Energy-dependent Effects Research Articles

Applicability of an Ionising Radiation Measuring System for Real-Time Effective-Dose-Optimised Route Finding Solution during Nuclear Accidents

The reduction in the effective dose of evacuated injured persons through contaminated areas of nuclear accidents is an essential emergency services requirement. In this context, there appeared a need to develop a dose-optimised route finding method for firefighting rescue vehicles, which includes the development of a real-time decision support measurement and evaluation system. This determines and visualises the radiation exposure of possible routes in a tested area. The system inside and outside of the vehicle measures the ambient dose equivalent rate, the gamma spectra, and also the airborne radioactive aerosol and iodine levels. The method uses gamma radiation measuring NaI(Tl) scintillation detectors mounted on the outside of the vehicle, to determine the dose rate inside the vehicle using the previously recorded attenuation conversation function, while continuously collecting the air through a filter and using an alpha, beta, and gamma radiation measuring NaI(Tl)+ PVT + ZnS(Ag) scintillator to determine the activity concentration in the air, using these measured values to determine the effective dose for all routes and all kinds of vehicles. The energy-dependent shielding effect of the vehicle, the filtering efficiency of the collective protection equipment, and the vehicle’s speed and travel time were taken into account. The results were validated by using gamma point sources with different activity and energy levels. The measurement results under real conditions and available real accident data used in our simulations for three different vehicles and pedestrians proved the applicability of the system. During a nuclear accident based on our model calculations, the inhalation of radioactive aerosols causes a dose almost an order of magnitude higher than the external gamma radiation caused by the fallout contamination. The selection of the appropriate vehicle and its route is determined by the spectrum that can be measured at the accident site but especially by the radioactive aerosol concentration in the air that can be measured in the area. In the case of radiation measuring detectors, the shielding effect of the carrier vehicle must be taken into account, especially in the case of heavy shielding vehicles. The method provides an excellent opportunity to reduce the damage to the health of accident victims and first responders during rescue operations.

First-principles quantum computational study to investigate radiation energy-dependent effect on optoelectronic properties of bismuth oxyhalides BiOX (X= I, Br)

Metal oxyhalides are potential candidates for fundamental and technological interest in pharmaceutical, biological, optical, photoluminance, sensing, energy, and photocatalyst applications. In this study, using first-principles density functional quantum computational approach, we investigate the electronic and optical properties of two members of bismuth oxyhalides, BiOX (X = I, Br). The study is mainly aimed to characterize and examine the light radiation energy-dependent optical properties of the compounds by using mBJ desnty functional with the full potential linearized augmented plane wave method. The oxyhalides show indirect bandgap semiconductor nature having bandgaps of 2.2 eV for BiOI and 3.5 eV for BiOBr. Besides, these are p-type materials owing to a large hole-like carrier density of states in the valence bands close to the Fermi level. The energy bands show considerable dispersion of particles. The increasing reflectivity at high light energy shows the potential of the materials as good reflectors in shielding screens or glasses to avoid damage from the ultraviolet radiation.

Measurement of the size of the gamma-ray source in blazar B0218+357 based on microlensing at the 100 GeV energy band

Context. Observations of the effect of microlensing in gravitationally lensed quasars can be used to study the structure of active galactic nuclei on distance scales down to the sizes of a supermassive black hole’s powering source activity. Aims. We searched for a microlensing effect in the signal from a gravitationally lensed blazar, B0218+357, in a very-high-energy γ-ray band. Methods. We combined observations of a bright flare of the source in 2014 by the Fermi Large Area Telescope and MAGIC telescopes in the 0.1 − 300 GeV and 65 − 175 GeV energy ranges, respectively. Using the time-delayed leading and trailing signals from two gravitationally lensed images of the source, we measured the magnification factor at the moment of the flare. We used the scaling of the maximal magnification factor with the source size to constrain the size of the γ-ray emission region in the wide 0.1 − 175 GeV energy range. Results. The magnification factor in the very-high-energy band that we derived from our comparison of Fermi/LAT and MAGIC data is μVHE = 25−17+38, which is substantially larger than the factor found in the radio band. This suggests one of the source images is strongly affected by microlensing at the moment of the flare. Assuming that the microlensing is produced by a stellar mass object in the lens galaxy, we constrained the size of the emission region in the E > 100 GeV band to be RVHE = 6.6−5.6+69 × 1014 cm. We note that the spectrum of the microlensed source was unusually hard at the moment of the flare, and we speculate that this hardening may be due to the energy-dependent microlensing effect. This interpretation suggests that the source size decreases with energy in the entire 0.1 − 175 GeV energy range we studied.

