Enzymatic Synthesis of Glucose- and Xylose Laurate Esters Using Different Acyl Donors,Higher Substrate Concentrations,and Membrane Assisted Solvent Recovery

Glucose- and xylose laurate esters are enzymatically synthesized using equimolar substrate concentrations in 2-methyl-2-butanol, comparing free lauric acid with methyl- and vinyl-laurate as acyl donors. All reactions result in ≥70% acyl donor conversions after 72 h but the activated donors are also partially hydrolyzed to lauric acid, highlighting the difficulty in controlling water presence in this particular reaction system. The esterification of xylose generates a complex product profile, with several regioisomers of monoesters and diesters. The esterification of glucose is quite selective, forming mainly the 6-O monoester (≥96%) with a small presence of two diester isomers (4%). Increasing substrate concentration up to 800 millimoles kg⁻¹ results in lower conversion values (down to 58%) but shows that the reaction proceeds successfully even in the presence of high amounts of insoluble glucose. However, the reaction is less selective and the proportion of diester increases, becoming up to 46% (molar fraction) of the final product. Solvent recovery after esterification can be achieved by organic solvent nanofiltration through a polymeric membrane able to retain ≥80% of all reaction substrates and products. Practical Applications: The use of high substrate concentrations during the enzymatic synthesis of sugar ester biosurfactants leads to product titers that are more industrially appealing, without the need to find a solvent that can solubilize all initial substrate. The sustainability of the enzymatic conversion at mild temperatures can be enhanced by recycling of the reaction solvent through organic solvent nanofiltration, an energy efficient alternative to other traditional methods like distillation.     

Mixed-mode correlator for micropower acoustic transientclassification

A mixed-mode very large scale integration (VLSI) processor for acoustic transient classification performs a running correlation between a time-frequency decomposed analog input signal and a corresponding template. Differential encoding of the inputs allows simplification of the multiply-and-accumulate operations, operating on binary templates and positive-valued inputs, implemented in current mode with eight MOS transistors per cell including SRAM template storage. The use of a bucket-brigade device (BED) instead of a charge-coupled device (CCD) for shift-and-accumulate operations allows long integration times necessary for acoustic transients spanning several hundred milliseconds. Correlated double sampling at the output compensates for dark current losses in the BED and other common-mode effects. The 64×16 time-frequency correlator measures 700 μm×1170 μm in a 1.2-μm CMOS process and dissipates an average of 30 μW in continuous operation     

VLSI Implementation of Fuzzy Adaptive Resonance and Learning Vector Quantization

We present a mixed-mode VLSI chip performing unsupervised clustering and classification, implementing models of Fuzzy Adaptive Resonance Theory (ART) and Learning Vector Quantization (LVQ), and extending to variants such as Kohonen Self-Organizing Maps (SOM). The parallel processor classifies analog vectorial data into a digital code in a single clock, and implements on-line learning of the analog templates, stored locally and dynamically using the same adaptive circuits for on-chip quantization and refresh. The unit cell performing fuzzy choice and vigilance functions, adaptive resonance learning and long-term analog storage, measures 43 m×43 m in 1.2 m CMOS technology. Experimental learning results from a fabricated 8-input, 16-category prototype are included.     

VLSI Potentiostat Array With Oversampling Gain Modulation for Wide-Range Neurotransmitter Sensing

A 16-channel current-measuring very large-scale integration (VLSI) sensor array system for highly sensitive electrochemical detection of electroactive neurotransmiters like dopamine and nitric-oxide is presented. Each channel embeds a current integrating potentiostat within a switched-capacitor first-order single-bit delta-sigma modulator implementing an incremental analog-to-digital converter. The duty-cycle modulation of current feedback in the delta-sigma loop together with variable oversampling ratio provide a programmable digital range selection of the input current spanning over six orders of magnitude from picoamperes to microamperes. The array offers 100-fA input current sensitivity at 3.4-muW power consumption per channel. The operation of the 3 mm times3 mm chip fabricated in 0.5-mum CMOS technology is demonstrated with real-time multichannel acquisition of neurotransmitter concentration     

Influence of massive heat-pump introduction on the electricity-generation mix and the GHG effect: Comparison between Belgium, France, Germany and The Netherlands

