1,344 research outputs found
Bryophytes of Mona Island Natural Reserve, Puerto Rico
This checklist provides in addition to a list of mosses and hepatics, a key to the species. We report 17 moss species of which 9 are new to Mona Island and 3 are new records for Puerto Rico (Fissidens minutus, Plaubelia sprengelii and Brymela callicostelloides). This report represents a 35% increase to the moss flora of Mona Island. Thirteen hepatics are reported of which 8 are new records, representing an increase of 31%. Two new synonyms (Bryum microdecurrens = Bryum coronatum, Riccia brittonii = Riccia elliottii) are included. No hornworts are known for the island.Este listado en adición a la lista de musgos y hepáticas provee una clave para las especies. Reportamos 17 especies de musgos de los cuales 9 son nuevos para Isla de Mona y 3 son registros nuevos para Puerto Rico (Fissidens minutus, Plaubelia sprengelii y Brymela callicostelloides). Este reporte representa un aumento de un 35% en la flora muscinal de Isla de Mona. Trece hepáticas son reportadas de las cuales 8 son registros nuevos, representando un aumento de 31%. Dos nuevos sinónimos (Bryum microdecurrens = Bryum coronatum, Riccia brittonii = Riccia elliottii) se incluyen. No se conocen registros de antocerotes para la isla
Bounds on quark mass matrices elements due to measured properties of the mixing matrix and present values of the quark masses
We obtain constraints on possible structures of mass matrices in the quark
sector by using as experimental restrictions the determined values of the quark
masses at the energy scale, the magnitudes of the quark mixing matrix
elements , , , and , and the
Jarlskog invariant . Different cases of specific mass matrices are
examined in detail. The quality of the fits for the Fritzsch and Stech type
mass matrices is about the same with and
, respectively. The fit for a simple
generalization (one extra parameter) of the Fritzsch type matrices, in the
physical basis, is much better with . For
comparison we also include the results using the quark masses at the 2 GeV
energy scale. The fits obtained at this energy scale are similar to that at
energy scale, implying that our results are unaffected by the evolution
of the quark masses from 2 to 91 GeV.Comment: Evolution effects include
Intracontinental Neotectonics: Case Studies from the Tian Shan Orogen and Kuqa Fold-Thrust Belt
This dissertation focuses on the kinematic properties of intracontinental deformation during short geologic time scales. Using three case studies this work characterizes active deformation at varying spatial scales within the continental interior of Eurasia. The far-field effect of the Cenozoic Indo-Asia collision is the driving force controlling deformation within the Eurasian continental interior. Active deformation across the intracontinental Tian Shan range challenges the plate tectonic model that proposes crustal deformation is concentrated along plate boundaries. This work further constrains the active kinematics of intracontinental motion that is necessary to understand the dynamics of the Eurasian intracontinental system. The two standing hypothesis that explain intracontinental deformation include the (A) discrete or (B) diffuse deformation models. While the discrete model suggests deformation occurs primarily along major faults between crustal blocks, the diffuse model suggests motion is distributed throughout the continental interior. On a smaller scale, I examine active deformation of sub-aerial salt bodies. Ephemeral subaerial salt exposure during the evolution of a salt structure can greatly impact the subsequent development and deformation of its tectonic setting. InSAR time series analysis and inspection of individual interferograms confirm that the majority of the salt bodies in western Kuqa are active, with significant InSAR observable displacements at 3 of 4 structures studied in the region. Decoupling between surface salt motion and climatic conditions suggests that the regional tectonic regime controls surface salt displacement rates. Lastly, on a more local scale, this work examines the characteristics of anthropogenic deformation. Unnatural, rapid rates of subsidence and/or uplift have extreme hazard potential because it may lead to infrastructure damage and increased flood potential. Surface subsidence resulting from hydrocarbon extraction has been widely observed across the globe. However, the occurrence of surface uplift caused by fluid injection has only recently been noted and is less documented. An unusual surface displacement distribution at the Dawanqi oil field in the Kuqa fold-thrust belt of northwestern China suggests that fluid extraction may not only cause widespread, irreversible subsidence but also facilitate local uplift
Vitamin D Clinical Relevance in the Recovery From Traumatic Brain Injury Among the Military Population
