Encoding of mixtures in a simple olfactory system

Natural odors are usually mixtures; yet, humans and animals can experience them as unitary percepts. Olfaction also enables stimulus categorization and generalization. We studied how these computations are performed with the responses of 168 locust antennal lobe projection neurons (PNs) to varying mixtures of two monomolecular odors, and of 174 PNs and 209 mushroom body Kenyon cells (KCs) to mixtures of up to eight monomolecular odors. Single-PN responses showed strong hypoadditivity and population trajectories clustered by odor concentration and mixture similarity. KC responses were much sparser on average than those of PNs and often signaled the presence of single components in mixtures. Linear classifiers could read out the responses of both populations in single time bins to perform odor identification, categorization, and generalization. Our results suggest that odor representations in the mushroom body may result from competing optimization constraints to facilitate memorization (sparseness) while enabling identification, classification, and generalization

Kernelized log linear models for continuous speech recognition

Large margin criteria and discriminative models are two effective improvements for HMM-based speech recognition. This paper proposed a large margin trained log linear model with kernels for CSR. To avoid explicitly computing in the high dimensional feature space and to achieve the nonlinear decision boundaries, a kernel based training and decoding framework is proposed in this work. To make the system robust to noise a kernel adaptation scheme is also presented. Previous work in this area is extended in two directions. First, most kernels for CSR focus on measuring the similarity between two observation sequences. The proposed joint kernels defined a similarity between two observation-label sequence pairs on the sentence level. Second, this paper addresses how to efficiently employ kernels in large margin training and decoding with lattices. To the best of our knowledge, this is the first attempt at using large margin kernel-based log linear models for CSR. The model is evaluated on a noise corrupted continuous digit task: AURORA 2.0. © 2013 IEEE.

Field programmable gate array based predictive control system for spacecraft rendezvous in elliptical orbits

Copyright © 2014 John Wiley & Sons, Ltd. Copyright © 2014 John Wiley & Sons, Ltd. Summary A field programmable gate array (FPGA) based model predictive controller for two phases of spacecraft rendezvous is presented. Linear time-varying prediction models are used to accommodate elliptical orbits, and a variable prediction horizon is used to facilitate finite time completion of the longer range manoeuvres, whilst a fixed and receding prediction horizon is used for fine-grained tracking at close range. The resulting constrained optimisation problems are solved using a primal-dual interior point algorithm. The majority of the computational demand is in solving a system of simultaneous linear equations at each iteration of this algorithm. To accelerate these operations, a custom circuit is implemented, using a combination of Mathworks HDL Coder and Xilinx System Generator for DSP, and used as a peripheral to a MicroBlaze soft-core processor on the FPGA, on which the remainder of the system is implemented. Certain logic that can be hard-coded for fixed sized problems is implemented to be configurable online, in order to accommodate the varying problem sizes associated with the variable prediction horizon. The system is demonstrated in closed-loop by linking the FPGA with a simulation of the spacecraft dynamics running in Simulink on a PC, using Ethernet. Timing comparisons indicate that the custom implementation is substantially faster than pure embedded software-based interior point methods running on the same MicroBlaze and could be competitive with a pure custom hardware implementation.

Sparse recovery of complex phase-encoded velocity images using iterative thresholding

In this paper we propose a new algorithm for reconstructing phase-encoded velocity images of catalytic reactors from undersampled NMR acquisitions. Previous work on this application has employed total variation and nonlinear conjugate gradients which, although promising, yields unsatisfactory, unphysical visual results. Our approach leverages prior knowledge about the piecewise-smoothness of the phase map and physical constraints imposed by the system under study. We show how iteratively regularizing the real and imaginary parts of the acquired complex image separately in a shift-invariant wavelet domain works to produce a piecewise-smooth velocity map, in general. Using appropriately defined metrics we demonstrate higher fidelity to the ground truth and physical system constraints than previous methods for this specific application. © 2013 IEEE.

Preloaded hopping with linear multi-modal actuation

For more dexterous and agile legged robot locomotion, alternative actuation has been one of the most long-awaited technologies. The goal of this paper is to investigate the use of newly developed actuator, the so-called Linear Multi-Modal Actuator (LMMA), in the context of legged robot locomotion, and analyze the behavioral performance of it. The LMMA consists of three discrete couplings which enable the system to switch between different mechanical dynamics such as instantaneous switches between series elastic and fully actuated dynamics. To test this actuator for legged locomotion, this paper introduces a one-legged robot platform we developed to implement the actuator, and explains a novel control strategy for hopping, i.e. 'preloaded hopping control'. This control strategy takes advantage of the coupling mechanism of the LMMA to preload the series elasticity during the flight phase to improve the energy efficiency of hopping locomotion. This paper shows a series of experimental results that compare the control strategy with a simple sinusoidal actuation strategy to discuss the benefits and challenges of the proposed approach. © 2013 IEEE.

