Theoretical studies of the physics of the solar atmosphere

NASA Technical Reports Server (NTRS)

Hollweg, Joseph V.

1992-01-01

Significant advances in our theoretical basis for understanding several physical processes related to dynamical phenomena on the sun were achieved. We have advanced a new model for spicules and fibrils. We have provided a simple physical view of resonance absorption of MHD surface waves; this allowed an approximate mathematical procedure for obtaining a wealth of new analytical results which we applied to coronal heating and p-mode absorption at magnetic regions. We provided the first comprehensive models for the heating and acceleration of the transition region, corona, and solar wind. We provided a new view of viscosity under coronal conditions. We provided new insights into Alfven wave propagation in the solar atmosphere. And recently we have begun work in a new direction: parametric instabilities of Alfven waves.

Absorption of Sunlight by Water Vapor in Cloudy Conditions: A Partial Explanation for the Cloud Absorption Anomaly

NASA Technical Reports Server (NTRS)

Crisp, D.

1997-01-01

The atmospheric radiative transfer algorithms used in most global general circulation models underestimate the globally-averaged solar energy absorbed by cloudy atmospheres by up to 25 W/sq m. The origin of this anomalous absorption is not yet known, but it has been attributed to a variety of sources including oversimplified or missing physical processes in these models, uncertainties in the input data, and even measurement errors. Here, a sophisticated atmospheric radiative transfer model was used to provide a more comprehensive description of the physical processes that contribute to the absorption of solar radiation by the Earth's atmosphere. We found that the amount of sunlight absorbed by a cloudy atmosphere is inversely proportional to the solar zenith angle and the cloud top height, and directly proportional to the cloud optical depth and the water vapor concentration within the clouds. Atmospheres with saturated, optically-thick, low clouds absorbed about 12 W/sq m more than clear atmospheres. This accounts for about 1/2 to 1/3 of the anomalous ab- sorption. Atmospheres with optically thick middle and high clouds usually absorb less than clear atmospheres. Because water vapor is concentrated within and below the cloud tops, this absorber is most effective at small solar zenith angles. An additional absorber that is distributed at or above the cloud tops is needed to produce the amplitude and zenith angle dependence of the observed anomalous absorption.

[Current concepts of digestion and absorption of carbohydrates].

PubMed

Luz, S dos S; de Campos, P L; Ribeiro, S M; Tirapegui, J

1997-01-01

The aim of this paper is to review recent aspects of digestion and absorption of carbohydrates that are the main source of energy in human diets. Recent researches have found that starch is not largely hydrolysed and absorbed in the small bowel but one part of it is resistant to digestion. Several food factors may be responsible for digestion and absorption velocity and totality of carbohydrates. Therefore, carbohydrate classification must be based not only on molecular size to express the real carbohydrates utilization as an energy source by humans. In agreement with molecular size of carbohydrate, its classification can be: a) monosaccharides; b) disaccharides; c) oligosaccharides; d) polysaccharides. In agreement with carbohydrate digestibility or availability, its classification can be: a) digestible carbohydrates; b) undigestable carbohydrates (NSP). Carbohydrate digestibility can be altered by several factors like: Intrinsic factors: a) physical structure; b) molecular physical distribution; c) physical state of food; d) food antinutrients. Extrinsics factors: a) chewing; b) transit time of food; c) amount of starch present; d) diet antinutrients. Under influence of this factors, process of digestion happen by enzymatic activity a long the gastrointestinal tract. Salivary and pancreatic amylase; glycosidases of the duodenal enterocyte brush border (lactase, sacarase and maltase), whose activity happen by close interaction of digestive breakdown with transport. The summarized pathways of the absorptive process: 1. movement from the bulk phase of the lumenal or mucosal fluid to enterocyte surface; 2. movement across the brush border membrane through specific transporters: a) SGLT1; b) GLUT 5; c) passive diffusion. 3. movement across the basolateral membrane by the GLUT 2.

Multiphoton microscopy for the in-situ investigation of cellular processes and integrity in cryopreservation.

PubMed

Doerr, Daniel; Stark, Martin; Ehrhart, Friederike; Zimmermann, Heiko; Stracke, Frank

2009-08-01

In this study we demonstrate a new noninvasive imaging method to monitor freezing processes in biological samples and to investigate life in the frozen state. It combines a laser scanning microscope with a computer-controlled cryostage. Nearinfrared (NIR) femtosecond laser pulses evoke the fluorescence of endogenous fluorophores and fluorescent labels due to multiphoton absorption.The inherent optical nonlinearity of multiphoton absorption allows 3D fluorescence imaging for optical tomography of frozen biological material in-situ. As an example for functional imaging we use fluorescence lifetime imaging (FLIM) to create images with chemical and physical contrast.

Laponite crosslinked starch/polyvinyl alcohol hydrogels by freezing/thawing process and studying their cadmium ion absorption.

PubMed

Yu, Chen; Tang, Xiaozhi; Liu, Shaowei; Yang, Yuling; Shen, Xinchun; Gao, Chengcheng

2018-05-22

In this study, Laponite RD (LRD) cross-linked hydrogels consisting of starch, polyvinyl alcohol (PVA) were prepared by freezing/thawing process and the influence of LRD content on structure and properties of hydrogels was investigated. FTIR showed a new structure of hydrogen bonding might result from cross-linking reactions between LRD and polymers. X-ray diffraction (XRD) analysis showed that high degree of exfoliation of LRD clay layers had occurred during the preparation of hydrogels. The synergistic effect of physical cross-linking by freeze/thaw cycles and by LRD led to more porous, uniform and stable network, which was shown in SEM images. The melting temperature decreased and thermal stability got improved with the increase of LRD content. Reswelling ratios of hydrogels had the highest value when LRD content was 10%. Additionally, cadmium ion absorption capacity of the hydrogel was studied and the results showed that increasing the concentration of LRD increased absorption ratio and amount of Cd 2+ ion in the solution. In a word, LRD could be used as a physical crosslinker and reinforced agent for starch-PVA based hydrogels and the formed hydrogels could be used as novel type and high capacity absorbent materials in heavy metal removing processes. Copyright © 2018. Published by Elsevier B.V.

Utilization of red mud and bagasse for production of gas absorption materials

NASA Astrophysics Data System (ADS)

Thang, Nguyen Hoc; Quyen, Pham Vo Thi Ha; Nhung, Le Thuy; Phong, Dang Thanh; Tuyen, Nguyen Ngoc Kim

2018-04-01

Gas treatment or/and gas absorption is field which has more investigation from researchers. They are finding optimal solutions from catalyst or synthesized materials to obtain the best benefit for factories and community. This study would like to introduce a method to synthesis the gas absorption materials responding requirements for the process of gas treatment. More specially, raw materials used to produce the materials are industrial waste impacting negatively on the environment. In which, red mud is solid waste of Bayer process from bauxite mining which is being the hard problem to have solutions for its management and utilization, and bagasse is industrial waste of sugar factories. Both red mud and bagasse were dried, ground, and sieved and then mixed with bentonite and water for forming by wet pressing method. Continuously, the mixtures were passed processes of heat treatment at 400°C. The final samples were tested physic-chemical properties and characterized for microstructure. The productions were also tested for gas absorption capacity with data obtained very positive in comparison with others.

Trident: A Universal Tool for Generating Synthetic Absorption Spectra from Astrophysical Simulations

NASA Astrophysics Data System (ADS)

Hummels, Cameron B.; Smith, Britton D.; Silvia, Devin W.

2017-09-01

Hydrodynamical simulations are increasingly able to accurately model physical systems on stellar, galactic, and cosmological scales; however, the utility of these simulations is often limited by our ability to directly compare them with the data sets produced by observers: spectra, photometry, etc. To address this problem, we have created trident, a Python-based open-source tool for post-processing hydrodynamical simulations to produce synthetic absorption spectra and related data. trident can (I) create absorption-line spectra for any trajectory through a simulated data set mimicking both background quasar and down-the-barrel configurations; (II) reproduce the spectral characteristics of common instruments like the Cosmic Origins Spectrograph; (III) operate across the ultraviolet, optical, and infrared using customizable absorption-line lists; (IV) trace simulated physical structures directly to spectral features; (v) approximate the presence of ion species absent from the simulation outputs; (VI) generate column density maps for any ion; and (vii) provide support for all major astrophysical hydrodynamical codes. trident was originally developed to aid in the interpretation of observations of the circumgalactic medium and intergalactic medium, but it remains a general tool applicable in other contexts.

Temporal and vertical variability in optical properties of New England shelf waters during late summer and spring

NASA Astrophysics Data System (ADS)

Sosik, Heidi M.; Green, Rebecca E.; Pegau, W. Scott; Roesler, Collin S.

2001-05-01

Relationships between optical and physical properties were examined on the basis of intensive sampling at a site on the New England continental shelf during late summer 1996 and spring 1997. During both seasons, particles were found to be the primary source of temporal and vertical variability in optical properties since light absorption by dissolved material, though significant in magnitude, was relatively constant. Within the particle pool, changes in phytoplankton were responsible for much of the observed optical variability. Physical processes associated with characteristic seasonal patterns in stratification and mixing contributed to optical variability mostly through effects on phytoplankton. An exception to this generalization occurred during summer as the passage of a hurricane led to a breakdown in stratification and substantial resuspension of nonphytoplankton particulate material. Prior to the hurricane, conditions in summer were highly stratified with subsurface maxima in absorption and scattering coefficients. In spring, stratification was much weaker but increased over the sampling period, and a modest phytoplankton bloom caused surface layer maxima in absorption and scattering coefficients. These seasonal differences in the vertical distribution of inherent optical properties were evident in surface reflectance spectra, which were elevated and shifted toward blue wavelengths in the summer. Some seasonal differences in optical properties, including reflectance spectra, suggest that a significant shift toward a smaller particle size distribution occurred in summer. Shorter timescale optical variability was consistent with a variety of influences including episodic events such as the hurricane, physical processes associated with shelfbreak frontal dynamics, biological processes such as phytoplankton growth, and horizontal patchiness combined with water mass advection.

Infrared radiative energy transfer in gaseous systems

NASA Technical Reports Server (NTRS)

Tiwari, Surendra N.

1991-01-01

Analyses and numerical procedures are presented to investigate the radiative interactions in various energy transfer processes in gaseous systems. Both gray and non-gray radiative formulations for absorption and emission by molecular gases are presented. The gray gas formulations are based on the Planck mean absorption coefficient and the non-gray formulations are based on the wide band model correlations for molecular absorption. Various relations for the radiative flux and divergence of radiative flux are developed. These are useful for different flow conditions and physical problems. Specific plans for obtaining extensive results for different cases are presented. The procedure developed was applied to several realistic problems. Results of selected studies are presented.

Application of Terahertz Attenuated Total Reflection Spectroscopy to Detect Changes in the Physical Properties of Lactose during the Lubrication Process Required for Drug Formulation.

PubMed

Dohi, Masafumi; Momose, Wataru; Yamashita, Kazunari; Hakomori, Tadashi; Sato, Shusaku; Noguchi, Shuji; Terada, Katsuhide

2017-02-01

Manufacturing the solid dosage form of an orally administered drug requires lubrication to enhance manufacturability, ensuring that critical quality attributes such as disintegration and dissolution of the drug product are maintained during manufacture. Here, to evaluate lubrication performance during manufacture, we used terahertz attenuated total reflection (THz-ATR) spectroscopy to detect differences in the physical characteristics of the lubricated powder. We applied a simple formulation prepared by blending granulated lactose as filler with magnesium stearate as lubricant. A flat tablet was prepared using the lubricated powder to acquire sharp THz-ATR absorption peaks of the samples. First, we investigated the effects of lubricant concentration and compression pressure on preparation of the tablet and then determined the effect of the pressure applied to samples in contact with the ATR prism on sample absorption amplitude. We focused on the differences in the magnitudes of spectra at the lactose-specific frequency. Second, we conducted the dynamic lubrication process using a 120-L mixer to investigate differences in the magnitudes of absorption corresponding to the lactose-specific frequency during lubrication. In both studies, enriching the lubricated powder with a higher concentration of magnesium stearate or prolonging blending time correlated with higher magnitudes of spectra at the lactose-specific frequency. Further, in the dynamic lubrication study, the wettability and disintegration time of the tablets were compared with the absorption spectra amplitudes at the lactose-specific frequency. We conclude that THz-ATR spectroscopy is useful for detecting differences in densities caused by a change in the physical properties of lactose during lubrication.

Measurement of laser absorptivity for operating parameters characteristic of laser drilling regime

NASA Astrophysics Data System (ADS)

Schneider, M.; Berthe, L.; Fabbro, R.; Muller, M.

2008-08-01

Laser drilling in the percussion regime is commonly used in the aircraft industry to drill sub-millimetre holes in metallic targets. Characteristic laser intensities in the range of 10 MW cm-2 are typically employed for drilling metallic targets. With these intensities the temperature of the irradiated matter is above the vaporization temperature and the drilling process is led by hydrodynamic effects. Although the main physical processes involved are identified, this process is not correctly understood or completely controlled. A major characteristic coefficient of laser-matter interaction for this regime, which is the absorptivity of the laser on the irradiated surface, is still unknown, because of the perturbing effects due to laser beam geometrical trapping inside the drilled hole. So, by using time resolved experiments, this study deals with the direct measurement of the variation of the intrinsic absorption of aluminium, nickel and steel materials, as a function of the incident laser intensity up to 20 MW cm-2. We observe that for this incident intensity, the absorptivity can reach up to 80%. This very high and unexpected value is discussed by considering the microscopic behaviour of the heated matter near the vapour-liquid interface that undergoes possible Rayleigh-Taylor instability or volume absorption.

Gas trace detection with cavity enhanced absorption spectroscopy: a review of its process in the field

NASA Astrophysics Data System (ADS)

Liu, Siqi; Luo, Zhifu; Tan, Zhongqi; Long, Xingwu

2016-11-01

Cavity-enhanced absorption spectroscopy (CEAS) is a technology in which the intracavity absorption is deduced from the intensity of light transmitted by the high finesse optical cavity. Then the samples' parameters, such as their species, concentration and absorption cross section, would be detection. It was first proposed and demonstrated by Engeln R. [1] and O'Keefe[2] in 1998. This technology has extraordinary detection sensitivity, high resolution and good practicability, so it is used in many fields , such as clinical medicine, gas detection and basic physics research. In this paper, we focus on the use of gas trace detection, including the advance of CEAS over the past twenty years, the newest research progresses, and the prediction of this technology's development direction in the future.

Changes in water absorptivity of slag based cement mortars exposed to sulphur-oxidising A. thiooxidans bacteria

NASA Astrophysics Data System (ADS)

Estokova, A.; Smolakova, M.; Luptakova, A.; Strigac, J.

2017-10-01

Water absorptivity is heavily influenced by the volume and connectivity of pores in the pore network of cement composites and has been used as an important parameter for quantifying their durability. To improve the durability and permeability of mortars, various mineral admixtures such as furnace slag, silica fume or fly ash are added into the mortar and concrete mixtures. These admixtures provide numerous important advantages such as corrosion control, improvement of mechanical and physical properties and better workability. This study investigated the changes in absorptivity of cement mortars with different amounts of mineral admixture, represented by granulated blast furnace slag, under aggressive bacterial influence. The water absorptivity of mortars specimens exposed to sulphur-oxidising bacteria A. thiooxidans for the period of 3 and 6 months has changed due to bio-corrosion-based degradation process. The differences in water absorptivity in dependence on the mortars composition have been observed.

The imaging and modelling of the physical processes involved in digestion and absorption.

PubMed

Schulze, K S

2015-02-01

The mechanical activity of the gastro-intestinal tract serves to store, propel and digest food. Contractions disperse particles and transform solids and secretions into the two-phase slurry called chyme; movements of the intestine deliver nutrients to mucosal sites of absorption, and from the submucosa into the lymphatic and portal venous circulation. Colonic motor activity helps to extract fluid and electrolytes from chyme and to compound and compact luminal debris into faeces for elimination. We outline how dynamic imaging by ultrasound and magnetic resonance can demonstrate intestinal flow processes critical to digestion like mixing, dilution, swelling, dispersion and elution. Computational fluid mechanics enables a numerical rendition of the forces promoting digestion: pressure and flow fields, the shear stresses dispersing particles or the effectiveness of bolus mixing can be calculated. These technologies provide new insights into the mechanical processes that promote digestion and absorption. © 2014 This article is a U.S. Government work and is in the public domain in the USA.

Surface Treatment on Physical Properties and Biocompatibility of Orthodontic Power Chains

PubMed Central

Cheng, H. C.; Chen, M. S.; Peng, B. Y.; Lin, W. T.; Wang, Y. H.

2017-01-01

The conventional orthodontic power chain, often composed of polymer materials, has drawbacks such as a reduction of elasticity owing to water absorption as well as surface discoloration and staining resulting from food or beverages consumed by the patient. The goal of this study was to develop a surface treatment (nanoimprinting) for orthodontic power chains and to alleviate their shortcomings. A concave template (anodic alumina) was manufactured by anodization process using pure aluminum substrate by employing the nanoimprinting process. Convex nanopillars were fabricated on the surface of orthodontic power chains, resulting in surface treatment. Distinct parameters of the nanoimprinting process (e.g., imprinting temperature, imprinting pressure, imprinting time, and demolding temperature) were used to fabricate nanopillars on the surface of orthodontic power chains. The results of this study showed that the contact angle of the power chains became larger after surface treatment. In addition, the power chains changed from hydrophilic to hydrophobic. The power chain before surface treatment without water absorption had a water absorption rate of approximately 4%, whereas a modified chain had a water absorption rate of approximately 2%–4%. Furthermore, the color adhesion of the orthodontic power chains after surface modification was less than that before surface modification. PMID:28540299

Moving beyond the limits of mass transport in liquid absorbent microfilms through the implementation of surface-induced vortices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bigham, S; Yu, DZ; Chugh, D

2014-02-01

The slow diffusion of an absorbate molecule into an absorbent often makes the absorption process a rate-limiting step in many applications. In cases involving an absorbate with a high heat of phase change, such as water absorption into a LiBr (lithium bromide) solution, the absorption rate is further slowed due to significant heating of the absorbent. Recently, it has been demonstrated that constraining a LiBr solution film by a hydrophobic porous structure enables manipulation of the solution flow thermohydraulic characteristics. Here, it is shown that mass transport mode in a constrained laminar solution flow can be changed from diffusive tomore » advective. This change in mode is accomplished through stretching and folding the laminar streamlines within the solution film via the implementation of micro-scale features on the flow channel surface. The process induces vortices within the solution film, which continuously bring concentrated solution from the bottom and middle of the solution channel to its interface with the vapor phase, thus leading to a significant enhancement in the absorption rate. The detailed physics of the involved transport processes is elucidated using the LBM (Lattice Boltzmann Method). Published by Elsevier Ltd.« less

Observation of Reverse Saturable Absorption of an X-ray Laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cho, B. I.; Cho, M. S.; Kim, M.

A nonlinear absorber in which the excited state absorption is larger than the ground state can undergo a process called reverse saturable absorption. It is a well-known phenomenon in laser physics in the optical regime, but is more difficult to generate in the x-ray regime, where fast nonradiative core electron transitions typically dominate the population kinetics during light matter interactions. Here, we report the first observation of decreasing x-ray transmission in a solid target pumped by intense x-ray free electron laser pulses. The measurement has been made below the K-absorption edge of aluminum, and the x-ray intensity ranges are 10more » 16 –10 17 W=cm 2. It has been confirmed by collisional radiative population kinetic calculations, underscoring the fast spectral modulation of the x-ray pulses and charge states relevant to the absorption and transmission of x-ray photons. The processes shown through detailed simulations are consistent with reverse saturable absorption, which would be the first observation of this phenomena in the x-ray regime. These light matter interactions provide a unique opportunity to investigate optical transport properties in the extreme state of matters, as well as affording the potential to regulate ultrafast x-ray freeelectron laser pulses.« less

Observation of Reverse Saturable Absorption of an X-ray Laser

DOE PAGES

Cho, B. I.; Cho, M. S.; Kim, M.; ...

2017-08-16

A nonlinear absorber in which the excited state absorption is larger than the ground state can undergo a process called reverse saturable absorption. It is a well-known phenomenon in laser physics in the optical regime, but is more difficult to generate in the x-ray regime, where fast nonradiative core electron transitions typically dominate the population kinetics during light matter interactions. Here, we report the first observation of decreasing x-ray transmission in a solid target pumped by intense x-ray free electron laser pulses. The measurement has been made below the K-absorption edge of aluminum, and the x-ray intensity ranges are 10more » 16 –10 17 W=cm 2. It has been confirmed by collisional radiative population kinetic calculations, underscoring the fast spectral modulation of the x-ray pulses and charge states relevant to the absorption and transmission of x-ray photons. The processes shown through detailed simulations are consistent with reverse saturable absorption, which would be the first observation of this phenomena in the x-ray regime. These light matter interactions provide a unique opportunity to investigate optical transport properties in the extreme state of matters, as well as affording the potential to regulate ultrafast x-ray freeelectron laser pulses.« less

Vertical electro-absorption modulator design and its integration in a VCSEL

NASA Astrophysics Data System (ADS)

Marigo-Lombart, L.; Calvez, S.; Arnoult, A.; Thienpont, H.; Almuneau, G.; Panajotov, K.

2018-04-01

Electro-absorption modulators, either embedded in CMOS technology or integrated with a semiconductor laser, are of high interest for many applications such as optical communications, signal processing and 3D imaging. Recently, the integration of a surface-normal electro-absorption modulator into a vertical-cavity surface-emitting laser has been considered. In this paper we implement a simple quantum well electro-absorption model and design and optimize an asymmetric Fabry-Pérot semiconductor modulator while considering all physical properties within figures of merit. We also extend this model to account for the impact of temperature on the different parameters involved in the calculation of the absorption, such as refractive indices and exciton transition broadening. Two types of vertical modulator structures have been fabricated and experimentally characterized by reflectivity and photocurrent measurements demonstrating a very good agreement with our model. Finally, preliminary results of an electro-absorption modulator vertically integrated with a vertical-cavity surface-emitting laser device are presented, showing good modulation performances required for high speed communications.

Trident: A Universal Tool for Generating Synthetic Absorption Spectra from Astrophysical Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hummels, Cameron B.; Smith, Britton D.; Silvia, Devin W.

Hydrodynamical simulations are increasingly able to accurately model physical systems on stellar, galactic, and cosmological scales; however, the utility of these simulations is often limited by our ability to directly compare them with the data sets produced by observers: spectra, photometry, etc. To address this problem, we have created trident, a Python-based open-source tool for post-processing hydrodynamical simulations to produce synthetic absorption spectra and related data. trident can (i) create absorption-line spectra for any trajectory through a simulated data set mimicking both background quasar and down-the-barrel configurations; (ii) reproduce the spectral characteristics of common instruments like the Cosmic Origins Spectrograph;more » (iii) operate across the ultraviolet, optical, and infrared using customizable absorption-line lists; (iv) trace simulated physical structures directly to spectral features; (v) approximate the presence of ion species absent from the simulation outputs; (vi) generate column density maps for any ion; and (vii) provide support for all major astrophysical hydrodynamical codes. trident was originally developed to aid in the interpretation of observations of the circumgalactic medium and intergalactic medium, but it remains a general tool applicable in other contexts.« less

Semiconductor superlattice photodetectors

NASA Technical Reports Server (NTRS)

Chuang, S. L.; Hess, K.; Coleman, J. J.; Leburton, J. P.

1986-01-01

Superlattice photodetectors were investigated. A few major physical processes in the quantum-well heterostructures related to the photon detection and electron conduction mechanisms, the field effect on the wave functions and the energy levels of the electrons, and the optical absorption with and without the photon assistance were studied.

Fabrication process and electromagnetic wave absorption characterization of a CNT/Ni/epoxy nanocomposite.

PubMed

Ryu, Seongwoo; Mo, Chan Bin; Lee, Haeshin; Hong, Soon Hyung

2013-11-01

Since carbon nanotube (CNT) was first discovered in 1991, it has been considered as a viable type of conductive filler for electromagnetic wave absorption materials in the GHz range. In this paper, pearl-necklace-structure CNT/Ni nano-powders were fabricated by a polyol process as conductive fillers. Compared to synthesized CNT, pearl-necklace Ni-decorated CNT increased the electrical conductivity by an order of 1 due to the enhancement of the Ni-conductive network. Moreover, the decorated Ni particles prevented the agglomeration of CNTs by counterbalancing the Van der Walls interaction between the CNTs. A CNT/Ni nanocomposite showed a homogeneous dispersion in an epoxy-based matrix. This enhanced physical morphology and electrical properties lead to an increase in the loss tangent and reflection loss in the CNT/Ni/Epoxy nanocomposite compared to these characteristics of a CNT/Epoxy nanocomposite in range of 8-12 GHz. The electromagnetic wave absorption properties of CNT/Ni/epoxy nanocomposites will provide enormous opportunities for electronic applications where lightweight EMI shielding or electro-magnetic wave absorption properties are necessary.

Chemical physics of molecules and continuous channel electron multipliers

NASA Technical Reports Server (NTRS)

Judge, D. L.

1971-01-01

The A approaches X, B approaches X and B approaches A bands of CO(+) have been excited using monochromatic photons and the band intensities measured. Using such data the variations of the electronic transition moments for these above emission bands as well as for the absorption bands have been determined. Further, the specific cross sections for the absorption processes have been determined by measuring the total emission intensity in the band system through which the upper state decays. The band intensity measurements and the derived results are presented.

Gastric digestion of raw and roasted almonds in vivo

USDA-ARS?s Scientific Manuscript database

Almonds are an important dietary source of lipids, protein, and alpha-tocopherol. It has been demonstrated that the physical form of almond kernels will affect their digestion and absorption, but the influence of thermal processes on the digestion of almonds has received little attention. The obje...

Numerical and Probabilistic Analysis of Asteroid and Comet Impact Hazard Mitigation

DTIC Science & Technology

2010-09-01

object on Jupiter are reminders and warning signals that we should take seriously. The extinction of the dinosaurs has been attributed to the impact of a...experimentally determined absorption patterns. These energy deposition processes are independent, so a piecemeal approach is physically reasonable . We

Characterization and evaluation in vivo of baicalin-nanocrystals prepared by an ultrasonic-homogenization-fluid bed drying method.

PubMed

Shi-Ying, Jin; Jin, Han; Shi-Xiao, Jin; Qing-Yuan, Lv; Jin-Xia, Bai; Chen, Hong-Ge; Rui-Sheng, Li; Wei, Wu; Hai-Long, Yuan

2014-01-01

To improve the absorption and bioavailability of baicalin using a nanocrystal (or nanosuspension) drug delivery system. A tandem, ultrasonic-homogenization-fluid bed drying technology was applied to prepare baicalin-nanocrystal dried powders, and the physicochemical properties of baicalin-nanocrystals were characterized by scanning electron microscopy, photon correlation spectroscopy, powder X-ray diffraction, physical stability, and solubility experiments. Furthermore, in situ intestine single-pass perfusion experiments and pharmacokinetics in rats were performed to make a comparison between the microcrystals of baicalin and pure baicalin in their absorption properties and bioavailability in vivo. The mean particle size of baicalin-nanocrystals was 236 nm, with a polydispersity index of 0.173, and a zeta potential value of -34.8 mV, which provided a guarantee for the stability of the reconstituted nanosuspension. X-Ray diffraction results indicated that the crystallinity of baicalin was decreased through the ultrasonic-homogenization process. Physical stability experiments showed that the prepared baicalin-nanocrystals were sufficiently stable. It was shown that the solubility of baicalin in the form of nanocrystals, at 495 μg·mL(-1), was much higher than the baicalin-microcrystals and the physical mixture (135 and 86.4 μg·mL(-1), respectively). In situ intestine perfusion experiments demonstrated a clear advantage in the dissolution and absorption characteristics for baicalin-nanocrystals compared to the other formulations. In addition, after oral administration to rats, the particle size decrease from the micron to nanometer range exhibited much higher in vivo bioavailability (with the AUC(0-t) value of 206.96 ± 21.23 and 127.95 ± 14.41 mg·L(-1)·h(-1), respectively). The nanocrystal drug delivery system using an ultrasonic-homogenization-fluid bed drying process is able to improve the absorption and in vivo bioavailability of baicalin, compared with pure baicalin coarse powder and micronized baicalin. Copyright © 2014 China Pharmaceutical University. Published by Elsevier B.V. All rights reserved.

Physical properties of extruded products from three Mexican common beans (Phaseolus vulgaris L.) cultivars.

PubMed

Rocha-Guzman, N E; Gallegos-Infante, J A; Gonzalez-Laredo, R F; Bello-Perez, A; Delgado-Licon, E; Ochoa-Martinez, A; Prado-Ortiz, M J

2008-09-01

The physical properties of extruded products from three Mexican common bean cultivars were investigated. Common bean cultivars Flor de Mayo, Pinto Villa and Bayo Victoria from the same harvesting season (2006) were used in this work. Beans were milled and the flour was hydrated to 24, 26 and 28 g of water/100 g of dry weight. Two temperatures, 130 degrees C and 165 degrees C at the end of the extruder barrel without die, were experimented. Common bean flour extrudates were evaluated for water absorption index (WAI), water absorption capacity (WAC), oil absorption capacity (OAC), and emulsifying capacity (EC). Flor de Mayo extrudates showed the highest WAC and WAI values. Thus starch from Flor de Mayo beans showed minor restricted water availability. In all cases, the OAC of extruded products was lower than the crude bean flour. The EC for Bayo Victoria flour increased as a consequence of the extrusion process. The EC for Flor de Mayo was higher at lower temperature and lower moisture content than Pinto Villa and Bayo Victoria beans. EC behavior of Pinto Villa was similar to Bayo cultivar. These results indicate that it is possible to produce new extruded products with good physical properties from these common bean cultivars.

Continuous Energy Photon Transport Implementation in MCATK

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adams, Terry R.; Trahan, Travis John; Sweezy, Jeremy Ed

2016-10-31

The Monte Carlo Application ToolKit (MCATK) code development team has implemented Monte Carlo photon transport into the MCATK software suite. The current particle transport capabilities in MCATK, which process the tracking and collision physics, have been extended to enable tracking of photons using the same continuous energy approximation. We describe the four photoatomic processes implemented, which are coherent scattering, incoherent scattering, pair-production, and photoelectric absorption. The accompanying background, implementation, and verification of these processes will be presented.

The Magellan Evolution of Galaxies Spectroscopic and Ultraviolet Reference Atlas (MegaSaura). II. Stacked Spectra

NASA Astrophysics Data System (ADS)

Rigby, J. R.; Bayliss, M. B.; Chisholm, J.; Bordoloi, R.; Sharon, K.; Gladders, M. D.; Johnson, T.; Paterno-Mahler, R.; Wuyts, E.; Dahle, H.; Acharyya, A.

2018-01-01

We stack the rest-frame ultraviolet spectra of N = 14 highly magnified gravitationally lensed galaxies at redshifts 1.6< z< 3.6. The resulting new composite spans 900< {λ }{rest}< 3000 Å, with a peak signal-to-noise ratio (S/N) of 103 per spectral resolution element (∼100 km s‑1). It is the highest S/N, highest spectral resolution composite spectrum of z ∼ 2–3 galaxies yet published. The composite reveals numerous weak nebular emission lines and stellar photospheric absorption lines that can serve as new physical diagnostics, particularly at high redshift with the James Webb Space Telescope (JWST). We report equivalent widths to aid in proposing for and interpreting JWST spectra. We examine the velocity profiles of strong absorption features in the composite, and in a matched composite of z∼ 0 COS/HST galaxy spectra. We find remarkable similarity in the velocity profiles at z∼ 0 and z∼ 2, suggesting that similar physical processes control the outflows across cosmic time. While the maximum outflow velocity depends strongly on ionization potential, the absorption-weighted mean velocity does not. As such, the bulk of the high-ionization absorption traces the low-ionization gas, with an additional blueshifted absorption tail extending to at least ‑2000 km s‑1. We interpret this tail as arising from the stellar wind and photospheres of massive stars. Starburst99 models are able to replicate this high-velocity absorption tail. However, these theoretical models poorly reproduce several of the photospheric absorption features, indicating that improvements are needed to match observational constraints on the massive stellar content of star-forming galaxies at z∼ 2. We publicly release our composite spectra.

Frost grain size metamorphism - Implications for remote sensing of planetary surfaces

NASA Technical Reports Server (NTRS)

Clark, R. N.; Fanale, F. P.; Zent, A. P.

1983-01-01

The effective grain size of a material on a planetary surface affects the strength of absorption features observed in the reflectance of a particulate surface. In the case of a planetary surface containing volatile ices, the absorption characteristics can change in connection with processes leading to a change in the grain size of the material. The present investigation is concerned with an evaluation regarding the occurrence of such processes and the implications for remote sensing applications. It is found that quantitative modeling of the kinetics of grain growth and destruction by thermal and nonthermal processes can provide a means to reconcile apparent optical paths in the volatile portions of planetary surfaces with the physical history of those surfaces. Attention is also given to conditions in the case of the Pluto/Triton system, Uranus and Saturnian satellites, and the Galilean system.

Canopy structural complexity influences forest canopy reflectance: linking terrestrial lidar with Landsat observations

NASA Astrophysics Data System (ADS)

Hardiman, B. S.; Atkins, J.; Dahlin, K.; Fahey, R. T.; Gough, C. M.

2016-12-01

Canopy physical structure - leaf quantity and arrangement - strongly affects light interception and distribution. As such, canopy physical structure is a key driver of forest carbon (C) dynamics. Terrestrial lidar systems (TLS) provide spatially explicit, quantitative characterizations of canopy physical structure at scales commensurate with plot-scale C cycling processes. As an example, previous TLS-based studies established that light use efficiency is positively correlated with canopy physical structure, influencing the trajectory of net primary production throughout forest development. Linking TLS measurements of canopy structure to multispectral satellite observations of forest canopies may enable scaling of ecosystem C cycling processes from leaves to continents. We will report on our study relating a suite of canopy structural metrics to well-established remotely sensed measurements (NDVI, EVI, albedo, tasseled cap indices, etc.) which are indicative of important forest characteristics (leaf area, canopy nitrogen, light interception, etc.). We used Landsat data, which provides observations at 30m resolution, a scale comparable to that of TLS. TLS data were acquired during 2009-2016 from forest sites throughout Eastern North America, comprised primarily of NEON and Ameriflux sites. Canopy physical structure data were compared with contemporaneous growing-season Landsat data. Metrics of canopy physical structure are expected to covary with forest composition and dominant PFT, likely influencing interaction strength between TLS and Landsat canopy metrics. More structurally complex canopies (those with more heterogeneous distributions of leaf area) are expected to have lower albedo, suggesting greater canopy light absorption (higher fAPAR) than simpler canopies. We expect that vegetation indices (NDVI, EVI) will increase with TLS metrics of spatial heterogeneity, and not simply quantity, of leaves, supporting our hypothesis that canopy light absorption is dependent on both leaf quantity and arrangement. Relating satellite observations of canopy properties to TLS metrics of canopy physical structure represents an important advance for modelling canopy energy balance and forest C cycling processes at large spatial scales.

Atomistic Model of Physical Ageing in Se-rich As-Se Glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Golovchak,R.; Shpotyuk, O.; Kozdras, A.

2007-01-01

Thermal, optical, X-ray excited and magnetic methods were used to develop a microstructural model of physical ageing in Se-rich glasses. The glass composition As10Se90, possessing a typical cross-linked chain structure, was chosen as a model object for the investigations. The effect of physical ageing in this glass was revealed by differential scanning calorimetry, whereas the corresponding changes in its atomic arrangement were studied by extended X-ray absorption fine structure, Raman and solid-state 77Se nuclear magnetic resonance spectroscopy. Straightening-shrinkage processes are shown to be responsible for the physical ageing in this Se-rich As-Se glass.

Effects of processing moisture on the physical properties and in vitro digestibility of starch and protein in extruded brown rice and pinto bean composite flours.

PubMed

Sumargo, Franklin; Gulati, Paridhi; Weier, Steven A; Clarke, Jennifer; Rose, Devin J

2016-11-15

The influence of pinto bean flour and processing moisture on the physical properties and in vitro digestibility of rice-bean extrudates has been investigated. Brown rice: pinto bean flour (0%, 15%, 30%, and 45% bean flour) were extruded under 5 moisture conditions (17.2%, 18.1%, 18.3%, 19.5%, and 20.1%). Physical properties [bulk density, unit density, radial expansion, axial expansion, overall expansion, specific volume, hardness, color, water solubility index, and water absorption index] and in vitro starch and protein digestibilities were determined. Increasing bean flour and processing moisture increased density and hardness while decreasing expansion. Rapidly digestible starch decreased and resistant starch increased as bean substitution and processing moisture increased. In vitro protein digestibility increased with increasing bean flour or with decreasing processing moisture. Incorporating bean flour into extruded snacks can negatively affect physical attributes (hardness, density, and expansion) while positively affecting in vitro starch (decrease) and protein (increase) digestibilities. Copyright © 2016 Elsevier Ltd. All rights reserved.

Physical quality characteristics of the microwave-dried breadfruit powders due to different processing conditions

NASA Astrophysics Data System (ADS)

Taruna, I.; Hakim, A. L.; Sutarsi

2018-03-01

Production of breadfruit powder has been an option to make easy its uses in various food processing. Accordingly, there is a need recently to apply advanced drying method, i.e. microwave drying, for improving quality since conventional methods produced highly variable product quality and required longer process. The present work was aimed to study the effect of microwave power and grinding time on physical quality of breadfruit powders. The experiment was done initially by drying breadfruit slices in a microwave dryer at power level of 420, 540, and 720 W and then grinding for 3, 5, and 7 min to get powdery product of less than 80 mesh. The physical quality of breadfruit powders were measured in terms of fineness modulus (FM), average particle size (D), whiteness (WI), total color difference (ΔE), water absorption (Wa), oil absorption (La), bulk density (ρb) and consistency gel (Gc). The results showed that physical quality of powders and its ranged-values included the FM (2.08-2.62), D (0.44-0.68 mm), WI (75.2-77.9), ΔE (7.4-10.5), Wa (5.5-6.2 ml/g), La (0.7-0.9 ml/g), ρb (0.62-0.70 g/cm3) and Gc (41.3-46.8 mm). The experiment revealed that variation of microwave power and grinding time affected significantly the quality of the breadfruit powders. However, microwave power was more dominant factor to affect quality of breadfruit powder in comparison to the grinding time.

Effects of rain and fog on the Shuttle Ku-band microwave scanning beam landing system range and accuracy performance

NASA Technical Reports Server (NTRS)

Butler, D.

1981-01-01

The microwave Scanning Beam Landing System's (MSBLS) performance in fog and rain was studied. The fog and rain effects on the Shuttle Ku-band system were determined. Specifically, microwave attenuation, beam distortion, and coordinate errors resulting from operation of the MSBLS in poor weather conditions were evaluated. The main physical processes giving rise to microwave attenuation were found to be absorption and scattering by water droplets. The general theory of scattering and absorption used is discussed and a listing of applicable computer programs is provided.

Au NPs immersed in sol-gel matrix: nonlinear optical characterization

NASA Astrophysics Data System (ADS)

Aguilera-Zavala, Angélica; Trejo-Durán, Mónica; Ortiz-Jiménez, Orlando; Cornejo-Monroy, Delfino; Severiano-Carrillo, Israel; Alvarado-Méndez, Edgar

2016-09-01

Physical and optical characterization of thin films doped with Au Nanoparticles onto a silica substrate is presented. Films were prepared through sol-gel process, by using Au nanoparticles immersed in lipoic acid as dopant by means of hydrolysis and acid catalyzed reaction of tetraethyl-orthosilicate. The surface was characterized by SEM and AFM microscopies. Z-scan technique was used to measure nonlinear optical properties as nonlinear absorption and refraction indexes, using two different wavelengths. At 633 nm it was possible to observe nonlinear absorption only but at 514 nm both nonlinear properties were observed.

Evaluation of physics-based numerical modelling for diverse design architecture of perovskite solar cells

NASA Astrophysics Data System (ADS)

Mishra, A. K.; Catalan, Jorge; Camacho, Diana; Martinez, Miguel; Hodges, D.

2017-08-01

Solution processed organic-inorganic metal halide perovskite based solar cells are emerging as a new cost effective photovoltaic technology. In the context of increasing the power conversion efficiency (PCE) and sustainability of perovskite solar cells (PSC) devices, we comprehensively analyzed a physics-based numerical modelling for doped and un-doped PSC devices. Our analytics emphasized the role of different charge carrier layers from the view point of interfacial adhesion and its influence on charge extraction rate and charge recombination mechanism. Morphological and charge transport properties of perovskite thin film as a function of device architecture are also considered to investigate the photovoltaic properties of PSC. We observed that photocurrent is dominantly influenced by interfacial recombination process and photovoltage has functional relationship with defect density of perovskite absorption layer. A novel contour mapping method to understand the characteristics of current density-voltage (J-V) curves for each device as a function of perovskite layer thickness provide an important insight about the distribution spectrum of photovoltaic properties. Functional relationship of device efficiency and fill factor with absorption layer thickness are also discussed.

The physics of heterodyne detection in the far-infrared: Transition from electric-field to photon-absorption detection in a simple system

NASA Technical Reports Server (NTRS)

Teich, M. C.

1980-01-01

The history of heterodyne detection is reviewed from the radiowave to the optical regions of the electromagnetic spectrum with emphasion the submillimeter/far infrared. The transition from electric field to photon absorption detection in a simple system is investigated. The response of an isolated two level detector to a coherent source of incident radiation is calculated for both heterodyne and video detection. When the processes of photon absorption and photon emission cannot be distinguished, the relative detected power at double- and sum-frequencies is found to be multiplied by a coefficient, which is less than or equal to unity, and which depends on the incident photon energy and on the effective temperature of the system.

Effects of Perforation on Rigid PU Foam Plates: Acoustic and Mechanical Properties

PubMed Central

Lin, Jia-Horng; Chuang, Yu-Chun; Li, Ting-Ting; Huang, Chen-Hung; Huang, Chien-Lin; Chen, Yueh-Sheng; Lou, Ching-Wen

2016-01-01

Factories today are equipped with diverse mechanical equipment in response to rapid technological and industrial developments. Industrial areas located near residential neighborhoods cause massive environmental problems. In particular, noise pollution results in physical and psychological discomfort, and is a seen as invisible and inevitable problem. Thus, noise reduction is a critical and urgent matter. In this study, rigid polyurethane (PU) foam plates undergo perforation using a tapping machine. The mechanical and acoustic properties of these perforated plates as related to perforation rate and perforation depth are evaluated in terms of compression strength, drop-weight impact strength, and sound absorption coefficient. Experimental results indicate that applying the perforation process endows the rigid PU foaming plates with greater load absorption and better sound absorption at medium and high frequencies. PMID:28774119

Effects of Perforation on Rigid PU Foam Plates: Acoustic and Mechanical Properties.

PubMed

Lin, Jia-Horng; Chuang, Yu-Chun; Li, Ting-Ting; Huang, Chen-Hung; Huang, Chien-Lin; Chen, Yueh-Sheng; Lou, Ching-Wen

2016-12-09

Factories today are equipped with diverse mechanical equipment in response to rapid technological and industrial developments. Industrial areas located near residential neighborhoods cause massive environmental problems. In particular, noise pollution results in physical and psychological discomfort, and is a seen as invisible and inevitable problem. Thus, noise reduction is a critical and urgent matter. In this study, rigid polyurethane (PU) foam plates undergo perforation using a tapping machine. The mechanical and acoustic properties of these perforated plates as related to perforation rate and perforation depth are evaluated in terms of compression strength, drop-weight impact strength, and sound absorption coefficient. Experimental results indicate that applying the perforation process endows the rigid PU foaming plates with greater load absorption and better sound absorption at medium and high frequencies.

Aging behavior of near atmospheric N2 ambient sputtered/patterned Au IR absorber thin films

NASA Astrophysics Data System (ADS)

Gaur, Surender P.; Kothari, Prateek; Rangra, Kamaljit; Kumar, Dinesh

2018-03-01

Near atmospheric N2 ambient sputtered Au thin films exhibit significant spectral absorptivity over medium to long wave infrared radiations. Thin films were found adequately robust for micropatterning using conventional photolithography and metal lift off processes. Since long term spectral absorptivity is major practical concern for Au blacks, this paper reports on aging behavior of near atmospheric Ar and Ar + N2 (1:1) ambient sputtered infrared absorber Au thin films. Comparative analysis on electrical, morphological and spectral absorption behavior of twenty-five weeks room temperature/vacuum aged Au infrared absorber thin films is performed. The Ar and Ar + N2 ambient sputtered Au thing films have shown anticipated consistency in their physical, electrical and spectral properties regardless the long term aging in this work.

Whistlers, Helicons, Lower Hybrid Waves: the Physics of RF Wave Absorption Without Cyclotron Resonances

NASA Astrophysics Data System (ADS)

Pinsker, R. I.

2014-10-01

In hot magnetized plasmas, two types of linear collisionless absorption processes are used to heat and drive noninductive current: absorption at ion or electron cyclotron resonances and their harmonics, and absorption by Landau damping and the transit-time-magnetic-pumping (TTMP) interactions. This tutorial discusses the latter process, i.e., parallel interactions between rf waves and electrons in which cyclotron resonance is not involved. Electron damping by the parallel interactions can be important in the ICRF, particularly in the higher harmonic region where competing ion cyclotron damping is weak, as well as in the Lower Hybrid Range of Frequencies (LHRF), which is in the neighborhood of the geometric mean of the ion and electron cyclotron frequencies. On the other hand, absorption by parallel processes is not significant in conventional ECRF schemes. Parallel interactions are especially important for the realization of high current drive efficiency with rf waves, and an application of particular recent interest is current drive with the whistler or helicon wave at high to very high (i.e., the LHRF) ion cyclotron harmonics. The scaling of absorption by parallel interactions with wave frequency is examined and the advantages and disadvantages of fast (helicons/whistlers) and slow (lower hybrid) waves in the LHRF in the context of reactor-grade tokamak plasmas are compared. In this frequency range, both wave modes can propagate in a significant fraction of the discharge volume; the ways in which the two waves can interact with each other are considered. The use of parallel interactions to heat and drive current in practice will be illustrated with examples from past experiments; also looking forward, this tutorial will provide an overview of potential applications in tokamak reactors. Supported by the US Department of Energy under DE-FC02-04ER54698.

Numerical Investigation of the Effect of Some Parameters on Temperature Field and Kerf Width in Laser Cutting Process

NASA Astrophysics Data System (ADS)

Kheloufi, Karim; Amara, El Hachemi

A transient numerical model is developed to study the temperature field and the kerf shape during laser cutting process. The Fresnel absorption model is used to handle the absorption of the incident wave by the surface of the liquid metal and the enthalpy-porosity technique is employed to account for the latent heat during melting and solidification of the material. The VOF method is used to track the evolution of the shape of the kerf. Physical phenomena occurring at the liquid/gas interface, including friction force and pressure force exerted by the gas jet and the heat absorbed by the surface, are incorporated into the governing equations as source terms. Temperature and velocity distribution, and kerf shape are investigated.

Climate Sensitivity to Realistic Solar Heating of Snow and Ice

NASA Astrophysics Data System (ADS)

Flanner, M.; Zender, C. S.

2004-12-01

Snow and ice-covered surfaces are highly reflective and play an integral role in the planetary radiation budget. However, GCMs typically prescribe snow reflection and absorption based on minimal knowledge of snow physical characteristics. We performed climate sensitivity simulations with the NCAR CCSM including a new physically-based multi-layer snow radiative transfer model. The model predicts the effects of vertically resolved heating, absorbing aerosol, and snowpack transparency on snowpack evolution and climate. These processes significantly reduce the model's near-infrared albedo bias over deep snowpacks. While the current CCSM implementation prescribes all solar radiative absorption to occur in the top 2 cm of snow, we estimate that about 65% occurs beneath this level. Accounting for the vertical distribution of snowpack heating and more realistic reflectance significantly alters snowpack depth, surface albedo, and surface air temperature over Northern Hemisphere regions. Implications for the strength of the ice-albedo feedback will be discussed.

Reduction of the capillary water absorption of foamed concrete by using the porous aggregate

NASA Astrophysics Data System (ADS)

Namsone, E.; Sahmenko, G.; Namsone, E.; Korjakins, A.

2017-10-01

The article reports on the research of reduction of the capillary water absorption of foamed concrete (FC) by using the porous aggregate such as the granules of expanded glass (EG) and the cenospheres (CS). The EG granular aggregate is produced by using recycled glass and blowing agents, melted down in high temperature. The unique structure of the EG granules is obtained where the air is kept closed inside the pellet. The use of the porous aggregate in the preparation process of the FC samples provides an opportunity to improve some physical and mechanical properties of the FC, classifying it as a product of high-performance. In this research the FC samples were produced by adding the EG granules and the CS. The capillary water absorption of hardened samples has been verified. The pore size distribution has been determined by microscope. It is a very important characteristic, specifically in the cold climate territories-where temperature often falls below zero degrees. It is necessary to prevent forming of the micro sized pores in the final structure of the material as it reduces its water absorption capacity. In addition, at a below zero temperature water inside these micro sized pores can increase them by expanding the stress on their walls during the freezing process. Research of the capillary water absorption kinetics can be practical for prevision of the FC durability.

Spectral parameters and Hamaker constants of silicon hydride compounds and organic solvents.

PubMed

Masuda, Takashi; Matsuki, Yasuo; Shimoda, Tatsuya

2009-12-15

Cyclopentasilane (CPS) and polydihydrosilane, which consist of hydrogen and silicon only, are unique materials that can be used to produce intrinsic silicon film in a liquid process, such as spin coating or an ink-jet method. Wettability and solubility of general organic solvents including the above can be estimated by Hamaker constants, which are calculated according to the Lifshitz theory. In order to calculate a Hamaker constant by the simple spectral method (SSM), it is necessary to obtain absorption frequency and function of oscillator strength in the ultraviolet region. In this report, these physical quantities were obtained by means of an optical method. As a result of examination of the relation between molecular structures and ultraviolet absorption frequencies, which were obtained from various liquid materials, it was concluded that ultraviolet absorption frequencies became smaller as electrons were delocalized. In particular, the absorption frequencies were found to be very small for CPS and polydihydrosilane due to sigma-conjugate of their electrons. The Hamaker constants of CPS and polydihydrosilane were successfully calculated based on the obtained absorption frequency and function of oscillator strength.

Research program in nuclear and solid state physics

NASA Technical Reports Server (NTRS)

Stronach, C. E.

1973-01-01

The spectra of prompt gamma rays emitted following nuclear pion absorption were studied to determine the states of excited daughter nuclei, and the branching ratios for these states. Studies discussed include the negative pion absorption of C-12, S-32, and N-14; and the positive pion absorption on 0-16. Abstracts of papers submitted to the conference of the American Physical Society are included.

Applying high-emittance and solar-absorptance coating to aluminum

NASA Technical Reports Server (NTRS)

Progar, D. J.

1973-01-01

Coated surface withstands space environment with negilgible change in radiation characteristics and physical properties. Process can be used with any porous substance, as long as pores are large enough to allow molecules of reacting solutions to enter and yet not so large as to allow nickel sulfide to be leached out of pores before sealing.

Exploring Drug Diffusion through a Membrane: A Physical Chemistry Experiment for Health and Life Sciences Undergraduate Students

ERIC Educational Resources Information Center

Ribeiro, Isabel A. C.; Faustino, Ce´lia M. C.; Guedes, Rita C.; Alfaia, Anto´nio J. I.; Ribeiro, Maria H. L.

2015-01-01

The transport of molecules across biological membranes are critical for most cellular processes. Membrane permeability is also a key determinant for drug absorption, distribution, and elimination. Diffusion, that is, the migration of matter down a concentration gradient, is a simple mechanism by which both endogenous and drug molecules can enter…

Parameterization of Photon Tunneling with Application to Ice Cloud Optical Properties at Terrestrial Wavelengths

NASA Astrophysics Data System (ADS)

Mitchell, D. L.

2006-12-01

Sometimes deep physical insights can be gained through the comparison of two theories of light scattering. Comparing van de Hulst's anomalous diffraction approximation (ADA) with Mie theory yielded insights on the behavior of the photon tunneling process that resulted in the modified anomalous diffraction approximation (MADA). (Tunneling is the process by which radiation just beyond a particle's physical cross-section may undergo large angle diffraction or absorption, contributing up to 40% of the absorption when wavelength and particle size are comparable.) Although this provided a means of parameterizing the tunneling process in terms of the real index of refraction and size parameter, it did not predict the efficiency of the tunneling process, where an efficiency of 100% is predicted for spheres by Mie theory. This tunneling efficiency, Tf, depends on particle shape and ranges from 0 to 1.0, with 1.0 corresponding to spheres. Similarly, by comparing absorption efficiencies predicted by the Finite Difference Time Domain Method (FDTD) with efficiencies predicted by MADA, Tf was determined for nine different ice particle shapes, including aggregates. This comparison confirmed that Tf is a strong function of ice crystal shape, including the aspect ratio when applicable. Tf was lowest (< 0.36) for aggregates and plates, and largest (> 0.9) for quasi- spherical shapes. A parameterization of Tf was developed in terms of (1) ice particle shape and (2) mean particle size regarding the large mode (D > 70 mm) of the ice particle size distribution. For the small mode, Tf is only a function of ice particle shape. When this Tf parameterization is used in MADA, absorption and extinction efficiency differences between MADA and FDTD are within 14% over the terrestrial wavelength range 3-100 mm for all size distributions and most crystal shapes likely to be found in cirrus clouds. Using hyperspectral radiances, it is demonstrated that Tf can be retrieved from ice clouds. Since Tf is a function of ice particle shape, this may provide a means of retrieving qualitative information on ice particle shape.

Quality Assessment of Physical and Organoleptic Instant Corn Rice on Scale-Up Process

NASA Astrophysics Data System (ADS)

Kumalasari, R.; Ekafitri, R.; Indrianti, N.

2017-12-01

Development of instant corn rice product has been successfully conducted on a laboratory scale. Corn has high carbohydrate content but low in fiber. The addition of fiber in instant corn rice, intended to improve the functioning of the product, and replace fiber loss during the process. Scale up process of Instant corn rice required to increase the production capacity. Scale up was the process to get identic output on a larger scale based on predetermined production scale. This study aimed to assess the changes and differences in the quality of instant corn rice during scale up. Instant corn rice scale up was done on production capacity 3 kg, 4 kg and 5 kg. Results showed that scale up of instant corn rice producing products with rehydration ratio ranges between 514% - 570%, the absorption rate ranged between 414% - 470%, swelling rate ranging between 119% - 134%, bulk density ranged from 0.3661 to 0.4745 (g/ml) and porosity ranging between 30-37%. The physical quality of instant corn rice on scale up were stable from the ones at laboratory scale on swelling rate, rehydration ratio, and absorption rate but not stable on bulk density and porosity. Organoleptic qualities were stable at increased scale compared on a laboratory scale. Bulk density was higher than those at laboratory scale, and the porosity was lower than those at laboratory scale.

Laboratory Measurements of Celestial Solids

NASA Technical Reports Server (NTRS)

Sievers, A. J.; Beckwith, S. V. W.

1997-01-01

Our experimental study has focused on laboratory measurements of the low temperature optical properties of a variety of astronomically significant materials in the infrared and mm-wave region of the spectrum. Our far infrared measurements of silicate grains with an open structure have produced a variety of unusual results: (1) the low temperature mass opacity coefficient of small amorphous 2MgO(central dot)SiO2 and MgO(central dot)2SiO2 grains are many times larger than the values previously used for interstellar grain material; (2) all of the amorphous silicate grains studied possess the characteristic temperature dependent signature associated with two level systems in bulk glass; and (3) a smaller but nonzero two level temperature dependence signature is also observed for crystalline particles, its physical origin is unclear. These laboratory measurements yield surprisingly large and variable values for the mm-wave absorption coefficients of small silicate particles similar to interstellar grains, and suggest that the bulk absorptivity of interstellar dust at these long wavelengths will not be well known without such studies. Furthermore, our studies have been useful to better understand the physics of the two level absorption process in amorphous and crystalline grains to gain confidence in the wide applicability of these results.

AN ANALYTIC MODEL OF DUSTY, STRATIFIED, SPHERICAL H ii REGIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodríguez-Ramírez, J. C.; Raga, A. C.; Lora, V.

2016-12-20

We study analytically the effect of radiation pressure (associated with photoionization processes and with dust absorption) on spherical, hydrostatic H ii regions. We consider two basic equations, one for the hydrostatic balance between the radiation-pressure components and the gas pressure, and another for the balance among the recombination rate, the dust absorption, and the ionizing photon rate. Based on appropriate mathematical approximations, we find a simple analytic solution for the density stratification of the nebula, which is defined by specifying the radius of the external boundary, the cross section of dust absorption, and the luminosity of the central star. Wemore » compare the analytic solution with numerical integrations of the model equations of Draine, and find a wide range of the physical parameters for which the analytic solution is accurate.« less

Physical and physicochemical factors effecting transport of chlorohydrocarbon gases from lung alveolar air to blood as measured by the causation of narcosis.

PubMed

Holder, James W

2012-01-01

This systematic investigation examines gas transport in the lung for two sets of chlorohydrocarbons (CHCs): the chloromethanes (C1) and chloroethanes (C2). The C1 series includes chloromethane, methylene chloride, chloroform, and carbon tetrachloride, and the C2 series includes chloroethane, 1,2-dichloroethane, 1, 1, 2-trichloroethane, and 1, 1, 2, 2-tetrachloroethane. Most CHC gases cause narcosis. The comprehensive narcosis work of Lehmann and colleagues on CHCs was used as a basis for the narcosis endpoint in the present examination. The sites for narcosis are located in the brain (midline cortex and posterior parietal area), the spine, and at many peripheral nerve sites. Central nervous system (CNS) exposure executes a multisite, neural transmission set of inhibitions that promotes rapid loss of consciousness, sensory feeling, and current and stored memory while providing temporary amnesia. Absorption into the system requires dissolution into many lipid membranes and binding to lipoproteins. Lipophilicity is a CHC property shared with many anesthetics according to the Meyer-Overton Rule. Many structurally different lipid chemicals produce the narcosis response when the lipid concentration exceeds -67 mM. This suggests narcotic or anesthetic dissolution into CNS membranes until the lipid organization is disrupted or perturbed. This perturbation includes loading of Na(+)- and K(+)-channel transmembrane lipoprotein complexes and disrupting their respective channel functional organizations. The channel functions become attenuated or abrogated until the CHC exposure ceases and CHC loading reverses. This investigation demonstrates how the CHC physical and chemical properties influence the absorption of these CHCs via the lung and the alveolar system on route to the blood. Narcosis in test animals was used here as an objective biological endpoint to study the effects of the physical factors Bp, Vp, Kd (oil: gas) partition, Henry's constant (HK), and water solubility (S%) on gas transport. Narcosis is immediate after gas exposure and requires no chemical activation only absorption into the blood and circulation to CNS narcotic sites. The three physical factors Bp, K(d) (oil: air), and S% vary directly with unitary narcosis (UN) whereas Vp and HK vary inversely with UN in linear log-log relationships for the C2 series but not for the C1 series. Physicochemical properties of C1 series gases indicate why they depart from what is usually assumed to be an Ideal Gas. An essential discriminating process in the distal lung is the limiting alveolar film layer (AFL) and the membrane layer of the alveolar acini. The AFL step influences gas uptake by physically limiting the absorption process. Interaction with and dissolution into aqueous solvent of the AFL is required for transport and narcotic activity. Narcotics or anesthetics must engage the aqueous AFL with sufficient strength to allow transport and absorption for downstream CNS binding. CHCs that do not engage well with the AFL are not narcotic. Lipophilicity and amphipathicity are also essential solvency properties driving narcotics' transport through the alveolar layer, delivery to the blood fats and lipoproteins, and into critical CNS lipids, lipoproteins, and receptor sites that actuate narcosis. AFL disruption is thought to be strongly related to a number of serious pulmonary diseases such acute respiratory distress syndrome, infant respiratory distress syndrome, emphysema, chronic obstructive pulmonary disease, asthma, chronic bronchitis, pneumonia, pulmonary infections, and idiopathic pulmonary fibrosis. The physical factors (Bp, Vp, Kd [oil: gas] partition, Henry's constant, and water solubility [S%]) combine to affect a specific transport through the AFL if lung C > C(0) (threshold concentration for narcosis). The degree of blood CHC absorption depends on dose, lipophilicity, and lung residence time. AFL passage can be manipulated by physical factors of increased pressure (kPa) or increased gas exposure (moles). Molecular lipophilicity facilitates narcosis but lipophilicity alone does not explain narcosis. Vapor pressure is also required for narcosis. Narcotic activity apparently requires stereospecific processing in the AFL and/or down-stream inhibition at stereospecific lipoproteins at CNS inhibitory sites. It is proposed that CHCs likely cannot proceed through the AFL without perturbation or disruption of the integrity of the AFL at the alveoli. CHC physicochemical properties are not expected to allow their transport through the AFL as physiological CO(2) and O(2) naturally do in respiration. This work considers CHC inspiration and systemic absorption into the blood with special emphasis on the CHC potential perturbation effects on the lipid, protein liquid layer supra to the alveolar membrane (AFL). A heuristic gas transport model for the CHCs is presented as guidance for this examination. The gas transport model can be used to study absorption for other gas delivery endpoints of environmental concern such as carcinogens.

Determination of the Self-organized Mesoporous Materials Sorption Capacity in Water Treatment Processes Using Mössbauer Spectroscopy

NASA Astrophysics Data System (ADS)

Feklistov, D. Yu.; Filippov, V. P.; Kurchatov, I. M.; Laguntsov, N. I.

Different approaches to water purification are considered. It is shown that for developing of effective purification methods in the different water treatment technologies special knowledge is necessary. This knowledge deals with physical-chemical processes of used reagents interaction with contaminating impurities. The obtaining of the necessary data on physics-chemical processes such as the formation of chemical compounds of iron, the change in valence state of iron, adsorption and absorption pollutants are analyzed. The usage of iron compounds as a cleaners and the water treatment from the iron pollutant are the events, in which Mössbauer spectroscopy allows to determine not only the chemical changes, but also to obtain quantitative data on the reaction products and on the sizes of reaction products and their quantities.

Editorial

NASA Astrophysics Data System (ADS)

Musilek, L.; Dunn, W. L.

2017-08-01

The selected proceedings of the 13th International Symposium on Radiation Physics (ISRP-13) are presented here across a broad range of important topics including: Fundamental processes in radiation physics, Theoretical investigations, New radiation sources, techniques & detectors, Absorption and fluorescence spectroscopy (XAFS, XANES, XRF Spectroscopy, Raman, Infrared …), Applications of radiation in material science, nano-science & nanotechnology, Applications of radiation in biology & medical science, Applications of radiation in space, earth, energy & environmental sciences, Applications of radiation in cultural heritage & art and Applications of radiation in industry. In total, 48 papers have been accepted for these proceedings.

QED-driven laser absorption

NASA Astrophysics Data System (ADS)

Levy, Matthew; Blackburn, T.; Ratan, N.; Sadler, J.; Ridgers, C.; Kasim, M.; Ceurvorst, L.; Holloway, J.; Baring, M.; Bell, A.; Glenzer, S.; Gregori, G.; Ilderton, A.; Marklund, M.; Tabak, M.; Wilks, S.; Norreys, P.

2016-10-01

Absorption covers the physical processes which convert intense photon flux into energetic particles when a high-power laser (I >1018 W cm-2 where I is intensity at 1 μm wavelength) illuminates optically-thick matter. It underpins important applications of petawatt laser systems today, e.g., in isochoric heating of materials. Next-generation lasers such as ELI are anticipated to produce quantum electrodynamical (QED) bursts of γ-rays and anti-matter via the multiphoton Breit-Wheeler process which could enable scaled laboratory probes, e.g., of black hole winds. Here, applying strong-field QED to advances in plasma kinematic theory, we present a model elucidating absorption limited only by an avalanche of self-created electron-positron pairs at ultra-high-field. The model, confirmed by multidimensional QED-PIC simulations, works over six orders of magnitude in optical intensity and reveals this cascade is initiated at 1.8 x 1025 W cm-2 using a realistic linearly-polarized laser pulse. Here the laser couples its energy into highly-collimated electrons, ions, γ-rays, and positrons at 12%, 6%, 58% and 13% efficiency, respectively. We remark on attributes of the QED plasma state and possible applications.

Hydrogen Sulfide and Ionic Liquids: Absorption, Separation, and Oxidation.

PubMed

Chiappe, Cinzia; Pomelli, Christian Silvio

2017-06-01

Economical and environmental concerns are the main motivations for development of energy-efficient processes and new eco-friendly materials for the capture of greenhouse gases. Currently, H 2 S capture is dominated by physical and/or chemical absorption technologies, which are, however, energy intensive and often problematic from an environmental point of view due to emission of volatile solvent components. Ionic liquids have been proposed as a promising alternative to conventional solvents because of their low volatility and other interesting properties. The aim of the present review paper is to provide a detailed overview of the achievements and difficulties that have been encountered in finding suitable ionic liquids for H 2 S capture. The effect of ionic liquid anions, cations, and functional groups on the H 2 S absorption, separation, and oxidation are highlighted. Recent developments on yet scarcely available molecular simulations and on the development of robust predictive methods are also discussed.

Differential absorption lidar observation on small-time-scale features of water vapor in the atmospheric boundary layer

NASA Astrophysics Data System (ADS)

Kong, Wei; Li, Jiatang; Liu, Hao; Chen, Tao; Hong, Guanglie; Shu, Rong

2017-11-01

Observation on small-time-scale features of water vapor density is essential for turbulence, convection and many other fast atmospheric processes study. For the high signal-to-noise signal of elastic signal acquired by differential absorption lidar, it has great potential for all-day water vapor turbulence observation. This paper presents a set of differential absorption lidar at 935nm developed by Shanghai Institute of Technical Physics of the Chinese Academy of Science for water vapor turbulence observation. A case at the midday is presented to demonstrate the daytime observation ability of this system. "Autocovariance method" is used to separate the contribution of water vapor fluctuation from random error. The results show that the relative error is less than 10% at temporal and spatial resolution of 10 seconds and 60 meters in the ABL. This indicate that the system has excellent performance for daytime water vapor turbulence observation.

Exciton exciton annihilation dynamics in chromophore complexes. II. Intensity dependent transient absorption of the LH2 antenna system.

PubMed

Bruggemann, B; May, V

2004-02-01

Using the multiexciton density matrix theory of excitation energy transfer in chromophore complexes developed in a foregoing paper [J. Chem. Phys. 118, 746 (2003)], the computation of ultrafast transient absorption spectra is presented. Beside static disorder and standard mechanisms of excitation energy dissipation the theory incorporates exciton exciton annihilation (EEA) processes. To elucidate signatures of EEA in intensity dependent transient absorption data the approach is applied to the B850 ring of the LH2 found in rhodobacter sphaeroides. As main indications for two-exciton population and resulting EEA we found (i) a weakening of the dominant single-exciton bleaching structure in the transient absorption, and (ii) an intermediate suppression of long-wavelength and short-wavelength shoulders around the bleaching structure. The suppression is caused by stimulated emission from the two-exciton to the one-exciton state and the return of the shoulders follows from a depletion of two-exciton population according to EEA. The EEA-signature survives as a short-wavelength shoulder in the transient absorption if orientational and energetic disorder are taken into account. Therefore, the observation of the EEA-signatures should be possible when doing frequency resolved transient absorption experiments with a sufficiently strongly varying pump-pulse intensity. Copyright 2004 American Institute of Physics

Extrusion and Extruded Products: Changes in Quality Attributes as Affected by Extrusion Process Parameters: A Review.

PubMed

Alam, M S; Kaur, Jasmeen; Khaira, Harjot; Gupta, Kalika

2016-01-01

Extrusion of foods is an emerging technology for the food industries to process and market a large number of products of varying size, shape, texture, and taste. Extrusion cooking technology has led to production of wide variety of products like pasta, breakfast cereals, bread crumbs, biscuits, crackers, croutons, baby foods, snack foods, confectionery items, chewing gum, texturized vegetable protein (TVP), modified starch, pet foods, dried soups, dry beverage mixes etc. The functional properties of extruded foods plays an important role for their acceptability which include water absorption, water solubility, oil absorption indexes, expansion index, bulk density and viscosity of the dough. The aim of this review is to give the detailed outlines about the potential of extrusion technology in development of different types of products and the role of extrusion-operating conditions and their effect on product development resulting in quality changes i.e physical, chemical, and nutritional, experienced during the extrusion process.

Five-Photon Absorption and Selective Enhancement of Multiphoton Absorption Processes

PubMed Central

2015-01-01

We study one-, two-, three-, four-, and five-photon absorption of three centrosymmetric molecules using density functional theory. These calculations are the first ab initio calculations of five-photon absorption. Even- and odd-order absorption processes show different trends in the absorption cross sections. The behavior of all even- and odd-photon absorption properties shows a semiquantitative similarity, which can be explained using few-state models. This analysis shows that odd-photon absorption processes are largely determined by the one-photon absorption strength, whereas all even-photon absorption strengths are largely dominated by the two-photon absorption strength, in both cases modulated by powers of the polarizability of the final excited state. We demonstrate how to selectively enhance a specific multiphoton absorption process. PMID:26120588

Five-Photon Absorption and Selective Enhancement of Multiphoton Absorption Processes.

PubMed

Friese, Daniel H; Bast, Radovan; Ruud, Kenneth

2015-05-20

We study one-, two-, three-, four-, and five-photon absorption of three centrosymmetric molecules using density functional theory. These calculations are the first ab initio calculations of five-photon absorption. Even- and odd-order absorption processes show different trends in the absorption cross sections. The behavior of all even- and odd-photon absorption properties shows a semiquantitative similarity, which can be explained using few-state models. This analysis shows that odd-photon absorption processes are largely determined by the one-photon absorption strength, whereas all even-photon absorption strengths are largely dominated by the two-photon absorption strength, in both cases modulated by powers of the polarizability of the final excited state. We demonstrate how to selectively enhance a specific multiphoton absorption process.

Laser Induced Fluorescence Spectroscopy of Neutral and Ionized Polycyclic Aromatic Hydrocarbons in the Cosmic Simulation Chamber

NASA Technical Reports Server (NTRS)

Bejaoui, Salma; Salama, Farid; Contreras, Cesar; Sciamma O'Brien, Ella; Foing, Bernard; Pascale, Ehrenfreund

2015-01-01

Polycyclic aromatic hydrocarbon (PAH) molecules are considered the best carriers to account for the ubiquitous infrared emission bands. PAHs have also been proposed as candidates to explain the diffuse interstellar bands (DIBs), a series of absorption features seen on the interstellar extinction curve and are plausible carriers for the extended red emission (ERE), a photoluminescent process associated with a wide variety of interstellar environments. Extensive efforts have been devoted over the past two decades to characterize the physical and chemical properties of PAH molecules and ions in space. Absorption spectra of PAH molecules and ions trapped in solid matrices have been compared to the DIBs. Absorption spectra of several cold, isolated gas-phase PAHs have also been measured under experimental conditions that mimic the interstellar conditions. The purpose of this study is to provide a new dimension to the existing spectroscopic database of neutral and single ionized PAHs that is largely based on absorption spectra by adding emission spectroscopy data. The measurements are based on the laser induced fluorescence (LIF) technique and are performed with the Pulsed Discharge Nozzle (PDN) of the COSmIC laboratory facility at NASA Ames laboratory. The PDN generates a plasma in a free supersonic jet expansion to simulate the physical and the chemical conditions in interstellar environments. We focus, here, on the fluorescence spectra of large neutral PAHs and their cations where there is a lack of fluorescence spectroscopy data. The astronomical implications of the data (e.g., ERE) are examined.

ABSORPTION OF I$sup 131$ BY THYROID GLAND IN ATHLETES DURING PHYSICAL EXERTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khorol, I.S.

