Dynamic Cell and Microparticle Control via Optoelectronic Tweezers

This paper reports on cell and microparticle manipulation using optically induced dielectrophoresis. Our novel optoelectronic tweezers (OET) device enables optically controlled trapping, transportation, and sorting via dielectrophoretic forces. By integrating a spatial light modulator and using direct imaging, arbitrary dynamic manipulation patterns are obtained. Here, we demonstrate manipulation functions, including particle collectors, single-particle traps, individually addressable single-particle arrays, light-defined particle channels, and size-based particle sorting. OET-induced particle manipulation velocities are analyzed as a function of the applied voltage, optical pattern linewidth, and single-particle trap dimensions.     

Comparative study of the electronic structure of natural and synthetic rubies using XAFS and EDAX analyses

We have studied the Cr-K-edge XANES and EXAFS in natural Indian rubies from two sources and a synthetic ruby at ESRF. Weight % of various constituents in them is determined using EDAX measurements. Taking the results from the three techniques together we are able to demonstrate their feasibility in quantitative study of precious stones.     

Capacity of RAKE reception with energy randomization

We consider a RAKE receiver for coherent binary orthogonal signaling over a frequency selective multipath Rayleigh fading channel. The receiver uses maximal-ratio combining such that the weight estimation errors are not independent of the additive noise. We find the capacity-achieving energy randomization scheme with two energy levels for the cases of imperfect and perfect channel estimates. We observe that the capacity-achieving probability gets closer to 1/2 with increase in the number of paths. We also show that the capacity is higher if channel estimates are perfect and that the channel estimation errors have more pronounced effect on the capacity at low signal-to-noise ratios.     

Periodic heat transfer and load levelling of heat flux through a PCCM thermal storage wall/roof in an air-conditioned building

This communication presents an investigation of the thermal behaviour of a phase changing component material (PCCM) wall/roof which is exposed on one side to periodic solar radiation and atmospheric temperature and on the other side is in contact with room air at constant temperature. A periodic heat transfer analysis for PCCM slab has been developed (assuming effective thermal properties of PCCM) to assess the load levelling of the periodic heat flux and thermal storage characteristics of a PCCM wall/roof. It is found that a PCCM wall of thickness which is even less than that of an ordinary masonry concrete wall is more desirable for providing efficient thermal energy storage and maximum load levelling and hence is suitable for providing excellent thermal comfort in an air-conditioned building. Both the load levelling and storage duration increase with the decrease of melting temperature and increase of the latent heat of fusion of the PCCM.     

Efficient presentation of phagocytosed cellular fragments on the major histocompatibility complex class II products of dendritic cells

Cells from the bone marrow can present peptides that are derived from tumors, transplants, and self-tissues. Here we describe how dendritic cells (DCs) process phagocytosed cell fragments onto major histocompatibility complex (MHC) class II products with unusual efficacy. This was monitored with the Y-Ae monoclonal antibody that is specific for complexes of I-Ab MHC class II presenting a peptide derived from I-Ealpha. When immature DCs from I-Ab mice were cultured for 5-20 h with activated I-E+ B blasts, either necrotic or apoptotic, the DCs produced the epitope recognized by the Y-Ae monoclonal antibody and stimulated T cells reactive with the same MHC-peptide complex. Antigen transfer was also observed with human cells, where human histocompatibility leukocyte antigen (HLA)-DRalpha includes the same peptide sequence as mouse I-Ealpha. Antigen transfer was preceded by uptake of B cell fragments into MHC class II-rich compartments. Quantitation of the amount of I-E protein in the B cell fragments revealed that phagocytosed I-E was 1-10 thousand times more efficient in generating MHC-peptide complexes than preprocessed I-E peptide. When we injected different I-E- bearing cells into C57BL/6 mice to look for a similar phenomenon in vivo, we found that short-lived migrating DCs could be processed by most of the recipient DCs in the lymph node. The consequence of antigen transfer from migratory DCs to lymph node DCs is not yet known, but we suggest that in the steady state, i.e., in the absence of stimuli for DC maturation, this transfer leads to peripheral tolerance of the T cell repertoire to self.     

