University of Tsukuba

About: University of Tsukuba is a education organization based out in Tsukuba, Ibaraki, Japan. It is known for research contribution in the topics: Population & Gene. The organization has 36352 authors who have published 79483 publications receiving 1934752 citations. The organization is also known as: Tsukuba daigaku & Tsukuba University.

Theory on Rates of Excitation-Energy Transfer between Molecular Aggregates through Distributed Transition Dipoles with Application to the Antenna System in Bacterial Photosynthesis

Abstract: It has often been observed in the light-harvesting antenna system of bacterial photosynthesis that excitation-energy transfer (EET) takes place very rapidly to or from a nearly (or completely) optically forbidden state. So far, the rate constant of EET has usually been calculated by Forster's formula, which regards EET as arising from the overlap integral between the luminescence spectrum of the excitation donor and the absorption spectrum of its acceptor. The observed EETs are much faster than expected from this formula, since the transition dipole as a whole nearly (or completely) vanishes in this state, giving a very small (or completely vanishing) Forster's overlap integral. We note in these EETs that at least one of the donor and acceptor is an aggregate of chromophores. Individual chromophores comprising the aggregate retain nonvanishing transition dipoles, even if their sum nearly (or completely) vanishes at an exciton state which is nearly (or completely) optically forbidden therein. EET to (or fr...

Cooperation in Evolving Social Networks

Abstract: We study the problem of cooperative behavior emerging in an environment where individual behaviors and interaction structures coevolve. Players not only learn which strategy to adopt by imitating the strategy of the best-performing player they observe, but also choose with whom they should interact by selectively creating and/or severing ties with other players based on a myopic cost-benefit comparison. We find that scalable cooperation---that is, high levels of cooperation in large populations---can be achieved in sparse networks, assuming that individuals are able to sever ties unilaterally and that new ties can only be created with the mutual consent of both parties. Detailed examination shows that there is an important trade-off between local reinforcement and global expansion in achieving cooperation in dynamic networks. As a result, networks in which ties are costly and local structure is largely absent tend to generate higher levels of cooperation than those in which ties are made easily and friends of friends interact with high probability, where the latter result contrasts strongly with the usual intuition.

Effect of Mechanical Thrombectomy Without vs With Intravenous Thrombolysis on Functional Outcome Among Patients With Acute Ischemic Stroke: The SKIP Randomized Clinical Trial.

Abstract: Importance Whether intravenous thrombolysis is needed in combination with mechanical thrombectomy in patients with acute large vessel occlusion stroke is unclear. Objective To examine whether mechanical thrombectomy alone is noninferior to combined intravenous thrombolysis plus mechanical thrombectomy for favorable poststroke outcome. Design, Setting, and Participants Investigator-initiated, multicenter, randomized, open-label, noninferiority clinical trial in 204 patients with acute ischemic stroke due to large vessel occlusion enrolled at 23 hospital networks in Japan from January 1, 2017, to July 31, 2019, with final follow-up on October 31, 2019. Interventions Patients were randomly assigned to mechanical thrombectomy alone (n = 101) or combined intravenous thrombolysis (alteplase at a 0.6-mg/kg dose) plus mechanical thrombectomy (n = 103). Main Outcomes and Measures The primary efficacy end point was a favorable outcome defined as a modified Rankin Scale score (range, 0 [no symptoms] to 6 [death]) of 0 to 2 at 90 days, with a noninferiority margin odds ratio of 0.74, assessed using a 1-sided significance threshold of .025 (97.5% CI). There were 7 prespecified secondary efficacy end points, including mortality by day 90. There were 4 prespecified safety end points, including any intracerebral hemorrhage and symptomatic intracerebral hemorrhage within 36 hours. Results Among 204 patients (median age, 74 years; 62.7% men; median National Institutes of Health Stroke Scale score, 18), all patients completed the trial. Favorable outcome occurred in 60 patients (59.4%) in the mechanical thrombectomy alone group and 59 patients (57.3%) in the combined intravenous thrombolysis plus mechanical thrombectomy group, with no significant between-group difference (difference, 2.1% [1-sided 97.5% CI, −11.4% to ∞]; odds ratio, 1.09 [1-sided 97.5% CI, 0.63 to ∞];P = .18 for noninferiority). Among the 7 secondary efficacy end points and 4 safety end points, 10 were not significantly different, including mortality at 90 days (8 [7.9%] vs 9 [8.7%]; difference, –0.8% [95% CI, –9.5% to 7.8%]; odds ratio, 0.90 [95% CI, 0.33 to 2.43];P > .99). Any intracerebral hemorrhage was observed less frequently in the mechanical thrombectomy alone group than in the combined group (34 [33.7%] vs 52 [50.5%]; difference, –16.8% [95% CI, –32.1% to –1.6%]; odds ratio, 0.50 [95% CI, 0.28 to 0.88];P = .02). Symptomatic intracerebral hemorrhage was not significantly different between groups (6 [5.9%] vs 8 [7.7%]; difference, –1.8% [95% CI, –9.7% to 6.1%]; odds ratio, 0.75 [95% CI, 0.25 to 2.24];P = .78). Conclusions and Relevance Among patients with acute large vessel occlusion stroke, mechanical thrombectomy alone, compared with combined intravenous thrombolysis plus mechanical thrombectomy, failed to demonstrate noninferiority regarding favorable functional outcome. However, the wide confidence intervals around the effect estimate also did not allow a conclusion of inferiority. Trial Registration umin.ac.jp/ctr Identifier:UMIN000021488