Wrocław University of Technology

About: Wrocław University of Technology is a education organization based out in Wrocław, Poland. It is known for research contribution in the topics: Laser & Computer science. The organization has 13115 authors who have published 31279 publications receiving 338694 citations.

Critical closing pressure determined with a model of cerebrovascular impedance

Abstract: Critical closing pressure (CCP) is the arterial blood pressure (ABP) at which brain vessels collapse and cerebral blood flow (CBF) ceases. Using the concept of impedance to CBF, CCP can be expressed with brain-monitoring parameters: cerebral perfusion pressure (CPP), ABP, blood flow velocity (FV), and heart rate. The novel multiparameter method (CCPm) was compared with traditional transcranial Doppler (TCD) calculations of CCP (CCP1). Digital recordings of ABP, intracranial pressure (ICP), and TCD-based FV from previously published studies of 29 New Zealand White rabbits were reanalyzed. Overall, CCP1 and CCPm showed correlation across wide ranges of ABP, ICP, and PaCO2 (R=0.93, P<0.001). Three physiological perturbations were studied: increase in ICP (n=29) causing both CCP1 and CCPm to increase (P<0.001 for both); reduction of ABP (n=10) resulting in decrease of CCP1 (P=0.006) and CCPm (P=0.002); and controlled increase of PaCO2 (n=8) to hypercapnic levels, which decreased CCP1 and CCPm, albeit insignificantly (P=0.123 and P=0.306 respectively), caused by a spontaneous significant increase in ABP (P=0.025). Multiparameter mathematical model of critical closing pressure explains the relationship of CCP on brain-monitoring variables, allowing the estimation of CCP during cases such as hypercapnia-induced hyperemia, where traditional calculations, like CCP1, often reach negative non-physiological values.

New block properties for the permutation flow shop problem with application in tabu search

Abstract: This paper deals with the classic flow-shop scheduling problem with the make-span criterion. Some new properties of the problem associated with the so-called blocks have been presented and discussed. The properties allow us to skip some non-perspective solutions during the search of the solution space. Applied to local search algorithms, they result in a significant reduction of neighbourhood size and quickly direct the search trajectory to promising regions of the solution space. The implementation of the proposed properties in a tabu search algorithm is also presented. Computational experiments (up to 500 jobs and 20 machines) are given and compared with the results yielded by the best known algorithms.

Size and Shape Resonances in Second Harmonic Generation from Silver Nanocavities

Abstract: The nonlinear response of subwavelength nanocavities in thin silver films are investigated. We report on significant enhancements of the second harmonic generation (SHG) when the fundamental wavelength matches dimensional resonances within the nanocavities. The nonlinear polarization properties of the nanocavities are studied as well and found to be correlated with the cavity shape and symmetry. In some nanocavities with internal nanocorrugations, giant field enhancements are observed, making them excellent candidates for high sensitivity spectroscopy.