1,909 research outputs found
Dynamical behavior of generic quintessence potentials: constraints on key dark energy observables
We perform a comprehensive study of a class of dark energy models - scalar
field models where the effective potential can be described by a polynomial
series - exploring their dynamical behavior using the method of flow equations
that has previously been applied to inflationary models. Using supernova,
baryon oscillation, CMB and Hubble constant data, and an implicit theoretical
prior imposed by the scalar field dynamics, we find that the LCDM model
provides an excellent fit to the data. Constraints on the generic scalar field
potential parameters are presented, along with the reconstructed w(z) histories
consistent with the data and the theoretical prior. We propose and pursue
computationally feasible algorithms to obtain estimates of the principal
components of the equation of state, as well as parameters w_0 and w_a.
Further, we use the Monte Carlo Markov Chain machinery to simulate future data
based on the Joint Dark Energy Mission, Planck and baryon acoustic oscillation
surveys and find that the inverse area figure of merit improves nearly by an
order of magnitude. Therefore, most scalar field models that are currently
consistent with data can be potentially ruled out by future experiments. We
also comment on the classification of dark energy models into "thawing'" and
"freezing" in light of the more diverse evolution histories allowed by this
general class of potentials.Comment: 22 pages and 12 figures, minor clarifications and a new Figure (#9)
added in v3, matches the published PRD version. Chains and high-res figures
are available at
http://kicp.uchicago.edu/~dhuterer/DE_FLOWROLL/de_flowroll.htm
Spin-SILC: CMB polarisation component separation with spin wavelets
We present Spin-SILC, a new foreground component separation method that
accurately extracts the cosmic microwave background (CMB) polarisation and
modes from raw multifrequency Stokes and measurements of the
microwave sky. Spin-SILC is an internal linear combination method that uses
spin wavelets to analyse the spin-2 polarisation signal . The
wavelets are additionally directional (non-axisymmetric). This allows different
morphologies of signals to be separated and therefore the cleaning algorithm is
localised using an additional domain of information. The advantage of spin
wavelets over standard scalar wavelets is to simultaneously and
self-consistently probe scales and directions in the polarisation signal and in the underlying and modes, therefore providing the ability
to perform component separation and - decomposition concurrently for the
first time. We test Spin-SILC on full-mission Planck simulations and data and
show the capacity to correctly recover the underlying cosmological and
modes. We also demonstrate a strong consistency of our CMB maps with those
derived from existing component separation methods. Spin-SILC can be combined
with the pseudo- and pure - spin wavelet estimators presented in a
companion paper to reliably extract the cosmological signal in the presence of
complicated sky cuts and noise. Therefore, it will provide a
computationally-efficient method to accurately extract the CMB and
modes for future polarisation experiments.Comment: 13 pages, 9 figures. Minor changes to match version published in
MNRAS. Map products available at http://www.silc-cmb.org. Companion paper:
arXiv:1605.01414 "Wavelet reconstruction of pure E and B modes for CMB
polarisation and cosmic shear analyses" (B. Leistedt et al.
SILC: a new Planck Internal Linear Combination CMB temperature map using directional wavelets
We present new clean maps of the CMB temperature anisotropies (as measured by
Planck) constructed with a novel internal linear combination (ILC) algorithm
using directional, scale-discretised wavelets --- Scale-discretised,
directional wavelet ILC or SILC. Directional wavelets, when convolved with
signals on the sphere, can separate the anisotropic filamentary structures
which are characteristic of both the CMB and foregrounds. Extending previous
component separation methods, which use the frequency, spatial and harmonic
signatures of foregrounds to separate them from the cosmological background
signal, SILC can additionally use morphological information in the foregrounds
and CMB to better localise the cleaning algorithm. We test the method on Planck
data and simulations, demonstrating consistency with existing component
separation algorithms, and discuss how to optimise the use of morphological
information by varying the number of directional wavelets as a function of
spatial scale. We find that combining the use of directional and axisymmetric
wavelets depending on scale could yield higher quality CMB temperature maps.
Our results set the stage for the application of SILC to polarisation
anisotropies through an extension to spin wavelets.Comment: 15 pages, 13 figures. Minor changes to match version published in
MNRAS. Map products available at http://www.silc-cmb.or
Public Opinion on Peace as a Reflection of Social Differentiation and Politicisation of Identity in Sri Lanka
This article provides a critical analysis of the public opinion on peace in Sri Lanka, with consideration to two determinants: social differentiation and politicisation of identities. Specifically, it aims at developing arguments about the correlations between public opinion, social position, and political mobilisation. Inspired by Bourdieu\u27s concepts of habitus, social space, and political field, this article develops an empirical analysis of the links between ethnic identity and public opinion on peace, and between social differentiation and opinions within the Sinhalese majority community in Sri Lanka. This article argues that ethnic polarisation and politicisation were the foremost determinants of public opinion during the peace process in 2002-2009
An Emulator for the Lyman-alpha Forest
We present methods for interpolating between the 1-D flux power spectrum of
the Lyman- forest, as output by cosmological hydrodynamic simulations.
