Community economic development : an approach for urban-based economies

vi, 203 p

Duality, thermodynamics, and the linear programming problem in constraint-based models of metabolism

It is shown that the dual to the linear programming problem that arises in constraint-based models of metabolism can be given a thermodynamic interpretation in which the shadow prices are chemical potential analogues, and the objective is to minimise free energy consumption given a free energy drain corresponding to growth. The interpretation is distinct from conventional non-equilibrium thermodynamics, although it does satisfy a minimum entropy production principle. It can be used to motivate extensions of constraint-based modelling, for example to microbial ecosystems.Comment: 4 pages, 2 figures, 1 table, RevTeX 4, final accepted versio

An assessment of upper mantle heterogeneity based on abyssal peridotite isotopic compositions

Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 114 (2009): B12203, doi:10.1029/2008JB006186.Abyssal peridotites, the depleted solid residues of ocean ridge melting, are the most direct samples available to assess upper oceanic mantle composition. We present detailed isotope and trace element analyses of pyroxene mineral separates from Southwest Indian Ridge abyssal peridotites and pyroxenites in order to constrain the size and length scale of mantle heterogeneity. Our results demonstrate that the mantle can be highly heterogeneous to <1 km and even <0.1 m length scales. Examination of Nd isotopes in relation to modal, trace, and major element compositions indicate that the length scales and amplitudes of heterogeneities in abyssal peridotites reflect both ancient mantle heterogeneity and recent modification by melting, melt-rock reaction and melt crystallization. The isotopic and trace element compositions of pyroxenite veins in this study indicate that they are not direct remnants of recycled oceanic crust, but instead are formed by recent melt crystallization. Combined with existing data sets, the results show that the average global isotopic composition of peridotites is similar to that of mid-ocean ridge basalts, though peridotites extend to significantly more depleted 143Nd/144Nd and 87Sr/86Sr. Standard isotope evolution models of upper mantle composition do not predict the full isotopic range observed among abyssal peridotites, as they do not account adequately for the complexities of ancient and recent melting processes.This research was supported by WHOI Academic Programs funding to J.M.W; EAR0115433 and EAR0106578 to N.S; OCE9907630, OCE0526905, and OPP0425785 to H.J.B.D; and COE-21 funding to E.N

Correlation between site preference of ternary Mn addition in LaAg and superconductivity

The results of an extensive investigation of structure, surface morphology, composition and the superconducting-normal phase diagram of a new unconventional superconductor LaAg1-cMnc with nominal composition c = 0.0, 0.025, 0.05, 0.1, 0.2 and 0.3, reveal the following. The alloys with c = 0, 0.025 and 0.05 are essentially single phase alloys with the actual Mn concentration, x, same as the nominal one, i.e., c = x, whereas in the alloys with c = 0.1, 0.2 and 0.3, the actual Mn concentration of the majority phase (crystalline grains) is x = 0.050(1), 0.080(1) and 0.100(1), respectively. The ternary Mn addition does not alter the CsCl structure of the parent compound LaAg. Neither a structural phase transition occurs nor a long-range antiferromagnetic order exists at any temperature within the range 1.8K < = T < = 50K in any of the Mn containing alloys. Mn has exclusive La (Ag) site preference in the alloy (alloys) with x = c = 0.025 (x < = 0.05 or c < = 0.1) whereas in the alloy with x = c = 0.05, Mn has essentially no site preference in that all the Mn atoms either occupy the La sites or the Ag sites. In the alloys (alloy) with x < = 0.05 (x = c = 0.025), substitution of Ag (La) by Mn at the Ag (La) sub-lattice sites in LaAg host gives rise to unconventional superconductivity (destroys the conventional phonon-mediated superconductivity prevalent in the parent LaAg compound).Comment: The manuscript has 25 pages that include the text, 2 Tables and 12 Figures. The manuscript contains unpublished results which are of paramount interest to the Condensed Matter Physics Community at large and particularly to those engaged in the pursuit of research in Unconventional Superconductivit

Timing and conditions of peak metamorphism and cooling across the Zimithang Thrust, Arunachal Pradesh, India

The Zimithang Thrust juxtaposes two lithotectonic units of the Greater Himalayan Sequence in Arunachal Pradesh, NE India. Monazite U–Pb, muscovite 40Ar/39Ar and thermobarometric data from rocks in the hanging and footwall constrain the timing and conditions of their juxtaposition across the structure, and their subsequent cooling. Monazite grains in biotite–sillimanite gneiss in the hanging wall yield LA-ICP-MS U–Pb ages of 16 ± 0.2 to 12.7 ± 0.4 Ma. A schistose gneiss within the high strain zone yields overlapping-to-younger monazite ages of 14.9 ± 0.3 to 11.5 ± 0.3 Ma. Garnet–staurolite–mica schists in the immediate footwall yield older monazite ages of 27.3 ± 0.6 to 17.1 ± 0.2 Ma. Temperature estimates from Ti-in-biotite and garnet–biotite thermometry suggest similar peak temperatures were achieved in the hanging and footwalls (~ 525–650 °C). Elevated temperatures of ~ 700 °C appear to have been reached in the high strain zone itself and in the footwall further from the thrust. Single grain fusion 40Ar/39Ar muscovite data from samples either side of the thrust yield ages of ~ 7 Ma, suggesting that movement along the thrust juxtaposed the two units by the time the closure temperature of Ar diffusion in muscovite had been reached. These data confirm previous suggestions that major orogen-parallel out-of-sequence structures disrupt the Greater Himalayan Sequence at different times during Himalayan evolution, and highlight an eastwards-younging trend in 40Ar/39Ar muscovite cooling ages at equivalent structural levels along Himalayan strike

The Cytotoxicity and Mode of Action of 2,3,4-Trisubstituted Pyrroles and Related Derivatives in Human Tmolt4 Leukemia Cells

4-Carbechoxy-l-methyl-2-phenacyl-3-phenylpyrrole (9), 4-carbethoxy-2-(4-methoxybcnzoyl)-3-(4-methoxyphcnyl)pyrrole (10) and 2-(4-methoxybenzoyl)-3,4-bis-(4-methoxyphenyl)pyrrole (11) proved to be potent cytotoxic agents against the growth of murine and human leukemias and lymphomas. Selective toxicity was demonstrated against the growth of solid tumors, e.g. human adenocarcinoma of the colon SW480 and ileum HCT-8, glioma U-87-MG, and rat UMR-106 osteosarcoma. A mode of action study in Tmolt4 leukemia cells demonstrated that the agents inhibited de novo purine synthesis at the regulatory sites PRPP-amido transferase, IMP dehydrogenase as well as dihydrofolate reductase resulting in significant inhibition of DNA synthesis in 60 min. Other biochemical sites which were affected significantly were thymidylate synthetase, DNA polymerase a, RNA polymerases, nucleoside kinase and ribonucleoside reductase