Radioiodine absorption by the thyroid gland after prolonged physical exercise (3000 m race) was studied in 16 athletes, aged 20 to 24 years. Two hours after administration of the isotope the level of its accumulation in the gland was halved. In 24 and 72 hours the content of radioiodine in the gland was higher than in experimental conditions without physical exercise. The phenomenon described evidently reflects the normal reaction of the thyroid gland of athletes to habitual physical exercise. (auth)

Nanoparticle Filtration in a RTM Processed Epoxy/Carbon Fiber Composite

NASA Technical Reports Server (NTRS)

Miller, Sandi G.; Micham, Logan; Copa, Christine C.; Criss, James M., Jr.; Mintz, Eric A.

2011-01-01

Several epoxy matrix composite panels were fabricated by resin transfer molding (RTM) E862/W resin onto a triaxially braided carbon fiber pre-form. Nanoparticles including carbon nanofiber, synthetic clay, and functionalized graphite were dispersed in the E862 matrix, and the extent of particle filtration during processing was characterized. Nanoparticle dispersion in the resin flashing on both the inlet and outlet edges of the panel was compared by TEM. Variation in physical properties such as Tg and moisture absorption throughout the panel were also characterized. All nanoparticle filled panels showed a decrease in Tg along the resin flow path across the panel, indicating nanoparticle filtration, however there was little change in moisture absorption. This works illustrates the need to obtain good nano-particle dispersion in the matrix resin to prevent particle agglomeration and hence particle filtration in the resultant polymer matrix composites (PMC).

Effect of ZnO on the Physical Properties and Optical Band Gap of Soda Lime Silicate Glass

PubMed Central

Zaid, Mohd Hafiz Mohd; Matori, Khamirul Amin; Aziz, Sidek Hj. Abdul; Zakaria, Azmi; Ghazali, Mohd Sabri Mohd

2012-01-01

This manuscript reports on the physical properties and optical band gap of five samples of soda lime silicate (SLS) glass combined with zinc oxide (ZnO) that were prepared by a melting and quenching process. To understand the role of ZnO in this glass structure, the density, molar volume and optical band gaps were investigated. The density and absorption spectra in the Ultra-Violet-Visible (UV-Visible) region were recorded at room temperature. The results show that the densities of the glass samples increased as the ZnO weight percentage increased. The molar volume of the glasses shows the same trend as the density: the molar volume increased as the ZnO content increased. The optical band gaps were calculated from the absorption edge, and it was found that the optical band gap decreased from 3.20 to 2.32 eV as the ZnO concentration increased. PMID:22837711

From Förster resonance energy transfer to coherent resonance energy transfer and back

NASA Astrophysics Data System (ADS)

Clegg, Robert M.; Sener, Melih; Govindjee, .

2010-02-01

Photosynthesis converts solar energy into chemical energy. It provides food and oxygen; and, in the future, it could directly provide bioenergy or renewable energy sources, such as bio-alcohol or hydrogen. To exploit such a highly efficient capture of energy requires an understanding of the fundamental physics. The process is initiated by photon absorption, followed by highly efficient and extremely rapid transfer and trapping of the excitation energy. We first review early fluorescence experiments on in vivo energy transfer, which were undertaken to understand the mechanism of such efficient energy capture. A historical synopsis is given of experiments and interpretations by others that dealt with the question of how energy is transferred from the original location of photon absorption in the photosynthetic antenna system into the reaction centers, where it is converted into useful chemical energy. We conclude by examining the physical basis of some current models concerning the roles of coherent excitons and incoherent hopping in the exceptionally efficient transfer of energy into the reaction center.

Effect of oxalic acid pretreatment of wood chips on manufacturing medium-density fiberboard

Treesearch

Xianjun Li; Zhiyong Cai; Eric Horn; Jerrold E. Winandy

2011-01-01

The main objective of this study was to evaluate the effect of oxalic acid (OA) wood chips pretreatment prior to refining, which is done to reduce energy used during the refining process. Selected mechanical and physical performances of medium-density fiberboard (MDF) – internal bonding (IB), modulus of elasticity (MOE), modulus of rupture (MOR), water absorption (WA)...

ESO Large Program on physical studies of Trans-Neptunian objects and Centaurs: Final results of the visible spectrophotometric observations

NASA Astrophysics Data System (ADS)

Fornasier, S.; Doressoundiram, A.; Tozzi, G. P.; Barucci, M. A.; Boehnhardt, H.; de Bergh, C.; Delsanti, A.; Davies, J.; Dotto, E.

2004-07-01

The Large Program on physical studies of TNOs and Centaurs, started at ESO Cerro Paranal on April 2001, has recently been concluded. This project was devoted to the investigation of the surface properties of these icy bodies through photometric and spectroscopic observations. In this paper we present the latest results on these pristine bodies obtained from the spectrophotometric investigation in the visible range. The newly obtained spectrophotometric data on 3 Centaurs and 5 TNOs, coming from 2 observing runs at the Very Large Telescope (VLT), show a large variety of spectral characteristics, comprising both gray and red objects in the two different populations. A very broad and weak absorption feature, centered around 7000 Å , has been revealed in the spectrum of the gray TNO 2003 AZ84. This absorption is very similar to a feature observed on low albedo main belt asteroids and attributed to the action of the aqueous alteration process on minerals. This process was previously also claimed as the most plausible explanation for some peculiar visible absorption bands observed on 2000 EB173 and 2000 GN171 in the framework of the Large Program (Lazzarin et al. \\cite{Lazzarin03}; de Bergh et al. \\cite{Bergh04}). This detection seems to reinforce the hypothesis that aqueous alteration might have taken place also at such large heliocentric distances. We also report the results of a spectroscopic investigation performed outside the Large Program on the very interesting TNO 2000 GN171 during part of its rotational period. This object, previously observed twice in the framework of the Large Program, had shown during the early observations a very peculiar absorption band tentatively attributed to aqueous alteration processes. As this feature was not confirmed in a successive spectrum, we recently repeated the investigations of 2000 GN171, finding out that it has an heterogeneous composition. Finally an analysis of the visible spectral slopes is reported for all the data coming from the Large Program and those available in literature. Based on observations obtained at the VLT Observatory Cerro Paranal of European Southern Observatory, ESO, Chile, in the framework of programs 167.C-0340(G), 071.C-0500.

Exercise, Insulin Absorption Rates, and Artificial Pancreas Control

NASA Astrophysics Data System (ADS)

Frank, Spencer; Hinshaw, Ling; Basu, Rita; Basu, Ananda; Szeri, Andrew J.

2016-11-01

Type 1 Diabetes is characterized by an inability of a person to endogenously produce the hormone insulin. Because of this, insulin must be injected - usually subcutaneously. The size of the injected dose and the rate at which the dose reaches the circulatory system have a profound effect on the ability to control glucose excursions, and therefore control of diabetes. However, insulin absorption rates via subcutaneous injection are variable and depend on a number of factors including tissue perfusion, physical activity (vasodilation, increased capillary throughput), and other tissue geometric and physical properties. Exercise may also have a sizeable effect on the rate of insulin absorption, which can potentially lead to dangerous glucose levels. Insulin-dosing algorithms, as implemented in an artificial pancreas controller, should account accurately for absorption rate variability and exercise effects on insulin absorption. The aforementioned factors affecting insulin absorption will be discussed within the context of both fluid mechanics and data driven modeling approaches.

Enhanced in vivo absorption of CB-1 antagonist in rats via solid solutions prepared by hot-melt extrusion.

PubMed

Ranzani, L S; Font, J; Galimany, F; Santanach, A; Gomez-Gomar, A M; Casadevall, G; Gryczke, A

2011-06-01

The aim of the present work was to investigate in vitro dissolution properties of three binary solid solutions prepared by a hot-melt extrusion (HME) process with vinyl pirrolidone--vinyl acetate copolymer (Kollidon VA 64), ethyl acrylate, methyl methacrylate polymer (Eudragit E) polyetilenglicol 8000 (PEG 8000) with a cannabinoid type 1 (CB-1) antagonist. Hansen solubility parameters were calculated from the chemical structures of the drug and the individual polymers in order to predict miscibility. Solid state characterizations of drug substance, physical blends and HME formulations were performed with differential scanning calorimetry. The dissolution testing conducted under sink conditions revealed that the dissolution rate of HME formulations improved around 1.8-fold vs drug substance. Supersaturation dissolution study demonstrated that HME formulations composed by Eudragit E and Kollidon VA64 increased drug solubility between 30- and 35-fold, respectively comparing to the drug substance. Physical and chemical stability of formulations were studied at 40°C/75%HR with open dish during 15 days. The formulation composed by the drug and Eudragit E at 10:90 was evaluated for in vivo drug absorption in male Wistar-Hannover rats and it was found to increase CB-1 absorption threefold greater than pure drug oral suspension.

Investigating a physical basis for spectroscopic estimates of leaf nitrogen concentration

USGS Publications Warehouse

Kokaly, R.F.

2001-01-01

The reflectance spectra of dried and ground plant foliage are examined for changes directly due to increasing nitrogen concentration. A broadening of the 2.1-??m absorption feature is observed as nitrogen concentration increases. The broadening is shown to arise from two absorptions at 2.054 ??m and 2.172 ??m. The wavelength positions of these absorptions coincide with the absorption characteristics of the nitrogen-containing amide bonds in proteins. The observed presence of these absorption features in the reflectance spectra of dried foliage is suggested to form a physical basis for high correlations established by stepwise multiple linear regression techniques between the reflectance of dry plant samples and their nitrogen concentration. The consistent change in the 2.1-??m absorption feature as nitrogen increases and the offset position of protein absorptions compared to those of other plant components together indicate that a generally applicable algorithm may be developed for spectroscopic estimates of nitrogen concentration from the reflectance spectra of dried plant foliage samples. ?? 2001 Published by Elsevier Science Ireland Ltd.

Effect of the carbonyl iron particles on acoustic absorption properties of magnetic polyurethane foam

NASA Astrophysics Data System (ADS)

Geng, Jialu; Wang, Caiping; Zhu, Honglang; Wang, Xiaojie

2018-03-01

Elastomeric matrix embedded with magnetic micro-sized particles has magnetically controllable properties, which has been investigated extensively in the last decades. In this study we develop a new magnetically controllable elastomeric material for acoustic applications at lower frequencies. The soft polyurethane foam is used as matrix material due to its extraordinary elastic and acoustic absorption properties. One-step method is used to synthesize polyurethane foam, in which all components including polyether polyols 330N, MDI, deionized water, silicone oil, carbonyl iron particle (CIP) and catalyst are put into one container for curing. Changing any component can induce the change of polyurethane foam's properties, such as physical and acoustic properties. The effect of the content of MDI on acoustic absorption is studied. The CIPs are aligned under extra magnetic field during the foaming process. And the property of polyurethane foam with aligned CIPs is also investigated. Scanning electron microscope (SEM) is used to observe the structure of pore and particle-chain. The two-microphone impedance tube and the transfer function method are used to test acoustic absorption property of the magnetic foams.

Encapsulation of Ionic Liquids with an Aprotic Heterocyclic Anion (AHA-IL) for CO2 Capture: Preserving the Favorable Thermodynamics and Enhancing the Kinetics of Absorption.

PubMed

Moya, Cristian; Alonso-Morales, Noelia; de Riva, Juan; Morales-Collazo, Oscar; Brennecke, Joan F; Palomar, Jose

2018-03-08

The performance of an ionic liquid with an aprotic heterocyclic anion (AHA-IL), trihexyl(tetradecyl)phosphonium 2-cyanopyrrolide ([P 66614 ][2-CNPyr]), for CO 2 capture has been evaluated considering both the thermodynamics and the kinetics of the phenomena. Absorption gravimetric measurements of the gas-liquid equilibrium isotherms of CO 2 -AHA-IL systems were carried out from 298 to 333 K and at pressures up to 15 bar, analyzing the role of both chemical and physical absorption phenomena in the overall CO 2 solubility in the AHA-IL, as has been done previously. In addition, the kinetics of the CO 2 chemical absorption process was evaluated by in situ Fourier transform infrared spectroscopy-attenuated total reflection, following the characteristic vibrational signals of the reactants and products over the reaction time. A chemical absorption model was used to describe the time-dependent concentration of species involved in the reactive absorption, obtaining kinetic parameters (such as chemical reaction kinetic constants and diffusion coefficients) as a function of temperatures and pressures. As expected, the results demonstrate that the CO 2 absorption rate is mass-transfer-controlled because of the relatively high viscosity of AHA-IL. The AHA-IL was encapsulated in a porous carbon sphere (Encapsulated Ionic Liquid, ENIL) to improve the kinetic performance of the AHA-IL for CO 2 capture. The newly synthesized AHA-ENIL material was evaluated as a CO 2 sorbent with gravimetric absorption measurements. AHA-ENIL systems preserve the good CO 2 absorption capacity of the AHA-IL but drastically enhance the CO 2 absorption rate because of the increased gas-liquid surface contact area achieved by solvent encapsulation.

Numerical analysis of the heating phase and densification mechanism in polymers selective laser melting process

NASA Astrophysics Data System (ADS)

Mokrane, Aoulaiche; Boutaous, M'hamed; Xin, Shihe

2018-05-01

The aim of this work is to address a modeling of the SLS process at the scale of the part in PA12 polymer powder bed. The powder bed is considered as a continuous medium with homogenized properties, meanwhile understanding multiple physical phenomena occurring during the process and studying the influence of process parameters on the quality of final product. A thermal model, based on enthalpy approach, will be presented with details on the multiphysical couplings that allow the thermal history: laser absorption, melting, coalescence, densification, volume shrinkage and on numerical implementation using FV method. The simulations were carried out in 3D with an in-house developed FORTRAN code. After validation of the model with comparison to results from literature, a parametric analysis will be proposed. Some original results as densification process and the thermal history with the evolution of the material, from the granular solid state to homogeneous melted state will be discussed with regards to the involved physical phenomena.

Speciation of metal(loid)s in environmental samples by X-ray absorption spectroscopy: a critical review.

PubMed

Gräfe, Markus; Donner, Erica; Collins, Richard N; Lombi, Enzo

2014-04-25

Element specificity is one of the key factors underlying the widespread use and acceptance of X-ray absorption spectroscopy (XAS) as a research tool in the environmental and geo-sciences. Independent of physical state (solid, liquid, gas), XAS analyses of metal(loid)s in complex environmental matrices over the past two decades have provided important information about speciation at environmentally relevant interfaces (e.g. solid-liquid) as well as in different media: plant tissues, rhizosphere, soils, sediments, ores, mineral process tailings, etc. Limited sample preparation requirements, the concomitant ability to preserve original physical and chemical states, and independence from crystallinity add to the advantages of using XAS in environmental investigations. Interpretations of XAS data are founded on sound physical and statistical models that can be applied to spectra of reference materials and mixed phases, respectively. For spectra collected directly from environmental matrices, abstract factor analysis and linear combination fitting provide the means to ascertain chemical, bonding, and crystalline states, and to extract quantitative information about their distribution within the data set. Through advances in optics, detectors, and data processing, X-ray fluorescence microprobes capable of focusing X-rays to micro- and nano-meter size have become competitive research venues for resolving the complexity of environmental samples at their inherent scale. The application of μ-XANES imaging, a new combinatorial approach of X-ray fluorescence spectrometry and XANES spectroscopy at the micron scale, is one of the latest technological advances allowing for lateral resolution of chemical states over wide areas due to vastly improved data processing and detector technology. Copyright © 2014. Published by Elsevier B.V.

Engineering Design Handbook: Environmental Series. Part Five. Glossary of Environmental Terms

DTIC Science & Technology

1975-07-31

temperature, surface. shield. In cables, the metallic layer applied over the dielectric, or group of dielectrics, composed of woven, braided , or served...greases, thereby reducing corrosion of metals and hardening of seals. active vibration isolation and absorption systems. Servomechanism-type systems...Usually refers to grav- AMCP708119 el or crashed rock. Sometimes called road metal (in England) (Ref. 1). aging. A gradual process involving physical

Unveiling the Diffuse, Neutral Interstellar Medium: Absorption Spectroscopy of Galactic Hydrogen

NASA Astrophysics Data System (ADS)

Murray, Claire Elizabeth

The formation of stars and evolution of galaxies depends on the cycle of interstellar matter between supernova-expelled plasma and molecule-rich gas. At the center of this cycle is multiphase neutral hydrogen (HI), whose physical conditions provide key ingredients to theoretical models. However, constraints for HI properties require measurements of gas emission and absorption which have been severely limited by previous observational capabilities. In this thesis, I present the largest survey of Galactic HI absorption ever undertaken with the Karl G. Jansky Very Large Array (VLA). The survey, 21 cm Spectral Line Observations of Neutral Gas with the VLA (21-SPONGE), is a statistical study of HI in all phases using direct absorption measurements. Leveraging novel calibration techniques, I demonstrate the capability of the VLA to detect a significant sample of 21 cm absorption lines from warm, diffuse HI. To maximize observational sensitivity, I stack the 21-SPONGE spectra and detect a pervasive signature of the warm neutral medium in absorption. The inferred excitation (or spin) temperature is consistent with existing estimates, yet higher than predictions from theoretical models of collisional HI excitation. This suggests that radiative feedback via resonant scattering of Lyalpha photons, known as the Wouthuysen-Field effect, is influential with important implications for cosmological 21 cm observations. Next, I compare 21-SPONGE with synthetic HI spectra from 3D numerical simulations using a new, objective decomposition and radiative transfer tool. I quantify the recovery of HI structures and their properties by Gaussian-fitted 21 cm spectral lines for the first time. I find that 21 cm absorption line shapes are sensitive to simulated physics, and demonstrate that my analysis method is a powerful tool for diagnosing neutral ISM conditions. Finally, I compare properties inferred from synthetic spectra with "true" simulation results to construct a bias correction function for estimating HI properties. I apply this correction to the mass distribution of HI as a function of temperature from 21-SPONGE, and find a significant fraction of thermally unstable gas. This confirms that non-steady radiative and dynamical processes, such as turbulence and supernovae, have a strong influence on the thermodynamic state of the ISM.

Production of photocurrent due to intermediate-to-conduction-band transitions: a demonstration of a key operating principle of the intermediate-band solar cell.

PubMed

Martí, A; Antolín, E; Stanley, C R; Farmer, C D; López, N; Díaz, P; Cánovas, E; Linares, P G; Luque, A

2006-12-15

We present intermediate-band solar cells manufactured using quantum dot technology that show for the first time the production of photocurrent when two sub-band-gap energy photons are absorbed simultaneously. One photon produces an optical transition from the intermediate-band to the conduction band while the second pumps an electron from the valence band to the intermediate-band. The detection of this two-photon absorption process is essential to verify the principles of operation of the intermediate-band solar cell. The phenomenon is the cornerstone physical principle that ultimately allows the production of photocurrent in a solar cell by below band gap photon absorption, without degradation of its output voltage.

Directional Canopy Emissivity Estimation Based on Spectral Invariants

NASA Astrophysics Data System (ADS)

Guo, M.; Cao, B.; Ren, H.; Yongming, D.; Peng, J.; Fan, W.

2017-12-01

Land surface emissivity is a crucial parameter for estimating land surface temperature from remote sensing data and also plays an important role in the physical process of surface energy and water balance from local to global scales. To our knowledge, the emissivity varies with surface type and cover. As for the vegetation, its canopy emissivity is dependent on vegetation types, viewing zenith angle and structure that changes in different growing stages. Lots of previous studies have focused on the emissivity model, but few of them are analytic and suited to different canopy structures. In this paper, a new physical analytic model is proposed to estimate the directional emissivity of homogenous vegetation canopy based on spectral invariants. The initial model counts the directional absorption in six parts: the direct absorption of the canopy and the soil, the absorption of the canopy and soil after a single scattering and after multiple scattering within the canopy-soil system. In order to analytically estimate the emissivity, the pathways of photons absorbed in the canopy-soil system are traced using the re-collision probability in Fig.1. After sensitive analysis on the above six absorptions, the initial complicated model was further simplified as a fixed mathematic expression to estimate the directional emissivity for vegetation canopy. The model was compared with the 4SAIL model, FRA97 model, FRA02 model and DART model in Fig.2, and the results showed that the FRA02 model is significantly underestimated while the FRA97 model is a little underestimated, on basis of the new model. On the contrary, the emissivity difference between the new model with the 4SAIL model and DART model was found to be less than 0.002. In general, since the new model has the advantages of mathematic expression with accurate results and clear physical meaning, the model is promising to be extended to simulate the directional emissivity for the discrete canopy in further study.

Two Photon Absorption And Refraction in Bulk of the Semiconducting Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumari, Vinay; Department of Physics, DCRUST Murthal, Haryana; Kumar, Vinod

2011-10-20

Fast electronic detection systems have opened up a number of new fields like nonlinear optics, optical communication, coherent optics, optical bistability, two/four wave mixing. The interest in this field has been stimulated by the importance of multiphoton processes in many fundamental aspects of physics. It has proved to be an invaluable tool for determining the optical and electronic properties of the solids because of the fact that one gets the information about the bulk of the material rather than the surface one. In this paper we report, the measurement of the nonlinear absorption and refraction from the band gap tomore » half-band gap region of bulk of semiconductors in the direct and indirect band gap crystals with nanosecond laser. The measured theoretical calculated values of two-photon absorption coefficients ({beta}) and nonlinear refraction n{sub 2}({omega}) of direct band gap crystal match the earlier reported theoretical predictions. By making use of these theoretical calculated values, we have estimated {beta} and n{sub 2}({omega}) in the case of indirect band gap crystals. Low value of absorption coefficient in case of indirect band gap crystals have been attributed to phonon assisted transition while reduction in nonlinear refraction is due to the rise in saturation taking place in the absorption.« less

Ionized absorbers, ionized emitters, and the X-ray spectrum of active galactic nuclei

NASA Technical Reports Server (NTRS)

Netzer, Hagai

1993-01-01

Broad absorption features are common in the X-ray spectrum of low-luminosity AGNs. The features have been modeled by leaky neutral absorbers or by highly ionized gas that completely occult the continuum source. Such models are incomplete since they do not take into account all the physical processes in the gas. In particular, no previous model included the X-ray emission by the ionized absorbing gas and the reflection of the continuum source radiation. The present work discusses the emission, absorption, and reflection properties of photoionized gases with emphasis on conditions thought to prevail in AGNs. It shows that such gas is likely to produce intense X-ray line and continuum radiation and to reflect a sizable fraction of the nonstellar continuum at all energies. If such gas is indeed responsible for the observed X-ray absorption, then absorption edges are much weaker than commonly assumed, and some residual X-ray continuum is likely to be observed even if the line of sight is completely blocked. Moreover, X-ray emission features may show up in sources not showing X-ray absorption. This has immense consequences for medium-resolution X-ray missions, such as BBXRT and Astro-D, and for the planned high-resolution experiments on board XMM and AXAF.

A Low-Cost Quantitative Absorption Spectrophotometer

ERIC Educational Resources Information Center

Albert, Daniel R.; Todt, Michael A.; Davis, H. Floyd

2012-01-01

In an effort to make absorption spectrophotometry available to high school chemistry and physics classes, we have designed an inexpensive visible light absorption spectrophotometer. The spectrophotometer was constructed using LEGO blocks, a light emitting diode, optical elements (including a lens), a slide-mounted diffraction grating, and a…

Modeling and experimental analysis of electrospinning bending region physics in determining fiber diameter for hydrophilic polymer solvent systems

NASA Astrophysics Data System (ADS)

Cai, Yunshen

Electrospinning produces submicron fibers from a wide range of polymer/solvent systems that enable a variety of different applications. In electrospinning process, a straight polymer/solvent charged jet is initially formed, followed by a circular moving jet in the shape of a cone, called the bending region. The process physics in the bending region are difficult to study since the jet diameter cannot be measured directly due to its rapid motion and small size ( microns and smaller), and due to complex coupling of multiple forces, mass transport, and changing jet geometry. Since the solutions studied are hydrophilic, they readily absorb ambient moisture. This thesis explores the role of the bending region in determining the resulting electrospun fiber diameter through a combined experimental and modeling analysis for a variety of hydrophilic polymer/solvent solutions. Electrospinning experiments were conducted over a broad range of operating conditions for 4 different polymer/solvent systems. Comparison of the final straight jet diameters to fiber diameters reveals that between 30% to 60% jet thinning occurs in the bending region. These experiments also reveal that relative humidity significantly affects the electrospinning process and final fiber diameter, even for non-aqueous solutions. A model is developed to obtain insight into the bending region process physics. Important ones include understanding the mass transport for non-aqueous hydrophilic jets (including solvent evaporation and water absorption on the jet surface, radial diffusion, and axial advection), and the coupling between the mass and force balances that determines the final fiber diameter. The absorption and evaporation physics is validated by evaporation experiments. The developed model predicts fiber diameter to within of 8%, even though the solution properties and operating conditions that determines net stretching forces and net evaporation rates vary over a large range. Model analysis reveals how the net evaporation rate affects the jet length and net stretching force, both of which ultimately determine the fiber diameter. It is also shown that the primary impact of RH on the process is through occupation of the surface states that limits solvent evaporation rate, rather than the amount of water absorbed. Correlation functions between process conditions, solution properties and the resulting fiber diameters are discussed.

[Thermodynamic analysis of water adsorption and desorption process of Chinese herbal decoction pieces].

PubMed

Cheng, Lin; Luo, Xiao-Jian; Han, Xiu-Lin; Wang, Wen-Kai; Rao, Xiao-Yong; Xu, Shao-Zhong; He, Yan

2016-09-01

Based on the basic theory of thermodynamics, the thermodynamic parameters and related equations in the process of water adsorption and desorption of Chinese herbal decoction pieces were established, and their water absorption and desorption characteristics were analyzed. The physical significance of the thermodynamic parameters, such as differential adsorption enthalpy, differential adsorption entropy, integral adsorption enthalpy, integral adsorption entropy and the free energy of adsorption, were discussed in this paper to provide theoretical basis for the research on the water adsorption and desorption mechanism, optimum drying process parameters, storage conditions and packaging methods of Chinese herbal decoction pieces. Copyright© by the Chinese Pharmaceutical Association.

Statistical models for sediment/detritus and dissolved absorption coefficients in coastal waters of the northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Green, Rebecca E.; Gould, Richard W., Jr.; Ko, Dong S.

2008-06-01

We developed statistically-based, optical models to estimate tripton (sediment/detrital) and colored dissolved organic matter (CDOM) absorption coefficients ( a sd, a g) from physical hydrographic and atmospheric properties. The models were developed for northern Gulf of Mexico shelf waters using multi-year satellite and physical data. First, empirical algorithms for satellite-derived a sd and a g were developed, based on comparison with a large data set of cruise measurements from northern Gulf shelf waters; these algorithms were then applied to a time series of ocean color (SeaWiFS) satellite imagery for 2002-2005. Unique seasonal timing was observed in satellite-derived optical properties, with a sd peaking most often in fall/winter on the shelf, in contrast to summertime peaks observed in a g. Next, the satellite-derived values were coupled with the physical data to form multiple regression models. A suite of physical forcing variables were tested for inclusion in the models: discharge from the Mississippi River and Mobile Bay, Alabama; gridded fields for winds, precipitation, solar radiation, sea surface temperature and height (SST, SSH); and modeled surface salinity and currents (Navy Coastal Ocean Model, NCOM). For satellite-derived a sd and a g time series (2002-2004), correlation and stepwise regression analyses revealed the most important physical forcing variables. Over our region of interest, the best predictors of tripton absorption were wind speed, river discharge, and SST, whereas dissolved absorption was best predicted by east-west wind speed, river discharge, and river discharge lagged by 1 month. These results suggest the importance of vertical mixing (as a function of winds and thermal stratification) in controlling a sd distribution patterns over large regions of the shelf, in comparison to advection as the most important control on a g. The multiple linear regression models for estimating a sd and a g were applied on a pixel-by-pixel basis and results were compared to monthly SeaWiFS composite imagery. The models performed well in resolving seasonal and interannual optical variability in model development years (2002-2004) (mean error of 32% for a sd and 29% for a g) and in predicting shelfwide optical patterns in a year independent of model development (2005; mean error of 41% for a sd and 46% for a g). The models provide insight into the dominant processes controlling optical distributions in this region, and they can be used to predict the optical fields from the physical properties at monthly timescales.

Threshold response using modulated continuous wave illumination for multilayer 3D optical data storage

NASA Astrophysics Data System (ADS)

Saini, A.; Christenson, C. W.; Khattab, T. A.; Wang, R.; Twieg, R. J.; Singer, K. D.

2017-01-01

In order to achieve a high capacity 3D optical data storage medium, a nonlinear or threshold writing process is necessary to localize data in the axial dimension. To this end, commercial multilayer discs use thermal ablation of metal films or phase change materials to realize such a threshold process. This paper addresses a threshold writing mechanism relevant to recently reported fluorescence-based data storage in dye-doped co-extruded multilayer films. To gain understanding of the essential physics, single layer spun coat films were used so that the data is easily accessible by analytical techniques. Data were written by attenuating the fluorescence using nanosecond-range exposure times from a 488 nm continuous wave laser overlapping with the single photon absorption spectrum. The threshold writing process was studied over a range of exposure times and intensities, and with different fluorescent dyes. It was found that all of the dyes have a common temperature threshold where fluorescence begins to attenuate, and the physical nature of the thermal process was investigated.

Diesel NO{sub x} reduction by plasma-regenerated absorbent beds

DOEpatents

Wallman, P.H.; Vogtlin, G.E.

1998-02-10

Reduction of NO{sub x} from diesel engine exhaust by use of plasma-regenerated absorbent beds is described. This involves a process for the reduction of NO{sub x} and particulates from diesel engines by first absorbing NO{sub x} onto a solid absorbent bed that simultaneously acts as a physical trap for the particulate matter, and second regenerating said solid absorbent by pulsed plasma decomposition of absorbed NO{sub x} followed by air oxidation of trapped particulate matter. The absorbent bed may utilize all metal oxides, but the capacity and the kinetics of absorption and desorption vary between different materials, and thus the composition of the absorbent bed is preferably a material which enables the combination of NO{sub x} absorption capability with catalytic activity for oxidation of hydrocarbons. Thus, naturally occurring or synthetically prepared materials may be utilized, particularly those having NO{sub x} absorption properties up to temperatures around 400 C which is in the area of diesel engine exhaust temperatures. 1 fig.

Diesel NO.sub.x reduction by plasma-regenerated absorbend beds

DOEpatents

Wallman, P. Henrik; Vogtlin, George E.

1998-01-01

Reduction of NO.sub.x from diesel engine exhaust by use of plasma-regenerated absorbent beds. This involves a process for the reduction of NO.sub.x and particulates from diesel engines by first absorbing NO.sub.x onto a solid absorbent bed that simultaneously acts as a physical trap for the particulate matter, and second regenerating said solid absorbent by pulsed plasma decomposition of absorbed NO.sub.x followed by air oxidation of trapped particulate matter. The absorbent bed may utilize all metal oxides, but the capacity and the kinetics of absorption and desorption vary between different materials, and thus the composition of the absorbent bed is preferably a material which enables the combination of NO.sub.x absorption capability with catalytic activity for oxidation of hydrocarbons. Thus, naturally occurring or synthetically prepared materials may be utilized, particularly those having NO.sub.x absorption properties up to temperatures around 400.degree. C. which is in the area of diesel engine exhaust temperatures.

Fringes in FTIR spectroscopy revisited: understanding and modelling fringes in infrared spectroscopy of thin films.

PubMed

Konevskikh, Tatiana; Ponossov, Arkadi; Blümel, Reinhold; Lukacs, Rozalia; Kohler, Achim

2015-06-21

The appearance of fringes in the infrared spectroscopy of thin films seriously hinders the interpretation of chemical bands because fringes change the relative peak heights of chemical spectral bands. Thus, for the correct interpretation of chemical absorption bands, physical properties need to be separated from chemical characteristics. In the paper at hand we revisit the theory of the scattering of infrared radiation at thin absorbing films. Although, in general, scattering and absorption are connected by a complex refractive index, we show that for the scattering of infrared radiation at thin biological films, fringes and chemical absorbance can in good approximation be treated as additive. We further introduce a model-based pre-processing technique for separating fringes from chemical absorbance by extended multiplicative signal correction (EMSC). The technique is validated by simulated and experimental FTIR spectra. It is further shown that EMSC, as opposed to other suggested filtering methods for the removal of fringes, does not remove information related to chemical absorption.

Highly efficient SO2 capture by dual functionalized ionic liquids through a combination of chemical and physical absorption.

PubMed

Cui, Guokai; Wang, Congmin; Zheng, Junjie; Guo, Yan; Luo, Xiaoyan; Li, Haoran

2012-03-07

Two kinds of dual functionalized ionic liquids with ether-functionalized cations and tetrazolate anions were designed, prepared, and used for SO(2) capture, which exhibit an extremely high SO(2) capacity and excellent reversibility through a combination of chemical and physical absorption. This journal is © The Royal Society of Chemistry 2012

Ultrafast graphene and carbon nanotube film patterning by picosecond laser pulses

NASA Astrophysics Data System (ADS)

Bobrinetskiy, Ivan I.; Emelianov, Alexey V.; Otero, Nerea; Romero, Pablo M.

2016-03-01

Carbon nanomaterials is among the most promising technologies for advanced electronic applications, due to their extraordinary chemical and physical properties. Nonetheless, after more than two decades of intensive research, the application of carbon-based nanostructures in real electronic and optoelectronic devices is still a big challenge due to lack of scalable integration in microelectronic manufacturing. Laser processing is an attractive tool for graphene device manufacturing, providing a large variety of processes through direct and indirect interaction of laser beams with graphene lattice: functionalization, oxidation, reduction, etching and ablation, growth, etc. with resolution down to the nanoscale. Focused laser radiation allows freeform processing, enabling fully mask-less fabrication of devices from graphene and carbon nanotube films. This concept is attractive to reduce costs, improve flexibility, and reduce alignment operations, by producing fully functional devices in single direct-write operations. In this paper, a picosecond laser with a wavelength of 515 nm and pulse width of 30 ps is used to pattern carbon nanostructures in two ways: ablation and chemical functionalization. The light absorption leads to thermal ablation of graphene and carbon nanotube film under the fluence 60-90 J/cm2 with scanning speed up to 2 m/s. Just under the ablation energy, the two-photon absorption leads to add functional groups to the carbon lattice which change the optical properties of graphene. This paper shows the results of controlled modification of geometrical configuration and the physical and chemical properties of carbon based nanostructures, by laser direct writing.

Physical mechanisms of SiN{sub x} layer structuring with ultrafast lasers by direct and confined laser ablation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rapp, S., E-mail: rapp@hm.edu; Erlangen Graduate School in Advanced Optical Technologies; Heinrich, G.

2015-03-14

In the production process of silicon microelectronic devices and high efficiency silicon solar cells, local contact openings in thin dielectric layers are required. Instead of photolithography, these openings can be selectively structured with ultra-short laser pulses by confined laser ablation in a fast and efficient lift off production step. Thereby, the ultrafast laser pulse is transmitted by the dielectric layer and absorbed at the substrate surface leading to a selective layer removal in the nanosecond time domain. Thermal damage in the substrate due to absorption is an unwanted side effect. The aim of this work is to obtain a deepermore » understanding of the physical laser-material interaction with the goal of finding a damage-free ablation mechanism. For this, thin silicon nitride (SiN{sub x}) layers on planar silicon (Si) wafers are processed with infrared fs-laser pulses. Two ablation types can be distinguished: The known confined ablation at fluences below 300 mJ/cm{sup 2} and a combined partial confined and partial direct ablation at higher fluences. The partial direct ablation process is caused by nonlinear absorption in the SiN{sub x} layer in the center of the applied Gaussian shaped laser pulses. Pump-probe investigations of the central area show ultra-fast reflectivity changes typical for direct laser ablation. Transmission electron microscopy results demonstrate that the Si surface under the remaining SiN{sub x} island is not damaged by the laser ablation process. At optimized process parameters, the method of direct laser ablation could be a good candidate for damage-free selective structuring of dielectric layers on absorbing substrates.« less

Spectroscopy of Reaction Intermediates in Nitramine Decomposition and Combustion

DTIC Science & Technology

1991-06-20

Dakhis and co-workers, s the very strong absorption of MMN near 1332 cm - 1 did not appear. Unassigned absorptions appeared near 930, 1240, 1460, 2990, and...sharp NO2 absorption. In Table I, the positions of these absorptions are compared with the infrared absorptions of MMN reported by Dakhis and co-workers...Chemistry and Physics of Energetic Materials, S. N. Bulusu, Ed., pp. 51-78 (Kluwer Academic Publishers, Dordrecht, 1990). 56. M. I. Dakhis , V. G. Dashevsky

Spectroscopy of Reaction Intermediates in Nitramine Decomposition and Combustion

DTIC Science & Technology

1991-06-20

absorptions of gas-phase MMN reported by Dakhis and co-workers,5 6 the very strong absorption of MMN near 1332 cm - ’ did not appear. Unassigned...sharp NO 2 absorption. In Table I, the positions of these absorptions are compared with the infrared absorptions of MMN reported by Dakhis and co-workers...Chemistry and Physics of Energetic Materials, S. N. Bulusu, Ed., pp. 51-78 (Kluwer Academic Publishers, Dordrecht, 1990). 56. M. I. Dakhis , V. G

Performance of nanocomposites for preservation of artistic stones

NASA Astrophysics Data System (ADS)

Giancristofaro, Cristina; D'Amato, Rosaria; Caneve, Luisa; Pilloni, Luciano; Rinaldi, Antonio; Persia, Franca

2014-06-01

In this work, the effectiveness of nanocomposite surface treatments as protective systems for artistic stones was evaluated. Pyrolitic silica and titania nanoparticles were dispersed in a commercial silicon-based polymer and applied on marble and travertine samples. Artificial aging processes, both in climatic chamber and in solar box, were carried out to simulate real degradation processes in terms of photo-thermal effects and physical-chemical damage. The performances of the nanocomposites used as consolidant were evaluated comparatively by means of diverse diagnostic techniques, namely: scanning electron microscopy (SEM), laser induced fluorescence (LIF), ultrasonic technique, colorimetry, total immersion water absorption and contact angle. The results show that some properties of conservation materials can be improved by the presences of nanoparticles because they induce substantial changes of surface morphology of the coating layer and counter the physical damage observed during artificial weathering.

Dust coagulation in ISM

NASA Technical Reports Server (NTRS)

Chokshi, Arati; Tielens, Alexander G. G. M.; Hollenbach, David

1989-01-01

Coagulation is an important mechanism in the growth of interstellar and interplanetary dust particles. The microphysics of the coagulation process was theoretically analyzed as a function of the physical properties of the coagulating grains, i.e., their size, relative velocities, temperature, elastic properties, and the van der Waal interaction. Numerical calculations of collisions between linear chains provide the wave energy in individual particles and the spectrum of the mechanical vibrations set up in colliding particles. Sticking probabilities are then calculated using simple estimates for elastic deformation energies and for the attenuation of the wave energy due to absorption and scattering processes.

Theoretical studies of spectroscopic problems of importance for atmospheric radiation measurements

NASA Technical Reports Server (NTRS)

Tipping, Richard H.

1994-01-01

Many of the instruments used to deduce the physical parameters of the Earth's atmosphere necessary for climate studies or for pollution monitoring (for instance, temperature versus pressure or number densities of trace molecules) rely on the existence of accurate spectroscopic data and an understanding of the physical processes responsible for the absorption or emission of radiation. During the summer, research was either continued or begun on three distinct problems: (1) an improved theoretical framework for the calculation of the far-wing absorption of allowed spectral lines; (2) a refinement of the calculation of the collision-induced fundamental spectrum of N2; and (3) an investigation of possible line-mixing effects in the fundamental spectrum of CH4. Progress in these three areas is summarized below. During the past few years, we have developed a theoretical framework for the calculation of the absorption of radiation by the far wings of spectral lines. Such absorption due to water vapor plays a crucial role in the greenhouse effect as well as limiting the retrieval of temperature profiles from satellite data. Several improvements in the theory have been made and the results are being prepared for publication. Last year we published results for the theoretical calculation of the absorption of radiation due to the dipoles induced during binary collisions of N2 molecules using independently measured molecular parameters; the results were in reasonable agreement with experimental data. However, recent measurements have revealed new fine structure that has been attributed to line-mixing effects. We do not think that this is correct, rather that the structure results from short-range anisotropic dipoles. We are in the process of including this refinement in our theoretical calculation in order to compare with the new experimental data. Subtle changes in the spectra of CH4 measured by researchers at Langley have also been attributed to line-mixing effects. By analyzing the same spectral lines we have attempted to verify or rule out possible line-mixing mechanisms. Due to the complexity and richness of the spectrum of this highly symmetric molecule, as well as the small magnitude of the effects, a detailed first-principle calculation of the mixing is a difficult problem. Before such a program is undertaken it is important to glean as much information as possible concerning the possible mechanisms by a systematic analysis of the existing data.

Absorption of Solar Radiation by Clouds: Observations Versus Models

NASA Technical Reports Server (NTRS)

Cess, R. D.; Zhang, M. H.; Minnis, P.; Corsetti, L.; Dutton, E. G.; Forgan, B. W.; Garber, D. P.; Gates, W. L.; Hack, J. J.; Harrison, E. F.;

Physical Characteristics of White Sweet Potato (Ipomoea batatas L.), Rice (Oryza sativa L.), and Tapioca (Manihot esculenta) Flours - Based Seasoning Composite Flour

NASA Astrophysics Data System (ADS)

Alfani, NNA; Ishartani, D.; Anam, C.; Praseptiangga, D.; Manuhara, G. J.

2017-04-01

The objective of this study was to determine the physical characteristics of seasoning composite flour that made from white sweet potato, rice, and tapioca flours, and determined the best formula of seasoning composite flour. A completely randomized design (CRD) with formula as the single factor was used. The data were analyzed by one-way ANOVA method and followed by Duncan Multiple Range Test (DMRT) at significance 5% if there was a significant difference. The best formula of seasoning composite flour was 30% tapioca flour, 30% rice flour, and 40% white sweet potato flour. The physical characteristics of the best formula were 5.689 ml/g of swelling power, 2.681 g/g of water absorption capacity, 0.887 ml/g of oil absorption capacity, and 22.03% cooking loss. Physical characteristics of the best seasoning composite flour were significantly different from the commercial seasoning flour and showed a better cooking loss, oil absorption capacity, and swelling power than commercial seasoning flour.

Effect of layer thickness on device response of silicon heavily supersaturated with sulfur

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hutchinson, David; Department of Physics and Nuclear Engineering, United States Military Academy, West Point NY 10996; Mathews, Jay

2016-05-15

We report on a simple experiment in which the thickness of a hyperdoped silicon layer, supersaturated with sulfur by ion implantation followed by pulsed laser melting and rapid solidification, is systematically varied at constant average sulfur concentration, by varying the implantation energy, dose, and laser fluence. Contacts are deposited and the external quantum efficiency (EQE) is measured for visible wavelengths. We posit that the sulfur layer primarily absorbs light but contributes negligible photocurrent, and we seek to support this by analyzing the EQE data for the different layer thicknesses in two interlocking ways. In the first, we use the measuredmore » concentration depth profiles to obtain the approximate layer thicknesses, and, for each wavelength, fit the EQE vs. layer thickness curve to obtain the absorption coefficient of hyperdoped silicon for that wavelength. Comparison to literature values for the hyperdoped silicon absorption coefficients [S.H. Pan et al. Applied Physics Letters 98, 121913 (2011)] shows good agreement. Next, we essentially run this process in reverse; we fit with Beer’s law the curves of EQE vs. hyperdoped silicon absorption coefficient for those wavelengths that are primarily absorbed in the hyperdoped silicon layer, and find that the layer thicknesses obtained from the fit are in good agreement with the original values obtained from the depth profiles. We conclude that the data support our interpretation of the hyperdoped silicon layer as providing negligible photocurrent at high S concentrations. This work validates the absorption data of Pan et al. [Applied Physics Letters 98, 121913 (2011)], and is consistent with reports of short mobility-lifetime products in hyperdoped layers. It suggests that for optoelectronic devices containing hyperdoped layers, the most important contribution to the above band gap photoresponse may be due to photons absorbed below the hyperdoped layer.« less

Role of Ce 4 + in the scintillation mechanism of codoped Gd 3 Ga 3 Al 2 O 12 : Ce

DOE PAGES

Wu, Yuntao; Meng, Fang; Li, Qi; ...

2014-10-17

To control the time-response performance of widely used cerium-activated scintillators in cutting-edge medical-imaging devices, such as time-of-flight positron-emission tomography, a comprehensive understanding of the role of Ce valence states, especially stable Ce 4+, in the scintillation mechanism is essential. However, despite some progress made recently, an understanding of the physical processes involving Ce 4+ is still lacking. The aim of this work is to clarify the role of Ce 4+ in scintillators by studying Ca 2+ codoped Gd 3Ga 3Al 2O1 2∶Ce (GGAG∶Ce). By using a combination of optical absorption spectra and x-ray absorption near-edge spectroscopies, the correlation between Ca 2+codopingmore » content and the Ce 4+ fraction is seen. The energy-level diagrams of Ce 3+ and Ce 4+ in the Gd 3Ga 3Al 2O 12 host are established by using theoretical and experimental methods, which indicate a higher position of the 5d 1 state of Ce 4+ in the forbidden gap in comparison to that of Ce 3+. Underlying reasons for the decay-time acceleration resulting from Ca 2+ codoping are revealed, and the physical processes of the Ce 4+-emission model are proposed and further demonstrated by temperature-dependent radioluminescence spectra under x-ray excitation.« less

Role of Ce4+ in the Scintillation Mechanism of Codoped Gd3Ga3Al2O12∶Ce

NASA Astrophysics Data System (ADS)

Wu, Yuntao; Meng, Fang; Li, Qi; Koschan, Merry; Melcher, Charles L.

2014-10-01

To control the time-response performance of widely used cerium-activated scintillators in cutting-edge medical-imaging devices, such as time-of-flight positron-emission tomography, a comprehensive understanding of the role of Ce valence states, especially stable Ce44, in the scintillation mechanism is essential. However, despite some progress made recently, an understanding of the physical processes involving Ce4+ is still lacking. The aim of this work is to clarify the role of Ce4+ in scintillators by studying Ca2+ codoped Gd3Ga3Al2O12∶Ce (GGAG ∶Ce). By using a combination of optical absorption spectra and x-ray absorption near-edge spectroscopies, the correlation between Ca2+ codoping content and the Ce4+ fraction is seen. The energy-level diagrams of Ce3+ and Ce4+ in the Gd3Ga3Al2O12 host are established by using theoretical and experimental methods, which indicate a higher position of the 5d1 state of Ce4+ in the forbidden gap in comparison to that of Ce3+. Underlying reasons for the decay-time acceleration resulting from Ca2+ codoping are revealed, and the physical processes of the Ce4+-emission model are proposed and further demonstrated by temperature-dependent radioluminescence spectra under x-ray excitation.

Comparison between ray-tracing and physical optics for the computation of light absorption in capillaries--the influence of diffraction and interference.

PubMed

Qin, Yuan; Michalowski, Andreas; Weber, Rudolf; Yang, Sen; Graf, Thomas; Ni, Xiaowu

2012-11-19

Ray-tracing is the commonly used technique to calculate the absorption of light in laser deep-penetration welding or drilling. Since new lasers with high brilliance enable small capillaries with high aspect ratios, diffraction might become important. To examine the applicability of the ray-tracing method, we studied the total absorptance and the absorbed intensity of polarized beams in several capillary geometries. The ray-tracing results are compared with more sophisticated simulations based on physical optics. The comparison shows that the simple ray-tracing is applicable to calculate the total absorptance in triangular grooves and in conical capillaries but not in rectangular grooves. To calculate the distribution of the absorbed intensity ray-tracing fails due to the neglected interference, diffraction, and the effects of beam propagation in the capillaries with sub-wavelength diameter. If diffraction is avoided e.g. with beams smaller than the entrance pupil of the capillary or with very shallow capillaries, the distribution of the absorbed intensity calculated by ray-tracing corresponds to the local average of the interference pattern found by physical optics.

Broadband ultrafast nonlinear absorption and ultra-long exciton relaxation time of black phosphorus quantum dots.

PubMed

Chen, Runze; Zheng, Xin; Jiang, Tian

2017-04-03

Black phosphorus (BP) has recently attracted significant attention for its brilliant physical and chemical features. The remarkable strong light-matter interaction and tunable direct wide range band-gap make it an ideal candidate in various application regions, especially saturable absorbers. In this paper, ultrasmall black phosphorus quantum dots (BPQDs), a unique form of phosphorus nanostructures, with average size of 5.7 ± 0.8 nm are synthesized. Compared with BP nanosheets (BPNs) with similar thickness, the ultrafast nonlinear optical (NLO) absorption properties and excited carrier dynamics are investigated in wide spectra. Beyond the saturation absorption (SA), giant two photon absorption (TPA) is observed in BPQDs. BPQDs exhibit quite different excitation intensity and wavelength dependent nonlinear optical (NLO) response from BPNs, which is attributed to the quantum confinement and edge effects. The BPQDs show broadband photon-induced absorption (PIA) under the probe wavelength from 470 nm to 850 nm and a fast and a slow decay time are obtained as long as 92 ± 10 ps and 1100 ± 100 ps, respectively. The substantial independence for ultra-long time scales of pump intensity and temperature reveals that the carrier recombination mechanism may be attributed to a defect-assisted Auger capture process. These findings will help to develop optoelectronic and photonic devices operating in the infrared and visible wavelength region.

Study on detection of terrestrial and marine fractions in marine organic molecules by spectrophoto- and spectrofluorometric methods

NASA Astrophysics Data System (ADS)

Drozdowska, Violetta; Wróbel, Iwona; Piskozub, Jacek

2017-04-01

The sea surface is a highly productive and active interface between the sea and the atmosphere. Sea surface films are created by organic matter from sea and land sources and they dissipate due to loss of material at the sea surface, including microbial degradation, chemical and photo chemical processes, and loss due to absorption and adsorption onto particulates. However the surface microlayer is almost ubiquitous and cover most of the surface of the ocean, even under conditions of high turbulence. Surface active molecules (surfactants) present in the surface microlayer (SML) may modify the number of physical processes taking place there: among others they affect the depth of penetration of solar radiation and gas exchange. Therefore, research on the influence of surfactants on the sea surface properties become an important task, especially in coastal waters and in vicinity of the river mouths. Surfactants comprises a mixture of organic molecules rich in lipids, polymeric and humus whose proportions determine the various properties of the SML. A unique structure of the energy levels of the organic molecules results in a unique spectral distribution of the light intensity absorbed and emitted by the molecules. Hence, the absorption and fluorescence spectra of organic compounds may allow the identification of the sources of organic matter. Additionally, several absorption (E2:E3, S, SR) and fluorescence (fluorescence intensities at peaks: A, C, M, T, the ratio (M+T)/(A+C), HIX) indices help in describing the changes in molecular size and weight as well as composition of organic matter during the humification processes and caused by photobleaching and biodegradation. Investigations included the region of Gulf of Gdańsk, along a transect from the Vistula River outlet to open sea. The fluorescence and absorption measurements of the samples collected from a surface films and a subsurface layer (SS, a depth of 1 m) during three research cruises in Gulf of Gdańsk, the Baltic Sea, as well as hydrophysical studies and meteorological observations allowed to assess (i) the contribution of two terrestrial components (A and C) decreased with increasing salinity ( 1.64% and 1.89 % in SML and 0.78 and 0.71 % in SS, respectively), while the contribution of, in-situ, in the sea produced components (M and T) increased with salinity ( 0.52% and 2.83% in SML and 0.98% and 1.87 % in SS, respectively), (ii) the biggest relative changes of the FDOM component composition, along the transect from the Vistula River outlet to Gdańsk Deep, were recorded for component T, both in SML and SS (about 18.5 % and 12.3 %, respectively), (iii) the ratio E2:E3 points to discrete changes in molecular weight/size, effected by photobleaching, while (iv) HIX index reflects the humification/condensation processes more sensitively and effectively in SS. The organic molecules included in the SML can specifically modify the physical processes associated with the sea surface microlayers. It should be necessary to continue a study on the physical properties of surface microlayer in the future, especially in less urbanized and more natural and pristine region, like Arctic.

Ultraviolet Spectroscopy of Tidal Disruption Flares

NASA Astrophysics Data System (ADS)

Cenko, Stephen B.

2017-08-01

When a star passes within the sphere of disruption of a massive black hole, tidal forces will overcome self-gravity and unbind the star. While approximately half of the stellar debris is ejected at high velocities, the remaining material stays bound to the black hole and accretes, resulting in a luminous, long-lived transient known as a tidal disruption flare (TDF). In addition to serving as unique laboratories for accretion physics,TDFs offer the hope of measuring black hole masses in galaxies much too distant for resolved kinematic studies.In order to realize this potential, we must better understand the detailed processes by which the bound debris circularizes and forms an accretion disk. Spectroscopy is critical to this effort, as emission and absorption line diagnostics provide insight into the location and physical state (velocity, density, composition) of the emitting gas (in analogy with quasars). UV spectra are particularly critical, as most strong atomic features fall in this bandpass, and high-redshift TDF discoveries from LSST will sample rest-frame UV wavelengths.Here I present recent attempts to obtain UV spectra of tidal disruption flares. I describe the UV spectrum of ASASSN-14li, in which we detect three classes of features: narrow absorption from the Milky Way (probably a high-velocity cloud), and narrow absorption and broad (2000-8000 km s-1) emission lines at or near the systemic host velocity. The absorption lines are blueshifted with respect to the emission lines by 250-400 km s-1. Due both to this velocity offset and the lack of common low-ionization features (Mg II, Fe II), we argue these arise from the same absorbing material responsible for the low-velocity outflow discovered at X-ray wavelengths. The broad nuclear emission lines display a remarkable abundance pattern: N III], N IV], and He II are quite prominent, while the common quasar emission lines of C III] and Mg II are weak or entirely absent. Detailed modeling of this spectrum will help elucidate fundamental questions regarding the nature of the emission processes at work in TDFs, while future UV spectroscopy of ASASSN-14li would help to confirm (or refute) the previously proposed connection between TDFs and “N-rich” quasars.

ON THE DEGREE OF CONVERSION AND COEFFICIENT OF THERMAL EXPANSION OF A SINGLE FIBER COMPOSITE USING A FBG SENSOR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lai, M.; Botsis, J.; Coric, D.

2008-08-28

The increasing needs of extending the lifetime in high-technology fields, such as space and aerospace, rail transport and naval systems, require quality enhancing of the composite materials either from a processing standing point or in the sense of resistance to service conditions. It is well accepted that the final quality of composite materials and structures is strongly influenced by processing parameters like curing and post-curing temperatures, rate of heating and cooling, applied vacuum, etc. To optimize manufacturing cycles, residual strains evolution due to chemical shrinkage and other physical parameters of the constituent materials must be characterized in situ. Such knowledgemore » can lead to a sensible reduction in defects and to improved physical and mechanical properties of final products. In this context continuous monitoring of strains distribution developed during processing is important in understanding and retrieving components' and materials' characteristics such as local strains gradients, degree of curing, coefficient of thermal expansion, moisture absorption, etc.« less

A new look at low-energy nuclear reaction research.

PubMed

Krivit, Steven B; Marwan, Jan

2009-10-01

This paper presents a new look at low-energy nuclear reaction research, a field that has developed from one of the most controversial subjects in science, "cold fusion." Early in the history of this controversy, beginning in 1989, a strong polarity existed; many scientists fiercely defended the claim of new physical effects as well as a new process in which like-charged atomic nuclei overcome the Coulomb barrier at normal temperatures and pressures. Many other scientists considered the entire collection of physical observations-along with the hypothesis of a "cold fusion"--entirely a mistake. Twenty years later, some people who had dismissed the field in its entirety are considering the validity of at least some of the reported experimental phenomena. As well, some researchers in the field are wondering whether the underlying phenomena may be not a fusion process but a neutron capture/absorption process. In 2002, a related tabletop form of thermonuclear fusion was discovered in the field of acoustic inertial confinement fusion. We briefly review some of this work, as well.

Plasma flow reactor for steady state monitoring of physical and chemical processes at high temperatures.

PubMed

Koroglu, Batikan; Mehl, Marco; Armstrong, Michael R; Crowhurst, Jonathan C; Weisz, David G; Zaug, Joseph M; Dai, Zurong; Radousky, Harry B; Chernov, Alex; Ramon, Erick; Stavrou, Elissaios; Knight, Kim; Fabris, Andrea L; Cappelli, Mark A; Rose, Timothy P

2017-09-01

We present the development of a steady state plasma flow reactor to investigate gas phase physical and chemical processes that occur at high temperature (1000 < T < 5000 K) and atmospheric pressure. The reactor consists of a glass tube that is attached to an inductively coupled argon plasma generator via an adaptor (ring flow injector). We have modeled the system using computational fluid dynamics simulations that are bounded by measured temperatures. In situ line-of-sight optical emission and absorption spectroscopy have been used to determine the structures and concentrations of molecules formed during rapid cooling of reactants after they pass through the plasma. Emission spectroscopy also enables us to determine the temperatures at which these dynamic processes occur. A sample collection probe inserted from the open end of the reactor is used to collect condensed materials and analyze them ex situ using electron microscopy. The preliminary results of two separate investigations involving the condensation of metal oxides and chemical kinetics of high-temperature gas reactions are discussed.

Carbon Dioxide Absorption in a Membrane Contactor with Color Change

ERIC Educational Resources Information Center

Pantaleao, Ines; Portugal, Ana F.; Mendes, Adelio; Gabriel, Joaquim

2010-01-01

A pedagogical experiment is described to examine the physical absorption of gases, in this case carbon dioxide, in a hollow fiber membrane contactor (HFMC) where the absorption concentration profile can be followed by a color change. The HFMC is used to teach important concepts and can be used in interesting applications for students, such as…

The Reverse Thermal Effect in Epoxy Resins and Moisture Absorption in Semi-Interpenetrating Polymer Networks.

NASA Astrophysics Data System (ADS)

El-Sa'Ad, Leila

1989-12-01

Available from UMI in association with The British Library. Requires signed TDF. Epoxy resins exhibit many desirable properties which make them ideal subjects for use as matrices of composite materials in many commercial, military and space applications. However, due to their high cross-link density they are often brittle. Epoxy resin networks have been modified by incorporating tough, ductile thermoplastics. Such systems are referred to as Semi-Interpenetrating Polymer Networks (Semi-IPN). Systematic modification to the thermoplastics backbone allowed the morphology of the blend to be controlled from a homogeneous one-phase structure to fully separated structures. The moisture absorption by composites in humid environments has been found to lead to a deterioration in the physical and mechanical properties of the matrix. Therefore, in order to utilize composites to their full potential, their response to hot/wet environments must be known. The aims of this investigation were two-fold. Firstly, to study the effect of varying the temperature of exposure at different stages in the absorption process on the water absorption behaviour of a TGDDM/DDS epoxy resin system. Secondly, to study water absorption characteristics, under isothermal conditions, of Semi-Interpenetrating Polymer Networks possessing different morphologies, and develop a theoretical model to evaluate the diffusion coefficients of the two-phase structures. The mathematical treatment used in this analysis was based on Fick's second law of diffusion. Tests were performed on specimens immersed in water at 10 ^circ, 40^circ and 70^circC, their absorption behaviour and swelling behaviour, as a consequence of water absorption, were investigated. The absorption results of the variable temperature absorption tests indicated a saturation dependence on the absorption behaviour. Specimens saturated at a high temperature will undergo further absorption when transferred to a lower temperature. This behaviour was termed the "reverse thermal effect". The swelling results suggested that it is more tightly bound water in the polymer which takes part in the reverse thermal effect. The absorption results for the Semi-Interpenetrating Polymer Networks suggested that the two key parameters which affected the moisture uptake were the morphology of the network and the percentage of epoxy resin in the system.

The way to universal and correct medical presentation of diagnostic informations for complex spectrophotometry noninvasive medical diagnostic systems

NASA Astrophysics Data System (ADS)

Rogatkin, Dmitrii A.; Tchernyi, Vladimir V.

2003-07-01

The optical noninvasive diagnostic systems are now widely applied and investigated in different areas of medicine. One of the such techniques is the noninvasive spectrophotometry, the complex diagnostic technique consisting on elastic scattering spectroscopy, absorption spectroscopy, fluorescent diagnostics, photoplethismography, etc. Today a lot of real optical diagnostic systems indicate the technical parameters and physical data only as a result of the diagnostic procedure. But, it is clear that for the medical staff the more convenient medical information is needed. This presentation lights the general way for development a diagnostic system"s software, which can produce the full processing of the diagnostic data from a physical to a medical level. It is shown, that this process is a multilevel (3-level) procedure and the main diagnostic result for noninvasive spectrophotometry methods, the biochemical and morphological composition of the tested tissues, arises in it on a second level of calculations.

New insights on laser-induced graphene electrodes for flexible supercapacitors: tunable morphology and physical properties.

PubMed

Lamberti, Andrea; Perrucci, Francesco; Caprioli, Matteo; Serrapede, Mara; Fontana, Marco; Bianco, Stefano; Ferrero, Sergio; Tresso, Elena

2017-04-28

In certain polymers the graphenization of carbon atoms can be obtained by laser writing owing to the easy absorption of long-wavelength radiation, which generates photo-thermal effects. On a polyimide surface this process allows the formation of a nanostructured and porous carbon network known as laser-induced graphene (LIG). Herein we report on the effect of the process parameters on the morphology and physical properties of LIG nanostructures. We show that the scan speed and the frequency of the incident radiation affect the gas evolution, inducing different structure rearrangements, an interesting nitrogen self-doping phenomenon and consequently different conduction properties. The materials were characterized by infrared and Raman spectroscopy, XPS elemental analysis, electron microscopy and electrical/electrochemical measurements. In particular the samples were tested as interdigitated electrodes into electrochemical supercapacitors and the optimized LIG arrangement was tested in parallel and series supercapacitor configurations to allow power exploitation.

Analytical study of laser-supported combustion waves in hydrogen

NASA Technical Reports Server (NTRS)

Kemp, N. H.; Root, R. G.

1978-01-01

Laser supported combustion (LSC) waves are an important ingredient in the fluid mechanics of CW laser propulsion using a hydrogen propellant and 10.6 micron lasers. Therefore, a computer model has been constructed to solve the one-dimensional energy equation with constant pressure and area. Physical processes considered include convection, conduction, absorption of laser energy, radiation energy loss, and accurate properties of equilibrium hydrogen. Calculations for 1, 3, 10 and 30 atm were made for intensities of 10 to the 4th to 10 to the 6th W/sq cm, which gave temperature profiles, wave speed, etc. To pursue the propulsion application, a second computer model was developed to describe the acceleration of the gas emerging from the LSC wave into a variable-pressure, converging streamtube, still including all the above-mentioned physical processes. The results show very high temperatures in LSC waves which absorb all the laser energy, and high radiative losses.

Performance of nanocomposites for preservation of artistic stones

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giancristofaro, Cristina; Pilloni, Luciano; Rinaldi, Antonio

2014-06-19

In this work, the effectiveness of nanocomposite surface treatments as protective systems for artistic stones was evaluated. Pyrolitic silica and titania nanoparticles were dispersed in a commercial silicon-based polymer and applied on marble and travertine samples. Artificial aging processes, both in climatic chamber and in solar box, were carried out to simulate real degradation processes in terms of photo-thermal effects and physical-chemical damage. The performances of the nanocomposites used as consolidant were evaluated comparatively by means of diverse diagnostic techniques, namely: scanning electron microscopy (SEM), laser induced fluorescence (LIF), ultrasonic technique, colorimetry, total immersion water absorption and contact angle. Themore » results show that some properties of conservation materials can be improved by the presences of nanoparticles because they induce substantial changes of surface morphology of the coating layer and counter the physical damage observed during artificial weathering.« less

Proof-of-Concept Study: Novel Microbially-Driven Fenton Reaction for In Situ Remediation of Groundwater Contaminated with 1,4-Dioxane, Tetrachloroethene (PCE) and Trichloroethene (TCE)

DTIC Science & Technology

2014-09-17

technologies such as carbon absorption, air stripping, and distillation are limited by the physical properties of 1-4-dioxane. In the present study, a...and also to evaluate the ability of the novel degradation process to degrade perfluoroalkyl ( PFAS ) substances. 4 INTRODUCTION 1,4...miscible in water, displays low volatility, and is thus highly mobile in the environment. Current 1,4-dioxane remediation technologies such as carbon

Probing the chemical composition of the Z < 1 intergalactic medium with observations and simulations

NASA Astrophysics Data System (ADS)

Cooksey, Kathy L.

2009-09-01

Metals are produced in the stars in the galaxies, and a variety of feedback processes move metals from the sites of production into the intergalactic medium (IGM), enriching the material for future generations of stars. The signature of this process is etched in the recycled gas: its metallicity, elemental abundances, density, distribution, etc. The study of the low- redshift, z <, IGM is the study of the last eight-billion years of cosmic chemical evolution and all prior enrichment. In this thesis, I characterize the cosmic enrichment cycle with the use of observations and simulations. The gas is observed through quasar absorption- line spectroscopy. As the light of a distant quasar travels to us, intervening clouds of gas absorb the light at wavelengths characteristic, albeit redshifted, of the elements in the clouds. By identifying and modeling the elements associated with the absorption systems, I learn the ionic composition and density of the cosmic web (voids, filaments, and/or groups) along the line of sight. >From a detailed study of a single sightline, I observe a multi-phase IGM, with kinematically-distinct, hot and warm components ( T [approximate] 10 5.5 K and 10 4 K, respectively). By correlating the absorption systems with a complementary galaxy survey of the field around the background quasar, I find that the IGM systems arise in a variety of galactic environments. The metal- lines systems all have L > 0.1 L [low *] galaxies within a few hundred kiloparsecs, which suggests this is the distance to which galactic feedback processes typically disperse metals. I conduct a large, blind survey for triply-ionized carbon (C IV) absorption at z < 1 in the spectra of 49 low-redshift quasars and compare their propertie with those detected at z > 1. The mass density in C IV doublets with 13 < = log N (C +3 ) <= 15 at z < 1 has increased by a factor of 2.8 ± 0.7 over the error- weighted mean of the 1.5 < z < 5 measurements, where the mass density has not evolved significantly. The line density d[Special characters omitted.] /d X has not evolved as much, indicating that the average column density per doublet increases with decreasing redshift. In addition, I compare the observed properties of C IV absorbers with those predicted by cosmological hydrodynamic simulations with a variety of physical models (e.g., feedback, cosmology). I also use the results from the simulations that reproduce well the observations to understand better the physical conditions giving rise to the C IV absorbing gas. The observations and simulations indicate that the log N (C +3 ) > 13 C IV absorption systems predominately come from circum-galactic (or halo) gas.

Solid lipid nanoparticles for enhancing vinpocetine's oral bioavailability.

PubMed

Luo, YiFan; Chen, DaWei; Ren, LiXiang; Zhao, XiuLi; Qin, Jing

2006-08-10

An ultrasonic-solvent emulsification technique was adopted to prepare vinpocetine loaded Glyceryl monostearate (GMS) nanodispersions with narrow size distribution. To increase the lipid load the process was conducted at 50 degrees C, and in order to prepare nanoparticle using an ultrasonic-solvent emulsification technique. The mean particle size and droplet size distribution, drug loading capacity, drug entrapment efficiency (EE%), zeta potential, and long-term physical stability of the SLNs were investigated in detail respectively. Drug release from two sorts of VIN-SLN was studied using a dialysis bag method. A pharmacokinetic study was conducted in male rats after oral administration of 10 mg kg(-1) VIN in different formulations, it was found that the relative bioavailability of VIN in SLNs was significantly increased compared with that of the VIN solution. The amount of surfactant also had a marked effect on the oral absorption of VIN with SLN formulations. The absorption mechanism of the SLN formulations was also discussed. These results indicated that VIN absorption is enhanced significantly by employing SLN formulations. SLNs offer a new approach to improve the oral bioavailability of poorly soluble drugs.

Ablation dynamics - from absorption to heat accumulation/ultra-fast laser matter interaction

NASA Astrophysics Data System (ADS)

Kramer, Thorsten; Remund, Stefan; Jäggi, Beat; Schmid, Marc; Neuenschwander, Beat

2018-05-01

Ultra-short laser radiation is used in manifold industrial applications today. Although state-of-the-art laser sources are providing an average power of 10-100 W with repetition rates of up to several megahertz, most applications do not benefit from it. On the one hand, the processing speed is limited to some hundred millimeters per second by the dynamics of mechanical axes or galvanometric scanners. On the other hand, high repetition rates require consideration of new physical effects such as heat accumulation and shielding that might reduce the process efficiency. For ablation processes, process efficiency can be expressed by the specific removal rate, ablated volume per time, and average power. The analysis of the specific removal rate for different laser parameters, like average power, repetition rate or pulse duration, and process parameters, like scanning speed or material, can be used to find the best operation point for microprocessing applications. Analytical models and molecular dynamics simulations based on the so-called two-temperature model reveal the causes for the appearance of limiting physical effects. The findings of models and simulations can be used to take advantage and optimize processing strategies.

The Photo-Physics of Polythiophene Nanoparticles for Biological Applications.

PubMed

Bargigia, Ilaria; Zucchetti, Elena; Srimath Kandada, Ajay Ram; Moreira, Miguel; Bossio, Caterina; Wong, Walter; Miranda, Paulo; Decuzzi, Paolo; Soci, Cesare; D'Andrea, Cosimo; Lanzani, Guglielmo

2018-05-01

In this work the photo-physics of poly(3-hexyltiophene) nanoparticles (NPs) is investigated in the context of their biological applications. The NPs made as colloidal suspensions in aqueous buffers present a distinct absorption band in the low energy region. Based on systematic analysis of absorption and transient absorption spectra taken under different pH conditions, this band is associated to charge transfer states generated by the polarization of loosely bound polymer chains and originated from complexes formed with electron withdrawing species. Importantly, the ground state depletion of these states upon photo-excitation is active even in the microsecond timescales, suggesting that they act as precursor states for long-living polarons which could be beneficial for cellular stimulation. Preliminary results of transient absorption microscopy of NPs internalized within the cells reveal the presence of long-living species, further substantiating their relevance in bio-interfaces. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stress corrosion in titanium alloys and other metallic materials

NASA Technical Reports Server (NTRS)

Harkins, C. G. (Editor); Brotzen, F. R.; Hightower, J. W.; Mclellan, R. B.; Roberts, J. M.; Rudee, M. L.; Leith, I. R.; Basu, P. K.; Salama, K.; Parris, D. P.

1971-01-01

Multiple physical and chemical techniques including mass spectroscopy, atomic absorption spectroscopy, gas chromatography, electron microscopy, optical microscopy, electronic spectroscopy for chemical analysis (ESCA), infrared spectroscopy, nuclear magnetic resonance (NMR), X-ray analysis, conductivity, and isotopic labeling were used in investigating the atomic interactions between organic environments and titanium and titanium oxide surfaces. Key anhydrous environments studied included alcohols, which contain hydrogen; carbon tetrachloride, which does not contain hydrogen; and mixtures of alcohols and halocarbons. Effects of dissolved salts in alcohols were also studied. This program emphasized experiments designed to delineate the conditions necessary rather than sufficient for initiation processes and for propagation processes in Ti SCC.

Composite substrate for bipolar electrodes

DOEpatents

Tekkanat, Bora; Bolstad, James J.

1992-12-22

Substrates for electrode systems, particularly those to be used for bipolar electrodes in zinc-bromine batteries, are disclosed. The substrates preferably include carbon-black as a conductive filler in a polymeric matrix, with reinforcing materials such as glass fibers. Warpage of the zinc-bromine electrodes which was experienced in the prior art and which was believed to be caused by physical expansion of the electrodes due to bromine absorption by the carbon-black, is substantially eliminated when new substrate fabrication techniques are employed. In the pesent invention, substrates are prepared using a lamination process known as glass mat reinforced thermoplastics technology or, in an alternate embodiment, the substrate is made using a slurry process.

