Heavy Absorption Research Articles

Performance evaluation of four-wave mixing in a graphene-covered tapered fiber

Four-wave mixing in a monolayer graphene-covered tapered fiber is theoretically analyzed by taking into account the influence of the graphene layer on the light-field distribution. A figure-of-merit (FOM) coefficient, considering both the high nonlinearity and the heavy absorption, is redefined to evaluate nonlinear performance. The fiber diameter and length are optimized to acquire a higher FOM. Using such a graphene-covered tapered fiber with an optimal diameter of 0.736 μm, a maximum conversion efficiency of −38.07 dB is numerically obtained for the 1.55 μm pump when the graphene length is 34.4 μm and the peak pump power is 10 W. Moreover, a 3 dB bandwidth as broad as 430 nm can be realized in the 1.55 μm telecommunication band.

Probing the clumping structure of giant molecular clouds through the spectrum, polarisation and morphology of X-ray reflection nebulae

We suggest a method for probing global properties of clump populations in Giant Molecular Clouds (GMCs) in the case where these act as X-ray reflection nebulae (XRNe), based on the study of the clumping's overall effect on the reflected X-ray signal, in particular on the Fe K-alpha line's shoulder. We consider the particular case of Sgr B2, one of the brightest and most massive XRN in our Galaxy. We parametrise the gas distribution inside the cloud using a simple clumping model, with the slope of the clump mass function (alpha), the minimum clump mass (m_{min}), the fraction of the cloud's mass contained in clumps (f_{DGMF}), and the mass-size relation of individual clumps as free parameters, and investigate how these affect the reflected X-ray spectrum. In the case of very dense clumps, similar to those presently observed in Sgr B2, these occupy a small volume of the cloud and present a small projected area to the incoming X-ray radiation. We find that these contribute negligibly to the scattered X-rays. Clump populations with volume filling factors of > 10^{-3}, do leave observational signatures, that are sensitive to the clump model parameters, in the reflected spectrum and polarisation. Future high-resolution X-ray observations could therefore complement the traditional optical and radio observations of these GMCs, and prove to be a powerful probe in the study of their internal structure. Finally, clumps in GMCs should be visible both as bright spots and regions of heavy absorption in high resolution X-ray observations. We therefore further study the time-evolution of the X-ray morphology, under illumination by a transient source, as a probe of the 3d distribution and column density of individual clumps by future X-ray observatories.

Highly selective and efficient chelating fiber functionalized by bis(2-pyridylmethyl)amino group for heavy metal ions

A classical bis(2-pyridylmethyl)amino group-modified polyacrylonitrile fiber possesses high selectivity and excellent recyclability for heavy metal ion absorption.

Free Space Optic and mmWave Communications: Technologies, Challenges and Applications

SUMMARY Increasing demand in data-traffic has been addressed over the last few years. It is expected that the data-traffic will present the significant part of the total backbone traffic. Accordingly, much more transmission systems will be required to support this growth. A free space optic (FSO) communication is the greatest promising technology supporting high-speed and high-capacity transport networks. It can support multi Gbit/ s for few kilometers transmission distance. The benefits of an FSO system are widespread, low cost, flexibility, immunity to electromagnetic field, fast deployment, security, etc. However, it suffers from some drawbacks, which limit the deployment of FSO links. The main drawback in FSO is the degradation in the signal quality because of atmospheric channel impairments. In addition, it is high sensitive for illumination noise coming from external sources such as sun and lighting systems. It is more benefit that FSO and mmWave are operating as a complementary solution that is known as hybrid FSO/ mmWave links. Whereas the mmWave is susceptible to heavy rain conditions and oxygen absorption, while fog has no particular effect. This paper will help to better understand the FSO and mmWave technologies and applications operating under various atmospheric conditions. Furthermore, in order to improve the system performance and availability, several modulation schemes will be discussed. In

Thin hollow light guide for high-efficiency planar illuminator.

Light guides have been widely used for transforming line sources into planar illuminators for lighting and display applications. Solid light guides provide good uniformity but still have the issues of heavy weight and material absorption, especially for large applications. Hollow light guides solve the problem of weight, but the uniformity is relatively poor or efficiency could be sacrificed for enhancing uniformity. In this paper, a hollow light guide with edge-lit LED sources has been proposed to simultaneously resolve the issues of weight, uniformity, and efficiency. The major approach is to modulate the LED luminous intensity profile by a ring of parabolic surface with continuously varied focal length. The modulated light emitting profile directly makes up sufficient uniformity on the planar surface, and extra components are not required. The prototype is a circular planar illuminator with a diameter of 178 mm and a weight of 240 g. The experiment shows an overall efficiency of 82.37%, with a uniformity of 83.7%. The weight of the whole module is 40% lighter than that of a solid light guide with the same size.

