Absorption Probability Research Articles

Stealthy Hyperuniform Surface Structures for Efficiency Enhancement of Organic Solar Cells

Low absorption in the thin active layer of conventional organic solar cells limits their power conversion efficiency. Structured surface layers are a common approach to diffracting incoming light, thus elongating its path through the active layer, thereby increasing the probability of absorption and hence the power conversion efficiency. While standard periodic structures diffract light into discrete angles, making them optimal only for specific wavelengths, random structures induce broadband, but nontailorable diffraction. Thus, instead, a stealthy hyperuniform structure, designed to exhibit beneficial diffraction properties is implemented: it directs the light into a predefined range of higher angles, prevents diffraction into small angles, and is thus ideal for a strong active path length enhancement. After numerical optimization of the feature height and diameter, the stealthy hyperuniform structure is fabricated in silicon by electron beam lithography and subsequently transferred into a transparent polymer via replica molding. Experimental diffraction images reveal a circular symmetric spectrum, inducing diffraction independent of the azimuthal angle and polarization of the incident light. The application of the stealthy hyperuniform structure on a poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′]dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione)]:3,9‐bis(2‐methylene‐(3‐(1,1‐dicyanomethylene)‐indanone))‐5,5,11,11‐tetrakis(4‐hexylphenyl)‐dithieno[2,3‐d:2′,3′‐d’]‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene organic solar cell leads to a sharp increase in current density and power conversion efficiency.

Tailoring Fano Lineshape in Photonic Local Density of States by Losses Engineering

AbstractNon‐Hermitian theory in photonics revolutionized the understanding of optical resonators, thanks to the concept of quasi‐normal modes (QNM) and to a deep revision of the Purcell factor expression. Counterintuitive effects followed, such as complex modal volumes and non‐Lorentzian local density of states (LDOS) of QNMs. One of the fascinating aspects of non‐Hermitian theory is the analogy with quantum mechanics for autoionizing electronic levels where the absorption cross'section is characterized by Fano lineshapes, caused by interference between the probability of absorption in the continuum and in the bound states. In photonics Fano lineshapes can arise from QNM normalization through the complex modal volume. The link between Fano lineshapes in photonic LDOS of QNMs and in the case of autoionizing states needs to be clarified. Here, by developing an analytical model based on the role of losses in the QNM normalization, they clarify the meaning of the phase of QNM normalized fields (qFano parameter),linking QNMs normalization to the concept of interference among the resonant and the leaky modes. This inspired the design of photonic crystal (PhC) cavity that exhibits LDOS with Fano character inside the itself, providing a proof of principle on how to mold the radiative lifetime by Purcell effect.

Time to Absorption in Markov Chains as a Mixture Distribution of Hypo-Exponential Distributions

Abstract We given an elementary proof that in a Markov chain with absorbing states, and positive probability of absorption at some time t > 0 {t>0} , time to absorption follows a mixture distribution of hypo-exponential random variables. We use this fact to show that early approximations of such a distribution yield the length of the shortest path from an initial state to an absorbing state. Thus different Markov chains with the same distance of shortest paths can yield identical first order approximations. Our work is motivated by the classical Armitage and Doll model of carcinogenesis.

Measurement of the intrinsic hadronic contamination in the NA64[formula omitted] high-purity [formula omitted] beam at CERN

We present the measurement of the intrinsic hadronic contamination at the CERN SPS H4 beamline configured to transport electrons and positrons at 100 GeV/c. The analysis, performed using data collected by the NA64-e experiment in 2022, is based on calorimetric measurements, exploiting the different interaction mechanisms of electrons and hadrons in the NA64 detector. We determined the contamination by comparing the results obtained using the nominal electron/positron beamline configuration with those from a dedicated setup, in which only hadrons impinged on the detector. We also obtained an estimate of the relative protons, anti-protons and pions yield by exploiting the different absorption probabilities of these particles in matter. We cross-checked our results with a dedicated Monte Carlo simulation for the hadron production at the primary T2 target, finding a good agreement with the experimental measurements.

