bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic Anisotropy Control with Curie Temperature above 400 K in a van der Waals Ferromagnet for Spintronic Device
Authors: Li Zeya , Tang Ming , Huang Junwei , Qin Feng , Ao Lingyi , Shen Zhiwei , Zhang Caorong , Chen Peng , Bi Xiangyu , Qiu Caiyu , Yu Zhipeng , Zhai Kun , Ideue Toshiya , Wang Lin , Liu Zhongyuan , Tian Yongjun , Iwasa Yoshihiro , Yuan Hongtao
Published: April 2022

The technological appeal of van der Waals ferromagnetic materials is the ability to control magnetism under external fields with desired thickness toward novel spintronic applications. For practically useful devices, ferromagnetism above room temperature or tunable magnetic anisotropy is highly demanded but remains challenging. To date, only a few layered materials exhibit unambiguous ferromagnetic ordering at room temperature via gating techniques or interface engineering. Here, it is demonstrated that the magnetic anisotropy control and dramatic modulation of Curie temperature (Tc) up to 400 K are realized in layered Fe5GeTe2 via the high‐pressure diamond‐anvil‐cell technique. Magnetic phases manifesting with in‐plane anisotropic, out‐of‐plane anisotropic and nearly isotropic magnetic states can be tuned in a controllable way, depicted by the phase diagram with a maximum Tc up to 360 K. Remarkably, the Tc can be gradually enhanced to above 400 K owing to the Fermi surface evolution during a pressure loading–deloading process. Such an observation sheds light on the understanding and control of emergent magnetic states in practical spintronic applications.
Divergent Synthesis of C5‐Heteroatom Substituted Oxazoles
Authors: Oberheide Ansgar , Gaigne Frédéric , Arndt Hans‐Dieter
Published: April 2022

5‐Oxazoyl‐sulfamates have been profiled as versatile building blocks for modifications of oxazoles with various nucleophiles. The unified approach provides a diversification platform to directly access 5‐amino‐oxazoles, 5‐oxazolyl‐sulfides, and 5‐oxazoyl‐aryl ethers from a single precursor.

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Combined Approach of Hypervalent Iodine Reagents and Transition Metals in Organic Reactions
Authors: Rani Neha , Soni Rinku , Sihag Monika , Kinger Mayank , Aneja Deepak K.
Published: April 2022

This review outlines the progress over recent years in the reactions involving combined approach of hypervalent iodine reagents and transition metals such as palladium, nickel, iridium, gold, rhodium, copper, iron, ruthenium, platinum, silver, zinc, rhenium and cobalt. This approach enables organic transformations complimentary to traditional manifolds. Hypervalent iodine reagents play a preeminent role in organic chemistry due to their versatile reactivity, heteroatom ligands and mild reaction conditions. These reagents in combination of transition metal compounds are used in many synthetically useful organic reactions such as oxidation, rearrangement, amination, halogenation, amidation, ring‐opening, cyclization and C−H and C−C functionalization reactions, etc. which are discussed here.

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Mechanical Nanoscale Polarization Control in Ferroelectric PVDF‐TrFE Films
Authors: Roth Robert , Koch Martin M. , Rata A. Diana , Dörr Kathrin
Published: April 2022

Ferroelectric polymer films offer strong advantages like mechanical flexibility, biocompatibility, optical transparency, and low‐cost processing. However, their dielectric or piezoelectric performance is often inferior to that of oxide ferroelectric materials. Key to the dielectric or piezoelectric performance of semicrystalline polymers is the enhancement of electric dipolar order that is naturally lower than in crystalline ferroelectrics. Here, reorientation and alignment of the electric polarization in thin films by the mechanical effect of a scanning unbiased force microscopy tip is demonstrated as a versatile tool for nanoscale domain writing. Thin films (50–150 nm) of PVDF‐TrFE (78:22) on graphite are prepared with dense (110)‐oriented β‐phase lamellae randomly oriented in the film plane. The in‐plane polarization can be poled “mechanically” along any deliberately chosen direction in the film plane after vertical electric poling. Domain patterns with resolution down to ≈50 nm are written with four (out of six possible) local polarization orientations. Written domains show excellent long‐time stability. The surface roughening from the mechanical treatment is moderate (rms roughness of 2–3 nm). A ferroelastic origin of the mechanical polarization switching is discussed. Finally, suggestions are made how to utilize the domain patterns in thin film devices.
A new approach to the inverse scattering and spectral problems for the Sturm‐Liouville equation
Authors: Ramm A.G.
Published: April 2022

New proofs of the known uniqueness theorems for the one‐dimensional inverse spectral and scattering problems are given. Proof of the invertibility of all of the steps in the inversion procedures of Gelfand‐Levitan and Marchenko is given. The proposed method of investigation yields some new results, for example, a Marchenko‐type equation at x = 0 which holds on the whole axis, rather than on a half‐axis, as usual for the scattering theory on half‐axis. It also yields a new method, shorter and simpler than earlier published, for proving that the potential in the class L1,1, obtained by the Marchenko reconstruction procedure, generates the scattering data from which it was reconstructed.
Acoustic and elastic waves in random media – CPA
Authors: Kafesaki M. , Economou E.N.
Published: April 2022

