Low-loss photonic crystal fibers for transmission systems and their dispersion properties

We report on a single-mode photonic crystal fiber with attenuation and effective area at 1550 nm of 0.48 dB/km and 130 square-micron, respectively. This is, to our knowledge, the lowest loss reported for a PCF not made from VAD prepared silica and at the same time the largest effective area for a low-loss (< 1 dB/km) PCF. We briefly discuss the future applications of PCFs for data transmission and show for the first time, both numerically and experimentally, how the group velocity dispersion is related to the mode field diameterComment: 5 pages including 3 figures + 1 table. Accepted for Opt. Expres

Photonic crystal fiber with a hybrid honeycomb cladding

We consider an air-silica honeycomb lattice and demonstrate a new approach to the formation of a core defect. Typically, a high or low-index core is formed by adding a high-index region or an additional air-hole (or other low-index material) to the lattice, but here we discuss how a core defect can be formed by manipulating the cladding region rather than the core region itself. Germanium-doping of the honeycomb lattice has recently been suggested for the formation of a photonic band-gap guiding silica-core and here we experimentally demonstrate how an index-guiding silica-core can be formed by fluorine-doping of the honeycomb lattice.Comment: 5 pages including 3 figures. Accepted for Optics Expres

The Jefferson Scale of Empathy: a nationwide study of measurement properties, underlying components, latent variable structure, and national norms in medical students.

The Jefferson Scale of Empathy (JSE) is a broadly used instrument developed to measure empathy in the context of health professions education and patient care. Evidence in support of psychometrics of the JSE has been reported in health professions students and practitioners with the exception of osteopathic medical students. This study was designed to examine measurement properties, underlying components, and latent variable structure of the JSE in a nationwide sample of first-year matriculants at U.S. colleges of osteopathic medicine, and to develop a national norm table for the assessment of JSE scores. A web-based survey was administered at the beginning of the 2017-2018 academic year which included the JSE, a scale to detect good impression responses, and demographic/background information. Usable surveys were received from 6009 students enrolled in 41 college campuses (median response rate = 92%). The JSE mean score and standard deviation for the sample were 116.54 and 10.85, respectively. Item-total score correlations were positive and statistically significant (p \u3c 0.01), and Cronbach α = 0.82. Significant gender differences were observed on the JSE scores in favor of women. Also, significant differences were found on item scores between top and bottom third scorers on the JSE. Three factors of Perspective Taking, Compassionate Care, and Walking in Patient\u27s Shoes emerged in an exploratory factor analysis by using half of the sample. Results of confirmatory factor analysis with another half of the sample confirmed the 3-factor model. We also developed a national norm table which is the first to assess students\u27 JSE scores against national data

Analytical description of the 1s exciton linewidth temperature-dependence in transition metal dichalcogenides

We obtain an analytical expression for the linewidth of the 1s exciton as a function of temperature in transition metal dichalcogenides. The total linewidth, as a function of temperature, is dominated by three contributions: (i) the radiative decay (essentially temperature independent), (ii) the phonon-induced intravalley scattering, and (iii) the phonon-induced intervalley scattering. Our approach uses a variational Ansatz to solve the Wannier equation, allowing for an analytical treatment of the excitonic problem, including rates of the decay dynamics. Our results are in good agreement with experimental data already present in the literature and can be used to readily predict the value of the total linewidth at any temperature in the broad class of excitonic two-dimensional materials.N.M.R.P. acknowledges support by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/04650/2020. J.C.G.H. acknowledges the Center of Physics for a grant funded by the UIDB/04650/2020 strategic project and POCI-01-0145FEDER-028887. N.M.R.P. acknowledges support from the European Commission through the project "Graphene-Driven Revolutions in ICT and Beyond" (Ref. No. 881603, CORE 3), COMPETE 2020, PORTUGAL 2020, FEDER, and the FCT through projects POCI-01-0145-FEDER-028114 and PTDC/NAN-OPT/29265/2017. N.A.M. is a VILLUM Investigator supported by VILLUM FONDEN (Grant No. 16498). The Center for Nanostructured Graphene is sponsored by the Danish National Research Foundation (Project No. DNRF103)

Transport coefficients for electrolytes in arbitrarily shaped nano and micro-fluidic channels

