匹配条件: “” ,找到相关结果约100条。
Sutural simplification in Physodoceratinae (Aspidoceratidae, Ammonitina)  [cached]
Checa, A.
Estudios Geologicos , 1987, DOI: 10.3989/egeol.87433-4600
Abstract: The estructural analysis of the shell septum interrelationship in sorne Jurassic ammonites allows us to conclude that sutural simplifications occurred throughout the phylogeny, were originated by alterations in the external morphology of the shell. In the case of Physodoceratinae the simplification observed in the morphology of the septal suture may have a double origin. First, an increase in the size of periumbilical tubercles may determine a shallowing of sutural elements and a shortening of saddle and lobe frilling. In other cases, shallowing is determined by a decrease in the whorl expansion rate, an apparent shortening of secondary branching not being observed. El análisis estructural de la interrelación concha-septo en algunos ammonites del Jurásico superior lleva a concluir que las simplificaciones suturales aparecidas a lo largo de la filogenia fueron originadas por alteraciones ocurridas en la morfología externa de la concha. En el caso concreto de la subfamilia Physodoceratinae, la simplificación observada en la morfología de la sutura puede tener un doble origen. En primer lugar, un incremento en el tama o de los tubérculos periumbilicales puede determinar una pérdida de profundidad de los elementos de la sutura. siempre acompa ada de una disminución en las indentaciones (frilling) de sillas y lóbulos. En otros casos el acortamiento en profundidad está determinado por una disminución de la tasa de expansión de la espira, sin que se observe un acortamiento aparente de las ramificaciones secundarias.
Elementary Derivation for Passage Times  [PDF]
Dorje C. Brody
Physics , 2003, DOI: 10.1088/0305-4470/36/20/314
Abstract: When a quantum system undergoes unitary evolution in accordance with a prescribed Hamiltonian, there is a class of states |psi> such that, after the passage of a certain time, |psi> is transformed into a state orthogonal to itself. The shortest time for which this can occur, for a given system, is called the passage time. We provide an elementary derivation of the passage time, and demonstrate that the known lower bound, due to Fleming, is typically attained, except for special cases in which the energy spectra have particularly simple structures. It is also shown, using a geodesic argument, that the passage times for these exceptional cases are necessarily larger than the Fleming bound. The analysis is extended to passage times for initially mixed states.
On the topology of adiabatic passage  [PDF]
L. P. Yatsenko,S Guerin,H. R. Jauslin
Physics , 2001, DOI: 10.1103/PhysRevA.65.043407
Abstract: We examine the topology of eigenenergy surfaces characterizing the population transfer processes based on adiabatic passage. We show that this topology is the essential feature for the analysis of the population transfers and the prediction of its final result. We reinterpret diverse known processes, such as stimulated Raman adiabatic passage (STIRAP), frequency-chirped adiabatic passage and Stark-chirped rapid adiabatic passage (SCRAP). Moreover, using this picture, we display new related possibilities of transfer. In particular, we show that we can selectively control the level which will be populated in STIRAP process in Lambda or V systems by the choice of the peak amplitudes or the pulse sequence.
First Passage Percolation with nonidentical passage times  [PDF]
Ghurumuruhan Ganesan
Mathematics , 2014,
Abstract: In this paper we consider first passage percolation on the square lattice \(\mathbb{Z}^d\) with passage times that are independent and have bounded \(p^{th}\) moment for some \(p > 6(1+d),\) but not necessarily identically distributed. For integer \(n \geq 1,\) let \(T(0,n)\) be the minimum time needed to reach the point \((n,\mathbf{0})\) from the origin. We prove that \(\frac{1}{n}\left(T(0,n) - \mathbb{E}T(0,n)\right)\) converges to zero in \(L^2\) and use a subsequence argument to obtain almost sure convergence. As a corollary, for i.i.d. passage times, we also obtain the usual almost sure convergence of \(\frac{T(0,n)}{n}\) to a constant \(\mu.\)
Purity in the Context of the Rite of Passage
Prof. Dr. Fuzuli Bayat
Journal of International Social Research , 2009,
Abstract: Purity is the passage of the state which is been appeared a phenomenon until mythological epoch to middle age in the Turkish cultural ecological system. But purity is not only passage of the state also is a possessive of secret knowledge and mediator in different worlds. In this article was researched a function of purity from the ancient age - shamanism to middle age - sophism popular. The cod of purity of our culture was researched in mythological and tasawwuf’s materials which are been gathered from different sources
Geodesics in First Passage Percolation  [PDF]
Christopher Hoffman
Mathematics , 2005,
Abstract: We consider a wide class of ergodic first passage percolation processes on Z^2 and prove that there exist at least four one-sided geodesics a.s. We also show that coexistence is possible with positive probability in a four color Richardson's growth model. This improves earlier results of Haggstrom and Pemantle, Garet and Marchand, and Hoffman who proved that first passage percolation has at least two geodesics and that coexistence is possible in a two color Richardson's growth model.
