Enantiodifferentiation in asymmetric sonochemical hydrogenations

The effect of sonochemical pretreatment on the enantioselectivity of Pt/Al₂O₃–cinchonidine-catalyzed ethyl pyruvate hydrogenation was studied at different hydrogen pressures in various solvents, mainly in acetic acid. The sonochemical pretreatment of a commercial Pt/Al₂O₃–cinchonidine catalytic system in acetic acid resulted in enhanced enantioselectivity providing excellent ee values (97% ee) under mild and widely varied experimental conditions. Moreover, the application of ultrasonics provides a possibility of the catalyst recycling without regeneration. The catalyst was tested by transmission electron microscopy to determine the effect of the sonication on the metal particle size morphology. This revised version was published online in July 2006 with corrections to the Cover Date.     

Directional,passive liquid transport: the Texas horned lizard as a model for a biomimetic ‘liquid diode’

Moisture-harvesting lizards such as the Texas horned lizard (Iguanidae: Phrynosoma cornutum) live in arid regions. Special skin adaptations enable them to access water sources such as moist sand and dew: their skin is capable of collecting and transporting water directionally by means of a capillary system between the scales. This fluid transport is passive, i.e. requires no external energy, and directs water preferentially towards the lizard''s snout. We show that this phenomenon is based on geometric principles, namely on a periodic pattern of interconnected half-open capillary channels that narrow and widen. Following a biomimetic approach, we used these principles to develop a technical prototype design. Building upon the Young–Laplace equation, we derived a theoretical model for the local behaviour of the liquid in such capillaries. We present a global model for the penetration velocity validated by experimental data. Artificial surfaces designed in accordance with this model prevent liquid flow in one direction while sustaining it in the other. Such passive directional liquid transport could lead to process improvements and reduction of resources in many technical applications.     

Empirical Correlations for Free Convection in an Isothermal Asymmetrically Heated Vertical Channel

Laminar free convection in an isothermal asymmetrically heated vertical channel has been extensively studied in the past, and empirical correlations for the overall channel convective heat transfer rate are available in the literature. However, this problem has been revisited in order to develop empirical correlations that allow the calculation of the average Nusselt number for each channel wall separately. A numerical solution has been obtained for a Prandtl number of 0.71 and for Rayleigh numbers ranging from the conduction regime to the isolated boundary layer regime. The data have been used to develop correlations for the average Nusselt numbers on the hot and cold walls. These correlations satisfy a heat balance for the overall channel.     

Signal processing of the surface electromyogram to gain insight into neuromuscular physiology

A surface electromyogram (sEMG) contains information about physiological and morphological characteristics of the active muscle and its neural strategies. Because the electrodes are situated on the skin above the muscle, the sEMG is an easily obtainable source of information. However, different combinations of physiological and morphological characteristics can lead to similar sEMG signals and sEMG recordings contain noise and other artefacts. Therefore, many sEMG signal processing methods have been developed and applied to allow insight into neuromuscular physiology. This paper gives an overview of important advances in the development and applications of sEMG signal processing methods, including spectral estimation, higher order statistics and spatio-temporal processing. These methods provide information about muscle activation dynamics and muscle fatigue, as well as characteristics and control of single motor units (conduction velocity, firing rate, amplitude distribution and synchronization).     

The semiotics of landscape design communication: towards a critical visual research approach in landscape architecture

In landscape architecture, visual representations are the primary means of communication between stakeholders in design processes. Despite the reliance on visual representations, little critical research has been undertaken by landscape architects on how visual communication forms work or their socio-political implications. In this theoretical paper, we argue that such research is of great importance. We explain how concepts of visual and critical social theory such as visual semiotics, simulacra and simulation, and power/knowledge can be used to critically reflect on landscape architectural representations. We further propose to study these representations at different stages of meaning-making by using visual methodologies such as visual discourse analysis, iconographical content analysis and social semiotic analysis. We conclude that these research approaches have the potential to explain issues such as dominant power structures, miscommunication between participants, and visual path-dependencies during landscape design processes.     

