Comparative genomics and mutagenesis analyses of choline metabolism in the marine Roseobacter clade

Choline is ubiquitous in marine eukaryotes and appears to be widely distributed in surface marine waters; however, its metabolism by marine bacteria is poorly understood. Here, using comparative genomics and molecular genetic approaches, we reveal that the capacity for choline catabolism is widespread in marine heterotrophs of the marine Roseobacter clade (MRC). Using the model bacterium Ruegeria pomeroyi, we confirm that the betA, betB and betC genes, encoding choline dehydrogenase, betaine aldehyde dehydrogenase and choline sulfatase, respectively, are involved in choline metabolism. The betT gene, encoding an organic solute transporter, was essential for the rapid uptake of choline but not glycine betaine (GBT). Growth of choline and GBT as a sole carbon source resulted in the re-mineralization of these nitrogen-rich compounds into ammonium. Oxidation of the methyl groups from choline requires formyltetrahydrofolate synthetase encoded by fhs in R.pomeroyi, deletion of which resulted in incomplete degradation of GBT. We demonstrate that this was due to an imbalance in the supply of reducing equivalents required for choline catabolism, which can be alleviated by the addition of formate. Together, our results demonstrate that choline metabolism is ubiquitous in the MRC and reveal the role of Fhs in methyl group oxidation in R.pomeroyi

Solution of the Schr\"odinger Equation for Quantum Dot Lattices with Coulomb Interaction between the Dots

The Schr\"odinger equation for quantum dot lattices with non-cubic, non-Bravais lattices built up from elliptical dots is investigated. The Coulomb interaction between the dots is considered in dipole approximation. Then only the center of mass (c.m.) coordinates of different dots couple with each other. This c.m. subsystem can be solved exactly and provides magneto- phonon like collective excitations. The inter-dot interaction is involved only through a single interaction parameter. The relative coordinates of individual dots form decoupled subsystems giving rise to intra-dot excitations. As an example, the latter are calculated exactly for two-electron dots. Emphasis is layed on qualitative effects like: i) Influence of the magnetic field on the lattice instability due to inter-dot interaction, ii) Closing of the gap between the lower and the upper c.m. mode at B=0 for elliptical dots due to dot interaction, and iii) Kinks in the single dot excitation energies (versus magnetic field) due to change of ground state angular momentum. It is shown that for obtaining striking qualitative effects one should go beyond simple cubic lattices with spherical dots. We also prove a more general version of the Kohn Theorem for quantum dot lattices. It is shown that for observing effects of electron- electron interaction between the dots in FIR spectra (breaking Kohn's Theorem) one has to consider dot lattices with at least two dot species with different confinement tensors.Comment: 11 figures included as ps-file

Two-Electron Quantum Dot in Magnetic Field: Analytical Results

Two interacting electrons in a harmonic oscillator potential under the influence of a perpendicular homogeneous magnetic field are considered. Analytic expressions are obtained for the energy spectrum of the two- and three-dimensional cases. Exact conditions for phase transitions due to the electron-electron interaction in a quantum dot as a function of the dot size and magnetic field are calculated.Comment: 22 pages (Latex file), 3 Postscript figures, to be published in Phys. Rev.B 55, N 20 (1997

Response to comments on “A numerical method to determine interdiffusion coefficients of Cu6Sn5 and Cu3Sn intermetallic compounds”

Comments have recently been made by Yuan et al. [1] to deny one statement in our paper [2], Eq. (21) in Wagner's paper [3] can be used to accurately calculate the integrated interdiffusion coefficient for an incremental diffusion couple only under the assumption of constant Molar volume for all phases. We respond here to explain how they misunderstood our mathematical deduction, made a mistake in deriving a couple of equations, falsely cited our work and employed unjustifiable assumption. As a result, we believe that their comments are invalid to deny our statement

Probing the Shape of Quantum Dots with Magnetic Fields

A tool for the identification of the shape of quantum dots is developed. By preparing a two-electron quantum dot, the response of the low-lying excited states to a homogeneous magnetic field, i.e. their spin and parity oscillations, is studied for a large variety of dot shapes. For any geometric configuration of the confinement we encounter characteristic spin singlet - triplet crossovers. The magnetization is shown to be a complementary tool for probing the shape of the dot.Comment: 11 pages, 4 figure

High-pressure batch reverse osmosis (RO) for zero liquid discharge (ZLD) in a Cr(III) electroplating process