Encounter-based reaction-subdiffusion model II: partially absorbing traps and the occupation time propagator

In this paper we develop an encounter-based model of reaction-subdiffusion in a domain Ω with a partially absorbing interior trap . We assume that the particle can freely enter and exit , but is only absorbed within . We take the probability of absorption to depend on the amount of time a particle spends within the trap, which is specified by a Brownian functional known as the occupation time A(t). The first passage time (FPT) for absorption is identified with the point at which the occupation time crosses a random threshold with probability density . Non-Markovian models of absorption can then be incorporated by taking to be non-exponential. The marginal probability density for particle position prior to absorption depends on ψ and the joint probability density for the pair , also known as the occupation time propagator. In the case of normal diffusion one can use a Feynman–Kac formula to derive an evolution equation for the propagator. However, care must be taken when combining fractional diffusion with chemical reactions in the same medium. Therefore, we derive the occupation time propagator equation from first principles by taking the continuum limit of a heavy-tailed continuous-time random walk. We then use the solution of the propagator equation to investigate conditions under which the mean FPT for absorption within a trap is finite. We show that this depends on the choice of threshold density and the subdiffusivity. Hence, as previously found for evanescent reaction-subdiffusion models, the processes of subdiffusion and absorption are intermingled.

Theoretical and experimental study of the 6S-8S two-photon absorption cross-section in cesium atoms.

The probability of a two-photon absorption (TPA) process is quantified by means of the TPA cross-section. In this work the TPA cross-section for the 6S1/2 → 8S1/2 transition in cesium (Cs) atoms is obtained from a theoretical and experimental approach. It is calculated using second order perturbation theory including hyperfine structure and Doppler broadening for a thermal atomic vapor. The theoretical values for the TPA cross-sections of the two allowed hyperfine transitions are σ~3,3=3.10×10-24 cm4/W and σ~4,4=3.65×10-24 cm4/W. An experiment is set up to measure these cross-sections based on the quadratic dependence between the TPA transition rate and the intensity of the laser light. Values of σ~3,3=(3.6±1.1)×10-24 cm4/W and σ~4,4=(4.6±1.1)×10-24 cm4/W are obtained from the measurements. The results show an agreement between theory and experiment. To the best of our knowledge, this is the first time that these cross-sections are reported.

Background energy spectra of lutetium-based inorganic scintillators for radiation detection

In this work the predictions of the background spectra of ten scintillating crystals with lutetium for 1 cm3 cubes are presented. These spectra were obtained by performing Monte Carlo simulations of the 176Lu decay, and the radiation interaction mechanisms in the crystal materials, using PENELOPE and GATE, and by using an analytic model based on the 176Lu decay radiation emission and absorption probabilities. To properly simulate these materials, the mass density and elemental composition were investigated from various references, from which other important properties were derived, such as the expected count rate due to their intrinsic radiation and the intrinsic quantum efficiency for a continuous range of crystal thickness and photon energies, presented as two-dimensional maps. Additionally, other physical properties important for radiation detection of the lutetium-based scintillators are also compared to those of lutetium oxyorthosilicate, the most prevailing material in current detector technology for various imaging applications.

X-ray absorption fine structure (XAFS)-based radionuclide research at the KIT Light Source

