Born reciprocity and the 1/r potential

Many structures in nature are invariant under the transformation (p,r)->(br,-p/b), where b is some scale factor. Born's reciprocity hypothesis affirms that this invariance extends to the entire Hamiltonian and equations of motion. We investigate this idea for atomic physics and galactic motion, where one is basically dealing with a 1/r potential and the observations are very accurate, so as to determine the scale $b = m\Omega$. We find that an $\Omega \sim 1.5\times 10^{-15}$ Hz has essentially no effect on atomic physics but might possibly offer an explanation for galactic rotation, without invoking dark matter.Comment: 14 pages, with 4 figures, Latex, requires epsf.tex and iop style file

Probing the shape of atoms in real space

The structure of single atoms in real space is investigated by scanning tunneling microscopy. Very high resolution is possible by a dramatic reduction of the tip-sample distance. The instabilities which are normally encountered when using small tip-sample distances are avoided by oscillating the tip of the scanning tunneling microscope vertically with respect to the sample. The surface atoms of Si(111)-(7 x 7) with their well-known electronic configuration are used to image individual samarium, cobalt, iron and silicon atoms. The resulting images resemble the charge density corresponding to 4f, 3d and 3p atomic orbitals.Comment: Submitted to Phys. Rev. B, 17 pages, 7 figure

Niche models for British plants and lichens obtained using an ensemble approach

Site-occupancy models that predict habitat suitability for plant species in relation to measurable environmental factors can be useful for conservation planning. Such models can be derived from large-scale presence–absence datasets on the basis of environmental observations or, where only floristic data are available, using plant trait values averaged across a plot. However, the estimated modelled relationship between species presence and environmental variables depends on the type of statistical model adopted and hence can introduce additional uncertainty. Authors used an ensemble-modelling approach to constrain and quantify the uncertainty because of the choice of statistical model, applying generalised linear models (GLM), generalised additive models (GAM), and multivariate adaptive regression splines (MARS). Niche models were derived for over 1000 species of vascular plants, bryophytes and lichens, representing a large proportion of the British flora and many species occurring in continental Europe. Each model predicts habitat suitability for a species in response to climate variables and trait-based scores (evaluated excluding the species being modelled) for soil pH, fertility, wetness and canopy height. An R package containing the fitted models for each species is presented which allows the user to predict the habitat suitability of a given set of conditions for a particular species. Further functions within the package are included so that these habitat suitability scores can be plotted in relation to individual explanatory variables. A simple case study shows how the R package (MultiMOVE) can be used quickly and efficiently to answer questions of scientific interest, specifically whether climate change will counteract any benefits of sheep-grazing for a particular plant community. The package itself is freely available via http://doi.org/10.5285/94ae1a5a-2a28-4315-8d4b-35ae964fc3b9

Modelling Landscape-scale Species Response to Agri-Environment Schemes

Agri-environment schemes (AES) are the most significant environmental policy delivery mechanism in England, and include the conservation of biodiversity as a key objective. Provisional results from the ongoing Landscape-scale species monitoring of AES (LandSpAES) baseline field survey have shown some positive responses of mobile taxa to AES gradients at local (1km2) or landscape (3 × 3km) scales. However, it is not known whether these provisional results might be more broadly applicable outside the regions surveyed in the LandSpAES project, i.e. in other regions, or nationally. Here, we present the findings of an analytical project to explore the use of national Citizen Science (CitSci) scheme data, to investigate whether similar relationships with AES gradients would be found at a national scale in CitSci data to those shown with LandSpAES data, and whether integrated modelling was possible with combined CitSci and LandSpAES datasets. The design of LandSpAES has high power to detect AES effects, including the independent testing of the local and landscape AES gradients, but is restricted to six regions. The national CitSci are more representative of England as a whole, but have not been designed to detect AES effects. The aim of this project was to determine whether the provisional taxon responses to the AES gradients found in the LandSpAES project could be detected at a national scale using CitSci scheme data. To achieve this aim, three key questions were addressed through the analytical work: 1) Can addition of covariates account for environmental variation between survey squares in each dataset, to improve the comparability of AES gradient effects between LandSpAES and CitSci schemes? 2) Do the CitSci scheme datasets show similar relationships between taxa responses and the AES gradients, to those found with the LandSpAES data? 3) Can integrated approaches to combining datasets be used to jointly model CitSci and LandSpAES data, and does integrated modelling reduce uncertainty in quantifying the effects of AES gradients on taxa responses at a national scale across England

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

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

Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe

Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV

A search for a Higgs boson decaying into two photons is described. The analysis is performed using a dataset recorded by the CMS experiment at the LHC from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross section of the standard model Higgs boson decaying to two photons. The expected exclusion limit at 95% confidence level is between 1.4 and 2.4 times the standard model cross section in the mass range between 110 and 150 GeV. The analysis of the data excludes, at 95% confidence level, the standard model Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The largest excess of events above the expected standard model background is observed for a Higgs boson mass hypothesis of 124 GeV with a local significance of 3.1 sigma. The global significance of observing an excess with a local significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is estimated to be 1.8 sigma. More data are required to ascertain the origin of this excess.Comment: Submitted to Physics Letters

Landscape-scale species monitoring of agri-environment schemes (LandSpAES project). Final project report, 2022

In this project, we applied a novel, pseudo-experimental design in order to collect a baseline survey dataset of the responses of mobile taxa to local and landscape AES gradients over four years, from 54 survey squares across six regions (NCAs) in England. This is the first project to monitor the responses of multiple mobile taxa to generalised AES gradients across large spatial extents, which were applied to arable, grassland and upland agricultural systems, in order specifically to address impacts beyond AES option or agreement boundaries. This baseline dataset supported a spatial assessment of relationships between the AES gradients and taxon abundance (or activity), species richness and diversity. Strong evidence for relationships with local and / or landscape AES gradients were found for one or more response variable for butterflies, moths and bats. Little or no evidence of AES gradient relationships were found for either bees or hoverflies and weak evidence for associations with bird metrics. A future resurvey would allow analyses of the longer-term changes in target taxa in response to AES management, against this baseline. The identification of various spatial relationships is encouraging in terms of the likely power to detect AES effects on biodiversity change in the future

Search for new physics in events with opposite-sign leptons, jets, and missing transverse energy in pp collisions at sqrt(s) = 7 TeV

A search is presented for physics beyond the standard model (BSM) in final states with a pair of opposite-sign isolated leptons accompanied by jets and missing transverse energy. The search uses LHC data recorded at a center-of-mass energy sqrt(s) = 7 TeV with the CMS detector, corresponding to an integrated luminosity of approximately 5 inverse femtobarns. Two complementary search strategies are employed. The first probes models with a specific dilepton production mechanism that leads to a characteristic kinematic edge in the dilepton mass distribution. The second strategy probes models of dilepton production with heavy, colored objects that decay to final states including invisible particles, leading to very large hadronic activity and missing transverse energy. No evidence for an event yield in excess of the standard model expectations is found. Upper limits on the BSM contributions to the signal regions are deduced from the results, which are used to exclude a region of the parameter space of the constrained minimal supersymmetric extension of the standard model. Additional information related to detector efficiencies and response is provided to allow testing specific models of BSM physics not considered in this paper.Comment: Replaced with published version. Added journal reference and DO