We consider laminar flow of incompressible electrolytes in long, straight channels driven by pressure and electro-osmosis. We use a Hilbert space eigenfunction expansion to address the general problem of an arbitrary cross section and obtain general results in linear-response theory for the hydraulic and electrical transport coefficients which satisfy Onsager relations. In the limit of non-overlapping Debye layers the transport coefficients are simply expressed in terms of parameters of the electrolyte as well as the geometrical correction factor for the Hagen-Poiseuille part of the problem. In particular, we consider the limits of thin non-overlapping as well as strongly overlapping Debye layers, respectively, and calculate the corrections to the hydraulic resistance due to electro-hydrodynamic interactions.Comment: 13 pages including 4 figures and 1 table. Typos corrected. Accepted for NJ

Educating law students for rural and regional legal practice: embedding place consciousness in law curricula

As with other professions, the declining rates of recruitment and retention of lawyers in rural and regional Australia is of significant concern. Whilst the causes of this vary between communities, common depictions of the rural and regional lawyer&rsquo;s role indicate that employment as a lawyer in such areas is characterised by unique personal and professional challenges. Nonetheless, employment as a rural and regional lawyer also offers practitioners rewarding opportunities and lifestyle benefits. Research from other disciplines indicates that the challenges inherent in rural and regional professional practice may be alleviated, and benefits more easily harnessed, via place conscious discipline-specific curriculum that sensitises tertiary students to, and prepares them for, the rural and regional career context.Largely oriented towards substantive content to satisfy external accrediting bodies, undergraduate legal education does not typically acknowledge the &lsquo;places&rsquo;in which graduates will practice as professionals. This article argues however that there is scope to incorporate place within legal education, and documents an innovative curriculum development project which embeds place consciousness to better prepare law students for employment in rural and regional legal practice.Drawing upon methods from other disciplines, the project team designed a curriculum package which aims to sensitise students to the rural and regional legal practice context, and equip them with the skills to overcome challenges and take advantage of the opportunities available in a rural or regional professional career

A high-field adiabatic fast passage ultracold neutron spin flipper for the UCNA experiment

The UCNA collaboration is making a precision measurement of the β asymmetry (A) in free neutron decay using polarized ultracold neutrons (UCN). A critical component of this experiment is an adiabatic fast passage neutron spin flipper capable of efficient operation in ambient magnetic fields on the order of 1 T. The requirement that it operate in a high field necessitated the construction of a free neutron spin flipper based, for the first time, on a birdcage resonator. The design, construction, and initial testing of this spin flipper prior to its use in the first measurement of A with UCN during the 2007 run cycle of the Los Alamos Neutron Science Center's 800 MeV proton accelerator is detailed. These studies determined the flipping efficiency of the device, averaged over the UCN spectrum present at the location of the spin flipper, to be ϵ(overbar) = 0.9985(4)

Bayesian Error Estimation in Density Functional Theory

We present a practical scheme for performing error estimates for Density Functional Theory calculations. The approach which is based on ideas from Bayesian statistics involves creating an ensemble of exchange-correlation functionals by comparing with an experimental database of binding energies for molecules and solids. Fluctuations within the ensemble can then be used to estimate errors relative to experiment on calculated quantities like binding energies, bond lengths, and vibrational frequencies. It is demonstrated that the error bars on energy differences may vary by orders of magnitude for different systems in good agreement with existing experience.Comment: 5 pages, 3 figure

Capillarity in pressure infiltration: improvements in characterization of high-temperature systems

In the pressure infiltration of metal matrix composites, molten metal is injected under external pressure into a porous preform of the reinforcing material. Equilibrium capillary parameters characterizing wetting for this process are summarized in plots of metal saturation versus applied pressure, also known as drainage curves. Such curves can be measured in our laboratory during a single experiment with an infiltration apparatus designed to track the rate of metal penetration into porous preforms under conditions characteristic of metal matrix composite processing (temperatures in excess of 1000°C and pressures in the order of 10MPa). For such measurements to be valid, infiltration of the preform with molten metal must be mechanically quasi-static, i.e., the metal must flow at a rate sufficiently low for the metal pressure to be essentially uniform across the preform at all times. We examine this requirement quantitatively, using a finite-difference model that simulates the unsaturated unidirectional ingress of molten metal into a ceramic particle preform of finite width. We furthermore present improvements in the experimental apparatus developed in our laboratory to measure the entire drainage curve in a single experiment. We compare numerical results with new experimental data for the copper/alumina system to show (i) that pressurization rates sufficiently low for quasi-static infiltration can be produced with this apparatus, and (ii) that taking the relative permeability equal to the saturation yields better agreement with experiment than does the expression originally proposed by Brooks and Core