We study the propagation of acoustic and elastic waves in random composites consisting of spherical inclusions in a homogeneous elastic host (fluid or solid), using various extensions of the Coherent Potential Approximation (CPA) method, well‐known from the electronic problem. We calculate the phase velocity, the scattering mean free path and the transport velocity. The results are compared with experimental data and accurate computational results.
Electronic states in topologically disordered systems
Authors: Grimm U. , Römer R.A. , Schliecker G.
Published: April 2022

Networks generated from Voronoi tessellations of space are prototypes for topologically disordered systems. In order to assess the effects of random coordination on the statistical properties of energy spectra, we analyze tight‐binding models for planar topologically disordered systems. To this end, the networks are generated by a simple topological model covering a wide range of naturally observed random structures. We find that the energy‐level‐spacing distributions exhibit level repulsion, similar to the spacings in the energetically disordered Anderson model of localization in the metallic regime.
Wave functions in the Anderson model and in the quantum percolation model: a comparison
Authors: Kantelhardt Jan W. , Bunde Armin
Published: April 2022

We compare numerically the localization behavior of electronic eigenfunctions in the Anderson model and on self‐similar percolation clusters at criticality. We find that the distributions of the local wave function amplitudes |ψ| at fixed distances from the localization center are very similar for both models. The amplitude distributions are well approximated by log‐normal fits, which seem to become exact at large distances. From the distributions, we can calculate analytically the behavior of the averages at sufficiently large distances. We observe two different localization regimes. In the first regime, at intermediate distances from the localization center, we find stretched exponential localization (‘sublocalization’), ln 〈|ψ|〉 ∼ —r, with effective localization exponents dψ < 1. In the second regime, for very large r, the averages strongly depend on the number of configurations N, and superlocalization (dψ > 1) is observed, converging to simple exponential behavior asymptotically as expected. The crossover from the intermediate to the asymptotic regime depends logarithmically on the number of configurations.
Eigenvector correlations in non‐Hermitian random matrix ensembles
Authors: Mehlig B. , Chalker J.T.
Published: April 2022

We analyse correlations of eigenvectors in Ginibre's and Girko's ensembles of Gaussian, non‐Hermitian random N × N matrices J. We study the ensemble average of 〈Lα|Lβ〉 〈Rβ|Rα〉, where 〈Lα| and |Rβ〉 are the left and right eigenvectors of J. The case of Ginibre's ensemble, in which the real and imaginary parts of each element of J are independent random variables, is sufficiently symmetric to allow for an exact solution. In the more general case of Girko's ensemble, we rely on approximations which become exact in the limit of N → ∞.
A numerical study of wave‐function and matrix‐element statistics in the Anderson model of localization
Authors: Uski V. , Mehlig B. , Römer R.A.
Published: April 2022

We have calculated wave functions and matrix elements of the dipole operator in the two‐ and three‐dimensional Anderson model of localization and have studied their statistical properties in the limit of weak disorder. In particular, we have considered two cases. First, we have studied the fluctuations as an external Aharonov‐Bohm flux is varied. Second, we have considered the influence of incipient localization. In both cases, the statistical properties of the eigenfunctions are non‐trivial, in that the joint probability distribution function of eigenvalues and eigenvectors does no longer factorize. We report on detailed comparisons with analytical results, obtained within the non‐linear sigma model and/or the semiclassical approach.
Interplay disorder–interaction in one‐dimensional quantum models
Authors: Pichard Jean‐Louis , Weinmann Dietmar , De Toro Arias Samuel , Jalabert Rodolfo A. , Schmitteckert Peter , Waintal Xavier , Wobst André
Published: April 2022

We show that the crossover from the weak interaction limit towards the strong interaction limit may be accompanied by a delocalization effect in one dimensional disordered quantum models. The spin degrees of freedom are frozen and the spatial wave functions remain symmetric or antisymmetric when the strength U of a short range interaction is varied. The study concerns the excited states for two interacting particles and the ground state for a finite density of carriers.

First, for two particles in a chain of length L, we establish a duality transformation mapping the behavior at weak U onto the behavior at strong U. For intermediate U, the mixing of the one body states and the interaction induced delocalization effect are maximum. Furthermore, if L ≈︂ L1 (the one particle localization length), the system becomes weakly chaotic with critical spectral statistics. This weak chaos is related to the multifractality of the interaction matrix. For two particles starting close to each other, localization is reached in two steps. Before the time t1 necessary to propagate over L1 , U de‐favors the propagation. On the contrary, U favors a very slow delocalization after t1 , characterized by a log(t) spreading of the center of mass. Similarly, the curvatures of the energy levels with respect to an enclosed magnetic flux decrease as a function of U for L < L1 and increase for L > L1 . The changes of the curvatures can be described by a conductance‐like single scaling parameter.

