Indications exist that mobile phones may cause non-specific biological effects. They are classified as being of implausible non-thermal nature due to low quantum energy and low specific absorption rate levels, even if...Indications exist that mobile phones may cause non-specific biological effects. They are classified as being of implausible non-thermal nature due to low quantum energy and low specific absorption rate levels, even if considering worst cases of "hot spots" of only millimeter size. The considerations of this paper demonstrate that classical theory of polarization offers a conventional interpretation for all three the existence of so far unclarified effects, their low reproducibility and their low intensity. The basis of this explanation is given by the assumption that hot spots contain even hotter “nano spots” on a molecular level according to well known mechanisms of γ-relaxation. In this paper, the concept is put for discussion assuming a heterogeneous system that consists of water molecules as well as larger-sized functional molecules. A consistent interpretation through temperature increase on the level of nanometer sized molecular compounds promises to favor interdisciplinary discussions with respect to safety regulations.展开更多
We present a novel approach for Stimulated Raman Scattering(SRS)spectroscopy in which a hyper spectral resolution and high-speed spectral acquisition are achieved by employing amplified offset-phase controlled fs-puls...We present a novel approach for Stimulated Raman Scattering(SRS)spectroscopy in which a hyper spectral resolution and high-speed spectral acquisition are achieved by employing amplified offset-phase controlled fs-pulse bursts.We investigate the method by solving the coupled non-linear Schrödinger equations and validate it by numerically characterizing SRS in molecular nitrogen as a model compound.The spectral resolution of the method is found to be determined by the inverse product of the number of pulses in the burst and the intraburst pulse separation.The SRS spectrum is obtained through a motion-free scanning of the offset phase that results in a sweep of the Raman-shift frequency.Due to high spectral resolution and fast motion-free scanning the technique is beneficial for a number SRS-based applications such as gas sensing and chemical analysis.展开更多
Ultrafast extreme ultraviolet (XUV) transient absorption spectroscopy measures the time- and frequencydependent light losses after light–matter interactions. In the linear region, the matter response to an XUV light ...Ultrafast extreme ultraviolet (XUV) transient absorption spectroscopy measures the time- and frequencydependent light losses after light–matter interactions. In the linear region, the matter response to an XUV light field is usually determined by the complex refractive index ̃n. The absorption signal is directly related to the imaginary part of ̃n, namely, the absorption index. The real part of ̃n refers to the real refractive index, which describes the chromatic dispersion of an optical material. However, the real refractive index information is usually not available in conventional absorption experiments. Here, we investigate the refractive index line shape in ultrafast XUV transient absorption spectroscopy by using a scheme that the XUV pulse traverses the target gas jet off-center. The jet has a density gradient in the direction perpendicular to the gas injection direction, which induces deflection on the XUV radiation. Our experimental and theoretical results show that the shape of the frequency-dependent XUV deflection spectra reproduces the refractive index line profile. A typical dispersive refractive index line shape is measured for a single-peak absorption;an additional shoulder structure appears for a doublet absorption.Moreover, the refractive index line shape is controlled by introducing a later-arrived near-infrared pulse to modify the phase of the XUV free induction decay, resulting in different XUV deflection spectra. The results promote our understanding of matter-induced absorption and deflection in ultrafast XUV spectroscopy.展开更多
Effective stewardship of data is a critical precursor to making data FAIR.The goal of this paper is to bring an overview of current state of the art of data management and data stewardship planning solutions(DMP).We b...Effective stewardship of data is a critical precursor to making data FAIR.The goal of this paper is to bring an overview of current state of the art of data management and data stewardship planning solutions(DMP).We begin by arguing why data management is an important vehicle supporting adoption and implementation of the FAIR principles,we describe the background,context and historical development,as well as major driving forces,being research initiatives and funders.Then we provide an overview of the current leading DMP tools in the form of a table presenting the key characteristics.Next,we elaborate on emerging common standards for DMPs,especially the topic of machine-actionable DMPs.As sound DMP is not only a precursor of FAIR data stewardship,but also an integral part of it,we discuss its positioning in the emerging FAIR tools ecosystem.Capacity building and training activities are an important ingredient in the whole effort.Although not being the primary goal of this paper,we touch also the topic of research workforce support,as tools can be just as much effective as their users are competent to use them properly.We conclude by discussing the relations of DMP to FAIR principles,as there are other important connections than just being a precursor.展开更多
