A novel microfluidic high-throughput resistive pulse sensing device for cells analysis

Microfluidic impedance-based devices offer a simple method for counting and sizing particles and cells in fields of biomedical research and clinical diagnosis. In this work, we present design, fabrication and operational characteristics of a novel high throughput original MEMS-based Coulter counter. This microfluidic device possesses two sub channels including two pairs of coplanar Au/Cr electrodes in each channels which allows double detection of the particles simultaneously and increases the throughput. The present design provides minimizing the cross talk and obviating the need for hydrodynamic focusing of the sample particles by adjusting Y shape insulation obstacle in direction of flow. Moreover, reducing coincidence events and removing electrode polarization effect were purposed by applying optimum sizes for electrodes considering the ease of fabrication and low costs. The reliability of the novel device was evaluated for polystyrene particles and cancer cells in conductive solutions. Results, which were recorded as relative resistance pulses across four sensing zones, illustrate the capability of the double-channel proposed device in detecting, counting and sizing 10 and 20 µm polystyrene particles. The superiority of present design was proved by relative counting error of below 3 and 11% for the 10 µm and 20 µm particles, respectively and a throughput of hundreds particles per second. Aiming at demonstrating the functionality of the proposed device in the biomedical area, counting of SP2/0 cells was performed. The measured counting outputs for cells in the size range of 5.63–17.6 µm were validated with results of hemocytometer cell counter, with relative error less than 7%.

     

A new route for the direct synthesis of Al2O3/SiC nanopowder mixtures by the carbothermal reduction of parent oxides

The direct synthesis of Al₂O₃/SiC nanopowders from the parent oxides Al₂O₃ and SiO₂ through mullite carbothermal reduction as intermediate phase has been investigated. The effect of the amount of excess stoichiometric carbon (active charcoal, AC) as sole carbon source on the microstructure evolution has been studied. The effect of type of carbon source (AC, graphite (G), 50 wt % AC 50 wt % G mixture, 57 wt % AC 43 wt % G mixture) on the microstructure evolution was investigated using 30 wt % excess stoichiometric carbon. The effect of reaction temperature, reaction duration, initial green compact thickness, and carbon source on the mullite conversion, morphology, and surface area of the final powders has been thoroughly investigated. The calculated activation energy is in the range of 203–230 kJ mol^?1, depending on the carbon source used. The synergetic effect observed for the AC/G mixtures has been accordingly explained. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Computationally efficient decoding of LDPC codes

A computationally efficient algorithm for the decoding of low-density parity check codes is introduced. Instead of updating all bit and check nodes at each decoding iteration, the developed algorithm only updates unreliable check and bit nodes. A simple reliability criteria is developed to determine the active bit and check nodes per decoding iteration. Based on the developed technique, significant computation reductions are achieved with very little or no loss in the BER performance of the LDPC codes. The proposed method can be implemented with a slight modification to the sum-product algorithm with negligible additional hardware complexity.     

MBE Growth of lattice-matched ZnCdMgSe quaternaries and ZnCdMgSe/ZnCdSe quantum wells on InP substrates

We report the growth and characterization of a new wide bandgap II-VI alloy, Zn_xCd_yMg_1-x-ySe, grown lattice-matched to InP. High quality quaternary layers with bandgaps ranging from 2.4 to 3.1 eV were grown by molecular beam epitaxy. The bandgaps and lattice constants were measured using photoluminescence and single crystal Θ-2Θ scans. Quantum well structures with quaternary barriers and ZnCdSe wells were also grown, entirely lattice matched to InP. Their photoluminescence properties suggest that these materials are suitable for the design of visible semiconductor lasers spanning the blue, green, and yellow regions of the visible range. The absence of strain in these heterostructures is expected to improve the reliability of the materials in device applications.     

The effect of reliable prediction of final pressure during pressure equalization steps on the performance of PSA cycles

The present work aims at modeling the performance of isothermal PSA cycles for the production of H₂ from refinery fuel gas by introducing a more reliable calculation of the final pressure during the pressure equalization steps. The latter calculation is performed based on the law of conservation of mass in a system comprehending the depressurizing and pressurizing beds in contact. Single adsorbent (zeolite 5A) dual and six-bed PSA processes have been considered. The PSA cycle performance is compared with a conventional model considering an arithmetic mean for the final pressure during the pressure equalization steps (old model). It is shown that the new model predicts lower values for product purity and recovery when compared with the old model. The error in the estimation of the product recovery is larger than the corresponding value for product purity and may exceed 9%. It is shown that the error in the calculation of purity and recovery strongly depends on the number of beds. The error in the calculation of product recovery increases approximately two-fold increasing the number of beds from 2 to 6. Therefore, the present study shows that implementation of a more robust method for the evaluation of final pressure during the equalization steps is imperative for the development of new models of industrial PSA processes, especially for the number of beds exceeding 2.     

