1,683 research outputs found
A question by Chihara about shell polynomials and indeterminate moment problems
The generalized Stieltjes--Wigert polynomials depending on parameters 0\le
p<1 and 0<q<1 are discussed. By removing the mass at zero of the N-extremal
solution concentrated in the zeros of the D-function from the Nevanlinna
parametrization, we obtain a discrete measure \mu^M which is uniquely
determined by its moments. We calculate the coefficients of the corresponding
orthonormal polynomials (P^M_n). As noticed by Chihara, these polynomials are
the shell polynomials corresponding to the maximal parameter sequence for a
certain chain sequence. We also find the minimal parameter sequence, as well as
the parameter sequence corresponding to the generalized Stieltjes--Wigert
polynomials, and compute the value of related continued fractions. The mass
points of \mu^M have been studied in recent papers of Hayman, Ismail--Zhang and
Huber. In the special case of p=q, the maximal parameter sequence is constant
and the determination of \mu^M and (P^M_n) gives an answer to a question posed
by Chihara in 200
A low energy neutrino factory with non-magnetic detectors
We show that a very precise neutrino/anti-neutrino event separation is not
mandatory to cover the physics program of a low energy neutrino factory and
thus non-magnetized detectors like water Cerenkov or liquid Argon detectors can
be used. We point out, that oscillation itself strongly enhances the signal to
noise ratio of a wrong sign muon search, provided there is sufficiently
accurate neutrino energy reconstruction. Further, we argue that apart from a
magnetic field, other means to distinguish neutrino from anti-neutrino events
(at least statistically) can be explored. Combined with the fact that
non-magnetic detectors potentially can be made very big, we show that modest
neutrino/anti-neutrino separations at the level of 50% to 90% are sufficient to
obtain good sensitivity to CP violation and the neutrino mass hierarchy for
. These non-magnetized detectors have a rich
physics program outside the context of a neutrino factory, including topics
like supernova neutrinos and proton decay. Hence, our observation opens the
possibility to use a multi-purpose detector also in a neutrino factory beam.Comment: 13 pages, 4 figures, discussion improved, new figure 4, version to
appear in PL
Kinematics of the swimming of Spiroplasma
\emph{Spiroplasma} swimming is studied with a simple model based on
resistive-force theory. Specifically, we consider a bacterium shaped in the
form of a helix that propagates traveling-wave distortions which flip the
handedness of the helical cell body. We treat cell length, pitch angle, kink
velocity, and distance between kinks as parameters and calculate the swimming
velocity that arises due to the distortions. We find that, for a fixed pitch
angle, scaling collapses the swimming velocity (and the swimming efficiency) to
a universal curve that depends only on the ratio of the distance between kinks
to the cell length. Simultaneously optimizing the swimming efficiency with
respect to inter-kink length and pitch angle, we find that the optimal pitch
angle is 35.5 and the optimal inter-kink length ratio is 0.338, values
in good agreement with experimental observations.Comment: 4 pages, 5 figure
Goodness-of-fit Tests For Elliptical And Independent Copulas Through Projection Pursuit
Two goodness-of-fit tests for copulas are being investigated. The first one
deals with the case of elliptical copulas and the second one deals with
independent copulas. These tests result from the expansion of the projection
pursuit methodology we will introduce in the present article. This method
enables us to determine on which axis system these copulas lie as well as the
exact value of these very copulas in the basis formed by the axes previously
determined irrespective of their value in their canonical basis. Simulations
are also presented as well as an application to real datasets.Comment: 31 page
Eocene biogenic silica accumulation rates at the Pacific equatorial divergence zone
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94733/1/palo1454.pd
The political economy of unemployment insurance based on individual savings account: lessons from Chile
In recent years, unemployment protection systems based on individual savings have been instituted in several developing countries. Chile was one of the first to establish such a system, which at the time was widely cited as a model for other countries. This article discusses the particular political context in which the Chilean system was created before examining how it works in terms of coverage and levels of benefits received by unemployed workers. The authors undertake a detailed analysis of the administrative data produced by the system and conclude that the insurance covers only a small proportion of the unemployed, as most workers generally had precarious jobs that did not allow them to contribute to the system consistently. The Chilean case illustrates how difficult it is to establish functioning unemployment insurance in developing countries with precarious labour markets. Based on the interaction between employment characteristics and the conditions imposed by the benefit system, the article assesses the efficacy of the Unemployment Insurance Savings Accounts (UISA) system and analyses whether it can indeed serve as a model for other developing countries
Submarine neutrino communication
We discuss the possibility to use a high energy neutrino beam from a muon
storage ring to provide one way communication with a submerged submarine.
Neutrino interactions produce muons which can be detected either, directly when
they pass through the submarine or by their emission of Cerenkov light in sea
water, which, in turn, can be exploited with sensitive photo detectors. Due to
the very high neutrino flux from a muon storage ring, it is sufficient to mount
either detection system directly onto the hull of the submersible. The
achievable data transfer rates compare favorable with existing technologies and
do allow for a communication at the usual speed and depth of submarines.Comment: 4 pages, 1 figure, 1 table, published versio
Functional compartmentalization and metabolic separation in a prokaryotic cell
The prokaryotic cell is traditionally seen as a “bag of enzymes,” yet its organization is much more complex than in this simplified view. By now, various microcompartments encapsulating metabolic enzymes or pathways are known for Bacteria. These microcompartments are usually small, encapsulating and concentrating only a few enzymes, thus protecting the cell from toxic intermediates or preventing unwanted side reactions. The hyperthermophilic, strictly anaerobic Crenarchaeon Ignicoccus hospitalis is an extraordinary organism possessing two membranes, an inner and an energized outer membrane. The outer membrane (termed here outer cytoplasmic membrane) harbors enzymes involved in proton gradient generation and ATP synthesis. These two membranes are separated by an intermembrane compartment, whose function is unknown. Major information processes like DNA replication, RNA synthesis, and protein biosynthesis are located inside the “cytoplasm” or central cytoplasmic compartment. Here, we show by immunogold labeling of ultrathin sections that enzymes involved in autotrophic CO2 assimilation are located in the intermembrane compartment that we name (now) a peripheric cytoplasmic compartment. This separation may protect DNA and RNA from reactive aldehydes arising in the I. hospitalis carbon metabolism. This compartmentalization of metabolic pathways and information processes is unprecedented in the prokaryotic world, representing a unique example of spatiofunctional compartmentalization in the second domain of life
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