Abstract. In the past two decades, X-ray absorption spectroscopy (XAS) and related synchrotron-based radionuclide speciation techniques have become indispensable, supporting open issues in fundamental radiochemistry and nuclear waste disposal alike. Physicochemical structure information – encoded in the element-specific X-ray absorption fine structure (XAFS) – is obtained by the precise determination of the linear mass absorption coefficient μ(E) of a specimen in an X-ray energy window ΔE encompassing an electronic bonding level of a selected atom type. The characteristic modulations of μ(E) in the vicinity of an “absorption edge” (i.e., the steeply rising absorption probability of photons tuned to the binding energy of inner shell “core” electrons) are attributed to electronic transitions into unoccupied states due to the photoelectric effect. While absorption features close to the edge (arising from excitations into molecular orbitals or empty band structure levels close to the Fermi level) are generally denoted as an X-ray absorption near-edge structure (XANES), the scattering states at higher excitation energies are causing the well-known extended X-ray absorption fine structure (EXAFS). EXAFS oscillations of the post-edge μ(E) are caused by the periodicity of the constructive and destructive interference of outbound and backscattered inbound photoelectron waves (superimposing at the absorbing atom site) when continuously increasing the excitation energy. Quantitative analysis of EXAFS data based on electron scattering theory is a well-established short-range structural probe, providing precise values of interatomic distances (between the absorber atom and its neighbors) and additional information on the type, number, and ordering of neighbor atoms within a local cluster. Recent significant advancements in the quantum theoretical description of core-excited final states have been successful in overcoming persisting ambiguities in XANES data interpretation. Meanwhile, although there are more than 50 synchrotron radiation centers operational in the world, facilities with specialized beamline infrastructure and safety protocols to allow experiments on radioactive samples with activities beyond the exemption limits are still scarce. At the KIT Light Source (at the Karlsruhe Institute of Technology, Karlsruhe, Germany), the Institute for Nuclear Waste Disposal (Institut für Nukleare Entsorgung, INE) operates two beamline end-stations dedicated to the investigation of radionuclide materials by XAFS spectroscopy and related techniques, i.e., the INE-Beamline (operational since 2005) and the ACT station of the CAT-ACT (CATalysis and ACTinide) wiggler beamline (operational since 2016). Samples with total activities amounting to 1.0×106 times the isotope specific exemption limits and 200 mg of fissile isotopes 235U and 239Pu are feasible at both beamlines. Highly versatile detection systems and sample holders – generally avoiding extensive shielding or sample handling in a glove box – have been conceived since the initial commissioning of the beamlines and have enabled unique XAFS measurements such as the first ever investigation of aqueous technetium species at the Tc L3 edge. Investigations of highly radioactive specimens (e.g., spent nuclear fuel or nuclear waste glass fragments) are feasible, regardless of the actual contact dose rate if the radiation field is limited to a few microsieverts per hour at the edge of the experimental table.

Determining Long-Term Probabilities for Labor Absorption from the Realization of Domestic Investment (PMDN) and Foreign Investment (PMA) in Indonesia Using Markov Chain Analysis

The government through President Joko Widodo in a press conference stated that the Job Creation Law is very urgent to be passed immediately, even though it has received a lot of resistance in society. The government stated that the bureaucracy in investing in Indonesia is still convoluted, so the possibility of a decrease in employment in the future is very high. However, this was denied by Faisal Basri. This reason is not in accordance with the current state of investment, he concluded. Realization of Domestic Investment (PMDN) and Foreign Investment (PMA) in Indonesia tends to always increase every year, so it is not the investment bureaucracy that is the cause of decreased employment. Abdul Malik said that, the reason for the decrease in absorption labor is the lack of competitiveness of the local workforce and the government's lack of selectiveness in choosing investments that enter Indonesia. This study aims to provide consideration for the government, in the form of long-term employment probabilities from the realization of PMDN and PMA in Indonesia which are calculated using Markov chain analysis. The calculation results obtained are that the long-term probability of increasing the amount of labor absorption from the realization of PMDN and PMA is 0.56 or 56%, while the long-term probability of decreasing is 0.44 or 44%. Then, in specific intervals, the possibility of an increase in the workforce of at most 93 thousand people is very high, namely 0.42 or 42%. This value is greater than the possibility of a decrease in the workforce of at most 93 thousand people, namely 0.27 or 27%. This value is contrary to the government's assumption which states that the possibility of a decrease in labor absorption is very high. Therefore, the results of this research can be used as one of the considerations for the government to rethink the urgency of issuing the Job Creation Law.

Optical properties and radiation shielding performance of tellurite glassy composites: Role of rare earth oxides