Therapeutic considerations of sarcopenia in heart failure patients.

PubMed

Saitoh, Masakazu; Ebner, Nicole; von Haehling, Stephan; Anker, Stefan D; Springer, Jochen

2018-02-01

Sarcopenia is a common feature, and affects 20-47% of patients with heart failure (HF). Sarcopenia is also an independent predictor of impaired functional capacity, even after adjusting for clinical relevant variables, which is associated with adverse outcome in patients with HF. Areas covered: Several different pathophysiological pathways are involved in sarcopenic processes including altered nutrient intake and absorption, hormonal factor, inflammatory processes, oxidative stress, cellular proteolysis, and unhealthy lifestyle. Nutritional therapy, physical activity and/or exercise training have been associated with improved muscle mass or physical performance in HF. Few studies reported beneficial effects for muscle mass and physical performance, in those who received angiotensin-converting enzyme (ACE) inhibitors, or/and beta-blocker. In addition, testosterone, selective androgen receptor modulators, ghrelin agonist and myostatin inhibitors are currently under study as possible future therapeutic options. Expert commentary: Regular and adequate level of physical activity and/or exercise training, and sufficient nutritional intake or special nutritional supplementation may represent the best strategy for prevention or delay of sarcopenia and worsening physical performance in patients with HF. Maximal tolerated dosages of standard therapies for HF such as ACE-inhibitors or beta-blockers are first-line strategy, however it is difficult to recommend other pharmacological agents as part of routine treatment of sarcopenia.

New insights into the molecular mechanism of intestinal fatty acid absorption

PubMed Central

Wang, Tony Y.; Liu, Min; Portincasa, Piero; Wang, David Q.-H.

2013-01-01

Background Dietary fat is the most important energy source of all the nutrients. Fatty acids, stored as triacylglycerols in the body, are an important reservoir of stored energy and derive primarily from animal fats and vegetable oils. Design Although the molecular mechanisms for the transport of water-insoluble amphipathic fatty acids across cell membranes have been debated for many years, it is now believed that the dominant means for intestinal fatty acid uptake is via membrane-associated fatty acid-binding proteins, i.e., fatty acid transporters on the apical membrane of enterocytes. Results These findings indicate that intestinal fatty acid absorption is a multistep process that is regulated by multiple genes at the enterocyte level, and intestinal fatty acid absorption efficiency could be determined by factors influencing intraluminal fatty acid molecules across the brush border membrane of enterocytes. To facilitate research on intestinal, hepatic and plasma triacylglycerol metabolism, it is imperative to establish standard protocols for precisely and accurately measuring the efficiency of intestinal fatty acid absorption in humans and animal models. In this review, we will discuss the chemical structure and nomenclature of fatty acids and summarize recent progress in investigating the molecular mechanisms underlying the intestinal absorption of fatty acids, with a particular emphasis on the physical-chemistry of intestinal lipids and the molecular physiology of intestinal fatty acid transporters. Conclusions A better understanding of the molecular mechanism of intestinal fatty acid absorption should lead to novel approaches to the treatment and the prevention of fatty acid-related metabolic diseases that are prevalent worldwide. PMID:24102389

Photo-physical properties and triplet-triplet absorption of platinum(II) acetylides in solid PMMA matrices

NASA Astrophysics Data System (ADS)

Glimsdal, Eirik; Westlund, Robert; Lindgren, Mikael

2009-05-01

Because of their strong nonlinear optical properties, Platinum(II) acetylides are investigated as potential chromophores for optical power limiting (OPL) applications. The strong excited state absorption and efficient intersystem crossing to the triplet states in these materials are desired properties for good OPL performance. We recently reported on OPL and photo-physical properties of Pt(II)-acetylide chromophores in solution, modified with thiophenyl or triazole groups. [R. Westlund et al. J. Mater. Chem. 18, 166 (2008); E. Glimsdal et al. Proc. SPIE 6740, 67400M (2007)] The chromophores were later incorporated into poly(methyl-methacrylate) (PMMA) glasses. A variety of doped organic solids were prepared, reaching concentrations of up to 13 wt% of the guest molecule. Raman spectra of the doped solid devices proved that the chemical structure of the nonlinear dyes remains intact upon the polymerization of the solid matrix. Luminescence spectra confirm that the basic photo-physical properties (absorption, emission and inter-system crossing) observed for the solute molecules in THF are maintained also in the solid state. In particular, the phosphorescence lifetime stays in the order of μs to ms, just as in the oxygen evacuated liquid samples. Also, the wavelength dependence and time-dynamics of the triplet absorption spectra of the dyes, dissolved in THF solution and dispersed in solid PMMA matrices, were investigated and compared. Ground state UV absorption spectra between 300 and 420 nm have corresponding broad band visible triplet-triplet absorption between 400 and 800 nm. The triplet state extinction coefficients were determined to be in the order of 104 M-1cm-1.

Infrared band absorptance correlations and applications to nongray radiation. [mathematical models of absorption spectra for nongray atmospheres in order to study air pollution

NASA Technical Reports Server (NTRS)

Tiwari, S. N.; Manian, S. V. S.

1976-01-01

Various mathematical models for infrared radiation absorption spectra for atmospheric gases are reviewed, and continuous correlations for the total absorptance of a wide band are presented. Different band absorptance correlations were employed in two physically realistic problems (radiative transfer in gases with internal heat source, and heat transfer in laminar flow of absorbing-emitting gases between parallel plates) to study their influence on final radiative transfer results. This information will be applied to the study of atmospheric pollutants by infrared radiation measurement.

Role of the phase-matching condition in nondegenerate four-wave mixing in hot vapors for the generation of squeezed states of light

NASA Astrophysics Data System (ADS)

Turnbull, M. T.; Petrov, P. G.; Embrey, C. S.; Marino, A. M.; Boyer, V.

2013-09-01

Nondegenerate forward four-wave mixing in hot atomic vapors has been shown to produce strong quantum correlations between twin beams of light [McCormick , Opt. Lett.OPLEDP0146-959210.1364/OL.32.000178 32, 178 (2007)], in a configuration which minimizes losses by absorption. In this paper, we look at the role of the phase-matching condition in the trade-off that occurs between the efficiency of the nonlinear process and the absorption of the twin beams. To this effect, we develop a semiclassical model by deriving the atomic susceptibilities in the relevant double-Λ configuration and by solving the classical propagation of the twin-beam fields for parameters close to those found in typical experiments. These theoretical results are confirmed by a simple experimental study of the nonlinear gain experienced by the twin beams as a function of the phase mismatch. The model shows that the amount of phase mismatch is key to the realization of the physical conditions in which the absorption of the twin beams is minimized while the cross coupling between the twin beams is maintained at the level required for the generation of strong quantum correlations. The optimum is reached when the four-wave mixing process is not phase matched for fully resonant four-wave mixing.

Modification of fish skin collagen film and absorption property of tannic acid.

PubMed

Liu, Haiying; Zhao, Lu; Guo, Shidong; Xia, Yu; Zhou, Peng

2014-06-01

Fish collagen is a biomacromolecule material and is usually used as a clarifying agent. However, fish collagen is not recyclable, and sedimentation usually occurs in the clarification process using fish collagen so that the filtration process is inevitable. This work aimed to provide a recyclable modified fish skin collagen film (MFCF) for adsorption of tannic acids. The collagen from channel catfish skin was extracted and used for preparation of the fish skin collagen film (FCF) and MFCF. The result indicated that the mechanical properties of MFCF were improved by addition of 2 ml/L glycerol, 6 ml/L polyvinyl alcohol (PVA) and 2 ml/L glutaraldehyde in 15 g/L collagen solution. As the most important property of adsorption material, the hydroscopicity of MFCF was only 54%, significantly lower than that of FCF (295%). Therefore, MFCF would not collapse in water. The infrared and thermal properties of MFCF were also investigated in this work. Results indicated that, in comparison to FCF, the physical and chemical properties of MFCF had been improved significantly. MFCF had higher shrink temperature (79.3 °C) and it did not collapse in distilled water at normal temperature. Furthermore, absorption and desorption properties of tannic acid were studied. MFCF showed good capability of absorption and desorption of tannic acid, which leaded to the suggestion that MFCF could have potential applications in adsorption material.

Diffraction and quantum control of wave functions in nonresonant two-photon absorption

NASA Astrophysics Data System (ADS)

Li, Baihong; Pang, Huafeng; Wang, Doudou; Zhang, Tao; Dong, Ruifang; Li, Yongfang

2018-03-01

In this study, the nonresonant two-photon absorption process in a two-level atom, induced by a weak chirped pulse, is theoretically investigated in the frequency domain. An analytical expression of the wave function expressed by Fresnel functions is obtained, and the two-photon transition probability (TPTP) versus the integral bandwidth, spectral width, and chirp parameter is analyzed. The results indicate that the oscillation evolution of the TPTP result from quantum diffraction of the wave function, which can be explained by analogy with Fresnel diffraction from a wide slit in the spatial domain. Moreover, the ratio between the real and imaginary parts of the excited state wave function and, hence, the atomic polarization, can be controlled by the initial phase of the excitation pulse. In some special initial phase of the excitation pulse, the wave functions with purely real or imaginary parts can be obtained by measuring the population probability. This work provides a novel perspective for understanding the physical details of the interactions between atoms and chirped light pulses in the multiphoton process.

Physical Conditions of Eta Car Complex Environment Revealed From Photoionization Modeling

NASA Technical Reports Server (NTRS)

Verner, E. M.; Bruhweiler, F.; Nielsen, K. E.; Gull, T.; Kober, G. Vieira; Corcoran, M.

2006-01-01

The very massive star, Eta Carinae, is enshrouded in an unusual complex environment of nebulosities and structures. The circumstellar gas gives rise to distinct absorption and emission components at different velocities and distances from the central source(s). Through photoionization modeling, we find that the radiation field from the more massive B-star companion supports the low ionization structure throughout the 5.54 year period. The radiation field of an evolved O-star is required to produce the higher ionization . emission seen across the broad maximum. Our studies utilize the HST/STIS data and model calculations of various regimes from doubly ionized species (T= 10,000K) to the low temperature (T = 760 K) conditions conductive to molecule formation (CH and OH). Overall analysis suggests the high depletion in C and O and the enrichment in He and N. The sharp molecular and ionic absorptions in this extensively CNO - processed material offers a unique environment for studying the chemistry, dust formation processes, and nucleosynthesis in the ejected layers of a highly evolved massive star.

Distributed information system on molecular spectroscopy

NASA Astrophysics Data System (ADS)

Bykov, A. D.; Fazliev, A. Z.; Kozodoev, A. V.; Privezentsev, A. I.; Sinitsa, L. N.; Tonkov, M. V.; Filippov, N. N.; Tretyakov, M. Yu.

2006-12-01

The urgency of creating the information-computational systems (ICS) on molecular spectroscopy follows from the circumstance that for some molecules the number of calculated energy levels counts hundreds of thousands, and the number of spectral lines sometimes reaches hundreds of millions. Publication of such data volumes in regular journals is inappropriate. Comparison of different calculated spectral characteristics or their comparison with experimental data beyond computer processing is hopeless. We find information systems to be an adequate form for holding such data volumes and a toolkit for handling them. Correct digital data processing requires appropriate sets of metadata arranged in the form of ontology of molecular spectroscopy. Our information system provides the data on spectral line parameters, water molecule energy levels, and absorption coefficients. Within this distributed IS one can solve two types of problems: manipulation with data and calculation of spectral functions. Among the latest experimental data in the IS there are data obtained at the Institute of Applied Physics RAS. To calculate the absorption coefficients for the molecules of carbonic acid gas, we take into consideration spectral line interference.

Intestinal Permeability of β-Lapachone and Its Cyclodextrin Complexes and Physical Mixtures.

PubMed

Mangas-Sanjuan, Victor; Gutiérrez-Nieto, Jorge; Echezarreta-López, Magdalena; González-Álvarez, Isabel; González-Álvarez, Marta; Casabó, Vicente-Germán; Bermejo, Marival; Landin, Mariana

2016-12-01

β-Lapachone (βLAP) is a promising, poorly soluble, antitumoral drug. βLAP combination with cyclodextrins (CDs) improves its solubility and dissolution but there is not enough information about the impact of cyclodextrins on βLAP intestinal permeability. The objectives of this work were to characterize βLAP intestinal permeability and to elucidate cyclodextrins effect on the dissolution properties and on the intestinal permeability. The final goal was to evaluate CDs influence on the oral absorption of βLAP. Binary systems (physical mixtures and inclusion complexes) including βLAP and CDs (β-cyclodextrin: βCD, random-methyl-β-cyclodextrin: RMβCD and sulfobutylether-β-cyclodextrin: SBEβCD) have been prepared and analysed by differential scanning calorimetry. βLAP (and its combinations with CDs) absorption rate coefficients and effective permeability values have been determined in vitro in MDCK or MDCK-Mdr1 monolayers and in situ in rat by a closed loop perfusion technique. DSC results confirmed the formation of the inclusion complexes. βLAP-CDs inclusion complexes improve drug solubility and dissolution rate in comparison with physical mixtures. βLAP presented a high permeability value which can provide complete oral absorption. Its oral absorption is limited by its low solubility and dissolution rate. Cyclodextrin (both as physical mixtures and inclusion complexes) showed a positive effect on the intestinal permeability of βLAP. Complexation with CDs does not reduce βLAP intestinal permeability in spite of the potential negative effect of the reduction in free fraction of the drug. The use of RMβCD or SBEβCD inclusion complexes could benefit βLAP oral absorption by enhancing its solubility, dissolution rate and permeability.

Effect of natural Bayah zeolite particle size reduction to physico-chemical properties and absortion against potassium permanganate (KMnO4)

NASA Astrophysics Data System (ADS)

Widayanti, Siti Mariana; Syamsu, Khaswar; Warsiki, Endang; Yuliani, Sri

2016-02-01

Recently, researches on nanotechnology have been developed very rapid, as well as the utilization of nano-zeolites. Nano-sized material has several advantages which are expanding absorptive surfaces so it will enhance the material absorption and shorten the absorption time. Zeolite as a KMnO4 binder, has been widely recognized for its ability to extend the shelf life of vegetables and fruits. This study was conducted to determine zeolites physico-chemical characters from different particle size and the effect on KMnO4 absorption. Potassium permanganate (KMnO4) is a strong oxidizer for reducing the quantity of ethylene in storage process of fresh horticultural products. The treatment consisted of (1) different length of milling time (10, 20, 30, 40, and 60 minutes) and (2) the duration of chemical activation with 1 N KOH solution. Physical and chemical characters of zeolite were analyzed using BET, PSA, XRD and SEM. The research design was randomized design. The result implied that milling time was significantly affecting the zeolite particle size, material surface area, and the size of pore diameter and volume. Milling treatment for 40 minutes produced higher zeolite surface area and pore volume than other treatments. While the duration of chemical activation using 1 N KOH solution gives different effect on zeolite absorption to KMnO4 solution. Milling time for 60 minutes and activated for 48 hours has higher initial adsorption than other treatments.

Towards a fully kinetic 3D electromagnetic particle-in-cell model of streamer formation and dynamics in high-pressure electronegative gases

NASA Astrophysics Data System (ADS)

Rose, D. V.; Welch, D. R.; Clark, R. E.; Thoma, C.; Zimmerman, W. R.; Bruner, N.; Rambo, P. K.; Atherton, B. W.

2011-09-01

Streamer and leader formation in high pressure devices is dynamic process involving a broad range of physical phenomena. These include elastic and inelastic particle collisions in the gas, radiation generation, transport and absorption, and electrode interactions. Accurate modeling of these physical processes is essential for a number of applications, including high-current, laser-triggered gas switches. Towards this end, we present a new 3D implicit particle-in-cell simulation model of gas breakdown leading to streamer formation in electronegative gases. The model uses a Monte Carlo treatment for all particle interactions and includes discrete photon generation, transport, and absorption for ultra-violet and soft x-ray radiation. Central to the realization of this fully kinetic particle treatment is an algorithm that manages the total particle count by species while preserving the local momentum distribution functions and conserving charge [D. R. Welch, T. C. Genoni, R. E. Clark, and D. V. Rose, J. Comput. Phys. 227, 143 (2007)]. The simulation model is fully electromagnetic, making it capable of following, for example, the evolution of a gas switch from the point of laser-induced localized breakdown of the gas between electrodes through the successive stages of streamer propagation, initial electrode current connection, and high-current conduction channel evolution, where self-magnetic field effects are likely to be important. We describe the model details and underlying assumptions used and present sample results from 3D simulations of streamer formation and propagation in SF6.

[Dynamics of quickly absorption of the carbon source in wastewater by activated sludge].

PubMed

Liu, Hong-Bo; Wen, Xiang-Hua; Zhao, Fang

2011-09-01

In this paper, absorption characteristics of organic matter in municipal wastewater by three kinds of activated sludge (carbon-enriching, nitrification and denitrification sludge) were studied, and the absorption kinetic data was checked using three kinds of absorption kinetic equations based on Ritchie rate equation. The objectives of this study were to investigate the absorption mechanism of activated sludge to organic matter in municipal wastewater, and to identify the possibility of reclaiming organic matter by activated sludge. Results indicated that in the early 30 min, absorption process of organic matter by activated sludge was found to be mainly physical adsorption, which could be expressed by the Lagergren single-layer adsorption model. The carbon-enriching sludge had the highest adsorption capacity (COD/SS) which was 60 mg/g but the adsorption rate was lower than that of denitrification sludge. While nitrification sludge had the lowest adsorption rate and higher adsorption capacity compared with denitrification sludge, which was about 35 mg/g. The rates of the fitting index theta(0) of carbon-enriching, nitrification and denitrification sludge were 0.284, 0.777 and 0.923, respectively, which indicated that the sorbed organic matter on the surface of carbon-enriching sludge was the easiest fraction to be washed away. That is, the combination intensity of carbon-enriching sludge and organic matter was the feeblest, which was convenient for carbon-enriching sludge to release sorbed carbon. Furthermore, by fitting with Langmuir model, concentration of organic matter was found to be the key parameter influencing the adsorption capacity of activated sludge, while the influence of temperature was not obvious. The kinetic law of organic matter absorption by activated sludge was developed, which introduces a way to kinetically analyze the removing mechanism of pollutant by activated sludge and provides theoretical base for the reclaiming of nutriments in wastewater by the absorption of activated sludge.

The synthesis and the chemical and physical properties of non-aqueous silylamine solvents for carbon dioxide capture.

PubMed

Rohan, Amy L; Switzer, Jackson R; Flack, Kyle M; Hart, Ryan J; Sivaswamy, Swetha; Biddinger, Elizabeth J; Talreja, Manish; Verma, Manjusha; Faltermeier, Sean; Nielsen, Paul T; Pollet, Pamela; Schuette, George F; Eckert, Charles A; Liotta, Charles L

2012-11-01

Silylamine reversible ionic liquids were designed to achieve specific physical properties in order to address effective CO₂ capture. The reversible ionic liquid systems reported herein represent a class of switchable solvents where a relatively non-polar silylamine (molecular liquid) is reversibly transformed to a reversible ionic liquid (RevIL) by reaction with CO₂ (chemisorption). The RevILs can further capture additional CO₂ through physical absorption (physisorption). The effects of changes in structure on (1) the CO₂ capture capacity (chemisorption and physisorption), (2) the viscosity of the solvent systems at partial and total conversion to the ionic liquid state, (3) the energy required for reversing the CO₂ capture process, and (4) the ability to recycle the solvents systems are reported. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

AGIS -- the Advanced Gamma-ray Imaging System

NASA Astrophysics Data System (ADS)

Krennrich, Frank

2009-05-01

The Advanced Gamma-ray Imaging System, AGIS, is envisioned to become the follow-up mission of the current generation of very high energy gamma-ray telescopes, namely, H.E.S.S., MAGIC and VERITAS. These instruments have provided a glimpse of the TeV gamma-ray sky, showing more than 70 sources while their detailed studies constrain a wealth of physics and astrophysics. The particle acceleration, emission and absorption processes in these sources permit the study of extreme physical conditions found in galactic and extragalactic TeV sources. AGIS will dramatically improve the sensitivity and angular resolution of TeV gamma-ray observations and therefore provide unique prospects for particle physics, astrophysics and cosmology. This talk will provide an overview of the science drivers, scientific capabilities and the novel technical approaches that are pursued to maximize the performance of the large array concept of AGIS.

Physical preparation and optical properties of CuSbS2 nanocrystals by mechanical alloying process

NASA Astrophysics Data System (ADS)

Zhang, Huihui; Xu, Qishu; Tan, Guolong

2016-09-01

CuSbS2 nanocrystals have been synthesized through mechanical alloying Cu, Sb and S elemental powders for 40 hs. The optical spectrum of as-milled CuSbS2 nano-powders demonstrates a direct gap of 1.35 eV and an indirect gap of 0.36 eV, which are similar to that of silicon and reveals the evidence for the indirect semiconductor characterization of CuSbS2. Afterwards, CuSbS2 nanocrystals were capped with trioctylphosphine oxide/trioctylphosphine/pyridine (TOPO/TOP). There appear four sharp absorption peaks within the region of 315 to 355 nm for the dispersion solution containing the capped nanocrystals. The multiple peaks are proposed to be originating from the energy level splitting of 1S electronic state into four discrete sub-levels, where electrons were excited into the conduction band and thus four exciton absorption peaks were produced.

Broadband, high-resolution investigation of advanced absorption line shapes at high temperature

NASA Astrophysics Data System (ADS)

Schroeder, Paul J.; Cich, Matthew J.; Yang, Jinyu; Swann, William C.; Coddington, Ian; Newbury, Nathan R.; Drouin, Brian J.; Rieker, Gregory B.

2017-08-01

Spectroscopic studies of planetary atmospheres and high-temperature processes (e.g., combustion) require absorption line-shape models that are accurate over extended temperature ranges. To date, advanced line shapes, like the speed-dependent Voigt and Rautian profiles, have not been tested above room temperature with broadband spectrometers. We investigate pure water vapor spectra from 296 to 1305 K acquired with a dual-frequency comb spectrometer spanning from 6800 to 7200 c m-1 at a point spacing of 0.0033 c m-1 and absolute frequency accuracy of <3.3 ×10-6c m-1 . Using a multispectral fitting analysis, we show that only the speed-dependent Voigt accurately models this temperature range with a single power-law temperature-scaling exponent for the broadening coefficients. Only the data from the analysis using this profile fall within theoretical predictions, suggesting that this mechanism captures the dominant narrowing physics for these high-temperature conditions.

Microscopic Theory and Simulation of Quantum-Well Intersubband Absorption

NASA Technical Reports Server (NTRS)

Li, Jianzhong; Ning, C. Z.

2004-01-01

We study the linear intersubband absorption spectra of a 15 nm InAs quantum well using the intersubband semiconductor Bloch equations with a three-subband model and a constant dephasing rate. We demonstrate the evolution of intersubband absorption spectral line shape as a function of temperature and electron density. Through a detailed examination of various contributions, such as the phase space filling effects, the Coulomb many-body effects and the non-parabolicity effect, we illuminate the underlying physics that shapes the spectra. Keywords: Intersubband transition, linear absorption, semiconductor heterostructure, InAs quantum well

Application of tunable diode laser absorption spectroscopy in the detection of oxygen

NASA Astrophysics Data System (ADS)

Zhou, Xin; Jin, Xing

2015-10-01

Most aircrafts is driven by chemic energy which is released in the combustion process. For improving the capability of engine and controlling the running on-time, the processes of fuel physics and chemistry need to be analysis by kinds of high quality sensor. In the research of designing and improving the processes of fuel physics and chemistry, the concentration, temperature and velocity of kinds of gas in the combustor need to be detected and measured. In addition, these engines and research equipments are always in the harsh environment of high temperature, high pressure and high speed. The harsh environment needs the sensor to be high reliability, well repetition, no cross- sensitivity between gases, and the traditional measurement system can't satisfy the metrical requirement well. Tunable diode laser absorption spectroscopy (TDLAS) analytic measurement technology can well satisfy the measurement in the harsh environment, which can support the whole measurement plan and high quality measurement system. Because the TDLAS sensor has the excellence of small bulk, light weight, high reliability and well specifically measurement, the TDLAS measurement technology has wide prospects. Different from most measurements, only a beam of laser can be pass through the measured environment by TDLAS, and the measurement equipment needn't be set in the harsh environment. So, the TDLAS equipment can't be interrupted by the measured equipment. The ability of subsistence in the harsh environment is very valuable, especially in the measurement on the subject of aerospace with environment of high speed, combustion and plasma. This paper focuses on the collecting the articles on the subject of oxygen detection of TDLAS. By analyzing the research and results of the articles, we conclude the central issues, difficulties and results. And we can get some instructive conclusions.

Photo-ignition process of multiwall carbon nanotubes and ferrocene by continuous wave Xe lamp illumination.

PubMed

Visconti, Paolo; Primiceri, Patrizio; Longo, Daniele; Strafella, Luciano; Carlucci, Paolo; Lomascolo, Mauro; Cretì, Arianna; Mele, Giuseppe

2017-01-01

This work aims to investigate and characterize the photo-ignition phenomenon of MWCNT/ferrocene mixtures by using a continuous wave (CW) xenon (Xe) light source, in order to find the power ignition threshold by employing a different type of light source as was used in previous research (i.e., pulsed Xe lamp). The experimental photo-ignition tests were carried out by varying the weight ratio of the used mixtures, luminous power, and wavelength range of the incident Xe light by using selective optical filters. For a better explanation of the photo-induced ignition process, the absorption spectra of MWCNT/ferrocene mixtures and ferrocene only were obtained. The experimental results show that the luminous power (related to the entire spectrum of the Xe lamp) needed to trigger the ignition of MWCNT/ferrocene mixtures decreases with increasing metal nanoparticles content according to previously published results when using a different type of light source (i.e., pulsed vs CW Xe light source). Furthermore, less light power is required to trigger photo-ignition when moving towards the ultraviolet (UV) region. This is in agreement with the measured absorption spectra, which present higher absorption values in the UV-vis region for both MWCNT/ferrocene mixtures and ferrocene only diluted in toluene. Finally, a chemo-physical interpretation of the ignition phenomenon is proposed whereby ferrocene photo-excitation, due to photon absorption, produces ferrocene itself in its excited form and is thus capable of promoting electron transfer to MWCNTs. In this way, the resulting radical species, FeCp2 +∙ and MWCNT - , easily react with oxygen giving rise to the ignition of MWCNT/ferrocene samples.

Photo-ignition process of multiwall carbon nanotubes and ferrocene by continuous wave Xe lamp illumination

PubMed Central

Primiceri, Patrizio; Longo, Daniele; Strafella, Luciano; Carlucci, Paolo; Lomascolo, Mauro; Cretì, Arianna; Mele, Giuseppe

2017-01-01

This work aims to investigate and characterize the photo-ignition phenomenon of MWCNT/ferrocene mixtures by using a continuous wave (CW) xenon (Xe) light source, in order to find the power ignition threshold by employing a different type of light source as was used in previous research (i.e., pulsed Xe lamp). The experimental photo-ignition tests were carried out by varying the weight ratio of the used mixtures, luminous power, and wavelength range of the incident Xe light by using selective optical filters. For a better explanation of the photo-induced ignition process, the absorption spectra of MWCNT/ferrocene mixtures and ferrocene only were obtained. The experimental results show that the luminous power (related to the entire spectrum of the Xe lamp) needed to trigger the ignition of MWCNT/ferrocene mixtures decreases with increasing metal nanoparticles content according to previously published results when using a different type of light source (i.e., pulsed vs CW Xe light source). Furthermore, less light power is required to trigger photo-ignition when moving towards the ultraviolet (UV) region. This is in agreement with the measured absorption spectra, which present higher absorption values in the UV–vis region for both MWCNT/ferrocene mixtures and ferrocene only diluted in toluene. Finally, a chemo-physical interpretation of the ignition phenomenon is proposed whereby ferrocene photo-excitation, due to photon absorption, produces ferrocene itself in its excited form and is thus capable of promoting electron transfer to MWCNTs. In this way, the resulting radical species, FeCp2+∙ and MWCNT−, easily react with oxygen giving rise to the ignition of MWCNT/ferrocene samples. PMID:28144572

Semi-solid dosage form of clonazepam for rapid oral mucosal absorption.

PubMed

Sakata, Osamu; Machida, Yoshiharu; Onishi, Hiraku

2011-07-01

In order to obtain an alternative to the intravenous (i.v.) dosage form of clonazepam (CZ), an oral droplet formulation of CZ was developed previously; however, the droplet was physically unstable. Therefore, in the present study, it was attempted to develop an easily-handled dosage form, which was more physically stable and allowed rapid drug absorption from oral mucosa. A semi-solid dosage form, composed of polyethylene glycol 1500 (PEG), CZ, and oleic acid (OA) at 37/1/2 (w/w) and named PEG/CZ/OA, and a semi-solid dosage form containing PEG and CZ at 39/1 (w/w), called PEG/CZ, were prepared. Their physical stability in air at room temperature and oral mucosal absorption in rats were investigated. The semi-solid dosage forms were much more stable physically than the droplet, that is, no recrystallization of CZ was observed for at least 8 days. The effective concentration for humans and rats (20 ng/mL or more) was achieved within 30 min after buccal administration for both PEG/CZ/OA and PEG/CZ. The plasma concentration increased gradually and less varied at each time point for PEG/CZ/OA. PEG/CZ/OA was found to show more rapid and higher absorption of CZ in buccal administration than in sublingual administration. Buccal administration with the semi-solid dosage PEG/CZ with or without OA was suggested to be a possibly useful novel dosage form as an alternative to i.v. injection.

New insights into the molecular mechanism of intestinal fatty acid absorption.

PubMed

Wang, Tony Y; Liu, Min; Portincasa, Piero; Wang, David Q-H

2013-11-01

Dietary fat is one of the most important energy sources of all the nutrients. Fatty acids, stored as triacylglycerols (also called triglycerides) in the body, are an important reservoir of stored energy and derived primarily from animal fats and vegetable oils. Although the molecular mechanisms for the transport of water-insoluble amphipathic fatty acids across cell membranes have been debated for many years, it is now believed that the dominant means for intestinal fatty acid uptake is via membrane-associated fatty acid-binding proteins, that is, fatty acid transporters on the apical membrane of enterocytes. These findings indicate that intestinal fatty acid absorption is a multistep process that is regulated by multiple genes at the enterocyte level, and intestinal fatty acid absorption efficiency could be determined by factors influencing intraluminal fatty acid molecules across the brush border membrane of enterocytes. To facilitate research on intestinal, hepatic and plasma triacylglycerol metabolism, it is imperative to establish standard protocols for precisely and accurately measuring the efficiency of intestinal fatty acid absorption in humans and animal models. In this review, we will discuss the chemical structure and nomenclature of fatty acids and summarize recent progress in investigating the molecular mechanisms underlying the intestinal absorption of fatty acids, with a particular emphasis on the physical chemistry of intestinal lipids and the molecular physiology of intestinal fatty acid transporters. A better understanding of the molecular mechanism of intestinal fatty acid absorption should lead to novel approaches to the treatment and the prevention of fatty acid-related metabolic diseases that are prevalent worldwide. © 2013 Stichting European Society for Clinical Investigation Journal Foundation. Published by John Wiley & Sons Ltd.

The effect of age on systemic absorption and systemic disposition of bupivacaine after subarachnoid administration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Veering, B.T.; Burm, A.G.; Vletter, A.A.

1991-02-01

In order to evaluate the role of the pharmacokinetics of the age-related changes in the clinical profile of spinal anesthesia with bupivacaine, we studied the influence of age on the systemic absorption and systemic disposition of bupivacaine after subarachnoid administration in 20 male patients (22-81 yr), ASA Physical Status 1 or 2, by a stable isotope method. After subarachnoid administration of 3 ml 0.5% bupivacaine in 8% glucose, a deuterium-labeled analog (13.4 mg) was administered intravenously. Blood samples were collected for 24 h. Plasma concentrations of unlabeled and deuterium-labeled bupivacaine were determined with a combination of gas chromatography and massmore » fragmentography. Biexponential functions were fitted to the plasma concentration-time data of the deuterium-labeled bupivacaine. The systemic absorption was evaluated by means of deconvolution. Mono- and biexponential functions were fitted to the data of fraction absorbed versus time. The maximal height of analgesia and the duration of analgesia at T12 increased with age (r = 0.715, P less than 0.001; r = 0.640, P less than 0.01, respectively). In 18 patients the systemic absorption of bupivacaine was best described by a biexponential equation. The half-life of the slow systemic absorption process (r = -0.478; P less than 0.05) and the mean absorption time (r = -0.551; P less than 0.02) decreased with age. The total plasma clearance decreased with age (r = -0.650, P less than 0.002), whereas the mean residence time and terminal half-life increased with age (r = 0.597, P less than 0.01; r = 0.503, P less than 0.05).« less

Time-of-day-dependent global distribution of lunar surficial water/hydroxyl.

PubMed

Wöhler, Christian; Grumpe, Arne; Berezhnoy, Alexey A; Shevchenko, Vladislav V

2017-09-01

A new set of time-of-day-dependent global maps of the lunar near-infrared water/hydroxyl (H 2 O/OH) absorption band strength near 2.8 to 3.0 μm constructed on the basis of Moon Mineralogy Mapper (M 3 ) data is presented. The analyzed absorption band near 2.8 to 3.0 μm indicates the presence of surficial H 2 O/OH. To remove the thermal emission component from the M 3 reflectance spectra, a reliable and physically realistic mapping method has been developed. Our maps show that lunar highlands at high latitudes show a stronger H 2 O/OH absorption band in the lunar morning and evening than at midday. The amplitude of these time-of-day-dependent variations decreases with decreasing latitude of the highland regions, where below about 30°, absorption strength becomes nearly constant during the lunar day at a similar level as in the high-latitude highlands at midday. The lunar maria exhibit weaker H 2 O/OH absorption than the highlands at all, but showing a smaller difference from highlands absorption levels in the morning and evening than at midday. The level around midday is generally higher for low-Ti than for high-Ti mare surfaces, where it reaches near-zero values. Our observations contrast with previous studies that indicate a significant concentration of surficial H 2 O/OH at high latitudes only. Furthermore, although our results generally support the commonly accepted mechanism of H 2 O/OH formation by adsorption of solar wind protons, they suggest the presence of a more strongly bounded surficial H 2 O/OH component in the lunar highlands and parts of the mare regions, which is not removed by processes such as diffusion/thermal evaporation and photolysis in the course of the lunar day.

Finite Element Analysis of Interaction of Laser Beam with Material in Laser Metal Powder Bed Fusion Process.

PubMed

Fu, Guang; Zhang, David Z; He, Allen N; Mao, Zhongfa; Zhang, Kaifei

2018-05-10

A deep understanding of the laser-material interaction mechanism, characterized by laser absorption, is very important in simulating the laser metal powder bed fusion (PBF) process. This is because the laser absorption of material affects the temperature distribution, which influences the thermal stress development and the final quality of parts. In this paper, a three-dimensional finite element analysis model of heat transfer taking into account the effect of material state and phase changes on laser absorption is presented to gain insight into the absorption mechanism, and the evolution of instantaneous absorptance in the laser metal PBF process. The results showed that the instantaneous absorptance was significantly affected by the time of laser radiation, as well as process parameters, such as hatch space, scanning velocity, and laser power, which were consistent with the experiment-based findings. The applicability of this model to temperature simulation was demonstrated by a comparative study, wherein the peak temperature in fusion process was simulated in two scenarios, with and without considering the effect of material state and phase changes on laser absorption, and the simulated results in the two scenarios were then compared with experimental data respectively.

Composite substrate for bipolar electrodes

DOEpatents

Tekkanat, B.; Bolstad, J.J.

1992-12-22

Substrates for electrode systems, particularly those to be used for bipolar electrodes in zinc-bromine batteries, are disclosed. The substrates preferably include carbon-black as a conductive filler in a polymeric matrix, with reinforcing materials such as glass fibers. Warpage of the zinc-bromine electrodes which was experienced in the prior art and which was believed to be caused by physical expansion of the electrodes due to bromine absorption by the carbon-black, is substantially eliminated when new substrate fabrication techniques are employed. In the present invention, substrates are prepared using a lamination process known as glass mat reinforced thermoplastics technology or, in an alternate embodiment, the substrate is made using a slurry process. 4 figs.

Dust Spectroscopy and the Nature of Grains

NASA Technical Reports Server (NTRS)

Tielens, A. G. G. M.

2006-01-01

Ground-based, air-borne and space-based, infrared spectra of a wide variety of objects have revealed prominent absorption and emission features due to large molecules and small dust grains. Analysis of this data reveals a highly diverse interstellar and circumstellar grain inventory, including both amorphous materials and highly crystalline compounds (silicates and carbon). This diversity points towards a wide range of physical and chemical birthsites as well as a complex processing of these grains in the interstellar medium. In this talk, I will review the dust inventory contrasting and comparing both the interstellar and circumstellar reservoirs. The focus will be on the processes that play a role in the lifecycle of dust in the interstellar medium.

Systems Analysis of Physical Absorption of CO2 in Ionic Liquids for Pre-Combustion Carbon Capture.

PubMed

Zhai, Haibo; Rubin, Edward S

2018-04-17

This study develops an integrated technical and economic modeling framework to investigate the feasibility of ionic liquids (ILs) for precombustion carbon capture. The IL 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide is modeled as a potential physical solvent for CO 2 capture at integrated gasification combined cycle (IGCC) power plants. The analysis reveals that the energy penalty of the IL-based capture system comes mainly from the process and product streams compression and solvent pumping, while the major capital cost components are the compressors and absorbers. On the basis of the plant-level analysis, the cost of CO 2 avoided by the IL-based capture and storage system is estimated to be $63 per tonne of CO 2 . Technical and economic comparisons between IL- and Selexol-based capture systems at the plant level show that an IL-based system could be a feasible option for CO 2 capture. Improving the CO 2 solubility of ILs can simplify the capture process configuration and lower the process energy and cost penalties to further enhance the viability of this technology.

Plasma flow reactor for steady state monitoring of physical and chemical processes at high temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koroglu, Batikan; Mehl, Marco; Armstrong, Michael R.

Here, we present the development of a steady state plasma flow reactor to investigate gas phase physical and chemical processes that occur at high temperature (1000 < T < 5000 K) and atmospheric pressure. The reactor consists of a glass tube that is attached to an inductively coupled argon plasma generator via an adaptor (ring flow injector). We have modeled the system using computational fluid dynamics simulations that are bounded by measured temperatures. In situ line-of-sight optical emission and absorption spectroscopy have been used to determine the structures and concentrations of molecules formed during rapid cooling of reactants after theymore » pass through the plasma. Emission spectroscopy also enables us to determine the temperatures at which these dynamic processes occur. A sample collection probe inserted from the open end of the reactor is used to collect condensed materials and analyze them ex situ using electron microscopy. The preliminary results of two separate investigations involving the condensation of metal oxides and chemical kinetics of high-temperature gas reactions are discussed.« less

Plasma flow reactor for steady state monitoring of physical and chemical processes at high temperatures

DOE PAGES

Koroglu, Batikan; Mehl, Marco; Armstrong, Michael R.; ...

2017-09-11

Here, we present the development of a steady state plasma flow reactor to investigate gas phase physical and chemical processes that occur at high temperature (1000 < T < 5000 K) and atmospheric pressure. The reactor consists of a glass tube that is attached to an inductively coupled argon plasma generator via an adaptor (ring flow injector). We have modeled the system using computational fluid dynamics simulations that are bounded by measured temperatures. In situ line-of-sight optical emission and absorption spectroscopy have been used to determine the structures and concentrations of molecules formed during rapid cooling of reactants after theymore » pass through the plasma. Emission spectroscopy also enables us to determine the temperatures at which these dynamic processes occur. A sample collection probe inserted from the open end of the reactor is used to collect condensed materials and analyze them ex situ using electron microscopy. The preliminary results of two separate investigations involving the condensation of metal oxides and chemical kinetics of high-temperature gas reactions are discussed.« less

Quantifying the loss of methane through secondary gas mass transport (or 'slip') from a micro-porous membrane contactor applied to biogas upgrading.

PubMed

McLeod, Andrew; Jefferson, Bruce; McAdam, Ewan J

2013-07-01

Secondary gas transport during the separation of a binary gas with a micro-porous hollow fibre membrane contactor (HMFC) has been studied for biogas upgrading. In this application, the loss or 'slip' of the secondary gas (methane) during separation is a known concern, specifically since methane possesses the intrinsic calorific value. Deionised (DI) water was initially used as the physical solvent. Under these conditions, carbon dioxide (CO2) and methane (CH4) absorption were dependent upon liquid velocity (V(L)). Whilst the highest CO2 flux was recorded at high V(L), selectivity towards CO2 declined due to low residence times and a diminished gas-side partial pressure, and resulted in slip of approximately 5.2% of the inlet methane. Sodium hydroxide was subsequently used as a comparative chemical absorption solvent. Under these conditions, CO2 mass transfer increased by increasing gas velocity (VG) which is attributed to the excess of reactive hydroxide ions present in the solvent, and the fast conversion of dissolved CO2 to carbonate species reinitiating the concentration gradient at the gas-liquid interface. At high gas velocities, CH4 slip was reduced to 0.1% under chemical conditions. Methane slip is therefore dependent upon whether the process is gas phase or liquid phase controlled, since methane mass transport can be adequately described by Henry's law within both physical and chemical solvents. The addition of an electrolyte was found to further retard CH4 absorption via the salting out effect. However, their applicability to physical solvents is limited since electrolytic concentration similarly impinges upon the solvents' capacity for CO2. This study illustrates the significance of secondary gas mass transport, and furthermore demonstrates that gas-phase controlled systems are recommended where greater selectivity is required. Copyright © 2013 Elsevier Ltd. All rights reserved.

The effect of moisture absorption on the physical properties of polyurethane shape memory polymer foams.

PubMed

Yu, Ya-Jen; Hearon, Keith; Wilson, Thomas S; Maitland, Duncan J

2011-08-01

The effect of moisture absorption on the glass transition temperature (T(g)) and stress/strain behavior of network polyurethane shape memory polymer (SMP) foams has been investigated. With our ultimate goal of engineering polyurethane SMP foams for use in blood contacting environments, we have investigated the effects of moisture exposure on the physical properties of polyurethane foams. To our best knowledge, this study is the first to investigate the effects of moisture absorption at varying humidity levels (non-immersion and immersion) on the physical properties of polyurethane SMP foams. The SMP foams were exposed to differing humidity levels for varying lengths of time, and they exhibited a maximum water uptake of 8.0% (by mass) after exposure to 100% relative humidity for 96 h. Differential scanning calorimetry results demonstrated that water absorption significantly decreased the T(g) of the foam, with a maximum water uptake shifting the T(g) from 67 °C to 5 °C. Samples that were immersed in water for 96 h and immediately subjected to tensile testing exhibited 100% increases in failure strains and 500% decreases in failure stresses; however, in all cases of time and humidity exposure, the plasticization effect was reversible upon placing moisture-saturated samples in 40% humidity environments for 24 h.

The effect of moisture absorption on the physical properties of polyurethane shape memory polymer foams

PubMed Central

Yu, Ya-Jen; Hearon, Keith; Wilson, Thomas S.; Maitland, Duncan J.

2011-01-01

The effect of moisture absorption on the glass transition temperature (Tg) and stress/strain behavior of network polyurethane shape memory polymer (SMP) foams has been investigated. With our ultimate goal of engineering polyurethane SMP foams for use in blood contacting environments, we have investigated the effects of moisture exposure on the physical properties of polyurethane foams. To our best knowledge, this study is the first to investigate the effects of moisture absorption at varying humidity levels (non-immersion and immersion) on the physical properties of polyurethane SMP foams. The SMP foams were exposed to differing humidity levels for varying lengths of time, and they exhibited a maximum water uptake of 8.0% (by mass) after exposure to 100% relative humidity for 96 h. Differential scanning calorimetry results demonstrated that water absorption significantly decreased the Tg of the foam, with a maximum water uptake shifting the Tg from 67 °C to 5 °C. Samples that were immersed in water for 96 h and immediately subjected to tensile testing exhibited 100% increases in failure strains and 500% decreases in failure stresses; however, in all cases of time and humidity exposure, the plasticization effect was reversible upon placing moisture-saturated samples in 40% humidity environments for 24 h. PMID:21949469

The effect of moisture absorption on the physical properties of polyurethane shape memory polymer foams

NASA Astrophysics Data System (ADS)

Yu, Ya-Jen; Hearon, Keith; Wilson, Thomas S.; Maitland, Duncan J.

2011-08-01

The effect of moisture absorption on the glass transition temperature (Tg) and the stress/strain behavior of network polyurethane shape memory polymer (SMP) foams has been investigated. With our ultimate goal of engineering polyurethane SMP foams for use in blood-contacting environments, we have investigated the effects of moisture exposure on the physical properties of polyurethane foams. To the best of our knowledge, this study is the first to investigate the effects of moisture absorption at varying humidity levels (non-immersion and immersion) on the physical properties of polyurethane SMP foams. The SMP foams were exposed to differing humidity levels for varying lengths of time, and they exhibited a maximum water uptake of 8.0% (by mass) after exposure to 100% relative humidity for 96 h. Differential scanning calorimetry results demonstrated that water absorption significantly decreased the Tg of the foam, with a maximum water uptake shifting the Tg from 67 to 5 °C. Samples that were immersed in water for 96 h and immediately subjected to tensile testing exhibited 100% increases in failure strains and 500% decreases in failure stresses; however, in all cases of time and humidity exposure, the plasticization effect was reversible upon placing moisture-saturated samples in 40% humidity environments for 24 h.

Effect of epoxidised soybean oil loading as plasticiser on physical, mechanical and thermal properties of polyvinylchloride

NASA Astrophysics Data System (ADS)

Rahmah, M.; Nurazzi, N. Mohd; Farah Nordyana, A. R.; Syed Anas, S. M.

2017-07-01

The aim of this paper is to study the effect of epoxidised soybean oil (ESO) as an alternative plasticizer on physical, mechanical and thermal properties of plasticised polyvinyl chloride (PPVC). Samples were prepared using 10, 20, 30 and 40% by weight percent of ESO. The samples were characterized for density, water absorption, tensile, hardness and thermal properties. The addition of ESO as plasticizer in PVC had caused significant effect on the physical and mechanical properties of PPVC. Increasing of ESO loading had resulted in decreased density, tensile strength, tensile modulus but increased in elongation at break and shore hardness. From water absorption study, it was observed that the all the samples reached the plateau absorption at days 8 to 10 with absorption percentages of between 1.8 to 2%. In general the crystallinity of PPVC maintained between 10 to 13% with increase in ESO loading while the melting point ( Tm) is slightly decreased about 3 to 6°C. In this study, ESO which acts as plasticiser were found to result in lower glass transition temperature (Tg). The enhancements of super cooling with higher ESO loading were found to increase the crystallization temperature, promoting crystallisation and act as nucleating agent.

Radiative interactions in transient energy transfer in gaseous systems

NASA Technical Reports Server (NTRS)

Tiwari, S. N.

1985-01-01

Analyses and numerical procedures are presented to investigate the radiative interactions in transient energy transfer processes in gaseous systems. The nongray radiative formulations are based on the wide-band model correlations for molecular absorption. Various relations for the radiative flux are developed; these are useful for different flow conditions and physical problems. Specific plans for obtaining extensive results for different cases are presented. The methods presented in this study can be extended easily to investigate the radiative interactions in realistic flows of hydrogen-air species in the scramjet engine.

Near infrared spectrum simulation applied to human skin for diagnosis

NASA Astrophysics Data System (ADS)

Tsai, Chen-Mu; Fang, Yi-Chin; Wang, Chih-Yu; Chiu, Pin-Chun; Wu, Guo-Ying; Zheng, Wei-Chi; Chemg, Shih-Hao

2007-11-01

This research proposes a new method for skin diagnose using near infrared as the light source (750nm~1300nm). Compared to UV and visible light, near infrared might penetrate relatively deep into biological soft tissue in some cases although NIR absorption property of tissue is not a constant for water, fat, and collagen etc. In the research, NIR absorption and scattering properties for skin are discussed firstly using the theory of molecule vibration from Quantum physics and Solid State Physics; secondly the practical model for various NIR absorption spectrum to skin tissue are done by optical simulation for human skin. Finally, experiments are done for further identification of proposed model for human skin and its reaction to near infrared. Results show success with identification from both theory and experiments.

Sound propagation and absorption in foam - A distributed parameter model.

NASA Technical Reports Server (NTRS)

Manson, L.; Lieberman, S.

1971-01-01

Liquid-base foams are highly effective sound absorbers. A better understanding of the mechanisms of sound absorption in foams was sought by exploration of a mathematical model of bubble pulsation and coupling and the development of a distributed-parameter mechanical analog. A solution by electric-circuit analogy was thus obtained and transmission-line theory was used to relate the physical properties of the foams to the characteristic impedance and propagation constants of the analog transmission line. Comparison of measured physical properties of the foam with values obtained from measured acoustic impedance and propagation constants and the transmission-line theory showed good agreement. We may therefore conclude that the sound propagation and absorption mechanisms in foam are accurately described by the resonant response of individual bubbles coupled to neighboring bubbles.

A multi-epoch spectroscopic study of the BAL quasar APM 08279+5255. II. Emission- and absorption-line variability time lags

NASA Astrophysics Data System (ADS)

Saturni, F. G.; Trevese, D.; Vagnetti, F.; Perna, M.; Dadina, M.

2016-03-01

Context. The study of high-redshift bright quasars is crucial to gather information about the history of galaxy assembly and evolution. Variability analyses can provide useful data on the physics of quasar processes and their relation with the host galaxy. Aims: In this study, we aim to measure the black hole mass of the bright lensed BAL QSO APM 08279+5255 at z = 3.911 through reverberation mapping, and to update and extend the monitoring of its C IV absorption line variability. Methods: We perform the first reverberation mapping of the Si IV and C IV emission lines for a high-luminosity quasar at high redshift with the use of 138 R-band photometric data and 30 spectra available over 16 years of observations. We also cross-correlate the C IV absorption equivalent width variations with the continuum light curve to estimate the recombination time lags of the various absorbers and infer the physical conditions of the ionised gas. Results: We find a reverberation-mapping time lag of ~900 rest-frame days for both Si IV and C IV emission lines. This is consistent with an extension of the BLR size-to-luminosity relation for active galactic nuclei up to a luminosity of ~1048 erg s-1, and implies a black hole mass of 1010 M⊙. Additionally, we measure a recombination time lag of ~160 days in the rest frame for the C IV narrow absorption system, which implies an electron density of the absorbing gas of ~2.5 × 104 cm-3. Conclusions: The measured black hole mass of APM 08279+5255 indicates that the quasar resides in an under-massive host-galaxy bulge with Mbulge ~ 7.5MBH, and that the lens magnification is lower than ~8. Finally, the inferred electron density of the narrow-line absorber implies a distance of the order of 10 kpc of the absorbing gas from the quasar, placing it within the host galaxy.

Materials Science and Device Physics of 2-Dimensional Semiconductors

NASA Astrophysics Data System (ADS)

Fang, Hui

Materials and device innovations are the keys to future technology revolution. For MOSFET scaling in particular, semiconductors with ultra-thin thickness on insulator platform is currently of great interest, due to the potential of integrating excellent channel materials with the industrially mature Si processing. Meanwhile, ultra-thin thickness also induces strong quantum confinement which in turn affect most of the material properties of these 2-dimensional (2-D) semiconductors, providing unprecedented opportunities for emerging technologies. In this thesis, multiple novel 2-D material systems are explored. Chapter one introduces the present challenges faced by MOSFET scaling. Chapter two covers the integration of ultrathin III V membranes with Si. Free standing ultrathin III-V is studied to enable high performance III-V on Si MOSFETs with strain engineering and alloying. Chapter three studies the light absorption in 2-D membranes. Experimental results and theoretical analysis reveal that light absorption in the 2-D quantum membranes is quantized into a fundamental physical constant, where we call it the quantum unit of light absorption, irrelevant of most of the material dependent parameters. Chapter four starts to focus on another 2-D system, atomic thin layered chalcogenides. Single and few layered chalcogenides are first explored as channel materials, with focuses in engineering the contacts for high performance MOSFETs. Contact treatment by molecular doping methods reveals that many layered chalcogenides other than MoS2 exhibit good transport properties at single layer limit. Finally, Chapter five investigated 2-D van der Waals heterostructures built from different single layer chalcogenides. The investigation in a WSe2/MoS2 hetero-bilayer shows a large Stokes like shift between photoluminescence peak and lowest absorption peak, as well as strong photoluminescence intensity, consistent with spatially indirect transition in a type II band alignment in this van der Waals heterostructure. This result enables new family of semiconductor heterostructures having tunable optoelectronic properties with customized composite layers and highlights the ability to build van der Waals semiconductor heterostructure lasers/LEDs.

Determination of the water vapor continuum absorption by THz-TDS and Molecular Response Theory.

PubMed

Yang, Yihong; Mandehgar, Mahboubeh; Grischkowsky, D

2014-02-24

Determination of the water vapor continuum absorption from 0.35 to 1 THz is reported. The THz pulses propagate though a 137 m long humidity-controlled chamber and are measured by THz time-domain spectroscopy (THz-TDS). The average relative humidity along the entire THz path is precisely obtained by measuring the difference between transit times of the sample and reference THz pulses to an accuracy of 0.1 ps. Using the measured total absorption and the calculated resonance line absorption with the Molecular Response Theory lineshape, based on physical principles and measurements, an accurate continuum absorption is obtained within four THz absorption windows, that agrees well with the empirical theory. The absorption is significantly smaller than that obtained using the van Vleck-Weisskopf lineshape with a 750 GHz cut-off.

Studies of solid carbon dioxide in interstellar ice analogs subject to thermal processing

NASA Astrophysics Data System (ADS)

White, Douglas W.

2010-09-01

Solid CO2 has been detected in many lines of sight in the interstellar medium from infrared observatories. Spectral profiles from space-based observatories have suggested that CO2 on icy grain mantles is mixed with other common molecules such as H2O and CH 3OH in interstellar regions and that thermal annealing has occurred. The vibrational mode at 658 cm-1 (15.2 mum) is suspected to be a powerful diagnostic tool as to the composition of species on icy grain mantles as well as thermal histories. However, previous studies have not systematically investigated ice composition and temperature. Laboratory spectra of interstellar ice analogs have been created in this study order to better understand the physical properties of solid CO2 in these interstellar environments. Existing databases of ice composition studies and effects of ice thermal history were updated in this study to include a more systematic approach. The 658 cm-1 (15.2 mum) bending mode feature of CO2 is examined here and the subsequent astrophysical implications stated. In the first set of experiments, 47 mixtures of H2O,CH3OH, andCO2 were slowly warmed and mid-infrared absorption spectra were recorded at 5K intervals. The second set of experiments involved examining the CO2 bending mode feature of 10 different CO2-containing ice mixtures at different temperatures where ice segregation was suspected. In these experiments, the ice mixtures were slowly heated to the desired temperature for increasing time intervals before cooling down and recording mid-IR absorption spectra. These studies may be used to analyze IR data from space-based observatories such as the Spitzer Space Telescope Infrared Spectrograph as well other future IR observations of the interstellar medium. Finally, mass spectroscopy measurements were taken from temperature programmed desorption (TPD) experiments performed on several binary mixtures of H2O + CO2 and CH 3OH + CO2. Physical properties such as desorption energy of CO2 can be determined from the TPD traces of these experiments. The work provided here addresses the physical properties of solid CO 2 thermally processed in ice mixtures in interstellar environments by laboratory simulations spectroscopically analyzed by mid-infrared absorption profiles and TPD.

Simplification of the laser absorption process in the particle simulation for the laser-induced shockwave processing

NASA Astrophysics Data System (ADS)

Shimamura, Kohei

2016-09-01

To reduce the computational cost in the particle method for the numerical simulation of the laser plasma, we examined the simplification of the laser absorption process. Because the laser frequency is sufficiently larger than the collision frequency between the electron and heavy particles, we assumed that the electron obtained the constant value from the laser irradiation. First of all, the simplification of the laser absorption process was verified by the comparison of the EEDF and the laser-absorptivity with PIC-FDTD method. Secondary, the laser plasma induced by TEA CO2 laser in Argon atmosphere was modeled using the 1D3V DSMC method with the simplification of the laser-absorption. As a result, the LSDW was observed with the typical electron and neutral density distribution.

Absorption spectrum of the firefly luciferin anion isolated in vacuo.

PubMed

Støchkel, Kristian; Milne, Bruce F; Brøndsted Nielsen, Steen

2011-03-24

The excited-state physics of the firefly luciferin anion depends on its chemical environment, and it is therefore important to establish the intrinsic behavior of the bare ion. Here we report electronic absorption spectra of the anion isolated in vacuo obtained at an electrostatic ion storage ring and an accelerator mass spectrometer where ionic dissociation is monitored on a long time scale (from 33 μs and up to 3 ms) and on a short time scale (0-3 μs), respectively. In the ring experiment the yield of all neutrals (mainly CO(2)) as a function of wavelength was measured whereas in the single pass experiment, the abundance of daughter ions formed after loss of CO(2) was recorded to provide action spectra. We find maxima at 535 and 265 nm, and that the band shape is largely determined by the sampling time interval, which is due to the kinetics of the dissociation process. Calculations at the TD-B3LYP/TZVPP++ level predict maximum absorption at 533 and 275 nm for the carboxylate isomer in excellent agreement with the experimental findings. The phenolate isomer lies higher in energy by 0.22 eV, and also its absorption maximum is calculated to be at 463 nm, which is far away from the experimental value. Our data serve to benchmark future theoretical models for bioluminescence from fireflies.

Connecting the Interstellar Gas and Dust Properties in Distant Galaxies Using Quasar Absorption Systems

NASA Technical Reports Server (NTRS)

Aller, Monique C.; Dwek, Eliahu; Kulkarni, Varsha P.; York, Donald G.; Welty, Daniel E.; Vladilo, Giovanni; Som, Debopam; Lackey, Kyle; Dwek, Eli; Beiranvand, Nassim;

Pump-probe spectroscopy and imaging of heme proteins: temperature effects and data analysis

NASA Astrophysics Data System (ADS)

Wang, Erkang; Domingue, Scott R.; Bartels, Randy A.; Wilson, Jesse W.

2017-08-01

Ultrafast pump-probe microscopy enables visualization of non-fluorescent materials in biological tissue, such as melanin and hemoglobin. Whereas transient absorption has been primarily a physical chemistry technique, used to gain insight into molecular and electronic structure, pump-probe microscopy represents a paradigm shift in translating transient absorption into an analytical technique, which can clearly resolve pigments with nearly indistinguishable linear absorption spectra. Extending this technique to other important targets, such as mitochondrial respiratory chain hemes, will require new laser sources and new data processing techniques to estimate heme content from the pump-probe response. We will present recent developments on both of these fronts. The laser system we have developed to elicit a pump probe response of respiratory chain hemes is based on an amplified Yb:fiber ultrafast laser that uses modest spectral broadening followed by sum frequency generation to produce a tunable pulse pair in the visible region. Wavelength tuning is accomplished by changing quasi-phase matching conditions. We will present preliminary imaging data in addition to discussing management of sample heating problems that arise from performing transient absorption measurements at the high repetition rates needed for imaging microscopy. In the second part of the talk, we will present the use of regularized and non-negative least squares fitting, along with feature-preserving noise removal to estimate composition of a pixel from its pump-probe response.

Improved Modeling of Midlatitude D-Region Ionospheric Absorption of High Frequency Radio Signals During Solar X-Ray Flares

DTIC Science & Technology

2009-06-01

a physics-based model which calculates mid - latitude ionospheric electron and ion density profiles for prediction of HF propagation and absorption...greatest in the summer due to longer periods of daylight and ionization. For times not close to sunrise or sunset, mid - latitude ionospheric ...IMPROVED MODELING OF MIDLATITUDE D-REGION IONOSPHERIC ABSORPTION OF HIGH FREQUENCY RADIO SIGNALS DURING SOLAR X-RAY FLARES 1

Survey for C-Band High Spectral Lines with the Arecibo Telescope

NASA Astrophysics Data System (ADS)

Tan, Wei Siang

High-mass stars have masses greater than 8 solar masses and are the main source of heavy elements such as iron in the interstellar medium. This type of stars form in giant molecular clouds. Studying the molecular environment in star-forming regions is crucial to understand the physical structure and conditions that lead to the formation of high-mass stars. This thesis presents observations conducted with the 305m Arecibo Telescope in Puerto Rico of twelve high-mass star forming regions. Every source was observed in multiple transitions of molecular species including CH, CH3OH, H2CS, and OH lines, and a radio recombination line. The observations were conducted with the C-Band High receiver of the Arecibo Telescope in the frequency range of 6.0 to 7.4GHz. The goals of the observations were to investigate the detectability of different molecular species (including new possible molecular masers) and obtain high sensitivity observations of the 6.7GHz CH3OH line to detect absorption and use it as a probe of the kinematics of the molecular material with respect to the ionized gas. Among the results of the observations, we report detection of 6.7GHz CH3OH masers toward nine regions, OH masers toward five sources, 6.7GHz CH3OH absorption toward four sources (including tentative detections), and detection of H2CS toward the star forming region G34.26+0.15. We also found a variable and recurrent 6.7GHz CH3OH maser in G45.12+0.13. The 6.7GHz CH 3OH and 6278.65MHz H2CS absorption lines were modeled using the radiative transfer code RADEX to investigate the physical conditions of the molecular clouds responsible for the absorption lines. Our analysis of the absorption lines supports the interpretation that the spectral lines are tracing molecular envelopes of HII regions. In the case of 6.7GHz CH 3OH absorption, our results and data from an extensive literature review indicate that absorption is rare, but that a population of 6.7GHz CH 3OH absorbers may be present at levels below ˜ 100mJy. In the case of the 6278.65MHz H2CS absorption in G34.26+0.15, the data are consistent with infalling gas onto the HII region, which supports the key principle of gravitational collapse of molecular clouds during the process of star formation. However, high angular resolution observations of the H 2CS line are needed to confirm the infall hypothesis.

Functional Coupling of Human Microphysiology Systems: Intestine, Liver, Kidney Proximal Tubule, Blood-Brain Barrier and Skeletal Muscle

PubMed Central

Vernetti, Lawrence; Gough, Albert; Baetz, Nicholas; Blutt, Sarah; Broughman, James R.; Brown, Jacquelyn A.; Foulke-Abel, Jennifer; Hasan, Nesrin; In, Julie; Kelly, Edward; Kovbasnjuk, Olga; Repper, Jonathan; Senutovitch, Nina; Stabb, Janet; Yeung, Catherine; Zachos, Nick C.; Donowitz, Mark; Estes, Mary; Himmelfarb, Jonathan; Truskey, George; Wikswo, John P.; Taylor, D. Lansing

2017-01-01

Organ interactions resulting from drug, metabolite or xenobiotic transport between organs are key components of human metabolism that impact therapeutic action and toxic side effects. Preclinical animal testing often fails to predict adverse outcomes arising from sequential, multi-organ metabolism of drugs and xenobiotics. Human microphysiological systems (MPS) can model these interactions and are predicted to dramatically improve the efficiency of the drug development process. In this study, five human MPS models were evaluated for functional coupling, defined as the determination of organ interactions via an in vivo-like sequential, organ-to-organ transfer of media. MPS models representing the major absorption, metabolism and clearance organs (the jejunum, liver and kidney) were evaluated, along with skeletal muscle and neurovascular models. Three compounds were evaluated for organ-specific processing: terfenadine for pharmacokinetics (PK) and toxicity; trimethylamine (TMA) as a potentially toxic microbiome metabolite; and vitamin D3. We show that the organ-specific processing of these compounds was consistent with clinical data, and discovered that trimethylamine-N-oxide (TMAO) crosses the blood-brain barrier. These studies demonstrate the potential of human MPS for multi-organ toxicity and absorption, distribution, metabolism and excretion (ADME), provide guidance for physically coupling MPS, and offer an approach to coupling MPS with distinct media and perfusion requirements. PMID:28176881

Absorption fluids data survey

NASA Astrophysics Data System (ADS)

Macriss, R. A.; Zawacki, T. S.

Development of improved data for the thermodynamic, transport and physical properties of absorption fluids were studied. A specific objective of this phase of the study is to compile, catalog and coarse screen the available US data of known absorption fluid systems and publish it as a first edition document to be distributed to manufacturers, researchers and others active in absorption heat pump activities. The methodology and findings of the compilation, cataloguing and coarse screening of the available US data on absorption fluid properties and presents current status and future work on this project are summarized. Both in house file and literature searches were undertaken to obtain available US publications with pertinent physical, thermodynamic and transport properties data for absorption fluids. Cross checks of literature searches were also made, using available published bibliographies and literature review articles, to eliminate secondary sources for the data and include only original sources and manuscripts. The properties of these fluids relate to the liquid and/or vapor state, as encountered in normal operation of absorption equipment employing such fluids, and to the crystallization boundary of the liquid phase, where applicable. The actual data were systematically classified according to the type of fluid and property, as well as temperature, pressure and concentration ranges over which data were available. Data were sought for 14 different properties: Vapor-Liquid Equilibria, Crystallization Temperature, Corrosion Characteristics, Heat of Mixing, Liquid-Phase-Densities, Vapor-Liquid-Phase Enthalpies, Specific Heat, Stability, Viscosity, Mass Transfer Rate, Heat Transfer Rate, Thermal Conductivity, Flammability, and Toxicity.

Experimental investigation and model verification for a GAX absorber

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palmer, S.C.; Christensen, R.N.

1996-12-31

In the ammonia-water generator-absorber heat exchange (GAX) absorption heat pump, the heat and mass transfer processes which occur between the generator and absorber are the most crucial in assuring that the heat pump will achieve COPs competitive with those of current technologies. In this study, a model is developed for the heat and mass transfer processes that occur in a counter-current vertical fluted tube absorber (VFTA) with inserts. Correlations for heat and mass transfer in annuli are used to model the processes in the VTA. Experimental data is used to validate the model for three different insert geometries. Comparison ofmore » model results with experimental data provides insight into model corrections necessary to bring the model into agreement with the physical phenomena observed in the laboratory.« less

Modelling ultrafast laser ablation

NASA Astrophysics Data System (ADS)

Rethfeld, Baerbel; Ivanov, Dmitriy S.; E Garcia, Martin; Anisimov, Sergei I.

2017-05-01

This review is devoted to the study of ultrafast laser ablation of solids and liquids. The ablation of condensed matter under exposure to subpicosecond laser pulses has a number of peculiar properties which distinguish this process from ablation induced by nanosecond and longer laser pulses. The process of ultrafast ablation includes light absorption by electrons in the skin layer, energy transfer from the skin layer to target interior by nonlinear electronic heat conduction, relaxation of the electron and ion temperatures, ultrafast melting, hydrodynamic expansion of heated matter accompanied by the formation of metastable states and subsequent formation of breaks in condensed matter. In case of ultrashort laser excitation, these processes are temporally separated and can thus be studied separately. As for energy absorption, we consider peculiarities of the case of metal irradiation in contrast to dielectrics and semiconductors. We discuss the energy dissipation processes of electronic thermal wave and lattice heating. Different types of phase transitions after ultrashort laser pulse irradiation as melting, vaporization or transitions to warm dense matter are discussed. Also nonthermal phase transitions, directly caused by the electronic excitation before considerable lattice heating, are considered. The final material removal occurs from the physical point of view as expansion of heated matter; here we discuss approaches of hydrodynamics, as well as molecular dynamic simulations directly following the atomic movements. Hybrid approaches tracing the dynamics of excited electrons, energy dissipation and structural dynamics in a combined simulation are reviewed as well.

The impact of radiation belts region on top side ionosphere condition during last solar minimum.

NASA Astrophysics Data System (ADS)

Rothkaehl, Hanna; Przepiórka, Dororta; Matyjasiak, Barbara

2014-05-01

The wave particle interactions in radiation belts region are one of the key parameters in understanding the global physical processes which govern the near Earth environment. The populations of outer radiation belts electrons increasing in response to changes in the solar wind and the interplanetary magnetic field, and decreasing as a result of scattering into the loss cone and subsequent absorption by the atmosphere. The most important question in relation to understanding the physical processes in radiation belts region relates to estimate the ratio between acceleration and loss processes. This can be also very useful for construct adequate models adopted in Space Weather program. Moreover the wave particle interaction in inner radiation zone and in outer radiation zone have significant influence on the space plasma property at ionospheric altitude. The aim of this presentation is to show the manifestation of radiation belts region at the top side ionosphere during the last long solar minimum. The presentation of longitude and seasonal changes of plasma parameters affected by process occurred in radiation belts region has been performed on the base of the DEMETER and COSMIC 3 satellite registration. This research is partly supported by grant O N517 418440

Physical and chemical properties of pyropheophorbide-a methyl ester in ethanol, phosphate buffer and aqueous dispersion of small unilamellar dimyristoyl-L-alpha-phosphatidylcholine vesicles.

PubMed

Delanaye, Lisiane; Bahri, Mohamed Ali; Tfibel, Francis; Fontaine-Aupart, Marie-Pierre; Mouithys-Mickalad, Ange; Heine, Bélinda; Piette, Jacques; Hoebeke, Maryse

2006-03-01

The aggregation process of pyropheophorbide-a methyl ester (PPME), a second-generation photosensitizer, was investigated in various solvents. Absorption and fluorescence spectra showed that the photosensitizer was under a monomeric form in ethanol as well as in dimyristoyl-L-alpha-phosphatidylcholine liposomes while it was strongly aggregated in phosphate buffer. A quantitative determination of reactive oxygen species production by PPME in these solvents has been undertaken by electron spin resonance associated with spin trapping technique and absorption spectroscopy. In phosphate buffer, both electron spin resonance and absorption measurements led to the conclusion that singlet oxygen production was not detectable while hydroxyl radical production was very weak. In liposomes and ethanol, singlet oxygen and hydroxyl radical production increased highly; the singlet oxygen quantum yield was determined to be 0.2 in ethanol and 0.13 in liposomes. The hydroxyl radical production origin was also investigated. Singlet oxygen was formed from PPME triplet state deactivation in the presence of oxygen. Indeed, the triplet state formation quantum yield of PPME was found to be about 0.23 in ethanol, 0.15 in liposomes (too small to be measured in PBS).

Influence of nano-fibrillated cellulose (NFC) on starch digestion and glucose absorption.

PubMed

Liu, Lingling; Kerr, William L; Kong, Fanbin; Dee, Derek R; Lin, Mengshi

2018-09-15

Nano-fibrillated cellulose (NFC) is of interest in several fields due to its unique physical properties derived from its nanoscale dimensions. NFC has potential use in food systems as a dietary fiber that increases viscosity and limit diffusion of glucose. This study focused on the effects of added NFC on solution viscosity, starch digestion and glucose absorption. NFC did not affect α-amylase and α-glucosidase activity, but significantly retarded glucose diffusion, delayed amylolysis and reduced the amount of glucose released during in vitro digestion of starch. Specifically, 1% NFC retarded ∼26.6% of glucose released during the amylolysis process. The greatly increased viscosity of NFC at concentrations >0.5% was thought to be the main mechanism for its potential hypoglycemic effects. NFC suspensions also had higher glucose adsorption capacity than those containing cellulose. In addition, NFC bound 35.6% of the glucose when the initial glucose level was within the range of 5-200 mM. These results suggest that NFC may be useful for building viscosity in food products and serving to inhibit glucose absorption in vivo in starch-containing products. Copyright © 2018 Elsevier Ltd. All rights reserved.

Electromagnetic-wave propagation in unmagnetized plasmas

NASA Astrophysics Data System (ADS)

Gregoire, D. J.; Santoru, J.; Schumacher, R. W.

