Topology and energy transport in networks of interacting photosynthetic complexes

We address the role of topology in the energy transport process that occurs in networks of photosynthetic complexes. We take inspiration from light harvesting networks present in purple bacteria and simulate an incoherent dissipative energy transport process on more general and abstract networks, considering both regular structures (Cayley trees and hyperbranched fractals) and randomly-generated ones. We focus on the the two primary light harvesting complexes of purple bacteria, i.e., the LH1 and LH2, and we use network-theoretical centrality measures in order to select different LH1 arrangements. We show that different choices cause significant differences in the transport efficiencies, and that for regular networks centrality measures allow to identify arrangements that ensure transport efficiencies which are better than those obtained with a random disposition of the complexes. The optimal arrangements strongly depend on the dissipative nature of the dynamics and on the topological properties of the networks considered, and depending on the latter they are achieved by using global vs. local centrality measures. For randomly-generated networks a random arrangement of the complexes already provides efficient transport, and this suggests the process is strong with respect to limited amount of control in the structure design and to the disorder inherent in the construction of randomly-assembled structures. Finally, we compare the networks considered with the real biological networks and find that the latter have in general better performances, due to their higher connectivity, but the former with optimal arrangements can mimic the real networks' behaviour for a specific range of transport parameters. These results show that the use of network-theoretical concepts can be crucial for the characterization and design of efficient artificial energy transport networks.Comment: 14 pages, 16 figures, revised versio

Minimum output entropy of bosonic channels: a conjecture

The von Neumann entropy at the output of a bosonic channel with thermal noise is analyzed. Coherent-state inputs are conjectured to minimize this output entropy. Physical and mathematical evidence in support of the conjecture is provided. A stronger conjecture--that output states resulting from coherent-state inputs majorize the output states from other inputs--is also discussed.Comment: 15 pages, 12 figure

Technical note: Problem-specific variators in a genetic algorithm for the optimization of drinking water networks

Genetic algorithms can be a powerful tool for the automated design of optimal drinking water distribution networks. Fast convergence of such algorithms is a crucial factor for successful practical implementation at the drinking water utility level. In this technical note, we therefore investigate the performance of a suite of genetic variators that was tailored to the optimization of a least-cost network design. Different combinations of the variators are tested in terms of convergence rate and the robustness of the results during optimization of the real-world drinking water distribution network of Sittard, the Netherlands. The variator configurations that reproducibly reach the furthest convergence after 105 function evaluations are reported. In the future these may aid in dealing with the computational challenges of optimizing real-world networks.</p

Het nieuwe telen van aardbeien : topkwaliteit aardbeien telen met 14 kuub gas

Op een glasbedrijf in Limburg heeft tussen begin augustus 2009 en medio juni 2010 energieonderzoek bij aardbeien plaatsgevonden. Het doel van het project is om minimaal 20% energie te besparen en de vruchtkwaliteit te verbeteren. De hypothese is, dat energie kan worden bespaard door vroeg te planten in augustus, aanpassing van kasklimaat in nazomer en herfst waardoor in januari er minder warmtevraag is. Ondanks de grote verschillen in klimaat waren de uiteindelijke verschillen in plantontwikkeling, productie en vruchtkwaliteit erg klein. Doordat in de gekoelde afdelingen een lagere temperatuur werd gerealiseerd ontwikkelden de planten zich in die afdelingen trage

Do tonic itch and pain stimuli draw attention towards their location?

Background. Although itch and pain are distinct experiences, both are unpleasant, may demand attention, and interfere with daily activities. Research investigating the role of attention in tonic itch and pain stimuli, particularly whether attention is drawn to the stimulus location, is scarce. Methods. In the somatosensory attention task, fifty-three healthy participants were exposed to 35-second electrical itch or pain stimuli on either the left or right wrist. Participants responded as quickly as possible to visual targets appearing at the stimulated location (ipsilateral trials) or the arm without stimulation (contralateral trials). During control blocks, participants performed the visual task without stimulation. Attention allocation at the itch and pain location is inferred when responses are faster ipsilaterally than contralaterally. Results. Results did not indicate that attention was directed towards or away from the itch and pain location. Notwithstanding, participants were slower during itch and pain than during control blocks. Conclusions. In contrast with our hypotheses, no indications were found for spatial attention allocation towards the somatosensory stimuli. This may relate to dynamic shifts in attention over the time course of the tonic sensations. Our secondary finding that itch and pain interfere with task performance is in-line with attention theories of bodily perception

Risk Prediction in Acute Calculous Cholecystitis: A Systematic Review and Meta-analysis of Prognostic Factors and Predictive Models

BACKGROUND: Laparoscopic cholecystectomy is the main treatment of acute cholecystitis. Although considered relatively safe, it carries 6%–9% risk of major complications and 0.1%–1% risk of mortality. There is no consensus regarding the evaluation of the preoperative risks, and the management of patients with acute cholecystitis is usually guided by surgeon's personal preferences. We assessed the best method to identify patients with acute cholecystitis who are at high risk of complications and mortality. METHODS: We performed a systematic review of studies that reported the preoperative prediction of outcomes in people with acute cholecystitis. We searched the Cochrane Library, MEDLINE, EMBASE, WHO ICTRP, ClinicalTrials.gov, and Science Citation Index Expanded until April 27, 2019. We performed a meta-analysis when possible. RESULTS: Six thousand eight hundred twenty-seven people were included in one or more analyses in 12 studies. Tokyo guidelines 2013 (TG13) predicted mortality (two studies; Grade 3 versus Grade 1: odds ratio [OR] 5.08, 95% confidence interval [CI] 2.79–9.26). Gender predicted conversion to open cholecystectomy (two studies; OR 1.59, 95% CI 1.06–2.39). None of the factors reported in at least two studies had significant predictive ability of major or minor complications. CONCLUSION: There is significant uncertainty in the ability of prognostic factors and risk prediction models in predicting outcomes in people with acute calculous cholecystitis. Based on studies of high risk of bias, TG13 Grade 3 severity may be associated with greater mortality than Grade 1. Early referral of such patients to high-volume specialist centers should be considered. Further well-designed prospective studies are necessary

Postgraduate Research Studies handbook

2001 handbook for Postgraduate Research Studie