Polycephalin B and C: Unusual Tetramic Acids from Plasmodia of the Slime Mold Physarum polycephalum (Myxomycetes)

Illumination results in increased formation of metabolites 1 and 2 in the plasmodia of the slime mold Physarum polycephalum. This was determined from HPLC studies undertaken in the search for the photoactive substances involved in the “blue-light phenomenon”. The isolation and structure elucidation of 1 and 2 is described.     

Colloidal quantum dots conjugated with human serum albumin – interactions and bioimaging properties

Quantum dots, due to their unique optical properties, constitute significant materials for many areas of nanotechnology and bionanotechnology. This work presents a review of researches dedicated to the interaction between quantum dots (QDs) with human serum albumin (HSA) and human cell culture as important for nanomedicine applications. The optical properties of bio-nanocomplexes formed by nanoparticles including colloidal QDs (e.g., CdTe, CdS, CdCoS) and albumin are displayed. The absorption spectra show that adding HSA to colloidal QDs leads to a gradual decrease of absorption and broadening of the exciton structure. The photoluminescence quenching results indicate that the quenching effect of QDs on HSA fluorescence depends on the size and temperature. The nature of quenching is rather static, resulting in forming QD-HSA complexes. The CdTe QD-HSA complexes show chemical stability in a PBS buffer. Furthermore, it is stable in cytoplasm and suitable for cell labeling, tracking, and other bioimaging applications.     

An empirical study on the benefit of split loads with the pickup and delivery problem

Splitting loads such that the delivery of certain loads is completed in multiple trips rather than one trip has been shown to have benefit for both the classic Vehicle Routing Problem (VRP) and the Pickup and Delivery Problem (PDP). However, the magnitude of the benefit may be affected by various problem characteristics. In this paper, we characterize those real world environments in which split loads are most likely to be beneficial. Based on practitioner interest, we determine how the benefit is affected by the mean load size and variance, number of origins relative to the number of destinations, the percentage of origin–destination pairs with a load requiring service, and the clustering of origin and destination locations. We find that the magnitude of benefit is greatest for load sizes just over one half vehicle capacity as these loads can not be combined without splitting, while they are the easiest to combine on a vehicle with splitting; increases as the number of loads sharing an origin or destination increases because there are more potential load combinations to split at each stop; and increases as the average distance from an origin to a destination increases because splitting loads reduces the trips from origins to destinations.     

Approximation properties for generalized q-Bernstein polynomials

In this paper, we introduce the generalized q-Bernstein polynomials based on the q-integers and we study approximation properties of these operators. In special case, we obtain Stancu operators or Phillips polynomials.     

Millimeter scale variations in the isotopic composition of vein sulphide minerals in the Kupferschiefer deposits, Lubin area, SW Poland

A slice of black shale rock cut by various metal sulphide veins of different generations from the Kupferschiefer deposits of Lubin, Poland was subjected to bombardment in a Laser Microprobe Combustion Reactor to produce SO2 for S-isotope analyses. The delta34S values ranged from-22 to-29 per thousand consistent with previous findings using conventional IRMS and attributable to primary generation of H2S by bacterial sulphate reduction. Systematic trends in delta34S values of a few per mil over distances of the order of mm attest to low temperatures of mineralization with accompanying change in the isotope composition of the fluids due to kinetic or equilibrium isotope fractionation.     

Surface Studies on Glass Powders Used in Commercial Glass-Ionomer Dental Cements

The surface properties of three commercial ionomer glass powders, i.e., Fuji IX, Kavitan Plus and Chemadent G-J-W were studied. Samples were analyzed by X-ray fluorescence spectroscopy (XRF), and the density was determined by gas pycnometry. Morphology was studied using scanning electron microscopy (SEM) and laser diffraction (LD) technique, whereas low-temperature nitrogen sorption measurements determined textural parameters like specific surface area and pore volume. Thermal transformations in the materials studied were evaluated by thermogravimetric analysis (TGA), which was carried out in an inert atmosphere between 30 °C and 900 °C. XRF showed that Fuji IX and Kavitan Plus powders were strontium-based, whereas Chemadent G-J-W powder was calcium-based. Powders all had a wide range of particle sizes under SEM and LD measurements. Specific surface areas and pore volumes were in the range 1.42–2.73 m²/g and 0.0029 to 0.0083 cm³/g, respectively, whereas densities were in the range 2.6428–2.8362 g/cm³. Thermogravimetric analysis showed that the glass powders lost mass in a series of steps, with Fuji IX powder showing the highest number, some of which are attributed to the dehydration and decomposition of the polyacrylic acid present in this powder. Mass losses were more straightforward for the other two glasses. All three powders showed distinct losses at around 780 °C and 835 °C, suggesting that similar dehydration steps occur in all these glasses. Other steps, which differed between glass powders, are attributed to variations in states of water-binding on their surfaces.     

Vector measures and strict topologies

Let X be a completely regular Hausdorff space and Cb(X) be the space of all real-valued bounded continuous functions on X, endowed with the strict topology βσ. We study topological properties of continuous and weakly compact operators from Cb(X) to a locally convex Hausdorff space in terms of their representing vector measures. In particular, Alexandrov representation type theorems are derived. Moreover, a Yosida-Hewitt type decomposition for weakly compact operators on Cb(X) is given.     

Wavepacket Propagation in the Determination of Microscopic Eigenenergies: I: The Spectral Method

Examining the relationship between chemical structure and dynamics should be fundamental to the undergraduate study of microscopic systems. With this in mind wavepacket propagation, which is traditionally used in application to dynamical problems, is used here as the foundation for determining eigenenergies. The system is propagated in space and time from an initial wavepacket as in a traditional dynamical study. We then proceed to determine eigenenergies from the appearance of resonances in a spectrum of energies that is generated from the spatial projection of the wavepacket onto the initial wavepacket. Application of the spectral method is made to a classic electronic structure problem; resonances are observed at energies which match the known energy structure of the problem. Finally, the relevance of wavepacket propagation to the elucidation of structure and dynamics at the undergraduate level is discussed.     

Unit commitment in power generation – a basic model and some extensions

For the unit commitment problem in the hydro-thermal power system of VEAG Vereinigte Energiewerke AG Berlin we present a basic model and discuss possible extensions where both primal and dual solution approaches lead to flexible optimization tools. Extensions include staggered fuel prices, reserve policies involving hydro units, nonlinear start-up costs, and uncertain load profiles. This revised version was published online in June 2006 with corrections to the Cover Date.