In this research, the synthesis, optical parameters, and radiation absorption quantities of 50TeO2–15Na2O—(20-x)PbO—15ZnO—xEu2O3 glasses were reported. The glasses were prepared by the well-known melting and quenching method using high purity chemicals. The glasses were coded as TPEu-0, TPEu-1, TPEu-2, and TPEu-3 for glasses containing 0, 1, 2, and 3 mol% of Eu2O3, respectively. The density of the glasses was determined by the Archimedes method. The optical parameters of the glasses, such as the refractive index n, molar refractivity Rm, molar polarizability αm, reflection loss RL, optical transmission T, metallization criterion M, static dielectric constant εstatic, and optical dielectric constant εoptical were estimated by theoretical methods. The stopping powers and range of electrons, protons, α-particles, and carbon ions in the TPEu-X glasses for particle kinetic energies between 15 keV and 15 MeV were computed using the ESTAR, PSTAR, ASTAR, and STRIM software. In addition, the fast neutron (FN) removal cross section (FNRCS), thermal neutron (TN), and total cross-section (σtot) for the prepared glasses were evaluated theoretically using established models. The estimated optical parameters showed strong relationship with the chemical content of the glasses. Glass density and molar volume increased as Eu2O3 content increased. The Rm, αm, RL, εstatic, and εoptical vary from 16.24 to 17.20 cm3/mol, 6.44 × 10−24 cm3‒17.20 × 10−24 cm3, 0.17–0.19, 5.71–6.55, and 4.71–5.55 respectively, with TPEu-0 and TPEu-1 having the maximum and minimum values, respectively. Generally, the increase in Eu2O3 concentration increased the charged radiation shielding ability of the glasses. The increment in the Eu2O3 content of the glasses brought about an improvement in the thermal and fast neutron absorption probabilities of the glasses.

Challenging event horizons with spin (3/2) fields

We attempt to destroy the event horizons of Kerr black holes by perturbing them with massless spin (3/2) fields. We carry out a detailed analysis by incorporating the explicit form of the absorption probabilities and backreaction effects due to the self energy of the test fields. For extremal and nearly extremal black holes, backreaction effects dominate for perturbations with large magnitudes. However, small perturbations can destroy the event horizons of extremal black holes and drive nearly extremal black holes closer to extremality. Eventually, nearly extremal black holes reach a certain stage where they can be continuously driven to extremality and beyond. Both the cosmic censorship conjecture and the third law of black hole dynamics can be violated by spin (3/2) fields. This directly follows from the fact that fermionic fields do not satisfy the null energy condition. Therefore this result does not contradict with the fact that cosmic censorship and the laws of black hole mechanics remain valid for perturbations satisfying the null energy condition.

Grassmann Angles and Absorption Probabilities of Gaussian Convex Hulls

Grassmann Angles and Absorption Probabilities of Gaussian Convex Hulls

Using In Silico Approach for Metabolomic and Toxicity Prediction of Alternariol.

Alternariol is a metabolite produced by Alternaria fungus that can contaminate a variety of food and feed materials. The objective of the present paper was to provide a prediction of Phase I and II metabolites of alternariol and a detailed ADME/Tox profile for alternariol and its metabolites using an in silico working model based on the MetaTox, SwissADME, pKCMS, and PASS online computational programs. A number of 12 metabolites were identified as corresponding to the metabolomic profile of alternariol. ADME profile for AOH and predicted metabolites indicated a moderate or high intestinal absorption probability but a low probability to penetrate the blood-brain barrier. In addition to cytotoxic, mutagenic, carcinogenic, and endocrine disruptor effects, the computational model has predicted other toxicological endpoints for the analyzed compounds, such as vascular toxicity, haemato-toxicity, diarrhea, and nephrotoxicity. AOH and its metabolites have been predicted to act as a substrate for different isoforms of phase I and II drug-metabolizing enzymes and to interact with the response to oxidative stress. In conclusion, in silico methods can represent a viable alternative to in vitro and in vivo tests for the prediction of mycotoxins metabolism and toxicity.

Arrays of Fresnel Nanosystems for Enhanced Photovoltaic Performance.