Extracorporeal shock wave therapy: options in chronic osteomyelitis (literature review)

The use of extracorporeal shock wave therapy under experimental conditions has shown the effectiveness of the method in soft tissue and skeletal infections. In vitro, an energy-dependent effect of shock waves on reducing the viability of Staphylococcus aureus and other pathogenic flora was revealed. For the manifestation of the antibacterial activity of shock waves towards pathogenic bacteria of the typical flora in chronic osteomyelitis, at least 1,000 pulses were required, and for its almost complete eradication (99 %), 4,000 pulses were applied at an energy flux density of 0.59–0.96 mJ/mm2. Most authors confirm the isolated (without antibiotics) antibacterial effect of shock waves in vitro, although there are opposite opinions. It is known that pathogenic bacteria, including Staphylococcus aureus, form protective biofilms on infected soft, bone tissues, implants. Due to this, the emerging infection is difficult to treat for a number of reasons — the biofilm prevents the penetration of antibiotics and immune cells. In vitro studies have shown that shock waves destroy biofilms of pathogenic bacteria and create conditions for a joint bactericidal effect with antibiotics. In vivo observations under the conditions of modeling experimental osteomyelitis in animals have demonstrated bacteriologically that extracorporeal shock wave therapy, when used alone, does not have an antibacterial effect, however, a lower degree of osteomyelitis was detected morphologically. The authors stated the synergism of shock waves with antibiotics in the treatment of chronic osteomyelitis in animals, up to the bactericidal effect. Studies on the impact of shock waves on biofilms of pathogenic bacteria typical for soft tissue infections, chronic osteomyelitis, both in vivo and in vitro, showed that after the application of the method, the pathogenic flora becomes susceptible to antibiotic therapy. The currently widespread opinion about the contraindication of extracorporeal shock wave therapy in the presence of infection in the body, due to the risk of exacerbation of the inflammatory process, the likelihood of bacteremia, sepsis, and foci of secondary infection, has not been confirmed in the experimental studies in vivo. Many research have shown the absence of similar or other complications in animals after the use of shock waves. The analysis of the presented data indicates the need for further study of the mechanism of extracorporeal shock wave effect on chronic osteomyelitis, possible complications associated with the use of the method, as well as its approbation in the clinic.

Analytical energy formalism and kinetic effects of grain boundaries: A case study of graphene

Grain boundaries (GBs), inherent in polycrystalline materials, manifest a diverse array of features that substantially affect material properties. However, the incomplete knowledge of the relevance between structures and energetics of GBs impedes the understanding of their effects. Here, taking graphene as an example, we propose an analytical energy formula for GBs in grain-boundary angle space. Our study reveals that any given GB can be characterized by a geometric combination of symmetric GBs, adhering to the principle of uniformly distributing their dislocation cores along straight trajectories. The formation probability of GBs, as predicted by our theoretical derivation, aligns well with both high-throughput calculations and experimental statistics. Furthermore, we unveil the elusive kinetic effects on GBs by contrasting experimental statistics with energy-dependent thermodynamic effects. This study not only presents a robust model to describe energetically favorable GBs in graphene, offering insight into the formation of GBs in two-dimensional materials, but also reveals the kinetic effects of GBs in material synthesizing process.