DENSE CLUMPS AND CANDIDATES FOR MOLECULAR OUTFLOWS IN W40

We report the results of the 12CO (J = 3?2) and HCO+ (J = 4?3) observations of the W40 H ii region with the Atacama Submillimeter Telescope Experiment (ASTE) 10 m telescope (HPBW ? 22?) to search for molecular outflows and dense clumps. We found that the velocity field in the region is highly complex, consisting of at least four distinct velocity components at VLSR ? 3, 5, 7, and 10 km s?1. The ?7 km s?1 component represents the systemic velocity of cold gas surrounding the entire region, and causes heavy absorption in the 12CO spectra over the velocity range 6 ? VLSR ? 9 km s?1. The ?5 and ?10 km s?1 components exhibit high 12CO temperature (?40 K) and are found mostly around the H ii region, suggesting that these components are likely to be tracing dense gas interacting with the expanding shell around the H ii region. Based on the 12CO data, we identified 13 regions of high velocity gas, which we interpret as candidate outflow lobes. Using the HCO+ data, we also identified six clumps and estimated their physical parameters. On the basis of the ASTE data and near-infrared images from 2MASS, we present an updated three-dimensional model of this region. In order to investigate molecular outflows in W40, the SiO (J = 1?0, v = 0) emission line and some other emission lines at 40 GHz were also observed with the 45 m telescope at the Nobeyama Radio Observatory, but they were not detected at the present sensitivity.

Anatomy of the AGN in NGC 5548

An extensive multi-satellite campaign on NGC 5548 has revealed this archetypal Seyfert-1 galaxy to be in an exceptional state of persistent heavy absorption. Our observations taken in 2013-2014 with XMM-Newton, Swift, NuSTAR, INTEGRAL, Chandra, HST and two ground-based observatories have together enabled us to establish that this unexpected phenomenon is caused by an outflowing stream of weakly ionised gas (called the obscurer), extending from the vicinity of the accretion disk to the broad-line region. In this work we present the details of our campaign and the data obtained by all the observatories. We determine the spectral energy distribution of NGC 5548 from near-infrared to hard X-rays by establishing the contribution of various emission and absorption processes taking place along our line of sight towards the central engine. We thus uncover the intrinsic emission and produce a broadband continuum model for both obscured (average summer 2013 data) and unobscured ($<$ 2011) epochs of NGC 5548. Our results suggest that the intrinsic NIR/optical/UV continuum is a single Comptonised component with its higher energy tail creating the 'soft X-ray excess'. This component is compatible with emission from a warm, optically-thick corona as part of the inner accretion disk. We then investigate the effects of the continuum on the ionisation balance and thermal stability of photoionised gas for unobscured and obscured epochs.

Effects of Metamaterial Slabs Applied to Wireless Power Transfer at 13.56 MHz

This paper analyzes the effects of a metamaterial slab (or a practical “perfect lens”) with negative permeability applied to a two loop magnetically coupled wireless power transfer (WPT) system at 13.56 MHz, based on theory, full-wave electromagnetic- (EM-) simulations, and measurements. When using lossless slabs with ideal negative permeability in EM-simulations, the WPT efficiencies have been found to be enhanced close to 100% due to the magnetic field focusing. For the case of using a realistic slab made of ring resonators (RR)μr=-1-j0.23withs/d=0.5(s: slab width,d: distance between the transmitting and receiving loops), the WPT efficiency has been found to significantly decrease to about 20%, even lower than that of a free space case (32%) due to the heavy power absorption in the slab. However, some efficiency enhancement can be achieved whens/dis optimized between 0.1 and 0.3. Overall, the significant enhancement of efficiencies when using a lossless slab becomes moderate or only marginal when employing a realistic slab.

Design of renewable poly(amidoamine)/hemicellulose hydrogels for heavy metal adsorption

ABSTRACTRenewable poly(amidoamine)/hemicellulose hydrogels were prepared from O‐acetylated galactoglucomannan (AcGGM)‐rich biomass and shown to display a significantly high adsorption capacity for Cu2+, Cd2+, Pb2+, Zn2+, Ni2+, Co2+, and . Two different acrylamido end‐capped poly(amidoamine) oligomers (PAA) were prepared and covalently immobilized onto an in situ formed polysaccharide network via water‐based free radical graft copolymerization and cross‐linking. The synthetic approach was shown to be viable when using a highly purified AcGGM or a crude spruce hydrolysate, an AcGGM and lignin containing biomass fraction as a reactant. Homogeneous reaction mixtures were obtained in both cases with polysaccharide contents up to 20% by weight. Oscillatory shear measurements indicated a predominantly solid‐like behavior of the hydrogels with an increase in shear storage modulus with increasing cross‐link density. The mechanical integrity of the PAA/hemicellulose hydrogels showed higher water swelling capacity and less fragility than the parent PAA hydrogels and they retained the heavy metal ion absorption ability of the PAA component, even in the presence of the least purified hemicellulose fraction. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41695.