Interpolation is necessary for cosmological parameter estimation due to the
limited number of simulations possible. We construct an emulator for the
Lyman- forest flux power spectrum from small simulations using
Latin hypercube sampling and Gaussian process interpolation. We show that this
emulator has a typical accuracy of 1.5% and a worst-case accuracy of 4%, which
compares well to the current statistical error of 3 - 5% at from BOSS
DR9. We compare to the previous state of the art, quadratic polynomial
interpolation. The Latin hypercube samples the entire volume of parameter
space, while quadratic polynomial emulation samples only lower-dimensional
subspaces. The Gaussian process provides an estimate of the emulation error and
we show using test simulations that this estimate is reasonable. We construct a
likelihood function and use it to show that the posterior constraints generated
using the emulator are unbiased. We show that our Gaussian process emulator has
lower emulation error than quadratic polynomial interpolation and thus produces
tighter posterior confidence intervals, which will be essential for future
Lyman- surveys such as DESI.Comment: 28 pages, 10 figures, accepted to JCAP with minor change
Correlations in the three-dimensional Lyman-alpha forest contaminated by high column density absorbers
Correlations measured in three dimensions in the Lyman-alpha forest are
contaminated by the presence of the damping wings of high column density (HCD)
absorbing systems of neutral hydrogen (HI; having column densities
), which
extend significantly beyond the redshift-space location of the absorber. We
measure this effect as a function of the column density of the HCD absorbers
and redshift by measuring 3D flux power spectra in cosmological hydrodynamical
simulations from the Illustris project. Survey pipelines exclude regions
containing the largest damping wings. We find that, even after this procedure,
there is a scale-dependent correction to the 3D Lyman-alpha forest flux power
spectrum from residual contamination. We model this residual using a simple
physical model of the HCD absorbers as linearly biased tracers of the matter
density distribution, convolved with their Voigt profiles and integrated over
the column density distribution function. We recommend the use of this model
over existing models used in data analysis, which approximate the damping wings
as top-hats and so miss shape information in the extended wings. The simple
'linear Voigt model' is statistically consistent with our simulation results
for a mock residual contamination up to small scales (). It does not account for the effect of the highest
column density absorbers on the smallest scales (e.g., for small damped Lyman-alpha absorbers; HCD
absorbers with ). However, these systems are in any
case preferentially removed from survey data. Our model is appropriate for an
accurate analysis of the baryon acoustic oscillations feature. It is
additionally essential for reconstructing the full shape of the 3D flux power
spectrum.Comment: 13 pages, 11 figures. Minor changes to match version published in
MNRA
Non-destructive Detection of Food Adulteration to Guarantee Human Health and Safety
The primary objective of this review is to critique the basic concepts of non-destructive detection of food adulteration and fraud which collectively represent a tremendous annual financial loss worldwide and a major cause of human disease. The review covers the principles of the analytical instrumentation used for the non-destructive detection of food adulteration. Examples of practical applications of these methods for the control of food adulteration are provided and a comparative analysis of the advantages and disadvantages of instrumental methods in food technology are critiqued.Целью данного обзора является критическое рассмотрение основных понятий неразрушающего выявления фальсификации и подделки продуктов питания, которые в целом вызывают огромные ежегодные финансовые убытки во всем мире и являются одной из основных причин заболеваний человечества. Материалы и методы. Литература, указанная в данном обзоре, была получена в результате поиска библиографической информации в CAB abstracts, AGRICOLA, SciFinder Scholar, Modern Language Association (MLA), American Psychological Association (APA), OECD / EEA database по инструментам, которые используются для экологической политики и управления природными ресурсами, и Web of Science.Результаты и обсуждение. Фальсификация пищевых продуктов означает преднамеренное, обманное добавление посторонних, нестандартных или дешевых ингредиентов в продукты, или разбавление или удаление некоторых ценных ингредиентов с целью увеличения прибыли. В современных условиях производители стремятся увеличить выпуск своей продукции зачастую путем изготовления и продажи некачественных и фальсифицированных продуктов.“Неразрушающее выявление фальсификации пищевых продуктов” означает анализ образца и его существенных признаков без изменения физических и химических свойств образца. Повышение качества и безопасности пищевых продуктов путем разработки научных методов обнаружения фальсификации является главным условием для поддержания здоровья потребителей. Точная объективная оценка качества и выявление фальсификации пищевых продуктов представляется важнейшей целью пищевой промышленности. В связи с совершенствованием технологии фальсификации продуктов важно быть в курсе современных, самых точных методов контроля их фальсификации. С этой целью данный обзор рассматривает основные понятия выявления фальсификации продуктов питания, принципы устройств и возможные практические применения современных методов неразрушающего выявления фальсификации продуктов питания; сравнительный анализ преимуществ и недостатков инструментальных методов, используемых в пищевых технологиях. Каждый из рассмотренных методов обсуждается с точки зрения возможных различных консистенций продуктов – газов (свободного пространства вокруг продукта), свободно текущих жидкостей (соков), мутных и вязких жидкостей (меда как продукта растительного происхождения, растительных масел) и интактных продуктов (фруктов и овощей).Выводы. Результаты, освещенные в обзоре, рекомендуется использовать при контроле качества и безопасности пищевых продуктов.Метою даного огляду є критичний розгляд основних понять неруйнівного виявлення фальсифікації і підробки продуктів харчування, які в цілому викликають величезні щорічні фінансові збитки у всьому світі і є однією з основних причин захворювань людства.