Evolution of wetting layer in InAs/GaAs quantum dot system

For InAs/GaAs quantum dot system, the evolution of the wetting layer (WL) with the InAs deposition thickness has been studied by reflectance difference spectroscopy (RDS). Two transitions related to the heavy-and light-hole in the WL have been distinguished in RD spectra. Taking into account the strain and segregation effects, a model has been presented to deduce the InAs amount in the WL and the segregation coefficient of the indium atoms from the transition energies of heavy-and light-holes. The variation of the InAs amount in the WL and the segregation coefficient are found to rely closely on the growth modes. In addition, the huge dots also exhibits a strong effect on the evolution of the WL. The observed linear dependence of In segregation coefficient upon the InAs amount in the WL demonstrates that the segregation is enhanced by the strain in the WL.

High resolution interrogation technique based on linear photodiode array spectrometer for fiber Bragg grating Sensors - art. no. 65952C

A linear photodiode array spectrometer based, high resolution interrogation technique for fiber Bragg grating sensors is demonstrated. Spline interpolation and Polynomial Approximation Algorithm (PAA) are applied to the data points acquired by the spectrometer to improve the original PAA based interrogation method. Thereby fewer pixels are required to achieve the same resolution as original. Theoretical analysis indicates that if the FWHM of a FBG covers more than 3 pixels, the resolution of central wavelength shift will arrive at less than 1 pm. While the number of pixels increases to 6, the nominal resolution will decrease to 0.001 pm. Experimental result shows that Bragg wavelength resolution of similar to 1 pm is obtained for a FBG with FWHM of similar to 0.2 nm using a spectrometer with a pixel resolution of similar to 70 pm.

A multi-standard active-RC filter with accurate tuning system

A low-power, highly linear, multi-standard, active-RC filter with an accurate and novel tuning architec-ture is presented. It exhibits 1EEE 802. 11a/b/g (9.5 MHz) and DVB-H (3 MHz, 4 MHz) application. The filter exploits digitally-controlled polysilicon resistor banks and a phase lock loop type automatic tuning system. The novel and complex automatic frequency calibration scheme provides better than 4 comer frequency accuracy, and it can be powered down after calibration to save power and avoid digital signal interference. The filter achieves OIP3 of 26 dBm and the measured group delay variation of the receiver filter is 50 ns (WLAN mode). Its dissipation is 3.4 mA in RX mode and 2.3 mA (only for one path) in TX mode from a 2.85 V supply. The dissipation of calibration consumes 2 mA. The circuit has been fabricated in a 0.35μm 47 GHz SiGe BiCMOS technology; the receiver and transmitter filter occupy 0.21 mm~2 and 0.11 mm~2 (calibration circuit excluded), respectively.

Fiber Optic Coupling of CW Linear Laser Diode Array

Based on a set of microoptics the output radiation from a continuous wave (CW) linear laser diode array is coupled into a multi-mode optical fiber of 400 ptm diameter. The CW linear laser diode array is a 1 cm laser diode bar with 19 stripes with 100 fxm aperture spaced on 500 (xm centers. The coupling system contains packaged laser diode bar, fast axis collimator, slow axis collimation array, beam transformation system and focusing system. The high brightness, high power density and single fiber output of a laser diode bar is achieved. The coupling efficiency is 65% and the power density is up to 1.03 * 10~4 W/cm~2.

Comparison of aggregation behaviors between branched and linear block polyethers: MesoDyn simulation study

The comparison of aggregation behaviors between the branched block polyether T1107 (polyether A) and linear polyether (EO)(60)(PO)(40)(EO)(60) (polyether B) in aqueous solution are investigated by the MesoDyn simulation. Polyether A forms micelles at lower concentration and has a smaller aggregation number than B. Both the polyethers show the time-dependent micellar growth behaviors. The spherical micelles appear and then change to rod-like micelles with time evolution in the 10 vol% solution of polyether A. The micellar cluster appears and changes to pseudo-spherical micelles with time evolution in the 20 vol% solution of polyether A. However, the spherical micelles appear and change to micellar cluster with time evolution in the 20 vol% polyether B solution. The shear can induce the micellar transition of both block polyethers. When the shear rate is 1x10(5) s(-1), the shear can induce the sphere-to-rod transition of both polyethers at the concentration of 10 and 20 vol%. When the shear rate is lower than 1x10(5) s(-1), the huge micelles and micellar clusters can be formed in the 10 and 20 vol% polyether A systems under the shear, while the huge micelles are formed and then disaggregated with the time evolution in the 20 vol% polyether B system.

