519 research outputs found
Chirality of wave functions for three coalescing levels
The coalescence of three levels has particular attractive features. Even
though it may be difficult to realise such event in the laboratory (three
additional real parameters must be adjusted), to take up the challenge seems
worthwhile. In the same way as the chiral behaviour of a usual EP can give a
direction on a line, the state vectors in the vicinity of an EP3 provide an
orientation in the plane. The distinction between left and right handedness
depends on the distribution of the widths of the three levels in the vicinity
of the point of coalescence.Comment: Manuscript has been discussed in June 2007 with the experimental
group under Professor Achim Richter at the TU Darmstadt. It has been
presented at the 6th International Workshop on Pseudo Hermitian Hamiltonians,
London, 16-18 July 2007. An expanded version is being prepared for
publication. 3 Figures, 11 page
Cryptococcal transmigration across a model brain blood-barrier: Evidence of the Trojan horse mechanism and differences between Cryptococcus neoformans var. grubii strain H99 and Cryptococcus gattii strain R265
© 2015 Institut Pasteur. Cryptococcus neoformans (. Cn) and Cryptococcus gattii (Cg) cause neurological disease and cross the BBB as free cells or in mononuclear phagocytes via the Trojan horse mechanism, although evidence for the latter is indirect. There is emerging evidence that Cn and the North American outbreak Cg strain (R265) more commonly cause neurological and lung disease, respectively. We have employed a widely validated in vitro model of the BBB, which utilizes the hCMEC/D3 cell line derived from human brain endothelial cells (HBEC) and the human macrophage-like cell line, THP-1, to investigate whether transport of dual fluorescence-labelled Cn and Cg across the BBB occurs within macrophages. We showed that phagocytosis of Cn by non-interferon (IFN)-γ stimulated THP-1 cells was higher than that of Cg. Although Cn and Cg-loaded THP-1 bound similarly to TNF-activated HBECs under shear stress, more Cn-loaded macrophages were transported across an intact HBEC monolayer, consistent with the predilection of Cn for CNS infection. Furthermore, Cn exhibited a higher rate of expulsion from transmigrated THP-1 compared with Cg. Our results therefore provide further evidence for transmigration of both Cn and Cg via the Trojan horse mechanism and a potential explanation for the predilection of Cn to cause CNS infection
Complex WKB Analysis of a PT Symmetric Eigenvalue Problem
The spectra of a particular class of PT symmetric eigenvalue problems has
previously been studied, and found to have an extremely rich structure. In this
paper we present an explanation for these spectral properties in terms of
quantisation conditions obtained from the complex WKB method. In particular, we
consider the relation of the quantisation conditions to the reality and
positivity properties of the eigenvalues. The methods are also used to examine
further the pattern of eigenvalue degeneracies observed by Dorey et al. in
[1,2].Comment: 22 pages, 13 figures. Added references, minor revision
Interstellar polarization and grain alignment: the role of iron and silicon
We compiled the polarimetric data for a sample of lines of sight with known
abundances of Mg, Si, and Fe. We correlated the degree of interstellar
polarization and polarization efficiency (the ratio of to the colour
excess or extinction ) with dust phase abundances. We detect an
anticorrelation between and the dust phase abundance of iron in non
silicate - containing grains ]_\rm d, a correlation
between and the abundance of Si, and no correlation between or
and dust phase abundances. These findings can be explained if mainly
the silicate grains aligned by the radiative mechanism are responsible for the
observed interstellar linear polarization.Comment: Accepted for publication in Astronomy and Astrophysic
Early respiratory viral infections in infants with cystic fibrosis
This article is made available for unrestricted research re-use and secondary analysis in any form or by any means with acknowledgement of the original source. These permissions are granted for the duration of the World Health Organization (WHO) declaration of COVID-19 as a global pandemic.Background
Viral infections contribute to morbidity in cystic fibrosis (CF), but the impact of respiratory viruses on the development of airway disease is poorly understood.
Methods
Infants with CF identified by newborn screening were enrolled prior to 4 months of age to participate in a prospective observational study at 4 centers. Clinical data were collected at clinic visits and weekly phone calls. Multiplex PCR assays were performed on nasopharyngeal swabs to detect respiratory viruses during routine visits and when symptomatic. Participants underwent bronchoscopy with bronchoalveolar lavage (BAL) and a subset underwent pulmonary function testing. We present findings through 8.5 months of life.
Results
Seventy infants were enrolled, mean age 3.1 ± 0.8 months. Rhinovirus was the most prevalent virus (66%), followed by parainfluenza (19%), and coronavirus (16%). Participants had a median of 1.5 viral positive swabs (range 0–10). Past viral infection was associated with elevated neutrophil concentrations and bacterial isolates in BAL fluid, including recovery of classic CF bacterial pathogens. When antibiotics were prescribed for respiratory-related indications, viruses were identified in 52% of those instances.
