2,393 research outputs found
A new perturbative approach to the adiabatic approximation
A new and intuitive perturbative approach to time-dependent quantum mechanics
problems is presented, which is useful in situations where the evolution of the
Hamiltonian is slow. The state of a system which starts in an instantaneous
eigenstate of the initial Hamiltonian is written as a power series which has a
straightforward diagrammatic representation. Each term of the series
corresponds to a sequence of "adiabatic" evolutions, during which the system
remains in an instantaneous eigenstate of the Hamiltonian, punctuated by
transitions from one state to another. The first term of this series is the
standard adiabatic evolution, the next is the well-known first correction to
it, and subsequent terms can be written down essentially by inspection.
Although the final result is perhaps not terribly surprising, it seems to be
not widely known, and the interpretation is new, as far as we know. Application
of the method to the adiabatic approximation is given, and some discussion of
the validity of this approximation is presented.Comment: 9 pages. Added references, discussion of previous results, expanded
upon discussion of main result and application of i
The accretion-diffusion scenario for metals in cool white dwarfs
We calculated diffusion timescales for Ca, Mg, Fe in hydrogen atmosphere
white dwarfs with temperatures between 5000 and 25000 K. With these timescales
we determined accretion rates for a sample of 38 DAZ white dwarfs from the
recent studies of Zuckerman et al. (2003) and Koester et al. (2005). Assuming
that the accretion rates can be calculated with the Bondi-Hoyle formula for
hydrodynamic accretion, we obtained estimates for the interstellar matter
density around the accreting objects. These densities are in good agreement
with new data about the warm, partially ionized phase of the ISM in the solar
neighborhood.Comment: To be published in A&
Differentially Private Linear Regression with Linked Data
There has been increasing demand for establishing privacy-preserving
methodologies for modern statistics and machine learning. Differential privacy,
a mathematical notion from computer science, is a rising tool offering robust
privacy guarantees. Recent work focuses primarily on developing differentially
private versions of individual statistical and machine learning tasks, with
nontrivial upstream pre-processing typically not incorporated. An important
example is when record linkage is done prior to downstream modeling. Record
linkage refers to the statistical task of linking two or more data sets of the
same group of entities without a unique identifier. This probabilistic
procedure brings additional uncertainty to the subsequent task. In this paper,
we present two differentially private algorithms for linear regression with
linked data. In particular, we propose a noisy gradient method and a sufficient
statistics perturbation approach for the estimation of regression coefficients.
We investigate the privacy-accuracy tradeoff by providing finite-sample error
bounds for the estimators, which allows us to understand the relative
contributions of linkage error, estimation error, and the cost of privacy. The
variances of the estimators are also discussed. We demonstrate the performance
of the proposed algorithms through simulations and an application to synthetic
data
7-Bromo-4b-methyl-7,8-dihydro-4bH-9-thia-8a-azafluorene 9,9-dioxide
The title compound, C12H12BrNO2S, was isolated after direct irradiation (hν 350 nm, hexane) of a mixture of stereoisomeric sulfonamides containing a vicinal dibromide and a conjugated diene. This product is one of a group of substrates that has contributed to our understanding of the photoreactivity patterns of non-bridged sulfonamides. The crystal structure was determined from a non-merohedrally twinned data set, where the twin law corresponded to a 180° rotation about the a* axis. The minor twin component refined to a value of 0.176 (3). The conformation of the molecule is planar at one end, as the benzene ring and the adjacent fused five-membered ring are coplanar, and U-shaped at the other end, where the five-membered ring is fused to the heterocyclic six-membered ring containing an allyl bromide group
The Influence Of Normalization Technique On Between-muscle Activation During A Back-squat: Methodological Considerations
Sustained expression of microRNA-155 in hematopoietic stem cells causes a myeloproliferative disorder
Mammalian microRNAs are emerging as key regulators of the development and function of the immune system. Here, we report a strong but transient induction of miR-155 in mouse bone marrow after injection of bacterial lipopolysaccharide (LPS) correlated with granulocyte/monocyte (GM) expansion. Demonstrating the sufficiency of miR-155 to drive GM expansion, enforced expression in mouse bone marrow cells caused GM proliferation in a manner reminiscent of LPS treatment. However, the miR-155–induced GM populations displayed pathological features characteristic of myeloid neoplasia. Of possible relevance to human disease, miR-155 was found to be overexpressed in the bone marrow of patients with certain subtypes of acute myeloid leukemia (AML). Furthermore, miR-155 repressed a subset of genes implicated in hematopoietic development and disease. These data implicate miR-155 as a contributor to physiological GM expansion during inflammation and to certain pathological features associated with AML, emphasizing the importance of proper miR-155 regulation in developing myeloid cells during times of inflammatory stress
Dual Fronts Propagating into an Unstable State
The interface between an unstable state and a stable state usually develops a
single confined front travelling with constant velocity into the unstable
state. Recently, the splitting of such an interface into {\em two} fronts
propagating with {\em different} velocities was observed numerically in a
magnetic system. The intermediate state is unstable and grows linearly in time.
We first establish rigorously the existence of this phenomenon, called ``dual
front,'' for a class of structurally unstable one-component models. Then we use
this insight to explain dual fronts for a generic two-component
reaction-diffusion system, and for the magnetic system.Comment: 19 pages, Postscript, A
New exact fronts for the nonlinear diffusion equation with quintic nonlinearities
We consider travelling wave solutions of the reaction diffusion equation with
quintic nonlinearities . If the parameters
and obey a special relation, then the criterion for the existence of a
strong heteroclinic connection can be expressed in terms of two of these
parameters. If an additional restriction is imposed, explicit front solutions
can be obtained. The approach used can be extended to polynomials whose highest
degree is odd.Comment: Revtex, 5 page
Comparative transcriptomic analysis of human placentae at term and preterm delivery.
Preterm birth affects 1 out of every 10 infants in the United States, resulting in substantial neonatal morbidity and mortality. Currently, there are few predictive markers and few treatment options to prevent preterm birth. A healthy, functioning placenta is essential to positive pregnancy outcomes. Previous studies have suggested that placental pathology may play a role in preterm birth etiology. Therefore, we tested the hypothesis that preterm placentae may exhibit unique transcriptomic signatures compared to term samples reflective of their abnormal biology leading to this adverse outcome. We aggregated publicly available placental villous microarray data to generate a preterm and term sample dataset (n = 133, 55 preterm placentae and 78 normal term placentae). We identified differentially expressed genes using the linear regression for microarray (LIMMA) package and identified perturbations in known biological networks using Differential Rank Conservation (DIRAC). We identified 129 significantly differentially expressed genes between term and preterm placenta with 96 genes upregulated and 33 genes downregulated (P-valu
Understanding An Interprofessional Team Through The Lens Of The Intentional Relationship Model (IRM)
Research poster describing the following process: The Intentional Relationship Model (IRM) is designed to explain the therapist\u27s roles and demands in both establishing and maintaining a therapeutic relationship with a patient. While based in occupational therapy, this model has wide implications on being applied in many contexts, including an interdisciplinary team. While based in occupational therapy, this model has wide implications for the application to health care interdisciplinary teams. The objective for our team was to analyze our own interactions with Alex and identify how our ability to use different modes of the IRM and mode-shift made an impact on our care both individually and as a collective.https://dune.une.edu/cecespring2020/1015/thumbnail.jp
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