Coronary surgery on the beating heart under extracorporeal circulation in high-risk patients. An acceptable compromise?

Coronary artery surgery with cardioplegia in high risk patients carries a risk of myocardial ischaemia and, without cardiopulmonary bypass, is not always technically feasible. The authors assessed an alternative, surgery on the beating heart with haemodynamic assist by cardiopulmonary bypass in 43 consecutive patients with poor left ventricular function (mean ejection fraction: 0.26), evolving myocardial ischaemia or acute myocardial infarction, old age (mean: 79.5 years) and comorbid conditions. Results were assessed mainly on clinical criteria. In addition, 9 patients had pre- and post-cardiopulmonary bypass measurements of markers of myocardial ischaemia (troponine Ic) and systemic inflammation (interleukines 6 and 10, elastase). In 6 cases, right atrial biopsy was analysed for expression of messenger ribonucleic acid coding for heat shock protein (HSP) 70; the data were compared with those of patients operated under warm blood cardioplegia. There was one cardiac death and one myocardial infarction. Myocardial conservation was confirmed by the minimal increase in troponine Ic levels and the significant increase in HSP 70 in RNA suggesting myocardial adaptation to stress. On the other hand, the minimal concentrations of mediators of inflammation were not significantly changed. In selected high risk patients, coronary revascularisation on the beating heart under cardiopulmonary bypass could be a valuable alternative. It conserves the potentially deleterious effects of cardiopulmonary bypass but peroperative global myocardial ischaemia, an important factor in the aggressivity of cardiac surgery, is eliminated.     

Energy analysis of non-Newtonian nanofluid flow over parabola of revolution on the horizontal surface with catalytic chemical reaction

Nanofluids are special functional fluids, which are designed to reduce the loss of energy and maximize the transport of heat. The thermophoresis and Brownian motion of the particle are important factors in the transport of heat in these fluids. The rise in heat transport shows encouraging effects in control of dissipation of energy and reduces entropy generation. In the current study, two-dimensional non-Newtonian Casson nanofluid flow on an upper horizontal surface of a parabola is investigated. The impact of catalytic surface chemical reactions has been account also due to its industrial importance. For this flow problem, the governing equations are modeled using the law of conservation of mass, momentum, heat, and concentration equation. The fitting transformations are taken to change governing couple partial differential equations and domain into local similar ordinary differential equation and domain of [0,∞). Using the "RK4" approach with Newton's shooting schemes via MATLAB tools, the numerical solution of dimensionless governing equations is sorted. It is observed that the Casson fluid parameter caused a drop in temperature profile, and the chemical reaction parameter is the source of the rise in the temperature field.     

Performance of the dye‐sensitized solar cells fabricated using natural dyes from Ixora coccinea flowers and Cymbopogon schoenanthus leaves as sensitizers

In this study, the chlorophyll and anthocyanin natural dyes were extracted from Cymbopogon schoenanthus leaves and Ixora coccinea flowers, respectively. Thereafter, these dyes were used as sensitizers in the TiO₂‐based dye‐sensitized solar cells (DSSCs). Ten solvents were used for solubilizing the dyes. Amongst the 10 solvents, the ethanol showed the highest absorption spectra for the anthocyanin and chlorophyll molecules. Temperature significantly affected the yield of the natural dyes. It was seen that an optimal extraction temperature of 70°C and 80°C results to higher anthocyanin and chlorophyll yields, respectively. However, an extraction temperature above 70°C and 80°C has shown a sharply decrease in the anthocyanin and chlorophyll concentrations, respectively. Also, the solution of acidic extraction, especially with a pH value of 4, increased the dyes concentrations. As seen in the results, the chlorophyll‐sensitized DSSCs had 0.23% conversion efficiency (?), short‐circuit current (I_sc) of 0.9 mA/cm^–2, open‐circuit voltage (V_oc) of 0.51 V, and 49.13% fill factor (FF). Meanwhile, the anthocyanin‐sensitized DSSCs showed 0.16% ?, 0.4 mA/cm^–2 I_sc, 0.53 V V_oc, and 75.93% FF.     

Biclustering neighborhood-based collaborative filtering method for top-n recommender systems

Knowledge and Information Systems - We propose a novel collaborative filtering method for top- $$n$$ recommendation task using bicustering neighborhood approach. Our method takes advantage of local...     

