Single Absorber Research Articles

Dust and gas absorption in the high mass X-ray binary IGR J16318−4848

Context. With an absorption column density on the order of 1024 cm−2, IGR J16318−4848 is one of the most extreme cases of a highly obscured high mass X-ray binary. In addition to the overall continuum absorption, the source spectrum exhibits a strong iron and nickel fluorescence line complex at 6.4 keV. Previous empirical modeling of these features and comparison with radiative transfer simulations raised questions about the structure and covering fraction of the absorber and the profile of the fluorescence lines. Aims. We aim at a self-consistent description of the continuum absorption, the absorption edges, and the fluorescence lines to constrain the properties of the absorbing material, such as ionization structure and geometry. We further investigate the effects of dust absorption on the observed spectra and the possibility of fluorescence emission from dust grains. Methods. We used XMM-Newton and NuSTAR spectra to first empirically constrain the incident continuum and fluorescence lines. Next we used XSTAR to construct a customized photoionization model where we vary the ionization parameter, column density, and covering fraction. In the third step we modeled the absorption and fluorescence in a dusty olivine absorber and employed both a simple analytical model for the fluorescence line emission and a Monte Carlo simulation of radiative transfer that generates line fluxes, which are very close to the observational data. Results. Our empirical spectral modeling is in agreement with previous works. Our second model, the single gas absorber does not describe the observational data. In particular, irrespective of the ionization state or column density of the absorber, a much higher covering fraction than previously estimated is needed to produce the strong fluorescence lines and the large continuum absorption. A dusty, spherical absorber (modeled as consisting of olivine dust, although the nature of dust cannot be constrained) is able to produce the observed continuum absorption and edges. Conclusions. A dense, dusty absorber in the direct vicinity of the source consisting of dust offers a consistent description of both the strong continuum absorption and the strong emission features in the X-ray spectrum of IGR J16318−4848. In particular, for low optical depth of individual grains, which is the case for typical volume densities and grain size distribution models, the dust will contribute significantly to the fluorescence emission.

Study on power generation of single Point Absorber Wave Energy Converters (PA-WECs) and arrays of PA-WECs

The effects of humanity's carbon footprint deserve attention and remediation. The ocean can provide an abundant source of renewable energy instead of fossil fuels in the form of wave energy. However, wave energy collection needs to be comparable in terms of cost and efficiency to be considered a viable alternative. Point Absorber Wave Energy Converter (PA-WEC) is one method of capitalizing on the ocean's wave energy. Past research provides methods for optimizing control force parameters for single PA-WECs. This paper provides methods for optimizing control force parameters for arrays of PA-WECs; optimization considers factors such as radiation hydrodynamic interactions, diffraction hydrodynamic interactions, array arrangements, and wave incident angles. In section 2, we outline the steps to determining optimal control forces. In section 3, we present numerical simulations of PA-WECs and compared the results between single PA-WEC systems and arrayed PA-WEC systems.

