A planar surface acoustic wave micropump for closed-loop microfluidics

We have designed and characterized a simple Rayleigh-surface acoustic wave-based micropump, integrated directly with a fully enclosed 3D microfluidic system, which improves significantly the pumping efficiency within a coupled fluid whilst maintaining planar integration of the micropump and microfluidics. We achieve this by exploiting the Rayleigh-scattering angle of surface acoustic waves into pressure waves on contact with overlaid fluids, by designing a microfluidic channel aligned almost co-linearly with the launched pressure waves and by minimizing energy losses by reflections from, or absorption within, the channel walls. This allows the microfluidic system to remain fully enclosed—a pre-requisite for point-of-care applications—removing sources of possible contamination, whilst achieving pump efficiencies up to several orders of magnitude higher than previously reported, at low operating powers of 0.5 W

An improved model of the <i>Trypanosoma brucei</i> CTP synthetase glutaminase domain-acivicin complex

The natural product acivicin inhibits the glutaminase activity of CTP synthetase and is a potent lead compound for drug discovery in the area of neglected tropical diseases, specifically trypanosomaisis. A 2.1 Å resolution crystal structure of the acivicin adduct with the glutaminase domain from Trypanosoma brucei CTP synthetase has been deposited in the Protein Data Bank and provides a template for structure-based approaches to design new inhibitors. However, our assessment of that data identified deficiencies in the model. We now report an improved and corrected inhibitor structure with changes to the chirality at one position, the orientation and covalent structure of the isoxazoline moiety and the location of a chloride in an oxyanion binding site that is exploited during catalysis. The model is now in agreement with established chemical principles and allows an accurate description of molecular recognition of the ligand and the mode of binding in a potentially valuable drug target.</p

Rapid cell separation with minimal manipulation for autologous cell therapies

The ability to isolate specific, viable cell populations from mixed ensembles with minimal manipulation and within intra-operative time would provide significant advantages for autologous, cell-based therapies in regenerative medicine. Current cell-enrichment technologies are either slow, lack specificity and/or require labelling. Thus a rapid, label-free separation technology that does not affect cell functionality, viability or phenotype is highly desirable. Here, we demonstrate separation of viable from non-viable human stromal cells using remote dielectrophoresis, in which an electric field is coupled into a microfluidic channel using shear-horizontal surface acoustic waves, producing an array of virtual electrodes within the channel. This allows high-throughput dielectrophoretic cell separation in high conductivity, physiological-like fluids, overcoming the limitations of conventional dielectrophoresis. We demonstrate viable/non-viable separation efficacy of > 98% in pre-purified mesenchymal stromal cells, extracted from human dental pulp, with no adverse effects on cell viability, or on their subsequent osteogenic capabilities

Surface acoustic wave microfluidic pumps for on-chip diagnostics

Most of point-of-care diagnostics and lab-on-chip devices that do on-chip sample preparation require active fluid actuation. In a laboratory setting, this is done via bulky benchtop equipment such as syringe pumps, peristaltic pumps and pressure systems. However, integration of a pumping unit onto the device allows for increased portability and decreased footprint of the device. Although there are multiple examples of realised micropumps based on different technologies, no one solution offers a combination of small footprint, low costs, scalable manufacturing and high performance required for point-of-care devices. Surface acoustic wave (SAW)-based micropumps are an exciting alternative to the current micropump systems due their small footprint and simplicity of manufacturing, yet many of the SAW micropumps presented to date suffer from poor performance and/or utilisation of open channels, which can be a problem regarding contamination. The SAW micropump demonstrated here uses a novel planar design and SAW scattering effects to significantly improve the pump performance and maintain closed channels, which is a pre-requisite for point-of-care applications. This thesis evaluates the fabrication of SAW devices and microfluidic channels using soft lithography. After evaluating the SAW device design concerning electrical characteristics both experimentally and theoretically, the first iteration of SAW micropumps utilising SAW momentum along the piezoelectric substrate is presented and characterised in terms of fluid flow velocity profiles and volume flow rates produced. Subsequently, a concept of a more efficient SAW micropump is presented based on out of the plane interaction between SAW and liquid. To fully utilise this interaction a protocol on the development of 3D microfluidic channels is introduced followed by a discussion on SAW-liquid coupling setting the scene for a demonstration of efficient and closed-loop SAW micropump that delivers pressure gradients up to an order of magnitude higher than the best to-date reported values at a similar input power levels. Finally, the newly developed pump is utilised in an on-chip flow cytometer to showcase the advanced flow manipulations, showing the potential applications of the SAW micropump beyond simple fluid actuation

