On transitive orientations with restricted covering graphs

We consider the problem of finding a transitive orientation of a comparability graph, such that the edge set of its covering graph contains a given subset of edges. We propose a solution which employs the classical technique of modular tree decomposition. The method leads to a polynomial time algorithm to construct such an orientation or report that it does not exist.     

Nitrogen dynamics during till and no-till pasture restoration sequences in Rondônia,Brazil

The clearing of tropical rain forest in the Amazon basin has created large areas of cattle pasture that are now declining in productivity. Practices adopted by ranchers to restore productivity to degraded pastures have the potential to alter soil N availability and gaseous N losses from soils. We examined how soil inorganic N pools, net N mineralization and net nitrification rates, nitrification potential and NO and N₂O emissions from soils of a degraded pasture responded to the following restoration treatments: (1) soil tillage followed by replanting of grass and fertilization, (2) no-till application of non-selective herbicide, planting of rice, harvest followed by no-till replanting of grass and fertilization, and (3) the same no-till sequence with soybeans instead of rice. Tillage increased soil NH₄⁺ and NO₃^? pools but NH₄⁺ and NO₃^? pools remained relatively constant in the control and no-till treatments. Cumulative rates of net N mineralization and net nitrification during the first 6 months after treatment varied widely but were hightest in the tilled treatment. Emissions of NO and N₂O fluxes increased with tillage and with N fertilization. There were no clear relationships among rates of N fertilizer application, net N mineralization, net nitrification, NO, N₂O and total N oxide emissions. Our results indicate that pasture restoration sequences involving tilling and fertilizing will increase emissions of N oxides, but the magnitude of the increase is likely to differ based on timing of fertilizer application relative to the presence of plants and the magnitude of plant N demand. Emissions of N oxides appear to be decreased by the use of restoration sequences that minimize reductions in pasture grass cover.     

Rheological and morphological properties of high‐density polyethylene and poly(ethylene–octene) blends

The rheological and morphological properties of blends based on high‐density polyethylene (HDPE) and a commercial ethylene–octene copolymer (EOC) produced by metallocene technology were investigated. The rheological properties were evaluated in steady and dynamic shear experiments at 190°C in shear rates ranging from 90 s^?1 to 1500 s^?1 and frequency range between 10^?1 rad/s and 10² rad/s, respectively. These blends presented a high level of homogeneity in the molten state and rheological behavior was generally intermediate to those of the pure components. Scanning electron microscopy (SEM) showed that the blends exhibit dispersed morphologies with EOC domains distributed homogeneously and with particle size inferior to 2 μm. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2240–2246, 2002     

Optics clustered to output unique solutions: a multi-laser facility for combined single molecule and ensemble microscopy

Optics clustered to output unique solutions (OCTOPUS) is a microscopy platform that combines single molecule and ensemble imaging methodologies. A novel aspect of OCTOPUS is its laser excitation system, which consists of a central core of interlocked continuous wave and pulsed laser sources, launched into optical fibres and linked via laser combiners. Fibres are plugged into wall-mounted patch panels that reach microscopy end-stations in adjacent rooms. This allows multiple tailor-made combinations of laser colours and time characteristics to be shared by different end-stations minimising the need for laser duplications. This setup brings significant benefits in terms of cost effectiveness, ease of operation, and user safety. The modular nature of OCTOPUS also facilitates the addition of new techniques as required, allowing the use of existing lasers in new microscopes while retaining the ability to run the established parts of the facility. To date, techniques interlinked are multi-photon/multicolour confocal fluorescence lifetime imaging for several modalities of fluorescence resonance energy transfer (FRET) and time-resolved anisotropy, total internal reflection fluorescence, single molecule imaging of single pair FRET, single molecule fluorescence polarisation, particle tracking, and optical tweezers. Here, we use a well-studied system, the epidermal growth factor receptor network, to illustrate how OCTOPUS can aid in the investigation of complex biological phenomena.     