A batch RO system was designed and built for high-pressure (120 bar) operation. The system was developed for a ZLD application involving treatment of metal plating wastewater from a Cr(III) electroplating process at a major industrial plant. Hybrid semi-batch/batch operation enabled a compact design to be achieved. To maximize water recovery without exceeding a set peak pressure, a method for controlling the switch point between semi-batch and batch phases was developed. The system was tested with feed representative of rinse water from the electroplating process. A range of feed concentrations (at 10–20× dilution of the plating bath), feed flows (0.21–0.46 m3/h), water fluxes (6–14 LMH) and water recoveries (87–95.7 %) were investigated. The system successfully recovered Cr(III) and restored its concentration to that of the electrolyte bath, thus meeting the requirements for reuse in the electroplating process. Rejection of most species was >99.8 %, sufficient for reuse of the permeate as rinse. However, rejection of boric acid was only 69–80 % such that a second RO pass may be needed to remove boric acid. Specific Energy Consumption was <2.25 kWh per m3 of treated rinse water, representing a 50-fold saving compared to the current method of treatment and disposal at the industrial plant

Organic and conventional tomato cropping systems.

Among several alternative agricultural systems have been developed, organic agriculture has deserved increasing interest from. The objective of this paper was comparing both organic (OS) and conventional (CS) tomato cropping systems for varieties Débora and Santa Clara, through an interdisciplinary study. The experiment was set up in a randomized blocks design with six replicates, in a dystrophic Ultisol plots measuring 25 ´ 17 m. Cropping procedures followed by either local conventional or organic growers practices recommendations. Fertilization in the OS was done with organic compost, single superphosphate, dolomitic limes (5L, 60 g, and 60 g per pit), and sprayed twice a week with biofertilizer. Fertilization in the CS was done with 200 g 4-14-8 (NPK) per pit and, after planting, 30 g N, 33 g K and 10.5 g P per pit; from 52 days after planting forth, plants were sprayed once a week with foliar fertilizer. In the CS, a blend of insecticides, fungicides and miticides was sprayed twice a week, after planting. In the OS, extracts of black pepper, garlic, and Eucalyptus; Bordeaux mixture, and biofertilizer, were applied twice a week to control diseases and pests. Tomato spotted wilt was the most important disease in the OS, resulting in smaller plant development, number of flower clusters and yield. In the CS, the disease was kept under control, and the population of thrips, the virus vector, occurred at lower levels than in the OS. Variety Santa Clara presented greater incidence of the viral disease, and for this reason had a poorer performance than 'Débora', especially in the OS. Occurrence of Liriomyza spp. was significantly smaller in the OS, possibly because of the greater frequency of Chrysoperla. The CS had smaller incidence of leaf spots caused by Septoria lycopersici and Xanthomonas vesicatoria. However, early blight and fruit rot caused by Alternaria solani occurred in larger numbers. No differences were observed with regard to the communities of fungi and bacteria in the phylloplane, and to the occurrence of weeds

Addition Spectra of Quantum Dots in Strong Magnetic Fields

We consider the magnetic field dependence of the chemical potential for parabolically confined quantum dots in a strong magnetic field. Approximate expressions based on the notion that the size of a dot is determined by a competition between confinement and interaction energies are shown to be consistent with exact diagonalization studies for small quantum dots. Fine structure is present in the magnetic field dependence which cannot be explained without a full many-body description and is associated with ground-state level crossings as a function of confinement strength or Zeeman interaction strength. Some of this fine structure is associated with precursors of the bulk incompressible states responsible for the fractional quantum Hall effect.Comment: 11 pages, 3 figures (available from [email protected]). Revtex 3.0. (IUCM93-010

Electronic States in Silicon Quantum Dots: Multivalley Artificial Atoms

Electronic states in silicon quantum dots are examined theoretically, taking into account a multivalley structure of the conduction band. We find that (i) exchange interaction hardly works between electrons in different valleys. In consequence electrons occupy the lowest level in different valleys in the absence of Hund's coupling when the dot size is less than 10 nm. High-spin states are easily realized by applying a small magnetic field. (ii) When the dot size is much larger, the electron-electron interaction becomes relevant in determining the electronic states. Electrons are accommodated in a valley, making the highest spin, to gain the exchange energy. (iii) In the presence of intervalley scattering, degenerate levels in different valleys are split. This could result in low-spin states. These spin states in multivalley artificial atoms can be observed by looking at the magnetic-field dependence of peak positions in the Coulomb oscillation.Comment: 18 pages, 5 figure

PI3K/AKT/mTOR pathway activation in actinic cheilitis and lip squamous cell carcinomas

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156448/2/jdv16420_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156448/1/jdv16420.pd