Interaction of particles via solid interface: model and analysis

The paper addresses discrete element (DEM) models of the heterogeneous particulate solids where the normal interaction between two deformable spherical particles bonded via weaker solid interface is considered. The integral interaction model aimed for evaluation of the bond stiffness was developed, where analytical expressions of the stiffness parameters reflecting individual contribution of the two particles and of the interface properties are derived. Application of the developed DEM model to particulate solid with many particles is considered. The accuracy and the suitability of this approach are evaluated by considering refined 3D Finite Element analysis

Desenvolvimento de um modelo zerodimensional de uma zona para estudo dos parâmetros de combustão e desempenho de um motor de ignição por compressão

The purpose of the present work is to implement a code in MATLAB software to perform a simulation of the closed cycle of a compression ignition engine, obtaining the general parameters of performance, such as pressure curve in the cylinder, power, torque and specific consumption. The code consists in a zerodimensional simulation in which it is sought the solution of a set of ordinary differential equations that model the thermodynamic processes occurring with the gases in the cylinder of the engine. A control volume is considered, being limited by the inner walls of the cylinder and the conservation of mass and energy were applied to this volume. The gases are considered ideal and having uniform properties at all points within the control volume. Annands correlation is used to simulate the heat transfer to the cylinder walls and Wiebes Law is used to simulate the rate of burning of the air-fuel mixture. The numerical method used to solve the equations is the Euler Method. The validation/calibration of the model was done in three steps: first, for a given engine, the full load condition was fixed and the speed was varied (2000 rpm, 1800 rpm and 1700 rpm). These three points were simulated and the data obtained were compared with the experimental data. Then, for the same engine, the speed was set at 2000 rpm and the load was varied (full load, 60% full load and 40% full load). These three points were simulated and the data obtained were compared with the experimental data. Finally, the maximum power condition was set for two different engines. The data from these two points were then compared with the experimental data. The absolute percentage error (MAPE) between the simulated pressure curve and the experimentally obtained pressure curve was calculated, besides the error between the brake power given by the engine manufacturer and the brake power calculated by the simulation. For the brake power, the largest absolute error found was 3.07%. The MAPE between the curves ranged from 4.1% to 6.9%. The analysis of the values of the differences mentioned above and the fact that the simulation is completed in times of the order of seconds has led to the conclusion that the developed method/program is adequate to the proposal of providing the global performance parameters of a compression ignition engine in a practical and fast way, with low errorsO presente trabalho tem como objetivo geral implementar um código no programa MATLAB para realizar uma simulação do ciclo fechado de um motor de ignição por compressão, obtendo os parâmetros gerais de desempenho, como a pressão no cilindro, potência, torque e consumo específico. O código consiste em uma simulação zerodimensional de uma zona em que se busca a solução de um conjunto de equações diferenciais ordinárias que modelam os processos termodinâmicos que ocorrem com os gases no cilindro do motor. É considerado um volume de controle limitado pelas paredes do interior do cilindro e aplicadas a conservação de massa e de energia a este volume. Os gases são considerados ideais e tendo propriedades uniformes em todos os pontos no interior do volume de controle. A correlação de Annand é utilizada para a simulação da transferência de calor para as paredes do cilindro e a Lei de Wiebe utilizada para a simulação da taxa de queima da mistura ar-combustível. O método numérico utilizado para a solução das equações é o Método de Euler. A validação/calibração do modelo foi feita em três etapas: primeiro, para um dado motor, fixou-se a condição de plena carga e variou-se a rotação (2000 rpm, 1800 rpm e 1700 rpm). Estes três pontos foram simulados e os dados obtidos foram comparados com os dados experimentais. Depois, para o mesmo motor, fixou-se a rotação em 2000 rpm e variou-se a carga (plena carga, 60% da plena carga e 40% da plena carga). Estes três pontos foram simulados e os dados obtidos foram comparados com os dados experimentais. Por fim, fixou-se a condição de potência máxima para dois motores diferentes. Os dados destes dois pontos foram então comparados com os dados experimentais. Foram calculados a média do erro percentual absoluto () entre a curva de pressão simulada e a curva de pressão medida experimentalmente, além do erro entre a potência de eixo indicada pelo fabricante dos motores e a calculada pela simulação, em todos os pontos citados. Para a potência de eixo, a maior diferença encontrada, em módulo, foi de 3,07%. O entre as curvas variou de 4,1% a 6,9%. A análise dos valores das diferenças citados acima e o fato da simulação ser completada em tempos da ordem de segundos levou à conclusão de que o método/programa desenvolvido se adequa à proposta de fornecer os parâmetros globais de desempenho de um motor de ignição por compressão de forma prática, rápida e com baixos índices de err

