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space travel

Ling Ji, Jun Gao, Ai-Lin Yang, Zhen Feng, Xiao-Feng Lin, Zhong-Gen Li, Xian-Min Jin
Long-distance quantum channels capable of transferring quantum states faithfully for unconditionally secure quantum communication have been so far confirmed to be feasible in both fiber and free-space air. However, it remains unclear whether seawater, which covers more than 70% of the earth, can also be utilized, leaving global quantum communication incomplete. Here we experimentally demonstrate that polarization quantum states including general qubits of single photon and entangled states can survive well after travelling through seawater...
August 21, 2017: Optics Express
Andreas Steinbacher, Heiko Hildenbrand, Sebastian Schott, Johannes Buback, Marco Schmid, Patrick Nuernberger, Tobias Brixner
We present an optical setup capable of mirroring an arbitrary, potentially time-varying, polarization state of an ultrashort laser pulse. The incident beam is split up in two and the polarization of one beam is mirrored by reflection off a mirror in normal incidence. Afterwards, both beams are recombined in time and space such that two collinear ultrashort laser pulses with mutually mirrored polarization, i.e., laser-pulse enantiomers, leave the setup. We employ the Jones formalism to describe the function of the setup and analyze the influence of alignment errors before describing the experimental implementation and alignment protocol...
September 4, 2017: Optics Express
F Wang, J Li, G Martinez-Piedra, O Korotkova
We introduce theoretically and realize experimentally a class of random, wide-sense stationary optical beams with uniform correlations which, on propagation in free space, produce a crescent-like intensity distribution with the maximum at an off-axis position. The crescent's position of maximum intensity accelerates transversally at intermediate distances, and then exhibits a constant lateral shift further from the axis in the far zone of the source. We also show that on propagation in the isotropic turbulent atmosphere, the crescent beam shifts away from the axis as well, but slower than in free space, with rate depending on the strength of turbulence...
October 16, 2017: Optics Express
James N Dodds, Jody C May, John A McLean
Here we examine the relationship between resolving power (Rp), resolution (Rpp), and collision cross section (CCS) for compounds analyzed in previous ion mobility (IM) experiments representing a wide variety of instrument platforms and IM techniques. Our previous work indicated these three variables effectively describe and predict separation efficiency for drift tube ion mobility spectrometry (DTIMS) experiments. In this work we seek to determine if our previous findings are a general reflection of IM behavior applicable to various instrument platforms and mobility techniques...
October 17, 2017: Analytical Chemistry
Joe Yuichiro Wakano, William Gilpin, Seiji Kadowaki, Marcus W Feldman, Kenichi Aoki
Recent archaeological records no longer support a simple dichotomous characterization of the cultures/behaviors of Neanderthals and modern humans, but indicate much cultural/behavioral variability over time and space. Thus, in modeling the replacement or assimilation of Neanderthals by modern humans, it is of interest to consider cultural dynamics and its relation to demographic change. The ecocultural framework for the competition between hominid species allows their carrying capacities to depend on some measure of the levels of culture they possess...
October 12, 2017: Theoretical Population Biology
A P Riascos, José L Mateos
There is a burst of work on human mobility and encounter networks. However, the connection between these two important fields just begun recently. It is clear that both are closely related: Mobility generates encounters, and these encounters might give rise to contagion phenomena or even friendship. We model a set of random walkers that visit locations in space following a strategy akin to Lévy flights. We measure the encounters in space and time and establish a link between walkers after they coincide several times...
2017: PloS One
Reece D Pedler, Raoul F H Ribot, Andrew T D Bennett
Understanding and conserving mobile species presents complex challenges, especially for animals in stochastic or changing environments. Nomadic waterbirds must locate temporary water in arid biomes where rainfall is highly unpredictable in space and time. To achieve this they need to travel over vast spatial scales and time arrival to exploit pulses in food resources. How they achieve this is an enduring mystery.  We investigated these challenges in the colonial-nesting Banded Stilt (Cladorhynchus leucocephalus), a nomadic shorebird of conservation concern...
