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Parenthood Support Group

Público·7 miembros

Anomaly (2016)

Much of the record warmth for the globe can be attributed to record warmth in the global oceans. The annually-averaged temperature for ocean surfaces around the world was 0.75C (1.35F) higher than the 20th century average, edging out the previous record of 2015 by 0.01C (0.02F). A near-record strong El Niño in the Pacific Ocean at the beginning of the year led to some of the highest monthly global ocean temperatures on record, with January, February, March, April, June, July and August all ranking among the 12 warmest of all months in the 137-year record. January, February, and March each observed a monthly temperature at least 0.8C (1.4F) above average. This was a continuation of a high temperature threshold first crossed in September 2015.The El Niño dissipated in spring and was replaced by weak La Niña conditions near the end of the year. Even so, global ocean temperatures remained high, with the December temperature elevated at 0.61C (1.10F) above the 20th century average, an anomaly not achieved in the record until June 2009.

Anomaly (2016)

Because land surfaces generally have low heat capacity relative to oceans, temperature anomalies can vary greatly between months. In 2016, the average monthly land temperature anomaly ranged from +2.35C (+4.23F) in March, as noted above, to +0.95C (+1.71F) in November, a difference of 1.40C (2.52F). The ocean has a much higher heat capacity than land and thus anomalies tend to vary less over monthly timescales. During the year, the global monthly ocean temperature anomaly fell from +0.85C (+1.53F) in January to +0.61C (+1.10F) in December, a difference of 0.24C (0.43F).

HfTe5 is predicted to be a promising platform for studying topological phases. Here through an electrical transport study, we present an observation of chiral anomaly and ultrahigh mobility in HfTe5 crystals. Negative magnetoresistivity in HfTe5 is observed when the external magnetic and electrical fields are parallel (B//E) and quickly disappears once B deviates from the direction of E. Quantitative fitting further confirms the chiral anomaly as the underlying physics. Moreover, by analyzing the conductivity tensors of longitudinal and Hall traces, ultrahigh mobility and ultralow carrier density are revealed in HfTe5, which paves the way for potential electronic applications.

Strain can be induced by stretching and compressing crystals or by propagating sound waves. In graphene, a quintessential two-dimensional material with Dirac fermions, previous research has demonstrated the presence of strain-induced fields. Here, we explore the physics of strain-induced fields in three spatial dimensions in Dirac and Weyl semimetals shaped into very small wires (diameters on the order of hundreds of nanometers) or films. We consider both torsional and unidirectional strain. Using model calculations and numerical simulations, we find that these fields have several unusual experimentally observable consequences, including the chiral anomaly in the complete absence of real electromagnetic fields.

We propose a theory of one of the most economically significant stock market anomalies, i.e. the "profitability" anomaly. In our model, investors forecast future profits using a signal and sticky belief dynamics. In this model, past profits forecast future returns (the profitability anomaly). Using analyst forecast data, we measure expectation stickiness at the firm level and find strong support for three additional predictions of the model: (1) analysts are on average too pessimistic regarding the future profits of high profit firms, (2) the profitability anomaly is stronger for stocks which are followed by stickier analysts, and (3) it is also stronger for stocks with more persistent profits.

Background: Poland anomaly is a sporadic, phenotypically variable congenital condition usually characterized by unilateral pectoral muscle agenesis and ipsilateral hand deformity. Methods: A comprehensive review of the medical literature on Poland anomaly was performed using a Medline search. Results: Poland anomaly is a sporadic, phenotypically variable congenital condition usually characterized by unilateral, simple syndactyly with ipsilateral limb hypoplasia and pectoralis muscle agenesis. Operative management of syndactyly in Poland anomaly is determined by the severity of hand involvement and the resulting anatomical dysfunction. Syndactyly reconstruction is recommended in all but the mildest cases because most patients with Poland anomaly have notable brachydactyly, and digital separation can improve functional length. Conclusions: Improved understanding the etiology and presentation of Poland anomaly can improve clinician recognition and management of this rare congenital condition.

The Accident Investigation Team continues to make progress in examining the anomaly on September 1 that led to the loss of a Falcon 9 and its payload at Launch Complex 40 (LC-40), Cape Canaveral Air Force Station, Florida.

Overall, the report shows that data completeness and quality improved compared to the previous year, particularly for standards 8a and 8b that relate to the timely referral of women who have a suspected/identified anomaly at the screening scan.

