Modified beamformers for coherent source region suppression

Many tomographic source localization algorithms used in biomagnetic imaging assume, explicitly or sometimes implicitly, that the source activity at different brain locations are either independent or that the correlation structure between sources is known. Among these algorithms is a class of adaptive spatial filters known as beamformers, which have superior spatiotemporal resolution abilities. The performance of beamformers is robust to weakly coherent sources. However, these algorithms are extremely sensitive to the presence of strongly coherent sources. A frequent mode of failure in beamformers occurs with reconstruction of auditory evoked fields (AEFs), in which bilateral auditory cortices are highly coherent in their activation. Here, we present a novel beamformer that suppresses activation from regions with interfering coherent sources. First, a volume containing the interfering sources is defined. The lead field matrix for this volume is computed and reduced into a few significant columns using singular value decomposition (SVD). A vector beamformer is then constructed by rejecting the contribution of sources in the suppression region while allowing for source reconstruction at other specified regions. Performance of this algorithm was first validated with simulated data. Subsequent tests of this modified beamformer were performed on bilateral AEF data. An unmodified vector beamformer using whole head coverage misplaces the source medially. After defining a suppression region containing the temporal cortex on one side, the described method consistently results in clear focal activations at expected regions of the contralateral superior temporal plane.     

A gas-phase chemiluminescence-based analyzer for waterborne arsenic

We show a practical sequential injection/zone fluidics-based analyzer that measures waterborne arsenic. The approach is capable of differentiating between inorganic As(III) and As(V). The principle is based on generating AsH3 from the sample in a confined chamber by borohydride reduction at controlled pH, sparging the chamber to drive the AsH3 to a small reflective cell located atop a photomultiplier tube, allowing it to react with ozone generated from ambient air, and measuring the intense chemiluminescence that results. Arsine generation and removal from solution results in isolation from the sample matrix, avoiding the pitfalls encountered in some solution-based analysis techniques. The differential determination of As(III) and As(V) is based on the different pH dependence of the reducibility of these species to AsH3. At pH < or =1, both As(III) and As(V) are quantitatively converted to arsine in the presence of NaBH4. At a pH of 4-5, only As(III) is converted to arsine. In the present form, the limit of detection (S/N = 3) is 0.05 microg/L As at pH < or =1 and 0.09 microg/L As(III) at pH approximately 4-5 for a 3-mL sample. The analyzer is intrinsically automated and requires 4 min per determination. It is also possible to determine As(III) first at pH 4.5 and then determine the remaining As in a sequential manner; this requires 6 min. There are no significant practical interferences. A new borohydride solution formulation permits month-long reagent stability.     

Single column trapping/separation and chemiluminescence detection for on-site measurement of methyl mercaptan and dimethyl sulfide

A simple, automated method for the measurement of methyl mercaptan (CH3SH) and dimethyl sulfide (DMS) has been investigated. These two sulfur gases have strong and unpleasant odors. The collection and separation are performed in sequence with a single short column packed with silica gel powder. CH3SH and DMS are separated according to their desorption temperatures and introduced into a chemiluminescence cell in this order. These two gases emit strong chemiluminescence by reaction with ozone. The calibration curves obtained are linear, which is superior to flame photometric detection of these substances. The whole system, including a small cylinder for the carrier nitrogen, can be set in a portable box. The instrument is applicable to breath odor analysis, and automated measurement of room air can also be performed. In toilet air analysis, it was observed that levels of the sulfur gases increased after dark. With this instrument, sulfur gases at a ppbv level are successfully measured by a simple procedure without much interference.     

Measurement of ammonia in human breath with a liquid-film conductivity sensor

Measurement of breath NH3 is of interest in clinical applications as it can be used as a measure of kidney/liver functions as well as halitosis. We have developed a liquid-film conductivity sensor to measure NH3 in human breath. A film of dilute H2SO4 is formed on the top of two metal capillary tubes placed in a concentric annular arrangement. The tube exterior has been specially treated to render it hydrophilic. As breath passes over the sensor tip, the film collects NH3 and the solution conductivity (measured by the concentric capillaries functioning as electrodes) decreases accordingly. This initial rate of conductivity decrease was determined to be the best metric (most rapid and least dependent on breath pCO2) for ammonia, relative to time to attain complete neutralization (conductivity minimum) or the final rate of conductivity increase as more ammonia dissolves after neutralization. The absorbing solution composition was optimized so that CO2 does not interfere. Both dynamic measurement using mask sampling and offline balloon sampling were performed. Ammonia readily absorbs on surfaces when significant concentrations of water vapor are present. As such, memory effects are common when analyzing human breath for ammonia. This problem was successfully eliminated. The results from this sensor agreed well with data obtained by a solution-phase fluorometric technique using a porous membrane diffusion scrubber and o-phthalaldehyde derivatization chemistry. For breath CO2 measurement, the applicability of a similar sensor that relies on a NaOH film was also demonstrated.     