Dust and gas absorption in the high mass X-ray binary IGR J16318−4848

Context. With an absorption column density on the order of 10²⁴ cm⁻², IGR J16318−4848 is one of the most extreme cases of a highly obscured high mass X-ray binary. In addition to the overall continuum absorption, the source spectrum exhibits a strong iron and nickel fluorescence line complex at 6.4 keV. Previous empirical modeling of these features and comparison with radiative transfer simulations raised questions about the structure and covering fraction of the absorber and the profile of the fluorescence lines. Aims. We aim at a self-consistent description of the continuum absorption, the absorption edges, and the fluorescence lines to constrain the properties of the absorbing material, such as ionization structure and geometry. We further investigate the effects of dust absorption on the observed spectra and the possibility of fluorescence emission from dust grains. Methods. We used XMM-Newton and NuSTAR spectra to first empirically constrain the incident continuum and fluorescence lines. Next we used XSTAR to construct a customized photoionization model where we vary the ionization parameter, column density, and covering fraction. In the third step we modeled the absorption and fluorescence in a dusty olivine absorber and employed both a simple analytical model for the fluorescence line emission and a Monte Carlo simulation of radiative transfer that generates line fluxes, which are very close to the observational data. Results. Our empirical spectral modeling is in agreement with previous works. Our second model, the single gas absorber does not describe the observational data. In particular, irrespective of the ionization state or column density of the absorber, a much higher covering fraction than previously estimated is needed to produce the strong fluorescence lines and the large continuum absorption. A dusty, spherical absorber (modeled as consisting of olivine dust, although the nature of dust cannot be constrained) is able to produce the observed continuum absorption and edges. Conclusions. A dense, dusty absorber in the direct vicinity of the source consisting of dust offers a consistent description of both the strong continuum absorption and the strong emission features in the X-ray spectrum of IGR J16318−4848. In particular, for low optical depth of individual grains, which is the case for typical volume densities and grain size distribution models, the dust will contribute significantly to the fluorescence emission.

Adsorption of Chromium (III) on Melamine: Kinetic, Isotherm, Thermodynamics and Mechanism Analysis

Melamine as single absorbance had been investigated in heavy metal ions removing and it showed good adsorption performance. This paper focused on the chromium (III) remove from wastewater by adsorption with melamine. The results showed that the melamine had a great adsorption surface area of 8.71 m2/g and high adsorption capacity (2843 mg/g) at removal efficiency of chromium (III) (98.63%) within 60 min at n (melamine)/n (chromium)=1.5 and reaction temperature at 90 °C. The adsorption process was described by Langmuir isotherm and the kinetic process was fitted well with pseudo-second-order model. The adsorption process was a spontaneous, endothermic and physisorption process according to the thermodynamic analyzing results. This study provided a good evidence for successful application of melamine in adsorptive removal of chromium (III) from wastewater.

Techno-economic evaluation of amine-reclamation technologies and combined CO2/SO2 capture for Australian coal-fired plants

CSIRO’s patented CS-Cap process aims at reducing the costs of amine-based post-combustion capture by combining SO2 and CO2 capture using one absorbent in a single absorber column. By avoiding the need for a separate flue gas desulfurization unit, the process offers potential savings for power plants requiring CO2 capture. High-level cost estimates based on lab and pilot data are presented for two amine reclamation techniques i.e. thermal reclamation and reactive crystallisation. Only regeneration via reactive crystallisation reduces CS-Cap costs below base case FGD/SCR-PCC. Cost estimations suggest a potential reduction of 38–44% in the total plant cost when using the CS-Cap process compared to base case. However, the amine reclaimer operating cost governs the overall cost of the CS-Cap process and is highly sensitive to sulfur content. A 50% reduction is observed when SO2 levels reduce from 700 to 200 ppm. Comparing levelised cost of electricity and CO2 avoided costs for CS-Cap against our base case, low sulfur brown coal has a slight (5–7%) cost advantage; however, confirmation requires pilot data on amine recovery.

Stabilization of Black Perovskite Phase in FAPbI3 and CsPbI3

While halide perovskite allows a great versatility, the application on single absorber solar cells restrings significantly the number of available materials. In this context, CsPbI3 and FAPbI3 (FA,...

(Invited) Halide Vapor Phase Epitaxy of III-V Alloys for Unassisted Water Photoelectrolysis