Second, using the density renormalization group algorithm, we have studied the ground state energy of a finite density of spinless fermions and its change under twisted boundary conditions. For a large disorder, a charge reorganization is induced by the interaction: When the system becomes instable between the inhomogeneous configuration driven by the random potential (Anderson insulator) and the homogeneous one driven by repulsive interactions (Mott insulator), the ground state sensitivity can be enhanced by orders of magnitude. In contrast, no enhancement occurs at weaker disorder, when there are many particles on a scale L1.
Lax pair formulation for a small‐polaron chain with integrable boundaries
Authors: Guan Xi‐Wen , Grimm Uwe , Römer Rudolf A.
Published: April 2022

Using a fermionic version of the Lax pair formulation, we construct an integrable small‐polaron model with general open boundary conditions. The Lax pair and the boundary supermatrices K± for the model are obtained. This provides a direct proof of the integrability of the model.
Front propagation in evanescent media
Authors: Büttiker M. , Thomas H.
Published: April 2022

We investigate the time evolution of waves in evanescent media generated by a source within this medium and observed at some distance away from the location of the source. The aim is to find a velocity which describes a causal process and is thus, for a medium with relativistic dispersion, limited by the velocity of light. For a source with a sharp onset in time, the wave function consists of a forerunner generated by the onset of the source, and of a monochromatic front. The forerunner is dominated by a frequency which decreases with time, and the monochromatic front carries the oscillation frequency of the source into the evanescent medium. For a medium with Schrödinger‐like dispersion the velocity of the front is infinite and the monochromatic front propagates with a velocity which is in agreement with the traversal time for tunneling. In the relativistic case the forerunners travel with the velocity of light and the velocity the monochromatic front is smaller than the velocity of light and only for special energies equal to the velocity of light. For sources with a sharp onset, the forerunners are not attenuated and in magnitude far exceed the monochromatic front. This renders the detection of the monochromatic front difficult. To avoid the different behavior of forerunners and monochromatic fronts, sources which are frequency‐band limited can be considered or a short‐time Fourier transform of the field at the observation point can be taken. Both discussions suggest that the traversal time can be determined only up to a factor of 𝒪(1).
Superluminal signal velocity
Authors: Nimtz G.
Published: April 2022

It recently has been demonstrated that signals conveyed by evanescent modes can travel faster than light. In this report some special features of signals are introduced and investigated, for instance the fundamental property that signals are frequency band limited. Evanescent modes are characterized by extraordinary properties: Their energy is negative, they are not directly measurable, and the evanescent region is not causal since the modes traverse this region instantaneously. The study demonstrates the necessity of quantum mechanics in order to understand the superluminal signal velocity of classical evanescent modes.
Electromagnetic simulation of the evanescent mode
Authors: Chen X. , Xiong C.
Published: April 2022

The behaviour of a signal travelling through a piece of evanescent waveguide has been investigated using 3D electromagnetic simulation. The simulation reveals the filtering and resonating features of the evanescent waveguide and explains well most observations in the experiments [1, 2] without using the theory of superluminal signal velocity. However, how to measure and calculate the group velocity on a distorted wave packet remains an open question.
Wave packet tunneling
Authors: Krenzlin H.M. , Budczies J. , Kehr K.W.
Published: April 2022

The tunneling of Gaussian wave packets has been investigated by numerically solving the one‐dimensional Schrödinger equation. The shape of wave packets interacting with a square barrier has been monitored for various values of the barrier width, height and initial width of the wave packet. Compared to the case of free propagation, the maximum of a tunneled wavepacket exhibits a shift, which can be interpreted as an enhanced velocity during tunneling.
Hamiltonian evolution and quantization for extremal black holes
Authors: Kiefer Claus , Louko Jorma
Published: April 2022

We present and contrast two distinct ways of including extremal black holes in a Lorentzian Hamiltonian quantization of spherically symmetric Einstein‐Maxwell theory. First, we formulate the classical Hamiltonian dynamics with boundary conditions appropriate for extremal black holes only. The Hamiltonian contains no surface term at the internal infinity, for reasons related to the vanishing of the extremal hole surface gravity, and quantization yields a vanishing black hole entropy. Second, we give a Hamiltonian quantization that incorporates extremal black holes as a limiting case of nonextremal ones, and examine the classical limit in terms of wave packets. The spreading of the packets, even the ones centered about extremal black holes, is consistent with continuity of the entropy in the extremal limit, and thus with the Bekenstein‐Hawking entropy even for the extremal holes. The discussion takes place throughout within Lorentz‐signature spacetimes.
Atomic interferometry as two‐level particle scattering by a periodic potential
Authors: Bordé Christian J. , Lämmerzahl Claus
Published: April 2022

The beam splitting process of an atomic beam is described by an exactly solvable theory. We use exact plane wave solutions of an atomic two‐level system interacting with laser beams and employ appropriate jump conditions between regions with and without laser beam. The transmission matrix as well as the reflection matrix are given explicitely. Also, the conditions for atom optical analogues of the Borrmann effect and of the pendellösung effect are treated exactly. The high‐energy limit of these phenomena is discussed which is sufficient for many practical purposes.
Nonlinear fluorescence through intermolecular energy transfer and resolution increase in fluorescence microscopy
Authors: Schönle Andreas , Hänninen Pekka E. , Hell Stefan W.
Published: April 2022

We investigate a novel concept to efficiently generate multiphoton induced fluorescence from organic molecules. The concept is based on frustrating the energy transfer between a fluorescent donor and one or more acceptors in conjugated molecules. The nonlinearity is not based on higher order molecular susceptibilities but entirely on their linear properties. Therefore, in contrast to nonresonant multiphoton absorption, this method does not require high local intensities. Likewise, the production of visible fluorescence does not require an infrared excitation wavelength. Hence, when applied to scanning microscopy this property is predicted to increase spatial resolution. Instead of the ∼10 GW/cm2 required in non‐resonant multiphoton excitation, focal intensities ∼10 MW/cm2 are expected to produce an equally strong nonlinear signal. The predicted resolution is up to 30% greater than that of an ideal confocal microscope operating at the same fluorescence wavelength. The resolution improvement over non‐resonant two‐photon absorption microscopes is about two‐fold in all directions.
Potentials in low‐dimensional and semi‐infinite crystals
Authors: Mertins Frank
Published: April 2022