Systematic study of the fusion hindrance phenomenon using the proximity potential approach: signature of the energy-dependent effects of the surface energy coefficient

In the present study, we have systematically studied the role of surface energy coefficient as well as temperature dependence in the fusion hindrance phenomenon of the heavy-ion reactions using the proximity potential formalism. To this end, we have performed the calculations of the interaction potential using the original proximity potential 1977 (Prox. 77) and the fusion cross sections are calculated based on the coupled-channels (CC) approach. The considered fusion systems are including the heavy-ion reactions 11B+197Au, 12C+198Pt, 16O+208Pb, 28Si + 64Ni, 28Si + 94Mo, 58Ni+58Ni, 32S+89Y,34S+89Y, 12C+204Pb and 36S + 64Ni with conditions of Q <0 and charge product of the participant nuclei 392≤ Z1Z2 ≤784. Our preliminary calculations show the Prox. 77 model predicts the theoretical values ​​of the fusion cross-sections less than the corresponding experimental data especially in the energy regions below the fusion barrier. However, the imposing of the mentioned physical effects increases the calculated values of the fusion cross sections and thus improves their agreement with the experimental cross sections for the selected reactions. In addition, by considering the energy dependence on the surface energy constant γ0 of the proximity formalism at the low energy region we are able to reproduce well the fusion cross sections, the astrophysical factor S(E) as well as the logarithmic derivative L(E) in these regions.‎

Inertial energy dissipation in nuclear dynamics

We present the TDDFT+Langevin model that incorporates microscopic time-dependent density function theory (TDDFT) with macroscopic Langevin model. By extracting the energy-dependent dissipation effect from the TDDFT dynamics, quantum effects are introduced to the Langevin-type stochastic fission analysis. In this paper, by means of Skyrme nuclear effective interactions, the energy-dependent friction coefficients to be used in Langevin calculations are provided individually for 25 fission nuclei chosen from uranium, plutonium, curium, californium, and fermium isotopes. The validity of the energy-dependent friction coefficients are confirmed by comparing to the existing experimental fission fragment yields. In conclusion, depending on the energy, the transition of energy dissipation mechanism from conventional viscous energy dissipation to inertial energy dissipation is shown.

Low-intensity Extracorporeal Shockwave Therapy as an Adjunct to Xiaflex® in the Treatment of Peyronie's Disease

ABSTRACT Introduction Low-intensity extracorporeal shockwave therapy (Li-ESWT) may have physiologic effects including neo-angiogenesis, upregulation of vasoactive endothelial growth factors, nerve recovery, reduction of fibrotic changes, cavernosal tissue remodeling, and reduction in sympathetic tone. Collagenase clostridium histolyticum (CCH) is the only US FDA-approved drug for the non-surgical treatment of Peyronie's disease (PD). Treatment is intended to be completed in conjunction with penile traction therapy, but studies have demonstrated poor patient compliance. New adjunct therapies that have synergistic effects when used in combination with CCH are desirable but have not been explored. Objective To study if Li-ESWT has additive, synergistic, or no effect when used in combination with CCH to treat PD-associated fibrosis and PD-associated erectile dysfunction. Methods 40 adult male Sprague-Dawley rats were divided evenly into five groups: sham (S), control (T), CCH only (XT), low setting Li-ESWT and CCH (XTL), and CCH and high setting Li-ESWT (XTH). Normal saline was injected sub-tunical in the sham group. Transforming growth factor beta-1 (TGF-B1) was injected into the tunica albuginea of the remaining groups to induce Peyronies-like fibrosis. After 4 weeks of TGF-B1 induction, CCH was injected in all three groups over two injections separated by 48 hours, and then treatment with Li-ESWT (UroGold™ 100) was initiated. Treatment was delivered biweekly for 3 weeks (6 total sessions). Device settings were 600 shocks at 3 Hz, at level 6 (0.093 mJ/mm2) for the XTL group and at level 12 (0.125 mJ/mm2) for the XTH group. After 10 weeks, erectile function was measured by ratio of intracavernosal pressure (ICP) to mean arterial pressure (MAP). Histological analysis by H&amp;E, Trichome stain, and Western blot analysis of Collagen I (COL1A1), III (COL3A1), and alpha-smooth muscle actin (a-SMA) were also performed. Results There was no significant difference found in erectile function as measured by ICP/MAP between PD model and treatment groups (P &amp;gt; 0.05). Histological comparison showed no significant reduction of fibrosis when Li-ESWT was added to CCH, despite intensity, on microscopic examination. On Western blot analysis, there was a reduction of ∼500% in COL1A1 expression when the XT group was compared to the T group. While there was no significant change of COL1A1 between the XT group and the XTL group, there was found to be a decrease of ∼500% expression when the XT group was compared to the XTH group. Expression of COL3A1 in the treatment groups XTL and XTH was comparable to that of the XT group. There was no observable trend in a-SMA expression. Conclusions Different adjunct treatments to CCH need to be explored to augment the effect of the only approved non-surgical treatment for PD. Decreased COL1A1 expression seen in the XTH group, but not XTL, relative to the T group may suggest an energy-dependent effect to decrease fibrosis. Li-ESWT was hypothesized to be a promising candidate, but we have failed to show substantial benefit in our proposed setting. Disclosure Yes, this is sponsored by industry/sponsor: Sexual Medicine Society of North America Clarification Industry funding only - investigator initiated and executed study Any of the authors act as a consultant, employee or shareholder of an industry for: Endo Pharmaceuticals