Photoelectrochemical water splitting devices comprising III-V semiconductors alloys hold record solar-to-hydrogen efficiencies, achievable only by complex architectures involving tandem cells i.e an inverted metamorphic GaInAsP/GaInAs solar cell with an efficiency of 32.6% under 1-sun and the GaInAs/p-GaInP PV/PEC with a solar to hydrogen conversion efficicncy close to 17% under 1-sun as well; nanostructures and buried junctions, which leads to high manufacturing complexity. These approaches have been necessary to circumvent the shortcomings towards unassisted water splitting of state-of-the art III-V alloy-based single absorber devices, particularly of InGaP2, InGaAs, GaPN, and GaAsN, such as a) inadequate band edge alignment with respect to the HER and OER redox potentials, b) insufficient photovoltage to favor charge separation at the solid electrolyte liquid junction, and/or iii) charge recombination. An alternative path to overcome these limitations while maintaining device simplicity and competitive solar fuels costs is to develop novel III-V photoabsorbers with adequate band energetics.First-principles DFT+U calculations incorporating the local density approximation and generalized gradient approximation have shown that incorporation of Sb into GaN or GaP forms GaSbxN1-x and GaSbyP1-y alloys with narrowed band gap in the former case and changes the electronic band structure from indirect to direct in the latter. Theoretical computations predict that with band gaps in the order of 2 eV, these materials could be able to straddle the electrochemical potentials for water oxidation and proton reduction in acidic electrolytes.Metal organic chemical vapor deposition (MOCVD) and hydride vapor phase epitaxy (HVPE) have been used to synthesize GaSbxN1-x and GaSbyP1-y alloys, respectively, achieving single crystalline quality in a wide range of homogeneous Sb incorporation. Experimental measurements confirm the significant band gap reduction from 3.4 eV in pure GaN to 1.5 eV in GaSbxN1-x as determined by Tauc plot analysis of diffuse reflectance data and low temperature photoluminescence spectroscopy; and suggest reduction of the direct transition of GaP at 2.68 eV in the case of GaSbyP1-y alloys.The photoelectrochemical performance towards water splitting of GaSbxN1-x and GaSbyP1-y alloys has been assessed in 2- and 3-electrode standard methods to determine their characteristic attributes, e.g. flat-band and onset potentials, photovoltage, zero-bias photocurrent density, fill factors, carrier concentrations, and most importantly, their ability for gas evolution by in situ fluorescence probing. Furthermore, photoelectrochemical impedance measurements have shown the absence of charge transfer resistance at the interface between electrode and electrolyte in the case of GaSbyP1-y alloys that is clearly observed in pure GaP, suggesting antimony can also modify the charge transport properties of the material.These promising results have also motivated our efforts for better understanding of the synthesis processes, particularly for the HVPE technique given its fast growth rate is both an advantage and a challenge for precise thickness and composition control. A computational model using Chemkin Prowas used to validate the previous experimental results for the growth of Gallium Antimonide Phosphide (GaSbyP1-y) films. The model was developed for a reactor having one heating zone for precursor formation and a second zone for film deposition. The first zone was assumed to be in thermodynamic equilibrium. The second (deposition) zone was modeled using a chemistry set describing various gas phase and gas-solid kinetics. The substrate temperature and system pressure were successfully correlated with the observed experimental values for the growth rate and other important features such as the crystalline quality and degree of Sb incorporation. The results also point out the major gas phase chemical species involved in the growth, such as GaCl, SbCl, P2 and P4, which opens the door for future optimization of the synthesis process oriented towards a better precursor utilization and higher antimony incorporation at elevated substrate temperatures, which are required for single crystalline material quality. Acknowledgements: Financial support from Conn Center for Renewable Energy Research and NSF EPSCoR Program (1355438)

Mechanistic Studies for Electrochemical Self-Assembly of CuSCN/Stilbazolium Dye Hybrid Thin Films

