Magnetic microspherules associated with the K/T and upper Eocene extinction events

Magnetic microspherules were identified in over 20 K/T boundary sites, and in numerous Deep Sea Drilling Project (DSDP) cores from the Caribbean and Pacific, synchronous with the extinction of several radiolarian species near the end of the Eocene. The K/T magnetic spherules are of particular interest as carriers of Ir and other siderophiles generally found in abundance in K/T boundary clay. Furthermore the textures and unusual chemistry of their component magnetic phases indicate an origin at high temperature, possibly related to (an) unusual event(s) marking the end of the Cretaceous and Eocene periods. Their origin, along with the non-magnetic (sanidine) spheules, is generally ascribed directly to megaimpact events hypothesized to have periodically disrupted life on Earth. A survey of microspherical forms associated with known meteorite and impact derived materials reveals fundamental differences from the extinction related spherules. Low temperature magnetic experiments on the K/T and Upper Eocene spheroids indicate that, unlike tektites, extremely small superparamagnetic carriers are not present in abundance. The extensive subaerial exposure of Cretaceous combustible black shale during sea level regression in the latest Cretaceous represents a potential source for the magnetic spheroids found in certain K/T boundary clays. The recent discovery of high Ir abundances distributed above and below the K/T boundary within shallow water sediments in Israel, which also contain the most extensive known zones of combustion metamorphism, the so called Mottled Zone, adds a further dramatic footnote to the proposed association between the magnetic spheroids and combustion of organic shales. Interestingly, the Mottled Zone also contains the rare mineral magnesioferrite, which was identified both within the K/T magnetic spheroids and as discrete crystals in boundary clay from marine and continental sites

Dead Zone Accretion Flows in Protostellar Disks

Planets form inside protostellar disks in a dead zone where the electrical resistivity of the gas is too high for magnetic forces to drive turbulence. We show that much of the dead zone nevertheless is active and flows toward the star while smooth, large-scale magnetic fields transfer the orbital angular momentum radially outward. Stellar X-ray and radionuclide ionization sustain a weak coupling of the dead zone gas to the magnetic fields, despite the rapid recombination of free charges on dust grains. Net radial magnetic fields are generated in the magneto-rotational turbulence in the electrically conducting top and bottom surface layers of the disk, and reach the midplane by Ohmic diffusion. A toroidal component to the fields is produced near the midplane by the orbital shear. The process is similar to the magnetization of the Solar tachocline. The result is a laminar, magnetically-driven accretion flow in the region where the planets form.Comment: 12 pages, 4 figure

MODEL OF A COMPUTER SYSTEM FOR SELECTION OF OPERATING PARAMETERS FOR TRANSPORT VEHICLES IN THE ASPECT OF THEIR DURABILITY

The article presents a new method of selecting operating parameters of vehicles which allows to prolong their useful life. The theoretical and practical aspects of the new approach were discussed. The key methods of optimizing the use of vehicles and their transport routes were analysed. The proposed method of selecting operating parameters of transport vehicles was based on elements of the dynamic programming model using heuristic algorithms. A model and then an algorithm and a computer program for selecting operating parameters for vehicles were developed

Magnetism of nakhlites and chassignites

Hysteresis measurements on three shergottite and two nakhlite meteorites indicate single domain grain size behavior for the highly shocked Shergotty, Zagami, and EETA 79001 meteorites, with more multidomain-like behavior for the unshocked Nakhla and Governador Valadares meteorites. High viscosity and initial susceptibility for Antarctic shergottite ALHA 7705 indicate the presence of superparamagnetic grains in this specimen. Thermomagnetic analysis indicate Shergotty and Zagami as the least initially oxidized, while EETA 79001 appears to be the most oxidized. Cooling of the meteorite samples from high temperature in air results in a substantial increase in magnetization due to the production of magnetite through oxidation exsolution of titanomagnetite. However, vacuum heating substantially suppresses this process, and in the case of EETA 79001 and Nakhla, results in a rehomogenization of the titanomagnetite grains. Remanence measurements on several subsamples of Shergotty and Zagami meteorites reveal a large variation in intensity that does not seem related to the abundance of remanence carriers. The other meteorites carry only weak remanence, suggesting weak magnetizing fields as the source of their magnetic signal. The meteorites' weak field environment is consistent with Martian or asteroidal body origin but inconsistent with terrestrial origin

How to deal with reality when we're not built to

Philip K. Dick’s writing can be infuriatingly confusing. It feeds readers many ambiguoussignals that convey no real sense of closure—and The Man in the High Castle is no exception. Perhaps bewildering the audience is the intent, not a side-effect. We crave closure for many of the questions we find in Dick’s books, and he consistently denies us any real sense of arriving at definite answers. Lingering confusion and the gnawing feeling that the true nature of reality is just out of our grasp have been the dominant themes of both Dick’s narratives and philosophical and psychological studies for decades. Together, they all attest to how important understanding and embracing confusion can be in the business of dealing with reality

Towards nanophotonic optical isolation via inverse design of energy transfer in non-reciprocal media

In this work we generalise the adjoint method of inverse design to nonreciprocal media. As a test case, we use three-dimensional topology optimization via the level-set method to optimise one-way energy transfer for point-like source and observation points. To achieve this we introduce a suite of tools, chiefly what we term the `Faraday-adjoint' method which allows for efficient shape optimization in the presence of magneto-optical media. We carry out an optimization based on a very general equation that we derive for energy transfer in a nonreciprocal medium, and link finite-different time-domain numerics to analytics via a modified Born series generalised to a tensor permittivity. This work represents a stepping stone towards practical nanophotonic optical isolation, often regarded as the `holy grail' of integrated photonics

Seasonal Affective Disorder Treatment: Light Therapy versus SSRI Therapy

To determine the effect of pharmacological and nonpharmacological treatments for seasonal depression in college students, we asked the following evidence-based PICO question: In college students (ages 18-25) with seasonal affective disorder (SAD), how does SSRI (Selective Serotonin Reuptake Inhibitor) therapy compared to light therapy affect seasonal depression syndrome? Seasonal affective disorder is synonymously used with the terminology seasonal depression due to the clinical manifestations that encompass depression, such as low energy, feelings of sadness, emptiness, or hopelessness. SAD begins in the fall months and peaks in the winter months due to a decrease in Vitamin D and ultraviolet (UV) ray exposure from the sun. Our search for research articles was conducted by utilizing CINAHL, PUBMed, NLM, Gale Academic Library, and The American Journal of Psychiatry. Chosen articles were required to have been published on or after January 1, 2017. All articles within this review were required to match selected keywords and phrases and published on or after January 1, 2017. Articles that did not meet these requirements were excluded from this study. Eleven articles were selected that fell within the search criteria. The research implies that light therapy is just, if not more, effective in treating SAD than SSRI therapy. In multiple studies, the conjoined use of the two therapies, light and SSRI, provided the population with the greatest benefit