Greenhouse gas emissions from building and operating electric power plants in the Upper Colorado River Basin

As demand for electricity increases, investments into new generation capacity from renewable and nonrenewable sources should include assessment of global (climate) change consequences not just of the operational phase of the power plants but construction effects as well. In this paper, the global warming effect (GWE) associated with construction and operation of comparable hydroelectric, wind, solar, coal, and natural gas power plants is estimated for four time periods after construction. The assessment includes greenhouse gas emissions from construction, burning of fuels, flooded biomass decay in the reservoir, loss of net ecosystem production, and land use. The results indicate that a wind farm and a hydroelectric plant in an arid zone (such as the Glen Canyon in the Upper Colorado River Basin) appear to have lower GWE than other power plants. For the Glen Canyon hydroelectric plant, the upgrade 20 yr after the beginning of operation increased power capacity by 39% but resulted in a mere 1% of the CO2 emissions from the initial construction and came with no additional emissions from the reservoir, which accounts for the majority of the GWE.     

Biofiltration of methyl tert-butyl ether vapors by cometabolism with pentane: modeling and experimental approach

Degradation of methyl tert-butyl ether (MTBE) vapors by cometabolism with pentane using a culture of pentane-oxidizing bacteria (Pseudomonas aeruginosa) was studied in a 2.4-L biofilter packed with vermiculite, an inert mineral support. Experimental pentane elimination capacity (EC) of approximately 12 g m(-3) h(-1) was obtained for an empty bed residence time (EBRT) of 1.1 h and inlet concentration of 18.6 g m(-3). For these experimental conditions, EC of MTBE between 0.3 and 1.8 g m(-3) h(-1) were measured with inlet MTBE concentration ranging from 1.1 to 12.3 g m(-3). The process was modeled with general mass balance equations that consider a kinetic model describing cross-competitive inhibition between MTBE (cosubstrate) and pentane (substrate). The experimental data of pentane and MTBE removal efficiencies were compared to the theoretical predictions of the model. The predicted pentane and MTBE concentration profiles agreed with the experimental data for steady-state operation. Inhibition by MTBE of the pentane EC was demonstrated. Increasing the inlet pentane concentration improved the EC of MTBE but did not significantly change the EC of pentane. MTBE degradation rates obtained in this study were much lower than those using consortia or pure strains that can mineralize MTBE. Nevertheless, the system can be improved by increasing the active biomass.     

Piezoelectric properties of collagen-nanocrystalline hydroxyapatite composites

In this paper we did a study of the physicochemical, dielectric and piezoelectric properties of anionic collagen and collagen-hydroxyapatite (HA) composites, considering the development of new biomaterials which have potential applications in support for cellular growth and in systems for bone regeneration. The piezoelectric strain tensor element d ₁₄, the elastic constant s ₅₅, and the dielectric permittivity ₁₁ were measured for the anionic collagen and collagen-HA films. For the collagen-HA composite film (Col-HACOM) the main peaks associated to the crystalline HA is present. For the nanocrystalline composite, nanometric HA powder (103 nm particle size) (HAN), obtained by mechanical milling were used. For the composite film (Col-HAN) the HA and CaH(PO₄)₂H₂O phases were detected. One can see that the HA powder (HAN) present the main peaks associated to crystalline HA. The IR spectroscopy measurements on HA-COM and HAN powders, Col-HACOM and Col-HAN composite films and collagen film (Col) presents the main resonances associated to the modes of (PO₄)^3–, (CO₃)^2–. The IR spectra of Collagen Film (Col) shows the bands associated to amide I (C=O), amide II (N–H) and amide III (C–N) vibrational modes. The scanning electron photomicrography of the Col-HACOM and Col-HAN films, respectively, shows deposits of HA on the surface of collagen. It also shows that HACOM crystals has a dense feature, whereas the HAN crystals has soft porous surface. Energy-dispersive spectroscopy (EDS) analysis showed that the main elements of the hybrid sponge were carbon, oxygen, calcium, and phosphorus. The EDS of HACOM crystal, present in the Col-HACOM composite showed a molar ratio Ca/P = 1.71, whereas the Col-HAN composite the molar ratio of calcium and phosphorus (Ca/P = 2.14) and the amount of carbon were greater. The piezoelectric strain tensor element d ₁₄ obtained for the anionic collagen was around 0.102 pC/N. The collagen composite with nanocrystalline HA crystals (Col-HAN) present a better result (d ₁₄ = 0.040 pC/N) compared to the composite with the commercial ceramic (d ₁₄ = 0.012 pC/N). This is an indication that the nanometric particles of HA present little disturbance on the organization of the collagen fibers in the composite. In this situation the nanometric HA are the best candidates in future applications of these composites.     