We have found electrochemical self-assembly (ESA) of inorganic / organic hybrid thin films in which the inorganic is CuSCN, known as a wide bandgap p-type semiconductor, whereas the organic is 4-N,N-dimethylamino-4’-N’-methylstilbazolium chromophore (abbreviated as DAS) as its salt with tosylate (DAST) known to exhibit second-order nonlinear optical property for terahertz emitters. DAS is also known to yield a layered inorganic-organic hybrid crystal in a (DAS)(Cu5I6) composition [1]. Strong dipole-dipole interaction of the DAS chromophores aligned between the CuI layers results in a spontaneous photocarrier generation and ambipolar transport in a single absorber solar cell. Thus, CuSCN/DAS hybrid thin films can be attractive alternatives for such opto-electrical applications, when ordered arrangement of DAS chromophore is achieved during ESA.In our previous study, switching of dye loading mechanism has been suggested, depending on DAS concentration (C DAS) in the bath [2]. In low C DAS, the loading is limited by diffusion so that DAS is entrapped within CuSCN crystal grains, while surface reaction of hybridization begins to limit the dye loading in high C DAS, resulting in formation of unique nanostructures as well as phase separation of inorganic and organic domains.In this study, electrochemical analysis by employing rotating disk electrode (RDE) has been performed to verify the mechanism of ESA and also to explore the limit of DAS loading. Electrodeposition of CuSCN undergoes as limited by transport of 1 : 1 complex between Cu2+ and SCN- ions, namely [Cu(SCN)]+ species, near 100% Faradic efficiency with marginal influence by the presence of DAS. Thus, the rate of CuSCN precipitation, P CuSCN, is always proportional to the concentration of the complex (C comp), and also to ω 1/2 (ω = angular speed of rotation of RDE) therefore P CuSCN can be expressed Eq. (1) from Levich equation. P CuSCN = J/F = 0.62×C comp×D comp 2/3×ν -1/6×ω 1/2 ··· (1)On the other hand, the rate of DAS precipitation, P DAS, should also be proportional to ω 1/2 under the regime of diffusion limited loading with a given C DAS, and is independent of CuSCN formation rate. P DAS = 0.62×C DAS×D DAS 2/3×ν -1/6×ω 1/2 ··· (2)Plots of P DAS against C comp for variation of C DAS were examined, and indeed such a trend as predicted from the above-mentioned model was found (Fig. 1). In the high C comp range, P DAS is independent of C comp and appears proportional to C DAS, because of the diffusion limited loading mechanism. When C comp goes below certain concentration, P DAS changes proportionally to C comp, while its slope also increase as dependent on C DAS. The relationship between the switching C comp and C DAS yields C DAS / C comp = 1/31 as the border for the switching of the mechanism [3], whereas the dependence of the slope on C DAS in the low C comp range should reveal the stoichiometry of surface complex between CuSCN and DAS. When the rate surface complex formation, P DAS become proportional to the P CuSCN, assuming n of DAS complexes with single CuSCN site yields the equilibrium as the right and the surface is expected to be always equilibrated such equation, P CuSCN + nC DAS ⇄ P DAS ··· (3)Stability constant K should be expressed like Eq. (4), K = P DAS/P CuSCN × C DAS n ··· (4)Eq. (4) can be re-written by inserting Eq. (1), P DAS/C comp= 0.62×D comp 2/3×ν -1/6×ω 1/2 ×K×CDAS n ··· (5)Plotted slope of Fig. 1 in the low C comp range (P DAS/C comp) against C DAS and did fitting with n as variable and then resulted n = 0.6. It means approximately one DAS coordinating two CuSCNs and stability constant K can be calculated as 6.78×102 mol−0.5 cm2.5.[1] Elena Cariati et al., Adv. Mater., 13, 1665-1668 (2001).[2] Yuki Tsuda et al., Monatshefte für Chemie, 148, 845-854 (2017).[3] Yuki Tsuda et al., J. Electrochem. Soc. 166(9) B3096-B3102 (2019). Figure 1

Isolation, Purification and Characterization of Novel Phytomitogen from Nigella sativa Seeds