Improved version of the α -nucleus optical model potential for reactions relevant to the γ process

The present paper proposes an improved version of the $\ensuremath{\alpha}$-nucleus optical model potential ($\ensuremath{\alpha}$-OMP), in which the real part of the potential is determined by the double-folding calculation using the density-dependent CDM3Y1 interaction plus a repulsive potential. The imaginary part of the $\ensuremath{\alpha}$-OMP is treated by a Woods-Saxon form with energy-dependent depth, while its real part is corrected by including the contribution of the dispersion relation derived from the strong variation of the potential at energies in the vicinity of the Coulomb barrier. The proposed potential is validated by calculating the $(\ensuremath{\alpha},n)$ and $(\ensuremath{\alpha},\ensuremath{\gamma})$ cross sections on different target nuclei and the obtained results are compared with those predicted by the recent $\ensuremath{\alpha}$-OMP suggested by Avrigeanu, as well as the available experimental data. The impacts of the energy-dependent imaginary part and the real dispersive term on the $\ensuremath{\alpha}$-induced cross sections are also investigated. The results obtained show that the proposed $\ensuremath{\alpha}$-OMP together with that of Avrigeanu describe reasonably well the experimental cross sections of all $(\ensuremath{\alpha},n)$ reactions being considered. In addition, the imaginary part of the proposed potential has a strong energy-dependent effect on the $\ensuremath{\alpha}$-induced cross section in the energy region below the Coulomb barrier, in particular for radiative $\ensuremath{\alpha}$-capture reactions. Two potentials also describe well the cross sections of $(\ensuremath{\alpha},\ensuremath{\gamma})$ reactions after rescaling the radiative $\ensuremath{\gamma}$ width. This leads to our conclusion that the present $\ensuremath{\alpha}$-OMP can provide precise $\ensuremath{\alpha}$ widths for the study of reactions relevant to the production of $p$ nuclei, and therefore more intensive theoretical research on the radiative strength functions is required.

