Changes in the carbon balance of tropical forest: evidence from long-term plots

The role of the world’s forests as a “sink” for atmospheric carbon dioxide is the subject of active debate. Long-term monitoring of plots in mature humid tropical forests concentrated in South America revealed that biomass gain by tree growth exceeded losses from tree death in 38 out of 50 neotropical sites. These forest plots have accumulated 0.71 + 0.34 tons of carbon per hectare per year in recent decades. The data suggest that neotropical forests may be a significant carbon sink, reducing the rate of increase in atmospheric CO2

Casimir force on a piston

We consider a massless scalar field obeying Dirichlet boundary conditions on the walls of a two-dimensional L x b rectangular box, divided by a movable partition (piston) into two compartments of dimensions a x b and (L-a) x b. We compute the Casimir force on the piston in the limit L -> infinity. Regardless of the value of a/b, the piston is attracted to the nearest end of the box. Asymptotic expressions for the Casimir force on the piston are derived for a << b and a >> b.Comment: 10 pages, 1 figure. Final version, accepted for publication in Phys. Rev.

Row-switched states in two-dimensional underdamped Josephson junction arrays

When magnetic flux moves across layered or granular superconductor structures, the passage of vortices can take place along channels which develop finite voltage, while the rest of the material remains in the zero-voltage state. We present analytical studies of an example of such mixed dynamics: the row-switched (RS) states in underdamped two-dimensional Josephson arrays, driven by a uniform DC current under external magnetic field but neglecting self-fields. The governing equations are cast into a compact differential-algebraic system which describes the dynamics of an assembly of Josephson oscillators coupled through the mesh current. We carry out a formal perturbation expansion, and obtain the DC and AC spatial distributions of the junction phases and induced circulating currents. We also estimate the interval of the driving current in which a given RS state is stable. All these analytical predictions compare well with our numerics. We then combine these results to deduce the parameter region (in the damping coefficient versus magnetic field plane) where RS states can exist.Comment: latex, 48 pages, 15 figs using psfi

Amine Templated Zinc Phosphates Phases for Membrane Separations

This research is focused on developing inorganic molecular sieve membranes for light gas separations such as hydrogen recovery and natural gas purification, and organic molecular separations, such as chiral enantiomers. The authors focus on zinc phosphates because of the ease in crystallization of new phases and the wide range of pore sizes and shapes obtained. With hybrid systems of zinc phosphate crystalline phases templated by amine molecules, the authors are interested in better understanding the association of the template molecules to the inorganic phase, and how the organic transfers its size, shape, and (in some cases) chirality to the bulk. Furthermore, the new porous phases can also be synthesized as thin films on metal oxide substrates. These films allow one to make membranes from organic/inorganic hybrid systems, suitable for diffusion experiments. Characterization techniques for both the bulk phases and the thin films include powder X-ray diffraction, TGA, Scanning Electron Micrograph (SEM) and Electron Dispersive Spectrometry (EDS)

Long range facial image acquisition and quality

Abstract This chapter introduces issues in long range facial image acquisition and measures for image quality and their usage. Section 1, on image acquisition for face recognition discusses issues in lighting, sensor, lens, blur issues, which impact short-range biometrics, but are more pronounced in long-range biometrics. Section 2 introduces the design of controlled experiments for long range face, and why they are needed. Section 3 introduces some of the weather and atmospheric effects that occur for long-range imaging, with numerous of examples. Section 4 addresses measurements of “system quality”, including image-quality measures and their use in prediction of face recognition algorithm. That section introduces the concept of failure prediction and techniques for analyzing different “quality ” measures. The section ends with a discussion of post-recognition ”failure prediction ” and its potential role as a feedback mechanism in acquisition. Each section includes a collection of open-ended questions to challenge the reader to think about the concepts more deeply. For some of the questions we answer them after they are introduced; others are left as an exercise for the reader. 1 Image Acquisition Before any recognition can even be attempted, they system must acquire an image of the subject with sufficient quality and resolution to detect and recognize the face. The issues examined in this section are the sensor-issues in lighting, image/sensor resolution issues, the field-of view, the depth of field, and effects of motion blur

Relativistic Contributions to Deuteron Photodisintegration in the Bethe-Salpeter Formalism

In plane wave one-body approximation the reaction of deuteron photodisintegration is considered in the framework of the Bethe-Salpeter formalism for two-nucleon system. Results are obtained for deuteron vertex function, which is the solution of the homogeneous Bethe-Salpeter equation with a multi-rank separable interaction kernel, with a given analytical form. A comparison is presented with predictions of non-relativistic, quasipotential approaches and the equal time approximation. It is shown that important contributions come from the boost in the arguments of the initial state vertex function and the boost on the relative energy in the one-particle propagator due to recoil.Comment: 29 pages, 6 figure