A particular approach for the Three-dimensional Packing Problem with additional constraints

This paper focuses on a restrained concretization of the general NP-hard Container Loading Problem that arises from a real world application. This particular problem can be informally described as: given different sets of bins and boxes, find the packing of the boxes into the smallest number of bins obeying some additional restrictions on the placement. The mathematical programming formulation that appears to better model this application is the Three-dimensional Bin-Packing Problem (3D-BPP) which is no more than an extension of the classic Bin-Packing Problem to the orthogonal packing of solid objects.We present an alternative non-linear formulation for the 3D-BPP version as well as new designed heuristic algorithms (CPBOX and BOXCP) for the approximation of the optimal solution using boxes and bins of heterogeneous dimensions. Moreover, we also present a heuristic specifically designed to work under very particular storage application restrictions. The numerical results indicate that all of these new heuristics have good performance standards especially when applied to replications of real input data.     

Linking Organizational Resources and Work Engagement to Employee Performance and Customer Loyalty: The Mediation of Service Climate.

This study examined the mediating role of service climate in the prediction of employee performance and customer loyalty. Contact employees (N=342) from 114 service units (58 hotel front desks and 56 restaurants) provided information about organizational resources, engagement, and service climate. Furthermore, customers (N=1,140) from these units provided information on employee performance and customer loyalty. Structural equation modeling analyses were consistent with a full mediation model in which organizational resources and work engagement predict service climate, which in turn predicts employee performance and then customer loyalty. Further analyses revealed a potential reciprocal effect between service climate and customer loyalty. Implications of the study are discussed, together with limitations and suggestions for future research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The Impact of Technological Opportunities and Innovative Capabilities on Firms’ Output Innovation

In this study, we analyse the effect that external sources of knowledge and absorptive capacity exert on a firm's output innovation. In addition, we examine the moderating influence of absorptive capacity on the effect that technological opportunities have on output innovation. Empirical research was carried out on a sample of 91 Spanish firms from the ceramic tile industry. Absorptive capacity is operationalized by ‘systematic or continuous R&D’ and output innovation by ‘percentage of sales from new products’. Technological opportunities are divided into several industry and non‐industry related variables. Our results show the positive effect that both the industry's technological opportunities and a systematic approach to R&D exert on output innovation. Moreover, firms with a systematic approach to R&D usually achieve higher innovation output than firms which do not follow this approach. The innovation results of this second group decrease as a result of embedded technology acquisition.     

VWF,Platelets and the Antiphospholipid Syndrome

The antiphospholipid syndrome (APS) is characterized by thrombosis and/or pregnancy morbidity with the persistent presence of antiphospholipid antibodies (aPLs). Laboratory criteria for the classification of APS include the detection of lupus anticoagulant (LAC), anti-cardiolipin (aCL) antibodies and anti-β2glycoprotein I (aβ2GPI) antibodies. Clinical criteria for the classification of thrombotic APS include venous and arterial thrombosis, along with microvascular thrombosis. Several aPLs, including LAC, aβ2GPI and anti-phosphatidylserine/prothrombin antibodies (aPS/PT) have been associated with arterial thrombosis. The Von Willebrand Factor (VWF) plays an important role in arterial thrombosis by mediating platelet adhesion and aggregation. Studies have shown that aPLs antibodies present in APS patients are able to increase the risk of arterial thrombosis by upregulating the plasma levels of active VWF and by promoting platelet activation. Inflammatory reactions induced by APS may also provide a suitable condition for arterial thrombosis, mostly ischemic stroke and myocardial infarction. The presence of other cardiovascular risk factors can enhance the effect of aPLs and increase the risk for thrombosis even more. These factors should therefore be taken into account when investigating APS-related arterial thrombosis. Nevertheless, the exact mechanism by which aPLs can cause thrombosis remains to be elucidated.     

Solidification of Silicon for Solar Cells

Silicon is the dominating material in solar cells. Monocrystalline and multicrystalline cells have approximately equal market shares and are produced from wafers, cut from single crystals produced by Czochralski (CZ) pulling or from polycrystalline ingots made by directional solidification, respectively. The present paper reviews how demands for lower cost, better yield, higher efficiency and use of less pure silicon in solar cells are addressed by advanced solidification processing. In monocrystalline solar silicon, careful growth control results in less point defects, and better efficiency. Continuous- or semi-continuous CZ growth processes are being developed for better productivity and lower cost. In multicrystalline solar silicon, extended defects such as dislocations and grain boundaries decrease efficiency, particularly in combination with new, less expensive, but more contaminated silicon feedstock. This problem is addressed by control of nucleation and growth of ingots with larger grains, preferred grain orientation and lower dislocation density.