bluuebunny/crossref_metadata_2025 huggingface dataset:
Matter waves in terms of the unitary representations of the Lorentz group
Authors: Frick R.A.
Published: June 2022

In a generalized Heisenberg/Schrödinger picture, the unitary representations of the Lorentz group may, for a massive relativistic particle, be used to attribute to waves an extra wavelength that is longer than the de Broglie wavelength. Propagators are defined as spacetime transitions between states with different eigenvalues of the first or the second Casimir operator of the Lorentz algebra.
Prediction of spinodal wavelength in continuously cooled metallic liquid
Authors: Borchers C. , Schroers J. , Busch R.
Published: June 2022

The spinodal decomposition of a deeply undercooled metallic liquid Zr41.2 Ti13.8Cu12.5Ni10Be22.5 between 800 and 700 K is analysed in the framework of the theory of Cahn and Hilliard for continuous cooling, and the wavelength with maximum amplification is predicted, using as input parameters thermodynamic values gained in experiments. Electron microscopical studies show the microstructure of glass forming alloys Zr41.2Ti13.8Cu12.5Ni10Be22.5. The as‐cast material exhibits a two phase mixture of amorphous regions with different compositions. Evidence for spinodal decomposition is given, and the computed maximum‐amplitude wavelength corresponds well with the one found in the experiments.
Thermoballistic spin‐polarized electron transport in paramagnetic semiconductors
Authors: Lipperheide R. , Wille U.
Published: June 2022

Spin‐polarized electron transport in diluted magnetic semiconductors (DMS) in the paramagnetic phase is described within the thermoballistic transport model. In this (semiclassical) model, the ballistic and diffusive transport mechanisms are unified in terms of a thermoballistic current in which electrons move ballistically across intervals enclosed between arbitrarily distributed points of local thermal equilibrium. The contribution of each interval to the current is governed by the momentum relaxation length. Spin relaxation is assumed to take place during the ballistic electron motion. In paramagnetic DMS exposed to an external magnetic field, the conduction band is spin‐split due to the giant Zeeman effect. In order to deal with this situation, we extend our previous formulation of thermoballistic spin‐polarized transport so as to take into account an arbitrary (position‐dependent) spin splitting of the conduction band. The current and density spin polarizations as well as the magnetoresistance are each obtained as the sum of an equilibrium term determined by the spin‐relaxed chemical potential, and an off‐equilibrium contribution expressed in terms of a spin transport function that is related to the splitting of the spin‐resolved chemical potentials. The procedures for the calculation of the spin‐relaxed chemical potential and of the spin transport function are outlined. As an illustrative example, we apply the thermoballistic description to spin‐polarized transport in DMS/NMS/DMS heterostructures formed of a nonmagnetic semiconducting sample (NMS) sandwiched between two DMS layers. We evaluate the current spin polarization and the magnetoresistance for this case and, in the limit of small momentum relaxation length, find our results to agree with those of the standard drift‐diffusion approach to electron transport.
On the crystalline states of the dilute jellium model
Authors: Ciccariello S.
Published: June 2022

Strongly localized quantum crystalline states (SLQCS) are determinantal wave‐functions made up of the single‐particle wave‐functions that are obtained from all the distinct crystalline translations of a particular wave‐function different from zero only within a primitive cell of the considered crystal and dependent on some parameters α1, … , αn. The expectation value of the Hamiltonian of the jellium model is numerically evaluated over a class of SLQCS depending on a single parameter α. The minimization of this value with respect to α yields an energy smaller than that of the polarized jellium fluid. The results, compared with the more accurate results obtained by Hartree‐Fock and quantum Monte‐Carlo procedures, further clarify the importance of the electron localization for the transition to a crystalline phase as well as the localization increase with decreasing density.
Evaluation of the scientific impact, productivity and biological age based upon the h‐index in three Latin American countries: the materials science case
Authors: Romero A.H. , García A. , Kiwi M.
Published: June 2022

We discuss the scientific impact of Latin American scientists in the field of materials science. The analysis is based on the h‐index as the scientometric index used to quantify the scientific productivity of an individual. In particular, we focus our analysis in México, Chile and Colombia. We compare the level of productivity between all these countries. We also analyzed the h‐index as function of the biological age, by using the first year of publication of a given scientists as a reference and discussed the general distribution of its quantification. We do not find a clear relationship between these two quantities. Based in our results we propose some political measures that these countries could implement to improve productivity as well as scientific development in this field.
Thermal photon dispersion law and modified black‐body spectra
Authors: Ludescher J. , Hofmann R.
Published: June 2022