Compton thick active galactic nuclei in Chandra surveys

We present the results from an X-ray spectral analysis of active galactic nuclei (AGN) in the Chandra Deep Field-South, AEGIS-XD and Chandra-COSMOS surveys, focussing on the identification and characterisation of the most heavily obscured, Compton thick (CT, $N_{H}>10^{24} cm^{-2}$) sources. Our sample is comprised of 3184 X-ray selected extragalactic sources, which has a high rate of redshift completeness (97.6 %), and includes improved photometric redshifts over previous studies. We use spectral models designed for heavily obscured AGN which self consistently include all major spectral signatures of heavy absorption. We identify CT sources not selected through our spectral fitting method using X-ray colours, validate our spectral fitting method through simulations, and take considerations for the constraints on $N_{H}$ given the low count nature of many of our sources. After these considerations we identify a total of 100 CT AGN with best-fit $N_{H}>10^{24} cm^{-2}$ and $N_{H}$ constrained to be above $10^{23.5} cm^{-2}$ at 90% confidence. These sources cover an intrinsic $L_{X}$ range of $10^{42}-3x10^{45}$ ergs s$^{-1}$ and a redshift range of z=0.1-4. This sample will enable characterisation of these heavily obscured AGN across cosmic time and to ascertain their cosmological significance. Furthermore, by using the torus models to test different covering factor scenarios, and by investigating the inclusion of the soft scattered emission, we find evidence that the covering factor of the obscuring material decreases with $L_{X}$ for all redshifts, consistent with the receding torus model, and that this factor increases with redshift, consistent with an increase in the obscured fraction towards higher redshifts. We make $N_{H}$, $\Gamma$ (with uncertainties), observed X-ray fluxes and intrinsic $L_{X}$ for all sources analysed in this work publicly available in an online catalogue.

STUDI KANDUNGAN LOGAM BERAT Pb DAN Cd DALAM SEDIMEN DI PERAIRAN PESISIR KECAMATAN GENUK SEMARANG

Heavy metals; lead (Pb) and cadmium (Cd) are commonly used in the industrial sectors, including the industryof batteries, pesticides, detergents, paints, and chemical factories. Heavy metals which get into the water can damage the ecosystems and organisms in it. The aim of this study is to determine the contents of heavy metals Pb and Cd in sediments at Genuk coast waters district, Semarang. This research was conducted on October 7, November12, and December112012 at Genuk Coast Water District, Semarang. The sampling was conducted in 8 stationpoints. The method used for the analysis of heavy metals wasAtomic Absorption Spectrophotometry (AAS), while the sediment fraction was analyzed using wet sieving method in Soil Mechanics Laboratory of the Faculty of Engineering, Diponegoro University. Based on the research result, the contents of heavy metals Pb was higher compared with Cd, i.e heavy metal Pb ranging from 13,99 ppm - 38,11 ppm and heavy metal Cdranging from 0,17 ppm – 0,25 ppm, while the percentage of sediment fraction in all research stations dominated by silt fraction. The resultof correlation test has showed a positive correlation between heavy metals Pb and Cd to the grain size and organic matter in the amount of 11.4% and 49.6%.

Active galactic nucleus torus models and the puzzling infrared spectrum of IRAS F10214+4724