Background: Traumatic brain injury (TBI) still remains a difficult disorder to treat. TBI has been associated to chronic neuroinflammation and a high risk for neurodegenerative disorders. Since 2001 between ten to twenty percent of all deployed military members have suffered a combat-related TBI. Nearly twenty to thirty percent of those will experience chronic cognitive, behavioral and somatic symptoms after suffering a TBI. Methods: The objective of this review is to evaluate current literature examining vitamin D as a neurosteroid with protective properties and its clinical relevance after traumatic brain injury. Vitamin D is known to participate in neurobiological processes and genomic regulation in the brain. Clinical and laboratory findings support that vitamin D modulates the immune responses to trauma, diminishes oxidative and toxic damage, and inhibiting activation and progression of the neuroinflammation. Inadequate levels of vitamin D have been identified as a common risk factor for many neurological disorders and have been linked to poorer recovery. Results: This review found compelling evidence to support that the pathology of TBI is closely associated with neuroprotective mechanisms of vitamin D. Low vitamin D levels are common among US active duty military and veterans. The findings strongly suggest that optimizing vitamin D prior to injury could improve the recovery for military members after experiencing a TBI. Vitamin D ameliorates brain damage by modulating neuroinflammation, improving cell survival and down-regulating mechanisms involved in the progression of cell damage following a TBI. However, further studies are needed to evaluate the effects of vitamin D optimization in TBI outcomes
Stochastic Invariants for Probabilistic Termination
Termination is one of the basic liveness properties, and we study the
termination problem for probabilistic programs with real-valued variables.
Previous works focused on the qualitative problem that asks whether an input
program terminates with probability~1 (almost-sure termination). A powerful
approach for this qualitative problem is the notion of ranking supermartingales
with respect to a given set of invariants. The quantitative problem
(probabilistic termination) asks for bounds on the termination probability. A
fundamental and conceptual drawback of the existing approaches to address
probabilistic termination is that even though the supermartingales consider the
probabilistic behavior of the programs, the invariants are obtained completely
ignoring the probabilistic aspect.
In this work we address the probabilistic termination problem for
linear-arithmetic probabilistic programs with nondeterminism. We define the
notion of {\em stochastic invariants}, which are constraints along with a
probability bound that the constraints hold. We introduce a concept of {\em
repulsing supermartingales}. First, we show that repulsing supermartingales can
be used to obtain bounds on the probability of the stochastic invariants.
Second, we show the effectiveness of repulsing supermartingales in the
following three ways: (1)~With a combination of ranking and repulsing
supermartingales we can compute lower bounds on the probability of termination;
(2)~repulsing supermartingales provide witnesses for refutation of almost-sure
termination; and (3)~with a combination of ranking and repulsing
supermartingales we can establish persistence properties of probabilistic
programs.
We also present results on related computational problems and an experimental
evaluation of our approach on academic examples.Comment: Full version of a paper published at POPL 2017. 20 page
A priori mixing of mesons and the |Delta I|=1/2 rule in K\to\pi\pi
We consider the hypothesis of a priori mixings in the mass eigenstates of
mesons to obtain the |Delta I|=1/2 rule in K\to\pi\pi. The Hamiltonian
responsible for the transition is the strong interacting one. The experimental
data are described using the isospin symmetry relations between the strong
coupling constants
Leveraging Thousands of Contrail Observations from GLOBE Citizen Scientists
The GLOBE (Global Learning and Observations to Benefit the Environment) Program is NASA's largest and longest-operating citizen science program contributing Earth observations. Over 800,000 cloud observations have been reported worldwide since YEAR that include reports of short-lived, persistent, and persistent-spreading contrails. While contrails can be challenging to observe with space-borne platforms, humans are adept at spotting contrails from the ground. The NASA GLOBE Clouds team at NASA Langley Research Center in Hampton, Virginia matches cloud observations to multiple satellite platforms for comparison, including: NASA's CERES (Clouds and Earth's Radiant Energy System) instrument onboard Terra and Aqua, CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation), and geostationary satellites. A pilot project was started with select students in the United States to track airplanes above 25,000 ft and report airplane type, altitude, and report if a contrail was being or was not being produced. The objective of the pilot project was to establish if this is a scalable approach for building an international observational dataset documenting what types of airplanes are creating what types of contrails (short-lived, persistent, spreading) under what atmospheric conditions. Preliminary results of this pilot project will be presented
