597 research outputs found
Quasilinear stabilization of the free electron laser instability for a relativistic electron beam propagating through a transverse helical wiggler magnetic field
Residual Stresses in Cold Formed Steel Sections
Initial or residual stresses are considered one of the major factors that affect the design of the cold-formed steel sections, since they could reach 50% of the yield stress of the material. As part of a comprehensive experimental program on the use of cold-formed steel sections in transmission towers, an investigation on the magnitude and distribution of residual stresses in cold-formed steel sections was undertaken. The study involved 83 tests using two nondestructive methods, and two destructive methods, to determine the magnitude and distribution of residual stresses. The paper summarizes the results from this investigation and outlines a number of implications for the design of cold-formed sections
Active Depth Estimation: Stability Analysis and its Applications
Recovering the 3D structure of the surrounding environment is an essential
task in any vision-controlled Structure-from-Motion (SfM) scheme. This paper
focuses on the theoretical properties of the SfM, known as the incremental
active depth estimation. The term incremental stands for estimating the 3D
structure of the scene over a chronological sequence of image frames. Active
means that the camera actuation is such that it improves estimation
performance. Starting from a known depth estimation filter, this paper presents
the stability analysis of the filter in terms of the control inputs of the
camera. By analyzing the convergence of the estimator using the Lyapunov
theory, we relax the constraints on the projection of the 3D point in the image
plane when compared to previous results. Nonetheless, our method is capable of
dealing with the cameras' limited field-of-view constraints. The main results
are validated through experiments with simulated data.Comment: 7 pages, 3 figures, conferenc
Critical currents in Josephson junctions with macroscopic defects
The critical currents in Josephson junctions of conventional superconductors
with macroscopic defects are calculated for different defect critical current
densities as a function of the magnetic field. We also study the evolution of
the different modes with the defect position, at zero external field. We study
the stability of the solutions and derive simple arguments, that could help the
defect characterization. In most cases a reentrant behavior is seen, where both
a maximum and a minimum current exist.Comment: 17 pages with 16 figures, submitted to Supercond. Sci. Techno
Adverse events of active and placebo groups in SARS-CoV-2 vaccine randomized trials: A systematic review
Male and female sex hormones in primary headaches
Background: The three primary headaches, tension-type headache, migraine and cluster headache, occur in both genders, but all seem to have a sex-specific prevalence. These gender differences suggest that both male and female sex hormones could have an influence on the course of primary headaches. This review aims to summarise the most relevant and recent literature on this topic. Methods: Two independent reviewers searched PUBMED in a systematic manner. Search strings were composed using the terms LH, FSH, progesteron, estrogen, DHEA, prolactin, testosterone, androgen, headach, migrain, "tension type" or cluster. A timeframe was set limiting the search to articles published in the last 20 years, after January 1st 1997. Results: Migraine tends to follow a classic temporal pattern throughout a woman's life corresponding to the fluctuation of estrogen in the different reproductive stages. The estrogen withdrawal hypothesis forms the basis for most of the assumptions made on this behalf. The role of other hormones as well as the importance of sex hormones in other primary headaches is far less studied. Conclusion: The available literature mainly covers the role of sex hormones in migraine in women. Detailed studies especially in the elderly of both sexes and in cluster headache and tension-type headache are warranted to fully elucidate the role of these hormones in all primary headaches
Cnidarian Pattern Recognition Receptor Repertoires Reflect Both Phylogeny and Life History Traits
Pattern recognition receptors (PRRs) are evolutionarily ancient and crucial components of innate immunity, recognizing danger-associated molecular patterns (DAMPs) and activating host defenses. Basal non-bilaterian animals such as cnidarians must rely solely on innate immunity to defend themselves from pathogens. By investigating cnidarian PRR repertoires we can gain insight into the evolution of innate immunity in these basal animals. Here we utilize the increasing amount of available genomic resources within Cnidaria to survey the PRR repertoires and downstream immune pathway completeness within 15 cnidarian species spanning two major cnidarian clades, Anthozoa and Medusozoa. Overall, we find that anthozoans possess prototypical PRRs, while medusozoans appear to lack these immune proteins. Additionally, anthozoans consistently had higher numbers of PRRs across all four classes relative to medusozoans, a trend largely driven by expansions in NOD-like receptors and C-type lectins. Symbiotic, sessile, and colonial cnidarians also have expanded PRR repertoires relative to their non-symbiotic, mobile, and solitary counterparts. Interestingly, cnidarians seem to lack key components of mammalian innate immune pathways, though similar to PRR numbers, anthozoans possess more complete immune pathways than medusozoans. Together, our data indicate that anthozoans have greater immune specificity than medusozoans, which we hypothesize to be due to life history traits common within Anthozoa. Overall, this investigation reveals important insights into the evolution of innate immune proteins within these basal animals
Inter- and intragrain currents in bulk melt-grown YBaCuO rings
A simple contactless method suitable to discern between the intergrain
(circular) current, which flows in the thin superconducting ring, and the
intragrain current, which does not cross the weakest link, has been proposed.
At first, we show that the intergrain current may directly be estimated from
the magnetic flux density measured by the Hall sensor positioned
in the special points above/below the ring center. The experimental
and the numerical techniques to determine the value are discussed. Being
very promising for characterization of a current flowing across the joints in
welded YBaCuO rings (its dependencies on the temperature and the external
magnetic field as well as the time dissipation), the approach has been applied
to study corresponding properties of the intra- and intergrain currents flowing
across the -twisted grain boundaries which are frequent in bulk
melt-textured YBaCuO samples. We present experimental data related to the flux
penetration inside a bore of MT YBaCuO rings both in the non-magnetized, virgin
state and during the field reversal. The shielding properties and their
dependence on external magnetic fields are also studied. Besides, we consider
the flux creep effects and their influence on the current re-distribution
during a dwell.Comment: 13 pages, 16 figures (EPS), RevTeX4. In the revised version,
corrections to perturbing effects near the weak links are introduced, one
more figure is added. lin
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