Formulas for potentials in low‐dimensional and semi‐infinite lattices are derived, applying Ewald's method. The lattice sums under consideration describe interactions in different physical situations, e.g. point charges in a unit cell, multipoles or centers of van der Waals potentials, and the exchange interaction of Bloch orbitals. New expressions for general low‐dimensional lattice sums are presented together with earlier results in a unified framework. We take care of the convergency problems using a transparent regularization procedure which leads to a well‐defined solution for the electrostatic potential equation. We consider both point charges and more general Gaussian charge distributions. The latter are relevant for the description of realistic systems. For example, the use of Gaussian distributions makes the formulas useful for the quantum chemical description of polymers (modelled by one‐dimensional grids), stacked systems as graphite (approximated by two‐dimensional grids) and surfaces (modelled by semi‐infinite lattices). The potentials are discussed mainly in the frame‐work of classical electrostatics, but are easily applicable to various quantum chemical problems. We also discuss different physical examples. Since they contain only rapidly converging summations, the new formulas presented here are useful for the computational simulation, e.g. of polymers and multipolar or van der Waals potentials of thin films or surfaces.
Electronic Raman scattering and phonon self‐energy effects in the R‐123 system: Signatures of gap and pseudogap
Authors: Bock Andreas
Published: April 2022

Using Raman spectroscopy and transport measurements we investigate thin epitaxial films of Y1—x(Pr, Ca)xBa2Cu3O6+y. We explore the electronic Raman responses in A1g, B1g, and B2g symmetry obtained after subtraction of phononic excitations, and especially, the 2Δ peaks that form out of the electronic background below Tc. We find that the energy of the B1g 2Δ peak, which is a measure of the gap value, increases monotonically with decreasing doping until the peak becomes unresolvable. In contrast, the peak in A1g symmetry follows Tc being still resolvable in the Pr‐doped films. The B2g response is weak and a 2Δ peak is only detected at the highest doping level. As a consequence of strong electron‐phonon coupling, the B1g phonon at ∼340 cm—1 exhibits a pronounced Fano‐type line shape. We use a phenomenological model to describe the line shape that takes into account real and imaginary part of the electronic response. It allows us to obtain the self‐energy corrections and the mass‐enhancement factor λ as a measure of the coupling. In the normal state we find λ = 0.015 around optimal doping and decreasing values with decreasing doping. The electron‐phonon coupling increases strongly below Tc in overdoped samples in which the B1g 2Δ peaks appear in the vicinity of the phonon. Self‐energy effects observed in the superconducting state can only partly be assigned to the redistributing electronic response. Anomalies with respect to frequency, linewidth, and intensity remain. They appear at increasing temperatures with decreasing doping and we provide evidence that they are connected to the presence of the pseudogap. We supplement our study by a comparison with single crystal data and investigate the influence of site‐substitutional disorder on the electronic response and the electron‐phonon interaction.
Persistent current in normal metals
Authors: Mohanty P.
Published: April 2022

We discuss the recent experiments on persistent current in metallic rings in the backdrop of low temperature decoherence. The observed size of the persistent current, typically on the order of the Thouless energy,e/τD, is much larger than the theoretical results, obtained with or without electron interaction. In considering the phenomenology of both decoherence and persistent current, usually observed in similar systems, we argue towards a dynamic role played by decoherence in the generation of a persistent current. A field‐induced phase shift from near‐equilibrium high‐frequency fluctuations– which otherwise gives rise to decoherence–under certain conditions of periodicity and asymmetry due to disorder, is argued to induce a steady state diffusion current on the order ofe/τD, comparable to the observed persistent current.
Temperature and frequency scaling of the quantum Hall effect
Authors: Meisels R. , Kuchar F. , Dybko K.
Published: April 2022

The conductivity of AlGaAs/GaAs heterostructures in the regime of the quantum Hall effect is studied at DC and up to 55 GHz. The results are compared with predictions of the scaling theory. Deviations are attributed to individual impurities in the vicinity of the two‐dimensional electron system.
Critical spectral statistics as the Luttinger liquid of energy levels at a finite temperature
Authors: Kravtsov V.E.
Published: April 2022

We review the recent results on the energy level statistics in disordered conductors near the Anderson localization transition and other critical systems with multifractal eigenstates. We focus on the critical random matrix ensemble (CRMT) suggested by Mirlin and Fyodorov as a possible generic description of the critical parametric spectral statistics (CPSS). We show that in the region of large energy and/or parameter separations and weak multifractality this CRMT is equivalent to the Luttinger liquid of energy levels at a finite temperature with the interaction between the fictitious 1D fermions (energy levels) being dependent on the Dyson symmetry parameter β = 1, 2, 4 and the temperature being proportional to the multifractality exponent η = 1 — D2. We show that the CRMT is the simplest extension of the classical Wigner‐Dyson random matrix ensemble for the case of finite dimensionless conductance g ≫ 1 and suggest the form of the two‐level correlation functions for all the symmetry classes and all energy separations. We argue that these correlation functions coincide with the density correlation functions for the Calogero‐Sutherland model at finite temperatures.
Conductance distribution of disordered quasi one‐dimensional wires
Authors: Wölfle P. , Muttalib K.A.
Published: April 2022