Based on the postulate that photon propagation is governed by an SU(2) gauge principle we numerically compute the one‐loop dispersion for thermalized photon propagation on the radiatively induced mass shell. Formerly, the dispersion was addressed by assuming p2 = 0. While this approximation turns out to be excellent for temperatures ≤ 2 TCMB the exact result exhibits a much faster (power‐like) shrinking of the gap in the black‐body spectral intensity with rising temperature. Our previous statements on anomalous large‐angle CMB temperature‐temperature correlations, obtained in the approximation p2 = 0, remain valid.
Mixtures of correlated bosons and fermions: Dynamical mean‐field theory for normal and condensed phases
Authors: Byczuk K. , Vollhardt D.
Published: June 2022

We derive a dynamical mean‐field theory for mixtures of interacting bosons and fermions on a lattice (BF‐DMFT). The BF‐DMFT is a comprehensive, thermodynamically consistent framework for the theoretical investigation of Bose‐Fermi mixtures and is applicable for arbitrary values of the coupling parameters and temperatures. It becomes exact in the limit of high spatial dimensions d or coordination number Z of the lattice. In particular, the BF‐DMFT treats normal and condensed bosons on equal footing and thus includes the effects caused by their dynamic coupling. Using the BF‐DMFT we investigate two different interaction models of correlated lattice bosons and fermions, one where all particles are spinless (model I) and one where fermions carry a spin one‐half (model II). In model I the local, repulsive interaction between bosons and fermions can give rise to an attractive effective interaction between the bosons. In model II it can also lead to an attraction between the fermions.
On the variational formulation of systems with non‐holonomic constraints
Authors: Delphenich D.H.
Published: June 2022

In a previous article by the author, it was shown that one could effectively give a variational formulation to non‐conservative mechanical systems by starting with the first variation functional instead of an action functional. In this article, it is shown that this same approach will also allow one to give a variational formulation to systems with non‐holonomic constraints. The key is to use an adapted anholonomic local frame field in the formulation, which then implies the replacement of ordinary derivatives with covariant ones. The method is then applied to the case of a vertical disc rolling without slipping or friction on a plane.
Approximate analytical solutions of the pseudospin symmetric Dirac equation for exponential‐type potentials
Authors: Arda A. , Sever R. , Tezcan C.
Published: June 2022

The solvability of The Dirac equation is studied for the exponential‐type potentials with the pseudospin symmetry by using the parametric generalization of the Nikiforov–Uvarov method. The energy eigenvalue equation, and the corresponding Dirac spinors for Morse, Hulthen, and q‐deformed Rosen–Morse potentials are obtained within the framework of an approximation to the spin‐orbit coupling term, so the solutions are given for any value of the spin‐orbit quantum number κ = 0, or κ ≠ 0.
Network modules help the identification of key transport routes, signaling pathways in cellular and other networks
Authors: Palotai R. , Csermely P.
Published: June 2022

Complex systems are successfully reduced to interacting elements via the network concept. Transport plays a key role in the survival of networks – for example the specialized signaling cascades of cellular networks filter noise and efficiently adapt the network structure to new stimuli. However, our general understanding of transport mechanisms and signaling pathways in complex systems is yet limited. Here we summarize the key network structures involved in transport, list the solutions available to overloaded systems for relaxing their load and outline a possible method for the computational determination of signaling pathways. We highlight that in addition to hubs, bridges and the network skeleton, the overlapping modular structure is also essential in network transport. Path‐lenghts in the module‐space of the yeast protein‐protein interaction network indicated that module‐based paths may cross fewer modular boundaries than shortest paths. Moreover, by locating network elements in the space of overlapping network modules and evaluating their distance in this ‘module space’, it may be possible to approximate signaling pathways computationally, which, in turn could serve the identification of signaling pathways of complex systems. Our model may be applicable in a wide range of fields including traffic control or drug design.
Purely electronic transport and localization in the Bose glass
Authors: Müller M.
Published: June 2022