Wave propagation in a generalized thermoelastic plate using eigenvalue approach

In the present work, we obtain a dispersion relation for Rayleigh–Lamb wave propagation in a plate of thermoelastic material. For this aim, we consider the theory of generalized thermoelasticity with one relaxation time. The thickness of the plate is taken to be finite and the faces of the plate are assumed to be isothermal and free from stresses. We obtain the analytical solution for the temperature, displacement components, and stresses using an eigenvalue approach. Finally, we derive a dispersion relation for the plate in closed form taking into account isothermal boundary conditions for wave mode propagation. To obtain the phase velocity and attenuation coefficients of propagating wave mode, we use the function iteration numerical scheme to solve the complex dispersion relation. The phase velocity and attenuation coefficients for the first five modes of waves are represented graphically for Lord–Shulman and classical coupled dynamical theories.     

Study of ethanol dehydrogenation reaction mechanism for hydrogen production on combustion synthesized cobalt catalyst

Cobalt nanoparticles synthesized via solution combustion synthesis were used to study the decomposition mechanism of ethanol for hydrogen production. Thermodynamic studies were conducted on the synthesis of cobalt nanoparticles using cobalt nitrate as a metal precursor in presence of different reducing agents; hydrazine, glycine, urea and citric acid. Thermodynamic results along with experimental characterizations show that the type and amount of fuel influence the adiabatic combustion temperature and the gases released during synthesis process affecting nanoparticle size, porosity and microstructure. The synthesized nanoparticles were activated by passing H₂ at 300 °C inside the reaction chamber before being used for studying the reaction pathway of catalytic dehydrogenation of ethanol. These studies indicate that cobalt catalyst is selective for aldehyde and acetate species along with the formation of H_2, H₂O and CO₂. Production of methane was also observed on cobalt surface at 400 °C. The spent catalyst nanoparticles were characterized after the reaction using XRD, SEM and TEM to analyze the particle size and its morphology. Results indicate a growth in particle size due to sintering, and carbon formation on the catalyst surface due to coking during ethanol dehydrogenation reaction.     

A simulation modeling for optimization of flat plate collector design in Riyadh, Saudi Arabia

A simulation of forced convection solar heated water system is presented. A computer program is developed consisting of independent subroutines, capable of handling the variation of the collector tube diameter, tube spacing, ambient conditions, material thermal properties, collector and system design optimization.The meteorological data of Riyadh were used as the input in the program to simulate the performance of the collector system. The output of the program is analyzed to optimize the system design in the Riyadh region. The results of the simulations are compared with experimental data. There is a good agreement between the predicted and measured values.     

Determination of bioclimatic comfort in Erzurum–Rize expressway corridor using GIS

In this study, topographical and climatical conditions are prescinded all along Erzurum–Rize expressway corridors to appoint the areas which have bioclimatic comfort in summer season (June, July, August). For this purpose, the climate data (temperature, relative humidity, wind speed) from nine different stations was entered in the digital data base. By dint of ArcGIS 9.1 software, climatic data were analysed and numerological maps were produced by Inverse Distance Weighted (IDW) interpolation method. As a method, bioclimatically comfortable areas consists of: relative humidity between 30 and 65%, temperature between 15 and 20 °C, and wind speed up to 5 m/s. The maps were scored as 0 for uncomfortable and 1 for comfortable and superposed, and bioclimatic comfort area (temperature: 1–relative humidity: 1–wind speed: 1) were determined. Besides, topographic factors were appreciated. As a result of this study, it is concerned that the area (452749 ha. % 63); beginning from south of the Mountains Mescit which is started by Black Sea coastline to Mountain Mescit (3230 m) is out of bioclimatic comfort region; the Erzurum depression (1758 m) beginning from the Mountains Mescit has been determined that area has bioclimatic comfort conditions. As a consequence, it is confirmed that one of the ideal area which has bioclimatic comfort is the Erzurum depression area in Turkey.     

Managing object oriented framework reuse

Reusing frameworks instead of libraries can cause subtle architectural changes in an application, calling for innovative management solutions. We relate our experience in managing the Knowledge-Based Software Assistant project and offer tips for buying, building and using frameworks. One of the promises of object-oriented software development is that organizations can get a significant return on development investment because the code is easier to reuse. Software project managers are often eager to take the OO plunge for that reason, but are uncertain about the management issues they will face. There is also the problem of choosing the best form of reuse. Library-based reuse, the traditional reuse form, is more popular than framework-based reuse, but we have found that framework-based reuse offers many more benefits with the right management approach. We describe the lessons we learned when building the Knowledge-Based Software Assistant/Advanced Development Model