To evaluate the environmental impact of massive heat-pump introduction on greenhouse gas (GHG) emissions in different electricity-generation systems, dynamic simulations have been carried out for four European countries, namely, Belgium, France, Germany and the Netherlands. For this purpose, the simulations are performed with Promix, a tool that models the overall electricity-generation system. Three heating devices are considered for each country, namely classic fossil-fuel heating, heat pumps and electric resistance heating. Both direct heat-pump heating with a coefficient of performance (COP) of 2.5 and accumulation heat-pump heating with a COP of 5 are investigated. The introduction of electric heating in an electricity-generation system increases the demand for electricity and generates a shift of emissions from fossil-fuel heating systems to electrical plants. The results of the simulations reveal that the massive introduction of either heat pump or resistance heating is always favourable to the environment in France. The most environmentally friendly scenario in 2010 is projected to reduce GHG emissions by about 3.8 Mton compared to the reference scenario. In Belgium and Germany, the largest reduction in GHG emissions occurs with accumulation heat pumps. Belgium can save up to 220 kton of GHG emissions, while Germany can attain reductions of 800 kton in 2010. In the Netherlands, a significant reduction can be achieved by considering the addition of gas-fired combined cycle (CC) power plants, together with the introduction of electric heating, resulting in emissions savings of 410 kton.     

Polycyclic N-benzamido imides with potent activity against vaccinia virus

The synthesis and antiviral activity of a series of novel polycyclic analogues of the orthopoxvirus egress inhibitor tecovirimat (ST‐246) is presented. Several of these compounds display sub‐micromolar activity against vaccinia virus, and were more potent than cidofovir (CDV). The more active compounds were about 10‐fold more active than CDV, with minimum cytotoxic concentrations above 100 μM . Chemical manipulations of the two carbon–carbon double bonds present in the compounds were carried out to further explore the structure–activity relationships of these new polycyclic imides. Hydrogenation of the two carbon–carbon double bonds decreases antiviral activity, whereas either cyclopropanation or epoxidation of the double bonds fully eliminates the antiviral activity.     

Aging and the negative priming effect: A meta-analysis.

This article reports results from a meta-analysis on adult age differences in the negative priming effect (21 studies on identity negative priming and 8 on location negative priming). Both younger and older adults were found to be susceptible to the negative priming effect in identity and location tasks. Effect sizes were homogeneous for both tasks, indicating that the data are adequately described without reference to moderator variables. State trace analysis on identity tasks, in which mean latencies in negative priming conditions were regressed onto mean latencies in baseline conditions, showed (a) that in both age groups the negative priming effect is proportional rather than additive and (b) that the negative priming effect is smaller in older adults as compared with younger adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analysis and verification of an analog VLSI incrementalouter-product learning system

An architecture is described for the microelectronic implementation of arbitrary outer-product learning rules in analog floating-gate CMOS matrix-vector multiplier networks. The weights are stored permanently on floating gates and are updated under uniform UV illumination with a general incremental analog four-quadrant outer-product learning scheme, performed locally on-chip by a single transistor per matrix element on average. From the mechanism of floating gate relaxation under UV radiation, the authors derive the learning parameters and their dependence on the illumination level and circuit parameters. It is shown that the weight increments consists of two parts: one term contains the outer product of two externally applied learning vectors; the other part represents a uniform weight decay, with time constant originating from the floating gate relaxation. The authors address the implementation of supervised and unsupervised learning algorithms with emphasis on the delta rule. Experimental results from a simple implementation of the delta rule on an 8x7 linear network are included.     

Aging and the Stroop effect: A meta-analysis.

In this meta-analysis, data from 20 studies comparing younger and older adults on the Stroop interference effect, contained in 15 articles, were analyzed. No significant difference was found in the Stroop interference effect, expressed as mean standardized difference, between the 2 age groups (for younger adults: d?=?2.04; for older adults: d?=?2.17). Moderator variables were present, but these did not produce age differences. Brinley analysis showed that a single regression line with a slowing factor of 1.9 described the data well (R2?=?.83) and confirmed that no Age?×?Condition interaction was present in the data. Likewise, no Age?×?Condition interaction was found when the data were fitted to the information loss model; the age ratio of decay rates was estimated to be 1.4. Consequently, the apparent age-sensitivity of the Stroop interference effect appears to be merely an artifact of general slowing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)