We present a revised model for the infrared emission of the hyperluminous infrared galaxy IRAS F10214+4724 which takes into account recent photometric data from Spitzer and Herschel that sample the peak of its spectral energy distribution. We first present and discuss a grid of smooth active galactic nucleus (AGN) torus models computed with the method of Efstathiou & Rowan-Robinson and demonstrate that the combination of these models and the starburst models of Efstathiou and coworkers, while able to give an excellent fit to the average spectrum of Seyfert 2s and spectra of individual type 2 quasars measured by Spitzer, fails to match the spectral energy distribution of IRAS F10214+4724. This is mainly due to the fact that the νSν distribution of the galaxy falls very steeply with increasing frequency (a characteristic that is usually indicative of heavy absorption by dust) but shows a silicate feature in emission. Such emission features are not expected in sources with optical/near-infrared type 2 AGN spectral signatures. The Herschel data show that there is more power emitted in the rest-frame 20–50 μm wavelength range compared with the model presented by Efstathiou which assumes three components of emission: an edge-on torus, clouds (at a temperature of 610 and 200 K) that are associated with the narrow-line region (NLR) and a highly obscured starburst that dominates in the submillimetre. We present a revised version of that model that assumes an additional component of emission which we associate with NLR clouds at a temperature of 100 K. The 100 K dust component could also be explained by a highly obscured hot starburst. The model suggests that the NLR of IRAS F10214+4724 has an unusually high covering factor (≥17 per cent) or more likely the magnification of the emission from the NLR clouds is significantly higher than that of the emission from the torus.

The nonlinear optical properties of a magneto-exciton in a strained Ga0.2In0.8As/GaAs quantum dot

The magnetic field-dependent heavy hole excitonic states in a strained Ga0.2In0.8As/GaAs quantum dot are investigated by taking into account the anisotropy, non-parabolicity of the conduction band, and the geometrical confinement. The strained quantum dot is considered as a parabolic dot of InAs embedded in a GaAs barrier material. The dependence of the effective excitonic g-factor as a function of dot radius and the magnetic field strength is numerically measured. The interband optical transition energy as a function of geometrical confinement is computed in the presence of a magnetic field. The magnetic field-dependent oscillator strength of interband transition under the geometrical confinement is studied. The exchange enhancements as a function of dot radius are observed for various magnetic field strengths in a strained Ga0.2In0.8As/GaAs quantum dot. Heavy hole excitonic absorption spectra, the changes in refractive index, and the third-order susceptibility of third-order harmonic generation are investigated in the Ga0.2In0.8As/GaAs quantum dot. The result shows that the effect of magnetic field strength is more strongly dependent on the nonlinear optical property in a low-dimensional semiconductor system.

Compton thick AGN in Chandra sureys

AbstractWe present the results from the X-ray spectral analysis of active galactic nuclei (AGN) in the Chandra Deep Field-South, AEGIS-XD and Chandra-COSMOS surveys, focussing on the identification and characterisation of the most heavily obscured, Compton thick (CT, NH &gt; 104 cm−2) sources. Our sample is comprised of 3088 X-ray selected sources, which has a high rate of redshift completeness (97%). The aim is to produce the largest and cleanest uniform sample of these sources from the data as possible. We identify these sources through X-ray spectral fitting, utilising torus spectral models designed for heavily obscured AGN which self consistently include the spectral signatures of heavy absorption, being Compton scattering, photoelectric absorption and iron Kα fluorescence. We identify a total of 163 CT AGN covering an intrinsic 2-10 keV X-ray luminosity range of 102 −3 × 105 erg s−1 and from z = 0.1-7.

Research of Heavy Metal Particle and Ions Absorption Mechanism of Ordinary Portland Cement Materials

As the sign of social development, the vehicles and traffic flux have been increasing and have greatly influenced the ecological environment at the same time, especially on the cementitious based materials along roads as well as constructions. Heavy metal particle and ion absorption behavior and mechanism in cement materials were investigated and analyzed by means of ICP, SEM-EDS and XRD. The absorption mechanism was discussed and generalized.

The Mechanism Researches of Cementitious Materials Adsorb Heavy Metal Particle and Ions

As the sign of social development, the vehicles and traffic flux have been increasing and have greatly influenced the ecological environment at the same time, especially on the cementitious based materials along roads as well as constructions. Heavy metal particle and ion absorption behavior and mechanism in these cement materials were investigated and analyzed by means of ICP, SEM-EDS and XRD. The absorption mechanism was discussed and generalized.

Transmission spectra study of sulfate substituted potassium dihydrogen phosphate

Potassium dihydrogen phosphate (KDP) crystals with different amounts of sulfate concentration were grown and the transmittance spectrum was studied. A crystal with high sulfate replacement density exhibits heavy absorption property in the ultraviolet region which confirms and agrees well with former results.