Omnidirectional broadband absorption of the solar radiation is pivotal to solar energy harvesting and particularly to low-cost non-tracking photovoltaic (PV) technologies. The current work numerically examines the utilization of surface arrays composed of Fresnel nanosystems (Fresnel arrays), which are reminiscent of the known Fresnel lenses, for the realization of ultra-thin silicon PV cells. Specifically, the optical and electrical performances of PV cells integrated with Fresnel arrays are compared with those of a PV cell incorporated with an optimized surface array of nanopillars (NP array). It is shown that the broadband absorption of specifically tailored Fresnel arrays can provide an enhancement of ∼20% over that of an optimized NP array. The performed analysis suggests that broadband absorption in ultra-thin films decorated with Fresnel arrays is driven by two light trapping mechanisms. The first is light trapping governed by light concentration, induced by the arrays, into the underlying substrates, which increases the optical coupling between the impinging illumination and the substrates. The second mechanism is light trapping motivated by refraction, as the Fresnel arrays induce lateral irradiance in the underlying substrates, which increases the optical interaction length and hence the overall probability for optical absorption. Finally, PV cells incorporated with surface Fresnel arrays are numerically calculated, with short-circuit current densities (Jsc) which are ∼50% higher than that of a PV cell incorporated with an optimized NP array. Also, the effect of increased surface area, due to the presence of Fresnel arrays, and its effect on surface recombination and open-circuit voltage (Voc) are discussed.

Close encounters of the sticky kind: Brownian motion at absorbing boundaries.

Encounter-based models of diffusion provide a probabilistic framework for analyzing the effects of a partially absorbing reactive surface, in which the probability of absorption depends upon the amount of surface-particle contact time. In this paper we develop a class of encounter-based models that deal with absorption at sticky boundaries. Sticky boundaries occur in a diverse range of applications, including cell biology, colloidal physics, finance, and human crowd dynamics. They also naturally arise in active matter, where confined active particles tend to spontaneously accumulate at boundaries even in the absence of any particle-particle interactions. We begin by constructing a one-dimensional encounter-based model of sticky Brownian motion (BM), which is based on the zero-range limit of nonsticky BM with a short-range attractive potential well near the origin. In this limit, the boundary-contact time is given by the amount of time (occupation time) that the particle spends at the origin. We calculate the joint probability density or propagator for the particle position and the occupation time, and then identify an absorption event as the first time that the occupation time crosses a randomly generated threshold. We illustrate the theory by considering diffusion in a finite interval with a partially absorbing sticky boundary at one end. We show how various quantities, such as the mean first passage time (MFPT) for single-particle absorption and the relaxation to steady state at the multiparticle level, depend on moments of the random threshold distribution. Finally, we determine how sticky BM can be obtained by taking a particular diffusion limit of a sticky run-and-tumble particle (RTP).

Low-cost photoreactors for highly photon/energy-efficient solar-driven synthesis

Low-cost photoreactors for highly photon/energy-efficient solar-driven synthesis

Antiparasitic Activity of Plumbago auriculata Extracts and Its Naphthoquinone Plumbagin against Trypanosoma cruzi.

Chagas disease (CD) caused by the protozoan Trypanosoma cruzi affects more than six million people worldwide. Treatment is restricted to benznidazole (Bz) and nifurtimox (Nf) that display low activity in the later chronic stage besides triggering toxic events that result in treatment abandonment. Therefore, new therapeutic options are necessary. In this scenario, natural products emerge as promising alternatives to treat CD. In the family Plumbaginaceae, Plumbago sp. exhibits a broad spectrum of biological and pharmacological activities. Thus, our main objective was to evaluate, in vitro and in silico, the biological effect of crude extracts of root and of aerial parts of P. auriculata, as well as its naphthoquinone Plumbagin (Pb) against T. cruzi. The phenotypic assays revealed potent activity of the root extract against different forms (trypomastigote and intracellular forms) and strains (Y and Tulahuen), with a compound concentration that reduced 50% of the number of the parasite (EC50) values ranging from 1.9 to 3.9 µg/mL. In silico analysis showed that Pb is predicted to have good oral absorption and permeability in Caco2 cells, besides excellent probability of absorption by human intestinal cells, without toxic or mutagenic potential effects, not being predicted as a substrate or inhibitor of P-glycoprotein. Pb was as potent as Bz against intracellular forms and displayed a superior trypanosomicidal effect (about 10-fold) in bloodstream forms (EC50 = 0.8 µM) as compared to the reference drug (8.5 µM). The cellular targets of Pb on T. cruzi were evaluated using electron microscopy assays and the findings on bloodstream trypomastigotes showed several cellular insults related to the autophagic process. Regarding toxicity in mammalian cells, the root extracts and the naphthoquinone present a moderate toxic profile on fibroblasts and cardiac cell lines. Then, aiming to reduce host toxicity, the root extract and Pb were tested in combination with Bz, and the data showed additive profiles with the sum of the fractional inhibitory concentration indexes (ΣFICIs) being 1.45 and 0.87, respectively. Thus, our work reveals the promising antiparasitic activity of Plumbago auriculata crude extracts and its purified naphthoquinone Plumbagin against different forms and strains of Trypanosoma cruzi in vitro.