We discuss transport and localization properties on the insulating side of the disorder dominated superconductor‐insulator transition, described in terms of the dirty boson model. Analyzing the spectral properties of the interacting bosons in the absence of phonons, we argue that the Bose glass phase admits three distinct regimes. For strongest disorder the boson system is a fully localized, perfect insulator at any temperature. At smaller disorder, only the low temperature phase exhibits perfect insulation while delocalization takes place above a finite temperature. We argue that a third phase must intervene between these perfect insulators and the superconductor. This conducting Bose glass phase is characterized by a mobility edge in the many body spectrum, located at finite energy above the ground state. In this insulating regime purely electronically activated transport occurs, with a conductivity following an Arrhenius law at asymptotically low temperatures, while a tendency to superactivation is predicted at higher T. These predictions are in good agreement with recent transport experiments in highly disordered films of superconducting materials.
Optically driven Mott‐Hubbard systems out of thermodynamic equilibrium
Authors: Lubatsch A. , Kroha J.
Published: June 2022

We consider the Hubbard model at half filling, driven by an external, stationary laser field. This stationary, but periodic in time, electromagnetic field couples to the charge current, i.e. it induces an extra contribution to the hopping amplitude in the Hubbard Hamiltonian (photo‐induced hopping). We generalize the dynamical mean‐field theory (DMFT) for nonequilibrium with periodic‐in‐time external fields, using a Floquet mode representation and the Keldysh formalism. We calculate the non‐equilibrium electron distribution function, the density of states and the optical DC conductivity in the presence of the external laser field for laser frequencies above and below the Mott‐Hubbard gap. The results demonstrate that the system exhibits an insulator‐metal transition as the frequency of the external field is increased and exceeds the Mott‐Hubbard gap. This corresponds to photo‐induced excitations into the upper Hubbard band.
Non‐linear conductivity in Coulomb glasses
Authors: Caravaca M. , Voje A. , Bergli J. , Ortuño M. , Somoza A.M.
Published: June 2022

We have studied the nonlinear conductivity of two‐dimensional Coulomb glasses. We have used a Monte Carlo algorithm to simulate the dynamic of the system under an applied electric field E. We have compared results for two different models: a regular square lattice with only diagonal disorder and a random array of sites with diagonal and off‐diagonal disorder. We have found that for moderate fields the logarithm of the conductivity is proportional to

reproducing experimental results. We have also found that in the nonlinear regime the site occupancy in the Coulomb gap follows a Fermi‐Dirac distribution with an effective temperature Teff higher than the phonon bath temperature T.
Light transport and correlation length in a random laser
Authors: Frank R. , Lubatsch A. , Kroha J.
Published: June 2022

A random laser is a strongly disordered, laser‐active optical medium. The coherent laser feedback, which has been demonstrated experimentally to be present in these systems beyond doubt, requires the existence of spatially localized photonic quasimodes. However, the origin of these quasimodes has remained controversial. We develop an analytical theory for diffusive random lasers by coupling the transport theory of the disordered medium to the semiclassical laser rate equations, accounting for (coherent) stimulated and (incoherent) spontaneous emission. From the causality of wave propagation in an amplifying, diffusive medium we derive a novel length scale which we identify with the average mode radius of the lasing quasi‐modes. We show that truly localized modes do not exist in the system without photon number conservation. However, we find that causality in the amplifying medium implies the existence of a novel, finite intensity correlation length which we identify with the average mode volume of the lasing quasimodes. We show further that the surface of the laser‐active medium is crucial in order to stabilize a stationary lasing state. We solve the laser transport theory with appropriate surface boundary conditions to obtain the spatial distributions of the light intensity and of the occupation inversion. The dependence of the intensity correlation length on the pump rate agrees with experimental findings.
Conductance distribution at criticality: one‐dimensional Anderson model with random long‐range hopping
Authors: Méndez A. , Gopar V. , Varga I.
Published: June 2022

