Space weathering: Laboratory analyses and in-situ instrumentation

Simulations of space weathering using laser irradiation are exploited to study the formation of sub-microscopic iron. A variety of magnetic techniques are evaluated to characterise this iron and are considered for in-situ instrumentation

Models for Light-Cone Meson Distribution Amplitudes

Leading-twist distribution amplitudes (DAs) of light mesons like pi,rho etc. describe the leading nonperturbative hadronic contributions to exclusive QCD reactions at large energy transfer, for instance electromagnetic form factors. They also enter B decay amplitudes described in QCD factorisation, in particular nonleptonic two-body decays. Being nonperturbative quantities, DAs cannot be calculated from first principles, but have to be described by models. Most models for DAs rely on a fixed order conformal expansion, which is strictly valid for large factorisation scales, but not always sufficient in phenomenological applications. We derive models for DAs that are valid to all orders in the conformal expansion and characterised by a small number of parameters which are related to experimental observables.Comment: 19 pages, 10 figure

The Meat Standards Australia Index indicates beef carcass quality

A simple index that reflects the potential eating quality of beef carcasses is very important for producer feedback. The Meat Standards Australia (MSA) Index reflects variation in carcass quality due to factors that are influenced by producers (hot carcass weight, rib fat depth, hump height, marbling and ossification scores along with milk fed veal category, direct or saleyard consignment, hormonal growth promotant status and sex). In addition, processor impacts on meat quality are standardised so that the MSA Index could be compared across time, breed and geographical regions. Hence, the MSA Index was calculated using achilles hung carcasses, aged for 5 days postmortem. Muscle pH can be impacted by production, transport, lairage or processing factors, hence the MSA Index assumes a constant pH of 5.6 and loin temperature of 7 o C for all carcasses. To quantify the cut weight distribution of the 39 MSA cuts in the carcass, 40 Angus steers were sourced from the low (n=13), high (n=15) and myostatin (n=12) muscling selection lines. The left side of each carcass was processed down to the 39 trimmed MSA cuts. There was no difference in MSA cut distribution between the low and high muscling lines (P>0.05), although there were differences with nine cuts from the myostatin line (P<0.05). There was no difference in the MSA Index calculated using actual muscle percentages and using the average from the low and high muscling lines (R 2 =0.99). Different cooking methods impacted via a constant offset between eating quality and carcass input traits (R 2 =1). The MSA Index calculated for the four most commercially important cuts was highly related to the index calculated using all 39 MSA cuts (R 2 =0.98), whilst the accuracy was lower for an index calculated using the striploin (R 2 =0.82). Therefore, the MSA Index was calculated as the sum of the 39 eating quality scores predicted at 5 days ageing, based on their most common cooking method, weighted by the proportions of the individual cut relative to total weight of all cuts. The MSA Index provides producers with a tool to assess the impact of management and genetic changes on the predicted eating quality of the carcass. The MSA Index could also be utilised for benchmarking and to track eating quality trends at farm, supply chain, regional, state or national levels

The Quark Propagator from the Dyson-Schwinger Equations: I. the Chiral Solution

Within the framework of the Dyson-Schwinger equations in the axial gauge, we study the effect that non-perturbative glue has on the quark propagator. We show that Ward-Takahashi identities, combined with the requirement of matching perturbative QCD at high momentum transfer, guarantee the multiplicative renormalisability of the answer. Technically, the matching with perturbation theory is accomplished by the introduction of a transverse part to the quark-gluon vertex. We show that this transverse vertex is crucial for chiral symmetry breaking, and that massless solutions exist below a critical value of the strong coupling constant. Using the gluon propagator that we previously calculated, we obtain small corrections to the quark propagator, which keeps a pole at the origin in the chiral phase.Comment: 21 pages, 6 figures; McGill/94-24, SHEP 93/94-26 We generalise our results by showing that they are not sensitive to the specific choice that we make for the transverse vertex. We illustrate that fact in two new figure

Rare K and B Decays in the Littlest Higgs Model without T-Parity

We analyze rare K and B decays in the Littlest Higgs (LH) model without T-parity. We find that the final result for the Z^0-penguin contribution contains a divergence that is generated by the one-loop radiative corrections to the currents corresponding to the dynamically broken generators. Including an estimate of these logarithmically enhanced terms, we calculate the branching ratios for the decays K^+ -> pi^+ nu bar nu, K_L -> pi^0 nu bar nu, B_{s,d} -> mu^+ mu^- and B -> X_{s,d} nu bar nu. We find that for the high energy scale f=O(2-3) TeV, as required by the electroweak precision studies, the enhancement of all branching ratios amounts to at most 15% over the SM values. On the technical side we identify a number of errors in the existing Feynman rules in the LH model without T-parity that could have some impact on other analyses present in the literature. Calculating penguin and box diagrams in the unitary gauge, we find divergences in both contributions that are cancelled in the sum except for the divergence mentioned above.Comment: 39 pages, 8 figures, typos corrected, comment on (2.17) and (2.18) added, references added, results unchange

Predicting death and readmission after intensive care discharge

Background: Despite initial recovery from critical illness, many patients deteriorate after discharge from the intensive care unit (ICU). We examined prospectively collected data in an attempt to identify patients at risk of readmission or death after intensive care discharge. Methods: This was a secondary analysis of clinical audit data from patients discharged alive from a mixed medical and surgical (non-cardiac) ICU. Results: Four hundred and seventy-five patients (11.2%) died in hospital after discharge from the ICU. Increasing age, time in hospital before intensive care admission, Acute Physiology and Chronic Health Evaluation II (APACHE II) score, and discharge Therapeutic Intervention Scoring System (TISS) score were independent risk factors for death after intensive care discharge. Three hundred and eighty-five patients (8.8%) were readmitted to intensive care during the same hospital admission. Increasing age, time in hospital before intensive care, APACHE II score, and discharge to a high dependency unit were independent risk factors for readmission. One hundred and forty-three patients (3.3%) were readmitted within 48 h of intensive care discharge. APACHE II scores and discharge to a high dependency or other ICU were independent risk factors for early readmission. The overall discriminant ability of our models was moderate with only marginal benefit over the APACHE II scores alone. Conclusions: We identified risk factors associated with death and readmission to intensive care. It was not possible to produce a definitive model based on these risk factors for predicting death or readmission in an individual patient.Not peer reviewedAuthor versio