Stimulated-emission cross-sections of trivalent erbium ions in the cubic sesquioxides Y2O3, Lu2O3, and Sc2O3

We report on a detailed revision of the spectroscopic properties of Er3+ ions in the cubic sesquioxide host crystals R2O3 (R = Y, Lu and Sc). The 4f-4f transition probabilities are calculated by applying a modified Judd-Ofelt theory accounting for configuration interaction based on the measured absorption spectra. The stimulated-emission cross-sections for the 4I11/2 → 4I13/2 (at ∼2.8 µm) and 4I13/2 → 4I15/2 (at ∼1.6 µm) transitions of Er3+ ions are determined and the luminescence dynamics from the 4I11/2 and 4I13/2 manifolds are studied at different temperatures. It is found that the luminescence lifetime of the 4I11/2 state strongly depends on the host-forming R3+ cation even at low temperatures due to a non-negligible non-radiative multiphonon decay channel. Er:Y2O3 exhibits the lowest phonon energies and consequently the longest 4I11/2 luminescence lifetimes. A disagreement between the absorption and emission probabilities for the 4I15/2 ↔ 4I11/2 transition of Er3+ ions is observed at room temperature and explained considering the distribution of Er3+ ions over two non-equivalent crystallographic sites, C2 and C3i.

Low-energy solar neutrino detection utilizing advanced germanium detectors

We explore the possibility to use advanced germanium (Ge) detectors as a low-energy solar neutrino observatory by means of neutrino-nucleus elastic scattering. A Ge detector utilizing internal charge amplification for the charge carriers created by the ionization of impurities is a novel technology with experimental sensitivity for detecting low-energy solar neutrinos. Ge internal charge amplification (GeICA) detectors will amplify the charge carriers induced by neutrino interacting with Ge atoms through the emission of phonons. It is those phonons that will create charge carriers through the ionization of impurities to achieve an extremely low energy threshold of ∼0.01 eV. We demonstrate the phonon absorption, excitation, and ionization probability of impurities in a Ge detector with impurity levels of 3 × 1010 cm−3, 9 × 1010 cm−3, and 2 × 1011 cm−3. We present the sensitivity of such a Ge experiment for detecting solar neutrinos in the low-energy region. We show that, if GeICA technology becomes available, then a new opportunity arises to observe pp and 7Be solar neutrinos. Such a novel detector with only 1 kg of high-purity Ge will give ∼10 events per year for pp neutrinos and ∼5 events per year for 7Be neutrinos with a detection energy threshold of 0.01 eV.

Encounter-based model of a run-and-tumble particle II: absorption at sticky boundaries

In this paper we develop an encounter-based model of a run-and-tumble particle (RTP) confined to a finite interval with partially absorbing, sticky boundaries at both ends. We assume that the particle switches between two constant velocity states ±v at a rate α. Whenever the particle hits a boundary, it becomes stuck by pushing on the boundary until either a tumble event reverses the swimming direction or it is permanently absorbed. We formulate the absorption process by identifying the first passage time (FPT) for absorption with the event that the time A(t) spent attached to either wall up to time t (the occupation time) crosses some random threshold . Taking to be an exponential distribution, , we show that the joint probability density for particle position X(t) and velocity state satisfies a well-defined boundary value problem (BVP) with κ 0 representing a constant absorption rate. The solution of this BVP determines the so-called occupation time propagator, which is the joint probability density for the triplet . The propagator is then used to incorporate more general models of absorption based on non-exponential (non-Markovian) distributions . We illustrate the theory by calculating the mean FPT and splitting probabilities for absorption. We also show how our previous results for partially absorbing, non-sticky boundaries can be recovered in an appropriate limit. Absorption now depends on the number of collisions of the RTP with the boundary. Finally, we extend the theory by taking absorption to depend on the individual occupation times at the two ends.