Effect of components extracted from okara on the physicochemical properties of soymilk and tofu texture

ABSTRACT:  The physicochemical properties of soymilk and the texture of tofu were compared with regard to 2 kinds of soymilk, one of which was prepared by squeezing homogenates before heating and the other was prepared by squeezing after heating raw soymilk with okara, residue of soymilk production. Relative particulate protein content and viscosity were higher and pH was lower in the soymilk prepared by the latter method, in which liberated lipid bodies were decreased and more lipids were precipitated with protein after centrifugation, suggesting a change in the interaction between proteins and lipids. A difference in the distribution of proteins and lipids was also implied by analysis with a laser particle size analyzer. The breaking stress of tofu made with 0.30% glucono-delta-lactone increased in accordance with an increase in particulate protein. The calcium and magnesium contents increased in soymilk prepared by squeezing after heating with okara. Viscosity was slightly increased and pH decreased by adding calcium to the soymilk, but the particulate protein content and breaking stress of tofu did not increase significantly. To examine the effect of macromolecules, okara was extracted by boiling and dialyzed. Viscosity and particulate protein content in soymilk increased as the dialyzed extracts of the okara were added. The breaking stress of tofu was increased by adding the dialyzed extracts but excessive amounts of the extracts resulted in softer tofu. Spectra of Fourier-transform infrared spectroscopy and electrophoresis-separated patterns of proteins indicated that the dialyzed extracts contained mainly polysaccharides and the Basic 7S globulin protein.     

P-nitrophenol degradation by activated sludge attached on nonwovens

p-Nitrophenol (PNP) is a toxic compound that enters the environment during manufacturing and processing of a variety of industrial products. This study demonstrates the use of inexpensive and durable nonwovens as a biomass retainer for the biological degradation of p-nitrophenol. An essential aspect of p-nitrophenol degradation was the cultivation of p-nitrophenol degrading biomass prior to its attachment on the nonwovens. Results of continuous flow experiments demonstrated that using the nonwovens could attain consistent high-rate p-nitrophenol degradation. 500 mg-PNP/L was completely degraded at a hydraulic retention time of 11 h. Specific and volumetric p-nitrophenol loading rates were determined to be 165 mg-PNP/g-MLSS/d and 1.6 g-PNP/L/d, respectively. Nitrite released from p-nitrophenol breakdown was not completely nitrified to nitrate. Characteristics of p-nitrophenol degrading sludge were also investigated.     

Biosynthesis of the Fungal Organophosphonate Fosfonochlorin Involves an Iron(II) and 2-(Oxo)glutarate Dependent Oxacyclase

The fungal metabolite Fosfonochlorin features a chloroacetyl moiety that is unusual within known phosphonate natural product biochemistry. Putative biosynthetic genes encoding Fosfonochlorin in Fusarium and Talaromyces spp. were investigated through reactions of encoded enzymes with synthetic substrates and isotope labelling studies. We show that the early biosynthetic steps for Fosfonochlorin involve the reduction of phosphonoacetaldehyde to form 2-hydroxyethylphosphonic acid, followed by oxidative intramolecular cyclization of the resulting alcohol to form (S)-epoxyethylphosphonic acid. The latter reaction is catalyzed by FfnD, a rare example of a non-heme iron/2-(oxo)glutarate dependent oxacyclase. In contrast, FfnD behaves as a more typical oxygenase with ethylphosphonic acid, producing (S)-1-hydroxyethylphosphonic acid. FfnD thus represents a new example of a ferryl generating enzyme that can suppress the typical oxygen rebound reaction that follows abstraction of a substrate hydrogen by a ferryl oxygen, thereby directing the substrate radical towards a fate other than hydroxylation.     

Growing neural gas based navigation system in unknown terrain environment for an autonomous mobile robot

Artificial Life and Robotics - Recently, various types of autonomous robots have been expected in many fields such as a disaster site, forest, and so on. The autonomous robots are assumed to be...     

Adaptive optimal stimulus selection in cognitive models using a model averaging approach

Behaviormetrika - Stimulus selection based on the maximum Fisher information (MFI) principle enables the efficient estimation of participant parameters of cognitive models with elaborated...