scholarly journals Light path averages in spacetimes with nonvanishing average spatial curvature

2019 ◽  
Vol 100 (6) ◽  
Author(s):  
S. M. Koksbang
Keyword(s):  
Light Path ◽  
Spatial Curvature

scholarly journals Microfluidic Optical Shutter Flexibly x-y Actuated via Electrowetting-on-Dielectrics with <20 ms Response Time

2017 ◽  
Vol 2017 ◽  
pp. 1-5
Author(s):  
Henning Fouckhardt ◽  
Johannes Strassner ◽  
Carina Heisel ◽  
Dominic Palm ◽  
Christoph Doering
Keyword(s):  
Optical Properties ◽  
Response Time ◽  
Visible Spectral Range ◽  
Contact Structures ◽  
Light Path ◽  
Cell Type ◽  
Electrically Conductive ◽  
Droplet Movement ◽  
In Series ◽  
Optical Shutter

Tunable microoptics deals with devices of which the optical properties can be changed during operation without mechanically moving solid parts. Often a droplet is actuated instead, and thus tunable microoptics is closely related to microfluidics. One such device/module/cell type is an optical shutter, which is moved in or out of the path of the light. In our case the transmitting part comprises a moving transparent and electrically conductive water droplet, embedded in a nonconductive blackened oil, that is, an opaque emulsion with attenuation of 30 dB at 570 nm wavelength over the 250 μm long light path inside the fluid (15 dB averaged over the visible spectral range). The insertion loss of the cell is 1.5 dB in the “open shutter” state. The actuation is achieved via electrowetting-on-dielectrics (EWOD) with rectangular AC voltage pulses of 2·90 V peak-to-peak at 1 kHz. To flexibly allow for horizontal, vertical, and diagonal droplet movement in the upright x-y plane, the contact structures are prepared such that four possible stationary droplet positions exist. The cell is configured as two capacitors in series (along the z axis), such that EWOD forces act symmetrically in the front and back of the 60 nl droplet with a response time of <20 ms.

scholarly journals DARK MATTER, AND ITS DARKNESS

2006 ◽  
Vol 15 (12) ◽  
pp. 2267-2278 ◽  
Author(s):  
D. V. AHLUWALIA-KHALILOVA
Keyword(s):  
Dark Matter ◽  
Standard Model ◽  
Cosmological Constant ◽  
Model Material ◽  
Representation Space ◽  
Spatial Curvature ◽  
The Standard Model ◽  
General Relativistic ◽  
Relativistic Description ◽  
Friedmann Robertson Walker

Assuming the validity of the general relativistic description of gravitation on astrophysical and cosmological length scales, we analytically infer that the Friedmann–Robertson–Walker cosmology with Einsteinian cosmological constant, and a vanishing spatial curvature constant, unambiguously requires a significant amount of dark matter. This requirement is consistent with other indications for dark matter. The same space–time symmetries that underlie the freely falling frames of Einsteinian gravity also provide symmetries which, for the spin one half representation space, furnish a novel construct that carries extremely limited interactions with respect to the terrestrial detectors made of the standard model material. Both the "luminous" and "dark" matter turn out to be residents of the same representation space but they derive their respective "luminosity" and "darkness" from either belonging to the sector with (CPT)2 = +𝟙, or to the sector with (CPT)2 = -𝟙.

Productivity ofChlorella sorokinianain a short light-path (SLP) panel photobioreactor under high irradiance

2009 ◽  
Vol 104 (2) ◽  
pp. 352-359 ◽  
Author(s):  
María Cuaresma ◽  
Marcel Janssen ◽  
Carlos Vílchez ◽  
René H. Wijffels
Keyword(s):  
High Irradiance ◽  
Light Path

MODELLING HYDROGEN CLEARANCE FROM THE RETINA

2018 ◽  
Vol 59 (3) ◽  
pp. 281-292
Author(s):  
D. E. FARROW ◽  
G. C. HOCKING ◽  
S. J. CRINGLE ◽  
D.-Y. YU
Keyword(s):  
Blood Flow ◽  
Oxygen Supply ◽  
Retinal Blood Flow ◽  
Experimental Measurements ◽  
Human Retina ◽  
Light Path ◽  
Tissue Oxygen ◽  
Sophisticated Model ◽  
Tissue Oxygen Supply ◽  
Hydrogen Clearance

