Experimental study of inward freezing in circular and square pipes

This paper describes the results of an experimental study of the inward freezing of water in tubes of circular and square geometries. The temperature-time history is recorded using thermocouples, from which the progress of the freezing front is deduced. The results obtained pertain to the conditions of water not initially at freezing temperature, the outside surface temperature of the tube varying with time. Since the available theories assume liquid to be initially at freezing temperature and a constant sub-freezing temperature at the outside surface, a rigorous comparison is not possible. In order to make some sort of comparison, the sensible heat of water has been incorporated into the latent heat while the actual surface temperature variation has been replaced by its time-average value. Despite these approximations, the experimental results are in reasonable agreement with the theory.     

Knowledge based modelling of homologous proteins, part I: three-dimensional frameworks derived from the simultaneous superposition of multiple structures

An approach is described for modelling the three-dimensionalstructure of a protein from the tertiary structures of severalhomologous proteins that have been determined by X-ray analysis.A method is developed for the simultaneous superposition ofseveral protein molecules and for the calculation of an ‘averagestructure’ or ‘framework’. Investigation ofthe convergence properties of this method, in the case of bothweighted and unweighted least squares, demonstrates that bothgive a unique answer and the latter is robust for an homologousfamily of proteins. Multi-dimensional scaling is used to subgroupthe proteins with respect to structural homology. The frameworkcalculated on the basis of the family of homologous proteins,or of an appropriate subgroup, is used to align fragments ofthe known protein structures of high sequence homology withthe unknown. This alignment provides a basis for model buildingthe tertiary structure. Different techniques for using the frameworkto model the mainchain of various globins and an immunoglobulindomain in the structurally conserved regions are in vestigated.     

Free alpha-subunits of human chorionic gonadotropin in preeclampsia

OBJECTIVE: To investigate free alpha-human chorionic gonadotropin (hCG) as a marker of preeclampsia. METHODS: Four groups of patients were studied: normal pregnancies, preeclampsia, eclampsia and normal pregnant women <20 weeks' gestation. Patients were further divided according to parity and gestational age (< or =20, 21-30, 31-40 weeks). An immunoradiometric assay employing monoclonal antibodies specific for free alpha-hCG was used. RESULTS: A total of 313 patients were analyzed. Thirty-four patients < or =20 weeks' gestation were followed until delivery: five (14.7%) developed preeclampsia; none had abnormal alpha-hCG levels before onset of preeclampsia. Patients with preeclampsia (21-30 weeks' gestation) demonstrated a mean alpha-hCG level greater than that of normotensive controls but this was not statistically significant. Between 31 and 40 weeks' gestation, mean alpha-hCG levels in the hypertensive and control groups were 210.8 ng/ml and 115.8 ng/ml, respectively (P < 0.001). A stronger association was observed between alpha-hCG and preeclampsia with increasing gestational age (relative risk [RR] 2.07, 21-30 weeks; RR 3.02, 31-40 weeks) and severity (RR 4.51, mild; RR 12.15, severe; RR 16.88, eclampsia). CONCLUSION: There is a strong association between alpha-hCG and preeclampsia, nevertheless this test is unsuitable for predicting preeclampsia.     

Energy Cooperation with Sleep Mechanism in Renewable Energy Assisted Cellular HetNets

The emerging fifth generation (5G) and beyond radio access networks are expected to be extremely dense and heterogeneous as compared to the current networks, involving a large number of different classes of base stations (BSs), namely macro, micro, femto and pico BSs. Among several performance requirements 5G and beyond systems aim to achieve, energy efficiency is one of the crucial requirements. In order to achieve energy-efficient design in dense heterogeneous 5G networks, various approaches in terms of resource allocation, off-loading techniques, hardware solutions and energy harvesting are being considered. In this regard, this paper develops an energy usage optimization framework in a cellular heterogeneous network (HetNet) consisting of a central macro-BS and a number of micro-BSs, equipped with renewable energy sources (RESs) such as solar panels and wind turbines. The proposed framework incorporates an energy cooperation mechanism along with a sleep mechanism (BS ON/OFF switching), in which the BSs having lean traffic are put into a sleep mode and their traffic load gets shared by the central BS. The surplus harvested energy from RESs of the sleeping BSs can then be sold back to the grid. An optimization problem for maximizing the utilization of RES and minimizing the usage of the traditional sources, such as utility and generator, is formulated and this mixed integer non-linear programming problem is solved through an interior point method. The presented results for various HetNet sizes demonstrate the significant savings in the energy cost with the proposed RES-enabled HetNet sleep mechanism model over the conventional approaches.

     

On-chip deposition of carbon nanotubes using CMOS microhotplates

The direct deposition of carbon nanotubes on CMOS microhotplates is demonstrated in this paper. Tungsten microhotplates, fabricated on thin SOI membranes aside CMOS control circuitry, are used to locally grow carbon nanotubes by chemical vapour deposition. Unlike bulk heating of the entire chip, which could cause degradation to CMOS devices and interconnects due to high growth temperatures in excess of 500?°C, this novel technique allows carbon nanotubes to be grown on-chip in localized regions. The microfabricated heaters are thermally isolated from the rest of the CMOS chip as they are on the membranes. This allows carbon nanotubes to be grown alongside CMOS circuitry on the same wafer without any external heating, thus enabling new applications (e.g.?smart gas sensing) where the integration of CMOS and carbon nanotubes is required.     