We determine analytically the distribution of conductances of quasi one‐dimensional disordered electron systems, neglecting electron ‐ electron interaction, for all strengths of disorder. We find that in the crossover region between the metallic and insulating regimes, P(g) is highly asymmetric. The average and the variance of P(g) for 〈g〉 ≫ 1 and 〈g〉 ≪ 1 are shown to agree with exact results.
Addition spectra in disordered quantum dots with strongly interacting electrons
Authors: Canali C.M. , Stephan W.
Published: April 2022

We report on numerical simulations of the electron addition spectra in quantum dots weakly coupled to one charge reservoir, and containing a small number (N ≤ 10) of particles. In particular, we investigate the role played by disorder and electron‐electron interaction in creating a surprising feature, known as “electron bunching”, recently observed experimentally. In dots where disorder and on‐site repulsion are both strong, and the direct Coulomb repulsion is short range, we find examples of two electrons entering the dot at very close values of the gate voltage. Whenever such pairing occurs, the first electron involved in the pair appears at the edge of the quantum dot. Furthermore, the tunneling rate of the second electron is much faster than that of the first. We also find that the total spin of the many‐body ground state is partially polarized after the second electron enters the dot. The dependence of the addition spectrum as a function of the magnetic field is discussed.
Hawking radiation from dilaton gravity in 1 + 1 dimensions: a pedagogical review
Authors: Kummer W. , Vassilevich D.V.
Published: April 2022

Hawking radiation in d = 4 is regarded as a well understood quantum theoretical feature of Black Holes or of other geometric backgrounds with an event horizon. On the other hand, the dilaton theory, emerging after spherical reduction, and generalized dilaton theories only during the last years became the subject of numerous studies which unveiled a surprisingly difficult situation. Recently we have found some solution to the problem of Hawking flux in spherically reduced gravity which has the merit of using a minimal input. It leads to exact cancellation of negative contributions to this radiative flux, encountered in other approaches at infinity, so that our result asymptotically coincides with the one of minimally coupled scalars. The use of an integrated action is avoided — although we have been able to present also that quantity in a closed expression. This short review also summarizes and critically discusses recent activities in this field, including the problem of “conformal frames” for the background and questions which seem to be open in our own approach as well as in others.
Enzyme‐Free Copying of 12 Bases of RNA with Dinucleotides
Authors: Leveau Gabrielle , Pfeffer Daniel , Altaner Bernhard , Kervio Eric , Welsch Franziska , Gerland Ulrich , Richert Clemens
Published: April 2022

The synthesis of complementary strands is the reaction underlying the replication of genetic information. It is likely that the earliest self‐replicating systems used RNA as genetic material. How RNA was copied in the absence of enzymes and what sequences were most likely to have supported replication is not clear. Here we show that mixtures of dinucleotides with C and G as bases copy an RNA sequence of up to 12 nucleotides in dilute aqueous solution. Successful enzyme‐free copying occurred with in situ activation at 4 °C and pH 6.0. Dimers were incorporated in favor of monomers when both competed as reactants, and little misincorporation was detectable in mass spectra. Simulations using experimental rate constants confirmed that mixed C/G sequences are good candidates for successful replication with dimers. Because dimers are intermediates in the synthesis of longer strands, our results support evolutionary scenarios encompassing formation and copying of RNA strands in enzyme‐free fashion.
Bioinspired Design of seco‐Chlorin Photosensitizers to Overcome Phototoxic Effects in Photodynamic Therapy
Authors: Zhu Mengliang , Zhang Hang , Ran Guangliu , Yao Yuhang , Yang Zi‐Shu , Ning Yingying , Yu Yi , Zhang Ruijing , Peng Xin‐Xin , Wu Jiahui , Jiang Zhifan , Zhang Wenkai , Wang Bing‐Wu , Gao Song , Zhang Jun‐Long
Published: April 2022

Photodynamic therapy (PDT) is a non‐invasive treatment modality against a range of cancers and nonmalignant diseases, however one must be aware of the risk of causing phototoxic reactions after treatment. We herein report a bioinspired design of next‐generation photosensitizers (PSs) that not only effectively produce ROS but undergo fast metabolism after treatment to overcome undesirable side effects. We constructed a series of β‐pyrrolic ring‐opening seco‐chlorins, termed beidaphyrin (BP), beidapholactone (BPL), and their zinc(II) derivatives (ZnBP and ZnBPL), featuring intense near‐infrared absorption and effective O2 photosensitization. Irradiation of ZnBPL led to a non‐cytotoxic, metabolizable beidaphodiacetamide (ZnBPD) via in situ generated O2.− but not 1O2, as revealed by mechanistic studies including time‐resolved absorption, kinetics, and isotope labeling. Furthermore, water‐soluble ZnBPL showed an effective therapeutic outcome, fast metabolism, and negligible phototoxic reactions.
Chiral Arene Ligand as Stereocontroller for Asymmetric C−H Activation**
Authors: Liang Hao , Guo Weicong , Li Junxuan , Jiang Jijun , Wang Jun
Published: April 2022