We study numerically the conductance distribution function w(T) for the one‐dimensional Anderson model with random long‐range hopping described by the Power‐law Banded Random Matrix model at criticality. We concentrate on the case of two single‐channel leads attached to the system. We observe a smooth transition from localized to delocalized behavior in the conductance distribution by increasing b, the effective bandwidth of the model. Also, for b < 1 we show that w(ln T/Ttyp) is scale invariant, where Ttyp = exp 〈 ln T 〉 is the typical value of T. Moreover, we find that for T < Ttyp, w(ln T/Ttyp) shows a universal behavior proportional to (T/Ttyp)‐1/2.
Broken time‐reversal symmetry scattering at the Anderson transition
Authors: Alcazar A. , Méndez A. , Varga I.
Published: June 2022

We study numerically the statistical properties of some scattering quantities for the Power‐law Banded Random Matrix model at criticality in the absence of time‐reversal symmetry, with a small number of single‐channel leads attached to it. We focus on the average scattering matrix elements, the conductance probability distribution, and the shot noise power as a function of the effective bandwidth b of the model. We find a smooth transition from insulating‐ to metallic‐like behavior in the scattering properties of the model by increasing b. We contrast our results with existing random matrix theory predictions.
Organic glasses: cluster structure of the random energy landscape
Authors: Novikov S.V.
Published: June 2022

An appropriate model for the random energy landscape in organic glasses is a spatially correlated Gaussian field. We calculated the distribution of the average value of a Gaussian random field in a finite domain. The results of the calculation demonstrate a strong dependence of the width of the distribution on the spatial correlations of the field. Comparison with the simulation results for the distribution of the size of the cluster indicates that the distribution of an average field could serve as a useful tool for the estimation of the asymptotic behavior of the distribution of the size of the clusters for “deep” clusters where value of the field on each site is much greater than the rms disorder. We also demonstrate significant modification of the properties of energetic disorder in organic glasses at the vicinity of the electrode.
Normal frames for general connections
Authors: Nester J.M.
Published: June 2022

At any point on a manifold certain normal frames that are well adapted to general connections are identified. For manifolds with metrics the series expansion terms for the metric/frame (second order) and the connection (first order) are specified. Some special cases as well as mathematical and physical applications are noted.
A noncommutative Friedman cosmological model
Authors: Heller M.
Published: June 2022

The closed Friedman cosmological model, based on noncommutative geometry, is presented. Two global effects exhibited by the model are discussed. The first effect is the “generation of matter out of geometry”. Gravitational field equation in this model has the form of the eigenvalue equation for the Einstein operator. It turns out that the eigenvalues of this operator reproduce components of the energy‐momentum tensor. The second effect concerns the existence of the initial and final singularities. Because of the strongly probabilistic character of the noncommutative dynamics on the fundamental level, although singularities do exist, they are probabilistically irrelevant.
Can singularities be avoided in quantum cosmology?
Authors: Kiefer C.
Published: June 2022

Many cosmological models based on general relativity contain singularities. In this contribution I address the question whether consistent models without singularities can exist in quantum cosmology. The discussion is based on the Wheeler–DeWitt equation of quantum geometrodynamics. The models under consideration are motivated by recent discussions of dark energy. Employing some natural criteria of singularity avoidance in the quantum theory, I show that this can indeed happen in these models.
Testing dark energy with supernovae
Authors: Kowalski M.
Published: June 2022

The use of Type Ia Supernovae as cosmic standard candles pose still perhaps the most direct way to probe the Cosmic acceleration history. In this contribution we will review the present status of Supernova cosmology. We will focus on current observations and what they can tell us about the properties of Dark Energy, i.e. our (in‐)ability to distinguish dark energy models from cosmological constant. In the last part we will give a brief outlook at what to expect from future surveys.
Metric‐affine f(R)‐gravity with torsion: an overview
Authors: Capozziello S. , Vignolo S.
Published: June 2022

Torsion and curvature could play a fundamental role in explaining cosmological dynamics. f(R)‐gravity with torsion is an approach aimed to encompass in a comprehensive scheme all the Dark Side of the Universe (Dark Energy and Dark Matter). We discuss the field equations in empty space and in presence of perfect fluid matter taking into account the analogy with the metric‐affine formalism. The result is that the extra curvature and torsion degrees of freedom can be dealt under the standard of an effective scalar field of fully geometric origin. The initial value problem for such theories is also discussed.
Superenergy, conformal transformations, and Friedman universes
Authors: Garecki J.
Published: June 2022