Strike Hazard Posed By Columbids To Military Aircraft
Wildlife-aircraft strikes threaten both human and animal safety and result in hundreds of millions of dollars per year in aircraft damage and lost flight hours. Large-bodied birds are especially hazardous to aircraft. However, given high-speed flight at low altitudes, military aircraft may be especially vulnerable to strikes and more susceptible to damage even when encountering small birds. We summarized all wildlife-aircraft strike records from Randolph Air Force Base (San Antonio, Texas) over a 25-year period and compared the number and cost of strikes across avian species and species groups. Because columbids (i.e., pigeons and doves) are among the most frequently struck species by both civilian and military aircraft and because several columbid species have demonstrated marked population increases over the past decade, we also quantified characteristics (i.e., month, time of day, precipitation patterns, phase of flight, altitude) of columbid strikes. White-winged doves (Zenaida asiatica) have undergone a substantial northward range expansion over the past 60 years and are now numerous in San Antonio. Given local interest, we also highlighted characteristics of aircraft strikes involving this species. Though columbids were not the most frequently struck species group during the survey period (1990–2014), they were the most costly. Columbid strikes were more frequent from May to July than during other months and often occurred during morning hours, especially from 08:00–10:00, with a smaller afternoon peak from 15:00–17:00. Columbid strikes occurred during landing more than during other phases of flight, typically at ≤152 m above ground level (AGL), though white-winged doves were more likely to be struck on takeoff than expected. To reduce costs and safety concerns where columbids are prevalent, military flight planners, aircrews, and wildlife managers can reduce air travel, increase vigilance during takeoffs and landings, and implement on-the-ground hazing techniques in morning and late afternoon hours during spring and summer months
Spectroscopic Characteristics of Carbon Dots (C-Dots) Derived from Carbon Fibers and Conversion to Sulfur-Bridged C-Dots Nanosheets
We synthesized sub‐10 nm carbon nanoparticles (CNPs) consistent with photoluminescent carbon dots (C-dots) from carbon fiber starting material. The production of different C-dots fractions was monitored over seven days. During the course of the reaction, one fraction of C-dots species with relatively high photoluminescence was short-lived, emerging during the first hour of reaction but disappearing after one day of reaction. Isolation of this species during the first hour of the reaction was crucial to obtaining higher-luminescent C-dots species. When the reaction proceeded for one week, the appearance of larger nanostructures was observed over time, with lateral dimensions approaching 200 nm. The experimental evidence suggests that these larger species are formed from small C-dot nanoparticles bridged together by sulfur-based moieties between the C-dot edge groups, as if the C-dots polymerized by cross-linking the edge groups through sulfur bridges. Their size can be tailored by controlling the reaction time. Our results highlight the variety of CNP products, from sub‐10 nm C-dots to ~200 nm sulfur-containing carbon nanostructures, that can be produced over time during the oxidation reaction of the graphenic starting material. Our work provides a clear understanding of when to stop the oxidation reaction during the top-down production of C-dots to obtain highly photoluminescent species or a target average particle size
Complexity of Bradley-Manna-Sipma Lexicographic Ranking Functions
In this paper we turn the spotlight on a class of lexicographic ranking
functions introduced by Bradley, Manna and Sipma in a seminal CAV 2005 paper,
and establish for the first time the complexity of some problems involving the
inference of such functions for linear-constraint loops (without precondition).
We show that finding such a function, if one exists, can be done in polynomial
time in a way which is sound and complete when the variables range over the
rationals (or reals). We show that when variables range over the integers, the
problem is harder -- deciding the existence of a ranking function is
coNP-complete. Next, we study the problem of minimizing the number of
components in the ranking function (a.k.a. the dimension). This number is
interesting in contexts like computing iteration bounds and loop
parallelization. Surprisingly, and unlike the situation for some other classes
of lexicographic ranking functions, we find that even deciding whether a
two-component ranking function exists is harder than the unrestricted problem:
NP-complete over the rationals and -complete over the integers.Comment: Technical report for a corresponding CAV'15 pape
- …