Development of chiral ligands is the most fundamental task in metal‐catalyzed asymmetric synthesis. In the last 60 years, various kinds of ligands have been sophisticatedly developed. However, it remains a long‐standing challenge to develop practically useful chiral η6‐arene ligands, thereby seriously hampering the asymmetric synthesis promoted by arene‐metal catalysts. Herein, we report the design and synthesis of a class of readily tunable, C2‐symmetric chiral arene ligands derived from [2.2]paracyclophane. Its ruthenium(II) complexes have been prepared and successfully applied in the enantioselective C−H activation to afford a series of axially chiral isoquinolones (up to 99 % yield and 96 % ee). This study not only lays chemists’ longstanding doubts about whether it is possible to use chiral arene ligands to stereocontrol ruthenium(II)‐catalyzed asymmetric C−H activation, but also opens up a new avenue to achieve asymmetric C−H activation.
Proteoform‐Selective Imaging of Tissues Using Mass Spectrometry**
Authors: Yang Manxi , Hu Hang , Su Pei , Thomas Paul M. , Camarillo Jeannie M. , Greer Joseph B. , Early Bryan P. , Fellers Ryan T. , Kelleher Neil L. , Laskin Julia
Published: April 2022

Unraveling the complexity of biological systems relies on the development of new approaches for spatially resolved proteoform‐specific analysis of the proteome. Herein, we employ nanospray desorption electrospray ionization mass spectrometry imaging (nano‐DESI MSI) for the proteoform‐selective imaging of biological tissues. Nano‐DESI generates multiply charged protein ions, which is advantageous for their structural characterization using tandem mass spectrometry (MS/MS) directly on the tissue. Proof‐of‐concept experiments demonstrate that nano‐DESI MSI combined with on‐tissue top‐down proteomics is ideally suited for the proteoform‐selective imaging of tissue sections. Using rat brain tissue as a model system, we provide the first evidence of differential proteoform expression in different regions of the brain.
Mapping Active Site Geometry to Activity in Immobilized Frustrated Lewis Pair Catalysts
Authors: Das Shubhajit , Laplaza Ruben , Blaskovits J. Terence , Corminboeuf Clémence
Published: April 2022

The immobilization of molecular catalysts imposes spatial constraints on their active site. We reveal that in bifunctional catalysis such constraints can also be utilized as an appealing handle to boost intrinsic activity through judicious control of the active site geometry. To demonstrate this, we develop a pragmatic approach, based on nonlinear scaling relationships, to map the spatial arrangements of the acid–base components of frustrated Lewis pairs (FLPs) to their performance in the catalytic hydrogenation of CO2. The resulting activity map shows that fixing the donor–acceptor centers at specific distances and locking them into appropriate orientations leads to an unforeseen many‐fold increase in the catalytic activity of FLPs compared to their unconstrained counterparts.
Photoinduced Chemo‐, Site‐ and Stereoselective α‐C(sp3)−H Functionalization of Sulfides
Authors: Tan Zhenda , Zhu Shibo , Liu Yangbin , Feng Xiaoming
Published: April 2022

The ubiquity of sulfur‐containing molecules in biologically active natural products and pharmaceuticals has long attracted synthetic chemists to develop efficient strategies towards their synthesis. The strategy of direct α‐C(sp3)−H modification of sulfides provides a streamlining access to complex sulfur‐containing molecules. Herein, we report a photoinduced chemo‐, site‐ and stereoselective α‐C(sp3)−H functionalization of sulfides using isatins as the photoredox reagent and coupling partner catalyzed by a chiral gallium(III)‐N,N′‐dioxide complex. The reaction proceeds through a verified single‐electron transfer (SET) mechanism with high efficiency, excellent functional group tolerance, as well as a broad substrate scope. Importantly, this cross‐coupling protocol is highly selective for the direct late‐stage functionalization of methionine‐related peptides, regardless of the inherent structural similarity and complexity of diverse residues.
Enantioselective Synthesis of Spiroketals and Spiroaminals via Gold and Iridium Sequential Catalysis
Authors: Yang Wu‐Lin , Shang Xin‐Yu , Luo Xiaoyan , Deng Wei‐Ping
Published: April 2022

The enantioselective cascade reaction between racemic 2‐(1‐hydroxyallyl)phenols and alkynols/alkynamides was realized by using a gold and iridium sequential catalytic system. In this procedure, the in situ generated exocyclic vinyl ethers or enamides undergo the asymmetric allylation/spiroketalization with π‐ally‐Ir amphiphilic species, which provides an efficient and straightforward access to spiroketals and spiroaminals with excellent enantioselectivities. Moreover, racemic 2‐(1‐hydroxyallyl)anilines were also suitable in this reaction along with a kinetic resolution process, affording enantioenriched spiroaminals and 2‐(1‐hydroxyallyl)anilines in good yields. The synthetic utility of this method has been demonstrated by efficient enantioselective synthesis of the analogue of Paecilospirone.
Sulfone‐Decorated Conjugated Organic Polymers Activate Oxygen for Photocatalytic Methane Conversion
Authors: An Bo , Zhang Qin‐hua , Zheng Bo‐shi , Li Miao , Xi Yan‐yan , Jin Xin , Xue Sheng , Li Zhong‐tao , Wu Ming‐bo , Wu Wen‐ting
Published: April 2022

