Design of Copolymeric Materials

We devise a method for designing materials that will have some desired structural characteristics. We apply it to multiblock copolymers that have two different types of monomers, A and B. We show how to determine what sequence of A's and B's should be synthesised in order to give a particular structure and morphology. %For example in a melt of such %polymers, one may wish to engineer a body-centered %cubic structure. Using this method in conjunction with the theory of microphase separation developed by Leibler, we show it is possible to efficiently search for a desired morphology. The method is quite general and can be extended to design isolated heteropolymers, such as proteins, with desired structural characteristics. We show that by making certain approximations to the exact algorithm, a method recently proposed by Shakhnovich and Gutin is obtained. The problems with this method are discussed and we propose an improved approximate algorithm that is computationally efficient.Comment: 15 pages latex 2.09 and psfig, 1 postscript figure

Role of cerium in lithium niobate for holographic recording

Cerium-doped lithium niobate crystals are tested for holographic recording. A photochromic effect is observed in crystals doped with cerium and manganese. But two-center recording in the sample is not as effective as in iron and manganese doubly doped crystals. Photocurrent measurements in cerium and iron singly doped crystals indicate that the photovoltaic constant in the cerium-doped crystal is only one third of that of the iron-doped one. This is the main reason accounting for the low sensitivity of cerium-doped lithium niobate crystals. However, in the diffusion dominated case, i.e., for reflection geometry, cerium-doped lithium niobate may give a strong effect

Modeling near-field tsunami observations to improve finite-fault slip models for the 11 March 2011 Tohoku earthquake

The massive tsunami generated by the 11 March 2011 Tohoku earthquake (M_w 9.0) was widely recorded by GPS buoys, wave gauges, and ocean bottom pressure sensors around the source. Numerous inversions for finite-fault slip time histories have been performed using seismic and/or geodetic observations, yielding generally consistent patterns of large co-seismic slip offshore near the hypocenter and/or up-dip near the trench, where estimated peak slip is ~60 m. Modeling the tsunami generation and near-field wave processes using two detailed rupture models obtained from either teleseismic P waves or high-rate GPS recordings in Japan allows evaluation of how well the finite-fault models account for the regional tsunami data. By determining sensitivity of the tsunami calculations to rupture model features, we determine model modifications that improve the fit to the diverse tsunami data while retaining the fit to the seismic and geodetic observations

Multiscale Technicolor and the Zbb-bar Vertex

We estimate the correction to the Zbb-bar vertex arising from the exchanges of the sideways extended technicolor (ETC) boson and the flavor-diagonal ETC boson in the multiscale walking technicolor model. The obtained result is too large to explain the present data. However, if we introduce a new self- interaction for the top quark to induce the top quark condensate serving as the origin of the large top quark mass, the corrected R_b=Gamma_b/Gamma_h can be consistent with the recent LEP data. The corresponding correction to R_c=Gamma_c/Gamma_h is shown to be negligibly small.Comment: 9-page LaTex fil

Production and decay of the neutral top-pion in high energy e+e−e^{+}e^{-} colliders

We study the production and decay of the neutral top-pion $\pi_{t}^{0}$ predicted by topcolor-assisted technicolor(TC2) theory. Our results show that, except the dominant decay modes $b\bar{b}$, $\bar{t}c$ and $gg$, the $\pi_{t}^{0}$ can also decay into $\gamma\gamma$ and $Z \gamma$ modes. It can be significantly produced at high energy $e^{+}e^{-}$ collider(LC) experiments via the processes $e^{+}e^{-}\to \pi_{t}^{0}\gamma$ and $e^{+}e^{-}\to Z\pi_{t}^{0}$. We further calculate the production cross sections of the processes $e^{+}e^{-}\to\gamma\pi_{t}^{0}\to\gamma\bar{t}c$ and $e^{+}e^{-}\to Z\pi_{t}^{0}\to Z\bar{t}c$. We find that the signatures of the neutral top-pion $\pi_{t}^{0}$ can be detected via these processes.Comment: Latex file, 13 Pages, 6 eps figures. to be published in Phys.Rev.

