Tip‐vortex breakdown of wind turbines subject to shear

Sheared velocity profiles pervade all wind‐turbine applications, thus making it important to understand their effect on the wake. In this study, a single wind turbine is modeled using the actuator‐line method in the incompressible Navier–Stokes equations. The tip vortices are perturbed harmonically, and the growth rate of the response is evaluated under uniform inflow and a linear velocity profile. Whereas previous investigations of this kind were conducted in the rotating frame of reference, this study evaluates the excitation response in the fixed frame of reference, thus necessitating a frequency transformation. It is shown that increasing the shear decreases the spatial growth rate in the upper half of the wake while increasing it in the lower half. When scaled with the local tip vortex parameters, the growth rate along the entire azimuth collapses to a single value for the investigated wavenumbers. We conclude that even though the tip‐vortex breakdown is asymmetric in sheared flow, the scaled growth rates follow the behavior of axisymmetric helical vortices. An excitation amplitude reduction by an order of magnitude extends the linear growth region of the wake by one radius for uniform inflow. In the sheared setup, the linear growth region is extended further in the top half than in the bottom half because of the progressive distortion of the helical tip vortices. An existing model to determine the stable wake length was shown to be in close agreement with the observed numerical results when adjusted for shear.     

Chloroquine in Africa: critical assessment and recommendations for monitoring and evaluating chloroquine therapy efficacy in sub-Saharan Africa

Chloroquine-resistant malaria is a major public health threat in sub-Saharan Africa. While a few countries have already replaced chloroquine as the first-line therapy for uncomplicated malaria or are in the process of doing so, other countries are faced with the complicated task of assessing the current status of drug resistance, making national policy-level decisions about whether to replace chloroquine or not, and initiating a monitoring system to track changes in the efficacy of malaria therapy. There is currently no standardized approach for collecting and interpreting data on therapy efficacy. There is also no agreement as to how much chloroquine resistance or treatment failure is acceptable and how much warrants a change in treatment policy. Using data collected in 10 sites in eastern and southern Africa between 1990 and 1996, we have assessed the therapeutic response to chloroquine and investigated predictors of clinical success or failure. Based on these experiences and analyses, a standardized protocol for in vivo studies of the efficacy of malaria therapy and for approaches to designing monitoring systems are proposed. The process of making policy-level decisions based on data collected by these systems is also discussed.     

Modelling of aircraft manufacturing cost at the concept stage

The work presented is concerned with the estimation of manufacturing cost at the concept design stage, when little technical information is readily available. The work focuses on the nose cowl sections of a wide range of engine nacelles built at Bombardier Aerospace Shorts of Belfast. A core methodology is presented that: defines manufacturing cost elements that are prominent; utilises technical parameters that are highly influential in generating those costs; establishes the linkage between these two; and builds the associated cost estimating relations into models. The methodology is readily adapted to deal with both the early and more mature conceptual design phases, which thereby highlights the generic, flexible and fundamental nature of the method. The early concept cost model simplifies cost as a cumulative element that can be estimated using higher level complexity ratings, while the mature concept cost model breaks manufacturing cost down into a number of constituents that are each driven by their own specific drivers. Both methodologies have an average error of less that ten percent when correlated with actual findings, thus achieving an acceptable level of accuracy. By way of validity and application, the research is firmly based on industrial case studies and practice and addresses the integration of design and manufacture through cost. The main contribution of the paper is the cost modelling methodology. The elemental modelling of the cost breakdown structure through materials, part fabrication, assembly and their associated drivers is relevant to the analytical design procedure, as it utilises design definition and complexity that is understood by engineers.     

Cytotoxic T cell reactivity and HLA-B35 binding of the variant Plasmodium falciparum circumsporozoite protein CD8+ CTL epitope in naturally exposed Kenyan adults

In this study, we have investigated the extent of natural polymorphism in the CD8+ cytotoxic T lymphocyte (CTL) determinant (amino acids 368-390) of circumsporozoite (CS) protein of Plasmodium falciparum field isolates from a holoendemic region of Kenya, and determined how this variation affects the CTL reactivities in clinically immune adults and binding specificities to human histocompatibility leukocyte antigen (HLA)-B35. Among the eight variant sequences that were found in this region, four were new and not seen in parasites from other geographical regions. When synthetic peptides corresponding to the eight variants were used to test the presence of CTL response in different donors, a different spectrum of CTL reactivity to these variants was noticed. While CTL from some donors recognized the P1 sequence (the most prevalent type of sequence) but not P8 (another major variant), other donors showed a reverse pattern of reactivity. Although none of the donors was able to recognize all the variants, CTL responses to all the eight variant sequences were found in this population. An octamer peptide with P1 sequence KPKDELDY in this polymorphic determinant was known to bind HLA-B35. When we tested the effect of natural variation in this octamer sequence on HLA-B35 binding, it became evident that SP13 with D --> N substitution retained its binding specificity to HLA-B35. On the other hand, the SP12 octamer sequence which had two substitutions did not bind HLA-B35. The most interesting finding was the observation that a D --> G substitution at position 374 rescued the binding ability of SP14, which otherwise could not bind to this HLA molecule due to E --> Q amino acid substitution at position 372. To our knowledge, this is the first demonstration showing that a natural polymorphism can rescue the binding specificity to an HLA-class I molecule that was lost due to another natural amino acid substitution. Altogether, these results demonstrate that natural polymorphism in the CS protein affects both the CTL reactivity and the ability to bind to HLA-B35.     