Direction of arrival estimation of sources with intersecting signature in time–frequency domain using a combination of IF estimation and MUSIC algorithm

Time–frequency (TF) approaches are frequently employed for source localization at low signal to noise ratio. However, TF approaches fail to achieve the desired performance for sparsely sampled signals or signals corrupted by heavy noise in an under-determined scenario when sources are not TF separable. In this study, we propose a new TF method for direction of arrival (DOA) estimation of sources with closely spaced and overlapping TF signature. The proposed method uses a combination of a high-resolution time–frequency distribution and instantaneous frequency estimation method for extraction of sources with intersecting and closely spaced time–frequency signatures. Once sources are extracted, their DOAs are estimated using a well known multiple signal classification (MUSIC) algorithm. Experimental results demonstrate that the proposed source localization method achieves better performance as compared to the conventional time–frequency MUSIC algorithm.

     

Mechanical,morphological, thermal properties and hydrolytic degradation behavior of polylactic acid/polypropylene carbonate blends prepared by solvent casting

The preparation of polylactic acid (PLA) and polypropylene carbonate (PPC) blend films by using the solvent casting method is to improve the properties of pure PLA. The blends' mechanical and thermal properties, morphological as well as hydrolytic degradation behavior are evaluated. The tensile test proved that the increase of PPC from 0 wt% to 75 wt% could improve the elongation of pure PLA when the graph showed a significant increase of the elongation from 10% to 1000%. Scanning Electron Microscopy (SEM) supported the significant increase in elongation of the blends when it shows a definite phase separation in 75/25 PLA/PPC, where 25% of PPC has formed islands in the PLA matrix. Differential scanning calorimetry indicates the partial miscibility of the blends where two peaks of the glass transition temperature moved towards each other when the amount of PPC increases. Fourier transform infrared (FTIR) spectroscopy revealed a possible intermolecular interaction between two polymers, which affects the miscibility of the blends. Finally, the hydrolytic degradation test indicates that the degradation started from the PLA phase and the blends' degradation rate decrease as wt% of PPC increase.     

A robust and efficient automated docking algorithm for molecular recognition

A completely automated method is described for determining themost likely mode of binding of two (macro)moJecules from theknowledge of their three-dimensional structures alone. The methodis based on well-known graph theoretical techniques and hasbeen used successfully to determine and rationalize the bindingof a number of known macromolecular complexes. In this articlewe present results for a special case of the general molecularrecognition problem—given the information concerning theparticular atoms involved in the binding for one of the molecules,the algorithm can correctly identify the corresponding (contacting)atoms of the other molecule. The approach used can be easilyextended to the general molecular recognition problem and requiresthe extraction of maximal common subgraphs. In these studiesthe docking of the macromolecules was achieved without the aidof computer graphics or other visual aids. The algorithm hasbeen used to determine the correct mode of binding of a proteinantigen to an antibody in 100 min on a DEC micro VAX 3600     

Charge‐Transport Properties of F6TNAP‐Based Charge‐Transfer Cocrystals

The crystal structures of the charge‐transfer (CT) cocrystals formed by the π‐electron acceptor 1,3,4,5,7,8‐hexafluoro‐11,11,12,12‐tetracyanonaphtho‐2,6‐quinodimethane (F₆TNAP) with the planar π‐electron‐donor molecules triphenylene (TP), benzo[b]benzo[4,5]thieno[2,3‐d]thiophene (BTBT), benzo[1,2‐b:4,5‐b′]dithiophene (BDT), pyrene (PY), anthracene (ANT), and carbazole (CBZ) have been determined using single‐crystal X‐ray diffraction (SCXRD), along with those of two polymorphs of F₆TNAP. All six cocrystals exhibit 1:1 donor/acceptor stoichiometry and adopt mixed‐stacking motifs. Cocrystals based on BTBT and CBZ π‐electron donor molecules exhibit brickwork packing, while the other four CT cocrystals show herringbone‐type crystal packing. Infrared spectroscopy, molecular geometries determined by SCXRD, and electronic structure calculations indicate that the extent of ground‐state CT in each cocrystal is small. Density functional theory calculations predict large conduction bandwidths and, consequently, low effective masses for electrons for all six CT cocrystals, while the TP‐, BDT‐, and PY‐based cocrystals are also predicted to have large valence bandwidths and low effective masses for holes. Charge‐carrier mobility values are obtained from space‐charge limited current (SCLC) measurements and field‐effect transistor measurements, with values exceeding 1 cm² V^?1 s¹ being estimated from SCLC measurements for BTBT:F₆TNAP and CBZ:F₆TNAP cocrystals.