Protein design in a lattice model of hydrophobic and polar amino acids

A general strategy is described for finding which amino acid sequences have native states in a desired conformation (inverse design). The approach is used to design sequences of 48 hydrophobic and polar aminoacids on three-dimensional lattice structures. Previous studies employing a sequence-space Monte-Carlo technique resulted in the successful design of one sequence in ten attempts. The present work also entails the exploration of conformations that compete significantly with the target structure for being its ground state. The design procedure is successful in all the ten cases.Comment: RevTeX, 12 pages, 1 figur

Voltage-independent SK-channel dysfunction causes neuronal hyperexcitability in the hippocampus of Fmr1 knock-out mice

Neuronal hyperexcitability is one of the major characteristics of fragile X syndrome (FXS), yet the molecular mechanisms of this critical dysfunction remain poorly understood. Here we report a major role of voltage-independent potassium (

Parametrical optimization of laser surface alloyed NiTi shape memory alloy with Co and Nb by the Taguchi method

Different high-purity metal powders were successfully alloyed on to a nickel titanium (NiTi) shape memory alloy (SMA) with a 3 kW carbon dioxide (CO2) laser system. In order to produce an alloyed layer with complete penetration and acceptable composition profile, the Taguchi approach was used as a statistical technique for optimizing selected laser processing parameters. A systematic study of laser power, scanning velocity, and pre-paste powder thickness was conducted. The signal-to-noise ratios (S/N) for each control factor were calculated in order to assess the deviation from the average response. Analysis of variance (ANOVA) was carried out to understand the significance of process variables affecting the process effects. The Taguchi method was able to determine the laser process parameters for the laser surface alloying technique with high statistical accuracy and yield a laser surface alloying technique capable of achieving a desirable dilution ratio. Energy dispersive spectrometry consistently showed that the per cent by weight of Ni was reduced by 45 per cent as compared with untreated NiTi SMA when the Taguchi-determined laser processing parameters were employed, thus verifying the laser's processing parameters as optimum

Constraining Radon Backgrounds in LZ

The LZ dark matter detector, like many other rare-event searches, will suffer from backgrounds due to the radioactive decay of radon daughters. In order to achieve its science goals, the concentration of radon within the xenon should not exceed $2\mu$Bq/kg, or 20 mBq total within its 10 tonnes. The LZ collaboration is in the midst of a program to screen all significant components in contact with the xenon. The four institutions involved in this effort have begun sharing two cross-calibration sources to ensure consistent measurement results across multiple distinct devices. We present here five preliminary screening results, some mitigation strategies that will reduce the amount of radon produced by the most problematic components, and a summary of the current estimate of radon emanation throughout the detector. This best estimate totals $<17.3$ mBq, sufficiently low to meet the detector's science goals.Comment: Low Radioactivity Techniques (LRT) 2017 Workshop Proceedings. 6 pages; 3 figure

Production of the neutral top-pion πt0\pi_{t}^{0} in association with a high-pTp_{T} jet at the LHCLHC

In the framework of the topcolor-assisted technicolor $(TC2)$ model, we study production of the neutral top-pion $\pi_{t}^{0}$ in association with a high-$p_{T}$ jet at the $LHC$, which proceeds via the partonic processes $gg\longrightarrow \pi_{t}^{0}g$, $gq\longrightarrow \pi_{t}^{0}q$, $q\bar{q}\longrightarrow \pi_{t}^{0}g$, $gb(\bar{b})\longrightarrow \pi_{t}^{0}b(\bar{b})$, and $b\bar{b}\longrightarrow \pi_{t}^{0}g$. We find that it is very challenging to detect the neutral top-pion $\pi_{t}^{0}$ via the process $pp\longrightarrow \pi_{t}^{0}+jet+X\to t\bar{t}+jet+X$, while the possible signatures of $\pi_{t}^{0}$ might be detected via the process $pp\longrightarrow \pi_{t}^{0}+jet+X\to(\bar{t}c+t\bar{c})+jet+X$ at the $LHC$.Comment: 13 pages, 4 figures; typos correcte