Oxidizing CH4into liquid products with O2under mild conditions still mainly relies on metal catalysis. We prepared a series of sulfone‐modified conjugated organic polymers and found that the catalyst with proper SVIcontent (0.10) could drive O2→H2O2→⋅OH to oxidize CH4into CH3OH and HCOOH directly and efficiently at room temperature under light irradiation. Experimental results showed that after 4 h reaction, decomposition rate and residual amounts of H2O2were 81.21 % and 4.83 mmol gcat−1respectively, and CH4conversion rate was 22.81 %. Mechanism studies revealed that illumination could induce the homolytic dissociation of S=O bonds on catalyst to produce oxygen and sulfur radicals, where the ⋅O could adsorb and activate CH4, and the ⋅S could supply electrons for1O2to generate H2O2and then for decomposing the H2O2into ⋅OH timely to oxidize CH4. This research provided a novel organic catalysis approach for oxygen activation and utilization.
Investigations into spectroscopic and optoelectronic behaviour of furoic acid‐based Eu(III) complexes for advanced photonic applications
Authors: Bedi Manisha , Punia Monika , Taxak Vinod Bala , Khatkar Satyender Pal , Doon Priti Boora
Published: April 2022

To illuminate the zone of organic light‐emitting diodes, a novel series of four red luminescent europium complexes, one binary (C1) and three ternary (C2–C4), of 5‐phenyl 2‐furoic acid was synthesized with 2,2′‐bipyridyl (bipy), bathophenanthroline (batho) and 1,10‐phenanthroline (phen) as ancillary ligands and characterized by adopting various analytical techniques. All the findings of energy‐dispersive X‐ray spectroscopy, elemental (CHN) analysis, Fourier transform infrared, nuclear magnetic resonance, and ultraviolet–visible spectroscopy confirmed the coordination of ligand binding sites with the europium ion. To evaluate the thermal stability, thermogravimetric/difference thermogravimetric measurements were taken that revealed that the synthesized complexes were stable up to 245°C. Diffused reflectance studies indicated that these complexes had potential for their use in wide band‐gap semiconductors, as all the four complexes showed metal‐centred luminescence as a characteristic red emission peak that was observed at 613 nm under the excitation wavelength of 330 nm. The internal quantum efficiencies and luminescence lifetime of complexes were predicted using Judd–Ofelt and photophysical data. The monoexponential luminescence decay and Judd–Ofelt analysis suggested the presence of a single and asymmetric chemical environment in the coordination sphere of the europium metal. Commission International de l'Eclairage colour coordinates, correlated colour temperature values, and colour purity of the complexes validated their red emission in the visible region.
A combined experimental and computational framework to evaluate the behavior of therapeutic cells for peripheral nerve regeneration
Authors: Eleftheriadou Despoina , Berg Maxime , Phillips James B. , Shipley Rebecca J.
Published: April 2022

Recent studies have explored the potential of tissue‐mimetic scaffolds in encouraging nerve regeneration. One of the major determinants of the regenerative success of cellular nerve repair constructs (NRCs) is the local microenvironment, particularly native low oxygen conditions which can affect implanted cell survival and functional performance. In vivo, cells reside in a range of environmental conditions due to the spatial gradients of nutrient concentrations that are established. Here we evaluate in vitro the differences in cellular behavior that such conditions induce, including key biological features such as oxygen metabolism, glucose consumption, cell death, and vascular endothelial growth factor secretion. Experimental measurements are used to devise and parameterize a mathematical model that describes the behavior of the cells. The proposed model effectively describes the interactions between cells and their microenvironment and could in the future be extended, allowing researchers to compare the behavior of different therapeutic cells. Such a combinatorial approach could be used to accelerate the clinical translation of NRCs by identifying which critical design features should be optimized when fabricating engineered nerve repair conduits.
Psychiatric disorders among employment requiring firearms
Authors: Yasuhara Kento , Morreale Kristina , Talley Dijonee , Cooper Danielle T. , Hoy‐Watkins Michelle , Coker Kendell L.
Published: April 2022

Individuals who carry guns as a requirement of employment frequently experience hazards that can be stress inducing, violent, traumatizing, or cause personal injury. This study used data from the Collaborative Psychiatric Epidemiological Surveys (CPES; n = 20,013), to examine mental health diagnoses of individuals that ever worked at a job requiring a firearm. Consistent with existing literature, the findings indicated that those who worked in professions requiring a firearm showed similar risk of mental health diagnoses as law enforcement officers which includes symptoms of trauma, mood disorders, and alcohol use. Further, race/ethnic differences emerged in patterns of mental health diagnoses, suggesting sociocultural differences influence diagnoses. These findings indicate the necessity for further investigation of the understudied area of mental health of those within employment positions that require firearms.
3D bioprinting of an implantable xeno‐free vascularized human skin graft
Authors: Baltazar Tania , Jiang Bo , Moncayo Alejandra , Merola Jonathan , Albanna Mohammad Z. , Saltzman W. Mark , Pober Jordan S.
Published: April 2022