The Effect of the Flux Separability Approximation on Multigroup Neutron Transport

The angular dependence of flux-weighted multigroup cross sections is commonly neglected when generating multigroup libraries. The error of this flux separability approximation is typically not isolated from other error sources due to a lack of availability of library generation and corresponding solvers that cannot relax this approximation. These errors can now be isolated and quantified with the availability of a multigroup Monte Carlo transport and multigroup library-generation capability in the OpenMC Monte Carlo transport code. This work will discuss relevant details of the OpenMC implementation, provide an example case useful for detailing the type of errors one can expect from making the flux separability approximation, and end with more realistic problems which show the impact of the approximation and highlight how it can strongly arise from an energy-dependent resonance absorption effect. Since the angle-dependence is intrinsically linked to the energy group structure, these examples also show that relaxing the flux separability approximation with angle-dependent cross sections could be used to reduce either the fine-tuning required to set a multigroup energy structure for a specific reactor type or the number of energy groups required to obtain a desired level of accuracy for a given problem. This trade-off could increase the costs of generating multigroup cross sections, and has the potential to require more memory for storing the multigroup library during the transport calculations, but it can significantly reduce the computational time required since the runtime of a discrete ordinates or method of characteristics neutron transport solver scales roughly linearly with the number of groups.

Band Nesting in Two-Dimensional Crystals: An Exceptionally Sensitive Probe of Strain.

Band nesting occurs when conduction and valence bands are approximately equispaced over regions in the Brillouin zone. In two-dimensional materials, band nesting results in singularities of the joint density of states and thus in a strongly enhanced optical response at resonant frequencies. We exploit the high sensitivity of such resonances to small changes in the band structure to sensitively probe strain in semiconducting transition metal dichalcogenides (TMDs). We measure and calculate the polarization-resolved optical second harmonic generation (SHG) at the band nesting energies and present the first measurements of the energy-dependent nonlinear photoelastic effect in atomically thin TMDs (MoS2, MoSe2, WS2, and WSe2) combined with a theoretical analysis of the underlying processes. Experiment and theory are found to be in good qualitative agreement displaying a strong energy dependence of the SHG, which can be exploited to achieve exceptionally strong modulation of the SHG under strain. We attribute this sensitivity to a redistribution of the joint density of states for the optical response in the band nesting region. We predict that this exceptional strain sensitivity is a general property of all 2D materials with band nesting.

High-Resolution Photoelectron Spectroscopy of Cryogenically Cooled NO3̅.

High-resolution anion photoelectron spectra of cryogenically cooled NO3̅ anions obtained using slow photoelectron velocity-map imaging are presented and provide new insight into the vibronic structure of the corresponding neutral radical. A combination of improved spectral resolution, measurement of energy-dependent intensity effects, temperature control, and comparison to theory allows for full assignment of the vibronic features observed in this spectrum. We obtain a refined electron affinity of 3.9289(14) eV for NO3. Further, the appearance of Franck-Condon forbidden transitions from vibrationally cold anions to neutral states with excitation along the NO3 ν4 mode confirms that these features arise from vibronic coupling with the B̃2E' excited state of NO3 and are not hot bands, as has been suggested. Together, the suite of experimental and simulated results provides clear evidence that the ν3 fundamental of NO3 resides near 1050 cm-1, addressing a long-standing controversy surrounding this vibrational assignment.

Energy-dependent effect trial of photobiomodulation on blood pressure in hypertensive rats.

The main purpose of this work was to construct an energy-dependent response curve of photobiomodulation on arterial pressure in hypertension animal model. To reach this objective, we have used a two-kidney one clip (2K-1C) rat model. Animals received acute laser light irradiation (660nm) on abdominal region using different energy (0.6, 1.8, 3.6, 7.2, 13.8, 28.2, 55.8, and 111.6J), the direct arterial pressure was measured by femoral cannulation, and systolic arterial pressure (SAP), diastolic arterial pressure (DAP), heart rate (HR), and time of effect were obtained. Our results indicated that 660nm laser light presents an energy-dependent hypotensive effect, and 28.2J energy irradiation reached the maximum hypotensive effect, inducing a decreased SAP, DAP, and HR (decrease in SAP: - 19.23 ± 1.82mmHg, n = 11; DAP: - 9.57 ± 2.23mmHg, n = 11; HR: - 39.15 ± 5.10bpm, n = 11; and time of hypotensive effect: 3068.00 ± 719.00s, n = 11). The higher energy irradiation evaluated (111.6J) did not induce a hypotensive effect and induced an increase in HR (21.69 ± 7.89bpm, n = 7). Taken together, our results indicate that red laser energy irradiation from 7.2 to 55.8J is the effective therapeutic window to reduce SAP, DAP, MAP, and HR and induce a long-lasting hypotensive effect in rats, with effect loss at higher energy irradiation (111.6J).