Primer registro del género Vinalesphinctes (Ammonitina) en el Oxfordiano de México: Significación bioestratigráfica y consideraciones paleobiogeográficas en el Jurásico Superior de América
López-Palomino, Rosario Isabel;Villase?or-Martínez, Ana Bertha;Olóriz-Sáez, Federico;
Revista mexicana de ciencias geológicas , 2006,
Abstract: the genus vinalesphinctes (ammonitina) is reported for the first time from mexico. the studied specimens -were collected from two oxfordian sections of the east-central mexico, huasteca region, hidalgo and san luis potosí states. two morphospecies have been identified, vinalesphinctes tamanensis and vinalesphinctes tenangensis. mexican, cuban and chilean vinalesphinctes are compared, and a late oxfordian, bifurcatus chron age is interpreted for the mexican forms. within the context of limitations derived from the scarcity of the material available, the taxonomical differentiation proposed for mexican vinalesphinctes is in accordance with the ecological interpretation (i. e., envisaged habitat), and reinforces hypotheses about endemism affecting ammonites during the chron bifurcatus in the american regions considered. however, additional research is necessary before giving a conclusive interpretation about the causal factors for the ammonite scarcity during the late oxfordian of the mexico-caribbean region.
Randomized First Passage Times  [PDF]
Sebastian Jaimungal,Alex Kreinin,Angelo Valov
Mathematics , 2009,
Abstract: In this article we study a problem related to the first passage and inverse first passage time problems for Brownian motions originally formulated by Jackson, Kreinin and Zhang (2009). Specifically, define $\tau_X = \inf\{t>0:W_t + X \le b(t) \}$ where $W_t$ is a standard Brownian motion, then given a boundary function $b:[0,\infty) \to \RR$ and a target measure $\mu$ on $[0,\infty)$, we seek the random variable $X$ such that the law of $\tau_X$ is given by $\mu$. We characterize the solutions, prove uniqueness and existence and provide several key examples associated with the linear boundary.
First Passage Problems in Biology  [PDF]
Tom Chou,Maria R. D'Orsogna
Quantitative Biology , 2014,
Abstract: Applications of first passage times in stochastic processes arise across a wide range of length and time scales in biological settings. After an initial technical overview, we survey representative applications and their corresponding models. Within models that are effectively Markovian, we discuss canonical examples of first passage problems spanning applications to molecular dissociation and self-assembly, molecular search, transcription and translation, neuronal spiking, cellular mutation and disease, and organismic evolution and population dynamics. In this last application, a simple model for stem-cell ageing is presented and some results derived. Various approximation methods and the physical and mathematical subtleties that arise in the chosen applications are also discussed.
First Passage Value  [PDF]
Cenk Oguz Saglam,Katie Byl
Computer Science , 2014,
Abstract: For many stochastic dynamic systems, the Mean First Passage Time (MFPT) is a useful concept, which gives expected time before a state of interest. This work is an extension of MFPT in several ways. (1) We show that for some systems the system-wide MFPT, calculated using the second largest eigenvalue only, captures most of the fundamental dynamics, even for quite complex, high-dimensional systems. (2) We generalize MFPT to Mean First Passage Value (MFPV), which gives a more general value of interest, e.g., energy expenditure, distance, or time. (3) We provide bounds on First Passage Value (FPV) for a given confidence level. At the heart of this work, we emphasize that for our goals, many hybrid systems can be approximated as Markov Decision Processes. So, many systems can be controlled effectively using this framework. However, our framework is particularly useful for metastable systems. Such systems exhibit interesting long-living behaviors from which they are guaranteed to inevitably escape (e.g., eventually arriving at a distinct failure or success state). Our goal is then either minimizing or maximizing the value until escape, depending on the application.

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