Bioengineered tissues or organs produced using matrix proteins or components derived from xenogeneic sources pose risks of allergic responses, immune rejection, or even autoimmunity. Here, we report successful xeno‐free isolation, expansion, and cryopreservation of human endothelial cells (EC), fibroblasts (FBs), pericytes (PCs), and keratinocytes (KCs). We further demonstrate the bioprinting of a human skin substitute with a dermal layer containing xeno‐free cultured human EC, FBs, and PCs in a xeno‐free bioink containing human collagen type I and fibronectin layered in a biocompatible polyglycolic acid mesh and subsequently seeded with xeno‐free human KCs to form an epidermal layer. Following implantation of such bilayered skin grafts on the dorsum of immunodeficient mice, KCs form a mature stratified epidermis with rete ridge‐like structures. The ECs and PCs form human EC‐lined perfused microvessels within 2 weeks after implantation, preventing graft necrosis, and eliciting further perfusion of the graft by angiogenic host microvessels. As proof‐of‐concept, we generated 12 individual grafts using a single donor of all four cell types. In summary, we describe the fabrication of a bioprinted vascularized bilayered skin substitute under completely xeno‐free culture conditions demonstrating feasibility of a xeno‐free approach to complex tissue engineering.
Bioprinted hASC‐laden collagen/HA constructs with meringue‐like macro/micropores
Authors: Koo YoungWon , Kim Geun Hyung
Published: April 2022

Extrusion‐based bioprinting is one of the most effective methods for fabricating cell‐laden mesh structures. However, insufficient cellular activities within the printed cylindrical cell‐matrix blocks, inducing low cell‐to‐cell interactions due to the disturbance of the matrix hydrogel, remain to be addressed. Hence, various sacrificial materials or void‐forming methods have been used; however, most of them cannot solve the problem completely or require complicated fabricating procedures. Herein, we suggest a bioprinted cell‐laden collagen/hydroxyapatite (HA) construct comprising meringue‐like porous cell‐laden structures to enhance osteogenic activity. A porous bioink is generated using a culinary process, i.e., the whipping method, and the whipping conditions, such as the material concentration, time, and speed, are selected appropriately. The constructs fabricated using the meringue‐like bioink with MG63 cells and human adipose stem cells exhibit outstanding metabolic and osteogenic activities owing to the synergistic effects of the efficient cell‐to‐cell interactions and HA stimulation released from the porous structure. The in vitro cellular responses indicate that the meringue‐like collagen bioink for achieving an extremely porous cell‐laden construct can be a highly promising cell‐laden material for various tissue regeneration applications.
Relationship between the morphology and composition of the lumbar paraspinal and psoas muscles and lumbar intervertebral motion in chronic low‐back pain: An exploratory study
Authors: Seyedhoseinpoor Tahere , Taghipour Mohammad , Dadgoo Mehdi , Ebrahimi Takamjani Ismail , Sanjari Mohammad Ali , Kazemnejad Anoshirvan , M. Elliott James , Hides Julie
Published: April 2022

Muscles of the lumbar spine play an important role in controlling segmental intervertebral motion. This study aimed to evaluate the association between lumbar intervertebral motion and changes in lumbar morphology/composition in people with chronic low‐back pain (CLBP). A sample of 183 patients with CLBP participated in this cross‐sectional study. Participants underwent lumbar flexion‐extension X‐rays to determine vertebral motion (translational and/or rotational motion) of lumbar levels (L1–L2 to L5–S1) and lumbar spine magnetic resonance imaging to quantify total and functional cross‐sectional areas (CSAs) and asymmetry of the multifidus (MF), lumbar erector spinae (LES), and psoas muscles. The relationship between morphology/composition of the muscles and lumbar intervertebral motion was investigated. Smaller total and functional CSAs of the MF and greater CSAs of the LES muscle were observed in participants with greater intervertebral motion. Muscle asymmetry was observed at different lumbar vertebral levels. The greatest amount of translational intervertebral motion was observed at the L3–L4 level, while the greatest amount of rotational translation occurred at the L4–L5. Associations were observed between the morphology of the paraspinal muscles at the vertebral levels adjacent to the L3–L4 level and the increased intervertebral motion at this level. Relationships between measures of muscle morphology/composition and increased segmental vertebral motion were observed. The results may provide a plausible biological reason for the effectiveness of rehabilitating deficient paraspinal muscles in a subset of people with CLBP.
Guide‐Extension Carlino: A novel technique for crossing a microcatheter uncrossable proximal cap during chronic total occlusion interventions
Authors: Karacsonyi Judit , Brilakis Emmanouil S. , Chandwaney Raj H.
Published: April 2022

Balloon and microcatheter uncrossable chronic total occlusions can be challenging to treat. We present a novel technique for treating such lesions through contrast injection via a guide catheter extension wedged against the proximal cap. We named this technique “guide‐extension Carlino.”
Tibial shaft fracture after medial open‐wedge distal tibial tuberosity osteotomy: A case report
Authors: Kuwashima Umito , Itoh Masafumi , Itou Junya , Okazaki Ken
Published: April 2022

We report a case of tibial shaft fracture after open‐wedge distal tibial tuberosity osteotomy (OWDTO). The use of a lag screw for a lateral hinge fracture in OWDTO requires careful postoperative rehabilitation and follow‐up. We discuss concerns related to the mechanical strength at the osteotomy site after OWDTO to prevent fracture.