Polaron defects are ubiquitous in materials and play an important role in many processes involving carrier mobility,charge transfer and surface reactivity.Determining small polarons’spatial distributions is essential...Polaron defects are ubiquitous in materials and play an important role in many processes involving carrier mobility,charge transfer and surface reactivity.Determining small polarons’spatial distributions is essential to understand materials properties and functionalities.However,the required exploration of the configurational space is computationally demanding when using first principles methods.Here,we propose a machine-learning(ML)accelerated search that determines the ground state polaronic configuration.The ML model is trained on databases of polaron configurations generated by density functional theory(DFT)via molecular dynamics or random sampling.To establish a mapping between configurations and their stability,we designed descriptors modelling the interactions among polarons and charged point defects.We used the DFT+ML protocol to explore the polaron configurational space for two surface-systems,reduced rutile TiO_(2)(110)and Nb-doped SrTiO_(3)(001).The ML-aided search proposes additional polaronic configurations and can be utilized to determine optimal polaron distributions at any charge concentration.展开更多
A semigroup (S, .) is called right (left) quasiresiduated if for any a, b in S there exists x in S such that ax≤s b (xa≤s b) with respect to the natural partial order ≤s of S. This concept has its origin in t...A semigroup (S, .) is called right (left) quasiresiduated if for any a, b in S there exists x in S such that ax≤s b (xa≤s b) with respect to the natural partial order ≤s of S. This concept has its origin in the theory of residuated semigroups, but can also be seen as a generalization of the right (left) simplicity of semigroups. It is first studied for totally-, resp., trivially-ordered semigroups, and then for semigroups with idempotents. In particular, the cases when (S≤s) is directed downwards and when S contains a zero (with respect to a more restrictive definition) are dealt with. Throughout, examples are given; in total, 30 classes of (often well-known) semigroups of this kind are specified.展开更多
We demonstrate the generation,spectral broadening and post-compression of second harmonic pulses using a thin beta barium borate(BBO)crystal on a fused-silica substrate as the nonlinear interaction medium.By combining...We demonstrate the generation,spectral broadening and post-compression of second harmonic pulses using a thin beta barium borate(BBO)crystal on a fused-silica substrate as the nonlinear interaction medium.By combining second harmonic generation in the BBO crystal with self-phase modulation in the fused-silica substrate,we efficiently generate millijoule-level broadband violet pulses from a single optical component.The second harmonic spectrum covers a range from long wave ultraviolet(down to 310 nm)to visible(up to 550 nm)with a bandwidth of 65 nm.Subsequently,we compress the second harmonic beam to a duration of 4.8 fs with a pulse energy of 0.64 mJ(5 fs with a pulse energy of 1.05 mJ)using chirped mirrors.The all-solid free-space apparatus is compact,robust and pulse energy scalable,making it highly advantageous for generating intense second harmonic pulses from near-infrared femtosecond lasers in the sub-5 fs regime.展开更多
文摘Indications exist that mobile phones may cause non-specific biological effects. They are classified as being of implausible non-thermal nature due to low quantum energy and low specific absorption rate levels, even if considering worst cases of "hot spots" of only millimeter size. The considerations of this paper demonstrate that classical theory of polarization offers a conventional interpretation for all three the existence of so far unclarified effects, their low reproducibility and their low intensity. The basis of this explanation is given by the assumption that hot spots contain even hotter “nano spots” on a molecular level according to well known mechanisms of γ-relaxation. In this paper, the concept is put for discussion assuming a heterogeneous system that consists of water molecules as well as larger-sized functional molecules. A consistent interpretation through temperature increase on the level of nanometer sized molecular compounds promises to favor interdisciplinary discussions with respect to safety regulations.
基金supported by Austrian Science Fund(FWF)under ZK 9100-N,I 4566 and I 5592Prof.Zheltikov acknowledges the support from the Welch Foundation(Grant A-1801-20210327).
文摘We present a novel approach for Stimulated Raman Scattering(SRS)spectroscopy in which a hyper spectral resolution and high-speed spectral acquisition are achieved by employing amplified offset-phase controlled fs-pulse bursts.We investigate the method by solving the coupled non-linear Schrödinger equations and validate it by numerically characterizing SRS in molecular nitrogen as a model compound.The spectral resolution of the method is found to be determined by the inverse product of the number of pulses in the burst and the intraburst pulse separation.The SRS spectrum is obtained through a motion-free scanning of the offset phase that results in a sweep of the Raman-shift frequency.Due to high spectral resolution and fast motion-free scanning the technique is beneficial for a number SRS-based applications such as gas sensing and chemical analysis.
