Measuring crack initiation and the plastic deformation behaviour of titanium aluminides under compressive and tensile uniaxial loading

At temperatures of the order of 700 °C, suitable for the operation of low and intermediate pressure turbines and compressors in gas turbine engines, gamma titanium aluminides possess a higher specific strength than nickel superalloys. However, γ-TiAl suffers from a sufficiently reduced plasticity for a threshold approach to fatigue lifing to be necessary. Improving the fatigue behaviour of γ-TiAl requires an understanding of crack nucleation and how this is related to the detailed microstructure. Towards this, the monotonic compressive and tensile deformation behaviour of this two-phase lamellar composite alloy, Ti-45Al-2Nb-2Mn(at.%)-0.8vol%TiB2, currently undergoing engine tests by Rolls Royce, has therefore been measured at both room temperature and at 700°C. Both colony and lamellar-scale deformation features of the material have been investigated. Microstructural conditions with varying lamellar thicknesses were characterised by scanning electron microscopy and transmission Kikuchi diffraction. The near-surface plastic strain field and the build-up of local strains have been measured, using digital image correlation, with a remodelled gold speckle pattern, and compared with misorientation mapping using electron backscatter diffraction, both before and after testing. Temperature was found to have a significant impact on the active deformation mechanisms and their directions relative to the lamellae; this affects the ability of the material to provide compatible deformation. At high temperature, the shear generated upon twinning was found to be closely associated to debonding at colony boundaries. This is related to the possible accumulation of damage in cyclic loading

Scattering amplitudes with massive fermions using BCFW recursion

We study the QCD scattering amplitudes for \bar{q}q \to gg and \bar{q}q \to ggg where q is a massive fermion. Using a particular choice of massive fermion spinor we are able to derive very compact expressions for the partial spin amplitudes for the 2 \to 2 process. We then investigate the corresponding 2 \to 3 amplitudes using the BCFW recursion technique. For the helicity conserving partial amplitudes we again derive very compact expressions, but were unable to treat the helicity-flip amplitudes recursively, except for the case where all the gluon helicities are the same. We therefore evaluate the remaining partial amplitudes using standard Feynman diagram techniques.Comment: 21 page

A Constrained Standard Model from a Compact Extra Dimension

A SU(3) \times SU(2) \times U(1) supersymmetric theory is constructed with a TeV sized extra dimension compactified on the orbifold S^1/(Z_2 \times Z_2'). The compactification breaks supersymmetry leaving a set of zero modes which correspond precisely to the states of the 1 Higgs doublet standard model. Supersymmetric Yukawa interactions are localized at orbifold fixed points. The top quark hypermultiplet radiatively triggers electroweak symmetry breaking, yielding a Higgs potential which is finite and exponentially insensitive to physics above the compactification scale. This potential depends on only a single free parameter, the compactification scale, yielding a Higgs mass prediction of 127 \pm 8 GeV. The masses of the all superpartners, and the Kaluza-Klein excitations are also predicted. The lightest supersymmetric particle is a top squark of mass 197 \pm 20 GeV. The top Kaluza-Klein tower leads to the \rho parameter having quadratic sensitivity to unknown physics in the ultraviolet.Comment: 31 pages, Latex, 2 eps figures, minor correction

A developmental analysis of communication between mothers and infants with Down's syndrome

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68850/2/10.1177_027112148300300110.pd

An assessment of the reliability of three methods used in evaluating the status of multiple sclerosis patients

The reliability of three different evaluation methods used in a cooperative clinical trial of the efficacy of ACTH in multiple sclerosis patients was evaluated in a uniformity study that used an efficient statistical design requiring only 10 patients and 5 examiners. The methods were the standard neurologic examination, a scoring system for functional grades and disability status, and a 7-day symptom score. Each patient was examined only 3 times at the beginning of the study and 3 more times 6 days later. No significant differences among the 5 examiners were observed on 82 of the 87 items used to measure neurologic function. With the exception of 1 variable, there were no significant differences among the average values of the sequence of the 3 examinations, nor among the average increments of change in the numerical scores between the first and second trials.In an additional examination in which all 5 examiners simultaneously evaluated 3 patients 1 at a time, it was found that the 5 examiners observed uniformly in all of the neurologic tests.The results of this study indicate that, by and large, the three evaluation methods appear to be reliable in the evaluation of neurologic status when used in a cooperative clinical trial where several investigators contribute data. Furthermore, investigations of reliability in cooperative studies can be performed with the use of efficient statistical designs such as the incomplete Latin-square design.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32998/1/0000382.pd