In this paper we present the components of the canonical superenergy tensors for a dust flat Friedman universe. In order to simplify these calculations we have used the tranformational properties of the superenergy tensors under conformal change of the spacetime metric.
On the energy conditions in non‐compact Kaluza‐Klein gravity
Authors: Rasouli S.M.M. , Jalalzadeh S.
Published: June 2022

We investigate a few cosmological solutions in non‐compact five‐dimensional space‐time which is both Ricci‐flat and conformally flat. We then study the reduced solutions on the brane in detail by applying the four energy conditions, which categorize our model in some classes. These classes of solutions can describe the universe including accelerating expansion with either abnormal matter (when matter specifically violates the strong energy condition, it is called abnormal) or a phantom model of dark energy and a Stephani universe which is dominated by abnormal matter describing vacuum energy.
On the initial condition in quantum cosmology
Authors: Pedram P.
Published: June 2022

We outline the applications of a new initial condition for the Wheeler‐DeWitt equation in various quantum cosmology models. These models consist of minimally coupled scalar field in Friedmann‐Robertson‐Walker and Stephani spacetimes, varying speed of light theories and conformally coupled scalar field in Friedmann‐Robertson‐Walker spacetime. This initial condition results in wave packets with complete classical and quantum correspondence. This means that the wave packets closely follow the classical trajectories and strongly peak on them. We show that these models, similar to their classical counterparts, contain singularities even at the quantum level.
Bianchi I model of the universe in terms of nonstandard LQC
Authors: Dzierżak P. , Piechocki W.
Published: June 2022

We apply the loop geometry underlying loop quantum cosmology to examine the cosmological singularity of the Bianchi I model. Modification of classical theory by holonomy around a loop turns a big‐bang into a big‐bounce already at the classical level. Our model has a free parameter to be determined by cosmic data.
Generalization of Hajicek and Kuchař's canonical quantization scheme to the 3+1 geometries admitting maximally symmetric two‐dimensional surfaces
Authors: Melas E.
Published: June 2022

The 3+1 (canonical) decomposition of all geometries admitting two‐dimensional space‐like surfaces is exhibited. A proposal consisting of a specific re‐normalization Assumption and an accompanying Requirement is put forward, which enables the canonical quantization of these geometries. The resulting Wheeler–deWitt equation is based on a re‐normalized manifold parameterized by three smooth scalar functionals and the entire space of solutions to this equation is analytically given.
Propagation of extended objects across singularity of time dependent orbifold
Authors: Małkiewicz P.
Published: June 2022

In this paper we argue that the compactified Milne space is a promising model of the cosmological singularity. It is shown that extended objects like strings propagate in a well‐defined manner across the singularity of the embedding space. Then a proposal for quantization of extended objects in the case of a membrane is given.
Presently decaying dark energy?
Authors: Shafieloo A. , Sahni V. , Starobinsky A.A.
Published: June 2022

Investigation of dark energy (DE) properties using the largest existing Constitution supernovae sample including recent CfA data for small redshifts and omitting the assumption of a constant equation of state w for DE reveals a slight inconsistency (more than 1σ) with the standard spatially flat LCDM model. The effect which is most clearly seen using the recently introduced Om diagnostic corresponds to an increase of both this diagnostic and w at redshifts z <∼ 0.3. Interestingly, such DE behaviour produces a better fit to baryon acoustic oscillation data too. Including the cosmic microwave background shift parameter as another independent observation, we have shown that the well known CPL parametrization is not suitable to fit the data at low and high redshifts simultaneously because of this non‐trivial DE behaviour implied by them. If not systematic, this effect would correspond to DE decaying into dark matter or something else presently, and we have found good consistency of a toy model for this process with the data.
Three steps to accelerated expansion
Authors: Hrycyna O. , Szydłowski M.
Published: June 2022

We study the dynamics of a non‐minimally coupled scalar field cosmology with a potential function. We use the framework of dynamical systems theory to investigate all evolutional paths admissible for all initial conditions. Additionally, we assume the presence of barotropic matter and show that the dynamics can be formulated in terms of an autonomous dynamical system. We have found fixed points corresponding to three main stages of the evolution of the universe, namely, radiation, matter and quintessence domination epochs. Using the linearization of the dynamical systems in the vicinity of the critical points we explicitly obtain formulas determining the effective equation of state parameter for the universe at different epochs. In our approach the form of w(z) parametrisation is derived directly from the dynamical equations rather than postulated a priori.
Weak lensing forecasts for dark energy, neutrinos and initial conditions
Authors: Debono I. , Rassat A. , Réfrégier A. , Amara A. , Kitching T.D.
Published: June 2022

