Simplified Numerical and Analytical Approach for Solutes in Turbulent Flow Reacting with Smooth Pipe Walls

A large group of reactions that affect water quality in distribution networks occur on the pipe wall surface. Existing simulation models are usually based on cross-sectionally averaged variables that use mass-transfer coefficients derived for constant-concentration (Dirichlet) boundary conditions to account for cross-sectional variations. In the case of a first-order wall-demand problem, the boundary condition is however of Robin type. We derive a simple one-dimensional (1D) model for the radial concentration profile of a solute of arbitrary Schmidt number (Sc) reacting with pipe walls in a fully developed turbulent flow. A modified van Driest mixing length model was used to approximate the Reynolds-averaged velocity and eddy diffusivity. Numerical solutions of the 1D model agree well with a two-dimensional mass transport model and experimental data. An asymptotic solution for high Sc is derived, which is in excellent agreement with the 1D model for Sc>100. A comparison with the mass-transfer coefficients for constant-concentration boundary conditions shows that the differences between the two boundary conditions are small.     

Attentional retraining procedures: Manipulating early or late components of attentional bias?

According to cognitive models of anxiety disorders, attentional bias for threatening information is a vulnerability factor to the etiology and maintenance of anxiety. A recently developed methodology to reduce attentional bias has been found to reduce emotional reactivity and anxiety. The present study aimed at identifying the effects of this attentional bias reduction on early and later stages of threat processing. Undergraduates were allocated to an attentional bias reduction (n = 23) versus control condition (n = 25). It was found that attentional bias reduction influenced late but not early stages of threat processing. This finding is of theoretical importance in relation to studies on the causal role of attentional bias and emotional reactivity. Moreover, the present findings also bear relevance to the clinical application of attentional retraining procedures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Concentration of phenolic compounds from apple pomace extracts by nanofiltration at lab and pilot scale with a techno‐economic assessment

Apple pomace can be used as resource for the extraction of phenolic compounds with antioxidant properties. Pressing of apple in juice and pomace at lab scale in open air (aerobic) and under N₂ atmosphere (anaerobic) showed a recovery of phenolic compounds of 85% in juice and pomace after anaerobic pressing, compared to 43% after aerobic pressing, indicating loss of phenolic compounds by oxidation and the advantage of anaerobic over aerobic pressing. After a membrane screening and concentration test at lab scale, the commercial nanofiltration membrane NFX was selected to concentrate phenolic compounds in an ethanol : water extract of apple pomace. At pilot scale, the concencentration of 10 selected phenolic compounds and quinic acid increased from 59.5 mg/L in the ethanol : water extract to 1256.1 mg/L in the final retentate, that is, by a factor 21.1. The volume of the crude extract was reduced by a factor of 28.5 during the filtration, indicating some loss of phenolic compounds during pilot testing due to membrane fouling or oxidation of polyphenols. The pilot concentration test using a spiral‐wound membrane module showed good flux and concentration of phenolic compounds, indicating the technical feasibility of membrane technology for efficient concentration of polyphenols in an ethanol : water extraction solvent. Unfortunately, the extraction and concentration process was not economically feasible under the assumptions made.

Practical applications

The valorization of food waste for the production of high‐added value products is an increasingly hot topic. Phytochemicals are present in relatively low concentration in the fruit matrix, and concentration in the extraction solvent is necessary to develop an industrially relevant process. In this study, membrane filtration was selected for concentration due to its low energy consumption and mild processing conditions compared to other technologies. Membrane screening and testing at lab and pilot scale with techno‐economic assessment can be used by food and nutraceutical industries to evaluate membrane technology for concentration of phytochemicals extracted from agroindustrial by‐products.     

Determinants of survival in patients receiving dialysis in Libya

Maintenance dialysis is associated with reduced survival when compared with the general population. In Libya, information about outcomes on dialysis is scarce. This study, therefore, aimed to provide the first comprehensive analysis of survival in Libyan dialysis patients. This prospective multicenter study included all patients in Libya who had been receiving dialysis for >90 days in June 2009. Sociodemographic and clinical data were collected upon enrolment and survival status after 1 year was determined. Two thousand two hundred seventy‐three patients in 38 dialysis centers were followed up for 1 year. The majority were receiving hemodialysis (98.8%). Sixty‐seven patients were censored due to renal transplantation, and 46 patients were lost to follow‐up. Thus, 2159 patients were followed up for 1 year. Four hundred fifty‐eight deaths occurred, (crude annual mortality rate of 21.2%). Of these, 31% were due to ischemic heart disease, 16% cerebrovascular accidents, and 16% due to infection. Annual mortality rate was 0% to 70% in different dialysis centers. Best survival was in age group 25 to 34 years. Binary logistic regression analysis identified age at onset of dialysis, physical dependency, diabetes, and predialysis urea as independent determinants of increased mortality. Patients receiving dialysis in Libya have a crude 1‐year mortality rate similar to most developed countries, but the mean age of the dialysis population is much lower, and this outcome is thus relatively poor. As in most countries, cardiovascular disease and infection were the most common causes of death. Variation in mortality rates between different centers suggests that survival could be improved by promoting standardization of best practice.     