DETERMINATION OF REPEATABILITY AND REPRODUCIBILITY OF EBC ACCEPTED METHODS-II PALE MALT COLOUR,HOPS, SOLID ADJUNCTS

Methods for the determination of pale malt colour, hops analysis and solid adjuncts analysis published in Analytica EBC have been collaboratively tested by the European Brewery Convention Analysis Committee. Repeatability (r) and Reproducibility (R) are presented.     

Multilayered Cylindrical Triboelectric Nanogenerator to Harvest Kinetic Energy of Tree Branches for Monitoring Environment Condition and Forest Fire

Forest fires present a great threat as they can rapidly grow and become large, resulting in tragic loss of life and property when occurring near occupied land. Here a self‐powered fire alarm system based on a novel multilayered cylindrical triboelectric nanogenerator (MC‐TENG) that can produce electrical power for the detection sensors by harvesting the kinetic energy of moving tree branches in a forest is presented. The major parameters for harvesting the kinetic energy using the proposed MC‐TENG are investigated, including the number of triboelectric layers, the frequency, the amplitude of external excitation, and the orientation between motion direction and device configuration. The fabricated MC‐TENG results in a peak power of 2.9 mW and a maximum average power of 1.2 mW at a low frequency of 1.25 Hz. The integrated self‐powered forest fire alarm system, consisting of fire sensors, a carbon‐based micro‐supercapacitor, and the MC‐TENG, is demonstrated to be able to report fire risk or hazard efficiently, accurately, and robustly. This study provides a new solution to reduce the forest fire risk through a portable and sustainable alarm system by effectively harvesting kinetic energies in natural environment with TENG technology.     

N-myc oncogene amplification is correlated to trace metal concentrations in neuroblastoma cultured cells

N-myc oncogene amplification is a powerful predictor of aggressive behavior of neuroblastoma (NB), the most common solid tumor of the early childhood. Since N-myc overexpression – subsequent to amplification – determines a phenotype of invasiveness and metastatic spreading, it is assumed that N-myc amplified neuroblasts synthesize zinc metalloenzymes leading to tumor invasion and formation of metastases. In order to test a possible relation between N-myc oncogene amplification and trace metal contents in human NB cells, Fe, Cu and Zn concentrations have been measured by nuclear microprobe analysis in three human neuroblastoma cell lines with various degrees of N-myc amplification. Elemental determinations show uniform distribution of trace metals within the cells, but variations of intracellular trace metal concentrations with respect to the degree of N-myc amplification are highly dependent on the nature of the element. Zinc concentration is higher in both N-myc amplified cell lines (IMR-32 and IGR-N-91) than in the non-amplified cells (SK–N–SH). In contrast, intracellular iron content is particularly low in N-myc amplified cell lines. Moreover, copper concentrations showed an increase with the degree of N-myc amplification. These results indicate that a relationship exists between intracellular trace metals and N-myc oncogene amplification. They further suggest that trace metals very probably play a determinant role in mechanisms of the neuroblastoma invasiveness.     

An analytical model for spherulitic growth in fiber-reinforced polymers

An analytical model for the isothermal crystallization of fiber reinforced polymers is presented. The model is based on approximate expressions for the volume of intersection between a sphere and cylinder. These expressions are used to account for the effect of the fibers on the overall crystallization process. Expressions for the average volume of spherulites truncated by the fibers are computed. The crystallization process is divided into time frames during which specific types of fiber truncations are encountered. Three different time sequences for the occurrence of the truncations are also derived according to the fiber volume fraction. The depressing effect of the fibers on the overall crystallization process is demonstrated with simple examples. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1677–1687, 1998     

C-Src Is Activated by the EGF Receptor in a Pathway that Mediates JNK and ERK Activation by Gonadotropin-Releasing Hormone in COS7 Cells

The key participants in G-protein-coupled receptor (GPCR) signaling are the mitogen-activated protein kinase (MAPK) signaling cascades. The mechanisms involved in the activation of the above cascades by GPCRs are not fully elucidated. The prototypical GPCR is the receptor for gonadotropin-releasing hormone (GnRHR), which serves as a key regulator of the reproductive system. Here, we expressed GnRHR in COS7 cells and found that GnRHR transmits its signals to MAPKs mainly via Gαi and the EGF receptor, without the involvement of Hb-EGF or PKCs. The main pathway that leads to JNK activation downstream of the EGF receptor involves a sequential activation of c-Src and PI3K. ERK activation by GnRHR is mediated by the EGF receptor, which activates Ras either directly or via c-Src. Beside the main pathway, the dissociated Gβγ and β-arrestin may initiate additional (albeit minor) pathways that lead to MAPK activation in the transfected COS7 cells. The pathways detected are significantly different from those in other GnRHR-bearing cells, indicating that GnRH can utilize various signaling mechanisms for MAPK activation. The unique pathway elucidated here, in which c-Src and PI3K are sequentially activated downstream of the EGF receptor, may serve as a prototype of signaling mechanisms by GnRHR and additional GPCRs in various cell types.     

DETERMINATION OF MOISTURE AND FATTY SUBSTANCES CONTENTS OF SOLID ADJUNCTS

Two new methods—moisture at 130–133°C and fatty substances extracted by petroleum ether—were collaboratively tested by 14 laboratories (EBC and IOB Analysis Committee members and other laboratories). For moisture the following values were obtained in the range 12 to 15% m/m, repeatability=0.13% m/m and reproducibility=0.60% m/m. For fatty substances in the range 0.3 to 0.9% m/m the following values were obtained: repeatability=(0.06 m+0.02)% m/m and reproducibility=(0.14 m+0.09)% m/m. Both methods were accepted and will replace methods 6.1 and 6.4 respectively in Analytica EBC. The method for Fatty Substances will replace IoB methods 4.1.3 and 4.2.3. These modifications will become operative on 1 September, 1996.