films).It is shown that the spectrum of the spherical quantum dot consists not only of usual size-quantized states, located above the gap edge, but also surface modes residing inside the gap. Such states manifest themselves in the far infrared part of the absorption spectrum, the measurement of which allows one to extract information about the dot surface.Next, we consider a film with the energy gap modulated in the <111> (growth) direction. It is shown that the spectrum of the infinite crystal possesses a supersymmetrical structure. The film boundaries, generally speaking, destroy the supersymmetry, i.e. size-quantized subbands turn out to be spin-split. However, there exists a class of boundary conditions that do not lift spin degeneracy. Physically, in this case there is no band mismatch at interfaces. Our central statement, therefore, consists of the following: even when the inversion symmetry is destroyed by the bulk inhomogeneity, the spin-splitting of the spectrum is a purely surface effect. This is illustrated on a simple example, when the energy gap varies linearly over the film width.Finally, we investigate the role of boundary conditions in the problem of scattering of spinor waves by a quantum dot. It is shown that the existence of surface states greatly modifies the scattering data; in particular, outgoing waves may turn out to be fully polarized. / Department of Physics and Astronomy

In this thesis, the features of electric field signatures of narrow bipolar pulses (NBPs) generated by cloud flashes are investigated and their effects on wireless communication systems are studied. A handful amount of NBPs (14.5%) have been observed to occur as part of cloud-to-ground flashes in South Malaysia. Occurrence of NBPs in Sweden has been reported for the first time in this thesis. The electric field waveform characteristics of NBPs as part of cloud-to-ground flashes were similar to isolated NBPs found in Sweden and South Malaysia and also to those isolated NBPs reported by previous studies from various geographical areas. This is a strong indication that their breakdown mechanisms are similar at any latitudes regardless of geographical areas. A comparative study on the occurrence of NBPs and other forms of lightning flashes across various geographical areas ranging from northern regions to the tropics is presented. As the latitude decreased from Uppsala, Sweden (59.8°N) to South Malaysia (1.5°N), the percentage of NBP emissions relative to the total number of lightning flashes increased significantly from 0.13% to 12%. Occurrences of positive NBPs were more common than negative NBPs at all observed latitudes. However, as latitudes decreased, the negative NBP emissions increased significantly from 20% (Sweden) to 45% (South Malaysia). Factors involving mixed-phase region elevations and vertical extents of thundercloud tops are invoked to explain the observed results. These factors are fundamentally latitude dependent. In this thesis, the interaction between microwave radiations emitted by cloud-to-ground and cloud flashes events and bits transmission in wireless communication networks are also presented. To the best of our knowledge, this is the first time such effects are investigated in the literature. Narrow bipolar pulses were found to be the strongest source of interference that interfered with the bits transmission.