1992-03-01

This final report describes an investigation of electromagnetic-wave propagation in unmagnetized plasmas and its application to the reduction of the radar cross section (RCS) of a plasma-filled enclosure. We have demonstrated RCS reduction of 20 to 25 dB with a prototype system at the radar range at Hughes Aircraft's Microwave Products Division in Torrance. The prototype consists of a sealed ceramic enclosure with a microwave reflector and a plasma generator inside it. When the plasma is present, the RCS is significantly reduced over a frequency range of 4 to 14 GHz. As part of the program, we also investigated the basic-plasma-physics issues relating to the absorption and refraction of electromagnetic (EM) waves in collisional plasmas. We demonstrated absorption as high as 63 dB in a section of plasma-loaded C-band rectangular waveguide. We also developed a theoretical model for the plasma cloaking process that includes scattering contributions from the plasma-vacuum interface, partial reflections from the plasma, and collisional absorption in the plasma. The theoretical model is found to be in reasonable agreement with the experimental results and can be used to confidently design future plasma cloaking systems.

Conversion of laser energy to gas kinetic energy

NASA Technical Reports Server (NTRS)

Caledonia, G. E.

1975-01-01

Techniques for the gas phase absorption of laser radiation for conversion to gas kinetic energy are discussed. Absorption by inverse Bremsstrahlung, in which laser energy is converted at a gas kinetic rate in a spectrally continuous process, is briefly described, and absorption by molecular vibrational rotation bands is discussed at length. High pressure absorption is proposed as a means of minimizing gas bleaching and dissociation, the major disadvantages of the molecular absorption process. A band model is presented for predicting the molecular absorption spectra in the high pressure absorption region and is applied to the CO molecule. Use of a rare gas seeded with Fe(CO)5 for converting vibrational modes to translation modes is described.

Numerical analysis of quantitative measurement of hydroxyl radical concentration using laser-induced fluorescence in flame

NASA Astrophysics Data System (ADS)

Shuang, Chen; Tie, Su; Yao-Bang, Zheng; Li, Chen; Ting-Xu, Liu; Ren-Bing, Li; Fu-Rong, Yang

2016-06-01

The aim of the present work is to quantitatively measure the hydroxyl radical concentration by using LIF (laser-induced fluorescence) in flame. The detailed physical models of spectral absorption lineshape broadening, collisional transition and quenching at elevated pressure are built. The fine energy level structure of the OH molecule is illustrated to understand the process with laser-induced fluorescence emission and others in the case without radiation, which include collisional quenching, rotational energy transfer (RET), and vibrational energy transfer (VET). Based on these, some numerical results are achieved by simulations in order to evaluate the fluorescence yield at elevated pressure. These results are useful for understanding the real physical processes in OH-LIF technique and finding a way to calibrate the signal for quantitative measurement of OH concentration in a practical combustor. Project supported by the National Natural Science Foundation of China (Grant No. 11272338) and the Fund from the Science and Technology on Scramjet Key Laboratory, China (Grant No. STSKFKT2013004).

Hydrodynamics of wet foams

NASA Astrophysics Data System (ADS)

Langevin, Dominique; Saint-Jalmes, Arnaud; Marze, Sébastien; Cox, Simon; Hutzler, Stefan; Drenckhan, Wiebke; Weaire, Denis; Caps, Hervé; Vandewalle, Nicolas; Adler, Micheàle; Pitois, Olivier; Rouyer, Florence; Cohen-Addad, Sylvie; Höhler, Reinhard; Ritacco, Hernan

2005-10-01

Foams and foaming pose important questions and problems to the chemical industry. As a material, foam is unusual in being a desired product while also being an unwanted byproduct within industry. Liquid foams are an essential part of gas/liquid contacting processes such as distillation and absorption, but over-production of foam in these processes can lead to downtime and loss of efficiency. Solid polymeric foams, such as polystyrene and polyurethane, find applications as insulation panels in the construction industry. Their combination of low weight and unique elastic/plastic properties make them ideal as packing and cushioning materials. Foams made with proteins are extensively used in the food industry. Despite the fact that foam science is a rapidly maturing field, critical aspects of foam physics and chemistry remain unclear. Several gaps in knowledge were identified to be tackled as the core of this MAP project. In addition, microgravity affords conditions for extending our understanding far beyond the possibilities offered by ground-based investigation. This MAP project addresses the challenges posed by the physics of foams under microgravity.

Theoretical study on the sound absorption of electrolytic solutions. II. Assignments of relaxations.

PubMed

Yamaguchi, T; Matsuoka, T; Koda, S

2007-08-14

The theory on the ultrasonic absorption spectrum of electrolytic solutions recently proposed by us is applied to the model system that resembles to the aqueous solution of MgSO4. The charges on ions are reduced to +/-1.5e in order to obtain the equilibrium structure by the integral equation theory. The theory reproduces the existence of two relaxations around 100 kHz and 1 GHz. The physical origin of the relaxation is analyzed based on the theoretical expression. The slower relaxation is shown to originate in the formation of contact ion pair, in harmony with the conventional assignment. The amplitude of this relaxation agrees with the experimental one fairly well. The absorption cross section is a weakly increasing function of the concentration of the salt in theory, whereas it depends little on the concentration in experiment, which is ascribed to the weaker association of the pair in the theory. The deviation from the Debye relaxation is found for the faster process, and the concentration dependence is small. The analysis shows that this relaxation stems from the coupling between the pressure and the long-range concentration fluctuation, and the concentration independence and the non-Debye relaxation are explained based on the theoretical analysis. In particular, the theory demonstrates that this process has the t(-3/2) tail in the time domain, which is confirmed by numerical calculation. The deviation of the theoretical relaxation amplitude from the experimental one is elucidated in terms of the theoretical expression of the coefficient.

Observing quantum control of up-conversion luminescence in Dy3+ ion doped glass from weak to intermediate shaped femtosecond laser fields

NASA Astrophysics Data System (ADS)

Liu, Pei; Cheng, Wenjing; Yao, Yunhua; Xu, Cheng; Zheng, Ye; Deng, Lianzhong; Jia, Tianqing; Qiu, Jianrong; Sun, Zhenrong; Zhang, Shian

2017-11-01

Controlling the up-conversion luminescence of rare-earth ions in real-time, in a dynamical and reversible manner, is very important for their application in laser sources, fiber-optic communications, light-emitting diodes, color displays and biological systems. In previous studies, the up-conversion luminescence control mainly focused on the weak femtosecond laser field. Here, we further extend this control behavior from weak to intermediate femtosecond laser fields. In this work, we experimentally and theoretically demonstrate that the up-conversion luminescence in Dy3+ ion doped glass can be artificially controlled by a π phase step modulation, but the up-conversion luminescence control behavior will be affected by the femtosecond laser intensity, and the up-conversion luminescence is suppressed by lower laser intensity while enhanced by higher laser intensity. We establish a new theoretical model (i.e. the fourth-order perturbation theory) to explain the physical control mechanism by considering the two- and four-photon absorption processes, and the theoretical results show that the relative weight of four-photon absorption in the whole excitation process will increase with the increase in laser intensity, and the interference between two- and four-photon absorptions results in up-conversion luminescence control modulation under different laser intensities. These theoretical and experimental works can provide a new method to control and understand up-conversion luminescence in rare-earth ions, and also may open a new opportunity to the related application areas of rare-earth ions.

Physical mechanisms of timing jitter in photon detection by current-carrying superconducting nanowires

NASA Astrophysics Data System (ADS)

Sidorova, Mariia; Semenov, Alexej; Hübers, Heinz-Wilhelm; Charaev, Ilya; Kuzmin, Artem; Doerner, Steffen; Siegel, Michael

2017-11-01

We studied timing jitter in the appearance of photon counts in meandering nanowires with different fractional amount of bends. Intrinsic timing jitter, which is the probability density function of the random time delay between photon absorption in current-carrying superconducting nanowire and appearance of the normal domain, reveals two different underlying physical mechanisms. In the deterministic regime, which is realized at large photon energies and large currents, jitter is controlled by position-dependent detection threshold in straight parts of meanders. It decreases with the increase in the current. At small photon energies, jitter increases and its current dependence disappears. In this probabilistic regime jitter is controlled by Poisson process in that magnetic vortices jump randomly across the wire in areas adjacent to the bends.

Polymer alloys with balanced heat storage capacity and engineering attributes and applications thereof

DOEpatents

Soroushian, Parviz

2002-01-01

A thermoplastic polymer of relatively low melt temperature is blended with at least one of thermosets, elastomers, and thermoplastics of relatively high melt temperature in order to produce a polymer blend which absorbs relatively high quantities of latent heat without melting or major loss of physical and mechanical characteristics as temperature is raised above the melting temperature of the low-melt-temperature thermoplastic. The polymer blend can be modified by the addition of at least one of fillers, fibers, fire retardants, compatibilisers, colorants, and processing aids. The polymer blend may be used in applications where advantage can be taken of the absorption of excess heat by a component which remains solid and retains major fractions of its physical and mechanical characteristics while absorbing relatively high quantities of latent heat.

Optical spectroscopies diagnose cancer

NASA Astrophysics Data System (ADS)

Alfano, Robert R.; Das, Bidyut B.; Glassman, Wenling S.; Pradhan, Asima; Tang, Gui C.

1992-02-01

Today's medical professional is looking beyond the conventional procedures of X-rays, nuclear radiation, magnetic resonance, chemical analysis, and ultrasound to diagnose diseases ranging from cancer to heart ailments. In view of the possible dangerous side effects of X-rays and nuclear radiation, a need exists for novel techniques in disease detection that can either eliminate or reduce their use in examinations. For more than half a century, fluorescence, absorption, and light scattering spectroscopies have been widely used as probes to acquire fundamental knowledge about various physical, chemical, and biological processes. Light may offer alternatives to X-rays and nuclear approaches, and in some cases is non-invasive. Optical spectroscopy and laser technology may offer techniques for the detection and characterization of physical and chemical changes that occur in diseased tissue on a microscopic level.

Physical processes contributing to an ice free Beaufort Sea during September 2012

NASA Astrophysics Data System (ADS)

Babb, D. G.; Galley, R. J.; Barber, D. G.; Rysgaard, S.

2016-01-01

During the record September 2012 sea ice minimum, the Beaufort Sea became ice free for the first time during the observational record. Increased dynamic activity during late winter enabled increased open water and seasonal ice coverage that contributed to negative sea ice anomalies and positive solar absorption anomalies which drove rapid bottom melt and sea ice loss. As had happened in the Beaufort Sea during previous years of exceptionally low September sea ice extent, anomalous solar absorption developed during May, increased during June, peaked during July, and persisted into October. However in situ observations from a single floe reveal less than 78% of the energy required for bottom melt during 2012 was available from solar absorption. We show that the 2012 sea ice minimum in the Beaufort was the result of anomalously large solar absorption that was compounded by an arctic cyclone and other sources of heat such as solar transmission, oceanic upwelling, and riverine inputs, but was ultimately made possible through years of preconditioning toward a younger, thinner ice pack. Significant negative trends in sea ice concentration between 1979 and 2012 from June to October, coupled with a tendency toward earlier sea ice reductions have fostered a significant trend of +12.9 MJ m-2 yr-1 in cumulative solar absorption, sufficient to melt an additional 4.3 cm m-2 yr-1. Overall through preconditioning toward a younger, thinner ice pack the Beaufort Sea has become increasingly susceptible to increased sea ice loss that may render it ice free more frequently in coming years.

Physical Processes contributing to an ice free Beaufort Sea during September 2012

NASA Astrophysics Data System (ADS)

Babb, D.; Galley, R.; Barber, D. G.; Rysgaard, S.

2016-12-01

During the record September 2012 sea ice minimum the Beaufort Sea became ice free for the first time during the observational record. Increased dynamic activity during late winter enabled increased open water and seasonal ice coverage that contributed to negative sea ice anomalies and positive solar absorption anomalies which drove rapid bottom melt and sea ice loss. As had happened in the Beaufort Sea during previous years of exceptionally low September sea ice extent, anomalous solar absorption developed during May, increased during June, peaked during July and persisted into October. However in situ observations from a single floe reveal less than 78% of the energy required for bottom melt during 2012 was available from solar absorption. We show that the 2012 sea ice minimum in the Beaufort was the result of anomalously large solar absorption that was compounded by an arctic cyclone and other sources of heat such as solar transmission, oceanic upwelling and riverine inputs, but was ultimately made possible through years of preconditioning towards a younger, thinner ice pack. Significant negative trends in sea ice concentration between 1979 and 2012 from June to October, coupled with a tendency towards earlier sea ice reductions have fostered a significant trend of +12.9 MJ m-2 year-1 in cumulative solar absorption, sufficient to melt an additional 4.3 cm m-2 year-1. Overall through preconditioning towards a younger, thinner ice pack the Beaufort Sea has become increasingly susceptible to increased sea ice loss that may render it ice free more frequently in coming years.

Effects of acoustic- and optical-phonon sidebands on the fundamental optical-absorption edge in crystals and disordered semiconductors

NASA Astrophysics Data System (ADS)

Grein, C. H.; John, Sajeev

1990-04-01

We present the results of a parameter-free first-principles theory for the fine structure of the Urbach optical-absorption edge in crystalline and disordered semiconductors. The dominant features are recaptured by means of a simple physical argument based on the most probable potential-well analogy. At finite temperatures, the overall linear exponential Urbach behavior of the subgap optical-absorption coefficient is a consequence of multiple LA-phonon emission and absorption sidebands that accompany the electronic transition. The fine structure of subgap absorption spectra observed in some materials is accounted for by multiple TO-, LO-, and TA-phonon absorption and emission sidebands. Good agreement is found with experimental data on crystalline silicon. The effects of nonadiabaticity in the electron-phonon interaction are calculated.

Research on filling process of fuel and oxidant during detonation based on absorption spectrum technology

NASA Astrophysics Data System (ADS)

Lv, Xiao-Jing; Li, Ning; Weng, Chun-Sheng

2014-12-01

Research on detonation process is of great significance for the control optimization of pulse detonation engine. Based on absorption spectrum technology, the filling process of fresh fuel and oxidant during detonation is researched. As one of the most important products, H2O is selected as the target of detonation diagnosis. Fiber distributed detonation test system is designed to enable the detonation diagnosis under adverse conditions in detonation process. The test system is verified to be reliable. Laser signals at different working frequency (5Hz, 10Hz and 20Hz) are detected. Change of relative laser intensity in one detonation circle is analyzed. The duration of filling process is inferred from the change of laser intensity, which is about 100~110ms. The peak of absorption spectrum is used to present the concentration of H2O during the filling process of fresh fuel and oxidant. Absorption spectrum is calculated, and the change of absorption peak is analyzed. Duration of filling process calculated with absorption peak consisted with the result inferred from the change of relative laser intensity. The pulse detonation engine worked normally and obtained the maximum thrust at 10Hz under experiment conditions. The results are verified through H2O gas concentration monitoring during detonation.

Prebiotics and the absorption of minerals: a review of experimental and human data

USDA-ARS?s Scientific Manuscript database

Dietary factors, including calcium and vitamin D intake, absorption, and status, lifestyle factors including physical activity, and genetics interact to determine peak bone mass. The current recommended dietary intake of calcium (adequate intake, AI) of 1300 mg/day in the United States for adolescen...

The Colour of the Noble Metals.

ERIC Educational Resources Information Center

Poole, R. T.

1983-01-01

Examines the physical basis for colors of noble metals (copper, silver, gold) developed from energy conservation/quantum mechanical view of free electron photoabsorption. Describes production of absorption edges produced by change in density of occupied valence electron states in the d-band, which allows stronger absorption in the visible photon…

Luminescence and Absorption Spectra of C sub 60 Films

DTIC Science & Technology

1991-02-01

J. McKeirnan, J.L Zink, R. Stanley Williams, W.M. Tong, D.A.A. Ohlberg and R.L. Whetten Submitted t DTIC Physical Review Letters ELECT E SFEB 2? 7,19...range at 20K. A 1400 cm"& progression in the a soccerball inflation mode is observed. The low-temperature absorption spectrum exhibits similar fine...ag soccerball inflation mode is observed. The low temperature absorption spectrum exhibits similar fine structure. The characterization of vibronic

The hierarchical porous structure bio-char assessments produced by co-pyrolysis of municipal sewage sludge and hazelnut shell and Cu(II) adsorption kinetics.

PubMed

Zhao, Bing; Xu, Xinyang; Zeng, Fanqiang; Li, Haibo; Chen, Xi

2018-05-04

The co-pyrolysis technology was applied to municipal sewage sludge (MSS) and hazelnut shell with alkaline activating agent K 2 CO 3 under N 2 atmosphere. The innovative bio-char produced by co-pyrolysis had significant physical and chemical characteristics. The specific surface area reached 1990.23 m 2 /g, and the iodine absorption number was 1068.22 mg/g after co-pyrolysis at 850 °C. Although hazelnut shell was a kind of solid waste, it also had abundant cellulose resource, which could contribute to porous structure of bio-char during co-pyrolysis with MSS and decrease total heavy metals contents of raw material to increase security of bio-chars. Meanwhile, the residual fractions of heavy metals in bio-char were above 92.95% after co-pyrolysis at 900 °C except Cd to prevent heavy metals digestion, and the bio-char presented significant immobilization behavior from co-pyrolysis technology. Moreover, the yield and the iodine absorption number of bio-chars under different process variables were analyzed, and it was confirmed that appropriate process variables could contribute the yield and the iodine absorption number of bio-char and prevent to etch pore structure excessively to collapse. The changes of surface functional groups and crystallographic structure before and after co-pyrolysis were analyzed by FTIR and XRD, respectively. The hierarchical porous structure of bio-char was presented by SEM and N 2 adsorption-desorption isotherm. The Cu(II) adsorption capacity of the bio-char was 42.28 mg/g after 24 h, and surface functional groups acted as active binding sites for Cu(II) adsorption. Langmuir model and pseudo-second-order model can describe process of Cu(II) adsorption well.

Up-cycling waste glass to minimal water adsorption/absorption lightweight aggregate by rapid low temperature sintering: optimization by dual process-mixture response surface methodology.

PubMed

Velis, Costas A; Franco-Salinas, Claudia; O'Sullivan, Catherine; Najorka, Jens; Boccaccini, Aldo R; Cheeseman, Christopher R

2014-07-01

Mixed color waste glass extracted from municipal solid waste is either not recycled, in which case it is an environmental and financial liability, or it is used in relatively low value applications such as normal weight aggregate. Here, we report on converting it into a novel glass-ceramic lightweight aggregate (LWA), potentially suitable for high added value applications in structural concrete (upcycling). The artificial LWA particles were formed by rapidly sintering (<10 min) waste glass powder with clay mixes using sodium silicate as binder and borate salt as flux. Composition and processing were optimized using response surface methodology (RSM) modeling, and specifically (i) a combined process-mixture dual RSM, and (ii) multiobjective optimization functions. The optimization considered raw materials and energy costs. Mineralogical and physical transformations occur during sintering and a cellular vesicular glass-ceramic composite microstructure is formed, with strong correlations existing between bloating/shrinkage during sintering, density and water adsorption/absorption. The diametrical expansion could be effectively modeled via the RSM and controlled to meet a wide range of specifications; here we optimized for LWA structural concrete. The optimally designed LWA is sintered in comparatively low temperatures (825-835 °C), thus potentially saving costs and lowering emissions; it had exceptionally low water adsorption/absorption (6.1-7.2% w/wd; optimization target: 1.5-7.5% w/wd); while remaining substantially lightweight (density: 1.24-1.28 g.cm(-3); target: 0.9-1.3 g.cm(-3)). This is a considerable advancement for designing effective environmentally friendly lightweight concrete constructions, and boosting resource efficiency of waste glass flows.

Transient receptor potential (TRP) channels as drug targets for diseases of the digestive system

PubMed Central

Holzer, Peter

2011-01-01

Approximately 20 of the 30 mammalian transient receptor potential (TRP) channel subunits are expressed by specific neurons and cells within the alimentary canal. They subserve important roles in taste, chemesthesis, mechanosensation, pain and hyperalgesia and contribute to the regulation of gastrointestinal motility, absorptive and secretory processes, blood flow, and mucosal homeostasis. In a cellular perspective, TRP channels operate either as primary detectors of chemical and physical stimuli, as secondary transducers of ionotropic or metabotropic receptors, or as ion transport channels. The polymodal sensory function of TRPA1, TRPM5, TRPM8, TRPP2, TRPV1, TRPV3 and TRPV4 enables the digestive system to survey its physical and chemical environment, which is relevant to all processes of digestion. TRPV5 and TRPV6 as well as TRPM6 and TRPM7 contribute to the absorption of Ca2+ and Mg2+, respectively. TRPM7 participates in intestinal pacemaker activity, and TRPC4 transduces muscarinic acetylcholine receptor activation to smooth muscle contraction. Changes in TRP channel expression or function are associated with a variety of diseases/disorders of the digestive system, notably gastro-esophageal reflux disease, inflammatory bowel disease, pain and hyperalgesia in heartburn, functional dyspepsia and irritable bowel syndrome, cholera, hypomagnesemia with secondary hypocalcemia, infantile hypertrophic pyloric stenosis, esophageal, gastrointestinal and pancreatic cancer, and polycystic liver disease. These implications identify TRP channels as promising drug targets for the management of a number of gastrointestinal pathologies. As a result, major efforts are put into the development of selective TRP channel agonists and antagonists and the assessment of their therapeutic potential. PMID:21420431

Finite element computation of multi-physical micropolar transport phenomena from an inclined moving plate in porous media

NASA Astrophysics Data System (ADS)

Shamshuddin, MD.; Anwar Bég, O.; Sunder Ram, M.; Kadir, A.

2018-02-01

Non-Newtonian flows arise in numerous industrial transport processes including materials fabrication systems. Micropolar theory offers an excellent mechanism for exploring the fluid dynamics of new non-Newtonian materials which possess internal microstructure. Magnetic fields may also be used for controlling electrically-conducting polymeric flows. To explore numerical simulation of transport in rheological materials processing, in the current paper, a finite element computational solution is presented for magnetohydrodynamic, incompressible, dissipative, radiative and chemically-reacting micropolar fluid flow, heat and mass transfer adjacent to an inclined porous plate embedded in a saturated homogenous porous medium. Heat generation/absorption effects are included. Rosseland's diffusion approximation is used to describe the radiative heat flux in the energy equation. A Darcy model is employed to simulate drag effects in the porous medium. The governing transport equations are rendered into non-dimensional form under the assumption of low Reynolds number and also low magnetic Reynolds number. Using a Galerkin formulation with a weighted residual scheme, finite element solutions are presented to the boundary value problem. The influence of plate inclination, Eringen coupling number, radiation-conduction number, heat absorption/generation parameter, chemical reaction parameter, plate moving velocity parameter, magnetic parameter, thermal Grashof number, species (solutal) Grashof number, permeability parameter, Eckert number on linear velocity, micro-rotation, temperature and concentration profiles. Furthermore, the influence of selected thermo-physical parameters on friction factor, surface heat transfer and mass transfer rate is also tabulated. The finite element solutions are verified with solutions from several limiting cases in the literature. Interesting features in the flow are identified and interpreted.

Randic and Schultz molecular topological indices and their correlation with some X-ray absorption parameters

NASA Astrophysics Data System (ADS)

Khatri, Sunil; Kekre, Pravin A.; Mishra, Ashutosh

2016-10-01

The properties of a molecular system are affected by the topology of molecule. Therefore many studies have been made where the various physic-chemical properties are correlated with the topological indices. These studies have shown a very good correlation demonstrating the utility of the graph theoretical approach. It is, therefore, very natural to expect that the various physical properties obtained by the X-ray absorption spectra may also show correlation with the topological indices. Some complexes were used to establish correlation between topological indices and some X-ray absorption parameters like chemical shift. The chemical shift is on the higher energy side of the metal edge in these complexes. The result obtained in these studies shows that the topological indices of organic molecule acting as a legands can be used for estimating edge shift theoretically.

Edge physics of the quantum spin Hall insulator from a quantum dot excited by optical absorption.

PubMed

Vasseur, Romain; Moore, Joel E

2014-04-11

The gapless edge modes of the quantum spin Hall insulator form a helical liquid in which the direction of motion along the edge is determined by the spin orientation of the electrons. In order to probe the Luttinger liquid physics of these edge states and their interaction with a magnetic (Kondo) impurity, we consider a setup where the helical liquid is tunnel coupled to a semiconductor quantum dot that is excited by optical absorption, thereby inducing an effective quantum quench of the tunneling. At low energy, the absorption spectrum is dominated by a power-law singularity. The corresponding exponent is directly related to the interaction strength (Luttinger parameter) and can be computed exactly using boundary conformal field theory thanks to the unique nature of the quantum spin Hall edge.

Physical and optical absorption studies of Fe{sup 3+} - ions doped lithium borate glasses containing certain alkaline earths

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhogi, Ashok; Kumar, R. Vijaya; Kistaiah, P., E-mail: pkistaiah@yahoo.com

Iron ion doped lithium borate glasses with the composition 15RO-25Li{sub 2}O-59B{sub 2}O{sub 3}-1Fe{sub 2}O{sub 3} (where R= Ca, Sr and Ba) have been prepared by the conventional melt quenching technique and characterized to investigate the physical and optical properties using XRD, density, molar volume and UV-Visible spectroscopy. The optical absorption spectra exhibit a band at around 460 nm which is assigned to {sup 6}A{sub 1g}(S) → 4E{sub g} (G) of Fe{sup 3+} ions with distorted octahedral symmetry. From ultraviolet absorption edges, the optical band gap and Urbach energies have been evaluated. The effect of alkaline earths on these properties ismore » discussed.« less

[Purification of complicated industrial organic waste gas by complex absorption].

PubMed

Chen, Ding-Sheng; Cen, Chao-Ping; Tang, Zhi-Xiong; Fang, Ping; Chen, Zhi-Hang

2011-12-01

Complicated industrial organic waste gas with the characteristics of low concentration,high wind volume containing inorganic dust and oil was employed the research object by complex absorption. Complex absorption mechanism, process flow, purification equipment and engineering application were studied. Three different surfactants were prepared for the composite absorbent to purify exhaust gas loaded with toluene and butyl acetate, respectively. Results show that the low surface tension of the composite absorbent can improve the removal efficiency of toluene and butyl acetate. With the advantages of the water film, swirl plate and fill absorption device, efficient absorption equipment was developed for the treatment of complicated industrial organic waste gas. It is with superiorities of simple structure, small size, anti-jam and high mass transfer. Based on absorption technology, waste gas treatment process integrated with heating stripping, burning and anaerobic and other processes, so that emissions of waste gas and absorption solution could meet the discharge standards. The technology has been put into practice, such as manufacturing and spraying enterprises.

75 Easy Physics Demonstrations. Teacher Book.

ERIC Educational Resources Information Center

Kardos, Thomas

This book is a collection of classroom demonstrations in physics designed to present basic scientific ideas on a concrete level. The topics covered include: physical change and properties of matter; energy waves and energy forms; absorption of heat; radiant energy; vacuum bottles; kinetic molecular theory; states of matter; pressure of air; work…

Force-controlled absorption in a fully-nonlinear numerical wave tank

NASA Astrophysics Data System (ADS)

Spinneken, Johannes; Christou, Marios; Swan, Chris

2014-09-01

An active control methodology for the absorption of water waves in a numerical wave tank is introduced. This methodology is based upon a force-feedback technique which has previously been shown to be very effective in physical wave tanks. Unlike other methods, an a-priori knowledge of the wave conditions in the tank is not required; the absorption controller being designed to automatically respond to a wide range of wave conditions. In comparison to numerical sponge layers, effective wave absorption is achieved on the boundary, thereby minimising the spatial extent of the numerical wave tank. In contrast to the imposition of radiation conditions, the scheme is inherently capable of absorbing irregular waves. Most importantly, simultaneous generation and absorption can be achieved. This is an important advance when considering inclusion of reflective bodies within the numerical wave tank. In designing the absorption controller, an infinite impulse response filter is adopted, thereby eliminating the problem of non-causality in the controller optimisation. Two alternative controllers are considered, both implemented in a fully-nonlinear wave tank based on a multiple-flux boundary element scheme. To simplify the problem under consideration, the present analysis is limited to water waves propagating in a two-dimensional domain. The paper presents an extensive numerical validation which demonstrates the success of the method for a wide range of wave conditions including regular, focused and random waves. The numerical investigation also highlights some of the limitations of the method, particularly in simultaneously generating and absorbing large amplitude or highly-nonlinear waves. The findings of the present numerical study are directly applicable to related fields where optimum absorption is sought; these include physical wavemaking, wave power absorption and a wide range of numerical wave tank schemes.

Superb electromagnetic wave-absorbing composites based on large-scale graphene and carbon nanotube films.

PubMed

Li, Jinsong; Lu, Weibang; Suhr, Jonghwan; Chen, Hang; Xiao, John Q; Chou, Tsu-Wei

2017-05-24

Graphene has sparked extensive research interest for its excellent physical properties and its unique potential for application in absorption of electromagnetic waves. However, the processing of stable large-scale graphene and magnetic particles on a micrometer-thick conductive support is a formidable challenge for achieving high reflection loss and impedance matching between the absorber and free space. Herein, a novel and simple approach for the processing of a CNT film-Fe 3 O 4 -large scale graphene composite is studied. The Fe 3 O 4 particles with size in the range of 20-200 nm are uniformly aligned along the axial direction of the CNTs. The composite exhibits exceptionally high wave absorption capacity even at a very low thickness. Minimum reflection loss of -44.7 dB and absorbing bandwidth of 4.7 GHz at -10 dB are achieved in composites with one-layer graphene in six-layer CNT film-Fe 3 O 4 prepared from 0.04 M FeCl 3 . Microstructural and theoretical studies of the wave-absorbing mechanism reveal a unique Debye dipolar relaxation with an Eddy current effect in the absorbing bandwidth.

Varied absorption peaks of dual-band metamaterial absorber analysis by using reflection theory

NASA Astrophysics Data System (ADS)

Xiong, Han; Yu, Yan-Tao; Tang, Ming-Chun; Chen, Shi-Yong; Liu, Dan-Ping; Ou, Xiang; Zeng, Hao

2016-03-01

Cross-resonator metamaterial absorbers (MMA) have been widely investigated from microwave to optical frequencies. However, only part of the factors influencing the absorption properties were analyzed in previous works at the same time. In order to completely understand how the spacer thickness, dielectric parameter and incidence angle affect the absorption properties of the dual-band MMA, two sets of simulation were performed. It was found that with increasing incident angles, the low-frequency absorption peak showed a blue shift, while the high-frequency absorption peaks showed a red shift. However, with the increase in spacer thickness, both of the absorption peaks showed a red shift. By using the reflection theory expressions, the physical mechanism of the cross-resonator MMA was well explained. This method provides an effective way to analyze multi-band absorber in technology.

Broadband and tunable high-performance microwave absorption of an ultralight and highly compressible graphene foam.

PubMed

Zhang, Yi; Huang, Yi; Zhang, Tengfei; Chang, Huicong; Xiao, Peishuang; Chen, Honghui; Huang, Zhiyu; Chen, Yongsheng

2015-03-25

The broadband and tunable high-performance microwave absorption properties of an ultralight and highly compressible graphene foam (GF) are investigated. Simply via physical compression, the microwave absorption performance can be tuned. The qualified bandwidth coverage of 93.8% (60.5 GHz/64.5 GHz) is achieved for the GF under 90% compressive strain (1.0 mm thickness). This mainly because of the 3D conductive network. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Plasma Boundary Collisionless Absorption Effects in the Loading of RF Conductors,

DTIC Science & Technology

1979-10-01

a quasi-thermodynamic equilibrium between the charged particles and the applied RF potential. It is clear that the effect of external magnetic fields...AO-AOBI 115 CALIFORNIA UNIV LOS ANBELES PLASMA PHYSICS BROUP F/6O 20/9 PLASMA BOUNDARY COLLISIONLESS ABSORPTION EFFECTS IN THE LbADINGS-E*IC(U) OCT...79 B J MORALES N00OOIATB-C-0NA NLASIED PPB-435 NL mii-hiiiii PLASMA BOUNDARY COLLISIONLESS ABSORPTION EFFECTS IN THE LOADING OF ONDUCTOR) (𔃻.J. Oral

Visible and near-IR spectral reflectance of geologically important materials: A short review

NASA Technical Reports Server (NTRS)

Singer, R. B.

1982-01-01

Examples of reflectance spectra are presented and discussed for various mineral groups including pyroxenes, olivene, phylosilicates, amphiboles, feldspars, oxides and hydroxides, carbonates, and mixtures of minerals. The physical sources of some spectral features are also reviewed such as charge transfer and conduction bands, crystal field absorptions, and vibrational absorptions.

CHARGE-TRANSFER ASSOCIATION AND PARAMAGNETISM OF SOME ORGANIC SYSTEMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eastman, J W

When p-xylene was combined with chloranil in n-heptane, charge-transfer optical absorption was observed. The magnitude of this absorption was used to calculate an equilibrium constant for the formation of a donor-acceptor complex containing one p-xylene was combined with carbon tetrabromide and with carbon tetrachloride in n-heptane, no charge-transfer absorption was observed. Reactions of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) with chloranil (pQCl/ sub 4/) were observed in ethylene dichloride and acetonitrile. In both solvents adduct formation occurred initially, as observed by its charge-transfer absorption. In acetonitrile time-dependent electron spin resonance (ESR) absorption was observed, and it was identified with the positive and negative radicalmore » ions of TMPD and pQCl/sub 4/, respectively. In this case a completely ionized electron transfer had occurred. Chloranil and other quinones were found to react with N,N-dimethylaniline forming a crystal violet salt. The diamagnetic donor-acceptor complexes and also semiquinone radicals are intermediates which were observed. Some physical measurements of the kinetics of this reaction are described and correlated. When fluoranil was allowed to react with dimethylaniline, the hyperfine splitting by the fluorine atoms of the fluoranil radical was not resolved. Characteristics of the ESR absorption by this radical in dimethylaniline are discussed in terms of an electron transfer between the semiquinone and quinone, and between the semiquinone and hydroquinone ion. Paramagnetism was discovered in hydrocarbon-quinone solids. ESR absorption was assigned to imperfections in the solid which was normally diamagnetic. The preparation of these solids and some of their physical characteristics are described. (auth)« less

Optical Hydrogen Absorption Consistent with a Thin Bow Shock Leading the Hot Jupiter HD 189733b

NASA Astrophysics Data System (ADS)

Cauley, P. Wilson; Redfield, Seth; Jensen, Adam G.; Barman, Travis; Endl, Michael; Cochran, William D.

2015-09-01

Bow shocks are ubiquitous astrophysical phenomena resulting from the supersonic passage of an object through a gas. Recently, pre-transit absorption in UV metal transitions of the hot Jupiter (HJ) exoplanets HD 189733b and WASP12-b have been interpreted as being caused by material compressed in a planetary bow shock. Here we present a robust detection of a time-resolved pre-transit, as well as in-transit absorption signature around the HJ exoplanet HD 189733b using high spectral resolution observations of several hydrogen Balmer lines. The line shape of the pre-transit feature and the shape of the timeseries absorption provide the strongest constraints on the morphology and physical characteristics of extended structures around an exoplanet. The in-transit measurements confirm the previous exospheric Hα detection, although the absorption depth measured here is ∼50% lower. The pre-transit absorption feature occurs 125 minutes before the predicted optical transit, a projected linear distance from the planet to the stellar disk of 7.2 Rp. The absorption strength observed in the Balmer lines indicates an optically thick, but physically small, geometry. We model this signal as the early ingress of a planetary bow shock. If the bow shock is mediated by a planetary magnetosphere, the large standoff distance derived from the model suggests a large planetary magnetic field strength of Beq = 28 G. Better knowledge of exoplanet magnetic field strengths is crucial to understanding the role these fields play in planetary evolution and the potential development of life on planets in the habitable zone.

Simultaneous in situ Optical Monitoring Techniques during Crystal Growth of ZnSe by Physical Vapor Transport

NASA Technical Reports Server (NTRS)

Su, C.- H.; Feth, S.; Lehoczky, S. L.

1998-01-01

ZnSe crystals grown in sealed ampoules by the physical vapor transport method were monitored in situ using three techniques, simultaneously. A Michelson interferometer was set-up to observe the growth rate and surface morphological evolution. An interference pattern (interferogram) is formed by the interaction between the reflection of a HeNe laser (632.8 nm wavelength) off the crystal-vapor interface and a reference beam from the same laser. Preliminary results indicate that the rate of growth/thermal-etching can be calculated using analog data acquisition and simple fringe counting techniques. Gross surface features may also be observed using a digital frame grabber and fringe analysis software. The second in situ technique uses optical absorption to determine the partial pressures of the vapor species. The Se2 and Zn vapor species present in the sealed ampoule absorb light at characteristic wavelengths. The optical absorption is determined by monitoring the light intensity difference between the sample and reference beams. The Se2 Partial pressure profile along the length of the ampoule was estimated from the vibronic absorption peaks at 340.5, 350.8, 361.3 and 379.2 nm using the Beer's law constants established in the calibration runs of pure Se. Finally, because the high temperature crystal growth furnace contains windows, in situ visual observation of the growing crystal is also possible. The use of these techniques not only permits in situ investigation of high temperature vapor growth of semiconductors, but also offers the potential for real time feed back on the growing crystal and allows the possibility of actively controlling the growth process.

Device Scale Modeling of Solvent Absorption using MFIX-TFM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carney, Janine E.; Finn, Justin R.

Recent climate change is largely attributed to greenhouse gases (e.g., carbon dioxide, methane) and fossil fuels account for a large majority of global CO 2 emissions. That said, fossil fuels will continue to play a significant role in the generation of power for the foreseeable future. The extent to which CO 2 is emitted needs to be reduced, however, carbon capture and sequestration are also necessary actions to tackle climate change. Different approaches exist for CO 2 capture including both post-combustion and pre-combustion technologies, oxy-fuel combustion and/or chemical looping combustion. The focus of this effort is on post-combustion solvent-absorption technology.more » To apply CO 2 technologies at commercial scale, the availability and maturity and the potential for scalability of that technology need to be considered. Solvent absorption is a proven technology but not at the scale needed by typical power plant. The scale up and down and design of laboratory and commercial packed bed reactors depends heavily on the specific knowledge of two-phase pressure drop, liquid holdup, the wetting efficiency and mass transfer efficiency as a function of operating conditions. Simple scaling rules often fail to provide proper design. Conventional reactor design modeling approaches will generally characterize complex non-ideal flow and mixing patterns using simplified and/or mechanistic flow assumptions. While there are varying levels of complexity used within these approaches, none of these models resolve the local velocity fields. Consequently, they are unable to account for important design factors such as flow maldistribution and channeling from a fundamental perspective. Ideally design would be aided by development of predictive models based on truer representation of the physical and chemical processes that occur at different scales. Computational fluid dynamic (CFD) models are based on multidimensional flow equations with first principle foundations. CFD models can include a more accurate physical description of flow processes and be modified to include more complex behavior. Wetting performance and spatial liquid distribution inside the absorber are recognized as weak areas of knowledge requiring further investigation. CFD tools offer a possible method to investigating such topics and gaining a better understanding of their influence on reactor performance. This report focuses first on describing a hydrodynamic model for countercurrent gas-liquid flow through a packed column and then on the chemistry, heat and mass transfer specific to CO 2 absorption using monoethanolamine (MEA). The indicated model is implemented in MFIX, a CFD open source software package. The user defined functions needed to build this model are described in detail along with the keywords for the corresponding input file. A test case is outlined along with a few results. The example serves to briefly illustrate the developed CFD tool and its potential capability to investigate solvent absorption.« less

Leaf optical system modeled as a stochastic process. [solar radiation interaction with terrestrial vegetation

NASA Technical Reports Server (NTRS)

Tucker, C. J.; Garratt, M. W.

1977-01-01

A stochastic leaf radiation model based upon physical and physiological properties of dicot leaves has been developed. The model accurately predicts the absorbed, reflected, and transmitted radiation of normal incidence as a function of wavelength resulting from the leaf-irradiance interaction over the spectral interval of 0.40-2.50 micron. The leaf optical system has been represented as Markov process with a unique transition matrix at each 0.01-micron increment between 0.40 micron and 2.50 micron. Probabilities are calculated at every wavelength interval from leaf thickness, structure, pigment composition, and water content. Simulation results indicate that this approach gives accurate estimations of actual measured values for dicot leaf absorption, reflection, and transmission as a function of wavelength.

Impacts of Aerosol Direct Effects on the South Asian climate: Assessment of Radiative Feedback Processes Using Model Simulations and Satellite/surface Measurements

NASA Astrophysics Data System (ADS)

Wang, S.; Gautam, R.; Lau, W. K.; Tsay, S.; Sun, W.; Kim, K.; Chern, J.; Colarco, P. R.; Hsu, N. C.; Lin, N.

2011-12-01

Current assessment of aerosol radiative effect is hindered by our incomplete knowledge of aerosol optical properties, especially absorption, and our current inability to quantify physical and microphysical processes. In this research, we investigate direct aerosol radiative effect over heavy aerosol loading areas (e.g., Indo-Gangetic Plains, South/East Asia) and its feedbacks on the South Asian climate during the pre-monsoon season (March-June) using the Purdue Regional Climate Model (PRCM) with prescribed aerosol data derived by the NASA Goddard Earth Observing System Model (GEOS-5). Our modeling domain covers South and East Asia (60-140E and 0-50N) with spatial resolutions of 45 km in horizontal and 28 layers in vertical. The model is integrated from 15 February to 30 June 2008 continuously without nudging (i.e., only forced by initial/boundary conditions). Two numerical experiments are conducted with and without the aerosol-radiation effects. Both simulations are successful in reproducing the synoptic patterns on seasonal-to-interannual time scales and capturing a pre-monsoon feature of the northward rainfall propagation over Indian region in early June which shown in Tropical Rainfall Measuring Mission (TRMM) observation. Preliminary result suggests aerosol-radiation interactions mainly alter surface-atmosphere energetics and further result in an adjustment of the vertical temperature distribution in lower atmosphere (below 700 hPa). The modifications of temperature and associated rainfall and circulation feedbacks on the regional climate will be discussed in the presentation. In addition to modeling study, we will also present the most recent results on aerosol properties, regional aerosol absorption, and radiative forcing estimation based on NASA's operational satellite and ground-based remote sensing. Observational results show spatial gradients in aerosol loading and solar absorption accounting over Indo-Gangetic Plains during the pre-monsoon season. The direct radiative forcing of aerosols at surface to be -19-23 Wm-2 (12-15 % of the surface solar insolation) over NW India is estimated using an observational approach. A comparison of aerosol radiative forcing between numerical simulation and observational estimate will be presented. Overall, this work will demonstrate the aerosol direct effects from both modeling and observation perspectives, and further to assess the physical processes underlying the aerosol radiative feedbacks and possible impacts on the large-scale South Asian monsoon system.

Geophysical aspects of underground fluid dynamics and mineral transformation process

NASA Astrophysics Data System (ADS)

Khramchenkov, Maxim; Khramchenkov, Eduard

2014-05-01

The description of processes of mass exchange between fluid and poly-minerals material in porous media from various kinds of rocks (primarily, sedimentary rocks) have been examined. It was shown that in some important cases there is a storage equation of non-linear diffusion equation type. In addition, process of filtration in un-swelling soils, swelling porous rocks and coupled process of consolidation and chemical interaction between fluid and particles material were considered. In the latter case equations of physical-chemical mechanics of conservation of mass for fluid and particles material were used. As it is well known, the mechanics of porous media is theoretical basis of such branches of science as rock mechanics, soil physics and so on. But at the same moment some complex processes in the geosystems lacks full theoretical description. The example of such processes is metamorphosis of rocks and correspondent variations of stress-strain state. In such processes chemical transformation of solid and fluid components, heat release and absorption, phase transitions, rock destruction occurs. Extensive usage of computational resources in limits of traditional models of the mechanics of porous media cannot guarantee full correctness of obtained models and results. The process of rocks consolidation which happens due to filtration of underground fluids is described from the position of rock mechanics. As an additional impact, let us consider the porous media consolidating under the weight of overlying rock with coupled complex geological processes, as a continuous porous medium of variable mass. Problems of obtaining of correct storage equations for coupled processes of consolidation and mass exchange between underground fluid and skeleton material are often met in catagenesi processes description. The example of such processes is metamorphosis of rocks and correspondent variations of stress-strain state. In such processes chemical transformation of solid and fluid components, heat release and absorption, phase transitions, rock destruction occurs. Extensive usage of computational resources in limits of traditional models of the mechanics of porous media cannot guarantee full correctness of obtained models and results. The present work is dedicated to the retrieval of new ways to formulate and construct such models. It was shown that in some important cases there is a governing equation of non-linear diffusion equation type (well-known Fisher equation). In addition, some geophysical aspects of filtration process in usual non-swelling soils, swelling porous rocks and coupled process of consolidation and chemical interaction between fluid and skeleton material, including earth quakes, are considered.

Coherent perfect absorption in deeply subwavelength films in the single-photon regime

PubMed Central

Roger, Thomas; Vezzoli, Stefano; Bolduc, Eliot; Valente, Joao; Heitz, Julius J. F.; Jeffers, John; Soci, Cesare; Leach, Jonathan; Couteau, Christophe; Zheludev, Nikolay I.; Faccio, Daniele

2015-01-01

The technologies of heating, photovoltaics, water photocatalysis and artificial photosynthesis depend on the absorption of light and novel approaches such as coherent absorption from a standing wave promise total dissipation of energy. Extending the control of absorption down to very low light levels and eventually to the single-photon regime is of great interest and yet remains largely unexplored. Here we demonstrate the coherent absorption of single photons in a deeply subwavelength 50% absorber. We show that while the absorption of photons from a travelling wave is probabilistic, standing wave absorption can be observed deterministically, with nearly unitary probability of coupling a photon into a mode of the material, for example, a localized plasmon when this is a metamaterial excited at the plasmon resonance. These results bring a better understanding of the coherent absorption process, which is of central importance for light harvesting, detection, sensing and photonic data processing applications. PMID:25991584

The effect of colouring agent on the physical properties of glass ceramic produced from waste glass for antimicrobial coating deposition

NASA Astrophysics Data System (ADS)

Juoi, J. M.; Ayoob, N. F.; Rosli, Z. M.; Rosli, N. R.; Husain, K.

2016-07-01

Domestic waste glass is utilized as raw material for the production of glass ceramic material (GCM) via sinter crystallisation route. The glass ceramic material in a form of tiles is to be utilized for the deposition of Ag-TiO2 antimicrobial coating. Two types of soda lime glass (SLG) that are non-coloured and green SLG are utilised as main raw materials during the batch formulation in order to study the effect of colouring agent (Fe2O3) on the physical and mechanical properties of glass ceramic produced. Glass powder were prepared by crushing bottles using hammer milled with milling machine and sieved until they passed through 75 µm sieve. The process continues by mixing glass powder with ball clay with ratio of 95:5 wt. %, 90:10 wt. % and 85:15 wt. %. Each batch mixture was then uniaxial pressed and sintered at 800°C, 825 °C and 850 °C. The physical and mechanical properties were then determined and compared between those produced from non-coloured and green coloured SLG in order to evaluate the effect of colouring agent (Fe2O3) on the GCM produced. The optimum properties of non-coloured SLG is produced with smaller ball clay content (10 wt. %) compared to green SLG (15 wt. %). The physical properties (determined thru ASTM C373) of the optimized GCM produced from non-coloured SLG and green SLG are 0.69 % of porosity, 1.92 g/cm3 of bulk density, 0.36 % of water absorption; and 1.96 % of porosity, 2.69 g/cm3 of bulk density, 0.73 % of water absorption; respectively. Results also indicate that the most suitable temperature in producing GCM from both glasses with optimized physical and mechanical properties is at 850 °C.

During air cool process aerosol absorption detection with photothermal interferometry

NASA Astrophysics Data System (ADS)

Li, Baosheng; Xu, Limei; Huang, Junling; Ma, Fei; Wang, Yicheng; Li, Zhengqiang

2014-11-01

This paper studies the basic principle of laser photothermal interferometry method of aerosol particles absorption coefficient. The photothermal interferometry method with higher accuracy and lower uncertainty can directly measure the absorption coefficient of atmospheric aerosols and not be affected by scattered light. With Jones matrix expression, the math expression of a special polarization interferometer is described. This paper using folded Jamin interferometer, which overcomes the influence of vibration on measuring system. Interference come from light polarization beam with two orthogonal and then combine to one beam, finally aerosol absorption induced refractive index changes can be gotten with four beam of phase orthogonal light. These kinds of styles really improve the stability of system and resolution of the system. Four-channel detections interact with interference fringes, to reduce the light intensity `zero drift' effect on the system. In the laboratory, this device typical aerosol absorption index, it shows that the result completely agrees with actual value. After heated by laser, cool process of air also show the process of aerosol absorption. This kind of instrument will be used to monitor ambient aerosol absorption and suspended particulate matter chemical component. Keywords: Aerosol absorption coefficient; Photothermal interferometry; Suspended particulate matter.

High Affinity Macrocycle Threading by a Near-Infrared Croconaine Dye with Flanking Polymer Chains

PubMed Central

Liu, Wenqi; Peck, Evan M.; Smith, Bradley D.

2016-01-01

Croconaine dyes have narrow and intense absorption bands at ~800 nm, very weak fluorescence, and high photostabilities, which combine to make them very attractive chromophores for absorption-based imaging or laser heating technologies. The physical supramolecular properties of croconaine dyes have rarely been investigated, especially in water. This study focuses on a molecular threading process that encapsulates a croconaine dye inside a tetralactam macrocycle in organic or aqueous solvent. Macrocycle association and rate constant data are reported for a series of croconaine structures with different substituents attached to the ends of the dye. The association constants were highest in water (Ka ~109 M−1), and the threading rate constants (kon) increased in the solvent order H2O > MeOH > CHCl3. Systematic variation of croconaine substituents located just outside the croconaine/macrocycle complexation interface hardly changed Ka but had a strong influence on kon. A croconaine dye with N-propyl groups at each end of the structure exhibited a desirable mixture of macrocycle threading properties; that is, there was rapid and quantitative croconaine/macrocycle complexation at relatively high concentrations in water, and no dissociation of the pre-assembled complex when it was diluted into a solution of fetal bovine serum, even after laser induced photothermal heating of the solution. The combination of favorable near-infrared absorption properties and tunable mechanical stability makes threaded croconaine/macrocycle complexes very attractive as molecular probes or as supramolecular composites for various applications in absorption-based imaging or photothermal therapy. PMID:26807599

Computational study of hot electron generation and energy transport in intense laser produced hot dense matter

NASA Astrophysics Data System (ADS)

Mishra, Rohini

Present ultra high power lasers are capable of producing high energy density (HED) plasmas, in controlled way, with a density greater than solid density and at a high temperature of keV (1 keV ˜ 11,000,000° K). Matter in such extreme states is particularly interesting for (HED) physics such as laboratory studies of planetary and stellar astrophysics, laser fusion research, pulsed neutron source etc. To date however, the physics in HED plasma, especially, the energy transport, which is crucial to realize applications, has not been understood well. Intense laser produced plasmas are complex systems involving two widely distinct temperature distributions and are difficult to model by a single approach. Both kinetic and collisional process are equally important to understand an entire process of laser-solid interaction. By implementing atomic physics models, such as collision, ionization, and radiation damping, self consistently, in state-of-the-art particle-in-cell code (PICLS) has enabled to explore the physics involved in the HED plasmas. Laser absorption, hot electron transport, and isochoric heating physics in laser produced hot dense plasmas are studied with a help of PICLS simulations. In particular, a novel mode of electron acceleration, namely DC-ponderomotive acceleration, is identified in the super intense laser regime which plays an important role in the coupling of laser energy to a dense plasma. Geometric effects on hot electron transport and target heating processes are examined in the reduced mass target experiments. Further, pertinent to fast ignition, laser accelerated fast electron divergence and transport in the experiments using warm dense matter (low temperature plasma) is characterized and explained.

Fully kinetic particle simulations of high pressure streamer propagation

NASA Astrophysics Data System (ADS)

Rose, David; Welch, Dale; Thoma, Carsten; Clark, Robert

2012-10-01

Streamer and leader formation in high pressure devices is a dynamic process involving a hierarchy of physical phenomena. These include elastic and inelastic particle collisions in the gas, radiation generation, transport and absorption, and electrode interactions. We have performed 2D and 3D fully EM implicit particle-in-cell simulation model of gas breakdown leading to streamer formation under DC and RF fields. The model uses a Monte Carlo treatment for all particle interactions and includes discrete photon generation, transport, and absorption for ultra-violet and soft x-ray radiation. Central to the realization of this fully kinetic particle treatment is an algorithm [D. R. Welch, et al., J. Comp. Phys. 227, 143 (2007)] that manages the total particle count by species while preserving the local momentum distribution functions and conserving charge. These models are being applied to the analysis of high-pressure gas switches [D. V. Rose, et al., Phys. Plasmas 18, 093501 (2011)] and gas-filled RF accelerator cavities [D. V. Rose, et al. Proc. IPAC12, to appear].

Interfacial dynamics and solar fuel formation in dye-sensitized photoelectrosynthesis cells.

PubMed

Song, Wenjing; Chen, Zuofeng; Glasson, Christopher R K; Hanson, Kenneth; Luo, Hanlin; Norris, Michael R; Ashford, Dennis L; Concepcion, Javier J; Brennaman, M Kyle; Meyer, Thomas J

2012-08-27

Dye-sensitized photoelectrosynthesis cells (DSPECs) represent a promising approach to solar fuels with solar-energy storage in chemical bonds. The targets are water splitting and carbon dioxide reduction by water to CO, other oxygenates, or hydrocarbons. DSPECs are based on dye-sensitized solar cells (DSSCs) but with photoexcitation driving physically separated solar fuel half reactions. A systematic basis for DSPECs is available based on a modular approach with light absorption/excited-state electron injection, and catalyst activation assembled in integrated structures. Progress has been made on catalysts for water oxidation and CO(2) reduction, dynamics of electron injection, back electron transfer, and photostability under conditions appropriate for water splitting. With added reductive scavengers, as surrogates for water oxidation, DSPECs have been investigated for hydrogen generation based on transient absorption and photocurrent measurements. Detailed insights are emerging which define kinetic and thermodynamic requirements for the individual processes underlying DSPEC performance. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of ion-assisted induced absorption in A-Si thin-films used for multivariate optical computing

NASA Astrophysics Data System (ADS)

Nayak, Aditya B.; Price, James M.; Dai, Bin; Perkins, David; Chen, Ding Ding; Jones, Christopher M.

2015-06-01

Multivariate optical computing (MOC), an optical sensing technique for analog calculation, allows direct and robust measurement of chemical and physical properties of complex fluid samples in high-pressure/high-temperature (HP/HT) downhole environments. The core of this MOC technology is the integrated computational element (ICE), an optical element with a wavelength-dependent transmission spectrum designed to allow the detector to respond sensitively and specifically to the analytes of interest. A key differentiator of this technology is it uses all of the information present in the broadband optical spectrum to determine the proportion of the analyte present in a complex fluid mixture. The detection methodology is photometric in nature; therefore, this technology does not require a spectrometer to measure and record a spectrum or a computer to perform calculations on the recorded optical spectrum. The integrated computational element is a thin-film optical element with a specific optical response function designed for each analyte. The optical response function is achieved by fabricating alternating layers of high-index (a-Si) and low-index (SiO2) thin films onto a transparent substrate (BK7 glass) using traditional thin-film manufacturing processes (e.g., ion-assisted e-beam vacuum deposition). A proprietary software and process are used to control the thickness and material properties, including the optical constants of the materials during deposition to achieve the desired optical response function. The ion-assisted deposition is useful for controlling the densification of the film, stoichiometry, and material optical constants as well as to achieve high deposition growth rates and moisture-stable films. However, the ion-source can induce undesirable absorption in the film; and subsequently, modify the optical constants of the material during the ramp-up and stabilization period of the e-gun and ion-source, respectively. This paper characterizes the unwanted absorption in the a-Si thin-film using advanced thin-film metrology methods, including spectroscopic ellipsometry and Fourier transform infrared (FTIR) spectroscopy. The resulting analysis identifies a fundamental mechanism contributing to this absorption and a method for minimizing and accounting for the unwanted absorption in the thin-film such that the exact optical response function can be achieved.

HAI: A new TDLAS hygrometer for the HALO research aircraft

NASA Astrophysics Data System (ADS)

Klostermann, Tim; Afchine, Armin; Barthel, Jochen; Höh, Matthias; Wagner, Steven; Witzel, Oliver; Saathoff, Harald; Schiller, Cornelius; Ebert, Volker

2010-05-01

Water vapor is the most important greenhouse gas in the Earth's atmosphere and a key component for several physical and chemical processes. Therefore it is a key parameter to be measured during most research campaigns. The Hygrometer for Atmospheric Investigations (HAI) is especially designed for operations on the research aircraft HALO (High Altitude and LOng range research aircraft). HAI permits both, the in-situ measurement of water vapor with an open-path cell and the measurement of total water with an extractive close-path absorption cell. We are using TDLAS (Tunable Diode Laser Absorption Spectroscopy) in two water absorption bands with different line strength to increase the dynamical range. With this concept it is possible to measure from the middle troposphere up to the stratosphere. The open-path cell outside of the fuselage consists of a robust, aerodynamically designed aluminum structure with a single integrated White-cell for both laser beams. Although the mirror separation is only 15cm the cell allows an open absorption path of 4.8m. The detection of higher H2O concentrations is realized with a fiber coupled 1.4µm DFB diode laser. Inside the UTLS layer were small concentrations in the low ppm range are common, we employ up to 20 times stronger fundamental ro-vibration lines of the water molecule near 2.6µm. To supply this, the fiber coupled 2.6µm laser setup was developed and is a part of the HAI. Both detection wavelengths are introduced in the same open path cell via glass fibers which provide water measurements with a minimum of parasitic absorption. We will present the spectrometer design for high-quality airborne water measurements. Furthermore, first laboratory measurements will be shown.

Electroencephalographic correlates of states of concentrative meditation.

PubMed

DeLosAngeles, Dylan; Williams, Graham; Burston, John; Fitzgibbon, Sean P; Lewis, Trent W; Grummett, Tyler S; Clark, C Richard; Pope, Kenneth J; Willoughby, John O

2016-12-01

Meditative techniques aim for and meditators report states of mental alertness and focus, concurrent with physical and emotional calm. We aimed to determine the electroencephalographic (EEG) correlates of five states of Buddhist concentrative meditation, particularly addressing a correlation with meditative level. We studied 12 meditators and 12 pair-matched meditation-naïve participants using high-resolution scalp-recorded EEG. To maximise reduction of EMG, data were pre-processed using independent component analysis and surface Laplacian transformed data. Two non-meditative and five meditative states were used: resting baseline, mind-wandering, absorptions 1, 2, 3, 4 and 5 (corresponding to four levels of absorption and an absorption with a different object of focus, otherwise equivalent to level 4; these five meditative states produce repeatable, distinctly different experiences for experienced meditators). The experimental protocol required participants to experience the states in the order listed above, followed immediately by the reverse. We then calculated EEG power in standard frequency bands from 1 to 80Hz. We observed decreases of central scalp beta (13-25Hz), and central low gamma (25-48Hz) power in meditators during deeper absorptions. In contrast, we identified increases in frontal midline and temporo-parietal theta power in meditators, again, during deeper absorptions. Alpha activity was increased over all meditative states, not depth-related. This study demonstrates that the subjective experiences of deepening meditation partially correspond to measures of EEG. Our results are in accord with prior studies on non-graded meditative states. These results are also consistent with increased theta correlating with tightness of focus, and reduced beta/gamma with the desynchronization associated with enhanced alertness. Copyright © 2016. Published by Elsevier B.V.

Effect of autocontrol micromotion intramedullary interlocking nail on fracture healing: an experimental study.

PubMed

Xu, Wei-zhou; Guo, Xiao-dong; Zhao, Ju-cai; Wang, Yi-jin

2006-06-01

To investigate the effect of autocontrol micromotion locking nail (AMLN) on experimental fracture healing and its mechanism. 16 goats undergoing both sides of transverse osteotomy of the femoral shafts were fixed intramedullary with AMLN and Gross-Kempf (GK) nail, respectively. The follow-up time was 7, 14, 28 and 56 days. Roentgenographic, biomechanical, histological, scanning electromicroscopic and biochemical analyses were done. (1) The strength of anticompression, antiflexion and antitorsion in the fractural end in the AMLN-fixed group was higher than that of GK nail-fixed group; whereas, the rate of stress shelter in the fractured end decreased significantly (P<0.01). (2) The content of the total collagen, insoluble collagen, calcium and phosphate in the AMLN-fixed group was higher than that in the GK nail-fixed group (P<0.05). (3) Histological observation and quantitative analysis of calluses revealed that AMLN could promote the growth of bridge calluses and periosteum calluses. Hence the fracture healing and remolding process achieved early, which was much better than traditional GK nail fixation. (P<0.05). (4) 7-14 days postoperation, the calluses of AMLN-fixed group was flourish and camellarly arranged and the collagen fibril formed constantly in the absorption lacuna of bone trabecula. 28-56 days postoperation, the collagen fibril was flourish around the absorption lacuna and was parallel to the bone's longitudinal axis. Active bony absorption and formation were seen, so was remolding and rebuilding. Haversian system was intact and the bony structural net was very tenacious because of the deposition of calcium salt. None of the above findings was observed in the GK nail-fixed group. The design of AMLN accords well with the plastic fixation theory. As the geometry ametabolic system constituted by the intramedullary fixation instruments and the proximal and distal end of the fracture is very firm and stable, the disturbance to the physical stress distributed in the fractural end is light. The generation and conduct of the intermittent physical stress between the fractural parts could reach the balance between stress conduct and stress protection. The feature that the healing and remolding take place at the same time speeds up the fractural healing process.

Correction to the Beer-Lambert-Bouguer law for optical absorption.

PubMed

Abitan, Haim; Bohr, Henrik; Buchhave, Preben

2008-10-10

The Beer-Lambert-Bouguer absorption law, known as Beer's law for absorption in an optical medium, is precise only at power densities lower than a few kW. At higher power densities this law fails because it neglects the processes of stimulated emission and spontaneous emission. In previous models that considered those processes, an analytical expression for the absorption law could not be obtained. We show here that by utilizing the Lambert W-function, the two-level energy rate equation model is solved analytically, and this leads into a general absorption law that is exact because it accounts for absorption as well as stimulated and spontaneous emission. The general absorption law reduces to Beer's law at low power densities. A criterion for its application is given along with experimental examples. (c) 2008 Optical Society of America

Design of Quad-Band Terahertz Metamaterial Absorber Using a Perforated Rectangular Resonator for Sensing Applications.

PubMed

Xie, Qin; Dong, Guangxi; Wang, Ben-Xin; Huang, Wei-Qing

2018-05-08

Quad-band terahertz absorber with single-sized metamaterial design formed by a perforated rectangular resonator on a gold substrate with a dielectric gap in between is investigated. The designed metamaterial structure enables four absorption peaks, of which the first three peaks have large absorption coefficient while the last peak possesses a high Q (quality factor) value of 98.33. The underlying physical mechanisms of these peaks are explored; it is found that their near-field distributions are different. Moreover, the figure of merit (FOM) of the last absorption peak can reach 101.67, which is much higher than that of the first three absorption modes and even absorption bands of other works operated in the terahertz frequency. The designed device with multiple-band absorption and high FOM could provide numerous potential applications in terahertz technology-related fields.

Perfect absorption in nanotextured thin films via Anderson-localized photon modes

NASA Astrophysics Data System (ADS)

Aeschlimann, Martin; Brixner, Tobias; Differt, Dominik; Heinzmann, Ulrich; Hensen, Matthias; Kramer, Christian; Lükermann, Florian; Melchior, Pascal; Pfeiffer, Walter; Piecuch, Martin; Schneider, Christian; Stiebig, Helmut; Strüber, Christian; Thielen, Philip

2015-10-01

The enhancement of light absorption in absorber layers is crucial in a number of applications, including photovoltaics and thermoelectrics. The efficient use of natural resources and physical constraints such as limited charge extraction in photovoltaic devices require thin but efficient absorbers. Among the many different strategies used, light diffraction and light localization at randomly nanotextured interfaces have been proposed to improve absorption. Although already exploited in commercial devices, the enhancement mechanism for devices with nanotextured interfaces is still subject to debate. Using coherent two-dimensional nanoscopy and coherent light scattering, we demonstrate the existence of localized photonic states in nanotextured amorphous silicon layers as used in commercial thin-film solar cells. Resonant absorption in these states accounts for the enhanced absorption in the long-wavelength cutoff region. Our observations establish that Anderson localization—that is, strong localization—is a highly efficient resonant absorption enhancement mechanism offering interesting opportunities for the design of efficient future absorber layers.

Design of Quad-Band Terahertz Metamaterial Absorber Using a Perforated Rectangular Resonator for Sensing Applications

NASA Astrophysics Data System (ADS)

Xie, Qin; Dong, Guangxi; Wang, Ben-Xin; Huang, Wei-Qing

2018-05-01

Quad-band terahertz absorber with single-sized metamaterial design formed by a perforated rectangular resonator on a gold substrate with a dielectric gap in between is investigated. The designed metamaterial structure enables four absorption peaks, of which the first three peaks have large absorption coefficient while the last peak possesses a high Q (quality factor) value of 98.33. The underlying physical mechanisms of these peaks are explored; it is found that their near-field distributions are different. Moreover, the figure of merit (FOM) of the last absorption peak can reach 101.67, which is much higher than that of the first three absorption modes and even absorption bands of other works operated in the terahertz frequency. The designed device with multiple-band absorption and high FOM could provide numerous potential applications in terahertz technology-related fields.

[INVITED] Coherent perfect absorption of electromagnetic wave in subwavelength structures

NASA Astrophysics Data System (ADS)

Yan, Chao; Pu, Mingbo; Luo, Jun; Huang, Yijia; Li, Xiong; Ma, Xiaoliang; Luo, Xiangang

2018-05-01

Electromagnetic (EM) absorption is a common process by which the EM energy is transformed into other kinds of energy in the absorber, for example heat. Perfect absorption of EM with structures at subwavelength scale is important for many practical applications, such as stealth technology, thermal control and sensing. Coherent perfect absorption arises from the interplay of interference and absorption, which can be interpreted as a time-reversed process of lasing or EM emitting. It provides a promising way for complete absorption in both nanophotonics and electromagnetics. In this review, we discuss basic principles and properties of a coherent perfect absorber (CPA). Various subwavelength structures including thin films, metamaterials and waveguide-based structures to realize CPAs are compared. We also discuss the potential applications of CPAs.

Investigation of Diode Pumped Alkali Laser Atmospheric Transmission Using Tunable Diode Laser Absorption Spectroscopy

DTIC Science & Technology

2012-09-01

atmosphere”. Applied Physics B: Lasers and Optics, 82(1):133–140, 2006. 11. Barrass, S., Y. Grard, R.J. Holdsworth, and P.A. Martin . “Near-infrared tun...15. Brown, M. S., S. Williams, C. D. Lindstrom , and D. L. Barone. Progress in Applying Tunable Diode Laser Absorption Spectroscopy to Scramjet

Analysis of laser remote fusion cutting based on a mathematical model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matti, R. S.; Department of Mechanical Engineering, College of Engineering, University of Mosul, Mosul; Ilar, T.

Laser remote fusion cutting is analyzed by the aid of a semi-analytical mathematical model of the processing front. By local calculation of the energy balance between the absorbed laser beam and the heat losses, the three-dimensional vaporization front can be calculated. Based on an empirical model for the melt flow field, from a mass balance, the melt film and the melting front can be derived, however only in a simplified manner and for quasi-steady state conditions. Front waviness and multiple reflections are not modelled. The model enables to compare the similarities, differences, and limits between laser remote fusion cutting, lasermore » remote ablation cutting, and even laser keyhole welding. In contrast to the upper part of the vaporization front, the major part only slightly varies with respect to heat flux, laser power density, absorptivity, and angle of front inclination. Statistical analysis shows that for high cutting speed, the domains of high laser power density contribute much more to the formation of the front than for low speed. The semi-analytical modelling approach offers flexibility to simplify part of the process physics while, for example, sophisticated modelling of the complex focused fibre-guided laser beam is taken into account to enable deeper analysis of the beam interaction. Mechanisms like recast layer generation, absorptivity at a wavy processing front, and melt film formation are studied too.« less

Analysis of laser remote fusion cutting based on a mathematical model

NASA Astrophysics Data System (ADS)

Matti, R. S.; Ilar, T.; Kaplan, A. F. H.

2013-12-01

Laser remote fusion cutting is analyzed by the aid of a semi-analytical mathematical model of the processing front. By local calculation of the energy balance between the absorbed laser beam and the heat losses, the three-dimensional vaporization front can be calculated. Based on an empirical model for the melt flow field, from a mass balance, the melt film and the melting front can be derived, however only in a simplified manner and for quasi-steady state conditions. Front waviness and multiple reflections are not modelled. The model enables to compare the similarities, differences, and limits between laser remote fusion cutting, laser remote ablation cutting, and even laser keyhole welding. In contrast to the upper part of the vaporization front, the major part only slightly varies with respect to heat flux, laser power density, absorptivity, and angle of front inclination. Statistical analysis shows that for high cutting speed, the domains of high laser power density contribute much more to the formation of the front than for low speed. The semi-analytical modelling approach offers flexibility to simplify part of the process physics while, for example, sophisticated modelling of the complex focused fibre-guided laser beam is taken into account to enable deeper analysis of the beam interaction. Mechanisms like recast layer generation, absorptivity at a wavy processing front, and melt film formation are studied too.

The Physics of Marine Biology.

ERIC Educational Resources Information Center

Conn, Kathleen

1992-01-01

Discusses ways in which marine biology can be integrated into the physics classroom. Topics suggested for incorporation include the harmonic motion of ocean waves, ocean currents, the interaction of visible light with ocean water, pressure, light absorption, and sound transfer in water. (MDH)

[Absorption and metabolism of Chuanxiong Rhizoma decoction with multi-component sequential metabolism method].

PubMed

Liu, Yang; Luo, Zhi-Qiang; Lv, Bei-Ran; Zhao, Hai-Yu; Dong, Ling

2016-04-01

The multiple components in Chinese herbal medicines (CHMS) will experience complex absorption and metabolism before entering the blood system. Previous studies often lay emphasis on the components in blood. However, the dynamic and sequential absorption and metabolism process following multi-component oral administration has not been studied. In this study, the in situ closed-loop method combined with LC-MS techniques were employed to study the sequential process of Chuanxiong Rhizoma decoction (RCD). A total of 14 major components were identified in RCD. Among them, ferulic acid, senkyunolide J, senkyunolide I, senkyunolide F, senkyunolide G, and butylidenephthalide were detected in all of the samples, indicating that the six components could be absorbed into blood in prototype. Butylphthalide, E-ligustilide, Z-ligustilide, cnidilide, senkyunolide A and senkyunolide Q were not detected in all the samples, suggesting that the six components may not be absorbed or metabolized before entering the hepatic portal vein. Senkyunolide H could be metabolized by the liver, while senkyunolide M could be metabolized by both liver and intestinal flora. This study clearly demonstrated the changes in the absorption and metabolism process following multi-component oral administration of RCD, so as to convert the static multi-component absorption process into a comprehensive dynamic and continuous absorption and metabolism process. Copyright© by the Chinese Pharmaceutical Association.

