Methodological considerations for using thermal analysis in the characterization of soil organic matter

Thermal analysis is primarily used in the field of materials science, but has a long history in the geosciences. Soil organic matter (SOM) has received a great deal of recent scientific interest because of its role in the global carbon cycle. Conventional methods of characterizing SOM quality are unsatisfactory because they do not adequately capture the complete quality continuum that SOM comprises or the various mechanisms that act to stabilize it in the soil matrix. Thermal analysis techniques have the potential to capture this quality continuum, but are dependent on numerous experimental conditions that limit the comparability of results among different studies. Published methodology on thermal analysis of soils and sediments has largely focused on the characterization of the mineral component, while the organic component has received little attention. We tested several experimental conditions for their effects on the exothermic region of curves generated by thermal analysis of easily dispersed soil clay fractions and non-protected light-density particulate organic matter fractions isolated from the surface horizon of a forest soil. Results were found to be highly repeatable but strongly sensitive to crucible material, heating rate, and sample amount, and relatively insensitive to the use of a reference material. Thermal analysis is an important addition to the set of analytical tools used to characterize SOM quality because it provides direct, quantitative information of the energy potentially available for microbial metabolism. However, users will need to balance the needs of specific scientific objectives with the need for standardized methods and comparability between studies.     

Macrocyclic scaffolds derived from p-aminobenzoic acid

The regiospecific synthesis of C3 macrocyclic scaffolds possessing multiple different functional groups is described.     

Automated Synthesis of Oligosaccharides

The chemical synthesis of oligosaccharides with an automated solid‐phase synthesizer is described. An octenediol linker served to attach the growing oligosaccharide chain to the solid support, and the desired structures were cleaved from the support via olefin metathesis to afford a pentenyl glycoside. The automated syntheses of several important carbohydrates, including a pentarhamnoside, a proteoglycan linkage‐region tetrasaccharide, a phytoalexin elicitor dodecasaccharide, and a branched Leishmania lipophosphoglycan tetrasaccharide, were accomplished in higher overall yield and ca. 20 times faster than with solution‐phase methods.     

Etude comparative de la viscosite intrinseque des copolymeres bi et trisequences du styrene et de l'isoprene

The intrinsic viscosities of styrene-isoprene two- and three-block copolymers have been studied in a number of solvents as a function of molecular weight, composition and temperature. The behaviour of the three-block copolymers is similar in all points to that of the two-block. No conformational transition was observed between 10 and 60°. The intrinsic viscosities measured at 35° are close to the weighted average of the corresponding homopolymers of equal molecular weight. The Stockmayer-Fixman interaction parameters B are also close to the weighted average of the corresponding homopolymers. These results seem to indicate a structure with a limited number of heterocontacts.     

Design and fabrication of single mode rib waveguides using sol–gel derived organic–inorganic hybrid materials

Multi-layer buried rib waveguides were fabricated using sol–gel derived photopatternable organic–inorganic hybrid materials through multi-step spin coating and photolithography. A single mode circular waveguide at 1,550 nm was designed and fabricated using the equivalent refractive index method. Propagation loss in the order of 1.0 dB/cm was measured by cutback method. Waveguide thermal stability and thermo-optic coefficient were investigated using thermogravimetric analysis (TGA) and spectroscopic ellipsometry, respectively. Results suggest that the single mode waveguide can be used to develop thermal optical devices such as thermo-optic switches.     

First results from the XENON10 dark matter experiment at the Gran Sasso National Laboratory

The XENON10 experiment at the Gran Sasso National Laboratory uses a 15 kg xenon dual phase time projection chamber to search for dark matter weakly interacting massive particles (WIMPs). The detector measures simultaneously the scintillation and the ionization produced by radiation in pure liquid xenon to discriminate signal from background down to 4.5 keV nuclear-recoil energy. A blind analysis of 58.6 live days of data, acquired between October 6, 2006, and February 14, 2007, and using a fiducial mass of 5.4 kg, excludes previously unexplored parameter space, setting a new 90% C.L. upper limit for the WIMP-nucleon spin-independent cross section of 8.8x10(-44) cm2 for a WIMP mass of 100 GeV/c2, and 4.5x10(-44) cm2 for a WIMP mass of 30 GeV/c2. This result further constrains predictions of supersymmetric models.     

Maintenance Outsourcing Contracts for New Technology Adoptions

An external contractor receives a payment from a manufacturer for periodically performing preventive maintenance and for performing minimal repairs whenever process failures occur. Suppose a new technology will be available in the future, but the timing is uncertain. We propose specifying one or multiple time points in a maintenance contract, at which the manufacturer can adopt (switch to) the new technology, if it becomes available, and change the preventive maintenance schedule for the remaining time in the contract period. A model is developed to determine the value of using these (switch) points in a maintenance contract to the manufacturer. The numerical results show that, with a higher arrival rate of the new technology, the value becomes greater, and thus, the optimal switch point should be set earlier. Furthermore, if the new technology reduces maintenance costs, using switch points adds more value to a cost-plus-margin method than either the fixed payment or cost-plus-fixed-fee methods. On the other hand, if adopting the new technology results in higher maintenance costs, the value using switch points is higher for the fixed payment method.