Thick-section austenitic stainless steels have widespread industrial applications, especially in nuclear power plants. The joining methods used in the nuclear industry are primarily based on arc welding processes. However, it has recently been shown that the Narrow Gap Laser Welding (NGLW) technique can be used to join materials with thicknesses that are well beyond the capabilities of single pass autogenous laser welding. The heat input for NGLW is much lower than that of arc welding, as are the expected levels of residual stress and distortion. The multi-pass laser welding technique, based on the narrow gap approach, is an emerging welding technology which can be applied to thick-section welds using a relatively low-power laser, but the process is more complicated than autogenous laser welding, since it is necessary to introduce filler wire to narrow gap weld configurations. Despite this complexity, the technique is very promising for improving the penetration capabilities of the laser welding process. However a limited amount of research has been conducted on the development of the NGLW technique; the control and optimization of weld bead quality inside the narrow gap is still an area of weakness. The research described in this thesis involves investigations on NGLW of AISI grade 316L austenitic stainless steel, and the performance of the resulting welds. Design-of-experiments and statistical modelling techniques were employed to understand and optimize the welding process. A statistical model was used in order to understand the significant process parameters and their interactions, allowing improved control of the weld quality in ultra-narrow gap (1.5 mm gap width) welds. The results show a significant improvement in weld quality can be achieved through the use of statistical modelling and multi-variable optimisation. The microstructure characteristics and mechanical properties (e.g. tensile strengths, fatigue, bending strength and fracture toughness) of the NGLW samples were examined and compared with those of other welding techniques - autogenous laser welding and gas-tungsten arc welding (GTAW). The work shows that NGLW of 316L steel sheets up to 20 mm thickness have generally better or comparable mechanical properties than those of GTAW but with much higher welding productivity. The results of detailed investigations of the 2D residual stress distributions, material distortions, and plastic strain characteristics of the NGLW technique are described. The contour method was employed for residual stress evaluation of the NGLW technique, and the results were validated using X-Ray and neutron diffraction measurements. The results were compared with those obtained with GTAW. The results suggest that the longitudinal tensile residual stresses in NGLW joints are 30-40% lower than those for GTAW joints. The influence of the laser power and number of passes for the NGLW technique, on the developed residual stress and plastic strain has been investigated, and the influence of welding strategy and the use of restraint during welding were also investigated. To understand the thermal history in NGLW and its effect on residual stress, finite element analysis was carried out using ABAQUS to numerically model the behaviour of residual stress across the multipass NGLW weld joints. The model has been validated with the experiments using temperature measurements and in terms of residual stresses the model is compared with neutron diffraction and the contour method. There is a very good correlation between the model and experimental results. The influence of both the laser power and welding speed on the induced residual stress during the NGLW process was also investigated using the model. The aqueous, pitting and stress corrosion cracking behaviour of the NGLW joints were investigated, and the results compared to those for GTAW joints under the same conditions. The results show that NGLW joints have better resistance to pitting corrosion than the GTA welds. Preliminary results also suggest that NGLW has better resistance to stress corrosion cracking.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / Empirical methods play an important role in the field of geomechanics due to the recognized complexity of the nature of rock mass. This study aims to analyze the applicability of empirical design methods in vein-shaped hydrothermal mining deposits (narrow vein) using Bieniawski and Barton classification systems, Mathews stability graphs, Potvin and Mawdesley geomechanics classification systems, and mining pit dilution based on the equivalent linear overbreak/slough (ELOS). In most cases, these methods are applied without understanding the underlying assumptions and limits of the database in relation to the inherent hidden risks. Herein, the dilutions obtained using the empirical methods oscillate between 8% and 11% (according to the frontal dimension), which are inferior to the operative dilution of the mine at 15%. The proposed model can be used as a practical tool to predict and reduce dilution in narrow veins.

A large portion of irrigated soybean in Mississippi are planted on raised beds spaced 96.52 cm apart. There is recent interest in growing soybean in narrower rows. Previous research indicates that narrower row spacing can provide advantages over wider arrangements, including increased light interception, improved weed management and greater seed yield. Soybean was planted in 96.52 cm single rows, 96.52 cm twin rows and 50 cm rows on wide beds (200 cm) at three seeding rates. Canopy closure was monitored throughout the growing season. Soybean planted in narrow rows had consistently faster canopy closure than single rows at all site years. Similarly, there was a 10% to 13% seed yield advantage for the narrow row spacing over the single row spacing at each site year. With the introduction of novel technology, such as the twin row planter, comes equipment malfunction and/or misuse that could reduce seed yield. Producer decisions in the event of a planting/planter error can be challenging. The economic loss due to a planter error may vary by soil type due to differences in plant development. The purpose of this research is to determine the agronomic effects associated with multiple potential twin row planter errors on two distinct soil types across multiple maturity groups commonly found in Mississippi. Canopy closure of each planting error was monitored throughout the growing season. Seed yield was reduced by 9 to 18% when a whole twin row was missing compared to the untreated check at all site years.