PCM storage for solar DHW: An unfulfilled promise?

Phase change materials (PCM) have been repeatedly proposed for use in solar domestic hot water (DHW) systems. PCM storage designs have been proposed, but no detailed evaluation has been made of the actual contribution of the PCM to the total heat storage under typical end-use conditions. In this work annual simulations were done to compare the performance of a storage tank with PCM to a standard tank without PCM. A model was constructed to describe the heat storage tank with and without PCM, the collector, pump, controller and auxiliary heater. Realistic environmental conditions and typical end-user requirements were imposed. Annual simulations were carried out for different sites, load profiles, different PCM volume fractions, and different kinds of PCM. The results of all simulation scenarios indicate that, contrary to expectations, the use of PCM in the storage tank does not yield a significant benefit in energy provided to the end-user. The main reason for this undesirable effect is found to be increased heat losses during nighttime due to reheating of the water by the PCM.     

One-step synthesis of hybrid magnetic material based on polyphenoxazine and bimetallic Co–Fe nanoparticles

Polymer Bulletin - A simple method for preparation of hybrid magnetic nanocomposites consisting of bimetallic Co–Fe nanoparticles and polyphenoxazine (PPOA) is described. The nanocomposites...     

Modified Hyaluronic Acid-Laminin-Hydrogel as Luminal Filler for Clinically Approved Hollow Nerve Guides in a Rat Critical Defect Size Model

Hollow nerve guidance conduits are approved for clinical use for defect lengths of up to 3 cm. This is because also in pre-clinical evaluation they are less effective in the support of nerve regeneration over critical defect lengths. Hydrogel luminal fillers are thought to improve the regeneration outcome by providing an optimized matrix inside bioartificial nerve grafts. We evaluated here a modified hyaluronic acid-laminin-hydrogel (M-HAL) as luminal filler for two clinically approved hollow nerve guides. Collagen-based and chitosan-based nerve guides were filled with M-HAL in two different concentrations and the regeneration outcome comprehensively studied in the acute repair rat sciatic nerve 15 mm critical defect size model. Autologous nerve graft (ANG) repair served as gold-standard control. At 120 days post-surgery, all ANG rats demonstrated electrodiagnostically detectable motor recovery. Both concentrations of the hydrogel luminal filler induced improved regeneration outcome over empty nerve guides. However, neither combination with collagen- nor chitosan-based nerve guides resulted in functional recovery comparable to the ANG repair. In contrast to our previous studies, we demonstrate here that M-HAL slightly improved the overall performance of either empty nerve guide type in the critical defect size model.     

GaN nanostructures-poly(vinyl alcohol) composite based hydrostatic pressure sensor device

The wide band-gap semiconductor material gallium nitride was synthesized using a one step microwave-assisted solution phase technique. The synthesized GaN nanocrystals showed an intense ultraviolet-blue emission typical of GaN materials. Hydrostatic pressure sensors were fabricated using a GaN/polyvinyl alcohol (PVA) composite film deposited onto an interdigitated electrode and studied by measuring the change in alternating current conductance of the devices at varied applied pressures. Three different GaN concentrations of 29, 50 and 67% were used. A very high sensitivity in the range 100–200 kPa was observed for these devices. The composite devices demonstrated both response and recovery times of less than 16 s.     

Biological Implications of the Ribosome's Stunning Stereochemistry

The ribosome's striking architecture is ingeniously designed for its efficient polymerase activity in the biosynthesis of proteins, which is a prerequisite for cell vitality. This elaborate architecture is comprised of a universal symmetrical region that connects all of the ribosomal functional centers involved in protein biosynthesis. Assisted by the mobility of selected ribosomal nucleotides, the symmetrical region provides the structural tools that are required not only for peptide bond formation, but also for fast and smooth successive elongation of nascent proteins. It confines the path along which the A‐tRNA 3′‐end is rotated into the P‐site in concert with the overall tRNA/mRNA sideways movement, thus providing the required stereochemistry for peptide bond formation and substrate‐mediated catalysis. The extreme flexibility of the nucleotides that facilitate peptide bond formation is being exploited to promote antibiotic selectivity and synergism, as well as to combat antibiotic resistance.     

Experimental determination of the matrix-to-fracture transfer functions for oil recovery by water imbibition

Unique determination of the parameters of the triple-exponential matrix-to-fracture transfer functions is of profound importance to accurately simulate waterflooding and determine sweep efficiency in naturally fractured reservoirs. To accomplish this task, two novel approaches are investigated. Firstly, to our knowledge, the first attempt is made to facilitate not only the function values and their derivative, but also the integral to uniquely determine the transfer function parameters from a suite of in-house imbibition data. Secondly, a random number-based algorithm is applied to uniquely compute the parameters, and its results are compared to those generated through a conventional, nonlinear optimization method using spreadsheet software. The inclusion of the random component helps alleviate the inherent tendency of parametric optimization type algorithms to converge to that possible solution, predefined through the guessed values assigned to the parameters as starting values.Through precisely and more importantly uniquely determining the parameters of the matrix-to-fracture transfer function, experimental imbibition data can be correctly matched and better transposed to field applications. The presented approach of simultaneous correlation of the function and its derivative and integral provides an effective method to scale from laboratory experiments to field applications. Comparative studies presented in this paper delineate the outstanding advantages of the presented approach over the previous and frequently utilized function correlation approaches, which do not generally yield unique determination of transfer function parameters. With the help of a mathematically sound, uniquely defined model, a variety of issues pertaining to spontaneous imbibition can be addressed and resulting problems remedied. One such area of application is underbalanced drilling, where precise and advance knowledge of a formation's imbibition behavior would allow for optimized design and minimized formation damage. Another area is exploitation from naturally fractured reservoirs, in the presence of a strong water drive or a waterflood. Detailed understanding of the mechanisms governing matrix, fracture, and fluid interactions will result in optimized development and exploitation strategies.     

A line search approach for high dimensional function optimization

This paper proposes a modified line search method which makes use of partial derivatives and re-starts the search process after a given number of iterations by modifying the boundaries based on the best solution obtained at the previous iteration (or set of iterations). Using several high dimensional benchmark functions, we illustrate that the proposed Line Search Re-Start (LSRS) approach is very suitable for high dimensional global optimization problems. Performance of the proposed algorithm is compared with two popular global optimization approaches, namely, genetic algorithm and particle swarm optimization method. Empirical results for up to 10,000 dimensions clearly illustrate that the proposed approach performs very well for the tested high dimensional functions.     

Characterization and differentiation of Italian Parma,San Daniele and Toscano dry-cured hams: A multi-disciplinary approach

This study aimed at characterizing the sensory quality of Italian PDO dry-cured Parma, San Daniele and Toscano hams, applying a multi-disciplinary approach. Ham sensory profile as well as physico-chemical, aromatic, morphological and textural characteristics was investigated. There was a great difference between Toscano ham and Parma and San Daniele hams, which were more similar even though differentiated. Toscano ham showed higher scores for pork-meat odor, saltiness, dryness, fibrousness and hardness; accordingly, this ham was described by a high NaCl content and by high values of instrumental hardness, cohesiveness, gumminess and chewiness. Parma ham was characterized by a cured flavor, whereas San Daniele ham showed a wider fatty area and higher pH values. Parma and San Daniele hams were also described by higher values of sweetness, RGB color values and water activity. Sensory characteristics evaluated by trained assessors were correlated to instrumental measures, indicating that instrumental devices can be effectively applied for dry-cured ham characterization.