A robust excess in the cosmic-ray antiproton spectrum: Implications for annihilating dark matter

An excess of $\sim$10-20 GeV cosmic-ray antiprotons has been identified in the spectrum reported by the AMS-02 Collaboration. The systematic uncertainties associated with this signal, however, have made it difficult to interpret these results. In this paper, we revisit the uncertainties associated with the time, charge and energy-dependent effects of solar modulation, the antiproton production cross section, and interstellar cosmic-ray propagation. After accounting for these uncertainties, we confirm the presence of a 4.7$\sigma$ antiproton excess, consistent with that arising from a $m_{\chi} \approx 64-88$ GeV dark matter particle annihilating to $b\bar{b}$ with a cross section of $\sigma v \simeq (0.8-5.2) \times 10^{-26}$ cm$^{3}$/s. If we allow for the stochastic acceleration of secondary antiprotons in supernova remnants, the data continues to favor a similar range of dark matter models ($m_{\chi}\approx 46-94$ GeV, $\sigma v \approx (0.7-3.8)\times 10^{-26}$ cm$^3/$s) with a significance of 3.3$\sigma$. The same range of dark matter models that are favored to explain the antiproton excess can also accommodate the excess of GeV-scale gamma rays observed from the Galactic Center.

Electron-Phonon Coupling from AbInitio Linear-Response Theory within the GW Method: Correlation-Enhanced Interactions and Superconductivity in Ba_{1-x}K_{x}BiO_{3}.

We present a new first-principles linear-response theory of changes due to perturbations in the quasiparticle self-energy operator within the GW method. This approach, named GW perturbation theory (GWPT), is applied to calculate the electron-phonon (e-ph) interactions with the full inclusion of the GW nonlocal, energy-dependent self-energy effects, going beyond density-functional perturbation theory. Avoiding limitations of the frozen-phonon technique, GWPT gives access to e-ph matrix elements at the GW level for all phonons and scattering processes, and the computational cost scales linearly with the number of phonon modes (wave vectors and branches) investigated. We demonstrate the capabilities of GWPT by studying the e-ph coupling and superconductivity in Ba_{0.6}K_{0.4}BiO_{3}. We show that many-electron correlations significantly enhance the e-ph interactions for states near the Fermi surface, and explain the observed high superconductivity transition temperature of Ba_{0.6}K_{0.4}BiO_{3} as well as its doping dependence.

Optical Properties of Energy-Dependent Effective Mass GaAs/GaxIn1−xAs and GaAs/AlxGa1−xAs Quantum Well Systems: A Shooting Method Study

In this paper, we study the effect of energy-dependent effective mass on optical properties of GaAs/GaxIn1−xAs and GaAs/AlxGa1−xAs quantum well systems through the compact density matrix approach. We solved the resulting nonlinear Schrodinger equation by a simple shooting method and present the algorithm. We show that the energy-dependent effective mass effect is more important for systems with narrower quantum well systems. By an energy-dependent effective mass assumption, absorption coefficient peak height increases with increasing the total system length L while in the constant effective mass limit, absorption coefficient peak heights have not been influenced by changing L. In the GaAs/AlxGa1−xAs system, by increasing the number of wells, the linear absorption coefficient amplitude at first increases and then decreases in the fixed effective mass approximation and monotonically decreases in the energy-dependent effective mass case. By increasing the number of wells, the linear absorption coefficient peak position at first shows a blue shift and then shows a redshift. In the GaAs/GaxIn1−xAs system, the situation is more complicated and it is described in more detail in the text. However, GaAs/GaxIn1−xAs quantum well systems have larger values of absorption coefficient peak heights than GaAs/AlxGa1−xAs ones.

