Optics offers unique opportunities for reducing energy in information processing and communications while simultaneously resolving the problem of interconnect bandwidth density inside machines. Such ...energy dissipation overall is now at environmentally significant levels; the source of that dissipation is progressively shifting from logic operations to interconnect energies. Without the prospect of substantial reduction in energy per bit communicated, we cannot continue the exponential growth of our use of information. The physics of optics and optoelectronics fundamentally addresses both interconnect energy and bandwidth density, and optics may be the only scalable solution to such problems. Here we summarize the corresponding background, status, opportunities, and research directions for optoelectronic technology and novel optics, including subfemtojoule devices in waveguide and novel two-dimensional (2-D) array optical systems. We compare different approaches to low-energy optoelectronic output devices and their scaling, including lasers, modulators and LEDs, optical confinement approaches (such as resonators) to enhance effects, and the benefits of different material choices, including 2-D materials and other quantum-confined structures. With such optoelectronic energy reductions, and the elimination of line charging dissipation by the use optical connections, the next major interconnect dissipations are in the electronic circuits for receiver amplifiers, timing recovery, and multiplexing. We show we can address these through the integration of photodetectors to reduce or eliminate receiver circuit energies, free-space optics to eliminate the need for timing and multiplexing circuits (while also solving bandwidth density problems), and using optics generally to save power by running large synchronous systems. One target concept is interconnects from ~1 cm to ~10 m that have the same energy (~10 fJ/bit) and simplicity as local electrical wires on chip.
With wide deployment of machine learning (ML)-based systems for a variety of applications including medical, military, automotive, genomic, multimedia, and social networking, there is great potential ...for damage from adversarial learning (AL) attacks. In this article, we provide a contemporary survey of AL, focused particularly on defenses against attacks on deep neural network classifiers. After introducing relevant terminology and the goals and range of possible knowledge of both attackers and defenders, we survey recent work on test-time evasion (TTE), data poisoning (DP), backdoor DP, and reverse engineering (RE) attacks and particularly defenses against the same. In so doing, we distinguish robust classification from anomaly detection (AD), unsupervised from supervised, and statistical hypothesis-based defenses from ones that do not have an explicit null (no attack) hypothesis. We also consider several scenarios for detecting backdoors. We provide a technical assessment for reviewed works, including identifying any issues/limitations, required hyperparameters, needed computational complexity, as well as the performance measures evaluated and the obtained quality. We then delve deeper, providing novel insights that challenge conventional AL wisdom and that target unresolved issues, including: robust classification versus AD as a defense strategy; the belief that attack success increases with attack strength, which ignores susceptibility to AD; small perturbations for TTE attacks: a fallacy or a requirement; validity of the universal assumption that a TTE attacker knows the ground-truth class for the example to be attacked; black, gray, or white-box attacks as the standard for defense evaluation; and susceptibility of query-based RE to an AD defense. We also discuss attacks on the privacy of training data. We then present benchmark comparisons of several defenses against TTE, RE, and backdoor DP attacks on images. The article concludes with a discussion of continuing research directions, including the supreme challenge of detecting attacks whose goal is not to alter classification decisions, but rather simply to embed, without detection, "fake news" or other false content.
The occurrence of false positive detections in presence-absence data, even when they occur infrequently, can lead to severe bias when estimating species occupancy patterns. Building upon previous ...efforts to account for this source of observational error, we established a general framework to model false positives in occupancy studies and extend existing modeling approaches to encompass a broader range of sampling designs. Specifically, we identified three common sampling designs that are likely to cover most scenarios encountered by researchers. The different designs all included ambiguous detections, as well as some known-truth data, but their modeling differed in the level of the model hierarchy at which the known-truth information was incorporated (site level or observation level). For each model, we provide the likelihood, as well as R and BUGS code needed for implementation. We also establish a clear terminology and provide guidance to help choosing the most appropriate design and modeling approach.