Infrared spectroscopic study of the synthetic Mg-Ni talc series

NASA Astrophysics Data System (ADS)

Blanchard, Marc; Méheut, Merlin; Delon, Louise; Poirier, Mathilde; Micoud, Pierre; Le Roux, Christophe; Martin, François

2018-05-01

Five talc samples [(Mg,Ni)3Si4O10(OH)2] covering the entire Mg-Ni solid solution were synthesized following a recently developed and patented process (Dumas et al., Process for preparing a composition comprising synthetic mineral particles and composition, 2013a; Procédé de préparation d'une composition comprenant des particules minérales synthétiques et composition, 2013b), which produces sub-micron talc particles replying to industrial needs. Near- and mid-infrared spectra were collected and compared to infrared spectra modeled from first-principles calculations based on density functional theory. The good agreement between experimental and theoretical spectra allowed assigning unambiguously all absorption bands. We focused in particular on the four main OH stretching bands, which represent good probes of their local physical and chemical environment. The description of the vibrational modes at the origin of these absorption bands and the theoretical determination of absorption coefficients provide a firm basis for quantifying the talc chemical composition from infrared spectroscopy and for discussing the distribution of divalent cations in the octahedral sheet. Results confirm that these synthetic talc samples have a similar structure as natural talc, with a random distribution of Mg and Ni atoms. They only differ from natural talc by their hydrophilic character, which is due to their large proportion of reactive sites on sheet edges due to sub-micronic size of the particles. Therefore, the contribution on infrared spectra of hydroxyls adsorbed on edge sites has also been investigated by computing the infrared signature of hydroxyls of surface models.

A digital frequency stabilization system of external cavity diode laser based on LabVIEW FPGA

NASA Astrophysics Data System (ADS)

Liu, Zhuohuan; Hu, Zhaohui; Qi, Lu; Wang, Tao

2015-10-01

Frequency stabilization for external cavity diode laser has played an important role in physics research. Many laser frequency locking solutions have been proposed by researchers. Traditionally, the locking process was accomplished by analog system, which has fast feedback control response speed. However, analog system is susceptible to the effects of environment. In order to improve the automation level and reliability of the frequency stabilization system, we take a grating-feedback external cavity diode laser as the laser source and set up a digital frequency stabilization system based on National Instrument's FPGA (NI FPGA). The system consists of a saturated absorption frequency stabilization of beam path, a differential photoelectric detector, a NI FPGA board and a host computer. Many functions, such as piezoelectric transducer (PZT) sweeping, atomic saturation absorption signal acquisition, signal peak identification, error signal obtaining and laser PZT voltage feedback controlling, are totally completed by LabVIEW FPGA program. Compared with the analog system, the system built by the logic gate circuits, performs stable and reliable. User interface programmed by LabVIEW is friendly. Besides, benefited from the characteristics of reconfiguration, the LabVIEW program is good at transplanting in other NI FPGA boards. Most of all, the system periodically checks the error signal. Once the abnormal error signal is detected, FPGA will restart frequency stabilization process without manual control. Through detecting the fluctuation of error signal of the atomic saturation absorption spectrum line in the frequency locking state, we can infer that the laser frequency stability can reach 1MHz.

Resonantly enhanced multiple exciton generation through below-band-gap multi-photon absorption in perovskite nanocrystals.

PubMed

Manzi, Aurora; Tong, Yu; Feucht, Julius; Yao, En-Ping; Polavarapu, Lakshminarayana; Urban, Alexander S; Feldmann, Jochen

2018-04-17

Multi-photon absorption and multiple exciton generation represent two separate strategies for enhancing the conversion efficiency of light into usable electric power. Targeting below-band-gap and above-band-gap energies, respectively, to date these processes have only been demonstrated independently. Here we report the combined interaction of both nonlinear processes in CsPbBr 3 perovskite nanocrystals. We demonstrate nonlinear absorption over a wide range of below-band-gap excitation energies (0.5-0.8 E g ). Interestingly, we discover high-order absorption processes, deviating from the typical two-photon absorption, at specific energetic positions. These energies are associated with a strong enhancement of the photoluminescence intensity by up to 10 5 . The analysis of the corresponding energy levels reveals that the observed phenomena can be ascribed to the resonant creation of multiple excitons via the absorption of multiple below-band-gap photons. This effect may open new pathways for the efficient conversion of optical energy, potentially also in other semiconducting materials.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kashkooli, Ali Ghorbani; Foreman, Evan; Farhad, Siamak

In this study, synchrotron X-ray computed tomography has been utilized using two different imaging modes, absorption and Zernike phase contrast, to reconstruct the real three-dimensional (3D) morphology of nanostructured Li 4Ti 5O 12 (LTO) electrodes. The morphology of the high atomic number active material has been obtained using the absorption contrast mode, whereas the percolated solid network composed of active material and carbon-doped polymer binder domain (CBD) has been obtained using the Zernike phase contrast mode. The 3D absorption contrast image revealed that some LTO nano-particles tend to agglomerate and form secondary micro-sized particles with varying degrees of sphericity. Themore » tortuosity of electrode’s pore and solid phases were found to have directional dependence, different from Bruggeman’s tortuosity commonly used in macro-homogeneous models. The electrode’s heterogeneous structure was investigated by developing a numerical model to simulate galvanostatic discharge process using the Zernike phase contrast mode. The inclusion of CBD in the Zernike phase contrast results in an integrated percolated network of active material and CBD that is highly suited for continuum modeling. As a result, the simulation results highlight the importance of using the real 3D geometry since the spatial distribution of physical and electrochemical properties have a strong non-uniformity due to microstructural heterogeneities.« less

Structural, optical, physical and electrical properties of V2O5.SrO.B2O3 glasses.

PubMed

Sindhu, S; Sanghi, S; Agarwal, A; Seth, V P; Kishore, N

2006-05-01

The present work aims to study the structure and variation of optical band gap, density and dc electrical conductivity in vanadium strontium borate glasses. The glass systems xV2O5.(40-x)SrO.60B2O3 and xV2O5.(60-x)B2O3.40SrO with x varying from 0 to 20 mol% were prepared by normal melt quench technique. Structural studies were made by recording IR transmission spectra. The fundamental absorption edge for all the glasses was analyzed in terms of the theory proposed by Davis and Mott. The position of absorption edge and hence the value of the optical band gap was found to depend on the semiconducting glass composition. The absorption in these glasses is believed to be associated with indirect transitions. The origin of Urbach energy is associated with the phonon-assisted indirect transitions. The change in both density and molar volume was discussed in terms of the structural modifications that take place in the glass matrix on addition of V2O5. dc conductivity of the glass systems is also reported. The change of conductivity and activation energy with composition indicates that the conduction process varies from ionic to polaronic one.

Spectrally resolved opacities and Rosseland and Planck mean opacities of lowly ionized gold plasmas: a detailed level-accounting investigation.

PubMed

Zeng, Jiaolong; Yuan, Jianmin

2007-08-01

Calculation details of radiative opacity for lowly ionized gold plasmas by using our developed fully relativistic detailed level-accounting approach are presented to show the importance of accurate atomic data for a quantitative reproduction of the experimental observations. Even though a huge number of transition lines are involved in the radiative absorption of high- Z plasmas so that one believes that statistical models can often give a reasonable description of their opacities, we first show in detail that an adequate treatment of physical effects, in particular the configuration interaction (including the core-valence electron correlation), is essential to produce atomic data of bound-bound and bound-free processes for gold plasmas, which are accurate enough to correctly explain the relative intensity of two strong absorption peaks experimentally observed located near photon energy of 70 and 80 eV. A detailed study is also carried out for gold plasmas of an average ionization degree sequence of 10, for both spectrally resolved opacities and Rosseland and Planck means. For comparison, results obtained by using an average atom model are also given to show that even for a relatively higher density of matter, correlation effects are also important to predict the correct positions of absorption peaks of transition arrays.

Laboratory Needs for Interstellar Ice Studies

NASA Astrophysics Data System (ADS)

Boogert, Abraham C. A.

2012-05-01

A large fraction of the molecules in dense interstellar and circumstellar environments is stored in icy grain mantles. The mantles are formed by a complex interplay between chemical and physical processes. Key questions on the accretion and desorption processes and the chemistry on the grain surfaces and within the icy mantles can only be answered by laboratory experiments. Recent infrared (2-30 micron) spectroscopic surveys of large samples of Young Stellar Objects (YSOs) and background stars tracing quiescent cloud material have shown that the ice band profiles and depths vary considerably as a function of environment. Using laboratory spectra in the identification process, it is clear that a rather complex mixture of simple species (CH3OH, CO2, H2O, CO) exists even in the quiescent cloud phase. Variations of the local physical conditions (CO freeze out) and time scales (CH3OH formation) appear to be key factors in the observed variations. Sublimation and thermal processing dominate as YSOs heat their environments. The identification of several ice absorption features is still disputed. I will outline laboratory work (e.g., on salts, PAHs, and aliphatic hydrocarbons) needed to further constrain the ice band identification as well as the thermal and chemical history of the carriers. Such experiments will also be essential to interpret future high spectral resolution SOFIA and JWST observations.

OPTICAL HYDROGEN ABSORPTION CONSISTENT WITH A THIN BOW SHOCK LEADING THE HOT JUPITER HD 189733B

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cauley, P. Wilson; Redfield, Seth; Jensen, Adam G.

Bow shocks are ubiquitous astrophysical phenomena resulting from the supersonic passage of an object through a gas. Recently, pre-transit absorption in UV metal transitions of the hot Jupiter (HJ) exoplanets HD 189733b and WASP12-b have been interpreted as being caused by material compressed in a planetary bow shock. Here we present a robust detection of a time-resolved pre-transit, as well as in-transit absorption signature around the HJ exoplanet HD 189733b using high spectral resolution observations of several hydrogen Balmer lines. The line shape of the pre-transit feature and the shape of the timeseries absorption provide the strongest constraints on themore » morphology and physical characteristics of extended structures around an exoplanet. The in-transit measurements confirm the previous exospheric Hα detection, although the absorption depth measured here is ∼50% lower. The pre-transit absorption feature occurs 125 minutes before the predicted optical transit, a projected linear distance from the planet to the stellar disk of 7.2 R{sub p}. The absorption strength observed in the Balmer lines indicates an optically thick, but physically small, geometry. We model this signal as the early ingress of a planetary bow shock. If the bow shock is mediated by a planetary magnetosphere, the large standoff distance derived from the model suggests a large planetary magnetic field strength of B{sub eq} = 28 G. Better knowledge of exoplanet magnetic field strengths is crucial to understanding the role these fields play in planetary evolution and the potential development of life on planets in the habitable zone.« less

Light absorption properties of colored dissolved organic matter (CDOM) in adjacent waters of the Changjiang Estuary during a flood season: implication for DOC estimation

NASA Astrophysics Data System (ADS)

Liu, Yangyang; Shen, Fang; Li, Xiuzhen

2014-11-01

Light absorption properties of colored dissolved organic matter (CDOM) in adjacent waters of the Changjiang Estuary were investigated during the summer of 2013. CDOM absorption showed a substantial portion of the total absorption and clearly dominant among most investigation stations. It generally decreased from the northwest to the southeast, which controlled by physical mixing of fresh water and seawater as was indicated by a conservative behaviour of CDOM. CDOM absorption sharply increased during phytoplankton blooms. Similarly, dissolved organic carbon (DOC) also peaked during blooms period. However, DOC exhibited a more complex behavior relative to a simple conservative mixing, possibly attributed to multiple origins of DOC. CDOM absorption and DOC co-varied to some degree, implying a potential way of DOC estimation from CDOM absorption. However, more detailed information such as CDOM and DOC composition and more validation data were required to obtain a stable CDOM - DOC pattern. Lastly, empirical algorithms with limited data were developed to retrieve CDOM absorption. Further validation of the algorithms were needed when they were to be commonly applied.

Measurement of the sound absorption coefficient for an advanced undergraduate physics laboratory

NASA Astrophysics Data System (ADS)

Macho-Stadler, E.; Elejalde-García, M. J.

2017-09-01

We present a simple experiment that allows advanced undergraduates to learn the basics of the acoustic properties of materials. The impedance tube-standing wave method is applied to study the normal absorption coefficient of acoustics insulators. The setup includes a tube, a speaker, a microphone, a digital function generator and an oscilloscope, material available in an undergraduate laboratory. Results of the change of the absorption coefficient with the frequency, the sample thickness and the sample density are analysed and compared with those obtained with a commercial system.

Time-of-day–dependent global distribution of lunar surficial water/hydroxyl

PubMed Central

Wöhler, Christian; Grumpe, Arne; Berezhnoy, Alexey A.; Shevchenko, Vladislav V.

2017-01-01

A new set of time-of-day–dependent global maps of the lunar near-infrared water/hydroxyl (H2O/OH) absorption band strength near 2.8 to 3.0 μm constructed on the basis of Moon Mineralogy Mapper (M3) data is presented. The analyzed absorption band near 2.8 to 3.0 μm indicates the presence of surficial H2O/OH. To remove the thermal emission component from the M3 reflectance spectra, a reliable and physically realistic mapping method has been developed. Our maps show that lunar highlands at high latitudes show a stronger H2O/OH absorption band in the lunar morning and evening than at midday. The amplitude of these time-of-day–dependent variations decreases with decreasing latitude of the highland regions, where below about 30°, absorption strength becomes nearly constant during the lunar day at a similar level as in the high-latitude highlands at midday. The lunar maria exhibit weaker H2O/OH absorption than the highlands at all, but showing a smaller difference from highlands absorption levels in the morning and evening than at midday. The level around midday is generally higher for low-Ti than for high-Ti mare surfaces, where it reaches near-zero values. Our observations contrast with previous studies that indicate a significant concentration of surficial H2O/OH at high latitudes only. Furthermore, although our results generally support the commonly accepted mechanism of H2O/OH formation by adsorption of solar wind protons, they suggest the presence of a more strongly bounded surficial H2O/OH component in the lunar highlands and parts of the mare regions, which is not removed by processes such as diffusion/thermal evaporation and photolysis in the course of the lunar day. PMID:28913430

Energy absorption capability and crashworthiness of composite material structures: A review

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carruthers, J.J.; Kettle, A.P.; Robinson, A.M.

1998-10-01

The controlled brittle failure of thermosetting fiber-reinforced polymer composites can provide a very efficient energy absorption mechanism. Consequently, the use of these materials in crashworthy vehicle designs has been the subject of considerable interest. In this respect, their more widespread application has been limited by the complexity of their collapse behavior. This article reviews the current level of understanding i this field, including the correlations between failure mode and energy absorption, the principal material, geometric, and physical parameters relevant to crashworthy design and methods of predicting the energy absorption capability of polymer composites. Areas which require further investigation are identified.more » This review article contains 70 references.« less

The opacity of the universe and the strong equivalence principle

NASA Technical Reports Server (NTRS)

Canuto, V. M.; Goldman, I.

1983-01-01

A possible explanation of why the advanced solutions of Maxwell's equations are not observed in nature is by way of absorption by an opaque universe. As Davies has shown, the ever expanding, general relativistic cosmological models fail to provide the needed absorption. The absorption mechanism calling for an interplay between local physics and cosmology, is usually developed adopting the strong equivalence principle, SEP, which precludes such interplay. It is shown that complete absorption of electromagnetic radiation by ionized intergalactic plasma is obtained provided a violation of the SEP, of the order of the Hubble's constant, is allowed to occur. The same degree of violation was previously found to be compatible with a large body of observational data.

Absorption bleaching of squarylium dye J aggregates via a two-photon excitation process

NASA Astrophysics Data System (ADS)

Furuki, Makoto; Tian, Minquan; Sato, Yasuhiro; Pu, Lyong Sun; Tatsuura, Satoshi; Abe, Shuji

2001-08-01

Squarylium dye J aggregates exhibit ultrafast nonlinear optical response of absorption saturation at the resonant wavelength of 770 nm. We studied the two-photon excitation process of J aggregates. By fluorescence measurement, we found the two-photon absorption band at 1.3 μm, which was different from that of the dye solution at 1.2 μm. Absorption saturation at 770 nm via a two-photon excitation process was observed by two-photon resonant excitation at 1.3 μm and also by off-resonant excitation at 1.55 μm, suggesting the possibility of J aggregates for optical switching materials working at the wavelength used in optical communications.

Three-dimensional electrospun polycaprolactone (PCL)/alginate hybrid composite scaffolds.

PubMed

Kim, Min Seong; Kim, GeunHyung

2014-12-19

Micro/nanofibrous scaffolds have been used widely in biomedical applications because the micro/nano-scale fibres resemble natural extracellular matrix and the high surface-to-volume ratio encourages cellular activities (attachment and proliferation). However, poor mechanical properties, low controllability of various shapes and difficulties in obtaining controllable pore structure have been obstacles to their use in hard-tissue regeneration. To overcome these shortcomings, we suggest a new composite system, which uses a combination method of wet electrospinning, rapid prototyping and a physical punching process. Using the process, we obtained polycaprolactone (PCL)/alginate composite scaffolds, consisting of electrospun PCL/alginate fibres and micro-sized PCL struts, with mean pore sizes of 821 ± 55 μm. To show the feasibility of the scaffolds for hard-tissue regeneration, the scaffolds were assessed not only for physical properties, including hydrophilicity, water absorption, and tensile and compressive strength, but also in vitro cellular responses (cell viability and proliferation) and osteogenic differentiation (alkaline phosphatase (ALP) activity, and mineralisation) by culturing with pre-osteoblasts (MC3T3-E1 cells). With the reinforcing micro-sized PCL struts, the elastic modulus of the PCL/alginate scaffold was significantly improved versus a pure PCL scaffold. Additionally, due to the alginate component in the fibrous scaffold, they showed significantly enhanced hydrophilic behaviour, water absorption (∼8-fold) and significant biological activities (∼1.6-fold for cell viability at 7 days, ∼2.3-fold for ALP activity at 14 days and ∼6.4-fold for calcium mineralisation at 14 days) compared with those of a pure PCL fibrous scaffold. Copyright © 2014 Elsevier Ltd. All rights reserved.

Transient receptor potential (TRP) channels as drug targets for diseases of the digestive system.

PubMed

Holzer, Peter

2011-07-01

Approximately 20 of the 30 mammalian transient receptor potential (TRP) channel subunits are expressed by specific neurons and cells within the alimentary canal. They subserve important roles in taste, chemesthesis, mechanosensation, pain and hyperalgesia and contribute to the regulation of gastrointestinal motility, absorptive and secretory processes, blood flow, and mucosal homeostasis. In a cellular perspective, TRP channels operate either as primary detectors of chemical and physical stimuli, as secondary transducers of ionotropic or metabotropic receptors, or as ion transport channels. The polymodal sensory function of TRPA1, TRPM5, TRPM8, TRPP2, TRPV1, TRPV3 and TRPV4 enables the digestive system to survey its physical and chemical environment, which is relevant to all processes of digestion. TRPV5 and TRPV6 as well as TRPM6 and TRPM7 contribute to the absorption of Ca²⁺ and Mg²⁺, respectively. TRPM7 participates in intestinal pacemaker activity, and TRPC4 transduces muscarinic acetylcholine receptor activation to smooth muscle contraction. Changes in TRP channel expression or function are associated with a variety of diseases/disorders of the digestive system, notably gastro-esophageal reflux disease, inflammatory bowel disease, pain and hyperalgesia in heartburn, functional dyspepsia and irritable bowel syndrome, cholera, hypomagnesemia with secondary hypocalcemia, infantile hypertrophic pyloric stenosis, esophageal, gastrointestinal and pancreatic cancer, and polycystic liver disease. These implications identify TRP channels as promising drug targets for the management of a number of gastrointestinal pathologies. As a result, major efforts are put into the development of selective TRP channel agonists and antagonists and the assessment of their therapeutic potential. Copyright © 2011 Elsevier Inc. All rights reserved.

The Physical Constraints on a New LoBAL QSO at z = 4.82

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yi, Weimin; Bai, Jin-Ming; Green, Richard

Very few low-ionization broad absorption line (LoBAL) QSOs have been found at high redshifts, to date. One high-redshift LoBAL QSO, J0122+1216, was recently discovered by the Lijiang 2.4 m Telescope, with an initial redshift determination of 4.76. Aiming to investigate its physical properties, we carried out follow-up observations in the optical and near-IR spectroscopy. Near-IR spectra from UKIRT and P200 confirm that it is a LoBAL, with a new redshift determination of 4.82 ± 0.01 based on the Mg ii emission-line. The new Mg ii redshift determination reveals strong blueshifts and asymmetry of the high-ionization emission lines. We estimate amore » black hole mass of ∼2.3 × 10{sup 9} M {sub ⊙} and Eddington ratio of ∼1.0 according to the empirical Mg ii-based single-epoch relation and bolometric correction factor. It is possible that strong outflows are the result of an extreme quasar environment driven by the high Eddington ratio. A lower limit on the outflowing kinetic power (>0.9% L {sub Edd}) is derived from both emission and absorption lines, indicating that these outflows play a significant role in the feedback process that regulates the growth of its black hole, as well as host galaxy evolution.« less

Effects of Plant Oil Interesterified Triacylglycerols on Lipemia and Human Health

PubMed Central

Alfieri, Andreina; Vitucci, Daniela; Orrù, Stefania; Buono, Pasqualina; Mancini, Annamaria

2017-01-01

The position of the fatty acids (sn-1, sn-2 and sn-3) (stereospecific numbering (sn)) in triacylglycerol (TAG) molecules produces a characteristic stereospecificity that defines the physical properties of the fats and influences their absorption, metabolism and uptake into tissues. Fat interesterification is a process that implies a positional distribution of fatty acids (FAs) within the TAG molecules, generating new TAG species, without affecting the FA cis-trans natural balance. The interesterified (IE) fats, frequently used in the food industry comprise fats that are rich in long-chain saturated FAs, such as palmitic acid (16:0) and stearic acid (18:0). Within the interesterified fats, a critical role is played by FA occupying the sn-2 position; in fact, the presence of an unsaturated FA in this specific position influences early metabolic processing and postprandial clearance that in turn could induce atherogenesis and thrombogenesis events. Here, we provide an overview on the role of TAG structures and interesterified palmitic and stearic acid-rich fats on fasting and postprandial lipemia, focusing our attention on their physical properties and their effects on human health. PMID:29301208

Neutron coincidence measurements when nuclear parameters vary during the multiplication process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Ming-Shih; Teichmann, T.

1995-07-01

In a recent paper, a physical/mathematical model was developed for neutron coincidence counting, taking explicit account of neutron absorption and leakage, and using dual probability generating function to derive explicit formulae for the single and multiple count-rates in terms of the physical parameters of the system. The results of this modeling proved very successful in a number of cases in which the system parameters (neutron reaction cross-sections, detection probabilities, etc.) remained the same at the various stages of the process (i.e. from collision to collision). However, there are practical circumstances in which such system parameters change from collision to collision,more » and it is necessary to accommodate these, too, in a general theory, applicable to such situations. For instance, in the case of the neutron coincidence collar (NCC), the parameters for the initial, spontaneous fission neutrons, are not the same as those for the succeeding induced fission neutrons, and similar situations can be envisaged for certain other experimental configurations. This present document shows how the previous considerations can be elaborated to embrace these more general requirements.« less

Theoretical analysis of the sound absorption characteristics of periodically stiffened micro-perforated plates

NASA Astrophysics Data System (ADS)

Zhou, Hai-An; Wang, Xiao-Ming; Mei, Yu-Lin

2014-10-01

The vibro-acoustic responses and sound absorption characteristics of two kinds of periodically stiffened micro-perforated plates are analyzed theoretically. The connected periodical structures of the stiffened plates can be ribs or block-like structures. Based on fundamental acoustic formulas of the micro-perforated plate of Maa and Takahashi, semi-analytical models of the vibrating stiffened plates are developed in this paper. Approaches like the space harmonicmethod, Fourier transforms and finite elementmethod (FEM) are adopted to investigate both kinds of the stiffened plates. In the present work, the vibro-acoustic responses of micro-perforated stiffened plates in the wavenumber space are expressed as functions of plate displacement amplitudes. After approximate numerical solutions of the amplitudes, the vibration equations and sound absorption coefficients of the two kinds of stiffened plates in the physical space are then derived by employing the Fourier inverse transform. In numerical examples, the effects of some physical parameters, such as the perforation ratio, incident angles and periodical distances etc., on the sound absorption performance are examined. The proposed approaches are also validated by comparing the present results with solutions of Takahashi and previous studies of stiffened plates. Numerical results indicate that the flexural vibration of the plate has a significant effect on the sound absorption coefficient in the water but has little influence in the air.

The vibroacoustic response and sound absorption performance of multilayer, microperforated rib-stiffened plates

NASA Astrophysics Data System (ADS)

Zhou, Haian; Wang, Xiaoming; Wu, Huayong; Meng, Jianbing

2017-10-01

The vibroacoustic response and sound absorption performance of a structure composed of multilayer plates and one rigid back wall are theoretically analyzed. In this structure, all plates are two-dimensional, microperforated, and periodically rib-stiffened. To investigate such a structural system, semianalytical models of one-layer and multilayer plate structures considering the vibration effects are first developed. Then approaches of the space harmonic method and Fourier transforms are applied to a one-layer plate, and finally the cascade connection method is utilized for a multilayer plate structure. Based on fundamental acoustic formulas, the vibroacoustic responses of microperforated stiffened plates are expressed as functions of a series of harmonic amplitudes of plate displacement, which are then solved by employing the numerical truncation method. Applying the inverse Fourier transform, wave propagation, and linear addition properties, the equations of the sound pressures and absorption coefficients for the one-layer and multilayer stiffened plates in physical space are finally derived. Using numerical examples, the effects of the most important physical parameters—for example, the perforation ratio of the plate, sound incident angles, and periodical rib spacing—on sound absorption performance are examined. Numerical results indicate that the sound absorption performance of the studied structure is effectively enhanced by the flexural vibration of the plate in water. Finally, the proposed approaches are validated by comparing the results of stiffened plates of the present work with solutions from previous studies.

Transient-Absorption Spectroscopy of Cis-Trans Isomerization of N,N-dimethyl-4,4'-Azodianiline with 3D-Printed Temperature-Controlled Sample Holder

ERIC Educational Resources Information Center

Kosenkov, Dmytro; Shaw, James; Zuczek, Jennifer; Kholod, Yana

2016-01-01

The laboratory unit demonstrates a project based approach to teaching physical chemistry laboratory where upper-division undergraduates carry out a transient-absorption experiment investigating the kinetics of cis-trans isomerization of N,N-dimethyl-4,4'-azodianiline. Students participate in modification of a standard flash-photolysis spectrometer…

Laser Physics and Laser Techniques.

DTIC Science & Technology

1980-02-01

excited states is IGNFACTE produced in a pentacene -doped p-terphenyl molecular crystal by SIGNAL optical absorption from two crossed time-coincident...induces coherent microwave acoustic phonons. These in turn modulate, at the sound frequency, the optical absorption properties of the pentacene molecules... pentacene fects in molecular crystals, and particularly the observa- in p-terphenyl has thus been obtained [2]. tion of an acoustooptic amplitude

Laser Induced Fluorescence Spectroscopy of Neutral and Ionized Polycyclic Aromatic Hydrocarbons in a Cosmic Simulation Chamber

NASA Astrophysics Data System (ADS)

Bejaoui, Salma; Salama, Farid

2015-08-01

Polycyclic aromatic hydrocarbon (PAH) molecules are considered the best carriers to account for the ubiquitous infrared emission bands. PAHs have also been proposed as candidates to explain the diffuse interstellar bands (DIBs), a series of absorption features seen on the interstellar extinction curve and are plausible carriers for the extended red emission (ERE), a photoluminescent process associated with a wide variety of interstellar environments. Extensive efforts have been devoted over the past two decades to characterize the physical and chemical properties of PAH molecules and ions in space. Absorption spectra of PAH molecules and ions trapped in solid matrices have been compared to the DIBs [1, 2]. Absorption spectra of several cold, isolated gas-phase PAHs have also been measured under experimental conditions that mimic the interstellar conditions [see 3 for a review]. The purpose of this study is to provide a new dimension to the existing spectroscopic database of neutral and single ionized PAHs that is largely based on absorption spectra by adding emission spectroscopy data. The measurements are based on the laser-induced fluorescence (LIF) technique [4] and are performed with the Pulsed Discharge Nozzle (PDN) of the COSmIC laboratory facility at NASA Ames laboratory. The PDN generates plasma in a free supersonic jet expansion to simulate the physical and the chemical conditions in interstellar environments. We focus, here, on the fluorescence spectra of large neutral PAHs and their cations where there is a lack of fluorescence spectroscopy data. The astronomical implications of the data (e.g., ERE) are examinedReferences[1] F. Salama, E. Bakes, L.J. Allamandola, A.G.G.M. Tielens, Astrophys. J., 458 (1996) p.621[2] F. Salama, The ISO Revolution, EDP Sciences, Les Ulis, France (1999) p.65[3] Salama F., In Organic Matter in Space, IAU Symposium 251, Kwok & Sandford Eds.Cambridge University Press,4, S251,(2008), p. 357 (2008) and references therein.[4] Salma Bejaoui, Xavier Mercier, Pascale Desgroux, Eric Therssen, Comb.& Fl, 161 (2014) p. 2479

Controllable growth of vertically aligned graphene on C-face SiC

DOE PAGES

Liu, Yu; Chen, Lianlian; Hilliard, Donovan; ...

2016-10-06

We investigated how to control the growth of vertically aligned graphene on C-face SiC by varying the processing conditions. It is found that, the growth rate scales with the annealing temperature and the graphene height is proportional to the annealing time. Temperature gradient and crystalline quality of the SiC substrates influence their vaporization. The partial vapor pressure is crucial as it can interfere with further vaporization. A growth mechanism is proposed in terms of physical vapor transport. The monolayer character of vertically aligned graphene is verified by Raman and X-ray absorption spectroscopy. With the processed samples, d 0 magnetism ismore » realized and negative magnetoresistance is observed after Cu implantation. We also prove that multiple carriers exist in vertically aligned graphene.« less

Vibrational relaxation of hot carriers in C60 molecule

NASA Astrophysics Data System (ADS)

Madjet, Mohamed; Chakraborty, Himadri

2017-04-01

Electron-phonon coupling in molecular systems is at the heart of several important physical phenomena, including the mobility of carriers in organic electronic devices. Following the optical absorption, the vibrational relaxation of excited (hot) electrons and holes to the fullerene band-edges driven by electron-phonon coupling, known as the hot carrier thermalization process, is of particular fundamental interest. Using the non-adiabatic molecular dynamical methodology (PYXAID + Quantum Espresso) based on density functional approach, we have performed a simulation of vibrionic relaxations of hot carriers in C60. Time-dependent population decays and transfers in the femtosecond scale from various excited states to the states at the band-edge are calculated to study the details of this relaxation process. This work was supported by the U.S. National Science Foundation.

Facile method for the synthesis of gold nanoparticles using an ion coater

NASA Astrophysics Data System (ADS)

Lee, Seung Han; Jung, Hyun Kyu; Kim, Tae Cheol; Kim, Chang Hee; Shin, Chang Hwan; Yoon, Tae-Sik; Hong, A.-Ra; Jang, Ho Seong; Kim, Dong Hun

2018-03-01

Herein we report a metal nanoparticle synthesis method based on a physical vapor deposition process instead of the conventional wet process of chemical reactions in liquids. A narrow size distribution of synthesized gold nanoparticles was obtained using an ion coater on glycerin at low vapor pressure. The nanoparticle size could be modulated by controlling the sputtering conditions especially the discharge current. Due to the formation of gold nanoparticles, a surface plasmon resonance peak appeared at ∼530 nm in the absorption spectrum. The surface plasmon resonance peak exhibited red-shift with increasing size of the gold nanoparticles. Our results provide a simple, environmental friendly method for the synthesis of metal nanoparticles by combine low-cost deposition apparatus and a liquid medium, which is free from toxic reagents.

Controllable growth of vertically aligned graphene on C-face SiC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yu; Chen, Lianlian; Hilliard, Donovan

We investigated how to control the growth of vertically aligned graphene on C-face SiC by varying the processing conditions. It is found that, the growth rate scales with the annealing temperature and the graphene height is proportional to the annealing time. Temperature gradient and crystalline quality of the SiC substrates influence their vaporization. The partial vapor pressure is crucial as it can interfere with further vaporization. A growth mechanism is proposed in terms of physical vapor transport. The monolayer character of vertically aligned graphene is verified by Raman and X-ray absorption spectroscopy. With the processed samples, d 0 magnetism ismore » realized and negative magnetoresistance is observed after Cu implantation. We also prove that multiple carriers exist in vertically aligned graphene.« less

Towards high fidelity numerical wave tanks for modelling coastal and ocean engineering processes

NASA Astrophysics Data System (ADS)

Cozzuto, G.; Dimakopoulos, A.; de Lataillade, T.; Kees, C. E.

2017-12-01

With the increasing availability of computational resources, the engineering and research community is gradually moving towards using high fidelity Comutational Fluid Mechanics (CFD) models to perform numerical tests for improving the understanding of physical processes pertaining to wave propapagation and interaction with the coastal environment and morphology, either physical or man-made. It is therefore important to be able to reproduce in these models the conditions that drive these processes. So far, in CFD models the norm is to use regular (linear or nonlinear) waves for performing numerical tests, however, only random waves exist in nature. In this work, we will initially present the verification and validation of numerical wave tanks based on Proteus, an open-soruce computational toolkit based on finite element analysis, with respect to the generation, propagation and absorption of random sea states comprising of long non-repeating wave sequences. Statistical and spectral processing of results demonstrate that the methodologies employed (including relaxation zone methods and moving wave paddles) are capable of producing results of similar quality to the wave tanks used in laboratories (Figure 1). Subsequently cases studies of modelling complex process relevant to coastal defences and floating structures such as sliding and overturning of composite breakwaters, heave and roll response of floating caissons are presented. Figure 1: Wave spectra in the numerical wave tank (coloured symbols), compared against the JONSWAP distribution

Tunable ultranarrow spectrum selective absorption in a graphene monolayer at terahertz frequency

NASA Astrophysics Data System (ADS)

Wu, Jun

2016-06-01

Complete absorption in a graphene monolayer at terahertz frequency through the critical coupling effect is investigated. It is achieved by sandwiching the graphene monolayer between a dielectric grating and a Bragg grating. The designed graphene absorber exhibits near-unity absorption at resonance but with an ultranarrow spectrum and antenna-like response, which is attributed to the combined effects of guided mode resonance with dielectric grating and the photonic band gap with Bragg grating. In addition to numerical simulation, the electric field distributions are also illustrated to provide a physical understanding of the perfect absorption effect. Furthermore, the absorption performance can be tuned by only changing the Fermi level of graphene, which is beneficial for real application. It is believed that this study may be useful for designing next-generation graphene-based optoelectronic devices.

Metaporous layer to overcome the thickness constraint for broadband sound absorption

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Jieun; Lee, Joong Seok; Kim, Yoon Young, E-mail: yykim@snu.ac.kr

The sound absorption of a porous layer is affected by its thickness, especially in a low-frequency range. If a hard-backed porous layer contains periodical arrangements of rigid partitions that are coordinated parallel and perpendicular to the direction of incoming sound waves, the lower bound of the effective sound absorption can be lowered much more and the overall absorption performance enhanced. The consequence of rigid partitioning in a porous layer is to make the first thickness resonance mode in the layer appear at much lower frequencies compared to that in the original homogeneous porous layer with the same thickness. Moreover, appropriatemore » partitioning yields multiple thickness resonances with higher absorption peaks through impedance matching. The physics of the partitioned porous layer, or the metaporous layer, is theoretically investigated in this study.« less

Analysis of single-layer metamaterial absorber with reflection theory

NASA Astrophysics Data System (ADS)

Xiong, Han; Tang, Ming-Chun; Hong, Jing-Song

2015-04-01

A reflection theory is employed to analyze a single-layered metamaterial absorber. With the necessary conditions for zero reflection, the permittivity and permeability as functions of absorptivity were obtained, which are suitable for analyzing the absorption properties of single-layered metamaterial absorber at both normal and oblique incidence cases. With the obtained expressions, it not only can explain why the absorption peaks monotonously decrease with increasing of the incident angles but also can explore the relationship between the absorptivity and spacer thickness of the dielectric slab. A Jerusalem cross metamaterial absorber was simulated and verified the validity of this proposed reflection theory. The main contribution of our work is that it can explain the physical mechanism of the various absorption peaks by using the analytical formula and highlights its potential guidance for designing and analyzing metamaterial absorbers in the future.

Generalized Landauer equation: Absorption-controlled diffusion processes

NASA Astrophysics Data System (ADS)

Godoy, Salvador; García-Colín, L. S.; Micenmacher, Victor

1999-05-01

The exact expression of the one-dimensional Boltzmann multiple-scattering coefficients, for the passage of particles through a slab of a given material, is obtained in terms of the single-scattering cross section of the material, including absorption. The remarkable feature of the result is that for multiple scattering in a metal, free from absorption, one recovers the well-known Landauer result for conduction electrons. In the case of particles, such as neutrons, moving through a weak absorbing media, Landuer's formula is modified due to the absorption cross section. For photons, in a strong absorbing media, one recovers the Lambert-Beer equation. In this latter case one may therefore speak of absorption-controlled diffusive processes.

Study of absorption and re-emission processes in a ternary liquid scintillation system

NASA Astrophysics Data System (ADS)

Xiao, Hua-Lin; Li, Xiao-Bo; Zheng, Dong; Cao, Jun; Wen, Liang-Jian; Wang, Nai-Yan

2010-11-01

Liquid scintillators are widely used as the neutrino target in neutrino experiments. The absorption and emission of different components of a ternary liquid scintillator (Linear Alkyl Benzene (LAB) as the solvent, 2,5-diphenyloxazole (PPO) as the fluor and p-bis-(o-methylstyryl)-benzene (bis-MSB) as wavelength shifter) are studied. It is shown that the absorption of this liquid scintillator is dominant by LAB and PPO at wavelengths less than 349 nm, and the absorption by bis-MSB becomes prevalent at the wavelength larger than 349 nm. The fluorescence quantum yields, which are the key parameters to model the absorption and re-emission processes in large liquid scintillation detectors, are measured.

Excimer laser decontamination

NASA Astrophysics Data System (ADS)

Sentis, Marc L.; Delaporte, Philippe C.; Marine, Wladimir; Uteza, Olivier P.

2000-04-01

The application of excimer laser ablation process to the decontamination of radioactive surfaces is discussed. This technology is very attractive because it allows to efficiently remove the contaminated particles without secondary waste production. To demonstrate the capability of such technology to efficiently decontaminate large area, we studied and developed a prototype which include a XeCl laser, an optical fiber delivery system and an ablated particles collection cell. The main physical processes taking place during UV laser ablation will be explained. The influence of laser wavelength, pulse duration and absorption coefficient of material will be discussed. Special studies have been performed to understand the processes which limit the transmission of high average power excimer laser through optical fiber, and to determine the laser conditions to optimize the value of this transmission. An in-situ spectroscopic analysis of laser ablation plasma allows the real time control of the decontamination. The results obtained for painting or metallic oxides removal from stainless steel surfaces will be presented.

Stereolithographic processing of ceramics: Photon diffusion in colloidal dispersion

NASA Astrophysics Data System (ADS)

Garg, Rajeev

The technique of ceramic stereolithography (CSL) has been developed for fabricating near net shape ceramic objects. In stereolithography, the three-dimensional computer design file of the object is sliced into thin layers. Each layer is physically fabricated by photocuring the surface of a liquid photo-polymerizable resin bath by raster scanning an ultra-violet laser across the surface of the resin. In CSL, the liquid resin is a high concentration colloidal dispersion in a solution of ultraviolet curable polymers. The ceramic green body fabricated by ceramic stereolithography technique is subjected to the post processing steps of drying, binder burnout and sintering to form a dense ceramic object. An aqueous alumina dispersion in photocuring polymers with particle volume fraction greater than 0.5 was formulated for CSL process. Low molecular weight solution polymers were found to be best suited for formulating ceramic resins due to their inherently low viscosity and favorable interactions with the ceramic dispersant. A hydroxyapatite ceramic resin was also developed for the use in the CSL technique. A model is developed to describe the photocuring process in concentrated ceramic dispersion. The curing profile in ceramic dispersion is governed by multiple scattering from the ceramic particles and absorption by the photocuring polymers. Diffusion theory of light transport is used to model the multiple scattering and absorption phenomena. It is found that diffusive transport adequately describes the phenomena of laser pulse propagation in highly concentrated colloidal dispersions. A model was developed to describe the absorption in highly concentrated ceramic dispersion. Various complex-shaped monolithic alumina and hydroxyapatite objects were fabricated by CSL and shown to possess uniform microstructure. The mechanical properties and sintering behavior of the parts fabricated by CSL are shown to be comparable to those fabricated by other ceramic processing technique. An application of CSL has been established for fabricating orthopedic implants. Orthopedic implants and biomedical devices of defined micro and macro architecture with controlled pore sizes and porosity were fabricated by CSL. The bone implants were also fabricated form in vivo scan of the bone. The structures were implanted in rats to understand the biocompatibility of CSL fabricated parts.

Temperature dependence of the Urbach optical absorption edge: A theory of multiple phonon absorption and emission sidebands

NASA Astrophysics Data System (ADS)

Grein, C. H.; John, Sajeev

1989-01-01

The optical absorption coefficient for subgap electronic transitions in crystalline and disordered semiconductors is calculated by first-principles means with use of a variational principle based on the Feynman path-integral representation of the transition amplitude. This incorporates the synergetic interplay of static disorder and the nonadiabatic quantum dynamics of the coupled electron-phonon system. Over photon-energy ranges of experimental interest, this method predicts accurate linear exponential Urbach behavior of the absorption coefficient. At finite temperatures the nonlinear electron-phonon interaction gives rise to multiple phonon emission and absorption sidebands which accompany the optically induced electronic transition. These sidebands dominate the absorption in the Urbach regime and account for the temperature dependence of the Urbach slope and energy gap. The physical picture which emerges is that the phonons absorbed from the heat bath are then reemitted into a dynamical polaronlike potential well which localizes the electron. At zero temperature we recover the usual polaron theory. At high temperatures the calculated tail is qualitatively similar to that of a static Gaussian random potential. This leads to a linear relationship between the Urbach slope and the downshift of the extrapolated continuum band edge as well as a temperature-independent Urbach focus. At very low temperatures, deviations from these rules are predicted arising from the true quantum dynamics of the lattice. Excellent agreement is found with experimental data on c-Si, a-Si:H, a-As2Se3, and a-As2S3. Results are compared with a simple physical argument based on the most-probable-potential-well method.

Assessment of spectroscopic parameters of solvated Eu(dmh)3 phen organometallic complex in various basic and acidic solvents.

PubMed

Chitnis, Dipti; Kalyani, N Thejo; Dhoble, Sanjay

2018-05-31

We report on the comprehension of novel europium activated hybrid organic Eu(dmh) 3 phen (Eu: europium, dmh: 2,6-dimethyl-3,5-heptanedione, phen: 1,10 phenanthroline) organo-metallic complexes, synthesized at different pH values by the solution technique. Photo physical properties of these complexes in various basic and acidic solvents were probed by UV-vis optical absorption and photoluminescence (PL) spectra. Minute differences in optical absorption peaks with variable optical densities were encountered with the variation in solvent from basic (chloroform, toluene, tetrahydrofuran) to acidic (acetic acid) media, revealing bathochromic shift in the absorption peaks. The PL spectra of the complex in various acidic and basic organic solvents revealed the position of the emission peak at 613 nm irrespective of the changes in solvents whereas the excitation spectrum almost matched with that of the UV-vis absorption data. The optical density was found to be maximum for the complex with pH 7.0 whereas it gradually decreased when pH was lowered to 6.0 or raised to 8.0 at an interval of 0.5, demonstrating its pH sensitive nature. Several spectroscopic parameters related to probability of transition such as absorbance A(λ), Napierian absorption coefficient α(λ), molecular absorption cross-section σ(λ), radiative lifetime (τ 0 ) and oscillator strength (f) were calculated from UV-vis spectra. The relative intensity ratio (R-ratio), calculated from the emission spectra was found to be almost the same in all the organic solvents. The optical energy gap, calculated for the designed complexes were found to be well in accordance with the ideal acceptance value of energy gap of the emissive materials used for fabrication of red organic light-emitting diode (OLED). The relation between Stoke's shift and solvent polarity function was established by Lippert-Mataga plot. This remarkable independence of the electronic absorption spectra of Eu complexes on the nature of the solvent with unique emission wavelength furnishes its potential to serve as a red light emitter for solution processed OLEDs, display panels and solid-state lighting. Copyright © 2018 John Wiley & Sons, Ltd.

Physical and absorption properties of titanium nanoparticles incorporated into zinc magnesium phosphate glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ismail, S.F.; Sahar, M.R., E-mail: mrahim057@gmail.com; Ghoshal, S.K.

We report the influences of Titania (TiO{sub 2}) nanoparticles (NPs) on the physical and optical properties of melt quench synthesized zinc magnesium phosphate glasses. Five glass samples with composition (42 − x)P{sub 2}O{sub 5}–50ZnO–8MgO–xTiO{sub 2}, where x = 0, 1, 2, 3, 4 mol% are prepared and characterized. XRD pattern verified the amorphous nature of all samples. TEM images manifested the growth of Ti NPs of average size ≈ 5.78 nm. TiO{sub 2} NP concentration dependent variation in the physical properties including glass density, molar volume, molar refractivity, electronic polarizability and ionic packing density are determined. The values of glassmore » refractive indices, density and ionic packing density are increased with the increase of TiO{sub 2} NP contents. Conversely, the Urbach energy, direct and indirect optical band gap are found to decrease with the increase of TiO{sub 2} NP concentration. These glass compositions may be potential for various solid state devices including laser. - Highlights: • TiO{sub 2} NP embedded self-cleaning phosphate glass are synthesized for the first time. • Well dispersed and uniform sized TiO{sub 2} NPs are grown. • Absorption spectra revealed prominent peak in the UV region. • TiO{sub 2} NPs strongly influenced the physical and absorption features of synthesized glasses. • The effects of TiO{sub 2} NPs on the physical and optical properties of these glasses are determined.« less

Meso-Scale Wetting of Paper Towels

NASA Astrophysics Data System (ADS)

Abedsoltan, Hossein

In this study, a new experimental approach is proposed to investigate the absorption properties of some selected retail paper towels. The samples were selected from two important manufacturing processes, conventional wet pressing (CWP) considered value products, and through air drying (TAD) considered as high or premium products. The tested liquids were water, decane, dodecane, and tetradecane with the total volumes in micro-liter range. The method involves the point source injection of liquid with different volumetric flowrates, in the nano-liter per second range. The local site for injection was chosen arbitrarily on the sample surface. The absorption process was monitored and recorded as the liquid advances, with two distinct imaging system methods, infrared imaging and optical imaging. The microscopic images were analyzed to calculate the wetted regions during the absorption test, and the absorption diagrams were generated. These absorption diagrams were dissected to illustrate the absorption phenomenon, and the absorption properties of the samples. The local (regional) absorption rates were computed for Mardi Gras and Bounty Basic as the representative samples for CWP and TAD, respectively in order to be compared with the absorption capacity property of these two samples. Then, the absorption capacity property was chosen as an index factor to compare the absorption properties of all the tested paper towels.

Enhancement of Performance and Mechanism Studies of All-Solution Processed Small-Molecule based Solar Cells with an Inverted Structure.

PubMed

Long, Guankui; Wu, Bo; Yang, Xuan; Kan, Bin; Zhou, Ye-Cheng; Chen, Li-Chuan; Wan, Xiangjian; Zhang, Hao-Li; Sum, Tze Chien; Chen, Yongsheng

2015-09-30

Both solution-processed polymers and small molecule based solar cells have achieved PCEs over 9% with the conventional device structure. However, for the practical applications of photovoltaic technology, further enhancement of both device performance and stability are urgently required, particularly for the inverted structure devices, since this architecture will probably be most promising for the possible coming commercialization. In this work, we have fabricated both conventional and inverted structure devices using the same small molecular donor/acceptor materials and compared the performance of both device structures, and found that the inverted structure based device gave significantly improved performance, the highest PCE so far for inverted structure based device using small molecules as the donor. Furthermore, the inverted device shows a remarkable stability with almost no obvious degradation after three months. Systematic device physics and charge generation dynamics studies, including optical simulation, light-intensity-dependent current-voltage experiments, photocurrent density-effective voltage analyses, transient absorption measurements, and electrical simulations, indicate that the significantly enhanced performance using inverted device is ascribed to the increasing of Jsc compared to the conventional device, which in turn is mainly attributed to the increased absorption of photons in the active layers, rather than the reduced nongeminate recombination.

All-optical control of light on a graphene-on-silicon nitride chip using thermo-optic effect.

PubMed

Qiu, Ciyuan; Yang, Yuxing; Li, Chao; Wang, Yifang; Wu, Kan; Chen, Jianping

2017-12-06

All-optical signal processing avoids the conversion between optical signals and electronic signals and thus has the potential to achieve a power efficient photonic system. Micro-scale all-optical devices for light manipulation are the key components in the all-optical signal processing and have been built on the semiconductor platforms (e.g., silicon and III-V semiconductors). However, the two-photon absorption (TPA) effect and the free-carrier absorption (FCA) effect in these platforms deteriorate the power handling and limit the capability to realize complex functions. Instead, silicon nitride (Si 3 N 4 ) provides a possibility to realize all-optical large-scale integrated circuits due to its insulator nature without TPA and FCA. In this work, we investigate the physical dynamics of all-optical control on a graphene-on-Si 3 N 4 chip based on thermo-optic effect. In the experimental demonstration, a switching response time constant of 253.0 ns at a switching energy of ~50 nJ is obtained with a device dimension of 60 μm × 60 μm, corresponding to a figure of merit (FOM) of 3.0 nJ mm. Detailed coupled-mode theory based analysis on the thermo-optic effect of the device has been performed.

Formability and mechanical properties of porous titanium produced by a moldless process.

PubMed

Naito, Yoshihito; Bae, Jiyoung; Tomotake, Yoritoki; Hamada, Kenichi; Asaoka, Kenzo; Ichikawa, Tetsuo

2013-08-01

Tailor-made porous titanium implants show great promise in both orthopedic and dental applications. However, traditional powder metallurgical processes require a high-cost mold, making them economically unviable for producing unique devices. In this study, a mixture of titanium powder and an inlay wax binder was developed for moldless forming and sintering. The formability of the mixture, the dimensional changes after sintering, and the physical and mechanical properties of the sintered porous titanium were evaluated. A 90:10 wt % mixture of Ti powder and wax binder was created manually at 70°C. After debindering, the specimen was sintered in Ar at 1100°C without any mold for 1, 5, and 10 h. The shrinkage, porosity, absorption ratio, bending and compressive strength, and elastic modulus were measured. The bending strength (135-356 MPa), compression strength (178-1226 MPa), and elastic modulus (24-54 GPa) increased with sintering time; the shrinkage also increased, whereas the porosity (from 37.1 to 29.7%) and absorption ratio decreased. The high formability of the binder/metal powder mixture presents a clear advantage for fabricating tailor-made bone and hard tissue substitution units. Moreover, the sintered compacts showed high strength and an elastic modulus comparable to that of cortical bone. Copyright © 2013 Wiley Periodicals, Inc.

Photoacoustic measurements of photokinetics in single optically trapped aerosol droplets

NASA Astrophysics Data System (ADS)

Covert, Paul; Cremer, Johannes; Signorell, Ruth; Thaler, Klemens; Haisch, Christoph

2017-04-01

It is well established that interaction of light with atmospheric aerosols has a large impact on the Earth's climate. However, uncertainties in the magnitude of this impact remain large, due in part to broad distributions of aerosol size, composition, and chemical reactivity. In this context, photoacoustic spectroscopy is commonly used to measure light absorption by aerosols. Here, we present photoacoustic measurements of single, optically-trapped nanodroplets to reveal droplet size-depencies of photochemical and physical processes. Theoretical considerations have pointed to a size-dependence in the magnitude and phase of the photoacoustic response from aerosol droplets. This dependence is thought to originate from heat transfer processes that are slow compared to the acoustic excitation frequency. In the case of a model aerosol, our measurements of single particle absorption cross-section versus droplet size confirm these theoretical predictions. In a related study, using the same model aerosol, we also demonstrate a droplet size-dependence of photochemical reaction rates [1]. Within sub-micron sized particles, photolysis rates were observed to be an order of magnitude greater than those observed in larger droplets. [1] J. W. Cremer, K. M. Thaler, C. Haisch, and R. Signorell. Photoacoustics of single laser-trapped nanodroplets for the direct observation of nanofocusing in aerosol photokinetics. Nat. Commun., 7:10941, 2016.

Operating Mechanisms of Mesoscopic Perovskite Solar Cells through Impedance Spectroscopy and J-V Modeling.

PubMed

Zarazúa, Isaac; Sidhik, Siraj; Lopéz-Luke, Tzarara; Esparza, Diego; De la Rosa, Elder; Reyes-Gomez, Juan; Mora-Seró, Iván; Garcia-Belmonte, Germà

2017-12-21

The performance of perovskite solar cell (PSC) is highly sensitive to deposition conditions, the substrate, humidity, and the efficiency of solvent extraction. However, the physical mechanism involved in the observed changes of efficiency with different deposition conditions has not been elucidated yet. In this work, PSCs were fabricated by the antisolvent deposition (AD) and recently proposed air-extraction antisolvent (AAD) process. Impedance analysis and J-V curve fitting were used to analyze the photogeneration, charge transportation, recombination, and leakage properties of PSCs. It can be elucidated that the improvement in morphology of perovskite film promoted by AAD method leads to increase in light absorption, reduction in recombination sites, and interstitial defects, thus enhancing the short-circuit current density, open-circuit voltage, and fill factor. This study will open up doors for further improvement of device and help in understanding its physical mechanism and its relation to the deposition methods.

3D Microperiodic Hydrogel Scaffolds for Robust Neuronal Cultures

PubMed Central

Hanson Shepherd, Jennifer N.; Parker, Sara T.; Shepherd, Robert F.; Gillette, Martha U.; Lewis, Jennifer A.; Nuzzo, Ralph G.

2011-01-01

Three-dimensional (3D) microperiodic scaffolds of poly(2-hydroxyethyl methacrylate) (pHEMA) have been fabricated by direct-write assembly of a photopolymerizable hydrogel ink. The ink is initially composed of physically entangled pHEMA chains dissolved in a solution of HEMA monomer, comonomer, photoinitiator and water. Upon printing 3D scaffolds of varying architecture, the ink filaments are exposed to UV light, where they are transformed into an interpenetrating hydrogel network of chemically cross-linked and physically entangled pHEMA chains. These 3D microperiodic scaffolds are rendered growth compliant for primary rat hippocampal neurons by absorption of polylysine. Neuronal cells thrive on these scaffolds, forming differentiated, intricately branched networks. Confocal laser scanning microscopy reveals that both cell distribution and extent of neuronal process alignment depend upon scaffold architecture. This work provides an important step forward in the creation of suitable platforms for in vitro study of sensitive cell types. PMID:21709750

Physical aging and its influence on the reliability of network epoxies and epoxy-matrix composites

NASA Technical Reports Server (NTRS)

Heinemann, K.

1983-01-01

The matrix-dominated physical and mechanical properties of a carbon fiber reinforced epoxy composite and a neat epoxy resin were found to be affected by sub-Tg annealing in nitrogen and dark atmosphere. Postcured specimens of Thornel 300 carbon-fiber/Fiberite 934 epoxy as well as Fiberite 934 epoxy resin were quenched from above Tg and given annealing at 140 C, 110 C, or 80 C, for time up to one-hundred thousand minutes. No weight loss was observed during annealing at these temperatures. Significant variations were found in density, modulus, hardness, damping, moisture absorption ability, thermal expansivity. Moisture-epoxy interactious were also studied. The kinetics of aging as well as the molecular aggregation during this densification process were monitored by differential scanning calorimetry, dynamic mechanical analysis, density gradient column, microhardness tester, Instron, and solid-state nuclear magnetic resonance spectroscopy.

Training and business performance: the mediating role of absorptive capacities.

PubMed

Hernández-Perlines, Felipe; Moreno-García, Juan; Yáñez-Araque, Benito

2016-01-01

Training has been the focus of considerable conceptual and empirical attention but is considered a relevant factor for competitive edge in companies because it has a positive impact on business performance. This study is justified by the need for deeper analysis of the process involving the transfer of training into performance. This paper's originality lies in the implementation of the absorptive capacities approach as an appropriate conceptual framework for designing a model that reflects the connection between training and business performance through absorptive capacities. Based on the above conceptual framework and using the dual methodological implementation, a new method of analyzing the relationship between training and performance was obtained: efforts in training will not lead to performance without the mediation of absorptive. Training turns into performance if absorptive capacities are involved in this process. The suggested model becomes an appropriate framework for explaining the process of transformation of training into organizational performance, in which absorptive capacities play a key role. The findings obtained can go further owing to fs/QCA: of the different absorptive capacities, that of exploitation is a necessary condition to achieve better organizational performance. Therefore, training based on absorptive capacity will guide and facilitate the design of appropriate human resource strategies so that training results in improved performance. This conclusion is relevant for the development of a new facet of absorptive capacities by relating it to training and resulting in first-level implications for human resource management.

Light absorption and excitation energy transfer calculations in primitive photosynthetic bacteria

NASA Astrophysics Data System (ADS)

Komatsu, Yu; Kayanuma, Megumi; Shoji, Mitsuo; Yabana, Kazuhiro; Shiraishi, Kenji; Umemura, Masayuki

2015-06-01

In photosynthetic organisms, light energy is converted into chemical energy through the light absorption and excitation energy transfer (EET) processes. These processes start in light-harvesting complexes, which contain special photosynthetic pigments. The exploration of unique mechanisms in light-harvesting complexes is directly related to studies, such as artificial photosynthesis or biosignatures in astrobiology. We examined, through ab initio calculations, the light absorption and EET processes using cluster models of light-harvesting complexes in purple bacteria (LH2). We evaluated absorption spectra and energy transfer rates using the LH2 monomer and dimer models to reproduce experimental results. After the calibration tests, a LH2 aggregation model, composed of 7 or 19 LH2s aligned in triangle lattice, was examined. We found that the light absorption is red shifted and the energy transfer becomes faster as the system size increases. We also found that EET is accelerated by exchanging the central pigments to lower energy excited pigments. As an astrobiological application, we calculated light absorptions efficiencies of the LH2 in different photoenvironments.

Optical absorption in recycled waste plastic polyethylene

NASA Astrophysics Data System (ADS)

Aji, M. P.; Rahmawati, I.; Priyanto, A.; Karunawan, J.; Wati, A. L.; Aryani, N. P.; Susanto; Wibowo, E.; Sulhadi

2018-03-01

We investigated the optical properties of UV spectrum absorption in recycled waste plastic from polyethylene polymer type. Waste plastic polyethylene showed an optical spectrum absorption after it’s recycling process. Spectrum absorption is determined using spectrophotometer UV-Nir Ocean Optics type USB 4000. Recycling method has been processed using heating treatment around the melting point temperature of the polyethylene polymer that are 200°C, 220°C, 240°C, 260°C, and 280°C. In addition, the recycling process was carried out with time variations as well, which are 1h, 1.5h, 2h, and 2.5h. The result of this experiment shows that recycled waste plastic polyethylene has a spectrum absorption in the ∼ 340-550 nm wavelength range. The absorbance spectrum obtained from UV light which is absorbed in the orbital n → π* and the orbital π → π*. This process indicates the existence of electron transition phenomena. This mechanism is affected by the temperature and the heating time where the intensity of absorption increases and widens with the increase of temperature and heating time. Furthermore this study resulted that the higher temperature affected the enhancement of the band gap energy of waste plastic polyethylene. These results show that recycled waste plastic polyethylene has a huge potential to be absorber materials for solar cell.

Responses of epidermal cell turgor pressure and photosynthetic activity of leaves of the atmospheric epiphyte Tillandsia usneoides (Bromeliaceae) after exposure to high humidity.

PubMed

Martin, Craig E; Rux, Guido; Herppich, Werner B

2013-01-01

It has been well-established that many epiphytic bromeliads of the atmospheric-type morphology, i.e., with leaf surfaces completely covered by large, overlapping, multicellular trichomes, are capable of absorbing water vapor from the atmosphere when air humidity increases. It is much less clear, however, whether this absorption of water vapor can hydrate the living cells of the leaves and, as a consequence, enhance physiological processes in such cells. The goal of this research was to determine if the absorption of atmospheric water vapor by the atmospheric epiphyte Tillandsia usneoides results in an increase in turgor pressure in leaf epidermal cells that subtend the large trichomes, and, by using chlorophyll fluorescence techniques, to determine if the absorption of atmospheric water vapor by leaves of this epiphyte results in increased photosynthetic activity. Results of measurements on living cells of attached leaves of this epiphytic bromeliad, using a pressure probe and of whole-shoot fluorescence imaging analyses clearly illustrated that the turgor pressure of leaf epidermal cells did not increase, and the photosynthetic activity of leaves did not increase, following exposure of the leaves to high humidity air. These results experimentally demonstrate, for the first time, that the absorption of water vapor following increases in atmospheric humidity in atmospheric epiphytic bromeliads is mostly likely a physical phenomenon resulting from hydration of non-living leaf structures, e.g., trichomes, and has no physiological significance for the plant's living tissues. Copyright © 2012 Elsevier GmbH. All rights reserved.

A clumpy and anisotropic galaxy halo at redshift 1 from gravitational-arc tomography.

PubMed

Lopez, Sebastian; Tejos, Nicolas; Ledoux, Cédric; Barrientos, L Felipe; Sharon, Keren; Rigby, Jane R; Gladders, Michael D; Bayliss, Matthew B; Pessa, Ismael

2018-02-22

Every star-forming galaxy has a halo of metal-enriched gas that extends out to at least 100 kiloparsecs, as revealed by the absorption lines that this gas imprints on the spectra of background quasars. However, quasars are sparse and typically probe only one narrow beam of emission through the intervening galaxy. Close quasar pairs and gravitationally lensed quasars have been used to circumvent this inherently one-dimensional technique, but these objects are rare and the structure of the circumgalactic medium remains poorly constrained. As a result, our understanding of the physical processes that drive the recycling of baryons across the lifetime of a galaxy is limited. Here we report integral-field (tomographic) spectroscopy of an extended background source-a bright, giant gravitational arc. We can thus coherently map the spatial and kinematic distribution of Mg ɪɪ absorption-a standard tracer of enriched gas-in an intervening galaxy system at redshift 0.98 (around 8 billion years ago). Our gravitational-arc tomography unveils a clumpy medium in which the absorption strength decreases with increasing distance from the galaxy system, in good agreement with results for quasars. Furthermore, we find strong evidence that the gas is not distributed isotropically. Interestingly, we detect little kinematic variation over a projected area of approximately 600 square kiloparsecs, with all line-of-sight velocities confined to within a few tens of kilometres per second of each other. These results suggest that the detected absorption originates from entrained recycled material, rather than in a galactic outflow.

Response surface method for modeling the removal of carbon dioxide from a simulated gas using water absorption enhanced with a liquid-film-forming device.

PubMed

Nguyen, Diem-Mai Kim; Imai, Tsuyoshi; Dang, Thanh-Loc Thi; Kanno, Ariyo; Higuchi, Takaya; Yamamoto, Koichi; Sekine, Masahiko

2018-03-01

This paper presents the results from using a physical absorption process to absorb gaseous CO 2 mixed with N 2 using water by producing tiny bubbles via a liquid-film-forming device (LFFD) that improves the solubility of CO 2 in water. The influence of various parameters-pressure, initial CO 2 concentration, gas-to-liquid ratios, and temperature-on the CO 2 removal efficiency and its absorption rate in water were investigated and estimated thoroughly by statistical polynomial models obtained by the utilization of the response surface method (RSM) with a central composite design (CCD). Based on the analysis, a high efficiency of CO 2 capture can be reached in conditions such as low pressure, high CO 2 concentration at the inlet, low gas/liquid ratio, and low temperature. For instance, the highest removal efficiency in the RSM-CCD experimental matrix of nearly 80% occurred for run number 20, which was conducted at 0.30MPa, CO 2 concentration of 35%, gas/liquid ratio of 0.71, and temperature of 15°C. Furthermore, the coefficients of determination, R 2 , were 0.996 for the removal rate and 0.982 for the absorption rate, implying that the predicted values computed by the constructed models correlate strongly and fit well with the experimental values. The results obtained provide essential information for implementing this method properly and effectively and contribute a promising approach to the problem of CO 2 capture in air pollution treatment. Copyright © 2017. Published by Elsevier B.V.

Third order nonlinear optical response exhibited by mono- and few-layers of WS 2

DOE PAGES

Torres-Torres, Carlos; Perea-López, Néstor; Elías, Ana Laura; ...

2016-04-13

In this work, strong third order nonlinear optical properties exhibited by WS 2 layers are presented. Optical Kerr effect was identified as the dominant physical mechanism responsible for these third order optical nonlinearities. An extraordinary nonlinear refractive index together with an important contribution of a saturated absorptive response was observed to depend on the atomic layer stacking. Comparative experiments performed in mono- and few-layer samples of WS 2 revealed that this material is potentially capable of modulating nonlinear optical processes by selective near resonant induced birefringence. In conclusion, we envision applications for developing all-optical bidimensional nonlinear optical devices.

Penetration of Solar Radiation into Solid Carbon Dioxide

NASA Astrophysics Data System (ADS)

Chinnery, H. E.; Hagermann, A.; Kaufmann, E.; Lewis, S. R.; Grady, M. M.

2017-09-01

Carbon dioxide ice exists naturally on the surface of Mars. This is a unique environment, with no Earth analogues, and so determining the properties of such a surface is important to further our understanding of the Martian environment. Laboratory experiments have determined the e-folding scale, or absorption scale length, for carbon dioxide slab ice, granular ice and snow. This is a universal measure of how transparent a material is to visible light, and so has implications for the radiative budget of carbon dioxide ice covered surfaces, as well as physical processes, such as the so-called spider formations in the cryptic region near the Martian south pole.

Imaging at an x-ray absorption edge using free electron laser pulses for interface dynamics in high energy density systems [Resonant phase contrast imaging for interface physics

DOE PAGES

Beckwith, M. A.; Jiang, S.; Schropp, A.; ...

2017-05-01

Tuning the energy of an x-ray probe to an absorption line or edge can provide material-specific measurements that are particularly useful for interfaces. Simulated hard x-ray images above the Fe K-edge are presented to examine ion diffusion across an interface between Fe 2O 3 and SiO 2 aerogel foam materials. The simulations demonstrate the feasibility of such a technique for measurements of density scale lengths near the interface with submicron spatial resolution. A proof-of-principle experiment is designed and performed at the Linac coherent light source facility. Preliminary data show the change of the interface after shock compression and heating withmore » simultaneous fluorescence spectra for temperature determination. Here, the results provide the first demonstration of using x-ray imaging at an absorption edge as a diagnostic to detect ultrafast phenomena for interface physics in high-energy-density systems.« less

Determination of Pb in Biological Samples by Graphite Furnace Atomic Absorption Spectrophotometry: An Exercise in Common Interferences and Fundamental Practices in Trace Element Determination

ERIC Educational Resources Information Center

Spudich, Thomas M.; Herrmann, Jennifer K.; Fietkau, Ronald; Edwards, Grant A.

2004-01-01

An experiment is conducted to ascertain trace-level Pb in samples of bovine liver or muscle by applying graphite furnace atomic absorption spectrophotometry (GFAAS). The primary objective is to display the effects of physical and spectral intrusions in determining trace elements, and project the usual methods employed to minimize accuracy errors…

USSR Report, Physics and Mathematics.

DTIC Science & Technology

1987-03-12

reveal that the threshold of explosive absorption depends on both the laser beam diameter and the laser pulse duration. Estimates indicate the possi...Phenomena in Parametric Generators and Amplifiers of Ultrashort Light Pulses (A. Piskarkas, A. Stabinis, et al.; USPEKHI FIZICHESKIKH NAUK, No 1, Sep...Resolution of Picosecond Absorption Spectrometer by Selection of Length of Laser Light Pulses (B. N. Korvatovskiy, V. V. Gorokhov, et al.; KVANTOVAYA

Absorption of Solar Radiation by Clouds: An Overview

NASA Technical Reports Server (NTRS)

Tsay, Si-Chee; Einaudi, Franco (Technical Monitor)

2000-01-01

This talk provides an overview of the subject of absorption of solar radiation by clouds in the earth's atmosphere. The paper summarizes the available evidence which points to disagreements between theoretical and observed values of cloud absorption (and reflections). The importance of these discrepancies, particularly to remote sensing of clouds as well as to studies of cloud physics and earth radiation budgets, is emphasized. Existing cloud absorption and reflection measurements are reviewed and the persistent differences that exist between calculated and measured near-infrared cloud albedos are highlighted. Various explanations for these reflection and absorption discrepancies are discussed under two separate paths: a theoretician's approach and an experimentalist's approach. Examples for the former approach include model accuracy tests, large-droplet hypothesis, excess absorbing aerosol, enhanced water vapor continuum absorption, and effects of cloud inhomogeneity. The latter approach focuses on discussions of instrumental device, calibration, operational strategy, and signal/noise separation. A recommendation for future activities on this subject will be given.

Ultrathin Six-Band Polarization-Insensitive Perfect Metamaterial Absorber Based on a Cross-Cave Patch Resonator for Terahertz Waves

PubMed Central

Cheng, Yong Zhi; Huang, Mu Lin; Chen, Hao Ran; Guo, Zhen Zhong; Mao, Xue Song; Gong, Rong Zhou

2017-01-01

A simple design of an ultrathin six-band polarization-insensitive terahertz perfect metamaterial absorber (PMMA), composed of a metal cross-cave patch resonator (CCPR) placed over a ground plane, was proposed and investigated numerically. The numerical simulation results demonstrate that the average absorption peaks are up to 95% at six resonance frequencies. Owing to the ultra-narrow band resonance absorption of the structure, the designed PMMA also exhibits a higher Q factor (>65). In addition, the absorption properties can be kept stable for both normal incident transverse magnetic (TM) and transverse electric (TE) waves. The physical mechanism behind the observed high-level absorption is illustrated by the electric and power loss density distributions. The perfect absorption originates mainly from the higher-order multipolar plasmon resonance of the structure, which differs sharply from most previous studies of PMMAs. Furthermore, the resonance absorption properties of the PMMA can be modified and adjusted easily by varying the geometric parameters of the unit cell. PMID:28772951

Improving Optical Absorption Models for Harsh Planetary Atmospheres: Laboratory Spectroscopy at Venus Surface Conditions

NASA Astrophysics Data System (ADS)

Cole, Ryan Kenneth; Schroeder, Paul James; Diego Draper, Anthony; Rieker, Gregory Brian

2018-06-01

Modelling absorption spectra in high pressure, high temperature environments is complicated by the increased relevance of higher order collisional phenomena (e.g. line mixing, collision-induced absorption, finite duration of collisions) that alter the spectral lineshape. Accurate reference spectroscopy in these conditions is of interest for mineralogy and radiative transfer studies of Venus as well as other dense planetary atmospheres. We present a new, high pressure, high temperature absorption spectroscopy facility at the University of Colorado Boulder. This facility employs a dual frequency comb absorption spectrometer to record broadband (500nm), high resolution (~0.002nm) spectra in conditions comparable to the Venus surface (730K, 90bar). Measurements of the near-infrared spectrum of carbon dioxide at high pressure and temperature will be compared to modeled spectra extrapolated from the HITRAN 2016 database as well as other published models that include additional collisional physics. This comparison gives insight into the effectiveness of existing absorption databases for modeling the lower Venus atmosphere as well as the need to expand absorption models to suit these conditions.

Electronic absorption spectroscopy of matrix-isolated polycyclic aromatic hydrocarbon cations. I - The naphthalene cation (C10H8/+/)

NASA Technical Reports Server (NTRS)

Salama, F.; Allamandola, L. J.