The objective of the present study was to extract and purified proliferative factor for peripheral blood lymphocytes from Nigella sativa seeds. Dimeric 44, 32 and 26 -kDa glucosamine-specific lectins were extracted and purified from seeds of N. sativa L. by using different ionic strength solvents (deionized distilled water, phosphate buffer slain and 0.1 M HCl) purification procedure included, precipitation in saturated ammonium sulphate, then Sephadex G-100 gel filtration was used for further purification, finally electrophoresis by polyacrylamide gel to estimate the molecular weight in the presence of sodium dodecylsulphate. Single absorbance peak at 280 nm was recorded in each extracted method. The temperature and pH value on mitogenic activity was studied in temperature ranged from 4°C-60°C, the mitogenic activity reduced with gradual increase of temperatures, 50% of activity lost at temperature greater than 40°C, while the optimum pH for mitogenic activity ranged from 5-9, at pH value less than 3, and greater than 12 the activity disappeared. Interestingly, lectin extracted from N. sativa seeds have high activity especially that extracted with 0.1 M HCl and showed stability at temperature from 4°C to 10°C and pH from 5 to 9. The pure lectin is a homodimeric molecule of 26 kDa with subunit molecular mass of 12.9 kDa. The novel lectin exceed the PHA-Sigma in mitogenic activity.

Optically tunable single narrow band all-dielectric terahertz metamaterials absorber

In this work, we numerically demonstrated a single narrow band THz absorber based on cylindrically shaped periodical p-type doped silicon with excellent attributes, including polarization insensitivity and optical tunability. Good absorption characteristics were demonstrated at 0.57 THz with an absorption of nearly 99.75% and a quality factor of 11.278. Furthermore, its absorbance could be flexibly tuned from above 99% to less than 35% by changing the pump beam fluence from 0 µJ/cm2 to 3000 µJ/cm2. The demonstrated tunability may find potential applications in dynamic functional THz devices.

Effect of temperature on water vapor sorption on commercial desiccant and rice husk-CaCl2 composite desiccant

Many efforts have been made to control the moisture in the package by the addition of the active ingredients which absorb this moisture. In the modern retail, moisture or water vapor absorber, known as desiccant has been widely used to extend the shelf life of the food product. Composite desiccants comprising the high active ingredient has been developed to improve the performance of single absorber material in absorbing and controlling moisture in the food package. The purpose of this research was to observe the effect of temperature storage in moisture sorption of commercial desiccants (silica gel and active clay) comparing to the composite desiccant of rice husk-CaCl2. This research proved that the sorption ability of these desiccants were different, and it was influenced by the temperature of the storage. The results showed that rice husk-CaCl2 composite dessicant possessed the highest absorption capacity especially at temperature of 40 °C with value of 1.2342 g H2O/g desiccant for 7 days of storage. The increase of temperature has been resulted on increasing absorption rate (k), for example, rice husk-CaCl2 composite dessicant, the k value was 0.2587 g H2O/g desiccant/day at 30 °C, 0.7828 g H2O/g desiccant/day at 40 °C and 0.9562 g H2O/g desiccant/day at 50 °C. It looks that the moisture absorption followed pseudo second order for all treatment with R2 at 99% for almost all treatments.

Assembly and Characterization of Biocompatible Coenzyme Q10 -Enriched Lipid Nanoparticles.

Coenzyme Q10 (CoQ10 ) is a strongly hydrophobic lipid that functions in the electron transport chain and as an antioxidant. CoQ10 was conferred with aqueous solubility by incorporation into nanoparticles containing phosphatidylcholine (PtdCho) and apolipoprotein (apo) A-I. These particles, termed CoQ10 nanodisks (ND), contain 1.0 mg CoQ10 /5 mg PtdCho/2 mg apoA-I (97% CoQ10 solubilization efficiency). UV/Vis absorbance spectroscopy of CoQ10 ND revealed a characteristic absorbance peak centered at 275 nm. Incorporation of CoQ10 into ND resulted in quenching of apoA-I tryptophan fluorescence emission. Gel filtration chromatography of CoQ10 ND gave rise to a single major absorbance peak and HPLC of material extracted from this peak confirmed the presence of CoQ10 . Incubation of cultured cells with CoQ10 ND, but not empty ND, resulted in a significant increase in the CoQ10 content of mitochondria as well as enhanced oxidative phosphorylation, as observed by a ~24% increase in maximal oxygen consumption rate. Collectively, a facile method to solubilize significant quantities of CoQ10 in lipid nanoparticles has been developed. The availability of CoQ10 ND provides a novel means to investigate biochemical aspects of CoQ10 uptake by cells and/or administer it to subjects deficient in this key lipid as a result of inborn errors of metabolism, statin therapy, or otherwise.

