Activity in the Visual Cortex is Modulated by Top-Down Attention Locked to Reaction Time

We studied the correlation between perception and hemodynamic activity in the visual cortex in a change detection task. Whenever the observer perceived the location of a change, rightly or wrongly, the blood oxygenation level-dependent signal increased in the primary visual cortex and the nearby extrastriate areas above the baseline activity caused by the visual stimulation. This non-sensory-evoked activity was localized and corresponded to the perceived location of the change. When a change was missed, or when observers attended to a different task, the change failed to evoke such a response. The latency of the nonsensory component increased linearly with subjects' reaction time, with a slope of one, and its amplitude was independent of contrast. Control experiments are compatible with the hypothesis that the nonsensory hemodynamic signal is mediated by top-down spatial attention, linked to (but separate from) awareness of the change

Suppressive effect of sustained low-contrast adaptation followed by transient high-contrast on peripheral target detection

We observed that presenting a low-contrast Gabor patch (2 cpd, 5° eccentricity, contrast=4%) for 8 s and then flashing a 20–30 ms high-contrast patch over it could elicit the perceptual disappearance of a subsequent low-contrast stimulus, whereas neither low-contrast adaptation nor high-contrast flash alone had any considerable effect (p<0.00001). In other experiments we found (a) suppressive components are phase-insensitive, (b) the effect transfers between eyes, (c) suppression is selective for orientation, and (d) the induction by the transient high-contrast Gabor patch could be transferred to another previously adapted location up to a few degrees. Results indicate synergy between contrast and adaptation through a non-linear interaction between rapid gain adjustment to transient change and adaptation to sustained spatial patterns. Findings are compatible with non-local mechanisms presumably at the cortical level

Ultra Low Power Digital Circuit Design for Wireless Sensor Network Applications

Ny forskning innenfor feltet trådløse sensornettverk åpner for nye og innovative produkter og løsninger. Biomedisinske anvendelser er blant områdene med størst potensial og det investeres i dag betydelige beløp for å bruke denne teknologien for å gjøre medisinsk diagnostikk mer effektiv samtidig som man åpner for fjerndiagnostikk basert på trådløse sensornoder integrert i et ”helsenett”. Målet er å forbedre tjenestekvalitet og redusere kostnader samtidig som brukerne skal oppleve forbedret livskvalitet som følge av økt trygghet og mulighet for å tilbringe mest mulig tid i eget hjem og unngå unødvendige sykehusbesøk og innleggelser. For å gjøre dette til en realitet er man avhengige av sensorelektronikk som bruker minst mulig energi slik at man oppnår tilstrekkelig batterilevetid selv med veldig små batterier. I sin avhandling ” Ultra Low power Digital Circuit Design for Wireless Sensor Network Applications” har PhD-kandidat Farshad Moradi fokusert på nye løsninger innenfor konstruksjon av energigjerrig digital kretselektronikk. Avhandlingen presenterer nye løsninger både innenfor aritmetiske og kombinatoriske kretser, samtidig som den studerer nye statiske minneelementer (SRAM) og alternative minnearkitekturer. Den ser også på utfordringene som oppstår når silisiumteknologien nedskaleres i takt med mikroprosessorutviklingen og foreslår løsninger som bidrar til å gjøre kretsløsninger mer robuste og skalerbare i forhold til denne utviklingen. De viktigste konklusjonene av arbeidet er at man ved å introdusere nye konstruksjonsteknikker både er i stand til å redusere energiforbruket samtidig som robusthet og teknologiskalerbarhet øker. Forskningen har vært utført i samarbeid med Purdue University og vært finansiert av Norges Forskningsråd gjennom FRINATprosjektet ”Micropower Sensor Interface in Nanometer CMOS Technology”

