A Lagrangian relaxation approach to the edge-weighted clique problem

The $b$-clique polytope $CP^n_b$ is the convex hull of the node and edge incidence vectors of all subcliques of size at most $b$ of a complete graph on $n$ nodes. Including the Boolean quadric polytope $QP^n$ as a special case and being closely related to the quadratic knapsack polytope, it has received considerable attention in the literature. In particular, the max-cut problem is equivalent with optimizing a linear function over $QP^n_n$. The problem of optimizing linear functions over $CP^n_b$ has so far been approached via heuristic combinatorial algorithms and cutting-plane methods. We study the structure of $CP^n_b$ in further detail and present a new computational approach to the linear optimization problem based on Lucena's suggestion of integrating cutting planes into a Lagrangian relaxation of an integer programming problem. In particular, we show that the separation problem for tree inequalities becomes polynomial in our Lagrangian framework. Finally, computational results are presented. \u

Trade liberalization in Uruguay: Domestic and foreign firms

The reallocation of resources is one of the main impacts of trade liberalization processes. In the case of manufacturing industries resources will be reallocated from import--competing sectors to export--oriented sectors. This paper studies the effects that a more open economic environment has had on the entry conditions for foreign and domestic firms in Uruguayan manufacturing industries. We find significant differences in the behavior of foreign and domestic firms, both when they are incumbents or when they act as potential entrants. In general, foreign firms seem to be more successful in applying entry deterring strategies, due to advantages in foreign markets, deeper financial resources or better technological capabilities. They also appear to be more responsive to entry conditions when they face the prospects of entering a given industry.Production and market structure,industry studies

400 pc Imaging of a Massive Quasar Host Galaxy at a Redshift of 6.6

We report high spatial resolution (~0.076", 410pc) Atacama Large Millimeter/submillimeter Array imaging of the dust continuum and the ionized carbon line [CII] in a luminous quasar host galaxy at z=6.6, 800 million years after the big bang. Based on previous studies, this galaxy hosts a ~1x10^9 M_sun black hole and has a star-formation rate of ~1500 M_sun/yr. The unprecedented high resolution of the observations reveals a complex morphology of gas within 3kpc of the accreting central black hole. The gas has a high velocity dispersion with little ordered motion along the line of sight, as would be expected from gas accretion that has yet to settle in a disk. In addition, we find the presence of [CII] cavities in the gas distribution (with diameters of ~0.5kpc), offset from the central black hole. This unique distribution and kinematics cannot be explained by a simple model. Plausible scenarios are that the gas is located in a truncated or warped disk, or the holes are created by interactions with nearby galaxies or due to energy injection into the gas. In the latter case, the energy required to form the cavities must originate from the central active galactic nucleus, as the required energy far exceeds the energy output expected from supernovae. This energy input into the gas, however, does not inhibit the high rate of star-formation. Both star-formation and black hole activity could have been triggered by interactions with satellite galaxies; our data reveal three additional companions detected in [CII] emission around the quasar.Comment: Published in ApJ Letter

The wear behaviour of UHMWPE and ion implanted UHMWPE against differing counterfaces

Includes bibliographical references.A study has been made of the tribological behaviour of ultra high molecular weight polyethylene (UHMWPE) and ion implanted UHMWPE during water lubricated reciprocating sliding against differing stainless steel and Yttria Partially Stabilised Zirconia (YPSZ) counterfaces. A new laboratory test apparatus was designed, built and commissioned to facilitate this research. The new apparatus is capable of simulating the reciprocating wear of a sliding couple under diverse conditions of pressure, sliding speed and lubricant environment, as well as allowing the measurement of frictional forces 'encountered between the two surfaces in sliding contact. Variation in stainless steel counterface surface roughness resulted in three different types of wear behaviour

Correlation between charring rate and oxygen permeability for 12 different wood species

The charring rates of 12 different wood species originating from Europe and the tropics with densities ranging from 350 to 750kg/m3 were investigated to obtain clues on their fire resistance behavior. This was done by measuring the thickness of the charred layer after a 30-min exposure to the standard fire ISO 834-1. No correlation was observed between charring rate and density. In search of another physical property that could be used as an indicator of fire resistance, the oxygen permeabilities of the selected wood types were measured. A strong correlation between oxygen permeability perpendicular to the wood fiber direction and charring rate was found, which is quite straightforward given that oxygen is the necessary component to enable smoldering and ignition, both affecting the charring rate. It seems that oxygen permeability is potentially more suitable as a parameter to evaluate the fire resistance of char-sensitive wooden constructions, rather than density. No general preference of the tree ring orientation from 0° (tangential) to 45° and 90° (radial) was found for these measurement