Review of Dental Impression Materials

Major advances in impression materials and their application have occurred during the last decade, with greater emphasis being placed on rubber impression materials than on dental compound, zinc oxide-eugenol, and agar and alginate. Of particular interest has been the effect of disinfection solutions on the qualities of impressions and the biocompatibility of impression materials. The principal advance in hydrocolloids has been the introduction of the agar/alginate impression technique, which has simplified the procedure and improved the quality of gypsum dies compared with those prepared in alginate impressions. The tear strength of some alginates has been improved, and some have been formulated so that the powder is dustless, thus reducing the health hazard as a result of patient inhalation of dust during the dispensing process. Polyether and silicone impression materials have been modified so that the working time, viscosity, and flexibility of the polyethers have been improved and, with the introduction of addition silicones, their accuracy has become exceptional. Although the early addition silicones liberated hydrogen after setting, thus delaying the pouring of models and dies, most addition silicones have been improved so that no hydrogen is released and dies can be poured immediately. The introduction of automatic mixing systems for addition silicones has simplified their manipulation, has reduced the number of voids in impressions, and has reduced the amount of material wasted. The incorporation of surfactants into addition silicones has made them hydrophilic, with wetting properties similar to those of polyethers, and has made pouring bubble-free gypsum dies easier. This review is confined to published and unpublished information of the past decade. It will also suggest trends that should be anticipated in the near future based on this information. The review will not present information developed before 1975, which is available in several textbooks on dental materials by Craig (1985a), Phillips (1982), and Williams and Cunningham (1979).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66604/2/10.1177_08959374880020012001.pd

Gravitational Lensing at Millimeter Wavelengths

With today's millimeter and submillimeter instruments observers use gravitational lensing mostly as a tool to boost the sensitivity when observing distant objects. This is evident through the dominance of gravitationally lensed objects among those detected in CO rotational lines at z>1. It is also evident in the use of lensing magnification by galaxy clusters in order to reach faint submm/mm continuum sources. There are, however, a few cases where millimeter lines have been directly involved in understanding lensing configurations. Future mm/submm instruments, such as the ALMA interferometer, will have both the sensitivity and the angular resolution to allow detailed observations of gravitational lenses. The almost constant sensitivity to dust emission over the redshift range z=1-10 means that the likelihood for strong lensing of dust continuum sources is much higher than for optically selected sources. A large number of new strong lenses are therefore likely to be discovered with ALMA, allowing a direct assessment of cosmological parameters through lens statistics. Combined with an angular resolution <0.1", ALMA will also be efficient for probing the gravitational potential of galaxy clusters, where we will be able to study both the sources and the lenses themselves, free of obscuration and extinction corrections, derive rotation curves for the lenses, their orientation and, thus, greatly constrain lens models.Comment: 69 pages, Review on quasar lensing. Part of a LNP Topical Volume on "Dark matter and gravitational lensing", eds. F. Courbin, D. Minniti. To be published by Springer-Verlag 2002. Paper with full resolution figures can be found at ftp://oden.oso.chalmers.se/pub/tommy/mmviews.ps.g

Designing a survey to monitor multi-scale impacts of agri-environment schemes on mobile taxa

Agri-environment schemes (AES) are key mechanisms to deliver conservation policy, and include management to provide resources for target taxa. Mobile species may move to areas where resources are increased, without this necessarily having an effect across the wider countryside or on populations over time. Most assessments of AES efficacy have been at small spatial scales, over short timescales, and shown varying results. We developed a survey design based on orthogonal gradients of AES management at local and landscape scales, which will enable the response of several taxa to be monitored. An evidence review of management effects on butterflies, birds and pollinating insects provided data to score AES options. Predicted gradients were calculated using AES uptake, weighted by the evidence scores. Predicted AES gradients for each taxon correlated strongly, and with the average gradient across taxa, supporting the co-location of surveys across different taxa. Nine 1 × 1 km survey squares were selected in each of four regional blocks with broadly homogenous background habitat characteristics. Squares in each block covered orthogonal contrasts across the range of AES gradients at local and landscape scales. This allows the effects of AES on species at each scale, and the interaction between scales, to be tested. AES options and broad habitats were mapped in field surveys, to verify predicted gradients which were based on AES option uptake data. The verified AES gradient had a strong positive relationship with the predicted gradient. AES gradients were broadly independent of background habitat within each block, likely allowing AES effects to be distinguished from potential effects of other habitat variables. Surveys of several mobile taxa are ongoing. This design will allow mobile taxa responses to AES to be tested in the surrounding countryside, as well as on land under AES management, and potentially in terms of population change over time. The design developed here provides a novel, pseudo-experimental approach for assessing the response of mobile species to gradients of management at two spatial scales. A similar design process could be applied in other regions that require a standardized approach to monitoring the impacts of management interventions on target taxa at landscape scales, if equivalent spatial data are available