基金support of the Joint Centre for Extreme Photonics.Funding:This work is supported by the start-up grant of ShanghaiTech University,Double First-Class Initiative Fund of ShanghaiTech University,Shanghai Rising-Star Program(22QA1406200)National Natural Science Foundation of China(12274297,92250303)+7 种基金Shanghai Science and Technology Program(21511105000)NSERC Discovery Grant program(RGPIN-327147-2012)by the U.S.Army Research Office through Award W911NF-14-1-0383Part of this research used Beamline 03U of the Shanghai Synchrotron Radiation Facilitysupported by the ME2 project under contract no.11227902the National Natural Science Foundation of China.Y.F.and C.J.are supported by the National Natural Science Foundation of China(12274230,91950102,and 11834004)Funding of NJUST(TSXK2022D005)H.X.is supported by the National Natural Science Foundation of China(12074063 and 12264003)。
文摘Ultrafast extreme ultraviolet (XUV) transient absorption spectroscopy measures the time- and frequencydependent light losses after light–matter interactions. In the linear region, the matter response to an XUV light field is usually determined by the complex refractive index ̃n. The absorption signal is directly related to the imaginary part of ̃n, namely, the absorption index. The real part of ̃n refers to the real refractive index, which describes the chromatic dispersion of an optical material. However, the real refractive index information is usually not available in conventional absorption experiments. Here, we investigate the refractive index line shape in ultrafast XUV transient absorption spectroscopy by using a scheme that the XUV pulse traverses the target gas jet off-center. The jet has a density gradient in the direction perpendicular to the gas injection direction, which induces deflection on the XUV radiation. Our experimental and theoretical results show that the shape of the frequency-dependent XUV deflection spectra reproduces the refractive index line profile. A typical dispersive refractive index line shape is measured for a single-peak absorption;an additional shoulder structure appears for a doublet absorption.Moreover, the refractive index line shape is controlled by introducing a later-arrived near-infrared pulse to modify the phase of the XUV free induction decay, resulting in different XUV deflection spectra. The results promote our understanding of matter-induced absorption and deflection in ultrafast XUV spectroscopy.
文摘Effective stewardship of data is a critical precursor to making data FAIR.The goal of this paper is to bring an overview of current state of the art of data management and data stewardship planning solutions(DMP).We begin by arguing why data management is an important vehicle supporting adoption and implementation of the FAIR principles,we describe the background,context and historical development,as well as major driving forces,being research initiatives and funders.Then we provide an overview of the current leading DMP tools in the form of a table presenting the key characteristics.Next,we elaborate on emerging common standards for DMPs,especially the topic of machine-actionable DMPs.As sound DMP is not only a precursor of FAIR data stewardship,but also an integral part of it,we discuss its positioning in the emerging FAIR tools ecosystem.Capacity building and training activities are an important ingredient in the whole effort.Although not being the primary goal of this paper,we touch also the topic of research workforce support,as tools can be just as much effective as their users are competent to use them properly.We conclude by discussing the relations of DMP to FAIR principles,as there are other important connections than just being a precursor.
基金This work was supported by the Austrian Science Fund(FWF)project POLOX(Grant No.I 2460-N36),project Super(Grant No.P 32148-N36),the SFB-F81 project TACO.
文摘Polaron defects are ubiquitous in materials and play an important role in many processes involving carrier mobility,charge transfer and surface reactivity.Determining small polarons’spatial distributions is essential to understand materials properties and functionalities.However,the required exploration of the configurational space is computationally demanding when using first principles methods.Here,we propose a machine-learning(ML)accelerated search that determines the ground state polaronic configuration.The ML model is trained on databases of polaron configurations generated by density functional theory(DFT)via molecular dynamics or random sampling.To establish a mapping between configurations and their stability,we designed descriptors modelling the interactions among polarons and charged point defects.We used the DFT+ML protocol to explore the polaron configurational space for two surface-systems,reduced rutile TiO_(2)(110)and Nb-doped SrTiO_(3)(001).The ML-aided search proposes additional polaronic configurations and can be utilized to determine optimal polaron distributions at any charge concentration.
文摘A semigroup (S, .) is called right (left) quasiresiduated if for any a, b in S there exists x in S such that ax≤s b (xa≤s b) with respect to the natural partial order ≤s of S. This concept has its origin in the theory of residuated semigroups, but can also be seen as a generalization of the right (left) simplicity of semigroups. It is first studied for totally-, resp., trivially-ordered semigroups, and then for semigroups with idempotents. In particular, the cases when (S≤s) is directed downwards and when S contains a zero (with respect to a more restrictive definition) are dealt with. Throughout, examples are given; in total, 30 classes of (often well-known) semigroups of this kind are specified.
文摘We demonstrate the generation,spectral broadening and post-compression of second harmonic pulses using a thin beta barium borate(BBO)crystal on a fused-silica substrate as the nonlinear interaction medium.By combining second harmonic generation in the BBO crystal with self-phase modulation in the fused-silica substrate,we efficiently generate millijoule-level broadband violet pulses from a single optical component.The second harmonic spectrum covers a range from long wave ultraviolet(down to 310 nm)to visible(up to 550 nm)with a bandwidth of 65 nm.Subsequently,we compress the second harmonic beam to a duration of 4.8 fs with a pulse energy of 0.64 mJ(5 fs with a pulse energy of 1.05 mJ)using chirped mirrors.The all-solid free-space apparatus is compact,robust and pulse energy scalable,making it highly advantageous for generating intense second harmonic pulses from near-infrared femtosecond lasers in the sub-5 fs regime.