The human retina is supplied by two vascular systems: the highly vascular choroidal, situated behind the retina; and the retinal, which is dependent on the restriction that the light path must be minimally disrupted. Between these two circulations, the avascular retinal layers depend on diffusion of metabolites through the tissue. Oxygen supply to these layers may be threatened by diseases affecting microvasculature, for example diabetes and hypertension, which may ultimately cause loss of sight.An accurate model of retinal blood flow will therefore facilitate the study of retinal oxygen supply and, hence, the complications caused by systemic vascular disease. Here, two simple models of the blood flow and exchange of hydrogen with the retina are presented and compared qualitatively with data obtained from experimental measurements. The models capture some interesting features of the exchange and highlight effects that will need to be considered in a more sophisticated model and in the interpretation of experimental results.

scholarly journals Model-independent constraints on cosmic curvature: implication from the future space gravitational-wave antenna DECIGO

2021 ◽  
Vol 81 (1) ◽  
Author(s):  
Xiaogang Zheng ◽  
Shuo Cao ◽  
Yuting Liu ◽  
Marek Biesiada ◽  
Tonghua Liu ◽  
...  
Keyword(s):  
Gravitational Wave ◽  
Future Generation ◽  
Spatial Curvature ◽  
Hubble Diagram ◽  
Einstein Telescope ◽  
Future Space ◽  
Local Measurements ◽  
New Type ◽  
Model Independent ◽  
Hubble Parameters

AbstractIn order to estimate cosmic curvature from cosmological probes like standard candles, one has to measure the luminosity distance $$D_L(z)$$ D L ( z ) , its derivative with respect to redshift $$D'_L(z)$$ D L ′ ( z ) and the expansion rate H(z) at the same redshift. In this paper, we study how such idea could be implemented with future generation of space-based DECi-hertz Interferometer Gravitational-wave Observatory (DECIGO), in combination with cosmic chronometers providing cosmology-independent H(z) data. Our results show that for the Hubble diagram of simulated DECIGO data acting as a new type of standard siren, it would be able to constrain cosmic curvature with the precision of $$\varDelta \varOmega _k= 0.09$$ Δ Ω k = 0.09 with the currently available sample of 31 measurements of Hubble parameters. In the framework of the third generation ground-based gravitational wave detectors, the spatial curvature is constrained to be $$\varDelta \varOmega _k= 0.13$$ Δ Ω k = 0.13 for Einstein Telescope (ET). More interestingly, compared to other approaches aiming for model-independent estimations of spatial curvature, our analysis also achieve the reconstruction of the evolution of $$\varOmega _k(z)$$ Ω k ( z ) , in the framework of a model-independent method of Gaussian processes (GP) without assuming a specific form. Therefore, one can expect that the newly emerged gravitational wave astronomy can become useful in local measurements of cosmic curvature using distant sources.

scholarly journals 3D-printed Planktonic Observational Setup and Analysis Pipeline TrackmateTaxis

2020 ◽  
Author(s):  
Clemens C. Döring ◽  
Harald Hausen
Keyword(s):  
Pulse Width ◽  
Pulse Width Modulation ◽  
Photon Emission ◽  
Three Dimensional ◽  
Behavioral Observation ◽  
Swimming Behavior ◽  
Robust Tracking ◽  
Light Path ◽  
Analysis Pipeline ◽  
3D Printed

AbstractPlanktonic organisms are a cornerstone of marine ecosystems. They vary significantly in size and have a repertoire of behaviors to aid them to survive and navigate their three-dimensional environment. One of the most important cues is light. A variety of setups were used to study the swimming behavior of specific organisms, but broader and comparative investigations need more versatile solutions. With the help of 3D printing, we designed and constructed a modular and flexible behavioral observation setup that enables recordings of animals down to 50μm or up to a few centimeters. A video analysis pipeline using ImageJ and python allows a quick, automated, and robust tracking solution, capable of processing many videos automatically. A modular light path allows the addition of filters or use of pulse width modulation to equalize photon emission of LEDs or additional LEDs to mix different wavelengths. Optionally, a spectrometer can be installed to enable live monitoring of a stimulus. We tested the setup with two phototactic marine planktonic larvae. First, we investigated the spectral sensitivity of the 7-day old larvae of the polychaete Malacoceros fuliginosus and second, the behavior of the 200μm spherical bryozoan coronated larvae of Tricellaria inopinata to ultraviolet light coming from the bottom of the vessel. The setup and pipeline were able to record and analyze hundreds of animals simultaneously. We present an inexpensive, modular, and flexible setup to study planktonic behavior of a variety of sizes.

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