SUSY GUT Model Building

I discuss an evolution of SUSY GUT model building, starting with the construction of 4d GUTs, to orbifold GUTs and finally to orbifold GUTs within the heterotic string. This evolution is an attempt to obtain realistic string models, perhaps relevant for the LHC. This review is in memory of the sudden loss of Julius Wess, a leader in the field, who will be sorely missed.Comment: 24 pages, 14 figures, lectures given at PiTP 2008, Institute for Advanced Study, Princeton, to be published in the European Physical Journal

Outlier Resistant PCA Ensembles

Statistical re-sampling techniques have been used extensively and successfully in the machine learning approaches for generation of classifier and predictor ensembles. It has been frequently shown that combining so called unstable predictors has a stabilizing effect on and improves the performance of the prediction system generated in this way. In this paper we use the re-sampling techniques in the context of Principal Component Analysis (PCA). We show that the proposed PCA ensembles exhibit a much more robust behaviour in the presence of outliers which can seriously affect the performance of an individual PCA algorithm. The performance and characteristics of the proposed approaches are illustrated on a number of experimental studies where an individual PCA is compared to the introduced PCA ensemble

Digital Drugs: an anatomy of new medicines

Medicines are digitalized as aspects of their regulation and use are embodied in or draw from interlinked computerized systems and databases. This paper considers how this development changes the delivery of health care, the pharma industry, and regulatory and professional structures, as it reconfigures the material character of drugs themselves. It draws on the concept of assemblage in presenting a theory-based analysis that explores digital drugs’ ontological status including how they embody benefit and value. The paper addresses three interconnected domains – that of use of drugs (practice), of research (epistemology) and of regulation (structures)

Randomized Clinical-Trial of Manipulative Therapy and Physiotherapy for Persistent Back and Neck Complaints - Results of One Year Follow-Up

Objective - To compare the effectiveness of manipulative therapy, physiotherapy, treatment by the general practitioner, and placebo therapy in patients with persistent non-specific back and neck complaints. Design - Randomised clinical trial. Setting-Primary health care in the Netherlands. Patients-256 patients with non-specific back and neck complaints of at least six weeks' duration who had not received physiotherapy or manipulative therapy in the past two years. Interventions - At the discretion of the manipulative therapists, physiotherapists, and general practitioners. Physiotherapy consisted of exercises, massage, and physical therapy (heat, electrotherapy, ultrasound, shortwave diathermy). Manipulative therapy consisted of manipulation and mobilisation of the spine. Treatment by general practitioners consisted of drugs (for example, analgesics), advice about posture, home exercises, and (bed)rest. Placebo treatment consisted of detuned shortwave diathermy (10 minutes) and detuned ultrasound (10 minutes). Main outcome measures - Changes in severity of the main complaint and limitation of physical functioning measured on 10 point scales by a blinded research assistant and global perceived effect measured on a 6 point scale by the patients. Results - Many patients in the general practitioner and placebo groups received other treatment during follow up. Improvement in the main complaint was larger with manipulative therapy (4·5) than with physiotherapy (3·8) after 12 months' follow up (difference 0·9; 95% confidence interval 0·1 to 1·7). Manipulative therapy also gave larger improvements in physical functioning (difference 0·6; -0·1 to 1·3). The global perceived effect after six and 12 months' follow up was similar for both treatments. Conclusions - Manipulative therapy and physiotherapy are better than general practitioner and placebo treatment. Furthermore, manipulative therapy is slightly better than physiotherapy after 12 months

Sub-femto-g free fall for space-based gravitational wave observatories: LISA pathfinder results

We report the first results of the LISA Pathfinder in-flight experiment. The results demonstrate that two free-falling reference test masses, such as those needed for a space-based gravitational wave observatory like LISA, can be put in free fall with a relative acceleration noise with a square root of the power spectral density of 5.2 ± 0.1 fm s−2/√Hz or (0.54 ± 0.01) × 10−15 g/√Hz, with g the standard gravity, for frequencies between 0.7 and 20 mHz. This value is lower than the LISA Pathfinder requirement by more than a factor 5 and within a factor 1.25 of the requirement for the LISA mission, and is compatible with Brownian noise from viscous damping due to the residual gas surrounding the test masses. Above 60 mHz the acceleration noise is dominated by interferometer displacement readout noise at a level of (34.8 ± 0.3) fm/√Hz, about 2 orders of magnitude better than requirements. At f ≤ 0.5 mHz we observe a low-frequency tail that stays below 12 fm s−2/√Hz down to 0.1 mHz. This performance would allow for a space-based gravitational wave observatory with a sensitivity close to what was originally foreseen for LISA