Linear spatio-temporal instability analysis of ice growth under a falling water film

A linear spatio-temporal stability analysis is conducted for the ice growth under a falling water film along an inclined ice plane. The full system of linear stability equations is solved by using the Chebyshev collocation method. By plotting the boundary curve between the linear absolute and convective instabilities (AI/CI) of the ice mode in the parameter plane of the Reynolds number and incline angle, it is found that the linear absolute instability exists and occurs above a minimum Reynolds number and below a maximum inclined angle. Furthermore, by plotting the critical Reynolds number curves with respect to the inclined angle for the downstream and upstream branches, the convectively unstable region is determined and divided into three parts, one of which has both downstream and upstream convectively unstable wavepackets and the other two have only downstream or upstream convectively unstable wavepacket. Finally, the effect of the Stefan number and the thickness of the ice layer on the AI/CI boundary curve is investigated.

Three-Dimensional Linear Instability Analysis of Thermocapillary Return Flow on a Porous Plane

A three-dimensional linear instability analysis of thermocapillary convection in a fluid-porous double layer system, imposed by a horizontal temperature gradient, is performed. The basic motion of fluid is the surface-tension-driven return flow, and the movement of fluid in the porous layer is governed by Darcy's law. The slippery effect of velocity at the fluid-porous interface has been taken into account, and the influence of this velocity slippage on the instability characteristic of the system is emphasized. The new behavior of the thermocapillary convection instability has been found and discussed through the figures of the spectrum.

Quantum dots-bienzyme hybrid system for the sensitive determination of glucose

In this paper, we attempt to develop a sensitive detection method for glucose with the combination of the unique optical property of quantum dots and the specificity of enzymatic reactions. With glucose and hydroquinone as substrates, benzoquinone that intensively quenches the photoluminescence of quantum dots can be produced via the catalysis of bienzyme (glucose oxidase and horseradish peroxidase) system. A relatively low detection limit of 1.0 x 10(-8) mol/L can be achieved. Two linear ranges from 1.0 x 10(-6) to 1.5 x 10(-4) M and from 1.5 x 10(-4) to 1.0 x 10(-3) M were obtained.

Sensitive and Selective Sensor for Biothiols in the Cell Based on the Recovered Fluorescence of the CdTe Quantum Dots-Hg(II) System

Herein, a sensitive and selective sensor for biothiols based on the recovered fluorescence of the CdTe quantum dots (QDs)-Hg(II) system is reported. Fluorescence of QDs could be quenched greatly by Hg(II). In the presence of biothiols, such as glutathione (GSH), homocysteine (Hcy), and cysteine (Cys), however, Hg(H) preferred to react with them to form the Hg(II)-S bond because of the strong affinity with the thiols of biothiols rather than quenching the fluorescence of the QDs. Thus, the fluorescence of CdTe QDs was recovered. The restoration ability followed the order GSH > Hcy > Cys due to the decreased steric hindrance effect. A good linear relationship was obtained from 0.6 to 20.0 mu mol L-1 for GSH and from 2.0 to 20.0 mu mol L-1 for Cys, respectively. The detection limits of GSH and Cys were 0.1 and 0.6 mu mol L-1, respectively. In addition, the method showed a high selectivity for Cys among the other 19 amino acids. Furthermore, it succeeded in detecting biothiols in the Hela cell.

Colorimetric recognition of the coralyne-poly(dA) interaction using unmodified gold nanoparticle probes, and further detection of coralyne based upon this recognition system

Among the functional nucleic acids studied, adenine-rich nucleic acids have attracted attention due to their critical roles in many biological processes and self-assembly-based nanomaterials, especially deoxyribonucleic acids (abbreviated as poly(dA)). Therefore the ligands binding to poly(dA) might serve as potential therapeutic agents. Coralyne, a kind of planar alkaloid, has been firstly found that it could bind strongly to poly(dA). This work herein reports an approach for visual sensing of the coralyne-poly(dA) interaction. This method was based on the coralyne inducing poly(dA) into the homo-adenine DNA duplex and the difference in electrostatic affinity between single-stranded DNA and double-stranded DNA with gold nanoparticles (GNPs). Furthermore, we applied the recognition process of the interaction between coralyne and poly(dA) into specific coralyne detection with the assistance of certain software (such as Photoshop). A linear response from 0 to 728 nM was obtained for coralyne, and a detection limit of 91 nM was achieved.