We derive four laws relating the absorptivity and emissivity of thermal emitters. Unlike the original Kirchhoff radiation law derivations, these derivations include diffraction, and so are valid also ...for small objects, and can also cover nonreciprocal objects. The proofs exploit two recent approaches. First, we express all fields in terms of the mode-converter basis sets of beams; these sets, which can be uniquely established for any linear optical object, give orthogonal input beams that are coupled one-by-one to orthogonal output beams. Second, we consider thought experiments using universal linear optical machines, which allow us to couple appropriate beams and black bodies. Two of these laws can be regarded as rigorous extensions of previously known laws: One gives a modal version of a radiation law for reciprocal objects—the absorptivity of any input beam equals the emissivity into the “backward” (i.e., phase-conjugated) version of that beam; another gives the overall equality of the sums of the emissivities and the absorptivities for any object, including nonreciprocal ones. The other two laws, valid for reciprocal and nonreciprocal objects, are quite different from previous relations. One shows universal equivalence of the absorptivity of each mode-converter input beam and the emissivity into its corresponding scattered output beam. The other gives unexpected equivalences of absorptivity and emissivity for broad classes of beams. Additionally, we prove these orthogonal mode-converter sets of input and output beams are the ones that maximize absorptivities and emissivities, respectively, giving these beams surprising additional physical meaning.
ATP-binding cassette (ABC) transporters are important selective elements of the blood–brain barrier. They line the luminal plasma membrane of the brain capillary endothelium, facing the vascular ...space, and both protect the central nervous system from entry of neurotoxicants and limit the access of therapeutic drugs to the brain parenchyma. Recent studies highlight the multiple signaling pathways through which the expression and activity of P-glycoprotein and other ABC transporters are modulated in response to xenobiotics, stress and disease. The results show that increased transporter expression occurs in response to signals that activate specific transcription factors, including pregnane-X receptor, constitutive androstane receptor, nuclear factor-κB and activator protein-1, and that reduced transporter activity occurs rapidly and reversibly in response to signaling through Src kinase, protein kinase C and estrogen receptors. A detailed understanding of such regulation can provide the basis for improved neuroprotection and enhanced therapeutic drug delivery to the brain.
A Concise History of Mycotoxin Research Pitt, John I; Miller, J. David
Journal of agricultural and food chemistry,
08/2017, Volume:
65, Issue:
33
Journal Article
Peer reviewed
Toxigenic fungi and mycotoxins entered human food supplies about the time when mankind first began to cultivate crops and to store them from one season to the next, perhaps 10,000 years ago. The ...storage of cereals probably initiated the transition by mankind from hunter-gatherer to cultivator, at the same time providing a vast new ecological niche for fungi pathogenic on grain crops or saprophytic on harvested grain, many of which produced mycotoxins. Grains have always been the major source of mycotoxins in the diet of man and his domestic animals. In the historical context, ergotism from Claviceps purpurea in rye has been known probably for more than 2000 years and caused the deaths of many thousands of people in Europe in the last millennium. Known in Japan since the 17th century, acute cardiac beriberi associated with the consumption of moldy rice was found to be due to citreoviridin produced by Penicillium citreonigrum. This toxin was believed to be only of historic importance until its reemergence in Brazil a few years ago. Other Penicillium toxins, including ochratoxin A, once considered to be a possible cause of Balkan endemic nephropathy, are treated in a historical context. The role of Fusarium toxins in human and animal health, especially T-2 toxin in alimentary toxic aleukia in Russia in the 1940s and fumonisins in equine leucoencephalomalasia, is set out in some detail. Finally, this paper documents the story of the research that led to our current understanding of the formation of aflatoxins in grains and nuts, due to the growth of Aspergillus flavus and its role, in synergy with the hepatitis B virus, in human liver cancer. During a period of climate change and greatly reduced crop diversity on a global basis, researchers tasked with monitoring the food system need to be aware of fungal toxins that might have been rare in their working careers that can reappear.
There has been significant recent interest in synthetic dimensions, where internal degrees of freedom of a particle are coupled to form higher-dimensional lattices in lower-dimensional physical ...structures. For these systems, the concept of band structure along the synthetic dimension plays a central role in their theoretical description. Here we provide a direct experimental measurement of the band structure along the synthetic dimension. By dynamically modulating a resonator at frequencies commensurate with its mode spacing, we create a periodically driven lattice of coupled modes in the frequency dimension. The strength and range of couplings can be dynamically reconfigured by changing the modulation amplitude and frequency. We show theoretically and demonstrate experimentally that time-resolved transmission measurements of this system provide a direct readout of its band structure. We also realize long-range coupling, gauge potentials and nonreciprocal bands by simply incorporating additional frequency drives, enabling great flexibility in band structure engineering.
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