Матеріали і методи. Література, зазначена в даному огляді, була отримана в результаті пошуку бібліографічної інформації в in CAB abstracts, AGRICOLA, SciFinder Scholar, Modern Language Association (MLA), American Psychological Association (APA), OECD/EEA database щодо інструментів, які використовуються для екологічної політики та управління природними ресурсами, та Web of Science. Результати та обговорення. Фальсифікація харчових продуктів означає умисне, облудне додавання сторонніх, нестандартних або дешевих інгредієнтів в продукти, або розбавлення чи видалення деяких цінних інгредієнтів з метою збільшення прибутків. У сучасних умовах виробники прагнуть збільшити випуск своєї продукції найчастіше шляхом виготовлення та продажу неякісних та фальсифікованих продуктів. “Неруйнівне виявлення фальсифікації харчових продуктів” означає аналіз зразка і його істотних ознак без зміни фізичних і хімічних властивостей зразка.
Підвищення якості та безпеки харчових продуктів шляхом розробки наукових методів виявлення фальсифікації є головною умовою для підтримки здоров’я споживачів. Точна об’єктивна оцінка якості і виявлення фальсифікації харчових продуктів представляється найважливішою метою харчової промисловості. У зв’язку з удосконаленням технології фальсифікації продуктів важливо бути в курсі сучасних, найбільш точних методів контролю їх фальсифікації. З цією метою даний огляд розглядає основні поняття виявлення фальсифікації продуктів харчування, принципи пристроїв і можливі практичні застосування сучасних методів неруйнівного виявлення фальсифікації продуктів харчування; порівняльний аналіз переваг і недоліків інструментальних методів, що застосовуються в харчових технологіях. Кожен з розглянутих методів обговорюється з точки зору можливих різних консистенцій продуктів - газів (вільного простору навколо продукту), вільно текучих рідин (соків), каламутних та в'язких рідин (меду як продукту рослинного походження, рослинних масел) і інтактних продуктів (фруктів і овочів). Висновки. Результати, висвітлені в огляді, рекомендується використовувати під час контролю якості та безпеки харчових продуктів
Simulating the effect of high column density absorbers on the one-dimensional Lyman-alpha forest flux power spectrum
We measure the effect of high column density absorbing systems of neutral
hydrogen (HI) on the one-dimensional (1D) Lyman-alpha forest flux power
spectrum using cosmological hydrodynamical simulations from the Illustris
project. High column density absorbers (which we define to be those with HI
column densities ) cause broadened absorption lines
with characteristic damping wings. These damping wings bias the 1D Lyman-alpha
forest flux power spectrum by causing absorption in quasar spectra away from
the location of the absorber itself. We investigate the effect of high column
density absorbers on the Lyman-alpha forest using hydrodynamical simulations
for the first time. We provide templates as a function of column density and
redshift, allowing the flexibility to accurately model residual contamination,
i.e., if an analysis selectively clips out the largest damping wings. This
flexibility will improve cosmological parameter estimation, e.g., allowing more
accurate measurement of the shape of the power spectrum, with implications for
cosmological models containing massive neutrinos or a running of the spectral
index. We provide fitting functions to reproduce these results so that they can
be incorporated straightforwardly into a data analysis pipeline.Comment: 11 pages, 6 figures. Minor changes to match version published in
MNRA
Role of Newcomers Supportive Strategies on Socio-Technical Performance of Open Source Projects
The success of open source software (OSS) projects have been studied in previous research. This paper focused on the effect of newcomers’ supportive strategies in OSS projects on the success level of the projects. Our research analyzes the socio-technical commitment to the project as a proxy for success. Data about 453 OSS projects from GitHub.com is collected and analyzed to empirically test the research model. We have applied a clustering technique to explore the dataset attributes. Results show the importance of newcomers’ supportive strategies on the different socio-technical aspects of OSS projects’ leading to success. Also, we have tested the effect of programming language diversity and project profile health on the success of projects. The outcome of this study has both managerial and practical implications
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