Biointegrated and wirelessly powered implantable brain devices: a review

Implantable neural interfacing devices have added significantly to neural engineering by introducing the low-frequency oscillations of small populations of neurons known as local field potential as well as high-frequency action potentials of individual neurons. Regardless of the astounding progression as of late, conventional neural modulating system is still incapable to achieve the desired chronic in vivo implantation. The real constraint emerges from mechanical and physical diffierences between implants and brain tissue that initiates an inflammatory reaction and glial scar formation that reduces the recording and stimulation quality. Furthermore, traditional strategies consisting of rigid and tethered neural devices cause substantial tissue damage and impede the natural behaviour of an animal, thus hindering chronic in vivo measurements. Therefore, enabling fully implantable neural devices, requires biocompatibility, wireless power/data capability, biointegration using thin and flexible electronics, and chronic recording properties. This paper reviews biocompatibility and design approaches for developing biointegrated and wirelessly powered implantable neural devices in animals aimed at long-term neural interfacing and outlines current challenges toward developing the next generation of implantable neural devices

Total dominator total coloring of a graph

Here, we initiate to study the total dominator total coloring of a graph which is a total coloring of the graph such that each object of the graph is adjacent or incident to every object of some color class. In more details, while in section 2 we present some tight lower and upper bounds for the total dominator total chromatic number of a graphs in terms of some parameters such as order, size, the total dominator chromatic and total domination numbers of the graph and its line graph, in section 3 we restrict our to trees and present a Nordhaus-Gaddum-like relation for trees. Finally in last section we show that there exist graphs that their total dominator total chromatic numbers are equal to their orders

Characterization of radio active aerosols in Tehran research reactor containment

The objectives of this research were to determine the levels of radioactivity in the Tehran research reactor containment and to investigate the mass-size distribution, composition, and concentration of radio nuclides during operation of the reactor. A cascade impactor sampler was used to determine the size-activity distributions of radioactive aerosols in each of the sampling stations. Levels of α and β activities were determined based on a counting method using a liquid scintillation counter and smear tests. The total average mass fractions of fine particles (particle diameter dp &lt;1 µm) in all of the sampling stations were approximately 26.75 , with the mean and standard deviation of 52.15 ± 19.75 µg/m3. The total average mass fractions of coarse particles were approximately 73.2, with the mean and standard deviation of 71.34 ± 24.57 µg/m3. In addition to natural radionuclides, artificial radionuclides, such as 24Na,91Sr,131I,133I,103Ru,82Br, and 140La, may be released into the reactor containment structure. Maximum activity was associated with accumulation-mode particles with diameters less than 400 nm. The results obtained from liquid scintillation counting suggested that the mean specific activity of alpha particles in fine and coarse-modes were 89.7 and 10.26 , respectively. The mean specific activity of beta particles in fine and coarse-modes were 81.15 and 18.51 , respectively. A large fraction ofthe radionuclides' mass concentration in the Tehran research reactor containment was associated with coarse-mode particles, in addition, a large fraction of the activity in the aerosol particles was associated with accumulation-mode particles. © 2015, Vinca Inst Nuclear Sci. All rights reserved

Optimization of recombinant laccase production by Yarrowia lipolytica in a medium containing glucose as carbon source with Taguchi method

Introduction:Laccases (EC 1.10.3.2; benzenediol: oxygen oxidoreductase) are copper-containing oxidases that use molecular oxygen to oxidize various aromatic and non-aromatic compounds. Laccase is applied in delignification of lignocellulosic compounds for production of bioethanol, bioremediation of industrial wastewaters especially textile, food industries, and making biosensors. Materials and methods: The Taguchi experimental design method was used for optimization of laccase production in recombinant strain Yarrowia lipolytica YL4. A L-16 Taguchi orthogonal array was used to optimize the carbon and nitrogen sources along with vitamin in four levels. Results: The results showed that glucose, ammonium chloride, yeast extract and thiamine have significant effects on the production of laccase, respectively. The laccase activity reached to 1.52 U/mL after optimization of medium which is 7.6-fold higher than un-optimized medium. Discussion and conclusion: According to the analysis of results, the Taguchi experimental design method is a successful approach to increase laccase and recombinant proteins production in Y. lipolytica