Application of Neural Networks and Meta-Learners to Recognize Beef from OTM Cattle by Using Volatile Organic Compounds

Cattle with age under 30 months (UTM) are usually slaughtered for human consumption to be not associated of the disease called mad cow. Though the age of the animal can generally be estimated by dentition, this method cannot be applied to a piece of meat from which the teeth have been removed. Since volatile organic compounds have been used to analyze food samples, this technique was used to recognize meat obtained from cattle aged over 30 months (OTM). The monitoring of the volatile organic compounds (VOCs) released by UTM and OTM beef were done by using gas chromatography. A dataset with more than 500 chromatograms (each one with 17 VOCs fully identified) from fresh meat, refrigerated meat and vacuum-packaged meat was used to develop a classifier by using neural networks. Neural networks were trained with backpropagation, and then further optimized by using meta-learners. Optimal configuration of the neural networks allowed discriminating between beef obtained from OTM or UTM cattle with accuracy close to 90 %. Results contrast favorably with more traditional statistical methods such as linear discriminant analysis (LDA), soft independent modeling of class analogies (SIMCA), partial least square discriminate analysis (PLS-DA), and support vector machines (SVM). In conclusion, VOCs can be used as a fingerprint to recognize OTM beef from a pool of meat obtained indistinctly from fresh meat, refrigerated, or vacuum-packaged meat.     

Motor unit size estimation of enlarged motor units with surface electromyography

Surface EMG is hardly used to estimate motor unit (MU) characteristics, while its non-invasiveness is less stressful for patients and allows multi-electrode recordings to investigate different sites of the muscle and MU. The present study compares motor unit potentials (MUPs) obtained with surface EMG and macro EMG during voluntary contraction of the biceps brachii muscle of patients with enlarged MUs caused by prior poliomyelitis. Averaged surface MUPs were obtained by means of needle EMG (SMUP1) and surface EMG (SMUP2) triggering. The MUPs area and peak amplitudes correlated well when comparing the macro MUP and SMUP1 of the same MUs. When MU populations of different patients were compared, the SMUP1s and SMUP2s were equally sensitive to pathology as macro MUPs. In this, the late non-propagating positive wave (only present in unipolar recordings) is more robust than the triphasic propagating wave. Therefore, surface EMG can be used for detecting enlarged MUs.     

Dutch analysis for P-recovery from municipal wastewater.

There is a considerable practical interest in phosphorus recovery from water authorities, elementary P-industry, fertilizer industry and regulators in a number of countries. Due to a handful of full-scale plants worldwide, P-recovery can be seen as technically feasible. However, the economic feasibility of P-recovery from sewage can still be judged as dubious. The most important reason for this is that the prices of the techniques (in euro/tonne P) are much higher compared to the prices of phosphate rock. In this paper an analysis is given to recover phosphate from municipal wastewater for the elementary P-industry Thermphos International B.V. and the fertiliser industry Amsterdam Fertilizers B.V. in The Netherlands. Several scenarios are evaluated and the end products of these scenarios are compared to the quality required by both industries. From a Dutch study it became clear that all end products from the final sludge treatment do not provide a good source of secondary phosphate. As a consequence of this, the most preferred possibility for P-recovery is to extract phosphate before sludge goes to the final sludge treatment. Different scenarios can be selected based on the position of P-recovery in the WWTP configuration, the type of P-recovery product, and the precipitation technique. Local conditions will determine which scenario is the most expedient. Because it is more realistic to judge a practical situation instead of theoretical estimations based on literature, some local situations have to be assessed in sufficient detail to gain more feeling for the expenses and possible savings of P-recovery. One important actor that should be involved in the process management around P-recovery, is the national government. Especially, the Government have the responsibility for sustainable development and should have attention for some stimulation of P-recovery in The Netherlands. Water authorities and the P- and fertilizer industry made already some good steps.