Weyl semimetals provide the realization of Weyl fermions in solid-state physics. Among all the physical phenomena that are enabled by Weyl semimetals, the chiral anomaly is the most unusual one. Here, we report signatures of the chiral anomaly in the magneto-transport measurements on the first Weyl semimetal TaAs. We show negative magnetoresistance under parallel electric and magnetic fields, that is, unlike most metals whose resistivity increases under an external magnetic field, we observe that our high mobility TaAs samples become more conductive as a magnetic field is applied along the direction of the current for certain ranges of the field strength. We present systematically detailed data and careful analyses, which allow us to exclude other possible origins of the observed negative magnetoresistance. Our transport data, corroborated by photoemission measurements, first-principles calculations and theoretical analyses, collectively demonstrate signatures of the Weyl fermion chiral anomaly in the magneto-transport of TaAs.

Recently, there has been considerable progress in understanding the correspondence between high-energy and condensed matter physics, which has led to deeper knowledge of important topics in physics such as spontaneous symmetry breaking, phase transitions and renormalization. Such knowledge has, in turn, greatly helped physicists and materials scientists to better understand magnets, superconductors and other novel materials, leading to important practical device applications. Here, we present the signatures of the chiral anomaly in a low-energy condensed matter Weyl system. In order to measure the chiral anomaly in a solid-state system, one needs to find a perturbation that couples differently to the two Weyl fermions of opposite chiralities. This is most naturally realized in a Weyl semimetal, in which the two Weyl cones are separated in momentum space. Recent theoretical and experimental advances have shown that Weyl fermions can arise in the bulk of certain novel semimetals with nontrivial topology7,8,9,10,11,12,13,14,15,16. A Weyl semimetal is a bulk crystal whose low-energy excitations satisfy the Weyl equation. Therefore, the conduction and valence bands touch at discrete points, the Weyl nodes, with a linear dispersion relation in all three momentum space directions moving away from the Weyl node. The nontrivial topological nature of a Weyl semimetal guarantees that Weyl fermions with opposite chiralities are separated in momentum space (Fig. 1a), and host a monopole and an antimonopole of Berry flux in momentum space, respectively (Fig. 1b). In this situation, parallel magnetic and electric fields can pump electrons between Weyl cones of opposite chirality that are separated in momentum space (Fig. 1a). This process violates the conservation of the the chiral charge, meaning that the number of particles of left and right chirality are not separately conserved5,17,18,19,20,21,22,23,24,25,26, giving rise to an analogue of the chiral anomaly in a condensed matter system. Apart from this elegant analogy and correspondence between condensed matter and high-energy physics, the chiral anomaly also serves as a crucial transport signature for Weyl fermions in a Weyl semimetal phase. Furthermore, theoretical studies have recently suggested that it has potential applications27.

In this paper, we perform magneto-transport experiments on the Weyl semimetal TaAs12,13,14,16. We observe a negative longitudinal magnetoresistance (LMR) in the presence of parallel magnetic and electric fields, which is indicative of the chiral anomaly due to Weyl fermions. On the other hand, due to the complicated nature of the magnetoresistence28,29,30,31,32,33,34,35,36,37,38, an unambiguous demonstration of the chiral anomaly remains lacking despite the volume of works reporting negative LMR39,40,41,42,43,44. Our data and careful analyses, which go beyond a simple observation of a negative LMR, allow us to systematically exclude other possible origins for the observed negative LMR. These data strongly support the chiral anomaly due to Weyl fermions in TaAs. Our studies demonstrate a low-energy platform where the fundamental physics of Weyl fermions and quantum anomalies can be studied in a piece of solid metal17,18,19,20,21,22,23,24,25,26,27.

(a) Chemical potential EF dependence of the chiral coefficient CW. We expect the chiral coefficient CW to decay as a function of . (b) Angle ( versus ) dependence of the chiral coefficient CW. (c) Density of states (g(E)) of the bulk electronic structure of TaAs shows a slow variation as a function of energy. The Berry curvature increases markedly at the energy close to the Weyl nodes. (d) Distribution of the square of the Berry curvature as a function of kz and energy E, evidencing that the Weyl points are the dominant source of Berry curvature. The plot is integrated with respect to kx and ky over the whole Brillouin zone. (e)Temperature dependence of the axial charge relaxation time for sample a1. (f) A cartoon illustrating the chiral anomaly based on our LMR data. The chiral anomaly leads to the axial charge pumping, . This causes a population imbalance difference between the Weyl cones with the opposite chiralities. The charge-pumping effect is balanced by the axial charge relaxation, characterized by the time scale (refs 24, 26, 36). Note that the axial charge relaxation time can be directly obtained from the observed negative LMR data through the chiral coefficient . We also note that this is a cartoon that assumes the Fermi level at zero B field is exactly at the Fermi level. (g,h) Landau energy spectra of the left- and right-handed Weyl fermions in the presence of parallel electric and magnetic fields. 041b061a72

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