High-resolution structure of the M14-type cytosolic carboxypeptidase from <em>Burkholderia cenocepacia </em>refined exploiting <em>PDB_REDO </em>strategies

A potential cytosolic metallocarboxypeptidase from Burk­holderia cenocepacia has been crystallized and a synchrotron-radiation microfocus beamline allowed the acquisition of diffraction data to 1.9 Å resolution. The asymmetric unit comprises a tetramer containing over 1500 amino acids, and the high-throughput automated protocols embedded in PDB_REDO were coupled with model–map inspections in refinement. This approach has highlighted the value of such protocols for efficient analyses. The subunit is constructed from two domains. The N-terminal domain has previously only been observed in cytosolic carboxypeptidase (CCP) proteins. The C-terminal domain, which carries the Zn(2+)-containing active site, serves to classify this protein as a member of the M14D subfamily of carboxypeptidases. Although eukaryotic CCPs possess deglutamylase activity and are implicated in processing modified tubulin, the function and substrates of the bacterial family members remain unknown. The B. cenocepacia protein did not display deglutamylase activity towards a furylacryloyl glutamate derivative, a potential substrate. Residues previously shown to coordinate the divalent cation and that contribute to peptide-bond cleavage in related enzymes such as bovine carboxypeptidase are conserved. The location of a conserved basic patch in the active site adjacent to the catalytic Zn(2+), where an acetate ion is identified, suggests recognition of the carboxy-terminus in a similar fashion to other carboxypeptidases. However, there are significant differences that indicate the recognition of substrates with different properties. Of note is the presence of a lysine in the S1′ recognition subsite that suggests specificity towards an acidic substrate

Correspondence Between Reliability of Rental Flat Building and Space Needs

Flats for rent need to be designed so that residents move comfortably and can save themselves in times of disaster. This research was conducted with the aim of knowing the spaces needed by the occupants by taking into account the reliability of the building-safety and comfort. Some aspects of building reliability are motion comfort and safety. Data was collected by an online questionnaire, which was distributed to residents using non-random sampling. The collected text data was analyzed by content analysis. From the results of the analysis revealed that residents tend to be comfortable moving in rental residential units. Residents need a secondary space that is a shelf and work space. Storage space represents the meaning of storage of small items. Work, study and storage of equipment represent the meaning of workspace needs. Residents need some secondary space in a residential unit that has aspects of motion comfort and security during disaster evacuation. Motion comfort mainly represents a little furniture, has storage space, and doesn't interfere with activities like sitting and watching television. The number of residents felt safe moving when disaster evacuation in vertical housing was almost the same as the number of residents who felt the evacuation route was not ideal. Easy access is achieved, wide circulation room, near the emergency stairs is represented by the meaning of feeling safe moving during a disaster evacuation. There is no special emergency ladder, narrow circulation space, the condition of a damaged staircase at the time of disaster evacuation is represented by meaning not ideal. This study found a significant relationship between the reasons for motion comfort and the presence of space requirements. There is no significant relationship between disaster evacuation security and secondary space requirements

Loading characteristics of weight stack machines

The load characteristics of the weight stack machines, where the resistance is generated by inertia of the stack of masses, are the subject of the paper. The method and means of experimental research are described. The dependencies of inertial resistance load upon the rate of exercises and the stack weight are determine