A new nano‐(2Li2O/MgO) catalyst/porous alpha‐alumina composite for the oxidative coupling of methane reaction

The present work discloses a new methodology for the production of detached nanorods of 2Li₂O/MgO catalyst particles on the internal surface of α‐Al₂O₃ porous supports to be used as efficient catalysts for the oxidative coupling of methane reaction (OCM). The peculiarity of our preparatory recipe is the success in producing “detached” nanosized entities on the support surface. The performance of the new catalyst/support system for the OCM reaction has been evaluated using a special reactor assembly with cross flow of methane and oxygen gas streams. Under the optimum process conditions, the yield of C product is 25% at an average reaction temperature of 750°C. Under the optimum conditions, the yield of ethylene reaches 8%. It is shown that the enhanced catalytic properties of the new catalyst/support composite may be attributed to nanoeffects. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Ethylbenzene disproportionation and p-xylene selectivity enhancement in xylene isomerization using high crystallinity desilicated H-ZSM-5

Desilication accompanied with minimum loss of crystallinity effect of a high alumina ZSM-5 zeolite on the isomerization reaction of ethylbenzene/xylene mixtures has been considered.Desilication was assessed through XRF,XRD,FTIR,TEM,nitrogen adsorption/desorption,NH_3-TPD,~(29)Si and~(27)Al MAS NMR analytical techniques.Desilication was accompanied with the creation of super acid sites.There exists a limit(Si/Al molar ratio of9.67)for keeping high crystallinity and obtaining improved catalytic performance.Desilication promotes ethylbenzene conversion by disproportionation and trans-alkylation reactions while the same reactions are limited for the xylene isomers.The p-xylene approach to equilibrium improves by more than 7% at 400℃ and a WHSV of 2 h~(-1)for the optimum sample with respect to the parent zeolite.At the same conditions,the optimum sample exhibits the maximum ethylbenzene conversion of 89%,i.e.more than 40%w.r.t.of the parent zeolite.However,the xylene yield decreases only 3%.     

Efficient light harvesting by NiS/CdS/ZnS NPs incorporated in C,N-co-doped-TiO2 nanotube arrays as visible-light sensitive multilayer photoanode for solar applications

Here, we report a significant enhancement in photo-electrochemical activity of co-doped/modified TiO₂ nanotube arrays (TNAs). First, TiO₂ nanostructures were sensitized with nitrogen and carbon via a single step/low cost anodization process and then modified with Nis/CdS/ZnS nano particles (NPs) by the successive ionic layer adsorption and reaction (SILAR) method at room temperature. Photo-electrochemical properties and physical/chemical characteristics of the pure and sensitized/modified TNAs were investigated using field emission scanning electron microscopy (FESEM), XRD, XPS and EDX, comprehensively. Electrochemical measurements and UV–Vis DRS spectroscopy of the photo-electrodes showed that co-doping with anions and modification with different NPs result in the broadening of the absorption region of visible light and the reduction of band gap energy. The mechanism responsible for the enhanced photo-electrochemical activity of the C, N-co-doped/NiS, CdS, ZnS NPs modified TNAs for the water reduction reaction using aqueous solutions of Na₂S/Na₂SO₃ as sacrificial electrolyte under the whole spectrum of simulated solar light irradiation has been presented. The highest photocurrent in presence of sacrificial agent (Na₂S/Na₂SO₃) was obtained as 18.79 mA/cm², for the optimized SILAR loading cycles and dopants concentration. Furthermore, a high incident photon to current efficiency (IPCE) of about 82% for the optimum photo-anode had been achieved. These results confirm that the C, N-co-doped/NiS, CdS, ZnS NPs modified TNAs nanocomposite may offer a promising strategy to attain maximum efficiency in a variety of solar energy conversion systems, along with reduced photo-corrosion in the semiconductor-semiconductor heterojunction.     

Revisiting Major Dry Periods by Rolling Time Series Analysis for Human-Water Relevance in Drought

Drought is increasingly gaining importance for society, humans, and the environment. It is analyzed commonly by the use of available hydroclimatic or hydrologic data with little in-depth consideration of specific major dry periods experienced over a region. Also, it is not a common practice to assess the probability of drought categories with a rolling time series and hence the changing knowledge for operational drought monitoring. A combination of such quantitative analysis with a comprehensive qualitative assessment of drought as a human-water relation aimed to fill this gap performing a case study in the Seyhan River Basin, Turkey. Six major dry periods were identified from the precipitation time series of 19 meteorological stations. Major dry periods were analyzed by rolling time series and full time series, and they were also analyzed individually. A major dry period could be important in terms of its duration while another in terms of its severity or intensity, and each with its own impact on the human-water relations that can be influential on the drought mitigation, management and governance. Significantly higher probabilities were calculated for extreme droughts with the use of individual major dry periods. An important outcome from the study is that drought is underestimated in practice with the sole use of the whole data record.