1991-01-01

The ultraviolet, visible, and near-infrared absorption spectra of naphthalene (C10H8) and its radical ion (C10H8/+/), formed by vacuum ultraviolet irradiation, were measured in argon and neon matrices at 4.2 K. The associated vibronic band systems and their spectroscopic assignments are discussed together with the physical and chemical conditions governing ion production in the solid phase. The absorption coefficients were calculated for the ion and found lower than previous values, presumably due to the low polarizability of the neon matrix.

A survey of interstellar neutral potassium. I - Abundances and physical conditions in clouds toward 188 early-type stars

NASA Technical Reports Server (NTRS)

Chaffee, F. H., Jr.; White, R. E.

1982-01-01

Observations of interstellar absorption in the resonance doublet 7664, 7698 A of neutral potassium toward 188 early-type stars at a spectral resolution of 8 km/s are reported. The 7664 A line is successfully separated from nearly coincident telluric O2 absorption for all but a few of the 165 stars for which K I absorption is detected, making possible an abundance analysis by the doublet ratio method. The relationships between the potassium abundances and other atomic abundances, the abundance of molecular hydrogen, and interstellar reddening are investigated.

New Parameterization of Neutron Absorption Cross Sections

NASA Technical Reports Server (NTRS)

Tripathi, Ram K.; Wilson, John W.; Cucinotta, Francis A.

1997-01-01

Recent parameterization of absorption cross sections for any system of charged ion collisions, including proton-nucleus collisions, is extended for neutron-nucleus collisions valid from approx. 1 MeV to a few GeV, thus providing a comprehensive picture of absorption cross sections for any system of collision pairs (charged or uncharged). The parameters are associated with the physics of the problem. At lower energies, optical potential at the surface is important, and the Pauli operator plays an increasingly important role at intermediate energies. The agreement between the calculated and experimental data is better than earlier published results.

Secondary and primary relaxations in hyperbranched polyglycerol: a comparative study in the frequency and time domains.

PubMed

Garcia-Bernabé, Abel; Dominguez-Espinosa, Gustavo; Diaz-Calleja, Ricardo; Riande, Evaristo; Haag, Rainer

2007-09-28

The non-Debye relaxation behavior of hyperbranched polyglycerol was investigated by broadband dielectric spectroscopy. A thorough study of the relaxations was carried out paying special attention to truncation effects on deconvolutions of overlapping processes. Hyperbranched polyglycerol exhibits two relaxations in the glassy state named in increasing order of frequency beta and gamma processes. The study of the evolution of these two fast processes with temperature in the time retardation spectra shows that the beta absorption is swallowed by the alpha in the glass-liquid transition, the gamma absorption being the only relaxation that remains operative in the liquid state. In heating, a temperature is reached at which the alpha absorption vanishes appearing the alphagamma relaxation. Two characteristics of alpha absorptions, decrease of the dielectric strength with increasing temperature and rather high activation energy, are displayed by the alphagamma process. Williams' ansatz seems to hold for these topologically complex macromolecules.

Low-Energy Water Recovery from Subsurface Brines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Young Chul; Kim, Gyu Dong; Hendren, Zachary

A novel non-aqueous phase solvent (NAS) desalination process was proposed and developed in this research project. The NAS desalination process uses less energy than thermal processes, doesn’t require any additional chemicals for precipitation, and can be utilized to treat high TDS brine. In this project, our experimental work determined that water solubility changes and selective absorption are the key characteristics of NAS technology for successful desalination. Three NAS desalination mechanisms were investigated: (1) CO2 switchable, (2) high-temp absorption to low-temp desorption (thermally switchable), and (3) low-temp absorption to high-temp desorption (thermally switchable). Among these mechanisms, thermally switchable (low-temp absorption tomore » high-temp desorption) showed the highest water recovery and relatively high salt rejection. A test procedure for semi-continuous, bench scale NAS desalination process was also developed and used to assess performance under a range of conditions.« less

Absorption-emission optrode and methods of use thereof

DOEpatents

Hirschfeld, T.B.

1990-05-29

A method and apparatus are described for monitoring the physical and chemical properties of a sample fluid by measuring an optical signal generated by a fluorescent substance and modulated by an absorber substance. The emission band of the fluorescent substance overlaps the absorption band of the absorber substance, and the degree of overlap is dependent on the physical and chemical properties of the sample fluid. The fluorescent substance and absorber substance are immobilized on a substrate so that an effective number of molecules thereof are sufficiently close for resonant energy transfer to occur, thereby providing highly efficient modulation of the fluorescent emissions of the fluorescent substance by the absorber substance. 4 figs.

Fabrication of absorption gratings with X-ray lithography for X-ray phase contrast imaging

NASA Astrophysics Data System (ADS)

Wang, Bo; Wang, Yu-Ting; Yi, Fu-Ting; Zhang, Tian-Chong; Liu, Jing; Zhou, Yue

2018-05-01

Grating-based X-ray phase contrast imaging is promising especially in the medical area. Two or three gratings are involved in grating-based X-ray phase contrast imaging in which the absorption grating of high-aspect-ratio is the most important device and the fabrication process is a great challenge. The material with large atomic number Z is used to fabricate the absorption grating for excellent absorption of X-ray, and Au is usually used. The fabrication process, which involves X-ray lithography, development and gold electroplating, is described in this paper. The absorption gratings with 4 μm period and about 100 μm height are fabricated and the high-aspect-ratio is 50.

Phonon-Assisted Optical Absorption in Silicon from First Principles

NASA Astrophysics Data System (ADS)

Noffsinger, Jesse; Kioupakis, Emmanouil; Van de Walle, Chris G.; Louie, Steven G.; Cohen, Marvin L.

2012-04-01

The phonon-assisted interband optical absorption spectrum of silicon is calculated at the quasiparticle level entirely from first principles. We make use of the Wannier interpolation formalism to determine the quasiparticle energies, as well as the optical transition and electron-phonon coupling matrix elements, on fine grids in the Brillouin zone. The calculated spectrum near the onset of indirect absorption is in very good agreement with experimental measurements for a range of temperatures. Moreover, our method can accurately determine the optical absorption spectrum of silicon in the visible range, an important process for optoelectronic and photovoltaic applications that cannot be addressed with simple models. The computational formalism is quite general and can be used to understand the phonon-assisted absorption processes in general.

Polarization-independent absorption enhancement in a graphene square array with a cascaded grating structure.

PubMed

Wu, Jun

2018-03-01

The polarization-independent enhanced absorption effect of graphene in the near-infrared range is investigated. This is achieved by placing a graphene square array on top of a dielectric square array backed by a two-dimensional multilayer grating. Total optical absorption in graphene can be attributed to critical coupling, which is achieved through the combined effect of guided-mode resonance with the dielectric square array and the photonic band gap with the two-dimensional multilayer grating. To reveal the physical origin of such a phenomenon, the electromagnetic field distributions for both polarizations are illustrated. The designed graphene absorber exhibits near-unity polarization-independent absorption at resonance with an ultra-narrow spectrum. Moreover, the polarization-independent absorption can be tuned simply by changing the geometric parameters. The results may have promising potential for the design of graphene-based optoelectronic devices.

Reactor physics phenomena in additively manufactured control elements for the High Flux Isotope Reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burns, Joseph R.; Petrovic, Bojan; Chandler, David

Additive manufacturing is under investigation as a novel method of fabricating the control elements (CEs) of the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory with greater simplicity, eliminating numerous highly complex fabrication steps and thereby offering potential for significant savings in cost, time, and effort. This process yields a unique CE design with lumped absorbers, a departure from traditionally manufactured CEs with uniformly distributed absorbing material. Here, this study undertakes a neutronics analysis of the impact of additively manufactured CEs on the HFIR core physics, seeking preliminary assessment of the feasibility of their practical use. The resultsmore » of the MCNP transport simulations reveal changes in the HFIR reactor physics arising from geometric and nuclear effects. Absorber lumping in the discrete CEs yields a large volume of unpoisoned material that is not present in the homogeneous design, in turn yielding increases in free thermal flux in the CE absorbing regions and their immediate vicinity. The availability of additional free thermal neutrons in the core yields an increase in fission rate density in the fuel closest to the CEs and a corresponding increase in neutron multiplication on the order of 100 pcm. The absorption behavior exhibited by the discrete CEs is markedly different from the homogeneous CEs due to several competing effects. Self-shielding arising from absorber lumping acts to reduce the effective absorption cross section of the discrete CEs, but this effect is offset by geometric and spectral effects. The operational performance of the discrete CEs is found to be comparable to the homogeneous CEs, with only limited deficiencies in reactivity worth that are expected to be operationally recoverable via limited adjustment of the CE positions and withdrawal rate. On the whole, these results indicate that the discrete CEs perform reasonably similarly to the homogeneous CEs and appear feasible for application in HFIR. In conclusion, the physical phenomena identified in this study provide valuable background for follow-up design studies.« less

Reactor physics phenomena in additively manufactured control elements for the High Flux Isotope Reactor

DOE PAGES

Burns, Joseph R.; Petrovic, Bojan; Chandler, David; ...

2018-02-22

Additive manufacturing is under investigation as a novel method of fabricating the control elements (CEs) of the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory with greater simplicity, eliminating numerous highly complex fabrication steps and thereby offering potential for significant savings in cost, time, and effort. This process yields a unique CE design with lumped absorbers, a departure from traditionally manufactured CEs with uniformly distributed absorbing material. Here, this study undertakes a neutronics analysis of the impact of additively manufactured CEs on the HFIR core physics, seeking preliminary assessment of the feasibility of their practical use. The resultsmore » of the MCNP transport simulations reveal changes in the HFIR reactor physics arising from geometric and nuclear effects. Absorber lumping in the discrete CEs yields a large volume of unpoisoned material that is not present in the homogeneous design, in turn yielding increases in free thermal flux in the CE absorbing regions and their immediate vicinity. The availability of additional free thermal neutrons in the core yields an increase in fission rate density in the fuel closest to the CEs and a corresponding increase in neutron multiplication on the order of 100 pcm. The absorption behavior exhibited by the discrete CEs is markedly different from the homogeneous CEs due to several competing effects. Self-shielding arising from absorber lumping acts to reduce the effective absorption cross section of the discrete CEs, but this effect is offset by geometric and spectral effects. The operational performance of the discrete CEs is found to be comparable to the homogeneous CEs, with only limited deficiencies in reactivity worth that are expected to be operationally recoverable via limited adjustment of the CE positions and withdrawal rate. On the whole, these results indicate that the discrete CEs perform reasonably similarly to the homogeneous CEs and appear feasible for application in HFIR. In conclusion, the physical phenomena identified in this study provide valuable background for follow-up design studies.« less

Energy transfer processes between Tm(3+) and Ho(3+) in LiYF4. Ph.D. Thesis Final Report

NASA Technical Reports Server (NTRS)

Oezen, Goenuel

1991-01-01

The spectroscopic properties of the crystal LiYF4 doped with Thulium (Tm) and Holmium (Ho) ions are studied. The basic processes are discussed that regulate the transfer of energy between these two ions in this crystal. In this system Tm is considered the donor ion and the Ho the acceptor ion. Spectral data were obtained on three samples available: LiYF4:Tm(3+) (0.5 percent), LiYF4:Ho(3+) (1 percent), and LiYF4:Tm(3+) (5 percent), Ho(3+) (0.2 percent). Spectral data, which include absorption, luminescence, excitation, and the response to pulsed excitation in a wide range of temperatures, allowed to look at the energy transfer processes by considering the kinetic evolution of the emission of the two ions (donor and acceptor) involved in the process and the basic spectroscopic properties related to them. This inclusive approach has led to the validation of the physical model.

The use of the Novosol process for the treatment of polluted marine sediment.

PubMed

Zoubeir, Lafhaj; Adeline, Saliceto; Laurent, Cohen Solal; Yoann, Coudray; Truc, Huynh Trung; Benoît, Le Guen; Federico, Anguoni

2007-09-30

The work presented in this article concerns polluted marine sediments. The article is divided into three parts. The first part discusses existing industrial procedures of treatment. The second part introduces the Novosol((R)) process, which was used for the treatment of polluted marine sediments. This process is based on the stabilization of heavy metals in the solid matrix by phosphatation and the destruction of organic matter by calcination. Finally, after a comparison had been made between environmental results obtained on both polluted marine sediments and inert ones, treated sediments were introduced in the production of clay bricks. The results obtained show that the Novosol process leads to the immobilization of most heavy metals and can be considered as an efficient tool for the stabilisation of polluted marine sediment. Thus, the results of physical and mechanical tests as compressive strength and water absorption indicate that performances obtained were comparable to standard brick values. These results confirm that, once treated, polluted sediments can be recycled.

Physics of the Microwave Oven

ERIC Educational Resources Information Center

Vollmer, Michael

2004-01-01

This is the first of two articles about the physics of microwave ovens. This article deals with the generation of microwaves in the oven and includes the operation of the magnetrons, waveguides and standing waves in resonant cavities. It then considers the absorption of microwaves by foods, discussing the dielectric relaxation of water,…

Simulation of deleterious processes in a static-cell diode pumped alkali laser

NASA Astrophysics Data System (ADS)

Oliker, Benjamin Q.; Haiducek, John D.; Hostutler, David A.; Pitz, Greg A.; Rudolph, Wolfgang; Madden, Timothy J.

2014-02-01

The complex interactions in a diode pumped alkali laser (DPAL) gain cell provide opportunities for multiple deleterious processes to occur. Effects that may be attributable to deleterious processes have been observed experimentally in a cesium static-cell DPAL at the United States Air Force Academy [B.V. Zhdanov, J. Sell, R.J. Knize, "Multiple laser diode array pumped Cs laser with 48 W output power," Electronics Letters, 44, 9 (2008)]. The power output in the experiment was seen to go through a "roll-over"; the maximum power output was obtained with about 70 W of pump power, then power output decreased as the pump power was increased beyond this point. Research to determine the deleterious processes that caused this result has been done at the Air Force Research Laboratory utilizing physically detailed simulation. The simulations utilized coupled computational fluid dynamics (CFD) and optics solvers, which were three-dimensional and time-dependent. The CFD code used a cell-centered, conservative, finite-volume discretization of the integral form of the Navier-Stokes equations. It included thermal energy transport and mass conservation, which accounted for chemical reactions and state kinetics. Optical models included pumping, lasing, and fluorescence. The deleterious effects investigated were: alkali number density decrease in high temperature regions, convective flow, pressure broadening and shifting of the absorption lineshape including hyperfine structure, radiative decay, quenching, energy pooling, off-resonant absorption, Penning ionization, photoionization, radiative recombination, three-body recombination due to free electron and buffer gas collisions, ambipolar diffusion, thermal aberration, dissociative recombination, multi-photon ionization, alkali-hydrocarbon reactions, and electron impact ionization.

Utilization of lignite power generation residues for the production of lightweight aggregates.

PubMed

Anagnostopoulos, Iason M; Stivanakis, Victor E

2009-04-15

A novel process is proposed for the utilization of lignite combustion solid residues in the production of inflammable lightweight aggregates (LWA). The process consists of two stages, pelletization and sintering, and carbon contained in BA was used as the process fuel. The main residues bottom ash (BA) and fly ash (FA) from Megalopolis power plant were characterized, mixed in different proportions and treated through pelletization and sintering process. Sintering benefits from combustion of BA carbon content and the product is a hardened porous cake. The energy required for achievement of high temperatures, in the range of 1250 degrees C, was offered by carbon combustion and CO(2) evolution is responsible for porous structure formation. Selected physical properties of sintered material relevant to use as lightweight aggregates were determined, including bulk density, porosity and water absorption. Bulk density varies from 0.83 to 0.91 g/cm(3), porosity varies from 60% to 64% and water absorption varies from 66% to 80%. LWA formed is used for the production of lightweight aggregate concrete (LWAC). Thermal conductivity coefficient varies from 0.25 to 0.37 W/mK (lower than maximum limit 0.43 W/mK) and compressive strength varies from 19 to 23 MPa (higher than minimum limit 17 MPa). The results indicate that sintering of lignite combustion residues is an efficient method of utilization of carbon containing BA and production of LWA for structural and insulating purposes. Carbon content of BA is a key factor in LWA production. Finally, this research work comprises the first proposed application for utilization of BA in Greece.

Abnormal passive chloride absorption in cystic fibrosis jejunum functionally opposes the classic chloride secretory defect

PubMed Central

Russo, Michael A.; Högenauer, Christoph; Coates, Stephen W.; Santa Ana, Carol A.; Porter, Jack L.; Rosenblatt, Randall L.; Emmett, Michael; Fordtran, John S.

2003-01-01

Due to genetic defects in apical membrane chloride channels, the cystic fibrosis (CF) intestine does not secrete chloride normally. Depressed chloride secretion leaves CF intestinal absorptive processes unopposed, which results in net fluid hyperabsorption, dehydration of intestinal contents, and a propensity to inspissated intestinal obstruction. This theory is based primarily on in vitro studies of jejunal mucosa. To determine if CF patients actually hyperabsorb fluid in vivo, we measured electrolyte and water absorption during steady-state perfusion of the jejunum. As expected, chloride secretion was abnormally low in CF, but surprisingly, there was no net hyperabsorption of sodium or water during perfusion of a balanced electrolyte solution. This suggested that fluid absorption processes are reduced in CF jejunum, and further studies revealed that this was due to a marked depression of passive chloride absorption. Although Na+-glucose cotransport was normal in the CF jejunum, absence of passive chloride absorption completely blocked glucose-stimulated net sodium absorption and reduced glucose-stimulated water absorption 66%. This chloride absorptive abnormality acts in physiological opposition to the classic chloride secretory defect in the CF intestine. By increasing the fluidity of intraluminal contents, absence of passive chloride absorption may reduce the incidence and severity of intestinal disease in patients with CF. PMID:12840066

Removing sulphur oxides from a fluid stream

DOEpatents

Katz, Torsten; Riemann, Christian; Bartling, Karsten; Rigby, Sean Taylor; Coleman, Luke James Ivor; Lail, Marty Alan

2014-04-08

A process for removing sulphur oxides from a fluid stream, such as flue gas, comprising: providing a non-aqueous absorption liquid containing at least one hydrophobic amine, the liquid being incompletely miscible with water; treating the fluid stream in an absorption zone with the non-aqueous absorption liquid to transfer at least part of the sulphur oxides into the non-aqueous absorption liquid and to form a sulphur oxide-hydrophobic amine-complex; causing the non-aqueous absorption liquid to be in liquid-liquid contact with an aqueous liquid whereby at least part of the sulphur oxide-hydrophobic amine-complex is hydrolyzed to release the hydrophobic amine and sulphurous hydrolysis products, and at least part of the sulphurous hydrolysis products is transferred into the aqueous liquid; separating the aqueous liquid from the non-aqueous absorption liquid. The process mitigates absorbent degradation problems caused by sulphur dioxide and oxygen in flue gas.

Carbonic anhydrase-facilitated CO2 absorption with polyacrylamide buffering bead capture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dilmore, Robert; Griffith, Craid; Liu, Zhu

2009-07-01

A novel CO2 separation concept is described wherein the enzyme carbonic anhydrase (CA) is used to increase the overall rate Of CO2 absorption after which hydrated CO2 reacts with regenerable amine-bearing polyacrylamide buffering beads (PABB). Following saturation of the material's immobilized tertiary amines, CA-bearing carrier water is separated and recycled to the absorption stage while CO2-loaded material is thermally regenerated. Process application of this concept would involve operation of two or more columns in parallel with thermal regeneration with low-pressure steam taking place after the capacity of a column of amine-bearing polymeric material was exceeded. PABB CO2- bearing capacity wasmore » evaluated by thermogravimetric analysis (TGA) for beads of three acrylamido buffering monomer ingredient concentrations: 0 mol/kg bead, 0.857 mol/kg bead, and 2 mol/kg bead. TGA results demonstrate that CO2- bearing capacity increases with increasing PABB buffering concentration and that up to 78% of the theoretical CO2- bearing capacity was realized in prepared PABB samples (0.857 mol/kg recipe). The highest observed CO2-bearing capacity of PABB was 1.37 mol of CO2 per kg dry bead. TGA was also used to assess the regenerability Of CO2-loaded PABB. Preliminary results suggest that CO2 is partially driven from PABB samples at temperatures as low as 55 degrees C, with complete regeneration occurring at 100 degrees C. Other physical characteristics of PABB are discussed. In addition, the effectiveness of bovine carbonic anhydrase for the catalysis Of CO2 dissolution is evaluated. Potential benefits and drawbacks of the proposed process are discussed. Published by Elsevier Ltd.« less

[Construction of research system for processing mechanism of traditional Chinese medicine based on chemical composition transformation combined with intestinal absorption barrier].

PubMed

Sun, E; Xu, Feng-Juan; Zhang, Zhen-Hai; Wei, Ying-Jie; Tan, Xiao-Bin; Cheng, Xu-Dong; Jia, Xiao-Bin

2014-02-01

Based on practice of Epimedium processing mechanism for many years and integrated multidisciplinary theory and technology, this paper initially constructs the research system for processing mechanism of traditional Chinese medicine based on chemical composition transformation combined with intestinal absorption barrier, which to form an innovative research mode of the " chemical composition changes-biological transformation-metabolism in vitro and in vivo-intestinal absorption-pharmacokinetic combined pharmacodynamic-pharmacodynamic mechanism". Combined with specific examples of Epimedium and other Chinese herbal medicine processing mechanism, this paper also discusses the academic thoughts, research methods and key technologies of this research system, which will be conducive to systematically reveal the modem scientific connotation of traditional Chinese medicine processing, and enrich the theory of Chinese herbal medicine processing.

Effect of cellulose nanocrystals (CNC) addition and citric acid as co-plasticizer on physical properties of sago starch biocomposite

NASA Astrophysics Data System (ADS)

Nasution, Halimatuddahliana; Afandy, Yayang; Al-fath, M. Thoriq

2018-04-01

Cellulose has potential applications in new high-performance materials with low environmental impact. Rattan biomass is a fiber waste from processing industry of rattan which contains 37,6% cellulose. The high cellulose contents of rattan biomass make it a source of cellulose nanocrystals as a filler in biocomposite. Isolation of alpha cellulose from biomass rattan was prepared by using three stages: delignification, alkalization, and bleaching. It was delignificated with 3,5% HNO3 and NaNO2, precipitated with 17,5% NaOH, bleaching process with 10% H2O2. Nanocrystals obtained through the hydrolysis of alpha cellulose using 45% H2SO4 and followed by mechanical processes of ultrasonication, centrifugation, and filtration with a dialysis membrane. Sago starch biocomposites were prepared using a solution casting method, which includes 1-4 wt % cellulose nanocrystals rattan biomass as fillers, 10-40 wt% citric acid as co-plasticizer and 30 wt% glycerol as plasticizer. The results of TEM and FTIR characteristic of cellulose nanocrystals show spherical like shape FTIR and chemical composition analysis demonstrated that lignin and hemicellulose structures were successfully removed. Biocomposite characteristic consists of density and water absorption. The results showed the highest density values were 0,266 gram/cm3 obtained at an additional of 3% cellulose nanocrystals rattan biomass and 30% citric acid. The lowest water absorption was 7,893% obtained at an additional of 4% cellulose nanocrystals rattan biomass and 10% citric acid.

A Fundamental Test for Galaxy Formation Models: Matching the Lyman-α Absorption Profiles of Galactic Halos Over Three Decades in Distance

NASA Astrophysics Data System (ADS)

Sorini, Daniele; Oñorbe, José; Hennawi, Joseph F.; Lukić, Zarija

2018-06-01

Galaxy formation depends critically on the physical state of gas in the circumgalactic medium (CGM) and its interface with the intergalactic medium (IGM), determined by the complex interplay between inflow from the IGM and outflows from supernovae and/or AGN feedback. The average Lyα absorption profile around galactic halos represents a powerful tool to probe their gaseous environments. We compare predictions from Illustris and Nyx hydrodynamical simulations with the observed absorption around foreground quasars, damped Lyα systems, and Lyman-break galaxies. We show how large-scale BOSS and small-scale quasar pair measurements can be combined to precisely constrain the absorption profile over three decades in transverse distance 20 {kpc}≲ b≲ 20 {Mpc}. Far from galaxies, ≳ 2 {Mpc}, the simulations converge to the same profile and provide a reasonable match to the observations. This asymptotic agreement arises because the ΛCDM model successfully describes the ambient IGM and represents a critical advantage of studying the mean absorption profile. However, significant differences between the simulations, and between simulations and observations, are present on scales 20 {kpc}≲ b≲ 2 {Mpc}, illustrating the challenges of accurately modeling and resolving galaxy formation physics. It is noteworthy that these differences are observed as far out as ∼ 2 {Mpc}, indicating that the “sphere of influence” of galaxies could extend to approximately ∼7 times the halo virial radius. Current observations are very precise on these scales and can thus strongly discriminate between different galaxy formation models. We demonstrate that the Lyα absorption profile is primarily sensitive to the underlying temperature–density relationship of diffuse gas around galaxies, and argue that it thus provides a fundamental test of galaxy formation models.

Enhancement of transmission of laser and other radiation by soft turbid physical and biological media

NASA Astrophysics Data System (ADS)

Askar'yan, G. A.

1982-07-01

An analysis is made and experimental results are reported of studies of the transmission of laser and other radiation by turbid physical and biological media, such as layers of a scattering medium or human tissue of thickness much greater than the characteristic attenuation length. It is reported that the transmission increases strongly as a result of depression and piercing of soft scattering media. A local pressure applied to a biological tissue produces a transmission enhancement considerably greater than compression of a layer of a physically turbid medium: this is due to the displacement of blood and of muscle out of the compressed region. A reduction in the scattering and absorption is expected to occur also in the case of rf and ionizing radiations, such as charged particles, x rays, gamma rays, etc. It is pointed out that this could be useful in deep irradiation carried out with the aim of inhibiting internal morbid processes (for example, in the spinal cord) and in treatment of neuroinfectious diseases (amyotrophic lateral sclerosis, multiple sclerosis, poliomyelitis, etc.), as well as in oncological conditions, ulcers, etc.

Dual Mechanism Nonlinear Response of Selected Metal Organic Chromophores

DTIC Science & Technology

2007-10-01

emission was observed due to the high quantum efficiency of the free ligand despite having a relatively low two photon cross section at this wavelength...nonlinear absorbing chromophores. .............................30 2-1 Beer’s Law relationships of linear absorption...optical processes; (4) structure-property relationships of nonlinear absorption as it relates to two photon absorption and reverse saturable absorption

Contributions of the ARM Program to Radiative Transfer Modeling for Climate and Weather Applications

NASA Technical Reports Server (NTRS)

Mlawer, Eli J.; Iacono, Michael J.; Pincus, Robert; Barker, Howard W.; Oreopoulos, Lazaros; Mitchell, David L.

2016-01-01

Accurate climate and weather simulations must account for all relevant physical processes and their complex interactions. Each of these atmospheric, ocean, and land processes must be considered on an appropriate spatial and temporal scale, which leads these simulations to require a substantial computational burden. One especially critical physical process is the flow of solar and thermal radiant energy through the atmosphere, which controls planetary heating and cooling and drives the large-scale dynamics that moves energy from the tropics toward the poles. Radiation calculations are therefore essential for climate and weather simulations, but are themselves quite complex even without considering the effects of variable and inhomogeneous clouds. Clear-sky radiative transfer calculations have to account for thousands of absorption lines due to water vapor, carbon dioxide, and other gases, which are irregularly distributed across the spectrum and have shapes dependent on pressure and temperature. The line-by-line (LBL) codes that treat these details have a far greater computational cost than can be afforded by global models. Therefore, the crucial requirement for accurate radiation calculations in climate and weather prediction models must be satisfied by fast solar and thermal radiation parameterizations with a high level of accuracy that has been demonstrated through extensive comparisons with LBL codes. See attachment for continuation.

Complex (dusty) plasmas-kinetic studies of strong coupling phenomena

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morfill, Gregor E.; Ivlev, Alexei V.; Thomas, Hubertus M.

2012-05-15

'Dusty plasmas' can be found almost everywhere-in the interstellar medium, in star and planet formation, in the solar system in the Earth's atmosphere, and in the laboratory. In astrophysical plasmas, the dust component accounts for only about 1% of the mass, nevertheless this component has a profound influence on the thermodynamics, the chemistry, and the dynamics. Important physical processes are charging, sputtering, cooling, light absorption, and radiation pressure, connecting electromagnetic forces to gravity. Surface chemistry is another important aspect. In the laboratory, there is great interest in industrial processes (e.g., etching, vapor deposition) and-at the fundamental level-in the physics ofmore » strong coupling phenomena. Here, the dust (or microparticles) are the dominant component of the multi-species plasma. The particles can be observed in real time and space, individually resolved at all relevant length and time scales. This provides an unprecedented means for studying self-organisation processes in many-particle systems, including the onset of cooperative phenomena. Due to the comparatively large mass of the microparticles (10{sup -12}to10{sup -9}g), precision experiments are performed on the ISS. The following topics will be discussed: Phase transitions, phase separation, electrorheology, flow phenomena including the onset of turbulence at the kinetic level.« less

Gamma ray astrophysics. [emphasizing processes and absorption

NASA Technical Reports Server (NTRS)

Stecker, F. W.

1974-01-01

Gamma ray production processes are reviewed, including Compton scattering, synchrotron radiation, bremsstrahlung interactions, meson decay, nucleon-antinucleon annihilations, and pion production. Gamma ray absorption mechanisms through interactions with radiation and with matter are discussed, along with redshifts and gamma ray fluxes.

Capillary absorption spectrometer and process for isotopic analysis of small samples

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alexander, M. Lizabeth; Kelly, James F.; Sams, Robert L.

A capillary absorption spectrometer and process are described that provide highly sensitive and accurate stable absorption measurements of analytes in a sample gas that may include isotopologues of carbon and oxygen obtained from gas and biological samples. It further provides isotopic images of microbial communities that allow tracking of nutrients at the single cell level. It further targets naturally occurring variations in carbon and oxygen isotopes that avoids need for expensive isotopically labeled mixtures which allows study of samples taken from the field without modification. The process also permits sampling in vivo permitting real-time ambient studies of microbial communities.

Morphological and Electrochemical Characterization of Nanostructured Li 4Ti 5O 12 Electrodes Using Multiple Imaging Mode Synchrotron X-ray Computed Tomography

DOE PAGES

Kashkooli, Ali Ghorbani; Foreman, Evan; Farhad, Siamak; ...

2017-09-21

In this study, synchrotron X-ray computed tomography has been utilized using two different imaging modes, absorption and Zernike phase contrast, to reconstruct the real three-dimensional (3D) morphology of nanostructured Li 4Ti 5O 12 (LTO) electrodes. The morphology of the high atomic number active material has been obtained using the absorption contrast mode, whereas the percolated solid network composed of active material and carbon-doped polymer binder domain (CBD) has been obtained using the Zernike phase contrast mode. The 3D absorption contrast image revealed that some LTO nano-particles tend to agglomerate and form secondary micro-sized particles with varying degrees of sphericity. Themore » tortuosity of electrode’s pore and solid phases were found to have directional dependence, different from Bruggeman’s tortuosity commonly used in macro-homogeneous models. The electrode’s heterogeneous structure was investigated by developing a numerical model to simulate galvanostatic discharge process using the Zernike phase contrast mode. The inclusion of CBD in the Zernike phase contrast results in an integrated percolated network of active material and CBD that is highly suited for continuum modeling. As a result, the simulation results highlight the importance of using the real 3D geometry since the spatial distribution of physical and electrochemical properties have a strong non-uniformity due to microstructural heterogeneities.« less

Probing the CZTS/CdS heterojunction utilizing photoelectrochemistry and x-ray absorption spectroscopy

NASA Astrophysics Data System (ADS)

Turnbull, Matthew J.; Vaccarello, Daniel; Wong, Jonathan; Yiu, Yun Mui; Sham, Tsun-Kong; Ding, Zhifeng

2018-04-01

The importance of renewable resources is becoming more and more influential on research due to the depletion of fossil fuels. Cost-effective ways of harvesting solar energy should also be at the forefront of these investigations. Cu2ZnSnS4 (CZTS) solar cells are well within the frame of these goals, and a thorough understanding of how they are made and processed synthetically is crucial. The CZTS/CdS heterojunction was examined using photoelectrochemistry and synchrotron radiation (SR) spectroscopy. These tools provided physical insights into this interface that was formed by the electrophoretic deposition of CZTS nanocrystals and chemical bath deposition (CBD) of CdS for the respective films. It was discovered that CBD induced a change in the local and long range environment of the Zn in the CZTS lattice, which was detrimental to the photoresponse. X-ray absorption near-edge structures and extended X-ray absorption fine structures (EXAFSs) of the junction showed that this change was at an atomic level and was associated with the coordination of oxygen to zinc. This was confirmed through FEFF fitting of the EXAFS and through IR spectroscopy. It was found that this change in both photoresponse and the Zn coordination can be reversed with the use of low temperature annealing. Investigating CZTS through SR techniques provides detailed structural information of minor changes from the zinc perspective.

Phototransduction early steps model based on Beer-Lambert optical law.

PubMed

Salido, Ezequiel M; Servalli, Leonardo N; Gomez, Juan Carlos; Verrastro, Claudio

2017-02-01

The amount of available rhodopsin on the photoreceptor outer segment and its change over time is not considered in classic models of phototransduction. Thus, those models do not take into account the absorptance variation of the outer segment under different brightness conditions. The relationship between the light absorbed by a medium and its absorptance is well described by the Beer-Lambert law. This newly proposed model implements the absorptance variation phenomenon in a set of equations that admit photons per second as input and results in active rhodopsins per second as output. This study compares the classic model of phototransduction developed by Forti et al. (1989) to this new model by using different light stimuli to measure active rhodopsin and photocurrent. The results show a linear relationship between light stimulus and active rhodopsin in the Forti model and an exponential saturation in the new model. Further, photocurrent values have shown that the new model behaves equivalently to the experimental and theoretical data as published by Forti in dark-adapted rods, but fits significantly better under light-adapted conditions. The new model successfully introduced a physics optical law to the standard model of phototransduction adding a new processing layer that had not been mathematically implemented before. In addition, it describes the physiological concept of saturation and delivers outputs in concordance to input magnitudes. Copyright © 2017 Elsevier Ltd. All rights reserved.

Chromatic Mechanical Response in 2-D Layered Transition Metal Dichalcogenide (TMDs) based Nanocomposites

PubMed Central

Rahneshin, Vahid; Khosravi, Farhad; Ziolkowska, Dominika A.; Jasinski, Jacek B.; Panchapakesan, Balaji

2016-01-01

The ability to convert photons of different wavelengths directly into mechanical motion is of significant interest in many energy conversion and reconfigurable technologies. Here, using few layer 2H-MoS2 nanosheets, layer by layer process of nanocomposite fabrication, and strain engineering, we demonstrate a reversible and chromatic mechanical response in MoS2-nanocomposites between 405 nm to 808 nm with large stress release. The chromatic mechanical response originates from the d orbitals and is related to the strength of the direct exciton resonance A and B of the few layer 2H-MoS2 affecting optical absorption and subsequent mechanical response of the nanocomposite. Applying uniaxial tensile strains to the semiconducting few-layer 2H-MoS2 crystals in the nanocomposite resulted in spatially varying energy levels inside the nanocomposite that enhanced the broadband optical absorption up to 2.3 eV and subsequent mechanical response. The unique photomechanical response in 2H-MoS2 based nanocomposites is a result of the rich d electron physics not available to nanocomposites based on sp bonded graphene and carbon nanotubes, as well as nanocomposite based on metallic nanoparticles. The reversible strain dependent optical absorption suggest applications in broad range of energy conversion technologies that is not achievable using conventional thin film semiconductors. PMID:27713550

An evaluation of in vitro intestinal absorption of iron, calcium and potassium in chickens receiving gold nanoparticles.

PubMed

Sembratowicz, I; Ognik, K; Stępniowska, A

2016-08-01

This study evaluated the effect of oral administration of colloidal gold nanoparticles on accumulation of gold in the small intestine and intestinal absorption of iron, calcium and potassium under in vitro conditions. The gold nanoparticles are non-ionic, nanocrystalline, chemically pure particles 5 nm in size, produced in a physical process. In total, 126 one day-old Ross 308 chicks were assigned to 7 experimental groups of 18 birds each (3 replications of 6 individuals each). The control group (G-C) did not receive gold nanoparticles. Groups: Au-5(7), Au-10(7) and Au-15(7) received gold nanoparticles in their drinking water in the amounts of 5 mg l(-1) for group Au-5(7), 10 mg l(-1) for group Au-10(7) and 15 mg l(-1) for group Au-15(7) in 8-14, 22-28 and 36-42 d of life. The birds in groups Au-5(3), Au-10(3) and Au-15(3) received gold nanoparticles in the same amounts, but only in 8-10, 22-24 and 36-38 d of life. The study revealed that nanogold supplied via ingestion leads to dose- and time-dependent accumulation of gold in the intestinal walls. Nanogold present in the jejunum has a negative impact on the absorption of calcium, iron and potassium under in vitro conditions.

Energy Absorption Mechanisms in Unidirectional Composites Subjected to Dynamic Loading Events

DTIC Science & Technology

2012-03-30

integral part of commercial, recreation, and defense markets . The proliferation of applications for fiber-reinforced composite technology can be in large...soft body armors. The growth of composites in high-performance markets continues to outpace the development of new and improved physics-based...pp. 718 – 730, 2008. 16. G. C. Jacob, J. F. Fellers, S. Simunovic, and J. M. Starbuck , “Energy Absorption in Polymer Composites for

Bioavailability enhancement of curcumin by complexation with phosphatidyl choline.

PubMed

Gupta, Nishant Kumar; Dixit, Vinod Kumar

2011-05-01

Curcumin is a major constituent of rhizomes of Curcuma longa. Pharmacokinetic studies of curcumin reveal its poor absorption through intestine. Objective of the present study was to enhance bioavailability of curcumin by its complexation with phosphatidyl choline (PC). Complex of curcumin was prepared with PC and characterized on the basis of solubility, melting point, differential scanning calorimetry, thin layer chromatography, and infrared spectroscopic analysis. Everted intestine sac technique was used to study ex vivo drug absorption of curcumin-PC (CU-PC) complex and plain curcumin. Pharmacokinetic studies were performed in rats, and hepatoprotective activity of CU-PC complex was also compared with curcumin and CU-PC physical mixture in isolated rat hepatocytes. Analytical reports along with spectroscopic data revealed the formation of complex. The results of ex vivo study show that CU-PC complex has significantly increased absorption compared with curcumin, when given in equimolar doses. Complex showed enhanced bioavailability, improved pharmacokinetics, and increased hepatoprotective activity as compared with curcumin or CU-PC physical mixture. Enhanced bioavailability of CU-PC complex may be due to the amphiphilic nature of the complex, which greatly enhance the water and lipid solubility of the curcumin. The present study clearly indicates the superiority of complex over curcumin, in terms of better absorption, enhanced bioavailability, and improved pharmacokinetics. Copyright © 2010 Wiley-Liss, Inc.

Simulation based comparative analysis of photoresponse in front- and back-illuminated GaN P-I-N ultraviolet photodetectors

NASA Astrophysics Data System (ADS)

Wang, Jun; Guo, Jin; Xie, Feng; Wang, Guosheng; Wu, Haoran; Song, Man; Yi, Yuanyuan

2016-10-01

This paper presents the comparative analysis of influence of doping level and doping profile of the active region on zero bias photoresponse characteristics of GaN-based p-i-n ultraviolet (UV) photodetectors operating at front- and back-illuminated. A two dimensional physically-based computer simulation of GaN-based p-i-n UV photodetectors is presented. We implemented GaN material properties and physical models taken from the literature. It is shown that absorption layer doping profile has notable impacts on the photoresponse of the device. Especially, the effect of doping concentration and distribution of the absorption layer on photoresponse is discussed in detail. In the case of front illumination, comparative to uniform n-type doping, the device with n-type Gaussian doping profiles at absorption layer has higher responsivity. Comparative to front illumination, back illuminated detector with p-type doping profiles at absorption layer has higher maximum photoresponse, while the Gaussian doping profiles have a weaker ability to enhance the device responsivity. It is demonstrated that electric field distribution, mobility degradation, and recombinations are jointly responsible for the variance of photoresponse. Our work enriches the understanding and utilization of GaN based p-i-n UV photodetectors.

Kinetics study of carbon dioxide absorption reaction into the promoted methyldiethanolamine solution

NASA Astrophysics Data System (ADS)

Sitorus, Yasmikha Tiurlan Susanti; Taurina, Hanna Sucita; Altway, Ali; Rahmawati, Yeni; Nurkhamidah, Siti

2017-05-01

The absorption of carbon dioxide (CO2) is important in the industrial world. In industries, especially petrochemical, oil, and natural gas sectors, separation process of CO2 gas which is a corrosive gas (acid gas) is required. So, the separation process of CO2 gas stream is important, one of the methods used to remove CO2 from the gas stream is reactive absorption process using the promoted methyldiethanolamine (MDEA) solution. Therefore, this study is aimed to obtain the reaction kinetics data of CO2 absorption in MDEA solution using arginine as a promoter. Arginine was chosen because of its amino acid molecule which is reactive, so it can accelerate the reaction rate of MDEA. Moreover, this study also made a comparison between the reactivity of MDEA solution using arginine and MDEA solution using other promoters (glycine and piperazine) for CO2 absorption. The method used is absorption using laboratory scale of Wetted Wall Column (WWC) equipment at 1 atm. This study provides the reaction kinetics data information in order to optimize the separation process of CO2 in the industrialized world. The experimental results show that CO2 absorption rate at 323.15 K without any additon of arginine is 2.33 × 10-7 kmol/sec. By addition of 0.5 and 1 wt% of arginine, the absorption rate becomes 4 × 10-7 kmol/sec (2 times larger) and 6 × 10-7 kmol/sec (3 times larger). These results show that the addition of arginine as a promoter can increase the absorption rate of CO2 in MDEA solution and cover the weaknesses of MDEA solution. Based on the experimental result, the reaction kinetics constant for arginine is 1.91 × 1025 exp (-12296/T) (m3/kmol.s). Although, arginine reaction rate constant is lower than glycine and piperazine.

Broad-spectrum enhanced absorption of graphene-molybdenum disulfide photovoltaic cells in metal-mirror microcavity.

PubMed

Jiang-Tao, Liu; Yun-Kai, Cao; Hong, Tong; Dai-Qiang, Wang; Zhen-Hua, Wu

2018-04-06

The optical absorption of graphene-molybdenum disulfide photovoltaic cells (GM-PVc) in wedge-shaped metal-mirror microcavities (w-MMCs) combined with a spectrum-splitting structure was studied. Results showed that the combination of spectrum-splitting structure and w-MMC can enable the light absorption of GM-PVcs to reach about 65% in the broad spectrum. The influence of processing errors on the absorption of GM-PVcs in w-MMCs was 3-14 times lower than that of GM-PVcs in wedge photonic crystal microcavities. The light absorption of GM-PVcs reached 60% in the broad spectrum, even with the processing errors. The proposed structure is easy to implement and may have potentially important applications in the development of ultra-thin and high-efficiency solar cells and optoelectronic devices.

Broad-spectrum enhanced absorption of graphene-molybdenum disulfide photovoltaic cells in metal-mirror microcavity

NASA Astrophysics Data System (ADS)

Jiang-Tao, Liu; Yun-Kai, Cao; Hong, Tong; Dai-Qiang, Wang; Zhen-Hua, Wu

2018-04-01

The optical absorption of graphene-molybdenum disulfide photovoltaic cells (GM-PVc) in wedge-shaped metal-mirror microcavities (w-MMCs) combined with a spectrum-splitting structure was studied. Results showed that the combination of spectrum-splitting structure and w-MMC can enable the light absorption of GM-PVcs to reach about 65% in the broad spectrum. The influence of processing errors on the absorption of GM-PVcs in w-MMCs was 3-14 times lower than that of GM-PVcs in wedge photonic crystal microcavities. The light absorption of GM-PVcs reached 60% in the broad spectrum, even with the processing errors. The proposed structure is easy to implement and may have potentially important applications in the development of ultra-thin and high-efficiency solar cells and optoelectronic devices.

Calculation tool for transported geothermal energy using two-step absorption process

DOE Data Explorer

Kyle Gluesenkamp

2016-02-01

This spreadsheet allows the user to calculate parameters relevant to techno-economic performance of a two-step absorption process to transport low temperature geothermal heat some distance (1-20 miles) for use in building air conditioning. The parameters included are (1) energy density of aqueous LiBr and LiCl solutions, (2) transportation cost of trucking solution, and (3) equipment cost for the required chillers and cooling towers in the two-step absorption approach. More information is available in the included public report: "A Technical and Economic Analysis of an Innovative Two-Step Absorption System for Utilizing Low-Temperature Geothermal Resources to Condition Commercial Buildings"

Energy Absorption of Expansion Tube Considering Local Buckling Characteristics

NASA Astrophysics Data System (ADS)

Ahn, Kwang-Hyun; Kim, Jin-Sung; Huh, Hoon

This paper deals with the crash energy absorption and the local buckling characteristics of the expansion tube during the tube expanding processes. In order to improve energy absorption capacity of expansion tubes, local buckling characteristics of an expansion tube must be considered. The local buckling load and the absorbed energy during the expanding process were calculated for various types of tubes and punch shapes with finite element analysis. The energy absorption capacity of the expansion tube is influenced by the tube and the punch shape. The material properties of tubes are also important parameter for energy absorption. During the expanding process, local buckling occurs in some cases, which causes significant decreasing the absorbed energy of the expansion tube. Therefore, it is important to predict the local buckling load accurately to improve the energy absorption capacity of the expansion tube. Local buckling takes place relatively easily at the large punch angle and expansion ratio. Local buckling load is also influenced by both the tube radius and the thickness. In prediction of the local buckling load, modified Plantema equation was used for strain hardening and strain rate hardening. The modified Plantema equation shows a good agreement with the numerical result.

Vanderbilt free-electron-laser project in biomedical and materials research. Annual report, 1 February 1987-31 January 1988

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haglund, R.F.; Tolk, N.H.

The Medical Free Electron Laser Program was awarded to develop, construct and operate a free-electron laser facility dedicated to biomedical and materials studies, with particular emphases on: fundamental studies of absorption and localization of electromagnetic energy on and near material surfaces, especially through electronic and other selective, non-statistical processes; non-thermal photon-materials interactions (e.g., electronic bond-breaking or vibrational energy transfer) in physical and biological materials as well as in long-wavelength biopolymer dynamics; development of FEL-based methods to study drug action and to characterize biomolecular properties and metabolic processes in biomembranes; clinical applications in otolaryngology, neurosurgery, ophthalmology and radiology stressing the usemore » of the laser for selective laser-tissue, laser-cellular and laser-molecule interactions in both therapeutic and diagnostic modalities.« less

Numerical modeling of pulsed laser-material interaction and of laser plume dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Qiang; Shi, Yina

2015-03-10

We have developed two-dimensional Arbitrary Lagrangian Eulerian (ALE) code which is used to study the physical processes, the plasma absorption, the crater profile, and the temperature distribution on metallic target and below the surface. The ALE method overcomes problems with Lagrangian moving mesh distortion by mesh smoothing and conservative quantities remapping from Lagrangian mesh to smoothed one. A new second order accurate diffusion solver has been implemented for the thermal conduction and radiation transport on distorted mesh. The results of numerical simulation of pulsed laser ablation are presented. The influences of different processes, such as time evolution of the surfacemore » temperature, interspecies interactions (elastic collisions, recombination-dissociation reaction), interaction with an ambient gas are examined. The study presents particular interest for the analysis of experimental results obtained during pulsed laser ablation.« less

Investigation of phase matching for third-harmonic generation in silicon slow light photonic crystal waveguides using Fourier optics.

PubMed

Monat, Christelle; Grillet, Christian; Corcoran, Bill; Moss, David J; Eggleton, Benjamin J; White, Thomas P; Krauss, Thomas F

2010-03-29

Using Fourier optics, we retrieve the wavevector dependence of the third-harmonic (green) light generated in a slow light silicon photonic crystal waveguide. We show that quasi-phase matching between the third-harmonic signal and the fundamental mode is provided in this geometry by coupling to the continuum of radiation modes above the light line. This process sustains third-harmonic generation with a relatively high efficiency and a substantial bandwidth limited only by the slow light window of the fundamental mode. The results give us insights into the physics of this nonlinear process in the presence of strong absorption and dispersion at visible wavelengths where bandstructure calculations are problematic. Since the characteristics (e.g. angular pattern) of the third-harmonic light primarily depend on the fundamental mode dispersion, they could be readily engineered.

THE ENERGY CONVERSION APPARATUS IN PHOTOSYNTHESIS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sauer, K.

1962-12-01

An analysis of outstanding problems still presenting difficulty with respect to understanding the quantumconversion process in photosynthesis is presented. Considerations of how some of these difficulties may be overcome are included. The dynamic process of energy conversion is considered in terms of photon absorption, electronic energy transfer, trapping in long-lived excited states, primary oxidants and reductants, and the electron transport chain leading to products representing stored chemical potential. The physical structure of the apparatus accomplishing this energy conversion is sought in the framework of the concept of the photosynthetic unit. The nature of this unit--its size, composition, arrangement and orientationmore » of components, internal electrical and polarizability properties, and assembly and aggregation in the chloroplast--and the problems related to its determination are essential considerations in the overall approach to the understanding of the mechanism of energy conversion. (auth)« less

Temperature effect on laser-induced breakdown spectroscopy spectra of molten and solid salts

NASA Astrophysics Data System (ADS)

Hanson, Cynthia; Phongikaroon, Supathorn; Scott, Jill R.

2014-07-01

Laser-induced breakdown spectroscopy (LIBS) has been investigated as a potential analytical tool to improve operations and safeguards for electrorefiners, such as those used in processing spent nuclear fuel. This study set out to better understand the effect of sample temperature and physical state on LIBS spectra of molten and solid salts by building calibration curves of cerium and assessing self-absorption, plasma temperature, electron density, and local thermal equilibrium (LTE). Samples were composed of a LiCl-KCl eutectic salt, an internal standard of MnCl2, and varying concentrations of CeCl3 (0.1, 0.3, 0.5, 0.8, and 1.0 wt.% Ce) under different temperatures (773, 723, 673, 623, and 573 K). Analysis of salts in their molten form is preferred as plasma plumes from molten samples experienced less self-absorption, less variability in plasma temperature, and higher clearance of the minimum electron density required for local thermal equilibrium. These differences are attributed to plasma dynamics as a result of phase changes. Spectral reproducibility was also better in the molten state due to sample homogeneity.

Resistant starch in food: a review.

PubMed

Raigond, Pinky; Ezekiel, Rajarathnam; Raigond, Baswaraj

2015-08-15

The nutritional property of starch is related to its rate and extent of digestion and absorption in the small intestine. For nutritional purposes, starch is classified as rapidly available, slowly available and resistant starch (RS). The exact underlying mechanism of relative resistance of starch granules is complicated because those factors are often interconnected. The content of RS in food is highly influenced by food preparation manner and processing techniques. Physical or chemical treatments also alter the level of RS in a food. Commercial preparations of RS are now available and can be added to foods as an ingredient for lowering the calorific value and improving textural and organoleptic characteristics along with increasing the amount of dietary fiber. RS has assumed great importance owing to its unique functional properties and health benefits. The beneficial effects of RS include glycemic control and control of fasting plasma triglyceride and cholesterol levels and absorption of minerals. This review attempts to analyze the information published, especially in the recent past, on classification, structure, properties, applications and health benefits of RS. © 2014 Society of Chemical Industry.

STUDENT AWARD FINALIST: Oxygen Pathways in Streamer Discharge for Transient Plasma Ignition

NASA Astrophysics Data System (ADS)

Pendleton, S. J.; Bowman, S.; Singleton, D.; Watrous, J.; Carter, C.; Lempert, W.; Gundersen, M. A.

2011-10-01

The use of streamers for the ignition of fuels, also known as transient plasma ignition (TPI), has been shown in a variety of engines to improve combustion through decreased ignition delay, increased lean burn capability and increased energy release relative to conventional spark ignition. The mechanisms behind these improvements, however, remain poorly understood. Temperature measurements by optical emission spectroscopy demonstrate that ignition by TPI is a nonthermal process, and thus is almost entirely dependent on the production and presence of electron impact-created active species in the discharge afterglow. Of particular interest are active oxygen species due to their relatively long lifetimes at high pressures and the pivotal role they play in combustion reactions. In order to elucidate the oxygen pathways, here we report the investigation of the temporal evolution of the populations of atomic oxygen and ozone by use of two-photon absorption laser induced fluorescence (TALIF) and UV absorption, respectively. Experimental results are presented and compared to kinetic modeling of the streamers. Future experiments are proposed to better understand the physics behind TPI. Supported by NSF, AFOSR, NumerEx-ONR, AFRL-WPAFB.

Kinetics of Spontaneous Bimetallization between Silver and Noble Metal Nanoparticles.

PubMed

Hirakawa, Kazutaka; Kaneko, Tetsuya; Toshima, Naoki

2018-06-05

A physical mixture of polymer-protected Ag nanoparticles and Rh, Pd, or Pt nanoparticles spontaneously forms Ag-core bimetallic nanoparticles. The formed nanoparticles were smaller than the parent Ag nanoparticles. In the initial process of this reaction, the surface plasmon absorption of Ag nanoparticles diminished and then almost ceased within one hour. Within several minutes, the decrease in Ag surface plasmon absorption could be analyzed by second-order reaction. This reaction was accelerated with an increase of temperature and the energy gap in the Fermi level between Ag and the other metals. The activation energy (E a ) of this reaction could be determined. An electron transfer reaction from Ag to other metal nanoparticles was proposed as the initial interaction between these metal nanoparticles because the Fermi level of Ag is relatively high, and the electron transfer is possible in terms of energy. The Marcus plot between the rate constant and the driving force, roughly estimated from the work function of metals, and the observed E a values reasonably explained the proposed electron transfer mechanism. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Laser Lightcraft Performance

NASA Technical Reports Server (NTRS)

Chen, Yen-Sen; Liu, Jiwen; Wei, Hong

2000-01-01

The purpose of this study is to establish the technical ground for modeling the physics of laser powered pulse detonation phenomenon. The principle of the laser power propulsion is that when high-powered laser is focused at a small area near the surface of a thruster, the intense energy causes the electrical breakdown of the working fluid (e.g. air) and forming high speed plasma (known as the inverse Bremsstrahlung, IB, effect). The intense heat and high pressure created in the plasma consequently causes the surrounding to heat up and expand until the thrust producing shock waves are formed. This complex process of gas ionization, increase in radiation absorption and the forming of plasma and shock waves will be investigated in the development of the present numerical model. In the first phase of this study, laser light focusing, radiation absorption and shock wave propagation over the entire pulsed cycle are modeled. The model geometry and test conditions of known benchmark experiments such as those in Myrabo's experiment will be employed in the numerical model validation simulations. The calculated performance data will be compared to the test data.

The Physical Nature of Polar Broad Absorption Line Quasars

NASA Technical Reports Server (NTRS)

Ghost, Kajal; Punsly, Brian

2007-01-01

It has been shown based on radio variability arguments that some BALQSOs (broad absorption line quasars) are viewed along the polar axis (o rthogonal to accretion disk) in the recent article of Zhou et a. Thes e arguments are based on the brightness temperature, T(sub b) exceedi ng 10(exp 12) K which leads to the well-known inverse Compton catastr ophe unless the radio jet is relativistic and is viewed along its axi s. In this letter, we expand the Zhou et al sample of polar BALQSOs u sing their techniques applied to SDSS DR5. In the process, we clarify a mistake in their calculation of brightness temperature. The expanded sample of high T(sub b) BALQSOS, has an inordinately large fraction of LoBALQSOs (low ionization BALQSOs). We consider this an important clue to understanding the nature of the polar BALQSOs. This is expec ted in the polar BALQSO analytical/numerical models of Punsly that pr edicted that LoBALQSOs occur when the line of sight is very close to the polar axis, where the outflow density is the highest.

Kinetics of leather dyeing pretreated with enzymes: role of acid protease.

PubMed

Kanth, Swarna Vinodh; Venba, Rajangam; Jayakumar, Gladstone Christopher; Chandrababu, Narasimhan Kannan

2009-04-01

In the present investigation, kinetics of dyeing involving pretreatment with acid protease has been presented. Application of acid protease in dyeing process resulted in increased absorption and diffusion of dye into the leather matrix. Enzyme treatment at 1% concentration, 60 min duration and 50 degrees C resulted in maximum of 98% dye exhaustion and increased absorption rate constants. The final exhaustion (C(infinity)) for the best fit of CI Acid Black 194 dye has been 98.5% with K and r2 values from the modified Cegarra-Puente isotherm as 0.1033 and 0.0631. CI Acid Black 194 being a 2:1 metal complex acid dye exhibited higher absorption rate than the acid dye CI Acid Black 210. A reduction in 50% activation energy calculated from Arrhenius equation has been observed in enzyme assisted dyeing process of both the dyes that substantiates enhanced dye absorption. The absorption rate constant calculated with modified Cegarra-Puente equation confirm higher rate constants and faster kinetics for enzyme assisted dyeing process. Enzyme treated leather exhibited richness of color and shade when compared with control. The present study substantiates the essential role of enzyme pretreatment as an eco-friendly leather dyeing process.

Methods for deacidizing gaseous mixtures by phase enhanced absorption

DOEpatents

Hu, Liang

2012-11-27

An improved process for deacidizing a gaseous mixture using phase enhanced gas-liquid absorption is described. The process utilizes a multiphasic absorbent that absorbs an acid gas at increased rate and leads to reduced overall energy costs for the deacidizing operation.

Performance of a biogas upgrading process based on alkali absorption with regeneration using air pollution control residues.

PubMed

Baciocchi, Renato; Carnevale, Ennio; Costa, Giulia; Gavasci, Renato; Lombardi, Lidia; Olivieri, Tommaso; Zanchi, Laura; Zingaretti, Daniela

2013-12-01

This work analyzes the performance of an innovative biogas upgrading method, Alkali absorption with Regeneration (AwR) that employs industrial residues and allows to permanently store the separated CO2. This process consists in a first stage in which CO2 is removed from the biogas by means of chemical absorption with KOH or NaOH solutions followed by a second stage in which the spent absorption solution is contacted with waste incineration Air Pollution Control (APC) residues. The latter reaction leads to the regeneration of the alkali reagent in the solution and to the precipitation of calcium carbonate and hence allows to reuse the regenerated solution in the absorption process and to permanently store the separated CO2 in solid form. In addition, the final solid product is characterized by an improved environmental behavior compared to the untreated residues. In this paper the results obtained by AwR tests carried out in purposely designed demonstrative units installed in a landfill site are presented and discussed with the aim of verifying the feasibility of this process at pilot-scale and of identifying the conditions that allow to achieve all of the goals targeted by the proposed treatment. Specifically, the CO2 removal efficiency achieved in the absorption stage, the yield of alkali regeneration and CO2 uptake resulting for the regeneration stage, as well as the leaching behavior of the solid product are analyzed as a function of the type and concentration of the alkali reagent employed for the absorption reaction. Copyright © 2013 Elsevier Ltd. All rights reserved.

Theoretical description of protein field effects on electronic excitations of biological chromophores.

PubMed

Varsano, Daniele; Caprasecca, Stefano; Coccia, Emanuele

2017-01-11

Photoinitiated phenomena play a crucial role in many living organisms. Plants, algae, and bacteria absorb sunlight to perform photosynthesis, and convert water and carbon dioxide into molecular oxygen and carbohydrates, thus forming the basis for life on Earth. The vision of vertebrates is accomplished in the eye by a protein called rhodopsin, which upon photon absorption performs an ultrafast isomerisation of the retinal chromophore, triggering the signal cascade. Many other biological functions start with the photoexcitation of a protein-embedded pigment, followed by complex processes comprising, for example, electron or excitation energy transfer in photosynthetic complexes. The optical properties of chromophores in living systems are strongly dependent on the interaction with the surrounding environment (nearby protein residues, membrane, water), and the complexity of such interplay is, in most cases, at the origin of the functional diversity of the photoactive proteins. The specific interactions with the environment often lead to a significant shift of the chromophore excitation energies, compared with their absorption in solution or gas phase. The investigation of the optical response of chromophores is generally not straightforward, from both experimental and theoretical standpoints; this is due to the difficulty in understanding diverse behaviours and effects, occurring at different scales, with a single technique. In particular, the role played by ab initio calculations in assisting and guiding experiments, as well as in understanding the physics of photoactive proteins, is fundamental. At the same time, owing to the large size of the systems, more approximate strategies which take into account the environmental effects on the absorption spectra are also of paramount importance. Here we review the recent advances in the first-principle description of electronic and optical properties of biological chromophores embedded in a protein environment. We show their applications on paradigmatic systems, such as the light-harvesting complexes, rhodopsin and green fluorescent protein, emphasising the theoretical frameworks which are of common use in solid state physics, and emerging as promising tools for biomolecular systems.

Toward a Prescription for Feedback from Quasar Outflows

NASA Astrophysics Data System (ADS)

Ganguly, Rajib; Bourjaily, M.; Munsell, J.; Brotherton, M. S.; Bhattacharjee, A.; Runnoe, J.; Charlton, J. C.; Eracleous, M.

2011-01-01

Models have shown that quasars are a crucial ingredient in the evolution of massive galaxies. Outflows play a key role in the story of quasars and their host galaxies, by helping regulate the accretion process, the star-formation rate and mass of the host galaxy (i.e., feedback). The prescription for modeling outflows as a contributor to feedback requires knowledge of the outflow velocity, distance, geometry, and column density. In particular, we need to understand how these depend on physical parameters and how much is determined stochastically (and with what distribution). For this purpose, we are examining a sample of 14000 z=1.7-2.0 quasars from the Sloan Digital Sky Survey. This redshift range permits the following from the SDSS spectra: (1) separation of objects that do and do not exhibit outflows; (2) classification/measurement of outflow properties (ionization, velocity, velocity width); and (3) estimates of the quasar black hole mass. To this, we are adding photometry from GALEX, 2MASS, and ROSAT in an effort to characterize more fully the quasar SEDs. ROSAT photometry provides estimates of the level of soft X-ray absorption, which helps regulate the velocity of outflows. GALEX photometry samples the extreme ultraviolet range where several high ionization species, that may be present in the outflows, absorb light. 2MASS photometry samples the rest-frame optical, where the effects of absorption and dust reddening are minimal, yield better estimates of the bolometric luminosity (hence, Eddington ratio). In this poster, we will present preliminary measurements of the amount of absorption in the soft X-ray and extreme ultraviolet bands as a function of both outflow properties and quasar physical properties. This material is based upon work supported by the National Aeronautics and Space Administration under Grant No. 09-ADP09-0016 issued through the Astrophysics Data Analysis Program.

Theoretical description of protein field effects on electronic excitations of biological chromophores

NASA Astrophysics Data System (ADS)

Varsano, Daniele; Caprasecca, Stefano; Coccia, Emanuele

2017-01-01

Photoinitiated phenomena play a crucial role in many living organisms. Plants, algae, and bacteria absorb sunlight to perform photosynthesis, and convert water and carbon dioxide into molecular oxygen and carbohydrates, thus forming the basis for life on Earth. The vision of vertebrates is accomplished in the eye by a protein called rhodopsin, which upon photon absorption performs an ultrafast isomerisation of the retinal chromophore, triggering the signal cascade. Many other biological functions start with the photoexcitation of a protein-embedded pigment, followed by complex processes comprising, for example, electron or excitation energy transfer in photosynthetic complexes. The optical properties of chromophores in living systems are strongly dependent on the interaction with the surrounding environment (nearby protein residues, membrane, water), and the complexity of such interplay is, in most cases, at the origin of the functional diversity of the photoactive proteins. The specific interactions with the environment often lead to a significant shift of the chromophore excitation energies, compared with their absorption in solution or gas phase. The investigation of the optical response of chromophores is generally not straightforward, from both experimental and theoretical standpoints; this is due to the difficulty in understanding diverse behaviours and effects, occurring at different scales, with a single technique. In particular, the role played by ab initio calculations in assisting and guiding experiments, as well as in understanding the physics of photoactive proteins, is fundamental. At the same time, owing to the large size of the systems, more approximate strategies which take into account the environmental effects on the absorption spectra are also of paramount importance. Here we review the recent advances in the first-principle description of electronic and optical properties of biological chromophores embedded in a protein environment. We show their applications on paradigmatic systems, such as the light-harvesting complexes, rhodopsin and green fluorescent protein, emphasising the theoretical frameworks which are of common use in solid state physics, and emerging as promising tools for biomolecular systems.

K- absorption on two nucleons and ppK- bound state search in the Σ0p final state

NASA Astrophysics Data System (ADS)

Vázquez Doce, O.; Fabbietti, L.; Cargnelli, M.; Curceanu, C.; Marton, J.; Piscicchia, K.; Scordo, A.; Sirghi, D.; Tucakovic, I.; Wycech, S.; Zmeskal, J.; Anastasi, A.; Curciarello, F.; Czerwinski, E.; Krzemien, W.; Mandaglio, G.; Martini, M.; Moskal, P.; Patera, V.; Pérez del Rio, E.; Silarski, M.

2016-07-01

We report the measurement of K- absorption processes in the Σ0p final state and the first exclusive measurement of the two nucleon absorption (2NA) with the KLOE detector. The 2NA process without further interactions is found to be 9% of the sum of all other contributing processes, including absorption on three and more nucleons or 2NA followed by final state interactions with the residual nucleons. We also determine the possible contribution of the ppK- bound state to the Σ0p final state. The yield of ppK- /Kstop- is found to be (0.044 ± 0.009stat-0.005+0.004 syst) ṡ10-2 but its statistical significance based on an F-test is only 1σ.

Polycyclic Aromatic Hydrocarbons

NASA Technical Reports Server (NTRS)

Salama, Farid

2010-01-01

Carbonaceous materials play an important role in space. Polycyclic Aromatic Hydrocarbons (PAHs) are a ubiquitous component of the carbonaceous materials. PAHs are the best-known candidates to account for the IR emission bands. They are also thought to be among the carriers of the diffuse interstellar absorption bands (DIBs). PAH ionization states reflect the ionization balance of the medium while PAH size, composition, and structure reflect the energetic and chemical history of the medium. A major challenge is to reproduce in the laboratory the physical conditions that exist in the emission and absorption interstellar zones. The harsh physical conditions of the ISM -low temperature, collisionless, strong UV radiation fields- are simulated in the laboratory by associating a molecular beam with an ionizing discharge to generate a cold plasma expansion. PAH ions and radicals are formed from the neutral precursors in an isolated environment at low temperature and probed with high-sensitivity cavity ringdown spectroscopy in the NUV-NIR range. Carbon nanoparticles are also formed during the short residence time of the precursors in the plasma and are characterized with time-offlight mass spectrometry. These experiments provide unique information on the spectra of large carbonaceous molecules and ions in the gas phase that can now be directly compared to interstellar and circumstellar observations (IR emission bands, DIBs, extinction curve). These findings also hold great potential for understanding the formation process of interstellar carbonaceous grains. We will review recent progress in the experimental and theoretical studies of PAHs, compare the laboratory data with astronomical observations and discuss the global implications.

Aerosol Complexity and Implications for Predictability and Short-Term Forecasting

NASA Technical Reports Server (NTRS)

Colarco, Peter

2016-01-01

There are clear NWP and climate impacts from including aerosol radiative and cloud interactions. Changes in dynamics and cloud fields affect aerosol lifecycle, plume height, long-range transport, overall forcing of the climate system, etc. Inclusion of aerosols in NWP systems has benefit to surface field biases (e.g., T2m, U10m). Including aerosol affects has impact on analysis increments and can have statistically significant impacts on, e.g., tropical cyclogenesis. Above points are made especially with respect to aerosol radiative interactions, but aerosol-cloud interaction is a bigger signal on the global system. Many of these impacts are realized even in models with relatively simple (bulk) aerosol schemes (approx.10 -20 tracers). Simple schemes though imply simple representation of aerosol absorption and importantly for aerosol-cloud interaction particle-size distribution. Even so, more complex schemes exhibit a lot of diversity between different models, with issues such as size selection both for emitted particles and for modes. Prospects for complex sectional schemes to tune modal (and even bulk) schemes toward better selection of size representation. I think this is a ripe topic for more research -Systematic documentation of benefits of no vs. climatological vs. interactive (direct and then direct+indirect) aerosols. Document aerosol impact on analysis increments, inclusion in NWP data assimilation operator -Further refinement of baseline assumptions in model design (e.g., absorption, particle size distribution). Did not get into model resolution and interplay of other physical processes with aerosols (e.g., moist physics, obviously important), chemistry

Photo-induced intersubband absorption in {Si}/{SiGe} quantum wells

NASA Astrophysics Data System (ADS)

Boucaud, P.; Gao, L.; Visocekas, F.; Moussa, Z.; Lourtioz, J.-M.; Julien, F. H.; Sagnes, I.; Campidelli, Y.; Badoz, P.-A.; Vagos, P.

1995-12-01

We have investigated photo-induced intersubband absorption in the valence band of {Si}/{SiGe} quantum wells. Carriers are optically generated in the quantum wells using an argon ion laser. The resulting infrared absorption is probed with a step-scan Fourier transform infrared spectrometer. The photo-induced infrared absorption in SiGe quantum wells is dominated by two contributions: the free carrier absorption, which is similar to bulk absorption in a uniformly doped SiGe layer, and the valence subband absorption in the quantum wells. Both p- and s-polarized intersubband absorptions are measured. We have observed that the photo-induced intersubband absorption in doped samples is shifted to lower energy as compared to direct intersubband absorption. This absorption process is attributed to carriers away from the Brillouin zone center. We show that the photo-induced technique is appropriate to study valence band mixing effects and their influence on intersubband absorption.

Axisymmetric flow of Casson fluid by a swirling cylinder

NASA Astrophysics Data System (ADS)

Javed, Muhammad Faisal; Khan, Muhammad Imran; Khan, Niaz Bahadur; Muhammad, Riaz; Rehman, Muftooh Ur; Khan, Sajjad Wali; Khan, Tufail A.

2018-06-01

The present communication aims to investigate the influence of heat generation/absorption on axisymmetric Casson liquid flow over a stretched cylinder. Flow is caused due to torsional motion of cylinder. The governing physical problem is modelled and transferred into set of coupled nonlinear ordinary differential equations. These equations are solved numerically using built-in-Shooting method. Influence of sundry variables on the swirling velocity, temperature, coefficient of skin friction and heat transfer rate are computed and analyzed in a physical manner. Magnitude of axial skin friction is enhances for larger Reynold number and magnetic parameter while local Nusselt number decays with the enhancement of Casson parameter, heat generation/absorption and magnetic parameter. Comparison with already existing results is also given in the limiting case.

Probing excitons in transition metal dichalcogenides by Drude-like exciton intraband absorption.

PubMed

Zhao, Siqi; He, Dawei; He, Jiaqi; Zhang, Xinwu; Yi, Lixin; Wang, Yongsheng; Zhao, Hui

2018-05-24

Understanding excitonic dynamics in two-dimensional semiconducting transition metal dichalcogenides is important for developing their optoelectronic applications. Recently, transient absorption techniques based on resonant excitonic absorption have been used to study various aspects of excitonic dynamics in these materials. The transient absorption in such measurements originates from phase-space state filling, bandgap renormalization, or screening effects. Here we report a new method to probe excitonic dynamics based on exciton intraband absorption. In this Drude-like process, probe photons are absorbed by excitons in their intraband excitation to higher energy states, causing a transient absorption signal. Although the magnitude of the transient absorption is lower than that of the resonant techniques, the new method is less restrictive on the selection of probe wavelength, has a larger linear range, and can provide complementary information on photocarrier dynamics. Using the WS2 monolayer and bulk samples as examples, we show that the new method can probe exciton-exciton annihilation at high densities and reveal exciton formation processes. We also found that the exciton intraband absorption cross section of the WS2 monolayer is on the order of 10-18 cm2.

Reducing LANDSAT data to parameters with physical significance and signature extension: A view of LANDSAT capabilities

NASA Technical Reports Server (NTRS)

Salmon-Drexler, B. C.