Theoretical analysis of ammonia-water absorption cycles for refrigeration and space conditioning systems

This paper presents an investigation of an ammonia-water absorption cycle for solar refrigeration, airconditioning and heat pump operations at higher heat supply temperatures. The system consists of a solar driven generator, rectifier, condenser, evaporator, absorber and heat exchangers for preheating and subcooling within the system. A steady state thermodynamic cycle analysis based on mass and heat balances along with the state equations for the thermodynamic properties of the ammonia-water mixture has been carried out. A numerical computer simulation of the system with input component temperatures, refrigerant concentration/mass flow rate and effectiveness of the heat exchangers has been made to evaluate the relative heat transfer rates (i.e. coefficients of performance) and the mass flow rates for the cooling/heating modes. It is found that unlike the low generator temperature behaviour the coefficients of performance for both cooling and heating modes are reduced at higher generator temperatures. However, an increase of condenser temperature for each mode of operation improves the performance of the systems at higher generator temperatures. A choice for keeping the absorber temperature equal to/lower than that of the condenser is also predicted at lower/higher generator temperatures, respectively. In general the results are more pronounced for the refrigeration mode than for the heat pump mode and are least effective for the airconditioning mode.     

Solar thermal modelling of a non-airconditioned building: Evaluation of overall heat flux

This paper presents an investigation of the thermal behaviour of a non-airconditioned building with walls/roof being exposed to periodic solar radiation and atmospheric air while the inside air temperature is controlled by an isothermal mass, window and door in the walls of the room. The effects of air ventilation and infiltration, the heat capacities of the isothermal storage mass inside air and walls/roof, heat loss into the ground, and the presence/absence of the window/door have been incorporated in the realistic time dependent periodic heat transfer analysis to evaluate the overall heat flux coming into the room and the inside air temperature. A numerical computer model using typical weather data for Delhi has been made to appreciate the analytical results quantitatively. It is found that the heat fluxes through different walls have different magnitudes and phase lags w.r.t. the corresponding solair temperatures. The overall heat flux coming into the room as well as the room air temperature are sensitive functions of the number of air changes per hour, closing/opening of the window and the door ventilation. The effects of the heat capacity of the isothermal mass and the basement ground are found to reduce the inside air temperature swing and the presence of a window is found to increase the inside air temperature even when the window area is much smaller than the wall/roof area. The model presented would be an aid to a building architect for good thermal design of non-airconditioned buildings.     

Coating characteristics of electron beam cured Bisphenol A diglycidyl ether diacrylate-co-aliphatic urethane diacrylate resins

Electron beam (EB) was used to cure coatings of Bisphenol A diglycidyl ether diacrylate (BDGDA) containing varying proportions of aliphatic urethane diacrylate (AUA). The cured BDGDA-co-AUA polymer coatings were characterized by Fourier transformed infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), gel fraction and swelling estimation techniques. FTIR study showed that the coating formulations were completely cured at a dose of 420 kGy. The effect of AUA on the end use performance properties of BDGDA coating namely, abrasion resistance, specular gloss at 60° angle, tubular impact resistance, pencil hardness, pendulum hardness, scratch resistance, mar resistance, stain resistance, steam resistance and cigarette burn resistance was also investigated. It was observed that incorporation of urethane acrylate oligomer in the epoxy acrylate formulation improved abrasion resistance, gloss and impact resistance. However, scratch resistance, mar resistance and hardness of the BDGDA coatings decreased due to incorporation of AUA. All coating formulations exhibited excellent stains and steam resistance properties, but showed poor cigarette burn resistance.     

High-responsivity (Ga2Ge)100−x(Ga3Sb2)x (x = 15, 30, 45, 60) photodetection sensor for optoelectronic applications

Journal of Materials Science: Materials in Electronics - Electromagnetic signal detection for applications such as astronomy, product quality monitoring, health, and necessitates systems that are...