Numerical Analysis of Single Negative Broadband Metamaterial Absorber Based on Tri Thin Layer Material in Visible Spectrum for Solar Cell Energy Harvesting

A broadband nanostructure metamaterial absorber (MA) based on tri-layer metallic-optical-thin film molded shape is proposed for visible spectrum solar energy scavenging. This MA is investigated for photon mobility to achieve significant photon conversion and absorption to integrate into solar cell technology, IoT components, or energy harvesting. Design and analysis of the proposed MA were performed using the “Yee’s Finite-Difference Time-Domain (FDTD)” method based on commercially available CST microwave studio simulation software. Numerical computational tools depict an absorptivity of higher than 80%, which covered nearly the visible region 430~627 THz. This significant absorptivity can be maintained with both transverse electric and transverse magnetic polarizations. Furthermore, molded shape with two-dimensional split and nano-square window expedites the unit cell to exhibit single negative (SNG) metamaterial characteristics and photon conversion acceleration. Compared with related previously reported broadband absorbers, the proposed MA has promising application, in conventional solar cell efficiency improvement and emitter.

Design and fabrication of a single metal layer tunable metamaterial absorber in THz range

The design and development of resonance-tunable and high-absorptivity metamaterial absorbers is a research hotspot. In this paper, a single-band tunable metamaterial absorber based on the strontium titanate (STO) layer is designed and measured. This absorption peak is enhanced from 90% (D=3.2μm) to 99.4% (D=4.2μm) and the resonant frequency point is shifted from 6.2 THz to 5.8 THz, while it is enhanced and shifted to lower frequencies with the structural parameter P reducing. Measured results show that this absorption peak shows only a 2% reduction when the measured temperature is increased from 300 K to 380 K. Synchronous, the resonant frequency point is shifted from 6.2 THz to 7.1 THz. Based on the temperature-dependence of the STO layer, a temperature tunable metamaterial absorber is experimentally verified.

Microwave absorption properties of single and double-layer absorbers based on BaFe12O19 and SiO2

In order to study a new microwave absorption properties of single and double layer barium hexaferrite and silica have been investigated in X-band (8.2–12.4 GHz) frequencies. Barium hexaferrite BaFe12O19 was synthesized by ceramic method and Silica SiO2 was prepared from beach sand. Barium hexaferrite and silica SiO2 with a total thickness of 3 mm, 4 mm, 5 mm, 6 mm and 7 mm, were characterized at room temperature using vector network analyser (VNA) Keysight PNA-L N5232A. Reflection loss (RL) of single and double-layer absorbers of barium hexaferrite and silica were calculated and simulated using the transmit line theory. The minimum RL value (less than − 10 dB) of single layer barium hexaferrite is −21 dB at 9 GHz. The minimum RL values (less than − 10 dB) of single layer silica SiO2 is −40 dB at 9.2 GHz with 4 mm of thickness. The results show that double layer absorbing material showed different RL values than single layer of barium hexaferrite BaFe12O19 and silica SiO2.