Conclusions
Early viral infections were associated with greater neutrophilic inflammation and bacterial pathogens. Early viral infections appear to contribute to initiation of lower airway inflammation in infants with CF. Antibiotics were commonly prescribed in the setting of a viral infection. Future investigations examining longitudinal relationships between viral infections, airway microbiome, and antibiotic use will allow us to elucidate the interplay between these factors in young children with CF
Exploring spatial heterogeneity of Antarctic sea ice algae using an autonomous underwater vehicle mounted irradiance sensor
Sea ice algae represent a key energy source for many organisms in polar food webs, butestimating their biomass at ecologically appropriate spatiotemporal scales remains achallenge. Attempts to extend ice-core derived biomass to broader scales using remotesensing approaches has largely focused on the use of under-ice spectral irradiance.Normalized difference index (NDI) based algorithms that relate the attenuation ofirradiance by the snow-ice-algal ensemble at specific wavelengths to biomass havebeen used to explain up to 79% of the biomass of algae in limited areas. Application ofthese algorithms to datasets collected using tethered remotely operated vehicles (ROVs)has begun, generating methods for spatial sampling at scales and spatial resolutionnot achievable with ice-core sampling. Successful integration of radiometers withuntethered autonomous underwater vehicles (AUVs) offers even greater capability tosurvey broader regions to explore the spatial heterogeneity of sea ice algal communities.This work describes the pilot use of an AUV fitted with a multispectral irradiance sensorto estimate ice-algal biomass along transects beneath land-fast sea ice (~2 m thick withminimal snow cover) in McMurdo Sound, Antarctica. The AUV obtained continuous,repeatable, multi-band irradiance data, suitable for NDI-type approaches, over transectsof 500 m, with an instrument footprint of 4 m in diameter. Algorithms were developedusing local measurements of ice algae biomass and spectral attenuation of sea iceand were able to explain 40% of biomass variability. Relatively poor performance of thealgorithms in predicting biomass limited the confidence that could be placed in biomassestimates from AUV data. This was attributed to the larger footprint size of the opticalsensors integrating small-scale biomass variability more effectively than the ice core inthe platelet-dominated ice algal habitat. Our results support continued development ofremote-sensing of sea ice algal biomass at m–km spatial scales using optical methods,but caution that footprint sizes of calibration data (e.g., coring) must be compatible withoptical sensors used. AUVs offer autonomous survey techniques that could be appliedto better understand the horizontal variability of sea ice algae from nearshore ice out tothe marginal ice zone
Measurement of direct photon production at Tevatron fixed target energies
Measurements of the production of high transverse momentum direct photons by
a 515 GeV/c piminus beam and 530 and 800 GeV/c proton beams in interactions
with beryllium and hydrogen targets are presented. The data span the kinematic
ranges of 3.5 < p_T < 12 GeV/c in transverse momentum and 1.5 units in
rapidity. The inclusive direct-photon cross sections are compared with
next-to-leading-order perturbative QCD calculations and expectations based on a
phenomenological parton-k_T model.Comment: RevTeX4, 23 pages, 32 figures, submitted to Phys. Rev.
Evidence for Parton kT Effects in High pT Particle Production
Inclusive pizero and direct-photon cross sections in the kinematic range 3.5
< pT < 12 GeV/c with central rapidities are presented for 530 and 800 GeV/c
proton beams and a 515 GeV/c pi- beam incident on beryllium targets. Current
Next-to-Leading-Order perturbative QCD calculations fail to adequately describe
the data for conventional choices of scales. Kinematic distributions from these
hard scattering events provide evidence that the interacting partons carry
significant initial-state parton transverse momentum (kT). Incorporating these
kT effects phenomenologically greatly improves the agreement between
calculations and the measured cross sections.Comment: 11 pages including 6 pages of figures with caption
Production of pizero and eta mesons at large transverse momenta in pi-p and pi-Be interactions at 515 GeV/c
We present results on the production of high transverse momentum pizero and
eta mesons in pi-p and pi-Be interactions at 515 GeV/c. The data span the
kinematic ranges 1 < p_T < 11 GeV/c in transverse momentum and -0.75 < y < 0.75
in rapidity. The inclusive pizero cross sections are compared with
next-to-leading order QCD calculations and to expectations based on a
phenomenological parton-k_T model.Comment: RevTeX4, 15 pages, 15 figures, to be submitted to Phys. Rev.
Precision Determination of the Neutron Spin Structure Function g1n
We report on a precision measurement of the neutron spin structure function
using deep inelastic scattering of polarized electrons by polarized
^3He. For the kinematic range 0.014<x<0.7 and 1 (GeV/c)^2< Q^2< 17 (GeV/c)^2,
we obtain at an average . We find relatively large negative
values for at low . The results call into question the usual Regge
theory method for extrapolating to x=0 to find the full neutron integral
, needed for testing quark-parton model and QCD sum rules.Comment: 5 pages, 3 figures To be published in Phys. Rev. Let
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