October 5, 2017: Conservation Biology: the Journal of the Society for Conservation Biology
Lachlan Fleetwood
East India Company surveyors began gaining access to the high Himalaya in the 1810s, at a time when the mountains were taking on increasing political significance as the northern borderlands of British India. Though never as idiosyncratic as surveyors insisted, these were spaces in which instruments, fieldbook inscriptions, and bodies were all highly prone to failure. The ways surveyors managed these failures (both rhetorically and in practice) demonstrate the social performances required to establish credible knowledge in a world in which the senses were scrambled...
October 1, 2017: History of Science; An Annual Review of Literature, Research and Teaching
Ivo Dobrev, Jae Hoon Sim, Stefan Stenfelt, Sebastian Ihrle, Rahel Gerig, Flurin Pfiffner, Albrecht Eiber, Alexander M Huber, Christof Röösli
BACKGROUND: Bone conduction (BC) is an alternative to air conduction to stimulate the inner ear. In general, the stimulation for BC occurs on a specific location directly on the skull bone or through the skin covering the skull bone. The stimulation propagates to the ipsilateral and contralateral cochlea, mainly via the skull bone and possibly via other skull contents. This study aims to investigate the wave propagation on the surface of the skull bone during BC stimulation at the forehead and at ipsilateral mastoid...
September 23, 2017: Hearing Research
Marco Cardis, Maura Casadio, Rajiv Ranganathan
Motor variability plays an important role in motor learning, although the exact mechanisms of how variability affects learning is not well understood. Recent evidence suggests that motor variability may have different effects on learning in redundant tasks, depending on whether it is present in the task space (where it affects task performance), or in the null space (where it has no effect on task performance). Here we examined the effect of directly introducing null and task space variability using a manipulandum during the learning of a motor task...
September 27, 2017: Journal of Neurophysiology
Marie-Liesse Asselin-Labat, Rishi Rampersad, Xia Xu, Matthew E Ritchie, Jacob Michalski, Lingling Huang, Mark W Onaitis
High-linear energy transfer (LET) radiation encountered by astronauts in space generates clustered DNA damage that is potentially oncogenic. Analysis of the impact of exposure to space radiation on cancer formation is necessary to determine the best ways to prepare astronauts for space travel so they are protected for the duration of the space mission. A mouse model of lung adenocarcinoma driven by oncogenic K-Ras was used to ascertain the effect of low- and high-LET radiation on tumor formation. We observed increased tumor progression and tumor cell proliferation after single dose or fractionated high-LET doses, which was not observed in mice exposed to low-LET radiation...
September 27, 2017: Radiation Research
Alireza Karduni, Isaac Cho, Ginette Wessel, William Ribarsky, Eric Sauda, Wenwen Dou
Understanding people's behavior is fundamental to many planning professions (including transportation, community development, economic development, and urban design) that rely on data about frequently traveled routes, places, and social and cultural practices. Based on the results of a practitioner survey, the authors designed Urban Space Explorer, a visual analytics system that utilizes mobile social media to enable interactive exploration of public-space-related activity along spatial, temporal, and semantic dimensions...
2017: IEEE Computer Graphics and Applications
Cody W Whoolery, Angela K Walker, Devon R Richardson, Melanie J Lucero, Ryan P Reynolds, David H Beddow, K Lyles Clark, Hung-Ying Shih, Junie A LeBlanc, Mara G Cole, Wellington Z Amaral, Shibani Mukherjee, Shichuan Zhang, Francisca Ahn, Sarah E Bulin, Nathan A DeCarolis, Phillip D Rivera, Benjamin P C Chen, Sanghee Yun, Amelia J Eisch
Astronauts traveling to Mars will be exposed to chronic low doses of galactic cosmic space radiation, which contains highly charged, high-energy (HZE) particles. (56)Fe-HZE-particle exposure decreases hippocampal dentate gyrus (DG) neurogenesis and disrupts hippocampal function in young adult rodents, raising the possibility of impaired astronaut cognition and risk of mission failure. However, far less is known about how exposure to other HZE particles, such as (28)Si, influences hippocampal neurogenesis and function...
September 25, 2017: Radiation Research
Miho Iryo-Asano, Wael K M Alhajyaseen
Pedestrian safety is one of the most challenging issues in road networks. Understanding how pedestrians maneuver across an intersection is the key to applying countermeasures against traffic crashes. It is known that the behaviors of pedestrians at signalized crosswalks are significantly different from those in ordinary walking spaces, and they are highly influenced by signal indication, potential conflicts with vehicles, and intersection geometries. One of the most important characteristics of pedestrian behavior at crosswalks is the possible sudden speed change while crossing...