Quantitative oximetry of breast tumors: a near-infrared method that identifies two optimal wavelengths for each tumor

We present a noninvasive optical method to measure the oxygen saturation of hemoglobin in breast lesions. This method introduces the novel concept that the best choice of near-infrared wavelengths for noninvasive tumor oximetry consists of a wavelength pair (lambda1, lambda2) within the range 680-880 nm, where the specific values of lambda1 and lambda2 depend on the optical properties of the specific tumor under examination. Our method involves two steps: (1) identify the optimal wavelength pair for each tumor and (2) measure the tumor oxygenation using the optical data at the two selected wavelengths. We have tested our method by acquiring experimental optical data from turbid media containing cylindrical or irregularly shaped inhomogeneities and by computing theoretical data for the case of spherical lesions embedded in a highly scattering medium. We have found that our optical method can provide accurate and quantitative measurements of the oxygenation of embedded lesions without requiring knowledge of their size, shape, and depth.     

An enriched macro finite element for the static analysis of thick general quadrilateral laminated composite plates

This article presents the formulation of an enriched macro finite element based on the trigonometric shear deformation theory for the static analysis of symmetrically laminated composite plates. Shear correction factor is not required because this theory accounts for tangential stress-free boundary conditions on the plate boundary surfaces. The macro element is obtained using the principle of virtual work and Gram-Schmidt orthogonal polynomials as enrichment functions. The implementation of the obtained algorithm is simple and efficient, and allows studying general quadrilateral plates with a single macro element. Several examples are presented to show the capability and applicability of the developed formulation.     

Fibre distribution and tensile response anisotropy in sprayed fibre reinforced concrete

Sprayed steel fibre reinforced concrete (SSFRC) is a material that tends to present anisotropy, due to the action of the spraying process inducing preferential fibre orientation. Despite numerous applications worldwide since the 1980s, no study has been found of the assessment of fibre distribution and its influence on the residual tensile strength of SSFRC. This work addresess this issue from a quantitative standpoint through an experimental programme with specimens extracted in various orientations within a SSFRC panel. The fibre content and 3D orientation were quantified using the inductive method and correlated with an indirect tensile behaviour for the same specimen with the Barcelona test. The results confirm the high level of anisotropy of SSFRC. The fibre orientation number parallel to the spraying direction is three times bigger than that found in the perpendicular direction. Similar differences were observed between the residual tensile response measured in those directions. Comparison of test results suggest that the preferential fibre orientation creates weaker planes that favours the increase of crack opening at lower load levels.     

Coherence graphs

We study the consistency of a number of probability distributions, which are allowed to be imprecise. To make the treatment as general as possible, we represent those probabilistic assessments as a collection of conditional lower previsions. The problem then becomes proving Walley's (strong) coherence of the assessments. In order to maintain generality in the analysis, we assume to be given nearly no information about the numbers that make up the lower previsions in the collection. Under this condition, we investigate the extent to which the above global task can be decomposed into simpler and more local ones. This is done by introducing a graphical representation of the conditional lower previsions that we call the coherence graph: we show that the coherence graph allows one to isolate some subsets of the collection whose coherence is sufficient for the coherence of all the assessments; and we provide a polynomial-time algorithm that finds the subsets efficiently. We show some of the implications of our results by focusing on three models and problems: Bayesian and credal networks, of which we prove coherence; the compatibility problem, for which we provide an optimal graphical decomposition; probabilistic satisfiability, of which we show that some intractable instances can instead be solved efficiently by exploiting coherence graphs.     

Experimental analysis of a motorcycle semi-active rear suspension

The topic of this paper is the experimental analysis and development of a control system for a semi-active suspension in a 2-wheel vehicle. The control system is implemented via a semi-active electro-hydraulic damper located in the rear suspension of a motorbike. The entire design and analysis procedure is carried out: the semi-active damper is characterized; a wide range of control strategies is recalled and an innovative semi-active algorithm (Mix-1-Stroke) based on a single-sensor layout is proposed. The strategies are then implemented in the Electronic Control Unit of the motorbike. Tests, both on test-bench and on-road, are presented. The result is the comparative analysis of a wide portfolio of different suspension control strategies, which shows the effectiveness of the Mix-1-Sensor rationale.     

MODIS vegetation metrics as indicators of hydrological response in watersheds of California Mediterranean-type climate zones

Vegetation characteristics of a watershed can be important in estimating hydrological response variables (HRVs) such as streamflow (Q), evapotranspiration (ET), and river yield (Q/P). Quantifying the relationship between satellite-derived vegetation metrics and hydrological response to precipitation (P) has the potential to facilitate prediction of HRVs for ungauged watersheds, and/or aid in the assessment of watershed similarity as an initial phase of hydrological regionalization. The utility of Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data to estimate HRVs of watersheds at the regional scale (southern and central California) is tested in this study. An exhaustive statistical regression analysis was conducted to quantify the relationships between MODIS vegetation metrics and HRVs using both ordinary least squares and spatially varying parameter models. Additionally a confirmatory analysis was conducted to test the effect precipitation and potential evaporation have on the exploratory regression results. Results from both the exploratory and confirmatory analyses suggest that (1) while there are limitations in the water balance approach to estimating ET (errors associated with changes in storage and meteorological data are unknown), moderate statistical relationships exist between MODIS vegetation metrics and HRVs; (2) these relationships are heavily influenced by vegetation-precipitation relationships and general precipitation magnitudes; (3) relationships between MODIS metrics and precipitation/HRVs are strongest when drought conditions prevail; and (4) LAI has the strongest relationship with precipitation and HRVs compared to other MODIS vegetation metrics.