1977-01-01

The premise is the LANDSAT is capable of sensing only a few physical parameters. Much of the contrast provided in LANDSAT data is provided by differences in vegetation cover. Although dominant, vegetation is not the only physical parameter that can be detected with LANDSAT; a ratio of MSS Channel 5 to MSS Channel 4 (R5,4), two visible channels, separates materials by color hue. Additional information is attained by the addition of MSS channels 5 and 4 to approximate brightness, permitting separation of materials by color value. Other spectral combinations may provide correlations with these physical parameters or new ones. An iron absorption in the infrared can also be recognized in LANDSAT data when iron content is present in sufficient percentages, Although by color, limonite-rich soils are distinctive as bright yellow, they are not unique in the R5,4. A fairly strong iron absorption is present in the infrared band MSS Channel 7 for these soils, although the wideband configuration of LANDSAT is not optimal for its enhancement and the effects of vegetation often obscure it.

Surface tension mediated conversion of light to work

DOEpatents

Okawa, David; Pastine, Stefan J; Zettl, Alexander K; Frechet, Jean M. J

2014-12-02

Disclosed are a method and apparatus for converting light energy to mechanical energy by modification of surface tension on a supporting fluid. The apparatus comprises an object which may be formed as a composite object comprising a support matrix and a highly light absorptive material. The support matrix may comprise a silicon polymer. The highly light absorptive material may comprise vertically aligned carbon nanotubes (VANTs) embedded in the support matrix. The composite object is supported on a fluid. By exposing the highly light absorptive material to light, heat is generated, which changes the surface tension of the composite object, causing it to move physically within the fluid.

Traveling-wave photodetector

DOEpatents

Hietala, V.M.; Vawter, G.A.

1993-12-14

The traveling-wave photodetector of the present invention combines an absorptive optical waveguide and an electrical transmission line, in which optical absorption in the waveguide results in a photocurrent at the electrodes of the electrical transmission line. The optical waveguide and electrical transmission line of the electrically distributed traveling-wave photodetector are designed to achieve matched velocities between the light in the optical waveguide and electrical signal generated on the transmission line. This velocity synchronization provides the traveling-wave photodetector with a large electrical bandwidth and a high quantum efficiency, because of the effective extended volume for optical absorption. The traveling-wave photodetector also provides large power dissipation, because of its large physical size. 4 figures.

Traveling-wave photodetector

DOEpatents

Hietala, Vincent M.; Vawter, Gregory A.

1993-01-01

The traveling-wave photodetector of the present invention combines an absorptive optical waveguide and an electrical transmission line, in which optical absorption in the waveguide results in a photocurrent at the electrodes of the electrical transmission line. The optical waveguide and electrical transmission line of the electrically distributed traveling-wave photodetector are designed to achieve matched velocities between the light in the optical waveguide and electrical signal generated on the transmission line. This velocity synchronization provides the traveling-wave photodetector with a large electrical bandwidth and a high quantum efficiency, because of the effective extended volume for optical absorption. The traveling-wave photodetector also provides large power dissipation, because of its large physical size.

Absorption performance for CO2 capture process using MDEA-AMP aqueous solution

NASA Astrophysics Data System (ADS)

Liu, Gang; Kou, Liqing; Li, Chao

2017-03-01

The absorption capacity and the absorption rate of CO2 in 2-amino-2-methyl-1-propanol (AMP)-N-methyldiethanolamine (MDEA) aqueous solution were measured. The temperatures ranged from 303.2K to 323.2K. The mass fractions of AMP and MDEA respectively ranged from 0 to 0.03 and 0.2 to 0.3. The influence of temperature and w AMP on the absorption capacity and absorption rate of CO2 was illustrated.

Parameter extraction using global particle swarm optimization approach and the influence of polymer processing temperature on the solar cell parameters

NASA Astrophysics Data System (ADS)

Kumar, S.; Singh, A.; Dhar, A.

2017-08-01

The accurate estimation of the photovoltaic parameters is fundamental to gain an insight of the physical processes occurring inside a photovoltaic device and thereby to optimize its design, fabrication processes, and quality. A simulative approach of accurately determining the device parameters is crucial for cell array and module simulation when applied in practical on-field applications. In this work, we have developed a global particle swarm optimization (GPSO) approach to estimate the different solar cell parameters viz., ideality factor (η), short circuit current (Isc), open circuit voltage (Voc), shunt resistant (Rsh), and series resistance (Rs) with wide a search range of over ±100 % for each model parameter. After validating the accurateness and global search power of the proposed approach with synthetic and noisy data, we applied the technique to the extract the PV parameters of ZnO/PCDTBT based hybrid solar cells (HSCs) prepared under different annealing conditions. Further, we examine the variation of extracted model parameters to unveil the physical processes occurring when different annealing temperatures are employed during the device fabrication and establish the role of improved charge transport in polymer films from independent FET measurements. The evolution of surface morphology, optical absorption, and chemical compositional behaviour of PCDTBT co-polymer films as a function of processing temperature has also been captured in the study and correlated with the findings from the PV parameters extracted using GPSO approach.

Thermal emission and absorption of radiation in finite inverted-opal photonic crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Florescu, Marian; Stimpson, Andrew J.; Lee, Hwang

We study theoretically the optical properties of a finite inverted-opal photonic crystal. The light-matter interaction is strongly affected by the presence of the three-dimensional photonic crystal and the alterations of the light emission and absorption processes can be used to suppress or enhance the thermal emissivity and absorptivity of the dielectric structure. We investigate the influence of the absorption present in the system on the relevant band edge frequencies that control the optical response of the photonic crystal. Our study reveals that the absorption processes cause spectral broadening and shifting of the band edge optical resonances, and determine a strongmore » reduction of the photonic band gap spectral range. Using the angular and spectral dependence of the band edge frequencies for stop bands along different directions, we argue that by matching the blackbody emission spectrum peak with a prescribed maximum of the absorption coefficient, it is possible to achieve an angle-sensitive enhancement of the thermal emission/absorption of radiation. This result opens a way to realize a frequency-sensitive and angle-sensitive photonic crystal absorbers/emitters.« less

Process and Material Design for Micro-Encapsulated Ionic Liquids in Post-Combustion CO 2 Capture

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, Bo; Brennecke, Joan F; McCready, Mark

Aprotic Heterocyclic Anion (AHA) Ionic Liquids (ILs) have been identified as promising new solvents for post-combustion carbon capture due to their high CO 2 uptake and the high tenability 1,2 of their binding energy with CO 2. Some of these compounds change phase (solid to liquid) on absorption of CO 2; these Phase Change ILs (PCILs)3 offer the additional advantage that part of the heat needed to desorb the CO2 from the absorbent is provided by the heat of fusion as the PCIL solidifies upon release of CO 2. However, the relatively high viscosity of AHA ILs and the occurrencemore » of a phase change in PCILs present challenges for conventional absorption equipment. To overcome these challenges we are pursuing the use of new technology to micro-encapsulate the AHA ILs and PCILs. Our partners at Lawrence Livermore National Laboratory have successfully demonstrated this technology in the application of post-combustion carbon capture with sodium and potassium carbonate solutions,4 and have recently shown the feasibility of micro-encapsulation of an AHA IL for carbon capture.5 The large effective surface area and high CO 2 permeability of the micro-capsules is expected to offset the drawback of the high IL viscosity and to provide for a more efficient and cost-effective mass transfer operation involving AHA ILs and PCILs. These opportunities, however, present us with both process and materials design questions. For example, what is the target CO 2 absorption strength (enthalpy of chemical absorption) for the tunable AHA IL? What is the target for micro-capsule diameter in order to obtain a high mass transfer rate and good fluidization performance? What are the appropriate temperatures and pressures for the absorber and stripper? In order to address these and other questions, we have developed a rate-based model of a post-combustion CO 2 capture process using micro-encapsulated ILs. As a performance baseline, we have also developed a rate-based model of a standard packed bed absorber using an un-encapsulated AHA IL absorbent. Using such models we can determine optimal CO 2 capture performance and investigate the sensitivity of the optimum with respect to the key thermo-physical and transport properties of the IL (e.g., CO 2 binding energy, viscosity, etc.) and the micro-capsules (e.g. diameter, CO 2 permeability, etc.). Results of these process and material design studies will be presented, and the performance of this novel micro-encapsulation technology will be assessed.« less

Interaction of high-intensity laser radiation with metals.

NASA Technical Reports Server (NTRS)

Linlor, W. I.

1971-01-01

The interaction is characterized by the production of plasma, within which the primary absorption occurs. Absorption of laser radiation by a plasma may occur by several processes. The absorption process called 'inverse bremsstrahlung' is discussed. The interaction of a laser beam with the plasma produced from a thick metal target was studied. The results of the measurements of the ion kinetic energies are presented in a graph. In addition to measurements with thick targets, information was also obtained with a thin foil of gold.

High colored dissolved organic matter (CDOM) absorption in surface waters of the central-eastern Arctic Ocean: Implications for biogeochemistry and ocean color algorithms

PubMed Central

Rabe, Benjamin; Peeken, Ilka; Bracher, Astrid

2018-01-01

As consequences of global warming sea-ice shrinking, permafrost thawing and changes in fresh water and terrestrial material export have already been reported in the Arctic environment. These processes impact light penetration and primary production. To reach a better understanding of the current status and to provide accurate forecasts Arctic biogeochemical and physical parameters need to be extensively monitored. In this sense, bio-optical properties are useful to be measured due to the applicability of optical instrumentation to autonomous platforms, including satellites. This study characterizes the non-water absorbers and their coupling to hydrographic conditions in the poorly sampled surface waters of the central and eastern Arctic Ocean. Over the entire sampled area colored dissolved organic matter (CDOM) dominates the light absorption in surface waters. The distribution of CDOM, phytoplankton and non-algal particles absorption reproduces the hydrographic variability in this region of the Arctic Ocean which suggests a subdivision into five major bio-optical provinces: Laptev Sea Shelf, Laptev Sea, Central Arctic/Transpolar Drift, Beaufort Gyre and Eurasian/Nansen Basin. Evaluating ocean color algorithms commonly applied in the Arctic Ocean shows that global and regionally tuned empirical algorithms provide poor chlorophyll-a (Chl-a) estimates. The semi-analytical algorithms Generalized Inherent Optical Property model (GIOP) and Garver-Siegel-Maritorena (GSM), on the other hand, provide robust estimates of Chl-a and absorption of colored matter. Applying GSM with modifications proposed for the western Arctic Ocean produced reliable information on the absorption by colored matter, and specifically by CDOM. These findings highlight that only semi-analytical ocean color algorithms are able to identify with low uncertainty the distribution of the different optical water constituents in these high CDOM absorbing waters. In addition, a clustering of the Arctic Ocean into bio-optical provinces will help to develop and then select province-specific ocean color algorithms. PMID:29304182

High colored dissolved organic matter (CDOM) absorption in surface waters of the central-eastern Arctic Ocean: Implications for biogeochemistry and ocean color algorithms.

PubMed

Gonçalves-Araujo, Rafael; Rabe, Benjamin; Peeken, Ilka; Bracher, Astrid

2018-01-01

As consequences of global warming sea-ice shrinking, permafrost thawing and changes in fresh water and terrestrial material export have already been reported in the Arctic environment. These processes impact light penetration and primary production. To reach a better understanding of the current status and to provide accurate forecasts Arctic biogeochemical and physical parameters need to be extensively monitored. In this sense, bio-optical properties are useful to be measured due to the applicability of optical instrumentation to autonomous platforms, including satellites. This study characterizes the non-water absorbers and their coupling to hydrographic conditions in the poorly sampled surface waters of the central and eastern Arctic Ocean. Over the entire sampled area colored dissolved organic matter (CDOM) dominates the light absorption in surface waters. The distribution of CDOM, phytoplankton and non-algal particles absorption reproduces the hydrographic variability in this region of the Arctic Ocean which suggests a subdivision into five major bio-optical provinces: Laptev Sea Shelf, Laptev Sea, Central Arctic/Transpolar Drift, Beaufort Gyre and Eurasian/Nansen Basin. Evaluating ocean color algorithms commonly applied in the Arctic Ocean shows that global and regionally tuned empirical algorithms provide poor chlorophyll-a (Chl-a) estimates. The semi-analytical algorithms Generalized Inherent Optical Property model (GIOP) and Garver-Siegel-Maritorena (GSM), on the other hand, provide robust estimates of Chl-a and absorption of colored matter. Applying GSM with modifications proposed for the western Arctic Ocean produced reliable information on the absorption by colored matter, and specifically by CDOM. These findings highlight that only semi-analytical ocean color algorithms are able to identify with low uncertainty the distribution of the different optical water constituents in these high CDOM absorbing waters. In addition, a clustering of the Arctic Ocean into bio-optical provinces will help to develop and then select province-specific ocean color algorithms.

A frequency quantum interpretation of the surface renewal model of mass transfer

PubMed Central

Mondal, Chanchal

2017-01-01

The surface of a turbulent liquid is visualized as consisting of a large number of chaotic eddies or liquid elements. Assuming that surface elements of a particular age have renewal frequencies that are integral multiples of a fundamental frequency quantum, and further assuming that the renewal frequency distribution is of the Boltzmann type, performing a population balance for these elements leads to the Danckwerts surface age distribution. The basic quantum is what has been traditionally called the rate of surface renewal. The Higbie surface age distribution follows if the renewal frequency distribution of such elements is assumed to be continuous. Four age distributions, which reflect different start-up conditions of the absorption process, are then used to analyse transient physical gas absorption into a large volume of liquid, assuming negligible gas-side mass-transfer resistance. The first two are different versions of the Danckwerts model, the third one is based on the uniform and Higbie distributions, while the fourth one is a mixed distribution. For the four cases, theoretical expressions are derived for the rates of gas absorption and dissolved-gas transfer to the bulk liquid. Under transient conditions, these two rates are not equal and have an inverse relationship. However, with the progress of absorption towards steady state, they approach one another. Assuming steady-state conditions, the conventional one-parameter Danckwerts age distribution is generalized to a two-parameter age distribution. Like the two-parameter logarithmic normal distribution, this distribution can also capture the bell-shaped nature of the distribution of the ages of surface elements observed experimentally in air–sea gas and heat exchange. Estimates of the liquid-side mass-transfer coefficient made using these two distributions for the absorption of hydrogen and oxygen in water are very close to one another and are comparable to experimental values reported in the literature. PMID:28791137

Birge-Sponer Estimation of the C-H Bond Dissociation Energy in Chloroform Using Infrared, Near-Infrared, and Visible Absorption Spectroscopy: An Experiment in Physical Chemistry

ERIC Educational Resources Information Center

Myrick, M. L.; Greer, A. E.; Nieuwland, A. A.; Priore, R. J.; Scaffidi, J.; Andreatta, Danielle; Colavita, Paula

2008-01-01

The fundamental and overtone vibrational absorption spectroscopy of the C-H unit in CHCl[subscript 3] is measured for transitions from the v = 0 energy level to v = 1 through v = 5 energy levels. The energies of the transitions exhibit a linearly-decreasing spacing between adjacent vibrational levels as the vibrational quantum number increases.…

Modeling of thermoplastic composites laser welding - A ray tracing method associated to thermal simulation

NASA Astrophysics Data System (ADS)

Dauphin, Myriam; Cosson, Benoit

2016-10-01

The importance of the absorption phenomenon occurring into the semi-transparent substrate of reinforced fiber thermoplastic, during the Laser Transmission Welding process (LTW), was examined. A (3D) transient thermal model of LTW was developed. First, the energy distribution coming from the laser irradiation was assessed. Ray tracing techniques allowed us to deal with both absorption and a strong light-scattering caused by the heterogeneity of composite. Then, the energy balance equation was solved in order to study the heating stage. This paper proposes a comparison of the welding area obtained with a model for which absorption was neglected and a second model where absorption was considered. The interest to consider absorption was shown for process optimization purposes and for the use of reinforced composites colored or filled with additives.

Development of a carbonate absorption-based process for post-combustion CO2 capture: The role of biocatalyst to promote CO2 absorption rate

USGS Publications Warehouse

Lu, Y.; Ye, X.; Zhang, Z.; Khodayari, A.; Djukadi, T.

2011-01-01

An Integrated Vacuum Carbonate Absorption Process (IVCAP) for post-combustion carbon dioxide (CO2) capture is described. IVCAP employs potassium carbonate (PC) as a solvent, uses waste or low quality steam from the power plant for CO2 stripping, and employs a biocatalyst, carbonic anhydrase (CA) enzyme, for promoting the CO2 absorption into PC solution. A series of experiments were performed to evaluate the activity of CA enzyme mixed in PC solutions in a stirred tank reactor system under various temperatures, CA dosages, CO2 loadings, CO2 partial pressures, and the presence of major flue gas contaminants. It was demonstrated that CA enzyme is an effective biocatalyst for CO2 absorption under IVCAP conditions. ?? 2011 Published by Elsevier Ltd.

Effect of size and indium-composition on linear and nonlinear optical absorption of InGaN/GaN lens-shaped quantum dot

NASA Astrophysics Data System (ADS)

Ahmed, S. Jbara; Zulkafli, Othaman; M, A. Saeed

2016-05-01

Based on the Schrödinger equation for envelope function in the effective mass approximation, linear and nonlinear optical absorption coefficients in a multi-subband lens quantum dot are investigated. The effects of quantum dot size on the interband and intraband transitions energy are also analyzed. The finite element method is used to calculate the eigenvalues and eigenfunctions. Strain and In-mole-fraction effects are also studied, and the results reveal that with the decrease of the In-mole fraction, the amplitudes of linear and nonlinear absorption coefficients increase. The present computed results show that the absorption coefficients of transitions between the first excited states are stronger than those of the ground states. In addition, it has been found that the quantum dot size affects the amplitudes and peak positions of linear and nonlinear absorption coefficients while the incident optical intensity strongly affects the nonlinear absorption coefficients. Project supported by the Ministry of Higher Education and Scientific Research in Iraq, Ibnu Sina Institute and Physics Department of Universiti Teknologi Malaysia (UTM RUG Vote No. 06-H14).

Oscillations of absorption of a probe picosecond light pulse caused by its interaction with stimulated picosecond emission of GaAs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ageeva, N. N.; Bronevoi, I. L., E-mail: bil@cplire.ru; Zabegaev, D. N.

2015-04-15

The self-modulation of absorption of a picosecond light pulse was observed earlier [1] in a thin (∼1-μm thick) GaAs layer pumped by a high-power picosecond pulse. Analysis of the characteristics of this self-modulation predicted [5] that the dependences of the probe pulse absorption on the pump pulse energy and picosecond delay between pump and probe pulses should be self-modulated by oscillations. Such self-modulation was experimentally observed in this work. Under certain conditions, absorption oscillations proved to be a function of part of the energy of picosecond stimulated emission of GaAs lying above a certain threshold in the region where themore » emission front overlapped the probe pulse front. Absorption oscillations are similar to self-modulation of the GaAs emission characteristics observed earlier [4]. This suggests that the self-modulation of absorption and emission is determined by the same type of interaction of light pulses in the active medium, the physical mechanism of which has yet to be determined.« less

On the correlation of absorption cross-section with plasmonic color generation.

PubMed

Rezaei, Soroosh Daqiqeh; Ho, Jinfa; Ng, Ray Jia Hong; Ramakrishna, Seeram; Yang, Joel K W

2017-10-30

Through numerical simulations, we investigate the correlation between the absorption cross-section and the color saturation of plasmonic nanostructures of varying density. Understanding this correlation, enables the prediction of an optimal nanostructure separation, or combinations of different nanostructure sizes for plasmonic color printing applications. Here, we use metal-insulator-metal (MIM) aluminum nanostructures that support gap-plasmons. Large absorption cross-sections were observed that exceed twelve times the physical cross-section of the nanostructure disks. We derive a set of equations to determine the optimal separation for a periodic array using the absorption cross-section of an individual structure to realize saturated colors. Using the optimum pitch and enabled by the large absorption cross-sections of our structures, we employ color mixing strategies to realize a wider color gamut. The simulated color gamut exceeds the sRGB gamut for some colors, and includes dark tones. Color mixing using structures with large absorption cross-sections is a practical approach to generate a broad range of colors, in comparison to fabricating structures with continuously varying sizes.

Absorption coefficients of silicon: A theoretical treatment

NASA Astrophysics Data System (ADS)

Tsai, Chin-Yi

2018-05-01

A theoretical model with explicit formulas for calculating the optical absorption and gain coefficients of silicon is presented. It incorporates direct and indirect interband transitions and considers the effects of occupied/unoccupied carrier states. The indirect interband transition is calculated from the second-order time-independent perturbation theory of quantum mechanics by incorporating all eight possible routes of absorption or emission of photons and phonons. Absorption coefficients of silicon are calculated from these formulas. The agreements and discrepancies among the calculated results, the Rajkanan-Singh-Shewchun (RSS) formula, and Green's data are investigated and discussed. For example, the RSS formula tends to overestimate the contributions of indirect transitions for cases with high photon energy. The results show that the state occupied/unoccupied effect is almost negligible for silicon absorption coefficients up to the onset of the optical gain condition where the energy separation of Quasi-Femi levels between electrons and holes is larger than the band-gap energy. The usefulness of using the physics-based formulas, rather than semi-empirical fitting ones, for absorption coefficients in theoretical studies of photovoltaic devices is also discussed.

Amino acid utilization and body composition of growing pigs fed processed soybean meal or rapeseed meal with or without amino acid supplementation.

PubMed

Hulshof, T G; van der Poel, A F B; Hendriks, W H; Bikker, P

2017-07-01

Feed ingredients used in swine diets are often processed to improve nutritional value. However, (over-)processing may result in chemical reactions with amino acids (AAs) that decrease their ileal digestibility. This study aimed to determine effects of (over-)processing of soybean meal (SBM) and rapeseed meal (RSM) on post-absorptive utilization of ileal digestible AAs for retention and on body AA composition of growing pigs. Soybean meal and RSM were processed by secondary toasting in the presence of lignosulfonate to obtain processed soybean meal (pSBM) and processed rapeseed meal (pRSM). Four diets contained SBM, pSBM, RSM or pRSM as sole protein source. Two additional diets contained pSBM or pRSM and were supplemented with crystalline AA to similar standardized ileal digestible (SID) AA level as the SBM or RSM diet. These diets were used to verify that processing affected AA retention by affecting ileal AA digestibility rather than post-absorptive AA utilization. The SID AA levels of the protein sources were determined in a previous study. In total, 59 pigs were used (initial BW of 15.6±0.7 kg) of which five were used to determine initial body composition at the start of the experiment. In total, 54 pigs were fed one of six experimental diets and were slaughtered at a BW of 40 kg. The organ fraction (i.e. empty organs plus blood) and carcass were analyzed separately for N and AA content. Post-absorptive AA utilization was calculated from AA retention and SID AA intake. An interaction between diet type, comprising effects of processing and supplementing crystalline AA, and protein source was observed for CP content in the organ fraction, carcass and empty body and for nutrient retention. Processing reduced CP content and nutrient retention more for SBM than for RSM. Moreover, processing reduced (P<0.001) the lysine content in the organ fraction for both protein sources. Supplementing crystalline AA ameliorated the effect of processing on these variables. Thus, the data indicated that processing affected retention by reducing digestibility. Correcting AA retention for SID AA intake was, therefore, expected to result in similar post-absorptive AA utilization which was observed for the RSM diets. However, post-absorptive AA utilization was lower for the pSBM diet than for the SBM diet which might be related to an imbalanced post-absorptive AA supply. In conclusion, processing negatively affected nutrient retention for both protein sources and post-absorptive utilization of SID AA for retention for SBM. Effects of processing were compensated by supplementing crystalline AA.

Light Absorption in Arctic Sea Ice - Black Carbon vs Chlorophyll

NASA Astrophysics Data System (ADS)

Ogunro, O. O.; Wingenter, O. W.; Elliott, S.; Hunke, E. C.; Flanner, M.; Wang, H.; Dubey, M. K.; Jeffery, N.

2015-12-01

The fingerprint of climate change is more obvious in the Arctic than any other place on Earth. This is not only because the surface temperature there has increased at twice the rate of global mean temperature but also because Arctic sea ice extent has reached a record low of 49% reduction relative to the 1979-2000 climatology. Radiation absorption through black carbon (BC) deposited on Arctic snow and sea ice surface is one of the major hypothesized contributors to the decline. However, we note that chlorophyll-a absorption owing to increasing biology activity in this region could be a major competitor during boreal spring. Modeling of sea-ice physical and biological processes together with experiments and field observations promise rapid progress in the quality of Arctic ice predictions. Here we develop a dynamic ice system module to investigate discrete absorption of both BC and chlorophyll in the Arctic, using BC deposition fields from version 5 of Community Atmosphere Model (CAM5) and vertically distributed layers of chlorophyll concentrations from Sea Ice Model (CICE). To this point, our black carbon mixing ratios compare well with available in situ data. Both results are in the same order of magnitude. Estimates from our calculations show that sea ice and snow around the Canadian Arctic Archipelago and Baffin Bay has the least black carbon absorption while values at the ice-ocean perimeter in the region of the Barents Sea peak significantly. With regard to pigment concentrations, high amounts of chlorophyll are produced in Arctic sea ice by the bottom microbial community, and also within the columnar pack wherever substantial biological activity takes place in the presence of moderate light. We show that the percentage of photons absorbed by chlorophyll in the spring is comparable to the amount attributed to BC, especially in areas where the total deposition rates are decreasing with time on interannual timescale. We expect a continuous increase in chlorophyll absorption as the biological activity becomes stronger in thin ice toward the center of the Arctic basin. Alternatively, a shift in relative importance could occur as total BC mixing ratios are reduced because of environmental advocacy.

Detecting Isotopic Signatures and Measuring Isotopic Ratios on Solid Icy Surfaces:Implications for Origin and Evolution

NASA Astrophysics Data System (ADS)

Clark, R. N.; Brown, R. H.; Swayze, G. A.; Cruikshank, D. P.

2017-12-01

Infrared spectroscopy has long been used to detect isotopes in planetaryatmospheres and in the galaxy. Given sufficient spectral resolution,or large enough changes in mass, isotopes are also detectable in solids.Gas absorption lines can be quite narrow, but in some solids, e.g. H2Oice, absorptions are very broad with little to no fine structure. H2O icehas broad absorptions due to its orientationally disordered structure butmany ices, minerals, and other compounds display sufficiently narrowabsorptions to enable detection of isotopes with small mass changes atmoderate spectral resolution.D2O ice and HDO ice also show orientationally-disordered spectra withvery broad absorption bands. But as deuterium decreases to low levelsdeuterium apparently goes into ordered sites in the H2O ice structure,producing narrow absorptions and shifting to longer wavelengths.Trace D2O condensed on basalt at 80 Kelvin shows an O-D stretch at 4.0microns, but at D/H 0.1 or less in H2O ice, the D-O stretch occursnear 4.13 microns with a width in reflectance decreasing to 0.027 micronas D/H decreases. The narrow D-O stretch absorption shows an absorptioncoefficient of 80,000 cm^-1 enabling detection below Vienna Standard MeanOcean Water (VSMOW) with achievable S/N in the lab and from spacecraft.Isotopes of carbon have been detected in CO2 on Saturn's satelliteswith 16 nm FWHM using the VIMS instrument on the Cassini spacecraft.Deuterium has been detected at close to terrestrial levels in Saturn'srings and on Rhea, and an apparent enhancement on Phoebe using VIMSdata. The ocean world Enceladus is currently being analyzed. We alsodetect an enhancement in 13C on Phoebe, but not on Iapetus or Rhea,consistent with the suggestion from previous studies that suggest Phoebe'sorigin might be external to the Saturn system. The MISE instrumenton the Europa Clipper mission has the capability to detect deuteriumand carbon isotopes in the Jupiter system. The higher temperaturesin the Jupiter system may result in more fractionation, depending upona given isotope and the physical processes involved, potentially withimplications for origin and evolution.

The Law of Entropy Increase - A Lab Experiment

NASA Astrophysics Data System (ADS)

Dittrich, William; Drosd, Robert; Minkin, Leonid; Shapovalov, Alexander S.

2016-09-01

The second law of thermodynamics has various formulations. There is the "Clausius formulation," which can be stated in a very intuitive way: "No process is possible whose sole result is the transfer of heat from a cooler to a hotter body." There is also the "Kelvin-Plank principle," which states that "no cyclic process exists whose sole result is the absorption of heat from a reservoir and the conversion of all this heat into work" [emphasis added] (since this would require perfect energy conversion efficiency). Both these statements can be presented to physics students in a conceptual manner, and students' "everyday" experiences will support either statement of the second law of thermodynamics. However, when the second law of thermodynamics is expressed using the concept of entropy (ΔS ≥ 0, for a closed system), most first-year physics students lack any direct experimental experience with this parameter. This paper describes a calculation of the increase in entropy that can be performed while completing three traditional thermodynamics experiments. These simple and quick calculations help students become familiar and comfortable with the concept of entropy. This paper is complementary to prior work where classroom activities were developed to provide insight into the statistical nature of entropy.

Supersaturation and crystallization: non-equilibrium dynamics of amorphous solid dispersions for oral drug delivery.

PubMed

Kawakami, Kohsaku

2017-06-01

Amorphous solid dispersions (ASDs) are one of the key formulation technologies that aid the development of poorly soluble candidates. However, their dynamic behaviors, including dissolution and crystallization processes, are still full of mystery. Further understanding of these processes should enhance their wider use. Areas covered: The first part of this review describes the current understanding of the dissolution of ASDs, where phase separation behavior is frequently involved and attempts to develop appropriate dissolution tests to achieve an in vitro-in vivo correlation are examined. The second part of this review discusses crystallization of the drug molecule with the eventual aim of establishing an accelerated testing protocol for predicting its physical stability. Expert opinion: The phase separation behavior from the supersaturated state during the dissolution test must be understood, and its relevance to the oral absorption behavior needs to be clarified. Research efforts should focus on the differences between the phase behavior in in vitro and in vivo situations. Initiation time of the crystallization was shown to be predicted only from storage and glass transition temperatures. This finding should encourage the establishment of testing protocol of the physical stability of ASDs.

Focusing Light Beams To Improve Atomic-Vapor Optical Buffers

NASA Technical Reports Server (NTRS)

Strekalov, Dmitry; Matsko, Andrey; Savchenkov, Anatoliy

2010-01-01

Specially designed focusing of light beams has been proposed as a means of improving the performances of optical buffers based on cells containing hot atomic vapors (e.g., rubidium vapor). There is also a companion proposal to improve performance by use of incoherent optical pumping under suitable conditions. Regarding the proposal to use focusing: The utility of atomic-vapor optical buffers as optical storage and processing devices has been severely limited by nonuniform spatial distributions of intensity in optical beams, arising from absorption of the beams as they propagate in atomic-vapor cells. Such nonuniformity makes it impossible to optimize the physical conditions throughout a cell, thereby making it impossible to optimize the performance of the cell as an optical buffer. In practical terms simplified for the sake of brevity, "to optimize" as used here means to design the cell so as to maximize the group delay of an optical pulse while keeping the absorption and distortion of the pulse reasonably small. Regarding the proposal to use incoherent optical pumping: For reasons too complex to describe here, residual absorption of light is one of the main impediments to achievement of desirably long group delays in hot atomic vapors. The present proposal is directed toward suppressing residual absorption of light. The idea of improving the performance of slow-light optical buffers by use of incoherent pumping overlaps somewhat with the basic idea of Raman-based slow-light systems. However, prior studies of those systems did not quantitatively answer the question of whether the performance of an atomic vapor or other medium that exhibits electromagnetically induced transparency (EIT) with Raman gain is superior to that of a medium that exhibits EIT without Raman gain.

Contrasting seasonality in optical-biogeochemical properties of the Baltic Sea.

PubMed

Simis, Stefan G H; Ylöstalo, Pasi; Kallio, Kari Y; Spilling, Kristian; Kutser, Tiit

2017-01-01

Optical-biogeochemical relationships of particulate and dissolved organic matter are presented in support of remote sensing of the Baltic Sea pelagic. This system exhibits strong seasonality in phytoplankton community composition and wide gradients of chromophoric dissolved organic matter (CDOM), properties which are poorly handled by existing remote sensing algorithms. Absorption and scattering properties of particulate matter reflected the seasonality in biological (phytoplankton succession) and physical (thermal stratification) processes. Inherent optical properties showed much wider variability when normalized to the chlorophyll-a concentration compared to normalization to either total suspended matter dry weight or particulate organic carbon. The particle population had the largest optical variability in summer and was dominated by organic matter in both seasons. The geographic variability of CDOM and relationships with dissolved organic carbon (DOC) are also presented. CDOM dominated light absorption at blue wavelengths, contributing 81% (median) of the absorption by all water constituents at 400 nm and 63% at 442 nm. Consequentially, 90% of water-leaving radiance at 412 nm originated from a layer (z90) no deeper than approximately 1.0 m. With water increasingly attenuating light at longer wavelengths, a green peak in light penetration and reflectance is always present in these waters, with z90 up to 3.0-3.5 m depth, whereas z90 only exceeds 5 m at biomass < 5 mg Chla m-3. High absorption combined with a weakly scattering particle population (despite median phytoplankton biomass of 14.1 and 4.3 mg Chla m-3 in spring and summer samples, respectively), characterize this sea as a dark water body for which dedicated or exceptionally robust remote sensing techniques are required. Seasonal and regional optical-biogeochemical models, data distributions, and an extensive set of simulated remote-sensing reflectance spectra for testing of remote sensing algorithms are provided as supplementary data.

[THE PHYSICAL CHEMICAL, BIOLOGICAL BASICS OF CELLS ABSORPTION OF UNESTERIFIED FATTY ACIDS; ALBUMIN, CAVEOLIN, CLATHRIN AND LIPID-BINDING PROTEINS OF CYTOPLASM (THE LECTURE)].

PubMed

Titov, V N; Shoibonov, B B

2016-03-01

From aposition of phylogenetic theory of general pathology, obesity and metabolic syndrome are pathology of fatty cells. However, the first is a pathology of phylogenetically early visceral fatty cells of omentum. They supply with substratum of energy realization of biologic function of trophology, homeostasis, endoecology and adaptation. The visceral fatty cells of omentum have no receptors to insulin and synthesize adaptively insulin and they are not characterized by biologic reaction of proliferation. The obesity is a pathology of late in phylogenesis subcutaneous adpocytes. They are insulin-dependent and supply with substratum of energy realization of one biologic function of locomotion--movement at the expense of constriction of cross-striated miocytes. The adipocytes in terms of adaptation synthesize humoral mediator adponectin and actively implement biologic function of proliferation. Under both aphysiologic conditions increases passive by gradient of concentration, absorption by cells albumin-unbound free fatty acids in unionized form in micellae's composition. The passive aphysiologic absorption of free fatty acids by cells which under intracellular compartmentalization don't oxidize mitochondria results in synthesis, accumulation of triglycerides in cytoplasm of cells which don't implement it physiologically. The aphysiologic absorption of free fatty acids by cells, their etherification in triglyceride, in particular, in phylogenetically late β-cells of islets and either late cardiomyocytes which fatty acids don't synthesize de novo results in development of aphysiologic processes and disorder of function. From position of biology, these cells in vivo are subjected to loss similar to apoptosis. The formation of corpuscles of apoptosis compromise biologic function of endoecology activating biologic reaction of inflammation.

Recoilless Nuclear Resonance Absorption of Gamma Radiation

NASA Astrophysics Data System (ADS)

Mössbauer, Rudolf L.

It is a high distinction to be permitted to address you on the subject of recoilless nuclear resonance absorption of gamma radiation. The methods used in this special branch of experimental physics have recently found acceptance in many areas of science. I take the liberty to confine myself essentially to the work which I was able to carry out in the years 1955-1958 at the Max Planck Institute in Heidelberg, and which finally led to establishment of the field of recoilless nuclear resonance absorption. Many investigators shared in the preparations of the basis for the research we are concerned with in this lecture. As early as the middle of the last century Stokes observed, in the case of fluorite, the phenomenon now known as fluorescence - namely, that solids, liquids, and gases under certain conditions partially absorb incident electromagnetic radiation which immediately is reradiated. A special case is the so-called resonance fluorescence, a phenomenon in which the re-emitted and the incident radiation both are of the same wavelength. The resonance fluorescence of the yellow D lines of sodium in sodium vapour is a particularly notable and exhaustively studied example. In this optical type of resonance fluorescence, light sources are used in which the atoms undergo transitions from excited states to their ground states (Fig. 1.1). The light quanta emitted in these transitions (A → B) are used to initiate the inverse process of resonance absorption in the atoms of an absorber which are identical with the radiating atoms. The atoms of the absorber undergo a transition here from the ground state (B) to the excited state (A), from which they again return to the ground state, after a certain time delay, by emission of fluorescent light.

Bio-Inspired Photon Absorption and Energy Transfer for Next Generation Photovoltaic Devices

NASA Astrophysics Data System (ADS)

Magsi, Komal

Nature's solar energy harvesting system, photosynthesis, serves as a model for photon absorption, spectra broadening, and energy transfer. Photosynthesis harvests light far differently than photovoltaic cells. These differences offer both engineering opportunity and scientific challenges since not all of the natural photon absorption mechanisms have been understood. In return, solar cells can be a very sensitive probe for the absorption characteristics of molecules capable of transferring charge to a conductive interface. The objective of this scientific work is the advancement of next generation photovoltaics through the development and application of natural photo-energy transfer processes. Two scientific methods were used in the development and application of enhancing photon absorption and transfer. First, a detailed analysis of photovoltaic front surface fluorescent spectral modification and light scattering by hetero-structure was conducted. Phosphor based spectral down-conversion is a well-known laser technology. The theoretical calculations presented here indicate that parasitic losses and light scattering within the spectral range are large enough to offset any expected gains. The second approach for enhancing photon absorption is based on bio-inspired mechanisms. Key to the utilization of these natural processes is the development of a detailed scientific understanding and the application of these processes to cost effective systems and devices. In this work both aspects are investigated. Dye type solar cells were prepared and tested as a function of Chlorophyll (or Sodium-Copper Chlorophyllin) and accessory dyes. Forster has shown that the fluorescence ratio of Chlorophyll is modified and broadened by separate photon absorption (sensitized absorption) through interaction with nearby accessory pigments. This work used the dye type solar cell as a diagnostic tool by which to investigate photon absorption and photon energy transfer. These experiments shed some doubt on the Foster Resonant Energy Transfer mechanism since energy relay dye architecture-photosensitizer mixtures do not broaden the response of solar cells. Spectral absorption characterization of chromophore-Chlorophyll solutions in varying solvent polarity confirm the lack of cooperative absorption via a Foster-like mechanism and point the way to new concepts of cooperative absorption in natural systems and the development of a new photovoltaic paradigm.

Dense electron-positron plasmas and ultraintense γ rays from laser-irradiated solids.

PubMed

Ridgers, C P; Brady, C S; Duclous, R; Kirk, J G; Bennett, K; Arber, T D; Robinson, A P L; Bell, A R

2012-04-20

In simulations of a 10 PW laser striking a solid, we demonstrate the possibility of producing a pure electron-positron plasma by the same processes as those thought to operate in high-energy astrophysical environments. A maximum positron density of 10(26) m(-3) can be achieved, 7 orders of magnitude greater than achieved in previous experiments. Additionally, 35% of the laser energy is converted to a burst of γ rays of intensity 10(22) W cm(-2), potentially the most intense γ-ray source available in the laboratory. This absorption results in a strong feedback between both pair and γ-ray production and classical plasma physics in the new "QED-plasma" regime.

Lunar surface magnetometer experiment

NASA Technical Reports Server (NTRS)

Dyal, P.; Parkin, C. W.; Sonett, C. P.

1972-01-01

The Apollo 15 lunar-surface magnetometer (LSM) is one of a network of magnetometers that have been deployed on the moon to study intrinsic remanent magnetic fields and global magnetic response of the moon to large-scale solar and terrestrial magnetic fields. From these field measurements, properties of the lunar interior such as magnetic permeability, electrical conductivity, and temperature can be calculated. In addition, correlation with solar-wind-spectrometer data allows study of the the solar-wind plasma interaction with the moon and, in turn, investigation of the resulting absorption of gases and accretion of an ionosphere. These physical parameters and processes determined from magnetometer measurements must be accounted for by comprehensive theories of origin and evolution of the moon and solar system.

Pluronic F127/chitosan blend microspheres for mucoadhesive drug delivery

NASA Astrophysics Data System (ADS)

Gu, W. Z.; Hu, X. F.

2017-01-01

Pluronic F127/chitosan blend microspheres were prepared via emulsification and cross-linking process using glutaraldehyde as a cross-linker. Compared with chitosan microspheres fabricated under the same experimental conditions, blend microspheres exhibited better physical stability and higher swelling capacity. Puerarin, a traditional Chinese medicine, was incorporated into microparticlesas the model drug. The in vitro release of puerarin from blend microspheres was reduced because of the improved compatibility of the drug with the matrices. According to the results from in vitro adhesion experiments, mucoadhesive behavior of blend microspheres on a mucosa-like surface was similar to that of chitosan microspheres, despite their good ability of anti-protein absorption in solution.

Energy-absorption capability of composite tubes and beams. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Farley, Gary L.; Jones, Robert M.

1989-01-01

In this study the objective was to develop a method of predicting the energy-absorption capability of composite subfloor beam structures. Before it is possible to develop such an analysis capability, an in-depth understanding of the crushing process of composite materials must be achieved. Many variables affect the crushing process of composite structures, such as the constituent materials' mechanical properties, specimen geometry, and crushing speed. A comprehensive experimental evaluation of tube specimens was conducted to develop insight into how composite structural elements crush and what are the controlling mechanisms. In this study the four characteristic crushing modes, transverse shearing, brittle fracturing, lamina bending, and local buckling were identified and the mechanisms that control the crushing process defined. An in-depth understanding was developed of how material properties affect energy-absorption capability. For example, an increase in fiber and matrix stiffness and failure strain can, depending upon the configuration of the tube, increase energy-absorption capability. An analysis to predict the energy-absorption capability of composite tube specimens was developed and verified. Good agreement between experiment and prediction was obtained.

More Constraints on the Physical Conditions of the Kinematically Complex, Multiphase Absorption Line System at z=0.93 toward PG1206+459

NASA Astrophysics Data System (ADS)

Rosenwasser, Ben; Muzahid, Sowgat; Norris, Jackson; Charlton, Jane C.

2015-01-01

We present the results of photo- and collisional ionization modeling of the strong MgII absorption system at redshift z~0.93 towards the quasar PG1206+459. This system has been extensively studied over the last two decades (Churchill & Charlton 1999; Ding et al. 2003; Tripp et al. 2011) using a combination of spectra from Keck/HIRES, HST/FOS, HST/STIS, and HST/COS. Here we present newconstraints using the most complete spectral coverage including more recent observations of OVI and the Lyman series from HST/COS. Numerous absorption components are seen over a large velocity spread (~1500km/s), and multiple ionization phases are required to account for the detected transitions, which include MgI, MgII, FeII, SiII, SiIII, SiIV, CII, CIII, CIV, SIII, SIV, SV, SVI, NIII, NIV, NV, OIII, OIV, OV, OVI, and NeVIII. Considering the new constraints, we revisit the question of the physical nature of the structures that produce this absorber.

Study of physical and sound absorbing property of epoxy blended coir dust biocomposite

NASA Astrophysics Data System (ADS)

Nath, G.; Mishra, S. P.

2016-09-01

Reinforcement biocomposite has gained more attention recently due to its low cost, abundantly availability, low density, specific properties, easy method of separation, enhanced energy recovery, CO2 neutrality, biodegradability and recyclable in nature. As a waste product of coconut fruit, the coconut coir dust (CCD) obtained from the coconut husk. The biocomposite material prepared from the CCD modified with the proper blended solution with the help of ultrasonic technique. The study of adiabatic compressibility of acetone / water (70/30) worth its blending property for bleaching of CCD. The biocomposite material of CCD was prepared with epoxy resin. The different physical properties such as sound absorption coefficient, thermal conductivity and electrical conductivity were measured. The morphological study of biocomposite and measurement of sound absorption coefficient shows good evidence of sound absorbing characteristics of biocomposite of CCD. The sound absorption property of composite material shows a significant result where as the thermal conductivity and electrical conductivity executes a weak result. Thus biocomposite of CCD can acts as a good sound absorber and band conductor of heat and electric current.

Sound, infrasound, and sonic boom absorption by atmospheric clouds.

PubMed

Baudoin, Michaël; Coulouvrat, François; Thomas, Jean-Louis

2011-09-01

This study quantifies the influence of atmospheric clouds on propagation of sound and infrasound, based on an existing model [Gubaidulin and Nigmatulin, Int. J. Multiphase Flow 26, 207-228 (2000)]. Clouds are considered as a dilute and polydisperse suspension of liquid water droplets within a mixture of dry air and water vapor, both considered as perfect gases. The model is limited to low and medium altitude clouds, with a small ice content. Four physical mechanisms are taken into account: viscoinertial effects, heat transfer, water phase changes (evaporation and condensation), and vapor diffusion. Physical properties of atmospheric clouds (altitude, thickness, water content and droplet size distribution) are collected, along with values of the thermodynamical coefficients. Different types of clouds have been selected. Quantitative evaluation shows that, for low audible and infrasound frequencies, absorption within clouds is several orders of magnitude larger than classical absorption. The importance of phase changes and vapor diffusion is outlined. Finally, numerical simulations for nonlinear propagation of sonic booms indicate that, for thick clouds, attenuation can lead to a very large decay of the boom at the ground level. © 2011 Acoustical Society of America

On the origin of the water vapor continuum absorption within rotational and fundamental vibrational bands

NASA Astrophysics Data System (ADS)

Serov, E. A.; Odintsova, T. A.; Tretyakov, M. Yu.; Semenov, V. E.

2017-05-01

Analysis of the continuum absorption in water vapor at room temperature within the purely rotational and fundamental ro-vibrational bands shows that a significant part (up to a half) of the observed absorption cannot be explained within the framework of the existing concepts of the continuum. Neither of the two most prominent mechanisms of continuum originating, namely, the far wings of monomer lines and the dimers, cannot reproduce the currently available experimental data adequately. We propose a new approach to developing a physically based model of the continuum. It is demonstrated that water dimers and wings of monomer lines may contribute equally to the continuum within the bands, and their contribution should be taken into account in the continuum model. We propose a physical mechanism giving missing justification for the super-Lorentzian behavior of the intermediate line wing. The qualitative validation of the proposed approach is given on the basis of a simple empirical model. The obtained results are directly indicative of the necessity to reconsider the existing line wing theory and can guide this consideration.

Energy deposition processes in biological tissue: nonthermal biohazards seem unlikely in the ultra-high frequency range.

PubMed

Pickard, W F; Moros, E G

2001-02-01

The prospects of ultra high frequency (UHF, 300--3000 MHz) irradiation producing a nonthermal bioeffect are considered theoretically and found to be small. First, a general formula is derived within the framework of macroscopic electrodynamics for the specific absorption rate of microwaves in a biological tissue; this involves the complex Poynting vector, the mass density of the medium, the angular frequency of the electromagnetic field, and the three complex electromagnetic constitutive parameters of the medium. In the frequency ranges used for cellular telephony and personal communication systems, this model predicts that the chief physical loss mechanism will be ionic conduction, with increasingly important contributions from dielectric relaxation as the frequency rises. However, even in a magnetite unit cell within a magnetosome the deposition rate should not exceed 1/10 k(B)T per second. This supports previous arguments for the improbability of biological effects at UHF frequencies unless a mechanism can be found for accumulating energy over time and space and focussing it. Second, three possible nonthermal accumulation mechanisms are then considered and shown to be unlikely: (i) multiphoton absorption processes; (ii) direct electric field effects on ions; (iii) cooperative effects and/or coherent excitations. Finally, it is concluded that the rate of energy deposition from a typical field and within a typical tissue is so small as to make unlikely any significant nonthermal biological effect. Copyright 2001 Wiley-Liss, Inc.

Valorization of lignite combustion residues and ferroalumina in the production of aggregates.

PubMed

Anagnostopoulos, I M; Stivanakis, V E; Angelopoulos, G N; Papamantellos, D C

2010-02-15

The present research study investigates the synergy of industrial solid by-products from lignite combustion (fly ash and bottom ash) and aluminum production (ferroalumina) in the production of lightweight aggregates (LWA). The process consists of two stages, pelletization and sintering. Bottom ash (BA) is used as the principal raw material in mixtures while ferroalumina (FAL) is added in lower percentages (5-30 wt%). BA carbon content is used as the fuel of sintering process in high temperatures, around 1250 degrees C, and gas generation is responsible for porous structure formation. Physical properties such as porosity, water absorption and bulk density, of sintering products are measured. Increase of FAL percentage in sintering mixtures results in decrease of porosity from 61% to 35% and of water absorption from 61% to 21% and in increase of bulk density from 1.02 g/cm(3) to 1.80 g/cm(3) of the produced aggregates. Aggregates produced by FAL addition up to 20 wt% are characterized as LWA. Aggregates formed are used in the production of concrete specimens. Compressive strength of concrete increases by increasing FAL addition in aggregates from 5 wt% to 15 wt% (highest strength value), while decrease by increasing FAL addition from 20 wt% to 30 wt%. FAL addition in lignite ashes sintering mixtures (up to 15 wt%) is considered as an important parameter for enhancing aggregates strength.

The UV to Near-IR Optical Properties of PAHs: A Semi-Empirical Model

NASA Technical Reports Server (NTRS)

Mattioda, A. L.; Allamandola, L. J.; Hudgins, D. M.

2005-01-01

Interstellar Polycyclic Aromatic Hydrocarbon (PAH) infrared emission features represent an important and unique diagnostic tool of the chemical and physical conditions throughout the universe. However, one challenge facing the widely accepted PAH emission model has been the detection of infrared features in regions of low UV flux. Utilizing recently published laboratory Near Infrared VIR) PAH ion absorption data measured in our laboratory, we build upon previous models for PAH ion absorption in the UV-Vis to extrapolate a new model which incorporates PAH ion absorption in the NIR. This model provides a basis for comparing the relative energy absorption of PAH ions in the UV-Vis and NIR regions for a wide variety of stellar types. This model demonstrates that the radiation from late-type stars can pump the mid-IR PAH features.

Mean absorption coefficients of He/Ar/N2/(C1-x-y , Ni x , Co y ) thermal plasmas for CNT synthesis

NASA Astrophysics Data System (ADS)

Salem, D.; Hannachi, R.; Cressault, Y.; Teulet, Ph; Béji, L.

2017-01-01

In this paper, we present the mean absorption coefficients (MACs) calculated for plasma mixtures of argon-helium-nitrogen-carbon-nickel-cobalt at 60 kPa and in a temperature range from 1 kK to 20 kK. These coefficients have been computed under the assumption of a local thermodynamic equilibrium (LTE), isothermal plasma, including atomic and molecular continuum, molecular bands and lines radiation splitted into nine spectral intervals. The results show that the continuum absorption coefficients strongly depend on photodissociation and photoionization processes of the molecular species N2, CN and C2, with a significant effect on photodetachment processes of C- in a frequency interval lower than 1  ×  1015 Hz and for low temperature (<6 kK). While at high temperature, the main contribution in continuum absorption coefficient comes from radiative recombination processes except in the infrared region (<0.5  ×  1015 Hz) where the inverse bremsstrahlung represents the most important component in continuum processes for all temperature values. On the other hand, the calculation of MAC shows that the role of molecular continuum, molecular bands and line absorption of the neutral catalysis species Ni/Co are only important in a small range of temperature and in a few spectral bands located in visible and infrared regions, while at high temperature and in UV and visible regions, the foremost contributions to MAC come from atomic continuum and line absorption.

Pharmacokinetics of lidocaine and bupivacaine following subarachnoid administration in surgical patients: simultaneous investigation of absorption and disposition kinetics using stable isotopes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burm, A.G.; Van Kleef, J.W.; Vermeulen, N.P.

1988-10-01

The pharmacokinetics of lidocaine and bupivacaine following subarachnoid administration were studied in 12 surgical patients using a stable isotope method. After subarachnoid administration of the agent to be evaluated, a deuterium-labelled analogue was administered intravenously. Blood samples were collected for 24 h. Plasma concentrations of the unlabelled and the deuterium-labelled local anesthetics were determined using a combination of capillary gas chromatography and mass fragmentography. Bi-exponential functions were fitted to the plasma concentration-time data of the deuterium-labelled local anesthetics. The progression of the absorption was evaluated using deconvolution. Mono- and bi-exponential functions were then fitted to the fraction absorbed versus timemore » data. The distribution and elimination half-lives of the deuterium-labelled analogues were 25 +/- 13 min (mean +/- SD) and 121 +/- 31 min for lidocaine and 19 +/- 10 min and 131 +/- 33 min for bupivacaine. The volumes of the central compartment and steady-state volumes of distribution were: lidocaine 57 +/- 10 l and 105 +/- 25 l, bupivacaine 25 +/- 6 l and 63 +/- 22 l. Total plasma clearance values averaged 0.97 +/- 0.21 l/min for lidocaine and 0.56 +/- 0.14 l/min for bupivacaine. The absorption of lidocaine could be described by a single first order absorption process, characterized by a half-life of 71 +/- 17 min in five out of six patients. The absorption of bupivacaine could be described adequately assuming two parallel first order absorption processes in all six patients. The half-lives, characterizing the fast and slow absorption processes of bupivacaine, were 50 +/- 27 min and 408 +/- 275 min, respectively. The fractions of the dose, absorbed in the fast and slow processes, were 0.35 +/- 0.17 and 0.61 +/- 0.16, respectively.« less

An Intercomparison Study of Two Proximate Damped Lyα Systems with Residual Flux upon the Lyα Absorption Trough toward Quasars

NASA Astrophysics Data System (ADS)

Xie, Xiaoyi; Zhou, Hongyan; Pan, Xiang; Jiang, Peng; Shi, Xiheng; Ji, Tuo; Zhang, Shaohua; Wu, Shengmiao; Zhong, Zhihao

2018-05-01

In this paper, we present an intercomparison study of two quasars, SDSS J145618.32+340037.2 and SDSS J215331.50–025514.1, which have proximate damped Lyα systems (PDLAs) with residual flux upon the Lyα absorption trough. Though they both have residual flux as luminous as 1043 erg s‑1, their PDLAs are quite different in, e.g., neutral hydrogen column density, metal line absorption strength, high-ionization absorption lines as well as residual flux strength. For J1456+3400, the H I column density is log(N H I /cm–2) = 20.6 ± 0.2, with z abs = 2.3138, nearly identical to the quasar redshift (z = 2.3142) determined from the [O III] emission line. The metallicity of this system is typical of DLAs and there is high ionization therein, suggesting that the PDLA system is multiphase, putting it in the quasar environment. For J2153–0255, we measure the H I column density to be log(N H I /cm–2) = 21.5 ± 0.1 at z abs = 3.511, slightly redshifted with respect to the quasar (z = 3.490) measured from C III]. The metallicity of this system is quite low and there is a lack of significant high-ionization absorption lines therein, suggesting that the system is beyond the quasar host galaxy. The residual flux is wide (∼1000 km s‑1) in J1456, with a significance of ∼8σ, while also wide (∼1500 km s‑1) but with a smaller significance of ∼3σ in J2153. Among many explanations, we find that Lyα fuzz or resonant scattering can be used to explain the residual flux in the two sources while partial coverage cannot be excluded for J1456. By comparing these two cases, together with a similar case reported previously, we suggest that the strength of the residual flux is related to properties such as metallicity and high-ionization absorption lines of PDLAs. The residual flux recorded upon the PDLA absorption trough opens a window for us to see the physical conditions and processes of the quasar environment, and their profile and strength further remind us of their spatial scales.

Physical properties of erupting plasma associated with coronal mass ejections

NASA Astrophysics Data System (ADS)

Lee, J.; Raymond, J. C.; Reeves, K. K.; Moon, Y.; Kim, K.

2013-12-01

We investigate the physical properties (temperature, density, and mass) of erupting plasma observed in X-rays and EUV, which are all associated with coronal mass ejections observed by SOHO/LASCO. The erupting plasmas are observed as absorption or emission features in the low corona. The absorption feature provides a lower limit to the cold mass while the emission feature provides an upper limit to the mass of observed plasma in X-ray and EUV. We compare the mass constraints for each temperature response and find that the mass estimates in EUV and XRT are smaller than the total mass in the coronagraph. Several events were observed by a few passbands in the X-rays, which allows us to determine the temperature of the eruptive plasma using a filter ratio method. The temperature of one event is estimated at about 8.6 MK near the top of the erupting plasma. This measurement is possibly an average temperature for higher temperature plasma because the XRT is more sensitive at higher temperatures. In addition, a few events show that the absorption features of a prominence or a loop change to emission features with the beginning of their eruptions in all EUV wavelengths of SDO/AIA, which indicates the heating of the plasma. By estimating the physical properties of the erupting plasmas, we discuss the heating of the plasmas associated with coronal mass ejections in the low corona.

Using the Overhead Projector as a Light Source for Physics Demonstrations

ERIC Educational Resources Information Center

Mak, Se-Yuen

2006-01-01

This article illustrates how the overhead projector can be used as a light source in some peculiar ways for physics demonstrations. Five examples are included: (1) Study of chromatic aberration; (2) Making giant Newton's rings; (3) Comparison of the rate of heat absorption by different surfaces; (4) Demonstration of greenhouse effect; and (5)…

Forster Resonance Energy Transfer and Conformational Stability of Proteins: An Advanced Biophysical Module for Physical Chemistry Students

ERIC Educational Resources Information Center

Sanchez, Katheryn M.; Schlamadinger, Diana E.; Gable, Jonathan E.; Kim, Judy E.

2008-01-01

Protein folding is an exploding area of research in biophysics and physical chemistry. Here, we describe the integration of several techniques, including absorption spectroscopy, fluorescence spectroscopy, and Forster resonance energy transfer (FRET) measurements, to probe important topics in protein folding. Cytochrome c is used as a model…

Pulse Oximetry in the Physics Lab: A Colorful Alternative to Traditional Optics Curricula

ERIC Educational Resources Information Center

Kutschera, Ellynne; Dunlap, Justin C.; Byrd, Misti; Norlin, Casey; Widenhorn, Ralf

2013-01-01

We designed a physics laboratory exercise around pulse oximetry, a noninvasive medical technique used to assess a patient's blood oxygen saturation. An alternative to a traditional optics and light lab, this exercise teaches the principles of light absorption, spectroscopy, and the properties of light, while simultaneously studying a common…

Dynamic Optoelectronic Properties in Perovskite Oxide Thin Films Measured with Ultrafast Transient Absorption & Reflectance Spectroscopy

NASA Astrophysics Data System (ADS)

Smolin, Sergey Y.

Ultrafast transient absorption and reflectance spectroscopy are foundational techniques for studying photoexcited carrier recombination mechanisms, lifetimes, and charge transfer rates. Because quantifying photoexcited carrier dynamics is central to the intelligent design and improvement of many solid state devices, these transient optical techniques have been applied to a wide range of semiconductors. However, despite their promise, interpretation of transient absorption and reflectance data is not always straightforward and often relies on assumptions of physical processes, especially with respect to the influence of heating. Studying the material space of perovskite oxides, the careful collection, interpretation, and analysis of ultrafast data is presented here as a guide for future research into novel semiconductors. Perovskite oxides are a class of transition metal oxides with the chemical structure ABO3. Although traditionally studied for their diverse physical, electronic, and magnetic properties, perovskite oxides have gained recent research attention as novel candidates for light harvesting applications. Indeed, strong tunable absorption, unique interfacial properties, and vast chemical flexibility make perovskite oxides a promising photoactive material system. However, there is limited research characterizing dynamic optoelectronic properties, such as recombination lifetimes, which are critical to know in the design of any light-harvesting device. In this thesis, ultrafast transient absorption and reflectance spectroscopy was used to understand these dynamic optoelectronic properties in highquality, thin (<50 nm) perovskite oxide films grown by molecular beam epitaxy. Starting with epitaxial LaFeO3 (LFO) grown on (LaAlO 3)0.3(Sr2AlTaO6)0.7 (LSAT), transient absorption spectroscopy reveals two photoinduced absorption features at the band gap of LFO at 2.4 eV and at the higher energy absorption edge at 3.5 eV. Using a combination of temperature-dependent, variable-angle spectroscopic ellipsometry and time-resolved ultrafast optical spectroscopy on a type I heterostructure, we clarify thermal and electronic contributions to spectral transients in LaFeO3. Upon comparison to thermally-derived static spectra of LaFeO3, we find that thermal contributions dominate the transient absorption and reflectance spectra above the band gap. A transient photoinduced absorption feature below the band gap at 1.9 eV is not reproduced in the thermally derived spectra and has significantly longer decay kinetics from the thermallyinduced features; therefore, this long lived photoinduced absorption is likely derived, at least partially, from photoexcited carriers with lifetimes much longer than 3 nanoseconds. LaFeO3 has a wide band gap of 2.4 eV but its absorption can be decreased with chemical substitution of Sr for Fe to make it more suitable for various applications. This type of A-site substitution is a common route to change static optical absorption in perovskite oxides, but there are no systematic studies looking at how A-site substitution changes dynamic optoelectronic properties. To understand the relationship between composition and static and dynamic optical properties we worked with the model system of La1-xSrxFeO 3-delta epitaxial films grown on LSAT, uncovering the effects of A-site cation substitution and oxygen stoichiometry. Variable-angle spectroscopic ellipsometry was used to measure static optical properties, revealing a linear increase in absorption coefficient at 1.25 eV and a red-shifting of the optical absorption edge with increasing Sr fraction. The absorption spectra can be similarly tuned through the introduction of oxygen vacancies, indicating the critical role that nominal Fe valence plays in optical absorption. Dynamic optoelectronic properties were studied with ultrafast transient reflectance spectroscopy with broadband visible (1.6 eV to 4 eV) and near-infrared (0.9 eV to 1.5 eV) probes. The sign of the reflectance change in the near-infrared region in LSFO is indicative of carrier bandfilling of newly created electronic states by photoexcited carriers. Moreover, we find that similar transient spectral trends can be induced with A-site substitution or through oxygen vacancies, which is a surprising result. Probing the near-infrared region reveals similar nanosecond (1-3 ns) photoexcited carrier lifetimes for oxygen deficient and stoichiometric films. These results demonstrate that while the static optical absorption is strongly dependent on nominal Fe valence tuned through cation or anion stoichiometry, oxygen vacancies do not appear to play a significantly detrimental role in long lived recombination kinetics. Although this thesis represents one of the first comprehensive studies using broad band transient absorption and reflectance spectroscopy to study dynamic optoelectronic phenomena in perovskite oxides, it can also serve as a guide for the implementation and interpretation of ultrafast spectroscopy in other material systems. Moreover, the ultrafast work on perovskite oxides indicates that these materials have long nanosecond lifetimes required for light harvesting devices and should be investigated further.

Functional studies of Drosophila zinc transporters reveal the mechanism for dietary zinc absorption and regulation

PubMed Central

2013-01-01

Background Zinc is key to the function of many proteins, but the process of dietary zinc absorption is not well clarified. Current knowledge about dietary zinc absorption is fragmented, and mostly derives from incomplete mammalian studies. To gain a comprehensive picture of this process, we systematically characterized all zinc transporters (that is, the Zip and ZnT family members) for their possible roles in dietary zinc absorption in a genetically amenable model organism, Drosophila melanogaster. Results A set of plasma membrane-resident zinc transporters was identified to be responsible for absorbing zinc from the lumen into the enterocyte and the subsequent exit of zinc to the circulation. dZip1 and dZip2, two functionally overlapping zinc importers, are responsible for absorbing zinc from the lumen into the enterocyte. Exit of zinc to the circulation is mediated through another two functionally overlapping zinc exporters, dZnT1, and its homolog CG5130 (dZnT77C). Somewhat surprisingly, it appears that the array of intracellular ZnT proteins, including the Golgi-resident dZnT7, is not directly involved in dietary zinc absorption. By modulating zinc status in different parts of the body, we found that regulation of dietary zinc absorption, in contrast to that of iron, is unresponsive to bodily needs or zinc status outside the gut. The zinc transporters that are involved in dietary zinc absorption, including the importers dZip1 and dZip2, and the exporter dZnT1, are respectively regulated at the RNA and protein levels by zinc in the enterocyte. Conclusions Our study using the model organism Drosophila thus starts to reveal a comprehensive sketch of dietary zinc absorption and its regulatory control, a process that is still incompletely understood in mammalian organisms. The knowledge gained will act as a reference for future mammalian studies, and also enable an appreciation of this important process from an evolutionary perspective. PMID:24063361

Physical-geometric optics method for large size faceted particles.

PubMed

Sun, Bingqiang; Yang, Ping; Kattawar, George W; Zhang, Xiaodong

2017-10-02

A new physical-geometric optics method is developed to compute the single-scattering properties of faceted particles. It incorporates a general absorption vector to accurately account for inhomogeneous wave effects, and subsequently yields the relevant analytical formulas effective and computationally efficient for absorptive scattering particles. A bundle of rays incident on a certain facet can be traced as a single beam. For a beam incident on multiple facets, a systematic beam-splitting technique based on computer graphics is used to split the original beam into several sub-beams so that each sub-beam is incident only on an individual facet. The new beam-splitting technique significantly reduces the computational burden. The present physical-geometric optics method can be generalized to arbitrary faceted particles with either convex or concave shapes and with a homogeneous or an inhomogeneous (e.g., a particle with a core) composition. The single-scattering properties of irregular convex homogeneous and inhomogeneous hexahedra are simulated and compared to their counterparts from two other methods including a numerically rigorous method.

Ultrafast carrier dynamics of titanic acid nanotubes investigated by transient absorption spectroscopy.

PubMed

Wang, Li; Zhao, Hui; Pan, Lin Yun; Weng, Yu Xiang; Nakato, Yoshihiro; Tamai, Naoto

2010-12-01

Carrier dynamics of titanic acid nanotubes (phase of H2Ti2O5.H2O) deposited on a quartz plate was examined by visible/near-IR transient absorption spectroscopy with an ultraviolet excitation. The carrier dynamics of titanic acid nanotubes follows the fast trapping process which attributed to the intrinsic tubular structure, the relaxation of shallow trapped carriers and the recombination as a second-order kinetic process. Transient absorption of titanic acid nanotubes was dominated by the absorption of surface-trapped holes in visible region around 500 nm, which was proved by the faster decay dynamics in the presence of polyvinyl alcohol as a hole-scavenger. However, the slow relaxation of free carriers was much more pronounced in the TiO2 single crystals, as compared with the transient absorption spectra of titanic acid nanotubes under the similar excitation.

Nanoimprint-Transfer-Patterned Solids Enhance Light Absorption in Colloidal Quantum Dot Solar Cells.

PubMed

Kim, Younghoon; Bicanic, Kristopher; Tan, Hairen; Ouellette, Olivier; Sutherland, Brandon R; García de Arquer, F Pelayo; Jo, Jea Woong; Liu, Mengxia; Sun, Bin; Liu, Min; Hoogland, Sjoerd; Sargent, Edward H

2017-04-12

Colloidal quantum dot (CQD) materials are of interest in thin-film solar cells due to their size-tunable bandgap and low-cost solution-processing. However, CQD solar cells suffer from inefficient charge extraction over the film thicknesses required for complete absorption of solar light. Here we show a new strategy to enhance light absorption in CQD solar cells by nanostructuring the CQD film itself at the back interface. We use two-dimensional finite-difference time-domain (FDTD) simulations to study quantitatively the light absorption enhancement in nanostructured back interfaces in CQD solar cells. We implement this experimentally by demonstrating a nanoimprint-transfer-patterning (NTP) process for the fabrication of nanostructured CQD solids with highly ordered patterns. We show that this approach enables a boost in the power conversion efficiency in CQD solar cells primarily due to an increase in short-circuit current density as a result of enhanced absorption through light-trapping.

On pulsating cosmic /radio/ noise absorption

NASA Technical Reports Server (NTRS)

Dangelo, N.

1981-01-01

It has been proposed that some absorption events measured on riometers are actually due to backscatter of cosmic radio noise by E-region plasma waves (D'Angelo, 1976, 1978; D'Angelo and Mehta, 1980). Assuming that DC or nearly DC absorption is a viable process, it is shown that it may also be operative in producing pulsations in cosmic noise absorption on riometers, with periods ranging from a few seconds to several minutes.

Study of Water Absorption Lines in the Near Infrared

DTIC Science & Technology

1975-02-17

the absorption coefficient is better approximated by the sum of Matcha -N«. oec short range contribution and W-BB dispersion contribution. The...and W. Byers Brown, Molecular Physics 2S, 1105 (1973). 5. R. L. Matcha and R. K. Nesbet, Phys. Rev. 1_6_0, 72 (1967). I H. B. Levine, Phys. Rev...reasurcrents of Ouren, ^eltqen Gaide, Helbing and Pauly. The dipole moment function is taken from ab initio 9 calculations of Matcha and Nesbet. With

Modeling of laser interactions with composite materials

DOE PAGES

Rubenchik, Alexander M.; Boley, Charles D.

2013-05-07

In this study, we develop models of laser interactions with composite materials consisting of fibers embedded within a matrix. A ray-trace model is shown to determine the absorptivity, absorption depth, and optical power enhancement within the material, as well as the angular distribution of the reflected light. We also develop a macroscopic model, which provides physical insight and overall results. We show that the parameters in this model can be determined from the ray trace model.

44th Annual Anomalous Absorption Conference

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beg, Farhat

Conference Grant Report July 14, 2015 Submitted to the U. S. Department of Energy Attn: Dr. Sean Finnegan By the University of California, San Diego 9500 Gilman Drive La Jolla, California 92093 On behalf of the 44th Annual Anomalous Absorption Conference 8-13 June 2014, in Estes Park, Colorado Support Requested: $10,100 Amount expended: $3,216.14 Performance Period: 1 March 20 14 to 28 February 20 15 Principal Investigator Dr. Farhat Beg Center for Energy Research University of California, San Diego 9500 Gilman Drive La Jolla, California 92093-0417 858-822-1266 (telephone) 858-534-4543 (fax) fbeg@ucsd.edu Administrative Point of Contact: Brandi Pate, 858-534-0851, blpate®ucsd.edu I.more » Background The forty-fourth Anomalous Absorption Conference was held in Estes Park, Colorado from June 5-8, 2014 (aac2014.ucsd.edu). The first Anomalous Absorption Conference was held in 1971 to assemble experts in the poorly understood area of laser-plasma absorption. The goal of that conference was to address the anomalously large laser absorption seen in plasma experiments with respect to the laser absorption predicted by linear plasma theory. Great progress in this research area has been made in the decades since that first meeting, due in part to the scientific interactions that have occurred annually at this conference. Specifically, this includes the development of nonlinear laser-plasma theory and the simulation of laser interactions with plasmas. Each summer since that first meeting, this week-long conference has been held at unique locations in North America as a scientific forum for intense scientific exchanges relevant to the interaction of laser radiation with plasmas. Responsibility for organizing the conference has traditional rotated each year between the major Inertial Confinement Fusion (ICF) laboratories and universities including LANL, LLNL, LLE, UCLA UC Davis and NRL. As the conference has matured over the past four decades, its technical footprint has expanded beyond ICF-related laser-plasma interactions to encompass closely related technical areas including laser particle acceleration, high-intensity laser effects, short­ pulse laser interactions, PIC and Vlasov/rad-hydro modeling, inertial and magnetic fusion plasmas, advanced plasma diagnostics, alternate ignition schemes, EOS/transport/opacity, and this year, x­ ray free-electron lasers and their applications. The conference continues to be a showcase for the presentation and discussion of the latest developments in these areas. II. Meeting Report The conference was extremely successful with more than one hundred participants. There were ninety-nine (99) abstracts submitted. There were forty-four (44) presentations including eleven (11) invited talks. The following topics were covered: a) Radiation Hydrodynamics b) Implosion Plasma Kinetic Effects c) Alternate Ignition Schemes d) Astrophysical Phenomena e) Opacity/Transport/EOS f) High Power Lasers and Facilities g) High-Intensity Laser-Matter Interactions h) Hydrodynamics and Hydro-instabilities i) Hot Dense Plasma Atomic Processes j) High Energy Density Physics k) Laser Particle Acceleration Physics l) Advanced Plasma Diagnostics m) Advanced light sources and applications Despite significant advertising, there were two students who applied for the travel grants: Charlie Jarrott and Joohwan Kim. The total funds expended were $3,216.14.« less

Energy consciousness in the design of lighting for people

DOE Office of Scientific and Technical Information (OSTI.GOV)

Halldane, J.F.