Chronic lymphocytic leukaemia: clinical-aetiological findings in 66 patients and their families

<p>Abstract</p> <p>Background</p> <p>Little is known about the aetiology of chronic lymphocytic leukaemia (CLL). The family medical history is a "genomic tool" capturing interactions of genetic susceptibility, shared environment and common behaviours.</p> <p>Methods</p> <p>A cohort of 66 consecutives patients with CLL (probands) was studied in a medical oncology practice (W.W.) from 1981 until 2005. A German version of the NCI medical history questionnaire for cancer aetiology was used. Familial clustering analysis was done by comparing the proportion of specific tumours in the first degree relatives of the CLL practice cohort with corresponding proportions of population-based cancer registry data.</p> <p>Results</p> <p>18 (41%) male and 5 (23%) female CLL probands had multiple malignancies, e.g. 2 meningiomas, 7 and 19 years after diagnosis of CLL. 46 (12%) first degree relatives had malignancies with an excess of CLL. Other conspicuous familial associations are CLL with malignancies of the upper GI tract (oesophagus, stomach) and of the nervous system.</p> <p>Conclusion</p> <p>1. Chronic lymphocytic leukaemia clusters in some families like any other disease. Predisposition genes should be searched. 2. Cancer prevention and early detection should be continued in CLL patients because of their longevity and high risk for multiple malignancies. 3. The overrepresentation of upper GI malignancies in first degree relatives of CLL patients calls for targeted oesophago-gastroscopy screening studies.</p

Berufslaufbahnkonzepte: Instrumente zur Weiterentwicklung des Berufsbildungssystems?

In diesem Beitrag geht es um Berufslaufbahnkonzepte als Instrument zur Weiterentwicklung des Berufsbildungssystems. Die Autoren zeigen wesentliche Entstehungsbedingungen auf, die für die Formulierung von Berufslaufbahnkonzepten von Bedeutung sind. Dabei werden vor dem Hintergrund von sich verändernden Qualifikationsanforderungen und steigender beruflicher Mobilität insbesondere Entwicklungen bezüglich der abnehmenden Attraktivität des dualen Systems für leistungsstärkere Jugendliche (bzw. der Trend zur Akademisierung) einerseits und die Herausforderung, leistungsschwächere Jugendliche zu intergrieren andererseits, als relevant erachtet. Es folgen eine Verdichtung von Kernelementen bestehender Laufbahnkonzepte zu einem Laufbahnmodell sowie eine Diskussion der Funktionen von Laufbahnkonzepten. (DIPF/Orig.

Magnetic resonance imaging goes postmortem: noninvasive detection and assessment of myocardial infarction by postmortem MRI

Objective: To investigate the performance of postmortem magnetic resonance imaging (pmMRI) in identification and characterization of lethal myocardial infarction in a non-invasive manner on human corpses. Materials and Methods: Before forensic autopsy, 20 human forensic corpses were examined on a 1.5-T system for the presence of myocardial infarction. Short axis, transversal and longitudinal long axis images (T1-weighted; T2-weighted; PD-weighted) were acquired in situ. In subsequent autopsy, the section technique was adapted to short axis images. Histological investigations were conducted to confirm autopsy and/or radiological diagnoses. Results: Nineteen myocardial lesions were detected and age staged with pmMRI, of which 13 were histologically confirmed (chronic, subacute and acute). Six lesions interpreted as peracute by pmMRI showed no macroscopic or histological finding. Five of the six peracute lesions correlated well to coronary pathology, and one case displayed a severe hypertrophic alteration. Conclusion: pmMRI reliably demonstrates chronic, subacute and acute myocardial infarction in situ. In peracute cases pmMRI may display ischemic lesions undetectable at autopsy and routine histology. pmMRI has the potential to substantiate autopsy and to counteract the loss of reliable information on causes of death due to the recent disappearance of the clinical autops