Nonlocal effects in atom-plasmon interactions

Nonlocal and quantum mechanical phenomena in noble metal nanostructures become increasingly crucial when the relevant length scales in hybrid nanostructures reach the few-nanometer regime. In practice, such mesoscopic effects at metal-dielectric interfaces can be described using exemplary surface-response functions (SRFs) embodied by the Feibelman $d$-parameters. Here we show that SRFs dramatically influence quantum electrodynamic phenomena -- such as the Purcell enhancement and Lamb shift -- for quantum emitters close to a diverse range of noble metal nanostructures interfacing different homogeneous media. Dielectric environments with higher permittivities are shown to increase the magnitude of SRFs calculated within the specular-reflection model. In parallel, the role of SRFs is enhanced in nanostructures characterized by large surface-to-volume ratios, such as thin planar metallic films or shells of core-shell nanoparticles. By investigating emitter quantum dynamics close to such plasmonic architectures, we show that decreasing the width of the metal region, or increasing the permittivity of the interfacing dielectric, leads to a significant change in the Purcell enhancement, Lamb shift, and visible far-field spontaneous emission spectrum, as an immediate consequence of SRFs. We anticipate that fitting the theoretically modelled spectra to experiments could allow for experimental determination of the $d$-parameters.Comment: 9 pages, 5 figure

Effective control of two-dimensional Rayleigh--B\'enard convection: invariant multi-agent reinforcement learning is all you need

Rayleigh-B\'enard convection (RBC) is a recurrent phenomenon in several industrial and geoscience flows and a well-studied system from a fundamental fluid-mechanics viewpoint. However, controlling RBC, for example by modulating the spatial distribution of the bottom-plate heating in the canonical RBC configuration, remains a challenging topic for classical control-theory methods. In the present work, we apply deep reinforcement learning (DRL) for controlling RBC. We show that effective RBC control can be obtained by leveraging invariant multi-agent reinforcement learning (MARL), which takes advantage of the locality and translational invariance inherent to RBC flows inside wide channels. The MARL framework applied to RBC allows for an increase in the number of control segments without encountering the curse of dimensionality that would result from a naive increase in the DRL action-size dimension. This is made possible by the MARL ability for re-using the knowledge generated in different parts of the RBC domain. We show in a case study that MARL DRL is able to discover an advanced control strategy that destabilizes the spontaneous RBC double-cell pattern, changes the topology of RBC by coalescing adjacent convection cells, and actively controls the resulting coalesced cell to bring it to a new stable configuration. This modified flow configuration results in reduced convective heat transfer, which is beneficial in several industrial processes. Therefore, our work both shows the potential of MARL DRL for controlling large RBC systems, as well as demonstrates the possibility for DRL to discover strategies that move the RBC configuration between different topological configurations, yielding desirable heat-transfer characteristics. These results are useful for both gaining further understanding of the intrinsic properties of RBC, as well as for developing industrial applications.Comment: 34 pages, 11 figures submitted to Physics of Fluid

How Integrated Ocean governance in the Barents Sea was created by a drive for increased oil production

-The Norwegian integrated management plan for the Lofoten–Barents Sea areas (BSMP) was initiated in 2002 following an international push for implementing ecosystem-based management, as well as a national drive to make new areas available for petroleum exploitation.. Governance of the plan was achieved through an inter-ministerial steering group working through its underlying institutions that have been tasked to work together during both development and implementation. This has achieved a high degree of integration across sectors and between government levels. Having the dual objectives of sustainable exploitation and conservation gives rise to a conflict over whether or not to allow petroleum industry access to the ecologically most valuable and vulnerable areas. There was an attempt at resolving this conflict by acquiring more knowledge, but the conflict is fundamentally a value-based question, which is impossible to resolve by gathering empirical knowledge alone. Nevertheless, the BSMP has been a positive vehicle for increasing the legitimacy of the complex decisions a modern society has to take in the management of ocean resources

Multisite Evaluation of the BD Max Extended Enteric Bacterial Panel for Detection of Yersinia enterocolitica, Enterotoxigenic Escherichia coli, Vibrio, and Plesiomonas shigelloides from Stool Specimens.

