3,241 research outputs found
Quantile Correlations: Uncovering temporal dependencies in financial time series
We conduct an empirical study using the quantile-based correlation function
to uncover the temporal dependencies in financial time series. The study uses
intraday data for the S\&P 500 stocks from the New York Stock Exchange. After
establishing an empirical overview we compare the quantile-based correlation
function to stochastic processes from the GARCH family and find striking
differences. This motivates us to propose the quantile-based correlation
function as a powerful tool to assess the agreements between stochastic
processes and empirical data
Precision and Sensitivity in Detailed-Balance Reaction Networks
We study two specific measures of quality of chemical reaction networks,
Precision and Sensitivity. The two measures arise in the study of sensory
adaptation, in which the reaction network is viewed as an input-output system.
Given a step change in input, Sensitivity is a measure of the magnitude of the
response, while Precision is a measure of the degree to which the system
returns to its original output for large time. High values of both are
necessary for high-quality adaptation.
We focus on reaction networks without dissipation, which we interpret as
detailed-balance, mass-action networks. We give various upper and lower bounds
on the optimal values of Sensitivity and Precision, characterized in terms of
the stoichiometry, by using a combination of ideas from matroid theory and
differential-equation theory.
Among other results, we show that this class of non-dissipative systems
contains networks with arbitrarily high values of both Sensitivity and
Precision. This good performance does come at a cost, however, since certain
ratios of concentrations need to be large, the network has to be extensive, or
the network should show strongly different time scales
Meningkatkan Hasil Belajar Siswa Pada Pembelajaran IPS Dengan Menggunakan Media Gambar Kelas V SDN Osan
Permasalahan dalam penelitian ini adalah rendahnya hasil belajar siswa pada mata pelajaran IPS di Kelas V SDN Osan. Penelitian ini bertujuan untuk meningkatkan hasil belajar siswa pada pembelajaran IPS dengan menggunakan media gambar.Jenis Penelitian ini adalah penelitian tindakan kelas (PTK). Subjek penelitian ini adalah siswa kelas V SDN Osan sebanyak 25 orang, yang terdiri dari 10 laki-laki dan 15 orang siswa perempuan.Teknik pengumpulan data dilakukan melalui dua cara yaitu:Tes tertulis dan Observasi. Teknik analisis data yang digunakan adalah analisis data kualitatif yang dilakukan melalui tiga tahap, yaitu reduksi data, penyajian data dan verifikasi/penarikan kesimpulan.Hasil penelitian menunjukkan bahwa pada siklus I diperoleh Daya Serap Individu (DSI) sebesar 64,88% dan Tuntas Klasikal (TK) sebesar 44% dan nilai rata-rata sebesar 64,88% dan pada siklus II menunjukkan Daya Serap Individu (DSI) sebesar 71,84% dan Tuntas Klasikal (TK) sebesar 80% dan nilai rata-rata (NR) 71,84%. Adapun hasil observasi aktivitas guru dan siswa mengalami peningkatan dari siklus I ke siklus II mencapai kategori yang sangat baik.Berdasarkan hasil penelitian tersebut, dapat disimpulkan bahwa penggunaan media gambar dalam pembelajaran IPS dapat meningkatkan hasil belajar siswa kelas V SDN Osan
Osmotic properties of polyethyleneglycols: quantitative features of brush and bulk scaling laws
From glycosylated cell surfaces to sterically stabilized liposomes, polymers
attached to membranes attract biological and therapeutic interest. Can the
scaling laws of polymer "brushes" describe the physical properties of these
coats? We delineate conditions where the Alexander - de Gennes theory of
polymer brushes successfully describes the intermembrane distance vs. applied
osmotic stress data of Kenworthy et al. for PEG-grafted multilamellar liposomes
[Biophys. J. (1995) 68:1921]. We establish that the polymer density and size in
the brush must be high enough that, in a bulk solution of equivalent density,
the polymer osmotic pressure is independent of polymer molecular weight (the
des Cloizeaux semi-dilute regime of bulk polymer solutions). The condition that
attached polymers behave as semi-dilute bulk solutions offers a rigorous
criterion for brush scaling-law behavior. There is a deep connection between
the behaviors of polymer solutions in bulk and polymers grafted to a surface at
a density such that neighbors pack to form a uniform brush. In this regime,
two-parameter unconstrained fits of the Alexander - de Gennes brush scaling
laws yield effective monomer lengths of 3.3 to 3.5 AA, which agree with
structural predictions. The fitted distances between grafting sites are larger
than expected from the nominal content of PEG-lipids; the chains apparently
saturate the surface. Osmotic stress measurements can be used to estimate the
actual densities of membrane-grafted polymers.Comment: 26 pages with figure
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