Development of the technology for the fabrication of reliable laminar from control panels

Materials were assessed and fabrication techniques were developed for use in the manufacture of wing surface materials compatible with the application of both aluminum alloys and nonmetallic composites. The concepts investigated included perforations and slots in the metallic test panels and microporosity and perforations in the composite test panels. Perforations were produced in the metallic test panels by the electron beam process and slots were developed by controlled gaps between the metal sheets. Microporosity was produced in the composite test panels by the resin bleed process, and perforations were produced by the fugitive fiber technique. Each of these concepts was fabricated into test panels, and air flow tests were conducted on the panels

Are tiled display walls needed for astronomy?

Clustering commodity displays into a Tiled Display Wall (TDW) provides a cost-effective way to create an extremely high resolution display, capable of approaching the image sizes now gen- erated by modern astronomical instruments. Astronomers face the challenge of inspecting single large images, many similar images simultaneously, and heterogeneous but related content. Many research institutions have constructed TDWs on the basis that they will improve the scientific outcomes of astronomical imagery. We test this concept by presenting sample images to astronomers and non- astronomers using a standard desktop display (SDD) and a TDW. These samples include standard English words, wide field galaxy surveys and nebulae mosaics from the Hubble telescope. These experiments show that TDWs provide a better environment for searching for small targets in large images than SDDs. It also shows that astronomers tend to be better at searching images for targets than non-astronomers, both groups are generally better when employing physical navigation as opposed to virtual navigation, and that the combination of two non-astronomers using a TDW rivals the experience of a single astronomer. However, there is also a large distribution in aptitude amongst the participants and the nature of the content also plays a significant role is success.Comment: 19 pages, 15 figures, accepted for publication in PASA (Publications of the Astronomical Society of Australia

Structural Separation versus Vertical Integration: Lessons for Telecommunications from Electricity Reforms

Structural separation between network and retail functions is increasingly being mandated in the telecommunications sector to countervail the market power of incumbent operators. Experience of separation in the electricity sector offers insights for telecommunications. Despite apparent competitive benefits the costs of contracting increase markedly when short-term focused electricity retail operations are separated from longer-term generation infrastructure investments (which require large up-front fixed and sunk cost components). The combination of mismatches in investment horizons entry barriers and risk preference and information asymmetries between generators and retailers leads to thin contract markets increased hold-up risk perverse wholesale risk management incentives and bankruptcies. Direct parallels in the telecommunications sector (e.g. separated retail and infrastructure functions) indicate exposure to similar complications intensifying many of the contractual risks arising from regulated access arrangements. In both sectors competition between vertically integrated providers appears more likely to efficiently and sustainably induce both investment and competition than separation

Searches for Long Lived Neutral Particles

An intriguing possibility for TeV scale physics is the existence of neutral long lived particles (LOLIPs) that subsequently decay into SM states. Such particles are many cases indistinguishable from missing transverse energy (MET) at colliders. We propose new methods to search for these particles using neutrino telescopes. We study their detection prospects, assuming production either at the LHC or through dark matter (DM) annihilations in the Sun and the Earth. We find that the sensitivity for LOLIPs produced at the LHC is limited by luminosity and detection energy thresholds. On the other hand, in the case of DM annihilation into LOLIPs, the sensitivity of neutrino telescopes is promising and may extend beyond the reach of upcoming direct detection experiments. In the context of low scale hidden sectors weakly coupled to the SM, such indirect searches allow to probe couplings as small as 10^-15.Comment: 22 pages, 6 figure

Etched distributed Bragg reflectors as three-dimensional photonic crystals: photonic bands and density of states

The photonic band dispersion and density of states (DOS) are calculated for the three-dimensional (3D) hexagonal structure corresponding to a distributed Bragg reflector patterned with a 2D triangular lattice of circular holes. Results for the Si/SiO$_2$ and GaAs/AlGaAs systems determine the optimal parameters for which a gap in the 2D plane occurs and overlaps the 1D gap of the multilayer. The DOS is considerably reduced in correspondence with the overlap of 2D and 1D gaps. Also, the local density of states (i.e., the DOS weighted with the squared electric field at a given point) has strong variations depending on the position. Both results imply substantial changes of spontaneous emission rates and patterns for a local emitter embedded in the structure and make this system attractive for the fabrication of a 3D photonic crystal with controlled radiative properties.Comment: 8 pages, 5 figures; to appear in Phys. Rev.