The purpose of this study was to perform a multisite evaluation to establish the performance characteristics of the BD Max extended enteric bacterial panel (xEBP) assay directly from unpreserved or Cary-Blair-preserved stool specimens for the detection of Yersinia enterocolitica, enterotoxigenic Escherichia coli (ETEC), Vibrio, and Plesiomonas shigelloides The study included prospective, retrospective, and prepared contrived specimens from 6 clinical sites. BD Max xEBP results were compared to the reference method, which included standard culture techniques coupled with alternate PCR and sequencing, except for ETEC, for which the reference method was two alternate PCRs and sequencing. Alternate PCR was also used to confirm the historical results for the retrospective specimens and for discrepant result analysis. A total of 2,410 unformed, deidentified stool specimens were collected. The prevalence in the prospective samples as defined by the reference method was 1.2% ETEC, 0.1% Vibrio, 0% Y. enterocolitica, and 0% P. shigelloides Compared to the reference method, the positive percent agreement (PPA) (95% confidence interval [CI]), negative percent agreement (NPA) (95% CI), and kappa coefficient (95% CI) for the BD Max xEBP assay for all specimens combined were as follows: ETEC, 97.6% (87.4 to 99.6), 99.8% (99.5 to 99.9), and 0.93 (0.87 to 0.99); Vibrio, 100% (96.4 to 100), 99.7% (99.4 to 99.8), and 0.96 (0.93 to 0.99); Y. enterocolitica, 99.0% (94.8 to 99.8), 99.9% (99.8 to 99.9), and 0.99 (0.98 to 1); P. shigelloides, 100% (96.4 to 100), 99.8% (99.5 to 99.9), and 0.98 (0.95 to 1), respectively. In this multicenter study, the BD Max xEBP showed a high correlation (kappa, 0.97; 95% CI, 0.95 to 0.98) with the conventional methods for the detection of ETEC, Vibrio, Y. enterocolitica, and P. shigelloides in stool specimens from patients suspected of acute gastroenteritis, enteritis, or colitis

Nonlinear photoluminescence in gold thin films

Promising applications in photonics are driven by the ability to fabricate crystal-quality metal thin films of controlled thickness down to a few nanometers. In particular, these materials exhibit a highly nonlinear response to optical fields owing to the induced ultrafast electron dynamics, which is however poorly understood on such mesoscopic length scales. Here, we reveal a new mechanism that controls the nonlinear optical response of thin metallic films, dominated by ultrafast electronic heat transport when the thickness is sufficiently small. By experimentally and theoretically studying electronic transport in such materials, we explain the observed temporal evolution of photoluminescence in pump-probe measurements that we report for crystalline gold flakes. Incorporating a first-principles description of the electronic band structures, we model electronic transport and find that ultrafast thermal dynamics plays a pivotal role in determining the strength and time-dependent characteristics of the nonlinear photoluminescence signal, which is largely influenced by the distribution of hot electrons and holes, subject to diffusion across the film as well as relaxation to lattice modes. Our findings introduce conceptually novel elements triggering the nonlinear optical response of nanoscale materials while suggesting additional ways to control and leverage hot carrier distributions in metallic films.Comment: 20 pages, 6 figures, 64 reference

Lessons on Marine Protected Area Management in Northern Boreal Regions from the United States and Norway

In comparison to tropical reef systems, relatively few marine protected areas (MPA’s) exist in temperate or subarctic systems (e.g., North Pacific and North Atlantic) where species diversity is lower, abundance of individual species is often higher, and many fish species exhibit large amounts of movement during one or more of their life stages, especially as adults. A review of MPA’s in three northern areas—the Northwest Atlantic, Northeast Atlantic, and the Northeast Pacific—indicates that MPA’s can be useful management tools towards fisheries management and habitat conservation. However, achieving fishery goals, such as sustainable use of the fisheries resources, will depend on population abundance (relative to unfished conditions) and fish behavior and movement. For example, depleted populations of stationary species such as Atlantic sea scallops, Placopecten magellanicus, in the Northeast Atlantic and European lobster, Homarus grammarus, in the North Sea have responded positively to small MPA’s, whereas migratory offshore Atlantic cod, Gadus morhua, and Pacific cod, Gadus macrocephalus, apparently do not appear to benefit from closed areas because of movement into fished areas. Efficient habitat conservation requires detailed habitat mapping on relevant spatial scales. In northern boreal systems with large remote areas, this information is difficult and expensive to access. An alternative strategy of closing and protecting unexploited areas has worked well for the Aleutian Island coral closure area in Alaska. MPA’s can be effective fisheries management tools when the species to be protected have been depleted and show a small to moderate level of movement, and reproductive success is ensured. MPA’s can be effective at preserving habitat when the design is based on scientific information and takes into account the impact on the user groups.publishedVersio

Mycoplasma genitalium Detected by Transcription-Mediated Amplification Is Associated With Chlamydia trachomatis in Adolescent Women

The clinical significance of Mycoplasma genitalium (MG) infection in adolescent women is poorly understood. We compared the prevalence of MG with that of other sexually transmitted organisms such as Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG), and Trichomonas vaginalis (TV) and assessed the associations of MG with sexual behaviors, genitourinary symptoms, physical and laboratory findings