Synthesis and characterization of maltose fatty acid monoesters as biosurfactants

Maltose long-chain fatty acid esters (MFAE), esterified at the 6 and 6′ position, were synthesized with stearic, palmitic, myristic, and oleic groups. Synthesis yields were 15–20% based on initial maltose present, and structural confirmation was obtained using plasma desorption mass spectrometry and nuclear magnetic resonance spectroscopy. These surfactants have surface tensions in the range of 34–36 dyn/cm at their critical micelle concentrations (CMC) of approximately 10⁻⁵–10⁻⁶ mol/L. The increased chain lengths have a marked effect, reducing CMC values for MFAE by approximately three orders of magnitude over similar carbohydrate-based dodecyl chain sources. Within chain lengths between 14 and 18 carbons, the rate of change in CMC is significant and decreases with increasing chain length for MFAE. The melting points of MFAE are approximately 40°C, and the heat capacities range from 1.6 to 1.9 J/g·K. These numbers are comparable to those of sucrose esters, indicating their applicability in similar uses. However, because MFAE, unlike sucrose, possess an anomeric carbohydrate carbon position, these surfactants maintain their reducing nature and are susceptible to further derivatization. They are also synthesized from renewable, economical carbohydrates and lipids and may provide an excellent alternative to pertrochemical-derived products.     

Elastic Properties and Microcracking Behavior of Particulate Titanium Diboride–Silicon Carbide Composites

The spontaneous microcracking of particulate TiB₂–SiC composites is studied as a function of TiB₂ volume fraction. The degree of microcracking was examined by measuring elastic properties from room temperature to 1300°C. The results showed that only one composition contains microcracks. All other compositions did not microcrack regardless of TiB₂ volume fraction. This was attributed to the difference in the sintering aids. In particular, the Al₂O₃ sintering aid needed in these compositions had reacted with SiO₂ to form an amorphous grain boundary phase that allowed residual stresses to relax by viscous flow at moderate to high temperatures. The existence of this amorphous grain boundary phase was directly observed by transmission electron microscopy.     

The prediction of transport parameters in filamentous fermentation broths based on results obtained in pseudoplastic polymer solutions

Transport phenomena studies on single phase “model” fluids are of limited value in biochemical engineering if they cannot be translated to the heterogeneous systems encountered in real fermentation processes. In this paper we discuss the utility of polymer solutions as models of filamentous fermentation broths for evaluation of: pipeline friction factors and impeller power numbers (turbine and helical ribbon). To a first approximation, polymer solutions can serve as suitable models for the prediction of laminar flow pressure drop in pipelines and turbulent power consumption in stirred tanks. However, results obtained on polymer solutions do not directly apply to filamentous fermentation broths for predictions of laminar flow impeller power consumption and the transition point for turbulent flow in stirred tanks. These discrepancies are believed to result from the existence of a time dependent yield stress in filamentous fermentation broths.     

Peer-to-peer bichromatic reverse nearest neighbours in mobile ad-hoc networks

The increasing use of mobile communications has raised many issues of decision support and resource allocation. A crucial problem is how to solve queries of Reverse Nearest Neighbour (RNN). An RNN query returns all objects that consider the query object as their nearest neighbour. Existing methods mostly rely on a centralised base station. However, mobile P2P systems offer many benefits, including self-organisation, fault-tolerance and load-balancing. In this study, we propose and evaluate 3 distinct P2P algorithms focusing on bichromatic RNN queries, in which mobile query peers and static objects of interest are of two different categories, based on a time-out mechanism and a boundary polygon around the mobile query peers. The Brute-Force Search Algorithm provides a naive approach to exploit shared information among peers whereas two other Boundary Search Algorithms filter a number of peers involved in query processing. The algorithms are evaluated in the MiXiM simulation framework with both real and synthetic datasets. The results show the practical feasibility of the P2P approach for solving bichromatic RNN queries for mobile networks.     

Characterization of Ceramics by X-Ray and Neutron Small-Angle Scattering

This paper reviews some recent advances in small-angle X-ray and neutron scattering methods and their application to address complex issues in ceramic systems of technological importance. It is shown how small-angle scattering (SAS) can be applied to ceramic systems in order to extract statistically representative microstructure information (e.g., void volume fraction size distributions, internal surface areas, pore morphologies) that complements the information obtained from diffraction methods, X-ray microtomography, or electron microscopy. It is demonstrated how SAS studies provide insights, not obtainable by other means, on the processing–microstructure–property relationships that frequently govern technological performance.     