How the NEUWAVE workshop series has pushed neutron imaging developments

ABSTRACTIn 2008, a series of international workshops—named NEUtron WAVElength-dependent Imaging (NEUWAVE)—was initiated after several decisions were taken to build new neutron spallation sources in the world, namely target station two of ISIS in the UK, J-PARC in Japan, SNS in the US, and the future ESS, now being built in Sweden. The aim was to collect existing knowledge about energy-dependent effects in neutron imaging, but also to develop new energy-selective imaging methods for the upcoming spallation sources, and also for steady-state sources using energy selecting devices for neutrons. The special format was a workshop with plenty of discussions but without explicit publications, where participants discussed not their past work, but their ideas and future plans. This paper gives a résumé after nine such meetings and highlights the most important progress features. The series will continue in 2019 with NEUWAVE-10 to be organized by Paul Scherrer Institut.

Highly (00l)-oriented Bi2Te3/Te heterostructure thin films with enhanced power factor.

Introducing nanoscale heterostructure interfaces into material matrix is an effective strategy to optimize the thermoelectric performance by energy-dependent carrier filtering effect. In this study, highly (00l)-oriented Bi2Te3/Te heterostructure thin films have been fabricated on single-crystal MgO substrates using a facile magnetron co-sputtering method. Bi2Te3/Te heterostructure thin films with Te contents of 63.8 at% show an optimized thermoelectric performance, which possess a Seebeck coefficient of -157.7 μV K-1 and an electrical conductivity of 9.72 × 104 S m-1, leading to a high power factor approaching 25 μW cm-1 K-2. The partially decoupled behavior of the Seebeck coefficient and electrical conductivity is contributed to Bi2Te3/Te heterostructure interfaces, which causes interfacial barrier filtering and scattering effects; thus, a high level of the Seebeck coefficient is obtained. Meanwhile, carrier transport in a-b plane can benefit from the highly preferred orientation, which guarantees a remarkably high electrical conductivity. We anticipate that our strategy may guide the way for preparing high-performance thermoelectric materials by microstructure design and regulation.

Theoretical study on collision dynamics of H+ + H2O at low energies

ABSTRACTScattering dynamics of a water molecule in collision with proton is studied based on a time-dependent density functional theory and coupled with the molecular dynamics method, in which the electrons are described by quantum mechanics and the nuclei are described by classical mechanics. Four different incident directions at 46 eV are chosen in order to investigate the orientations effect, and the energy-dependent effect in low energy region is explored under impact energies 27, 36 and 46 eV. Reaction channels, scattering angles and energy loss of protons are calculated. The differences between those characteristics are unobvious in large impact parameters, which are irrespective of the incident orientations due to weak projectile-target interaction. In small impact parameters, the results strongly depend on the collision energy and orientation.

Possible evidence for the stochastic acceleration of secondary antiprotons by supernova remnants

The antiproton-to-proton ratio in the cosmic-ray spectrum is a sensitive probe of new physics. Using recent measurements of the cosmic-ray antiproton and proton fluxes in the energy range of 1-1000 GeV, we study the contribution to the $\bar{p}/p$ ratio from secondary antiprotons that are produced and subsequently accelerated within individual supernova remnants. We consider several well-motivated models for cosmic-ray propagation in the interstellar medium and marginalize our results over the uncertainties related to the antiproton production cross section and the time-, charge-, and energy-dependent effects of solar modulation. We find that the increase in the $\bar{p}/p$ ratio observed at rigidities above $\sim$ 100 GV cannot be accounted for within the context of conventional cosmic-ray propagation models, but is consistent with scenarios in which cosmic-ray antiprotons are produced and subsequently accelerated by shocks within a given supernova remnant. In light of this, the acceleration of secondary cosmic rays in supernova remnants is predicted to substantially contribute to the cosmic-ray positron spectrum, accounting for a significant fraction of the observed positron excess.