November 2017: Accident; Analysis and Prevention
Azadeh Hekmat, Zahra Hajebrahimi, Amir Motamedzade
Nowadays, the biological effects of microgravity have been the subject of various experimental researches. The purpose of this study was to investigate the probable biological effects of microgravity on the human serum albumin (HSA) structure after 3 and 24 h exposure via various spectroscopic instruments. The UV-Visible, near-UV-CD and intrinsic fluorescence spectroscopy represented that microgravity can remarkably change the tertiary structure of HSA. Additionally, the ANS affinity for HSA incremented when the protein was exposed to simulate microgravity compared to unexposed HSA, which may possibly have appeared attributable to expansion of the structure of simulated HSA...
September 17, 2017: Protein and Peptide Letters
Bin Cai, Harold Li, Deshan Yang, Vivian Rodriguez, Austen Curcuru, Yuhe Wang, Jie Wen, Rojano Kashani, Sasa Mutic, Olga Green
PURPOSE: The purpose of this study was to investigate and characterize the performance of a Multi Leaf Collimator (MLC) designed for Cobalt-60 based MR-guided radiation therapy system in a 0.35 T magnetic field. METHODS: The MLC design and unique assembly features in the ViewRay MRIdian system were first reviewed. The RF cage shielding of MLC motor and cables were evaluated using ACR phantoms with real-time imaging and quantified by signal-to-noise ratio. The dosimetric characterizations, including the leaf transmission, leaf penumbra, tongue-and-groove effect, were investigated using radiosensitive films...
September 9, 2017: Medical Physics
Natalia Tejedor-Garavito, Nomcebo Dlamini, Deepa Pindolia, Adam Soble, Nick W Ruktanonchai, Victor Alegana, Arnaud Le Menach, Nyasatu Ntshalintshali, Bongani Dlamini, David L Smith, Andrew J Tatem, Simon Kunene
BACKGROUND: As Swaziland progresses towards national malaria elimination, the importation of parasites into receptive areas becomes increasingly important. Imported infections have the potential to instigate local transmission and sustain local parasite reservoirs. METHODS: Travel histories from Swaziland's routine surveillance data from January 2010 to June 2014 were extracted and analysed. The travel patterns and demographics of rapid diagnostic test (RDT)-confirmed positive cases identified through passive and reactive case detection (RACD) were analysed and compared to those found to be negative through RACD...
September 8, 2017: Malaria Journal
Naseem Cassim, Honora Smith, Lindi M Coetzee, Deborah K Glencross
INTRODUCTION: CD4 testing in South Africa is based on an integrated tiered service delivery model that matches testing demand with capacity. The National Health Laboratory Service has predominantly implemented laboratory-based CD4 testing. Coverage gaps, over-/under-capacitation and optimal placement of point-of-care (POC) testing sites need investigation. OBJECTIVES: We assessed the impact of relational algebraic capacitated location (RACL) algorithm outcomes on the allocation of laboratory and POC testing sites...
2017: African Journal of Laboratory Medicine
Marta M Iversen, Richard D Rabbitt
The semicircular canals are biomechanical sensors responsible for detecting and encoding angular motion of the head in 3D space. Canal afferent neurons provide essential inputs to neural circuits responsible for representation of self-position/orientation in space, and to compensatory circuits including the vestibulo-ocular and vestibulo-collic reflex arcs. In this work we derive, to our knowledge, a new 1D mathematical model quantifying canal biomechanics based on the morphology, dynamics of the inner ear fluids, and membranous labyrinth deformability...
September 5, 2017: Biophysical Journal
D A Walsh, D S Lake, E W Snedden, M J Cliffe, D M Graham, S P Jamison
The sub-luminal phase velocity of electromagnetic waves in free space is generally unobtainable, being closely linked to forbidden faster than light group velocities. The requirement of sub-luminal phase-velocity in laser-driven particle acceleration schemes imposes a limit on the total acceleration achievable in free space, and necessitates the use of dispersive structures or waveguides for extending the field-particle interaction. We demonstrate a travelling source approach that overcomes the sub-luminal propagation limits...
September 4, 2017: Nature Communications
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