The problem of clustering in laboratory studies of cometary dust

In trying to understand the nature of interstellar or interplanetary dust grains it is tempting to simply rely on direct lab measurements of grain properties such as extinction. However, until agreement is achieved between directly measured extinction and the same property calculated from measured optical constants of the solid, application to astronomical observations is questionable. There are two major problems which are discussed: the problem of what optical constants to use in the calculation, and the almost unavoidable problem of particle clustering in lab studies. Regarding small particle measurements, a problem afflicting almost all lab measurements is the clustering of particles. Having failed in efforts to isolate particles, the solution to the problem was attempted with a simple theory which seems to adequately describe the extinction by small, clustered particles in many cases. The theory is briefly explained

A NEW LOOK AT BEEF CATTLE PRICE REPORTING CLASSIFICATIONS

Demand and Price Analysis,

Community-based fire management at La Sepultura Biosphere Reserve, Chiapas, Mexico

2010 Fall.Includes bibliographical references.Within La Sepultura Biosphere Reserve in Chiapas, Mexico, human communities depend upon tropical pine-oak forests for survival. Management of this federally protected natural area is cooperative between government officials and local farmers and ranchers (producers). Producers conduct subsistence milpa agriculture and, by regulation of the reserve, have limited access to timber resources. I used a participatory, interdisciplinary approach to study community-based fire management in two communities within the reserve: Corazón del Valle and Valle de Corzo. Members of these two communities apply extensive traditional ecological knowledge in fire management. Focus groups and interviews revealed that producers integrate 40 environmental and social factors in their traditional burning practices. Frequent, low-intensity controlled burning with hand tools is customary to reduce fuels and to care for the forest. A shared concern of government managers and producers is reproduction of the dominant tree species, Pinus oocarpa. Producers had the opinion that trees grown from seed produce superior timber compared to trees grown from resprouting stems. Analysis of size class distributions of trees, seedlings and resprouts in 37 controlled burn plots confirmed that the density of seedlings is lower than would be expected under a typical reverse-J distribution. Seedling densities in two subjectively located wildfire sites were higher (mean = 3423 ± 2163 seedlings/ha). Despite very low-intensity fire behavior generated by producers in traditional controlled burning, seedling top-kill was high (82 percent). Because altering burning techniques would be unlikely to calm fire behavior any further, I tested two simple fuel removal treatments to try to reduce seedling top-kill. Removing fuels from a one meter radius around seedlings with a rake or machete reduced seedling top-kill to 52 percent. Removing fuels and covering seedlings with freshly cut green leaves reduced top-kill by 100 percent. Only by examining the social, ecological and physical aspects of traditional fire management was I able to arrive at practical methods for addressing the shared concern of post-fire pine seedling survival. Continued collaboration by reserve managers, community members and researchers can further refine management of tropical pine-oak ecosystems within the context of protected natural areas in Mesoamerica

The Family and Medical Leave Act of 1993 and the Current State of Employee Protection: What Type of Protection Can an Employee Expect upon Taking Work Leave for Family or Medical Problems

Commen

Iridium, shocked minerals, and trace elements across the Cretaceous/Tertiary boundary at Maud Rise, Wedell Sea, and Walvis Ridge, South Atlantic Ocean

Sediments spanning a 5 meter section across the Cretaceous-Tertiary boundary at ODP holes 689B and 690D, Maud Rise, Wedell Sea and hole 527, Walvis Ridge, are being analyzed for shock deformation, PGE's and other trace elements (including REE's). Mineral separates from each sample were studied with optical microscopy to determine the distribution and microstructural state of quartz and feldspar present in the sediments. Samples from Maud Rise were taken of the K/T transition and at about 50 cm intervals above and below it. These samples consist of carbonate-rich sediments, with the K/T transition marked by a change from white Maastrichtian oozes to a greenish ooze with higher concentrations of altered volcanic clay and vitric ash. The Walvis Ridge site is characterized by more clay-rich sediments with average carbonate content about 60 to 70 percent. Initial results from RNAA studies indicate that iridium is present in all the Maud Rise samples in concentrations equal to or greater than 0.01 ppb (whole-rock basis). Preliminary results from optical microscopy indicate the occurrence of shock mosaicism in quartz and feldspar in all of the samples studied. The pervasiveness of shock mosaicism and presence of planar features to 2 meters from the K/T boundary indicates that a single impact or volcanic explosion 66 ma may be ruled out as responsible for the K/T event. A similar conclusion may be drawn independently from the distribution of iridium and other trace elements. Regardless of the source of the shock waves and sediment contamination, multiple events are required over a ca.0.5 my timespan; currently we favor endogenous sources

Analysis of multi-sensor data, 12 September - 11 December 1968

Analysis of multi-sensor data obtained by Earth Resources Aircraft Progra

Measurements at low energies of the polarization-transfer coefficient Kyy' for the reaction 3H(p,n)3He at 0 degrees

Measurements of the transverse polarization coefficient Kyy' for the reaction 3H(p,n)3He are reported for outgoing neutron energies of 1.94, 5.21, and 5.81 MeV. This reaction is important both as a source of polarized neutrons for nuclear physics experiments, and as a test of theoretical descriptions of the nuclear four-body system. Comparison is made to previous measurements, confirming the 3H(p,n)3He reaction can be used as a polarized neutron source with the polarization known to an accuracy of approximately 5%. Comparison to R-matrix theory suggests that the sign of the 3F3 phase-shift parameter is incorrect. Changing the sign of this parameter dramatically improves the agreement between theory and experiment.Comment: 12 pages, RevTeX, 5 eps figures, submitted to Phys. Rev.

An implementation of Deflate in Coq

The widely-used compression format "Deflate" is defined in RFC 1951 and is based on prefix-free codings and backreferences. There are unclear points about the way these codings are specified, and several sources for confusion in the standard. We tried to fix this problem by giving a rigorous mathematical specification, which we formalized in Coq. We produced a verified implementation in Coq which achieves competitive performance on inputs of several megabytes. In this paper we present the several parts of our implementation: a fully verified implementation of canonical prefix-free codings, which can be used in other compression formats as well, and an elegant formalism for specifying sophisticated formats, which we used to implement both a compression and decompression algorithm in Coq which we formally prove inverse to each other -- the first time this has been achieved to our knowledge. The compatibility to other Deflate implementations can be shown empirically. We furthermore discuss some of the difficulties, specifically regarding memory and runtime requirements, and our approaches to overcome them

Examining the Impact of Service Times on Overall Guest Satisfaction Perception in the Casual Dining Environment

A mystery shopper study was used to examine the influence of service times on customer satisfaction. The impact of management emphasis on service quality was also examined. In the restaurants studied, service time influenced customer satisfaction. Management attention to service time improved performance in direct relationship to the level of emphasis