“Home Again”: The Contrasting Experiences of Richard D. Dunphy and Lewis A. Horton

Union veterans returning home from the war in 1865 faced a myriad of experiences and reacted to the return to civilian life in a variety of ways. Richard D. Dunphy and Lewis A. Horton, both double-arm amputee veterans of the Navy, ably demonstrate the differences in experience and reaction to the war and life afterwards. [excerpt

Rotational Doppler velocimetry to probe the angular velocity of spinning microparticles

Laser Doppler velocimetry is a technique used to measure linear velocity, ranging from that of exhaust gases to blood flow. A rotational analog of laser Doppler velocimetry was recently demonstrated, using a rotationally symmetric interference pattern to probe the angular velocity of a spinning object. In this work, we demonstrate the use of a diffraction-limited structured illumination pattern to measure the angular velocity of a micron-sized particle trapped and spinning at tens of Hz in an optical trap. The technique requires no detailed knowledge of the shape of the particle, or the distribution of scatterers within it, and is independent of the particle's chirality, transparency, and birefringence. The particle is also subjected to Brownian motion, which complicates the signal by affecting the rotation rate and the rotation axis. By careful consideration of these influences, we show how the measurement is robust to both, representing a technique with which to probe the rotational motion of microscale particles

Reviews and syntheses: 210Pb-derived sediment and carbon accumulation rates in vegetated coastal ecosystems-setting the record straight

Vegetated coastal ecosystems, including tidal marshes, mangroves and seagrass meadows, are being increasingly assessed in terms of their potential for carbon dioxide sequestration worldwide. However, there is a paucity of studies that have effectively estimated the accumulation rates of sediment organic carbon (Corg), also termed blue carbon, beyond the mere quantification of Corg stocks. Here, we discuss the use of the 210Pb dating technique to determine the rate of Corg accumulation in these habitats. We review the most widely used 210Pb dating models to assess their limitations in these ecosystems, often composed of heterogeneous sediments with varying inputs of organic material, that are disturbed by natural and anthropogenic processes resulting in sediment mixing and changes in sedimentation rates or erosion. Through a range of simulations, we consider the most relevant processes that impact the 210Pb records in vegetated coastal ecosystems and evaluate how anomalies in 210Pb specific activity profiles affect sediment and Corg accumulation rates. Our results show that the discrepancy in sediment and derived Corg accumulation rates between anomalous and ideal 210Pb profiles is within 20% if the process causing such anomalies is well understood. While these discrepancies might be acceptable for the determination of mean sediment and Corg accumulation rates over the last century, they may not always provide a reliable geochronology or historical reconstruction. Reliable estimates of Corg accumulation rates might be difficult at sites with slow sedimentation, intense mixing and/or that are affected by multiple sedimentary processes. Additional tracers or geochemical, ecological or historical data need to be used to validate the 210Pbderived results. The framework provided in this study can be instrumental in reducing the uncertainties associated with estimates of Corg accumulation rates in vegetated coastal sediments.This work was funded by the CSIRO Flagship Marine & Coastal Carbon Biogeochemical Cluster (Coastal Carbon Cluster), the Spanish Ministry of Economy and Competitiveness (projects EstresX CTM2012-32603, MedShift CGL2015-71809-P), the Generalitat de Catalunya (MERS 2017 SGR – 1588), the Australian Research Council LIEF Project (LE170100219), the Edith Cowan University Faculty Research Grant Scheme and the King Abdullah University of Science and Technology (KAUST) through baseline funding to Carlos M. Duarte. This work contributes to the ICTA Unit of Excellence (MinECo, MDM2015-0552

High-dimensional quantum cryptography with twisted light

Quantum key distributions (QKD) systems often rely on polarization of light for encoding, thus limiting the amount of information that can be sent per photon and placing tight bounds on the error that such a system can tolerate. Here we describe a proof-of-principle experiment that indicates the feasibility of high-dimensional QKD based on the transverse structure of the light field, allowing for the transfer of more than 1 bit per photon. Our implementation uses the orbital angular momentum (OAM) of photons and the corresponding mutually unbiased basis of angular position (ANG). Our experiment uses a digital micro-mirror device for the rapid generation of OAM and ANG modes at 4 kHz, and a mode sorter capable of sorting single photons based on their OAM and ANG content with a separation efficiency of 93\%. Through the use of a 7-dimensional alphabet encoded in the OAM and ANG bases, we achieve a channel capacity of 2.05 bits per sifted photon. Our experiment shows that, in addition to having an increased information capacity, QKD systems based on spatial-mode encoding will be more tolerant to errors and thus more robust against eavesdropping attacks

The Orbital Angular Momentum of Light for Ultra-High Capacity Data Centers

The potential of orbital angular momentum (OAM) of light in data center scenarios is presented. OAMs can be exploited for short reach ultra-high bit rate fiber links and as additional multiplexing domain in transparent ultra-high capacity optical switches. Recent advances on OAM integrated photonic technology are also reported. Finally demonstration of OAM-based fiber links (aggregate throughput 17.9 Tb/s) and two layers OAM-WDM-based optical switches are presented exploiting OAM integrated components and demonstrating the achievable benefits in terms of size, weight and power consumption (SWaP) compared to different technologies

Real time 100 Gbit/s electrical Nyquist WDM transmitter

We demonstrate the use of passive electrical filters to produce high quality spectrally-shaped 29 Gbaud WDM signals with a 20 dB bandwidth of 32 GHz, a roll-off of 4.8 dB/GHz and a required OSNR of 12.1 dB

Weak Gravitational Lensing by a Sample of X-Ray Luminous Clusters of Galaxies -- II. Comparison with Virial Masses

Dynamic velocity dispersion and mass estimates are given for a sample of five X-ray luminous rich clusters of galaxies at intermediate redshifts (z~0.3) drawn from a sample of 39 clusters for which we have obtained gravitational lens mass estimates. The velocity dispersions are determined from between 9 and 20 redshifts measured with the LDSS spectrograph of the William Herschel Telescope, and virial radii are determined from imaging using the UH8K mosaic CCD camera on the University of Hawaii 2.24m telescope. Including clusters with velocity dispersions taken from the literature, we have velocity dispersion estimates for 12 clusters in our gravitational lensing sample. For this sample we compare the dynamical velocity dispersion estimates with our estimates of the velocity dispersions made from gravitational lensing by fitting a singular isothermal sphere profile to the observed tangential weak lensing distortion as a function of radius. In all but two clusters, we find a good agreement between the velocity dispersion estimates based on spectroscopy and on weak lensing.Comment: 9 pages, 4 figures, accepted for publication in ApJ. Version in emulateapj format with only minor change