His-tags as Zn(II) binding motifs in a protein-based fluorescent sensor

Fluorescent indicators that allow real-time imaging of Zn(II) in living cells are invaluable tools for understanding Zn(II) homeostasis. Genetically encoded sensors based on fluorescence resonance energy transfer between fluorescent protein domains have important advantages over synthetic probes. We discovered that hexahistidine tags have a strong tendency to dimerize upon binding of Zn(II) in solution and we used this principle to develop a new protein-based sensor for Zn(II). Enhanced cyan and yellow fluorescent proteins were connected by long flexible peptide linkers and His-tags were incorporated at both termini of this fusion protein. The resulting sensor CLY9-2His allows the ratiometric fluorescent detection of Zn(II) in the nanomolar range. In addition, CLY9-2His is selective over the physiologically relevant metal ions Fe(II), Mn(II), Ca(II) and Mg(II). Our approach demonstrates the potential of using small peptides as metal-binding ligands in chelating fluorescent protein chimeras.     

The potential of electrospraying for hydrophobic film coating on foods

There is a continuous need for thinner edible coatings with excellent barrier properties, and this requires new application methods. Electrospraying is known to yield fine droplets of size down to 20 μm, giving the potential of very thin and even coatings. A single electrospraying nozzle was used to characterise droplet formation and investigate the formation of thin films on well-defined surfaces. The experimental droplet size was successfully described as a function of operational parameters and liquid properties using scaling relations. The influence of operating parameters as nozzle height and electrostatic potential were evaluated as well.Thin film deposition was experimentally investigated for sunflower oil electro-sprayed on a highly conductive (aluminium) and insulating target surface (Parafilm). For both aluminium foil and Parafilm the droplet deposition was found to be random. For aluminium foil, being a conductive target, this was expected as repellence between droplets on the surface and new droplets is low, due to charge leakage to the ground. For Parafilm, droplet repellence appeared so large that droplets deposited on larger empty spots or were even pushed away from the surface. To evaluate the film formation performance, Monte Carlo simulations were carried out, and it was found that the method is a useful tool to characterise droplet deposition and film formation characteristics.     

Pyrethrins Protect Pyrethrum Leaves Against Attack by Western Flower Thrips, <Emphasis Type="Italic">Frankliniella occidentalis</Emphasis>

Pyrethrins are active ingredients extracted from pyrethrum flowers (Tanacetum cinerariifolium), and are the most widely used botanical insecticide. However, several thrips species are commonly found on pyrethrum flowers in the field, and are the dominant insects found inside the flowers. Up to 80 % of western flower thrips (WFT, Frankliniella occidentalis) adults died within 3 days of initiating feeding on leaves of pyrethrum, leading us to evaluate the role of pyrethrins in the defense of pyrethrum leaves against WFT. The effects of pyrethrins on WFT survival, feeding behavior, and reproduction were measured both in vitro and in planta (infiltrated leaves). The lethal concentration value (LC50) for pyrethrins against WFT adults was 12.9 mg/ml, and pyrethrins at 0.1 % (w/v) and 1 % (w/v) had significantly negative effects on feeding, embryo development, and oviposition. About 20-70 % of WFT were killed within 2 days when they were fed chrysanthemum leaves containing 0.01-1 % pyrethrins. Chrysanthemum leaves containing 0.1 % or 1 % pyrethrins were significantly deterrent to WFT. In a no-choice assay, the reproduction of WFT was reduced significantly when the insects were fed leaves containing 0.1 % pyrethrins, and no eggs were found in leaves containing 1 % pyrethrins. Our results suggest that the natural concentrations of pyrethrins in the leaves may be responsible for the observed high mortality of WFT on pyrethrum.     

Provision and quality of dialysis services in Libya

Dialysis is entirely funded by the public health care sector in Libya. Access to treatment is unrestricted for citizens but there is a lack of local information and no renal registry to gather national data. This cross-sectional study aimed to investigate dialysis provision and practice in Libyan dialysis facilities in 2009. A structured interview regarding dialysis capacity, staffing and methods of assessment of dialysis patients, and infection control measures was conducted with the medical directors of all 40 dialysis centers and 28 centers were visited. A total of 2417 adult patients were receiving maintenance dialysis in 40 centers, giving a population prevalence of approximately 624 per million. Most dialysis units were located in the northern part of the country and only 12.5% were free-standing units. Only three centers offered peritoneal dialysis. One hundred ninety-two hemodialysis rooms hosted 713 functioning hemodialysis stations, giving a ratio of one machine to 3.4 patients. Around half of centers operated only two dialysis shifts per day. Nephrologist/internist to patient ratio was 1:40 and nurse to patient ratio was 1:3.7. We found a wide variation in monitoring of dialysis patients, with dialysis adequacy assessed only in a minority. Separate rooms were allocated for chronic viral infection seropositive patients in 92.5% of the units. In general, the provision of dialysis is adequate but several areas for improvement have been identified, including a need for implementation of guidelines, recruitment of more nephrologists, and the development of more cost-effective alternatives such as peritoneal dialysis and transplantation.     

A 186 to 212?GHz Downconverter in 90?nm CMOS

The design and measurements of a 200?GHz downconverter in 90?nm standard CMOS are presented. A positive conversion gain of +6.6?dB, a noise figure of 29.9?dB and an output bandwidth of 3?GHz are measured for an LO power of ?14.9?dBm. The conversion gain remains within 3?dB for an RF frequency between 186 and 212?GHz. Downconversion of BPSK and QPSK signals is demonstrated with eye diagrams and constellation plots with data rates over 4?Gbit/s. A mathematical analysis is made of the MOSFETs in the triode region and a new small-signal parameter κ is introduced, which enables the design of the mixing transistors for minimum conversion loss.