Fluazinam Potential as a Fungicide in Liquid Culture System for the Growth of Haematococcus pluvialis Microalgae

All across biological system, fungal infection in freshwater systems is well known to obstruct the aquatic biomass population such as microalgae. However, there is a lack of extensive information on the suitable technique to control them. This research aims to assess the effects of the fungicide fluazinam as a single dose treatment on the Haematococcus pluvialis growth rate and the presence of chytrids fungus in a liquid culture system. The variables used in this experiment were the concentration of fluazinam given to the culture (i.e. 0.25; 0.5; 0.75; 1; 1.25 ppm) as a single dose treatment. The growth performance of H. pluvialis was observed in 6 days consecutively based on the cell density by a single direct absorbance measurement and the cell counting by haemocytometer. The best growth was achieved in a culture system which was given fluazinam at a concentration of 0.5 ppm (started from 1.0 x 105 cells/mL to 5.5 x 105 cells mL−1 on the 5th day) and no chytrids fungus are found in the culture system either. So, in conclusion, the use of fluazinam is a promising treatment for removing contaminants that inhibit H. pluvialis growth.

Optimization of micro-perforated sound absorber using Particle Swarm Optimization (PSO)

This study investigates the acoustic properties of micro-perforated panel (MPP) as an alternative to passive noise control. In order to obtain high sound absorption over broad frequency band, the analysis of sound absorption performance of MPP sound absorber should be conducted based on 3 major design parameters, such as perforation diameter, d, air cavity depth, D, and distance between perforations, b, of MPP. Next, the optimization of sound absorption coefficient for MPP sound absorber need to be done by using the Particle Swarm Optimization (PSO) algorithm and the optimum parameters of a single layer MPP sound absorber should be obtained for achieving higher sound absorption which the sound absorption coefficient, α + 0.5 with a wider frequency band. The PSO is used in order to optimize the panel construction to provide maximum sound absorption coefficient in a determined wide band frequency range. Experiments are carried out at normal sound incidence and plane waves. A good agreement is achieved between the theory and the experiments.

Collision modeling of single unit impact absorber for mechanical systems vibration attenuation

Collision modeling of single unit impact absorber for mechanical systems vibration attenuation

New strategies for colloidal-quantum-dot-based intermediate-band solar cells.

The intermediate-band solar cell (IBSC) concept promises to increase the efficiency limit in a single-junction solar cell through the absorption of below-bandgap-energy photons. Despite their operating principle having been proposed over 20 years ago, IBSCs have not delivered on this promise yet, and the devices fabricated so far, mainly based on embedded epitaxial quantum dots, have instead operated with lower efficiency than conventional solar cells. A new paradigm, based on the exploitation as the intermediate band of the intragap states naturally occurring in the density functional theory description of colloidal (i.e., chemically synthesized) quantum dots, was suggested recently. Here, we revisit this intriguing concept unveiling its shortcomings and propose two alternative schemes: in the first, the localized electron surface trap states, ubiquitously found in commonly synthesized colloidal quantum dots, are used as intermediate bands in strongly coupled films made of small InAs nanocrystals and, in the second scheme, the intermediate band is provided by the conduction-band-minimum-derived miniband in films of larger InAs nanocrystals. Both schemes yield estimated limiting IBSC efficiencies exceeding Shockley-Queisser's limit for a single absorber.

Perforated Dallenbach microwave absorber based on dielectric polyaniline – phenolic resin composite for X-band applications

Design optimization to achieve broadband microwave absorption of a metal backed single layer microwave absorber in Dallenbach form is investigated by perforated designing of polyaniline (PA) reinforced novolac phenolic resin (NPR) composites in the frequency ranges of 8.2-12.4 GHz. The effect of triangular lattice pattern circularly perforated design is studied through effective complex permittivity and impedance matching condition between air-absorber interfaces. A comparative analysis of broadband absorption efficiency of perforated and non-perforated PA/NPR composite is carried out in terms of impedance matching to support the tailoring of microwave properties. The study shows a -15dB whole X band absorption bandwidth for PA3 perforated sample of thickness 3mm with a maximum absorption peak of ∼-35dB at 12.4 GHz.