Natural Supersymmetry at the LHC

If the minimal supersymmetric standard model is the solution to the hierarchy problem, the scalar top quark (stop) and the Higgsino should weigh around the electroweak scale such as 200 GeV. A low messenger scale, which results in a light gravitino, is also suggested to suppress the quantum corrections to the Higgs mass parameters. Therefore the minimal model for natural supersymmetry is a system with stop/Higgsino/gravitino whereas other superparticles are heavy. We study the LHC signatures of the minimal system and discuss the discovery potential and methods for the mass measurements.Comment: 19 pages, 6 figures, 1 tabl

Improving trial recruitment through improved communication about patient and public involvement : an embedded cluster randomised recruitment trial

Background: Evidence is emerging that patient and public involvement in research (PPIR) may improve recruitment into randomised controlled trials, but the best methods to achieve improvement are unclear. Although many trials use PPIR to improve design and conduct, many do not communicate their use of PPIR clearly to potential participants. Directly communicating PPIR might encourage participation through increased patient confidence and trust in a trial. We aimed to develop and evaluate the impact on recruitment an intervention communicating PPIR in a trial to potential participants. Methods: This study was embedded in EQUIP, a cluster randomised controlled trial which allocated mental health teams in England to either a training intervention group to improve service user and carer involvement in care planning, or to a control group (no training). We conducted a cluster randomised trial of a recruitment intervention communicating PPIR, embedded within the EQUIP trial. The principles underlying the intervention were informed by a systematic review and a workshop that included mental health service users and trialists. Working with EQUIP PPIR partners (service users and carers) we developed the intervention using a leaflet to advertise the nature and function of the PPIR. Professional graphic design optimised readability and impact. Patients identified as potentially eligible for EQUIP were randomised to receive the leaflet or not, alongside the standard trial information. The primary outcome was the proportion of participants enrolled in EQUIP. The secondary outcome was the proportion expressing interest in taking part. Results: 34 clusters (mental health teams) were recruited, and 8182 potential participants were randomised. Preliminary analyses show that for the primary outcome, 4% of patients receiving the PPIR leaflet were enrolled vs. 5.3% in the control group. For the secondary outcome 7.3% of potential participants receiving the PPIR leaflet responded positively to the invitation to participate, vs. 7.9% in the control group. Future analyses will be by intention-to-treat and use logistic regression to estimate between-group odds ratios (ORs) and corresponding 95% confidence intervals. A planned secondary analysis will explore whether the impact of the intervention is moderated by age and gender. Conclusion: In preliminary analysis of this large trial, communicating PPIR demonstrated no benefits for improving the numbers of potential participants expressing interest in the trial, and reduced trial enrolment. Our findings contrast with the literature suggesting PPIR benefits recruitment. We will discuss the potential reasons for this finding, along with implications for future recruitment practice and research

Structure and Stability of Si(114)-(2x1)

We describe a recently discovered stable planar surface of silicon, Si(114). This high-index surface, oriented 19.5 degrees away from (001) toward (111), undergoes a 2x1 reconstruction. We propose a complete model for the reconstructed surface based on scanning tunneling microscopy images and first-principles total-energy calculations. The structure and stability of Si(114)-(2x1) arises from a balance between surface dangling bond reduction and surface stress relief, and provides a key to understanding the morphology of a family of surfaces oriented between (001) and (114).Comment: REVTeX, 4 pages + 3 figures. A preprint with high-resolution figures is available at http://cst-www.nrl.navy.mil/papers/si114.ps . To be published in Phys. Rev. Let

MSSM in view of PAMELA and Fermi-LAT

We take the MSSM as a complete theory of low energy phenomena, including neutrino masses and mixings. This immediately implies that the gravitino is the only possible dark matter candidate. We study the implications of the astrophysical experiments such as PAMELA and Fermi-LAT, on this scenario. The theory can account for both the realistic neutrino masses and mixings, and the PAMELA data as long as the slepton masses lie in the $500-10^6$TeV range. The squarks can be either light or heavy, depending on their contribution to radiative neutrino masses. On the other hand, the Fermi-LAT data imply heavy superpartners, all out of LHC reach, simply on the grounds of the energy scale involved, for the gravitino must weigh more than 2 TeV. The perturbativity of the theory also implies an upper bound on its mass, approximately $6-7$TeV.Comment: Published version, figures update

Momentum asymmetries as CP violating observables

Three body decays can exhibit CP violation that arises from interfering diagrams with different orderings of the final state particles. We construct several momentum asymmetry observables that are accessible in a hadron collider environment where some of the final state particles are not reconstructed and not all the kinematic information can be extracted. We discuss the complications that arise from the different possible production mechanisms of the decaying particle. Examples involving heavy neutralino decays in supersymmetric theories and heavy Majorana neutrino decays in Type-I seesaw models are examined.Comment: 20 pages, 9 figures. Clarifying comments and one reference added, matches published versio