SHORT-TERM VARIABILITY OF X-RAYS FROM ACCRETING NEUTRON STAR VELA X-1. I.SUZAKUOBSERVATIONS

We have analyzed the time variability of the wide-band X-ray spectrum of Vela X-1, the brightest wind-fed accreting neutron star, on a short timescale of 2 ks by using {\it Suzaku} observations with an exposure of 100 ks. During the observation, the object showed strong variability including several flares and so-called "low states", in which the X-ray luminosity decreases by an order of magnitude. Although the spectral hardness increases with the X-ray luminosity, the majority of the recorded flares do not show any significant changes of circumstellar absorption. However, a sign of heavy absorption was registered immediately before one short flare that showed a significant spectral hardening. In the low states, the flux level is modulated with the pulsar spin period, indicating that even at this state the accretion flow reaches the close proximity of the neutron star. Phenomenologically, the broad-band X-ray spectra, which are integrated over the entire spin phase, are well represented by the "NPEX" function (a combination of negative and positive power laws with an exponential cutoff by a common folding energy) with a cyclotron resonance scattering feature at 50 keV. Fitting of the data allowed us to infer a correlation between the photon index and X-ray luminosity. Finally, the circumstellar absorption shows a gradual increase in the orbital phase interval 0.25--0.3, which can be interpreted as an impact of a bow shock imposed by the motion of the compact object in the supersonic stellar wind.

PEMANFAATAN ABU BAGASSE SEBAGAI FILLER TERHADAP NILAI MARSHALL TEST PADA CAMPURAN ASPHALT TREATED BASE ( ATB )

Solidity construction of road of Indonesia generally are flexible solidity construction. One ofkind flexible solidity are solidity of ATB ( Asphalt Treated Base ) layer that give fundamental layerfunction that under surface layer which support and spread load along with place to put surfacelayer. Trial to asphalt are follow : penetration, flexible point, ductility, while trial of agregate follow: kind heavy ang agregate absorption, analysis of agregate filler. The thing of test trial of optimumasphalt degree is devided 5 variation namely 5%, 5.5%, 6%, 6.5% and 7% wich each groups aremade 5 different sample with weight each 1200 gram. The optimum asphalt degree which be got6.5%. The thing of test trial of optimum asphalt by filler Bagasse Dust are made 11 groups by fillerdegree 6.42% early which be made 0% up to 90% of Bagasse dust according to weight with 10%interval, by each groups are made 3 samples. The study result showed that three are influence ofusing Bagasse dust as filler to Marshall Test value. Stability is shown by equation Y = 1672.5 +17.544 X – 0.2336 X2 gotten optimum Bagasse dust degree about 37.59% by stability value are2001.033 kg. The flow value is shown by equation Y = 4.05 + ( 2.7 E – 3 ) X – ( 1 E – 4 ) X2 byoptimum Bagasse dust degree about 13.5% is gotten flow value 4.05%. The hole in ATB compoundis shown by equation Y = 4.102 + ( 0.04 ) X – ( 5 E – 4 ) X2 is gotten optimum Bagasse dust about40% by air hole about 4.90%. To Marshall Quotient value may be shown by equation Y = 4.007 +( 0.046 ) X – ( 5 E – 4 ) X2 by optimum Bagasse dust degree about 46% by Marshall Quotient valueare 5.06 kN/mm.Key word : Asphalt Treated Base ( ATB ), Bagasse Dust.

Selected Heavy Metals in Water and Sediments and Their Bioconcentrations in Plant (&amp;lt;i&amp;gt; Polygonum pulchrum&amp;lt;/i&amp;gt;) in Sosiani River, Uasin Gishu County, Kenya

Heavy metals’ availability and accumulation along the food chain pose public health risks. Water, sediment and plant samples were collected from selected sampling sites along Sosiani River, Uasin Gishu County, Kenya. The sediment and plant samples were dried in the oven at 50°C to constant weight and digested in a mixture of acids according to standard procedures. The water samples, sediments and plants digests were analyzed for selected heavy metals using Atomic Absorption Spectrophotometer (model AAS Variant 200). The site near the Moi Teaching and Referral Hospital (MTRH) had the highest total heavy metals concentration in water: Cu (0.18 ± 0.04 ppm); Pb (0.46 ± 0.09 ppm) and Zn (0.70 ± 0.22 ppm) and sediments: Cu (1.62 ± 0.14 ppm); Pb (1.27 ± 0.17 ppm) and Zn (6.73 ± 0.88 ppm) respectively. Fractionation of heavy metals in sediments showed low percentage solubility (Cu 9.3%; Pb 8.5%; Zn 4.2%). Concentration of zinc in studied plants was highest (3.60 ± 0.63 ppm), with a bioconcentration factor of 15.1 based on soluble zinc fraction. This indicates that conditions in the study area show preferential zinc metal uptake in plants and may lead to accumulation in exposed plants posing Zn exposure risks along the food chain. Suggestions are made for monitoring of heavy metals in food crops and aquatic organisms such as fish in the study area.