1975-01-01

A comprehensive overview of energy and power distribution in the environment is presented as it relates to lighting. The objectives are to develop a consciousness of the effects of light and vision in order to utilize them more effectively. Notes are made of the physical effects of radiant power on living things and materials including thermal absorption, reflection, transmission, refraction, spectral conversion, interference, diffraction, polarization, phototropy, luminescence, photochemical changes, and photoelectric effects. Environmental issues are stressed. The evaluation process in design is briefly discussed. Reference is made to the goal, parameter, synthesis, and criterion specification as a checklist for evaluation.more » Particular concern is raised for the occupants who experience the constructed environment, since their interests do not appear to be sufficiently represented in the present day design process. Meaningfulness of measurement is emphasized and some anomalies illustrated. (auth)« less

Surface modification of calcium sulfate whisker prepared from flue gas desulfurization gypsum

NASA Astrophysics Data System (ADS)

Liu, Chengjun; Zhao, Qing; Wang, Yeguang; Shi, Peiyang; Jiang, Maofa

2016-01-01

In order to obtain hydrophobic whisker for preparing polymeric composite product, the calcium sulfate whisker (CSW) prepared from flue gas desulfurization (FGD) gypsum by hydrothermal synthesis was modified by various surfactants, and the effects of some modification conditions on the hydrophobic property of CSW were investigated in this study. Sodium stearate was considered to be a suitable surfactant and its reasonable dosage was 2% of ethanol solvent. Both physical and chemical absorptions were found in the surface modification process, and the later one was suggested to preferentially occur on the CSW surface. Moreover, modifying temperature, modifying duration, and agitation speed were experimentally found to have a remarkable influence on the modification behavior. Active ratio reached 0.845 when the modification process was conducted under reasonable conditions obtained in the current work. Finally, polypropylene sheet products were prepared from modified CSW showing an excellence mechanical property.

Modeling, Measurements, and Fundamental Database Development for Nonequilibrium Hypersonic Aerothermodynamics

NASA Technical Reports Server (NTRS)

Bose, Deepak

2012-01-01

The design of entry vehicles requires predictions of aerothermal environment during the hypersonic phase of their flight trajectories. These predictions are made using computational fluid dynamics (CFD) codes that often rely on physics and chemistry models of nonequilibrium processes. The primary processes of interest are gas phase chemistry, internal energy relaxation, electronic excitation, nonequilibrium emission and absorption of radiation, and gas-surface interaction leading to surface recession and catalytic recombination. NASAs Hypersonics Project is advancing the state-of-the-art in modeling of nonequilibrium phenomena by making detailed spectroscopic measurements in shock tube and arcjets, using ab-initio quantum mechanical techniques develop fundamental chemistry and spectroscopic databases, making fundamental measurements of finite-rate gas surface interactions, implementing of detailed mechanisms in the state-of-the-art CFD codes, The development of new models is based on validation with relevant experiments. We will present the latest developments and a roadmap for the technical areas mentioned above

Determination of the solubility and size distribution of radioactive aerosols in the uranium processing plant at NRCN.

PubMed

Kravchik, T; Oved, S; Paztal-Levy, O; Pelled, O; Gonen, R; German, U; Tshuva, A

2008-01-01

Inhalation is the main route of internal exposure to radioactive aerosols in the nuclear industry. To assess the radiation dose from the intake of these aerosols, it is necessary to know their physical (aerodynamic diameter distribution) and chemical (dissolution rate in extracellular lung fluid) characteristics. Air samples were taken from the uranium processing plant at the Nuclear Research Center, Negev. Measurements of aerodynamic diameter distribution using a cascade impactor indicated an average activity median aerodynamic diameter value close to 5 microm, in accordance with the recent recommended values of International Commission on Radiological Protection (ICRP) model. Solubility profiles of these aerosols were determined by performing in vitro solubility tests over 100 d in a simultant solution of the extracellular fluid. The tests indicated that the uranium aerosols should be assigned to an absorption between Types M and S (as defined by the ICRP Publication 66 model).

Experimental Resonance Enhanced Multiphoton Ionization (REMPI) studies of small molecules

NASA Technical Reports Server (NTRS)

Dehmer, J. L.; Dehmer, P. M.; Pratt, S. T.; Ohalloran, M. A.; Tomkins, F. S.

1987-01-01

Resonance enhanced multiphoton ionization (REMPI) utilizes tunable dye lasers to ionize an atom or molecule by first preparing an excited state by multiphoton absorption and then ionizing that state before it can decay. This process is highly selective with respect to both the initial and resonant intermediate states of the target, and it can be extremely sensitive. In addition, the products of the REMPI process can be detected as needed by analyzing the resulting electrons, ions, fluorescence, or by additional REMPI. This points to a number of exciting opportunities for both basic and applied science. On the applied side, REMPI has great potential as an ultrasensitive, highly selective detector for trace, reactive, or transient species. On the basic side, REMPI affords an unprecedented means of exploring excited state physics and chemistry at the quantum-state-specific level. An overview of current studies of excited molecular states is given to illustrate the principles and prospects of REMPI.

Adsorption of octylamine on titanium dioxide

NASA Astrophysics Data System (ADS)

Siwińska, Daria; Kołodziejczak-Radzimska, Agnieszka; Krysztafkiewicz, Andrzej; Jesionowski, Teofil

2009-05-01

Processes of adsorption and desorption of a model active substance (octylamine) on the surface of unmodified titanium dioxide (E 171) have been performed. The effects of concentration of octylamine and time of the process on the character of adsorption have been studied and the efficiency of the adsorption/desorption has been determined. The samples obtained have been studied by X-ray diffraction. The nitrogen adsorption/desorption isotherms, particle size distribution and absorption capacities of water, dibutyl phthalate and paraffin oil have been determined. The efficiency of octylamine adsorption on the surface of the titanium dioxide has been found positively correlated with the concentration of octylamine in the initial solution. The desorption of octylamine has decreased with increasing concentration of this compound adsorbed. For octylamine in low concentrations the physical adsorption has been found to dominate, which is desirable when using TiO 2 in the production of pharmaceuticals.

Laboratory Measurements of Optical Properties of Micron Size Individual Dust Grains

NASA Technical Reports Server (NTRS)

Abbas, M. M.; Craven, P. D.; Spann, J. F.; Tankosic, D.; LeClair, A.; Witherow, W. K.; Camata, R.; Gerakines, P.

2003-01-01

A laboratory program is being developed at NASA Marshall Space Flight Center for experimental determination of the optical and physical properties individual dust grains in simulated astrophysical environments. The experimental setup is based on an electrodynamic balance that permits levitation of single 0.1 - 10 micron radii dust grains in a cavity evacuated to pressures of approx. 10(exp -6) torr. The experimental apparatus is equipped with observational ports for measurements in the UV, visible, and infrared spectral regions. A cryogenic facility for cooling the particles to temperature of approx. 10-50K is being installed. The current and the planned measurements include: dust charging processes, photoelectric emissions and yields with UV irradiation, radiation pressure measurements, infrared absorption and scattering properties, and condensation processes, involving the analogs of cosmic dust grains. Selected results based on photoemissions, radiation pressure, and other laboratory measurements will be presented.

Study on organic matter fractions in the surface microlayer in the Baltic Sea by spectrophotometric and spectrofluorometric methods

NASA Astrophysics Data System (ADS)

Drozdowska, Violetta; Wrobel, Iwona; Markuszewski, Piotr; Makuch, Przemysław; Raczkowska, Anna; Kowalczuk, Piotr

2017-08-01

The fluorescence and absorption measurements of the samples collected from a surface microlayer (SML) and a subsurface layer (SS), at a depth of 1 m, were studied during three research cruises in the Baltic Sea along with hydrophysical studies and meteorological observations. Several absorption (E2 : E3, S, SR) and fluorescence (fluorescence intensities at Coble classified peaks: A, C, M, T the ratio M + T/A + C, HIX (humification index)) indices of colored and fluorescent dissolved organic matter (CDOM and FDOM) helped to describe the changes in molecular size and weight as well as in composition of organic matter. The investigation allowed the assessment of a decrease in the contribution of two terrestrial components (A and C) with increasing salinity ( ˜ 1.64 and ˜ 1.89 % in the SML and ˜ 0.78 and ˜ 0.71 % in the SS, respectively) and an increase in components produced in situ (M and T) with salinity ( ˜ 0.52 and ˜ 2.83 % in the SML and ˜ 0.98 and ˜ 1.87 % in the SS, respectively). Hence, a component T reveals the biggest relative changes along the transect from the Vistula River outlet to Gdansk Deep, in both the SML and SS, although an increase was higher in the SML than in the SS ( ˜ 18.5 and ˜ 12.3 %, respectively). The ratio E2 : E3 points to greater changes in the molecular weight of CDOM affected by a higher rate of photobleaching in the SML. The HIX index reflects a more advanced stage of humification and condensation processes in the SS. Finally, the results reveal a higher rate of degradation processes occurring in the SML than in the SS. Thus, the specific physical properties of surface active organic molecules (surfactants) may modify, in a specific way, the solar light spectrum entering the sea and a penetration depth of the solar radiation. Research on the influence of surfactants on the physical processes linked to the sea surface becomes an important task, especially in coastal waters and in the vicinity of the river mouths.

Absorption dynamics and delay time in complex potentials

NASA Astrophysics Data System (ADS)

Villavicencio, Jorge; Romo, Roberto; Hernández-Maldonado, Alberto

2018-05-01

The dynamics of absorption is analyzed by using an exactly solvable model that deals with an analytical solution to Schrödinger’s equation for cutoff initial plane waves incident on a complex absorbing potential. A dynamical absorption coefficient which allows us to explore the dynamical loss of particles from the transient to the stationary regime is derived. We find that the absorption process is characterized by the emission of a series of damped periodic pulses in time domain, associated with damped Rabi-type oscillations with a characteristic frequency, ω = (E + ε)/ℏ, where E is the energy of the incident waves and ‑ε is energy of the quasidiscrete state of the system induced by the absorptive part of the Hamiltonian; the width γ of this resonance governs the amplitude of the pulses. The resemblance of the time-dependent absorption coefficient with a real decay process is discussed, in particular the transition from exponential to nonexponential regimes, a well-known feature of quantum decay. We have also analyzed the effect of the absorptive part of the potential on the dynamical delay time, which behaves differently from the one observed in attractive real delta potentials, exhibiting two regimes: time advance and time delay.

Minority carrier diffusion lengths and absorption coefficients in silicon sheet material

NASA Technical Reports Server (NTRS)

Dumas, K. A.; Swimm, R. T.

1980-01-01

Most of the methods which have been developed for the measurement of the minority carrier diffusion length of silicon wafers require that the material have either a Schottky or an ohmic contact. The surface photovoltage (SPV) technique is an exception. The SPV technique could, therefore, become a valuable diagnostic tool in connection with current efforts to develop low-cost processes for the production of solar cells. The technique depends on a knowledge of the optical absorption coefficient. The considered investigation is concerned with a reevaluation of the absorption coefficient as a function of silicon processing. A comparison of absorption coefficient values showed these values to be relatively consistent from sample to sample, and independent of the sample growth method.

Radiative transitions involving the (2p2)(3 Pe) metastable autodetaching of H(-)

NASA Technical Reports Server (NTRS)

Jacobs, V. L.; Bhatia, A. K.; Temkin, A.

1974-01-01

The absorption coefficient for the free-bound transition H (ls) + e(-)+ h omega yields H(-)(2 sq p,(3)P(e)) is calculated (together with the differential emission rate for the inverse process) using ls - 2s - 2p close coupling continuum wave functions and a Hylleraas bound state wave function. A maximum in the absorption and emission spectra is found to occur at a photon wavelength of 1219.5 A, which is 2 A closer to the Lyman alpha line than predicted by the calculations of Drake, and is in closer agreement with the stellar absorption feature identified by Heap and Stecher. The free-bound absorption process appears to be a significant source of continuous ultraviolet opacity.

Absorptivity modulation on wavy molten steel surfaces: The influence of laser wavelength and angle of incidence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaplan, A. F. H.

The modulation of the angle-dependent Fresnel absorptivity across wavy molten steel surfaces during laser materials processing, like drilling, cutting, or welding, has been calculated. The absorptivity is strongly altered by the grazing angle of incidence of the laser beam on the processing front. Owing to its specific Brewster-peak characteristics, the 10.64 {mu}m wavelength CO{sub 2}-laser shows an opposite trend with respect to roughness and angle-of-incidence compared to lasers in the wavelength range of 532-1070 nm. Plateaus or rings of Brewster-peak absorptivity can lead to hot spots on a wavy surface, often in close proximity to cold spots caused by shadowmore » domains.« less

All-inorganic colloidal upconversion quantum dots (Conference Presentation)

NASA Astrophysics Data System (ADS)

Oron, Dan; Teitelboim, Ayelet

2017-02-01

Upconversion (UC) is a nonlinear process in which two, or more, long wavelength photons are converted to a shorter wavelength photon. This process is based on sequential absorption of two or more photons, involving metastable, long lived intermediate energy states, thus is not restricted to ultrashort pulsed excitation. Hence, requirements for UC processes are long lived excited states, a ladder like arrangement of energy levels and a mechanism inhibiting cooling of the hot charge carrier. UC holds great promise for bioimaging, enabling to perform multiphoton imaging in scattering specimen at very low powers. Rare-earth-doped nanocrystals, the most commonly used ones for UC, typically require a minimal particle diameter of several tens of nanometers and have a limited action spectrum. Here, we present a novel luminescence upconversion nano-system based on colloidal semiconductor double quantum dots, consisting of a NIR-absorbing component and a visible emitting component separated by a tunneling barrier in a spherical onion-like geometry. These dual near-infrared and visible core/shell/shell PbSe/CdSe/CdS nanocrystals are shown to efficiently upconvert a broad range of NIR wavelengths up to 1.2 microns to visible emission at room temperature, covering a spectral range where there are practically no alternative upconversion systems. The particle diameter is less than ten nanometers, and the synthesis enables versatility and tunability of both the visible emission color and the NIR absorption edge. The physical mechanism for upconversion in this type of structures, as well as potential advances and extensions on this system will be discussed.

Lymphatic absorption of structured triglycerides vs. physical mix in a rat model of fat malabsorption.

PubMed

Tso, P; Lee, T; Demichele, S J

1999-08-01

Comparison was made between the intestinal absorption and lymphatic transport of a randomly interesterified fish oil and medium-chain triglyceride (MCT) structured triglycerides (STG) vs. the physical mix in rat small intestine following ischemia and reperfusion (I/R) injury. Under halothane anesthesia, the superior mesenteric artery (SMA) was occluded for 20 min and then reperfused in I/R rats. The SMA was isolated but not occluded in control rats. In both treatment groups, the mesenteric lymph duct was cannulated and a gastric tube was inserted. Each treatment group received 1 ml of the fish oil-MCT STG or physical mix (7 rats/group) through the gastric tube followed by an infusion of PBS at 3 ml/h for 8 h. Lymph was collected hourly for 8 h. Lymph triglyceride, cholesterol, and decanoic and eicosapentaenoic acids increased rapidly and maintained a significantly higher output (P < 0.01) with STG compared with physical mix in control rats over 8 h. After I/R, lymphatic triglyceride output decreased 50% compared with control. Gastric infusion of STG significantly improved lipid transport by having a twofold higher triglyceride, cholesterol, and decanoic and eicosapentaenoic acids output to lymph compared with its physical mix (P < 0.01). We conclude that STG is absorbed into lymph significantly better than physical mix by both the normal intestine and the intestine injured by I/R.

Mechanical and Physical Properties of Polyester Polymer Concrete Using Recycled Aggregates from Concrete Sleepers

PubMed Central

Carrión, Francisco; Montalbán, Laura; Real, Julia I.

2014-01-01

Currently, reuse of solid waste from disused infrastructures is an important environmental issue to study. In this research, polymer concrete was developed by mixing orthophthalic unsaturated polyester resin, artificial microfillers (calcium carbonate), and waste aggregates (basalt and limestone) coming from the recycling process of concrete sleepers. The variation of the mechanical and physical properties of the polymer concrete (compressive strength, flexural strength, modulus of elasticity, density, and water absorption) was analyzed based on the modification of different variables: nature of the recycled aggregates, resin contents (11 wt%, 12 wt%, and 13 wt%), and particle-size distributions of microfillers used. The results show the influence of these variables on mechanical performance of polymer concrete. Compressive and flexural strength of recycled polymer concrete were improved by increasing amount of polyester resin and by optimizing the particle-size distribution of the microfillers. Besides, the results show the feasibility of developing a polymer concrete with excellent mechanical behavior. PMID:25243213

Drug-nutrient interactions in enteral feeding: a primary care focus.

PubMed

Varella, L; Jones, E; Meguid, M M

1997-06-01

Drug and nutrient interactions are complex and can take many forms, including malabsorption of either the drug or the nutrient component. Some drugs can stimulate or suppress appetite, whereas others can cause nausea and vomiting resulting in inadequate nutritional intake. Absorption of drugs is a complex process that can be affected by the physical characteristics of the gastrointestinal tract (GIT) as well. Depending on the physical properties of a drug, it may be absorbed in a limited area of the GIT or more diffusely along much of the entire length. Many diseases and conditions are also known to affect the GIT either directly or indirectly. Dietary factors also need to be considered when the "food" is an enteral formula. The widespread use of enteral tubes requires that consideration be given to patients receiving both enteral feedings and medication concurrently. The location of a tube in the gastrointestinal tract, as well as the problems involved in crushing and administering solid dosage forms, creates a unique set of problems.

The importance of charge-transfer interactions in determining chromophoric dissolved organic matter (CDOM) optical and photochemical properties.

PubMed

Sharpless, Charles M; Blough, Neil V

2014-04-01

Absorption of sunlight by chromophoric dissolved natural organic matter (CDOM) is environmentally significant because it controls photic zone depth and causes photochemistry that affects elemental cycling and contaminant fate. Both the optics (absorbance and fluorescence) and photochemistry of CDOM display unusual properties that cannot easily be ascribed to a superposition of individual chromophores. These include (i) broad, unstructured absorbance that decreases monotonically well into the visible and near IR, (ii) fluorescence emission spectra that all fall into a single envelope regardless of the excitation wavelength, and (iii) photobleaching and photochemical quantum yields that decrease monotonically with increasing wavelength. In contrast to a simple superposition model, these phenomena and others can be reasonably well explained by a physical model in which charge-transfer interactions between electron donating and accepting chromophores within the CDOM control the optical and photophysical properties. This review summarizes current understanding of the processes underlying CDOM photophysics and photochemistry as well as their physical basis.

An Archival COS Study of Multi-phase Galactic Outflows and Their Dependence on Host Galaxy Properties

NASA Astrophysics Data System (ADS)

Chisholm, John

2013-10-01

Galactic outflows have become vital for understanding galaxy evolution. Outflows have been used to explain the mass-metallicity relation, the star formation history of the universe, and the shape of the baryonic mass function. However, few studies have focused on the basic question of how outflow velocities depend upon the physical properties of their host galaxies. Here we propose an archival project utilizing 52 COS spectra of local star-forming galaxies spanning four decades of star formation rate, and stellar mass. We will preform a self-consistent analysis of trends between galactic properties {star formation rate, stellar mass, specific star formation rate and star formation rate surface density} and outflow velocities measured from interstellar metal absorption lines {e.g., CII 1335}. We will extend this analysis to different gas phases - cold, warm, and hot - to gain a more comprehensive understanding of the physics of multi-phase outflows. The trends we observe will provide insights into the feedback process and will be crucial new benchmarks for simulations.

Mechanical and physical properties of polyester polymer concrete using recycled aggregates from concrete sleepers.

PubMed

Carrión, Francisco; Montalbán, Laura; Real, Julia I; Real, Teresa

2014-01-01

Currently, reuse of solid waste from disused infrastructures is an important environmental issue to study. In this research, polymer concrete was developed by mixing orthophthalic unsaturated polyester resin, artificial microfillers (calcium carbonate), and waste aggregates (basalt and limestone) coming from the recycling process of concrete sleepers. The variation of the mechanical and physical properties of the polymer concrete (compressive strength, flexural strength, modulus of elasticity, density, and water absorption) was analyzed based on the modification of different variables: nature of the recycled aggregates, resin contents (11 wt%, 12 wt%, and 13 wt%), and particle-size distributions of microfillers used. The results show the influence of these variables on mechanical performance of polymer concrete. Compressive and flexural strength of recycled polymer concrete were improved by increasing amount of polyester resin and by optimizing the particle-size distribution of the microfillers. Besides, the results show the feasibility of developing a polymer concrete with excellent mechanical behavior.

A Physical Model of the Proton Radiation Belts of Jupiter inside Europa's Orbit

NASA Astrophysics Data System (ADS)

Nénon, Q.; Sicard, A.; Kollmann, P.; Garrett, H. B.; Sauer, S. P. A.; Paranicas, C.

2018-05-01

A physical model of the Jovian trapped protons with kinetic energies higher than 1 MeV inward of the orbit of the icy moon Europa is presented. The model, named Salammbô, takes into account the radial diffusion process, the absorption effect of the Jovian moons, and the Coulomb collisions and charge exchanges with the cold plasma and neutral populations of the inner Jovian magnetosphere. Preliminary modeling of the wave-particle interaction with electromagnetic ion cyclotron waves near the moon Io is also performed. Salammbô is validated against in situ proton measurements of Pioneer 10, Pioneer 11, Voyager 1, Galileo Probe, and Galileo Orbiter. A prominent feature of the MeV proton intensity distribution in the modeled area is the 2 orders of magnitude flux depletion observed in MeV measurements near the orbit of Io. Our simulations reveal that this is not due to direct interactions with the moon or its neutral environment but results from scattering of the protons by electromagnetic ion cyclotron waves.

Direct measurements of nonlinear absorption and refraction in solutions of phthalocyanines

NASA Technical Reports Server (NTRS)

Wei, T. H.; Hagan, D. J.; Sence, M. J.; Van Stryland, E. W.; Perry, J. W.; Coulter, D. R.

1992-01-01

Direct measurements are reported of the excited singlet-state absorption cross section and the associated nonlinear refractive cross section using picosecond pulses at 532 nm in solutions of phthalocyanine and naphthalocyanine dyes. By monitoring the transmittance and far-field spatial beam distortion for different pulsewidths in the picosecond regime, it is shown that both the nonlinear absorption and refraction are fluence (energy-per-unit-area) rather than irradiance dependent. Thus, excited-state absorption is the dominant nonlinear absorption process, and the observed nonlinear refraction is also due to real population excitation.

Densification and Grain Growth in Polycrystalline Olivine Rocks Synthesized By Evacuated Hot-Pressing

NASA Astrophysics Data System (ADS)

Meyers, C. D.; Kohlstedt, D. L.; Zimmerman, M. E.

2017-12-01

Experiments on laboratory-synthesized olivine-rich rocks form the starting material for many investigations of physical processes in the Earth's upper mantle (e.g., creep behavior, ionic diffusion, and grain growth). Typically, a fit of a constitutive law to experimental data provides a description of the kinetics of a process needed to extrapolate across several orders of magnitude from laboratory to geological timescales. Although grain-size is a critical parameter in determining physical properties such as viscosity, broad disagreement persists amongst the results of various studies of grain growth kinetics in olivine-rich rocks. Small amounts of impurities or porosity dramatically affect the kinetics of grain growth. In this study, we developed an improved method for densifying olivine-rich rocks fabricated from powdered, gem-quality single crystals that involves evacuating the pore space, with the aim of refining measurements of the kinetics of mantle materials. In previous studies, olivine powders were sealed in a metal can and hydrostatically annealed at roughly 300 MPa and 1250 °C. These samples, which appear opaque and milky-green, typically retain a small amount of porosity. Consequently, when annealed at 1 atm, extensive pore growth occurs, inhibiting grain growth. In addition, Fourier-transform infrared and confocal Raman spectroscopy reveal absorption peaks characteristic of CO2 in the pores of conventionally hot-pressed material. To avoid trapping of adsorbed contaminants, we developed an evacuated hot-pressing method, wherein the pore space of powder compacts is vented to vacuum during heating and pressurization. This method produces a highly dense, green-tinted, transparent material. No CO2 absorptions peaks exist in evacuated hot-pressed material. When reheated to annealing temperatures at 1 atm, the evacuated hot-pressed material undergoes limited pore growth and dramatically enhanced grain-growth rates. High-strain deformation experiments on this new material provide new insights into the kinetics of recovery of deformation microstructures.

Antecedents of Absorptive Capacity: A New Model for Developing Learning Processes

ERIC Educational Resources Information Center

Rezaei-Zadeh, Mohammad; Darwish, Tamer K.

2016-01-01

Purpose: The purpose of this paper is to provide an integrated framework to indicate which antecedents of absorptive capacity (AC) influence its learning processes, and to propose testing of this model in future work. Design/methodology/approach Relevant literature into the antecedents of AC was critically reviewed and analysed with the objective…

Ammonia Synthesis at Low Pressure.

PubMed

Cussler, Edward; McCormick, Alon; Reese, Michael; Malmali, Mahdi

2017-08-23

Ammonia can be synthesized at low pressure by the use of an ammonia selective absorbent. The process can be driven with wind energy, available locally in areas requiring ammonia for synthetic fertilizer. Such wind energy is often called "stranded," because it is only available far from population centers where it can be directly used. In the proposed low pressure process, nitrogen is made from air using pressure swing absorption, and hydrogen is produced by electrolysis of water. While these gases can react at approximately 400 °C in the presence of a promoted conventional catalyst, the conversion is often limited by the reverse reaction, which makes this reaction only feasible at high pressures. This limitation can be removed by absorption on an ammine-like calcium or magnesium chloride. Such alkaline metal halides can effectively remove ammonia, thus suppressing the equilibrium constraints of the reaction. In the proposed absorption-enhanced ammonia synthesis process, the rate of reaction may then be controlled not by the chemical kinetics nor the absorption rates, but by the rate of the recycle of unreacted gases. The results compare favorably with ammonia made from a conventional small scale Haber-Bosch process.

Sound absorption of metallic sound absorbers fabricated via the selective laser melting process

NASA Astrophysics Data System (ADS)

Cheng, Li-Wei; Cheng, Chung-Wei; Chung, Kuo-Chun; Kam, Tai-Yan

2017-01-01

The sound absorption capability of metallic sound absorbers fabricated using the additive manufacturing (selective laser melting) method is investigated via both the experimental and theoretical approaches. The metallic sound absorption structures composed of periodic cubic cells were made of laser-melted Ti6Al4 V powder. The acoustic impedance equations with different frequency-independent and frequency-dependent end corrections factors are employed to calculate the theoretical sound absorption coefficients of the metallic sound absorption structures. The calculated sound absorption coefficients are in close agreement with the experimental results for the frequencies ranging from 2 to 13 kHz.

Solvatochromism of 9,10-phenanthrenequinone: An electronic and resonance Raman spectroscopic study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ravi Kumar, Venkatraman; Rajkumar, Nagappan; Umapathy, Siva, E-mail: umapathy@ipc.iisc.ernet.in

2015-01-14

Solvent effects play a vital role in various chemical, physical, and biological processes. To gain a fundamental understanding of the solute-solvent interactions and their implications on the energy level re-ordering and structure, UV-VIS absorption, resonance Raman spectroscopic, and density functional theory calculation studies on 9,10-phenanthrenequinone (PQ) in different solvents of diverse solvent polarity has been carried out. The solvatochromic analysis of the absorption spectra of PQ in protic dipolar solvents suggests that the longest (1n-π{sup 1}*; S{sub 1} state) and the shorter (1π-π{sup 1}*; S{sub 2} state) wavelength band undergoes a hypsochromic and bathochromic shift due to intermolecular hydrogen bondmore » weakening and strengthening, respectively. It also indicates that hydrogen bonding plays a major role in the differential solvation of the S{sub 2} state relative to the ground state. Raman excitation profiles of PQ (400–1800 cm{sup −1}) in various solvents followed their corresponding absorption spectra therefore the enhancements on resonant excitation are from single-state rather than mixed states. The hyperchromism of the longer wavelength band is attributed to intensity borrowing from the nearby allowed electronic transition through vibronic coupling. Computational calculation with C{sub 2ν} symmetry constraint on the S{sub 2} state resulted in an imaginary frequency along the low-frequency out-of-plane torsional modes involving the C=O site and therefore, we hypothesize that this mode could be involved in the vibronic coupling.« less

Biopharmaceutical insights of particulate emulsified systems - a prospective overview.

PubMed

Katamreddy, Jyothshna Devi; Yalavarthi, Prasanna Raju; D, Subba Rao; Battu, Sowjanya; Peesa, Jaya Preethi

2018-05-10

During the twenty-first century, drug discovery is expanding rapidly and a large number of chemical moieties are recognized. Many of them are poorly soluble and hence related biopharmaceutical constraints are to be addressed systematically. Among novel approaches to resolving biopharmaceutical issues, micro- and nano-emulsified systems serve as the best strategy for delivering both hydrophobic and hydrophilic drugs owing to their greater solubilization and transportation capabilities. Of late, the unique physical and biopharmaceutical properties of these liquid isotropic homogenous systems have gained substantive research importance. In addition nano/micro lipid systems share structural and functional similarity with that of the physiological lipids which offer better tolerance ability in the body. In this context, this article provides information on the historical emergence of particulate emulsified systems, importance and rationale of selection of carriers. It also encompasses the physicochemical principles that are responsible for the elevation of therapeutic outcomes of delivery systems. Detailed and schematic absorption of these drug delivery systems is explained here. Gastro-intestinal biochemistry necessary in the understanding of digestion process, lipolytic products formed, micellar structures, enzymes, transporters, mechanism of cell uptake involved after subsequent oral absorption are also emphasized. In addition, this article also explains disposition and pharmacokinetic properties of emulsified systems with real-time therapeutic research outcomes. The influence of biochemical compositions and biopharmaceutical principles on absorption and disposition patterns of ME/NEs was described in the article for the interest of readers and young researchers.

Study of moisture absorption by an organoplastic

NASA Astrophysics Data System (ADS)

Aniskevich, A. N.; Yanson, Yu. O.

1991-07-01

A complex experimental study of the state of sorbed moisture in a unidirectionally reinforced organoplastic was conducted. The methods of TG, DSC, DTA, and NMR showed that moisture absorption in OP is reversible up to 8%, the sorbed moisture does not crystallize in the temperature range from -70 to 0 °C, it is finely dispersely distributed and is in the strongly and weakly bound state, and there is almost no free moisture. The results of the sorption experiments conducted on OP and its structural components: microplastic and EDT-10 binder, in a wide range of temperature-humidity conditions and the data from physical studies showed that moisture absorption in the materials basically takes place by diffusion and is satisfactorily described by a phenomenological model based on the Fick equation. A method of accelerated determination of the sorption characteristics of anisotropic composite materials was developed, using the introduced concept of the fictitious diffusion coefficient and the extrapolation method of determining the limiting moisture content. The features of migration of moisture on the interface in a multiphase system were investigated, and the possibility of successive calculation estimation of the sorption characteristics of an organoplastic at different structural levels was demonstrated: components—unidirectionally reinforced composite—model laminated article. The tested phenomenological model of the sorption process and the experimentally obtained values of the characteristics of the material were the basis for a method of calculation determination of the resource of moisture-proofing properties of a model multilayer article of CM in nonstationary external conditions.

Facile synthesis of a two-photon fluorescent probe based on pyrimidine 2-isothiocyanate and its application in bioimaging.

PubMed

Yang, Jie; Hu, Wei; Li, Huirong; Hou, Hanna; Tu, Yi; Liu, Bo

2018-04-18

Two-photon microscopy imaging has been widely applied in biological imaging, but the development of two-photon absorption probes is obviously lagging behind in the development of imaging technology. In this paper, a two-photon fluorescent probe (1) based on pyrimidine 2-isothiocyanate has been designed and synthesized through a simple method for two-photon biological imaging. Probe 1 was able to couple effectively with the amino groups on biomolecules. To verify the reactivity of the isothiocyanate group on probe 1 and the amine groups on the biomolecules, d-glucosamine was chosen as a model biomolecule to conjugate with probe 1. The result showed that probe 1 could effectively conjugate with d-glucosamine to synthesize probe 2, and the yield of probe 2 was 83%. After conjugating with d-glucosamine, linear absorption spectra, single-photon fluorescence spectra, and two-photon fluorescence spectra of probes 1 and 2 did not present significant changes. Probes 1 and 2 exhibited high fluorescence quantum yields (0.71-0.79) in toluene and chloroform. They also exhibited different photo-physical properties in solvents with different polarities. The two-photon absorption cross-section of probe 1 was 953 GM in toluene. In addition, probe 1 could be effectively conjugated with transferrin, and the conjugated probe (Tf-1) could be transported into Hep G2 cells through a receptor-mediated process for biological imaging. These results demonstrate that such probes are expected to have great potential applications in two-photon fluorescence bioimaging.

X-ray diffraction microscopy on frozen hydrated specimens

NASA Astrophysics Data System (ADS)

Nelson, Johanna

X-rays are excellent for imaging thick samples at high resolution because of their large penetration depth compared to electrons and their short wavelength relative to visible light. To image biological material, the absorption contrast of soft X-rays, especially between the carbon and oxygen K-shell absorption edges, can be utilized to give high contrast, high resolution images without the need for stains or labels. Because of radiation damage and the desire for high resolution tomography, live cell imaging is not feasible. However, cells can be frozen in vitrified ice, which reduces the effect of radiation damage while maintaining their natural hydrated state. X-ray diffraction microscopy (XDM) is an imaging technique which eliminates the limitations imposed by current focusing optics simply by removing them entirely. Far-field coherent diffraction intensity patterns are collected on a pixelated detector allowing every scattered photon to be collected within the limits of the detector's efficiency and physical size. An iterative computer algorithm is then used to invert the diffraction intensity into a real space image with both absorption and phase information. This technique transfers the emphasis away from fabrication and alignment of optics, and towards data processing. We have used this method to image a pair of freeze-dried, immuno-labeled yeast cells to the highest resolution (13 nm) yet obtained for a whole eukaryotic cell. We discuss successes and challenges in working with frozen hydrated specimens and efforts aimed at high resolution imaging of vitrified eukaryotic cells in 3D.

Wind-embedded shocks in FASTWIND: X-ray emission and K-shell absorption

NASA Astrophysics Data System (ADS)

Carneiro, L. P.; Puls, J.; Sundqvist, J. O.; Hoffmann, T. L.

2017-11-01

EUV and X-ray radiation emitted from wind-embedded shocks can affect the ionization balance in the outer atmospheres of massive stars, and can also be the mechanism responsible for producing highly ionized atoms detected in the wind UV spectra. To investigate these processes, we implemented the emission from wind-embedded shocks and related physics into our atmosphere/spectrum synthesis code FASTWIND. We also account for the high energy absorption of the cool wind, by adding important K-shell opacities. Various tests justfying our approach have been described by Carneiro+(2016, A&A 590, A88). In particular, we studied the impact of X-ray emission on the ionization balance of important elements. In almost all the cases, the lower ionization stages (O iv, N iv, P v) are depleted and the higher stages (N v, O v, O vi) become enhanced. Moreover, also He lines (in particular He ii 1640 and He ii 4686) can be affected as well. Finally, we carried out an extensive discussion of the high-energy mass absorption coefficient, κν, regarding its spatial variation and dependence on T eff. We found that (i) the approximation of a radially constant κν can be justified for r >= 1.2R * and λ <= 18 Å, and also for many models at longer wavelengths. (ii) In order to estimate the actual value of this quantity, however, the He ii background needs to be considered from detailed modeling.

Analyzing and Post-modelling the High Speed Images of a Wavy Laser Induced Boiling Front

NASA Astrophysics Data System (ADS)

Matti, R. S.; Kaplan, A. F. H.

The boiling front in laser materials processing like remote fusion cutting, keyhole welding or drilling can nowadays be recorded by high speed imaging. It was recently observed that bright waves flow down the front. Several complex physical mechanisms are associated with a stable laser-induced boiling front, like beam absorption, shadowing, heating, ablation pressure, fluid flow, etc. The evidence of dynamic phenomena from high speed imaging is closely linked to these phenomena. As a first step, the directly visible phenomena were classified and analyzed. This has led to the insight that the appearance of steady flow of the bright front peaks is a composition of many short flashing events of 20-50 μs duration, though composing a rather constant melt film flow downwards. Five geometrical front shapes of bright and dark domains were categorized, for example long inclined dark valleys. In addition, the special top and bottom regions of the front are distinguished. As a second step, a new method of post-modelling based on the greyscale variation of the images was applied, to approximately reconstruct the topology of the wavy front and subsequently to calculate the absorption across the front. Despite certain simplifications this kind of analysis provides a variety of additional information, including statistical analysis. In particular, the model could show the sensitivity of front waves to the formation of shadow domains and the robustness of fiber lasers to keep most of an irradiated steel surface in an absorptivity window between 35 to 43%.

Molten salt CO2 capture and electro-transformation (MSCC-ET) into capacitive carbon at medium temperature: effect of the electrolyte composition.

PubMed

Deng, Bowen; Chen, Zhigang; Gao, Muxing; Song, Yuqiao; Zheng, Kaiyuan; Tang, Juanjuan; Xiao, Wei; Mao, Xuhui; Wang, Dihua

2016-08-15

Electrochemical transformation of CO2 into functional materials or fuels (i.e., carbon, CO) in high temperature molten salts has been demonstrated as a promising way of carbon capture, utilisation and storage (CCUS) in recent years. In a view of continuous operation, the electrolysis process should match very well with the CO2 absorption kinetics. At the same time, in consideration of the energy efficiency, a molten salt electrochemical cell running at lower temperature is more beneficial to a process powered by the fluctuating renewable electricity from solar/wind farms. Ternary carbonates (Li : Na : K = 43.5 : 31.5 : 25.0) and binary chlorides (Li : K = 58.5 : 41.5), two typical kinds of eutectic melt with low melting points and a wide electrochemical potential window, could be the ideal supporting electrolyte for the molten salt CO2 capture and electro-transformation (MSCC-ET) process. In this work, the CO2 absorption behaviour in Li2O/CaO containing carbonates and chlorides were investigated on a home-made gas absorption testing system. The electrode processes as well as the morphology and properties of carbon obtained in different salts are compared to each other. It was found that the composition of molten salts significantly affects the absorption of CO2, electrode processes and performance of the product. Furthermore, the relationship between the absorption and electro-transformation kinetics are discussed based on the findings.

Low-frequency radio absorption in Cassiopeia A

NASA Astrophysics Data System (ADS)

Arias, M.; Vink, J.; de Gasperin, F.; Salas, P.; Oonk, J. B. R.; van Weeren, R. J.; van Amesfoort, A. S.; Anderson, J.; Beck, R.; Bell, M. E.; Bentum, M. J.; Best, P.; Blaauw, R.; Breitling, F.; Broderick, J. W.; Brouw, W. N.; Brüggen, M.; Butcher, H. R.; Ciardi, B.; de Geus, E.; Deller, A.; van Dijk, P. C. G.; Duscha, S.; Eislöffel, J.; Garrett, M. A.; Grießmeier, J. M.; Gunst, A. W.; van Haarlem, M. P.; Heald, G.; Hessels, J.; Hörandel, J.; Holties, H. A.; van der Horst, A. J.; Iacobelli, M.; Juette, E.; Krankowski, A.; van Leeuwen, J.; Mann, G.; McKay-Bukowski, D.; McKean, J. P.; Mulder, H.; Nelles, A.; Orru, E.; Paas, H.; Pandey-Pommier, M.; Pandey, V. N.; Pekal, R.; Pizzo, R.; Polatidis, A. G.; Reich, W.; Röttgering, H. J. A.; Rothkaehl, H.; Schwarz, D. J.; Smirnov, O.; Soida, M.; Steinmetz, M.; Tagger, M.; Thoudam, S.; Toribio, M. C.; Vocks, C.; van der Wiel, M. H. D.; Wijers, R. A. M. J.; Wucknitz, O.; Zarka, P.; Zucca, P.

2018-05-01

Context. Cassiopeia A is one of the best-studied supernova remnants. Its bright radio and X-ray emission is due to shocked ejecta. Cas A is rather unique in that the unshocked ejecta can also be studied: through emission in the infrared, the radio-active decay of 44Ti, and the low-frequency free-free absorption caused by cold ionised gas, which is the topic of this paper. Aims: Free-free absorption processes are affected by the mass, geometry, temperature, and ionisation conditions in the absorbing gas. Observations at the lowest radio frequencies can constrain a combination of these properties. Methods: We used Low Frequency Array (LOFAR) Low Band Antenna observations at 30-77 MHz and Very Large Array (VLA) L-band observations at 1-2 GHz to fit for internal absorption as parametrised by the emission measure. We simultaneously fit multiple UV-matched images with a common resolution of 17″ (this corresponds to 0.25 pc for a source at the distance of Cas A). The ample frequency coverage allows us separate the relative contributions from the absorbing gas, the unabsorbed front of the shell, and the absorbed back of the shell to the emission spectrum. We explored the effects that a temperature lower than the 100-500 K proposed from infrared observations and a high degree of clumping can have on the derived physical properties of the unshocked material, such as its mass and density. We also compiled integrated radio flux density measurements, fit for the absorption processes that occur in the radio band, and considered their effect on the secular decline of the source. Results: We find a mass in the unshocked ejecta of M = 2.95 ± 0.48 M⊙ for an assumed gas temperatureof T = 100 K. This estimate is reduced for colder gas temperatures and, most significantly, if the ejecta are clumped. We measure the reverse shock to have a radius of 114″± 6″ and be centred at 23:23:26, +58:48:54 (J2000). We also find that a decrease in the amount of mass in the unshocked ejecta (as more and more material meets the reverse shock and heats up) cannot account for the observed low-frequency behaviour of the secular decline rate. Conclusions: To reconcile our low-frequency absorption measurements with models that reproduce much of the observed behaviour in Cas A and predict little mass in the unshocked ejecta, the ejecta need to be very clumped or the temperature in the cold gas needs to be low ( 10 K). Both of these options are plausible and can together contribute to the high absorption value that we find. The 9 LBA narrow-band images and the VLA image are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/612/A110

Carbon X-ray absorption in the local ISM: fingerprints in X-ray Novae spectra

NASA Astrophysics Data System (ADS)

Gatuzz, Efraín; Ness, J.-U.; Gorczyca, T. W.; Hasoglu, M. F.; Kallman, Timothy R.; García, Javier A.

2018-06-01

We present a study of the C K-edge using high-resolution LETGS Chandra spectra of four novae during their super-soft-source (SSS) phase. We identified absorption lines due to C II Kα, C III Kα and C III Kβ resonances. We used these astronomical observations to perform a benchmarking of the atomic data, which involves wavelength shifts of the resonances and photoionization cross-sections. We used improved atomic data to estimate the C II and C III column densities. The absence of physical shifts for the absorption lines, the consistence of the column densities between multiple observations and the high temperature required for the SSS nova atmosphere modeling support our conclusion about an ISM origin of the respective absorption lines. Assuming a collisional ionization equilibrium plasma the maximum temperature derived from the ratio of C II/C III column densities of the absorbers correspond to Tmax < 3.05 × 104 K.

Galactic Outflows and Their Correlation with Galaxy Properties at 0.8 < z < 1.6

NASA Astrophysics Data System (ADS)

Whiting, Lindsey M.

Out. ows have been shown to be ubiquitous in galaxies between z = 1 and z=2, and many models and observations have attempted to correlate the absorption line. properties of these out. ows with morphological characteristics of their host galaxies. In this study, we examined the spectra of 71 galaxies with redshifts 1< z<2, paying. particular attention to the FeII and MgII absorption lines. We plotted the equivalent. width, velocity, and maximum velocity of the absorption features against various. physical properties of the galaxies, obtained from catalogues created by Skelton et. al., (2014) and van der Wel et al., (2012). We conrmed the presence of out. ows in. our galaxy sample, and found a signicant trend between the equivalent width and. star formation rate - out. owing gas has stronger absorption lines in galaxies with. higher star formation rates.

Ultra-Thin Dual-Band Polarization-Insensitive and Wide-Angle Perfect Metamaterial Absorber Based on a Single Circular Sector Resonator Structure

NASA Astrophysics Data System (ADS)

Luo, Hao; Cheng, Yong Zhi

2018-01-01

We present a simple design for an ultra-thin dual-band polarization-insensitive and wide-angle perfect metamaterial absorber (PMMA) based on a single circular sector resonator structure (CSRS). Both simulation and experimental results reveal that two resonance peaks with average absorption above 99% can be achieved. The dual-band PMMA is ultra-thin with total thickness of 0.5 mm, which is

Cross-phase modulation-induced spectral broadening in silicon waveguides.

PubMed

Zhang, Yanbing; Husko, Chad; Lefrancois, Simon; Rey, Isabella H; Krauss, Thomas F; Schröder, Jochen; Eggleton, Benjamin J

2016-01-11

We analytically and experimentally investigate cross-phase modulation (XPM) in silicon waveguides. In contrast to the well known result in pure Kerr media, the spectral broadening ratio of XPM to self-phase modulation is not two in the presence of either two-photon absorption (TPA) or free carriers. The physical origin of this change is different for each effect. In the case of TPA, this nonlinear absorption attenuates and slightly modifies the pulse shape due to differential absorption in the pulse peak and wings. When free carriers are present two different mechanisms modify the dynamics. First, free-carrier absorption performs a similar role to TPA, but is additionally asymmetric due to the delayed free-carrier response. Second, free-carrier dispersion induces an asymmetric blue phase shift which competes directly with the symmetric Kerr-induced XPM red shift. We confirm this analysis with pump-probe experiments in a silicon photonic crystal waveguide.

Critical power for self-focusing of optical beam in absorbing media

NASA Astrophysics Data System (ADS)

Qi, Pengfei; Zhang, Lin; Lin, Lie; Zhang, Nan; Wang, Yan; Liu, Weiwei

2018-04-01

Self-focusing effects are of central importance for most nonlinear optical effects. The critical power for self-focusing is commonly investigated theoretically without considering a material’s absorption. Although this is practicable for various materials, investigating the critical power for self-focusing in media with non-negligible absorption is also necessary, because this is the situation usually met in practice. In this paper, the simple analytical expressions describing the relationships among incident power, absorption coefficient and focal position are provided by a simple physical model based on the Fermat principle. Expressions for the absorption dependent critical power are also derived; these can play important roles in experimental and applied research on self-focusing-related nonlinear optical phenomena in absorbing media. Numerical results, based on the nonlinear wave equation—and which can predict experimental results perfectly—are also presented, and agree quantitatively with the analytical results proposed in this paper.

Spectroscopy of T Tauri stars with UVES. Observations and analysis of RU Lup

NASA Astrophysics Data System (ADS)

Stempels, H. C.; Piskunov, N.

2002-08-01

We present the first results of our observations of classical T Tauri Stars with UVES/VLT. The data consists of high signal-to-noise (ge 150) and high spectral resolution (R ~ 60 000) spectra. A large simultaneous wavelength coverage throughout most of the visible spectrum and comparatively short integration times allow us to study variability on short time-scales, using a number of diagnostics reflecting a wide range of physical processes. In particular we concentrate on the properties and geometry of the accretion process in the strongly accreting and highly variable CTTS RU Lup. We use the evolution of the level of veiling, the shapes of absorption and emission lines, and correlations between these diagnostics, to make new measurements of the fundamental stellar parameters as well as constraints on the accretion process and its geometry. We also derive the shortest time-scale of incoherent changes, which has implications for the nature of the accretion process in RU Lup. Based on observations collected at the European Southern Observatory, Chile (proposal 65.I-0404).

AMMONIA ABSORPTION/AMMONIUM BISULFATE REGENERATION PILOT PLANT FOR FLUE GAS DESULFURIZATION

EPA Science Inventory

The report gives results of a pilot-plant study of the ammonia absorption/ammonium bisulfate regeneration process for removing SO2 from the stack gas of coal-fired power plants. Data were developed on the effects of such operating variable in the absorption of SO2 by ammoniacal l...

Impacts of Combustion Conditions and Photochemical Processing on the Light Absorption of Biomass Combustion Aerosol.

PubMed

Martinsson, J; Eriksson, A C; Nielsen, I Elbæk; Malmborg, V Berg; Ahlberg, E; Andersen, C; Lindgren, R; Nyström, R; Nordin, E Z; Brune, W H; Svenningsson, B; Swietlicki, E; Boman, C; Pagels, J H

2015-12-15

The aim was to identify relationships between combustion conditions, particle characteristics, and optical properties of fresh and photochemically processed emissions from biomass combustion. The combustion conditions included nominal and high burn rate operation and individual combustion phases from a conventional wood stove. Low temperature pyrolysis upon fuel addition resulted in "tar-ball" type particles dominated by organic aerosol with an absorption Ångström exponent (AAE) of 2.5-2.7 and estimated Brown Carbon contributions of 50-70% to absorption at the climate relevant aethalometer-wavelength (520 nm). High temperature combustion during the intermediate (flaming) phase was dominated by soot agglomerates with AAE 1.0-1.2 and 85-100% of absorption at 520 nm attributed to Black Carbon. Intense photochemical processing of high burn rate flaming combustion emissions in an oxidation flow reactor led to strong formation of Secondary Organic Aerosol, with no or weak absorption. PM1 mass emission factors (mg/kg) of fresh emissions were about an order of magnitude higher for low temperature pyrolysis compared to high temperature combustion. However, emission factors describing the absorption cross section emitted per kg of fuel consumed (m(2)/kg) were of similar magnitude at 520 nm for the diverse combustion conditions investigated in this study. These results provide a link between biomass combustion conditions, emitted particle types, and their optical properties in fresh and processed plumes which can be of value for source apportionment and balanced mitigation of biomass combustion emissions from a climate and health perspective.

Process for separating carbon dioxide from flue gas using sweep-based membrane separation and absorption steps

DOEpatents

Wijmans, Johannes G.; Baker, Richard W.; Merkel, Timothy C.

2012-08-21

A gas separation process for treating flue gases from combustion processes, and combustion processes including such gas separation. The invention involves routing a first portion of the flue gas stream to be treated to an absorption-based carbon dioxide capture step, while simultaneously flowing a second portion of the flue gas across the feed side of a membrane, flowing a sweep gas stream, usually air, across the permeate side, then passing the permeate/sweep gas to the combustor.

Time-resolved study of femtosecond laser induced micro-modifications inside transparent brittle materials

NASA Astrophysics Data System (ADS)

Hendricks, F.; Matylitsky, V. V.; Domke, M.; Huber, Heinz P.

2016-03-01

Laser processing of optically transparent or semi-transparent, brittle materials is finding wide use in various manufacturing sectors. For example, in consumer electronic devices such as smartphones or tablets, cover glass needs to be cut precisely in various shapes. The unique advantage of material processing with femtosecond lasers is efficient, fast and localized energy deposition in nearly all types of solid materials. When an ultra-short laser pulse is focused inside glass, only the localized region in the neighborhood of the focal volume absorbs laser energy by nonlinear optical absorption. Therefore, the processing volume is strongly defined, while the rest of the target stays unaffected. Thus ultra-short pulse lasers allow cutting of the chemically strengthened glasses such as Corning Gorilla glass without cracking. Non-ablative cutting of transparent, brittle materials, using the newly developed femtosecond process ClearShapeTM from Spectra-Physics, is based on producing a micron-sized material modification track with well-defined geometry inside. The key point for development of the process is to understand the induced modification by a single femtosecond laser shot. In this paper, pump-probe microscopy techniques have been applied to study the defect formation inside of transparent materials, namely soda-lime glass samples, on a time scale between one nanosecond to several tens of microseconds. The observed effects include acoustic wave propagation as well as mechanical stress formation in the bulk of the glass. Besides better understanding of underlying physical mechanisms, our experimental observations have enabled us to find optimal process parameters for the glass cutting application and lead to better quality and speed for the ClearShapeTM process.

Can the tricyanomethanide anion improve CO2 absorption by acetate-based ionic liquids?

PubMed

Lepre, L F; Szala-Bilnik, J; Pison, L; Traïkia, M; Pádua, A A H; Ando, R A; Costa Gomes, M F

2017-05-17

Carbon dioxide absorption by mixtures of two ionic liquids with a common cation-1-butyl-3-methylimidazolium acetate, [C 4 C 1 Im][OAc], and 1-butyl-3-methylimidazolium tricyanomethanide, [C 4 C 1 Im][C(CN) 3 ]-was determined experimentally at pressures below atmospheric pressure as a function of temperature between 303 K and 343 K, and at 303 K as a function of pressure up to 10 bar. It is observed that the absorption of carbon dioxide decreases with increasing tricyanomethanide anion concentration and with increasing temperature, showing a maximum of 0.4 mole fraction of carbon dioxide in pure [C 4 C 1 Im][OAc] at 303 K. At this temperature, the CO 2 absorption in the mixtures [C 4 C 1 Im][OAc] (1-x) [C(CN) 3 ] x is approximately the mole-fraction average of that in the pure ionic liquids. By applying an appropriate thermodynamic treatment, after identification of the species in solution, it was possible to calculate both the equilibrium constant, K eq , and Henry's law constant, K H , in the different mixtures studied thus obtaining an insight into the relative contribution of chemical and physical absorption of the gas. It is shown that chemical sorption proceeds through a 1 : 2 stoichiometry between CO 2 and acetate-based ionic liquid. The presence of the C(CN) 3 - anion does not significantly affect the chemical reaction of the gas with the solvent (K eq = 75 ± 2 at 303 K) but leads to lower Henry's law constants (from K H = 77.8 ± 0.6 bar to K H = 49.5 ± 0.5 bar at 303 K), thus pointing towards larger physical absorption of the gas. The tricyanomethanide anion considerably improves the mass transfer by increasing the fluidity of the absorbent as proven by the larger diffusivities of all the ions when the concentration of the C(CN) 3 - anion increases in the mixtures.

A theoretical/experimental program to develop active optical pollution sensors

NASA Technical Reports Server (NTRS)

Mills, F. S.; Blais, R. N.; Kindle, E. C.

1977-01-01

Light detection and ranging (LIDAR) technology was applied to the assessment of air quality, and its usefulness was evaluated by actual field tests. Necessary hardware was successfully constructed and operated in the field. Measurements of necessary physical parameters, such as SO2 absorption coefficients were successfully completed and theoretical predictions of differential absorption performance were reported. Plume modeling improvements were proposed. A full scale field test of equipment, data analysis and auxiliary data support was conducted in Maryland during September 1976.

Narrow absorption lines with two observations from the Sloan Digital Sky Survey

NASA Astrophysics Data System (ADS)

Chen, Zhi-Fu; Gu, Qiu-Sheng; Chen, Yan-Mei; Cao, Yue

2015-07-01

We assemble 3524 quasars from the Sloan Digital Sky Survey (SDSS) with repeated observations to search for variations of the narrow C IV λ λ 1548,1551 and Mg II λ λ 2796,2803 absorption doublets in spectral regions shortward of 7000 Å in the observed frame, which corresponds to time-scales of about 150-2643 d in the quasar rest frame. In these quasar spectra, we detect 3580 C IV absorption systems with zabs = 1.5188-3.5212 and 1809 Mg II absorption systems with zabs = 0.3948-1.7167. In term of the absorber velocity (β) distribution in the quasar rest frame, we find a substantial number of C IV absorbers with β < 0.06, which might be connected to absorption of quasar outflows. The outflow absorption peaks at υ ≈ 2000 km s^{-1} and drops rapidly below this peak value. Among 3580 C IV absorption systems, 52 systems (˜1.5 per cent) show obvious variations in equivalent widths in the absorber rest frame (Wr): 16 enhanced, 16 emerged, 12 weakened and 8 disappeared systems, respectively. We find that changes in Wrλ1548 are related neither to the time-scales of the two SDSS observations nor to absorber velocities in the quasar rest frame. Variable absorption in low-ionization species is important to constrain the physical conditions of the absorbing gas. There are two variable Mg II absorption systems measured from SDSS spectra detected by Hacker et al. However, in our Mg II absorption sample, we find that neither shows variable absorption with confident levels of >4σ for λ2796 lines and >3σ for λ2803 lines.

Influence of hole shape on sound absorption of underwater anechoic layers

NASA Astrophysics Data System (ADS)

Ye, Changzheng; Liu, Xuewei; Xin, Fengxian; Lu, Tian Jian

2018-07-01

A theoretical model is established to evaluate the sound absorption performance of underwater anechoic layers containing periodically distributed axial holes. Based on the concept for homogenized equivalent layer and on the theory of wave propagation in viscoelastic cylindrical tubes, the transfer function method is used to obtain the absorption coefficient of the anechoic layer adhered on the rigid plate. Three different types of axial holes are considered, the cylindrical, the conical and the horn shaped one. Results obtained with full finite element simulations are used to validate the model predictions. For each hole type, the vibration characteristics of the anechoic layer as well as the propagation of longitudinal and transverse waves in the layer are analyzed in detail to explore the physical mechanisms underlying its absorption performance. Furthermore, a three-dimensional finite element model for oblique incidence is developed to study the effect of hole shape at different incidence angles. The results show that two new absorption peaks appear since the oblique incidence excites two horizontal modes. Among the three hole types, the horn one achieves the best absorption performance at relatively low frequencies both in normal incidence and in oblique incidence.

A Novel Acoustic Sensor Approach to Classify Seeds Based on Sound Absorption Spectra

PubMed Central

Gasso-Tortajada, Vicent; Ward, Alastair J.; Mansur, Hasib; Brøchner, Torben; Sørensen, Claus G.; Green, Ole

2010-01-01

A non-destructive and novel in situ acoustic sensor approach based on the sound absorption spectra was developed for identifying and classifying different seed types. The absorption coefficient spectra were determined by using the impedance tube measurement method. Subsequently, a multivariate statistical analysis, i.e., principal component analysis (PCA), was performed as a way to generate a classification of the seeds based on the soft independent modelling of class analogy (SIMCA) method. The results show that the sound absorption coefficient spectra of different seed types present characteristic patterns which are highly dependent on seed size and shape. In general, seed particle size and sphericity were inversely related with the absorption coefficient. PCA presented reliable grouping capabilities within the diverse seed types, since the 95% of the total spectral variance was described by the first two principal components. Furthermore, the SIMCA classification model based on the absorption spectra achieved optimal results as 100% of the evaluation samples were correctly classified. This study contains the initial structuring of an innovative method that will present new possibilities in agriculture and industry for classifying and determining physical properties of seeds and other materials. PMID:22163455

Enhanced laser-energy coupling to dense plasmas driven by recirculating electron currents

NASA Astrophysics Data System (ADS)

Gray, R. J.; Wilson, R.; King, M.; Williamson, S. D. R.; Dance, R. J.; Armstrong, C.; Brabetz, C.; Wagner, F.; Zielbauer, B.; Bagnoud, V.; Neely, D.; McKenna, P.

2018-03-01

The absorption of laser energy and dynamics of energetic electrons in dense plasma is fundamental to a range of intense laser-driven particle and radiation generation mechanisms. We measure the total reflected and scattered laser energy as a function of intensity, distinguishing between the influence of pulse energy and focal spot size on total energy absorption, in the interaction with thin foils. We confirm a previously published scaling of absorption with intensity by variation of laser pulse energy, but find a slower scaling when changing the focal spot size. 2D particle-in-cell simulations show that the measured differences arise due to energetic electrons recirculating within the target and undergoing multiple interactions with the laser pulse, which enhances absorption in the case of large focal spots. This effect is also shown to be dependent on the laser pulse duration, the target thickness and the electron beam divergence. The parameter space over which this absorption enhancement occurs is explored via an analytical model. The results impact our understanding of the fundamental physics of laser energy absorption in solids and thus the development of particle and radiation sources driven by intense laser–solid interactions.

Removal of Sulfur Dioxide from Flue Gas Using the Sludge Sodium Humate

PubMed Central

Hu, Guoxin

2013-01-01

This study shows the ability of sodium humate from alkaline treatment sludge on removing sulfur dioxide (SO2) in the simulated flue gas. Experiments were conducted to examine the effect of various operating parameters, like the inlet SO2 concentration or temperature or O2, on the SO2 absorption efficiency and desulfurization time in a lab-scale bubbling reactor. The sludge sodium humate in the supernatant after alkaline sludge treatment shows great performance in SO2 absorption, and such efficiency can be maintained above 98% with 100 mL of this absorption solution at 298 K (flue gas rate of 0.12 m3/h). The highest SO2 absorption by 1.63 g SHA-Na is 0.946 mmol in the process, which is translated to 0.037 g SO2 g−1 SHA-Na. The experimental results indicate that the inlet SO2 concentration slightly influences the SO2 absorption efficiency and significantly influences the desulfurization time. The pH of the absorption solution should be above 3.5 in this process in order to make an effective desulfurization. The products of this process were characterized by Fourier transform infrared spectroscopy and X-ray diffraction. It can be seen that the desulfurization products mainly contain sludge humic acid sediment, which can be used as fertilizer components. PMID:24453875

Photobiology of Symbiodinium revisited: bio-physical and bio-optical signatures

NASA Astrophysics Data System (ADS)

Hennige, S. J.; Suggett, D. J.; Warner, M. E.; McDougall, K. E.; Smith, D. J.

2009-03-01

Light is often the most abundant resource within the nutrient-poor waters surrounding coral reefs. Consequently, zooxanthellae ( Symbiodinium spp.) must continually photoacclimate to optimise productivity and ensure coral success. In situ coral photobiology is becoming dominated by routine assessments using state-of-the-art non-invasive bio-optical or chlorophyll a fluorescence (bio-physical) techniques. Multiple genetic types of Symbiodinium are now known to exist; however, little focus has been given as to how these types differ in terms of characteristics that are observable using these techniques. Therefore, this investigation aimed to revisit and expand upon a pivotal study by Iglesias-Prieto and Trench (1994) by comparing the photoacclimation characteristics of different Symbiodinium types based on their bio-physical (chlorophyll a fluorescence, reaction centre counts) and bio-optical (optical absorption, pigment concentrations) ‘signatures’. Signatures described here are unique to Symbiodinium type and describe phenotypic responses to set conditions, and hence are not suitable to describe taxonomic structure of in hospite Symbiodinium communities. In this study, eight Symbiodinium types from clades and sub-clades (A-B, F) were grown under two PFDs (Photon Flux Density) and examined. The photoacclimation response by Symbiodinium was highly variable between algal types for all bio-physical and for many bio-optical measurements; however, a general preference to modifying reaction centre content over effective antennae-absorption was observed. Certain bio-optically derived patterns, such as light absorption, were independent of algal type and, when considered per photosystem, were matched by reaction centre stoichiometry. Only by better understanding genotypic and phenotypic variability between Symbiodinium types can future studies account for the relative taxonomic and physiological contribution by Symbiodinium to coral acclimation.

Effects of Cross-Shelf Physical Forcing on Satellite Bio-Optical Properties

NASA Astrophysics Data System (ADS)

Ladner, S. D.; Teague, W. J.; Mitchell, D. A.; Goode, W. A.; Gould, R. W.; Arnone, R. A.

2005-05-01

Our goal is to determine the effects of cross-shelf physical forcing on the optical properties in the northern Gulf of Mexico using in situ optical profiles and surface ocean color satellite images from SeaWiFS. The Naval Research Laboratory at Stennis Space Center is conducting an extensive monitoring program in the Northeast Gulf of Mexico west of the Desoto Canyon. During the Slope to Shelf Energetics and Exchange Dynamics (SEED) project, 14 bottom mounted Acoustic Doppler Current Profilers (ADCP's) were deployed from May-December 2004 along the shelf break at depths ranging from 60 to 1000 meters to improve understanding of cross-shelf exchange processes. Analysis of the May current data indicate abnormal events, including 30 cm/s off-shelf currents throughout the water column and a 3° Celsius elevation in bottom temperature. Coincident optical profiles were collected in May (absorption, scattering coefficients) and are compared with currents and physical properties (temperature, salinity). Similar subsurface abnormalities with stronger currents occurred in September during the passing of Hurricane Ivan over the mooring sites. We will show a time series of near-surface current speeds and their effect on the surface-satellite optical properties over the entire SEED sampling exercise.

Lipid-associated Oral Delivery: Mechanisms and Analysis of Oral Absorption Enhancement

PubMed Central

Rezhdo, Oljora; Speciner, Lauren; Carrier, Rebecca L.

2016-01-01

The majority of newly discovered oral drugs are poorly water soluble, and co-administration with lipids has proven effective in significantly enhancing bioavailability of some compounds with low aqueous solubility. Yet, lipid-based delivery technologies have not been widely employed in commercial oral products. Lipids can impact drug transport and fate in the gastrointestinal (GI) tract through multiple mechanisms including enhancement of solubility and dissolution kinetics, enhancement of permeation through the intestinal mucosa, and triggering drug precipitation upon lipid emulsion depletion (e.g., by digestion). The effect of lipids on drug absorption is currently not quantitatively predictable, in part due to the multiple complex dynamic processes that can be impacted by lipids. Quantitative mechanistic analysis of the processes significant to lipid system function and overall impact on drug absorption can aid understanding of drug-lipid interactions in the GI tract and exploitation of such interactions to achieve optimal lipid-based drug delivery. In this review, we discuss the impact of co-delivered lipids and lipid digestion on drug dissolution, partitioning, and absorption in the context of the experimental tools and associated kinetic expressions used to study and model these processes. The potential benefit of a systems-based consideration of the concurrent multiple dynamic processes occurring upon co-dosing lipids and drugs to predict the impact of lipids on drug absorption and enable rational design of lipid-based delivery systems is presented. PMID:27520734

Broadband superior electromagnetic absorption of a discrete-structure microwave coating

NASA Astrophysics Data System (ADS)

Duan, Yuping; Xi, Qun; Liu, Wei; Wang, Tongmin

2016-10-01

A method of improving the electromagnetic (EM) absorption property of conventional microwave absorber (CMA) is proposed here. The structural design process was mainly concerned with systematic analysis and research into the impedance matching characteristic and induced current. By processing a CMA-carbonyl-iron powder (CIP) coating into many isolated regions, the discrete-structure microwave absorber (DMA) had a much better absorption property than the corresponding CMA. When the thickness was only 2.0 mm and the component content was 33 wt%, the loss of reflection was less than -10 dB shifted from 6-7 GHz to 7-13 GHz and the loss of minimum reflection decreased from 12.5 dB lost to 32 dB lost through a discrete-structure process. The microwave absorption properties of coatings with different component contents and thicknesses were investigated. The minimum reflection peaks tended to shift towards the lower frequency region as CIP content or coating thickness increased. By adjusting these three factors, a high-performance broadband absorber was produced.

Up-conversion fluorescence: noncoherent excitation by sunlight.

PubMed

Baluschev, S; Miteva, T; Yakutkin, V; Nelles, G; Yasuda, A; Wegner, G

2006-10-06

We demonstrate up-conversion of noncoherent sunlight realized by ultralow excitation intensity. The bimolecular up-conversion process in our systems relies on the presence of a metastable triplet excited state, and thus has dramatically different photophysical characteristics relative to the other known methods for photon up-conversion (two-photon absorption, parametric processes, second harmonic generation, sequential multiphoton absorption, etc.).

Investigation of quadratic electro-optic effects and electro-absorption process in GaN/AlGaN spherical quantum dot

PubMed Central

2014-01-01

Quadratic electro-optic effects (QEOEs) and electro-absorption (EA) process in a GaN/AlGaN spherical quantum dot are theoretically investigated. It is found that the magnitude and resonant position of third-order nonlinear optical susceptibility depend on the nanostructure size and aluminum mole fraction. With increase of the well width and barrier potential, quadratic electro-optic effect and electro-absorption process nonlinear susceptibilities are decreased and blueshifted. The results show that the DC Kerr effect in this case is much larger than that in the bulk case. Finally, it is observed that QEOEs and EA susceptibilities decrease and broaden with the decrease of relaxation time. PMID:24646318

Research on disposal of copper(II)-containing wastewater by secondary strontium residue

NASA Astrophysics Data System (ADS)

Qing, Duowen; Xu, Longjun; Cui, Caixi

2018-01-01

Secondary strontium residue (SSR) was used as absorbent to remove Cu2+ in solution and the effects of experimental conditions on absorption of Cu2+ were investigated. The results showed that the absorption process reached balance in around 40 min. The absorption capacity achieved the maximum when PH value reached 6, and the maximum adsorption of Cu2+-containing wastewater by secondary strontium residue was 5.46 mg/g. Removal ratio of Cu2+ was in relation to initial concentration of Cu2+ in solution. Adsorptive process tallied with Langmuir Isothermal adsorption model.

Capillary absorption spectrometer and process for isotopic analysis of small samples

DOEpatents

Alexander, M. Lizabeth; Kelly, James F.; Sams, Robert L.; Moran, James J.; Newburn, Matthew K.; Blake, Thomas A.

2016-03-29

A capillary absorption spectrometer and process are described that provide highly sensitive and accurate stable absorption measurements of analytes in a sample gas that may include isotopologues of carbon and oxygen obtained from gas and biological samples. It further provides isotopic images of microbial communities that allow tracking of nutrients at the single cell level. It further targets naturally occurring variations in carbon and oxygen isotopes that avoids need for expensive isotopically labeled mixtures which allows study of samples taken from the field without modification. The method also permits sampling in vivo permitting real-time ambient studies of microbial communities.

Process Studies on Laser Welding of Copper with Brilliant Green and Infrared Lasers

NASA Astrophysics Data System (ADS)

Engler, Sebastian; Ramsayer, Reiner; Poprawe, Reinhart

Copper materials are classified as difficult to weld with state-of-the-art lasers. High thermal conductivity in combination with low absorption at room temperature require high intensities for reaching a deep penetration welding process. The low absorption also causes high sensitivity to variations in surface conditions. Green laser radiation shows a considerable higher absorption at room temperature. This reduces the threshold intensity for deep penetration welding significantly. The influence of the green wavelength on energy coupling during heat conduction welding and deep penetration welding as well as the influence on the weld shape has been investigated.

Numerical Modeling of Fluorescence Emission Energy Dispersion in Luminescent Solar Concentrator

NASA Astrophysics Data System (ADS)

Li, Lanfang; Sheng, Xing; Rogers, John; Nuzzo, Ralph

2013-03-01

We present a numerical modeling method and the corresponding experimental results, to address fluorescence emission dispersion for applications such as luminescent solar concentrator and light emitting diode color correction. Previously established modeling methods utilized a statistic-thermodynamic theory (Kenard-Stepnov etc.) that required a thorough understanding of the free energy landscape of the fluorophores. Some more recent work used an empirical approximation of the measured emission energy dispersion profile without considering anti-Stokes shifting during absorption and emission. In this work we present a technique for modeling fluorescence absorption and emission that utilizes the experimentally measured spectrum and approximates the observable Frank-Condon vibronic states as a continuum and takes into account thermodynamic energy relaxation by allowing thermal fluctuations. This new approximation method relaxes the requirement for knowledge of the fluorophore system and reduces demand on computing resources while still capturing the essence of physical process. We present simulation results of the energy distribution of emitted photons and compare them with experimental results with good agreement in terms of peak red-shift and intensity attenuation in a luminescent solar concentrator. This work is supported by the DOE `Light-Material Interactions in Energy Conversion' Energy Frontier Research Center under grant DE-SC0001293.