Chlorophyll and plankton of the Gulf coastal waters of Saudi Arabia bordering a desalination plant

As on land, plants are the real producers in the sea, and on them depend all marine living resources and the basic sustainability of ecosystems. Primary production is performed by chlorophyll-bearing plants ranging from the tiny phytoplankton to the giant kelps through the process ofphotosynthesis. Zooplankton play an important role as secondary producers, and together with phytoplankton they support the vast assemblages of marine food chain with all their diversity and complexity. Data on chlorophyll pigments, phytoplankton and zooplankton are regarded as a sound basis for environmental appraisal of ecosystems. This paper presents a set of data collected from the Saudi Arabian coastal waters near the desalination plants in AI-Jubail. Materials were collected from six different sites covering the intake and discharge zones during cruises carried out in 1997-1998. Analyses of chlorophyll pigments were made using the spectrophotometric method. Plankton samples were collected using a Nansen plankton net with a mesh size of 75 μ and analyzed following standard procedures. Chlorophyll a, b, c and phaeophytin are the most commonly occurring pigments in seawater. Their concentrations showed wide fluctuation. The phytoplankton community was composed of 35 genera representing the Diatoms, Dinoflagellates and blue- green algae. Zooplankton were composed ofProtozoa, Coelenterata, Ctenophora, Aschelminthes, Annelida, Mollusca, Arthropoda, Echinodermata and Chordata. Arthropoda, represented by Cladocera, Copepoda and Crustacean larvae, formed the largest group followed by Chordata. The distribution of phyto- and zooplankton was examined and discussed on a seasonal, annual and inter-annual basis. In terms of species, overall species composition was not affected by plant discharge. The study brings out a greater understanding of the changes experienced by biotic communities as a result of impingement, entrainment and entrapment consequent to water passage through the plant structures. The study reflects the ecological relationships that the phytoplankton and the zooplankton of the region possess with respect to intake and discharge. Further, the study has brought to light a very redeeming feature of the ecosystem to sustain its productivity and planktonic abundance. It was observed that seawater temperature, conductivity and total suspended solids did not act as limiting factors. Besides throwing much light on the little known biological aspects of desalination sites, the data provided constitute a significant addition to the knowledge base of marine living resources in an industrial zone of Gulf coastal waters.     

Preparation and Characterization of 17O-Enriched Alumina for Nuclear Fusion Damage Experiments

Alumina enriched in ¹⁷O was successfully fabricated from aluminum isopropoxide and water containing the ¹⁷O isotope. This material was necessary for an experiment to study the radiation damage expected in alumina exposed to a nuclear fusion reactor environment. The enrichment levels of specimens subjected to different preparation schedules were measured using a nuclear reaction analysis technique. Replacement of the ¹⁷O isotope in the ceramic by atmospheric oxygen occurred readily. Therefore, successful fabrication of suitably enriched alumina specimens required that all processing steps be performed under vacuum or inertgas environments. The optimum fabrication procedure produced enriched alumina specimens of >99.5% of theoretical density, ∽10-μm grain size, and a flexural strength of 280 MPa.     

Cracking and the Indentation Size Effect for Knoop Hardness of Glasses

The Knoop hardnesses of five glasses decreased with increasing load in accordance with the classic indentation size effect (ISE). At moderate loads, cracking dramatically altered the indentation sizes and the ISE trends in three of the five glasses. Cracked indentations were as much as 10 μm longer than uncracked indentations made under identical conditions. Diagonal length readings must be corrected for optical resolution limitations if low power lenses are used.     

Surface Preparation of Tantalum for Encapsulation and Adhesive Bonding

A number of methods of surface preparation of tantalum for encapsulation in silicone rubber and for structural adhesive bonding were explored. The only ones which could be generally useful were boiling for 24 hours in distilled water (28% improvement) or boiling for 4 hours in 20% sodium hydroxide solution followed by boiling for 2 hours in dilute hydrochloric acid (34% improvement). An alternative, which could sometimes be used, was heating in air for at least 2 hours at 100°C.     

Applications of laser Raman microprobe spectroscopy to the characterization of coals and cokes

Optical microscopy is widely used in the characterization of coals and cokes. This Paper shows that the laser Raman microprobe (MOLE) which combines an optical microscope and a Raman spectrometer can provide useful additional information. Three main areas were investigated: identification of minerals in coal and coke; structural characterization of coals and cokes; and the interaction of inorganic additives and coal. Where possible, the results were compared with conventional optical microscopy measurements whereby it was shown that the optical texture and Raman spectra of cokes are not closely related. The Raman spectra of high temperature cokes were used to estimate the size of microcrystalline regions.