Weak gravitational lensing provides a sensitive probe of cosmological parameters by measuring the mass distribution and the geometry of the low redshift universe. We show how an all‐sky weak lensing tomographic survey can jointly constrain different sets of cosmological parameters describing dark energy, massive neutrinos, and the primordial power spectrum. Using the Fisher matrix formalism with and without CMB priors, we examine how the constraints vary as the parameter set is enlarged. We find that weak lensing with CMB priors provides robust constraints on dark energy parameters and can simultaneously provide strong constraints on all three parameter sets. We also find that the dark energy sector is largely insensitive to the inclusion of the other cosmological sectors.
Statistical anisotropy as a consequence of inflation
Authors: Shtanov Y.
Published: June 2022

Cosmological inflation remains to be a unique mechanism of generation of plausible initial conditions in the early universe. In particular, it generates the primordial quasiclassical perturbations with power spectrum determined by the fundamental principles of quantum field theory. In this work, we pay attention to the fact that the quasiclassical perturbations permanently generated at early stages of inflation break homogeneity and isotropy of the cosmological background. The evolution of the small‐scale quantum vacuum modes on this inhomogeneous background results in statistical anisotropy of the primordial power spectrum, which can manifest itself in the observable large‐scale structure and cosmic microwave background. The effect is predicted to have almost scale‐invariant form dominated by a quadrupole and may serve as a non‐trivial test of the inflationary scenario. Theoretical expectation of the magnitude of this statistical anisotropy depends on the assumptions about the physics in the trans‐Planckian region of wavenumbers.
PPN limit and cosmological gravitational waves as tools to constrain f(R)‐gravity
Authors: De Laurentis M. , Capozziello S. , Nojiri S. , Odintsov S.D.
Published: June 2022

We discuss the PPN Solar‐System constraints and the GW stochastic background considering some recently proposed f(R) gravity models which satisfy both cosmological and stability conditions. Using the definition of PPN‐parameters γand β in terms of f(R)‐models and the definition of scalar GWs, we compare and discuss if it is possible to search for parameter ranges of f(R)‐models working at Solar System and GW stochastic background scale.
Galactic halos in cosmology with long‐range scalar DM interaction
Authors: Hellwing W.A.
Published: June 2022

Based on a set of cosmological N‐body simulations we analyze properties of the dark matter (DM) haloes in a galaxy mass range (1011–1013 h‐1Modot) in modified ΛCDM cosmology with additional dynamically screened scalar interactions in DM sector. Our simulations show that scalar interactions support picture of the Island Universe. Rapid structure formation processes are shifted into higher redshifts resulting in a much smaller accretion and merging rates for galactic haloes at low redshifts. Finally, we present how this “fifth” force affects halo properties, like density profile, triaxiality, ellipticities and the spin parameter.
Convergent Synthesis and Anti‐Pancreatic Cancer Cell Growth Activity of a Highly Branched Heptadecasaccharide from Carthamus tinctorius
Authors: Hu Chaoyu , Wu Shengjie , He Fei , Cai Deqin , Xu Zhuojia , Ma Wenjing , Liu Yating , Wei Bangguo , Li Tiehai , Ding Kan
Published: June 2022

Bioactive polysaccharides from natural resources target various biological processes and are increasingly used as potential target molecules for drug development. However, the accessibility of branched and long complex polysaccharide active domains with well‐defined structures remains a major challenge. Herein we describe an efficient first total synthesis of a highly branched heptadecasaccharide moiety of the native bioactive galectin‐3‐targeting polysaccharide from Carthamus tinctorius L. as well as shorter fragments of the heptadecasaccharide. The key feature of the approach is that a photo‐assisted convergent [6+4+7] one‐pot coupling strategy enables rapid assembly of the heptadecasaccharide, whereby a photoremovable o‐nitrobenzyl protecting group is used to generate the corresponding acceptor for glycosylation in situ upon ultraviolet radiation. Biological activity tests suggest that the heptadecasaccharide can target galectin‐3 and inhibit pancreatic cancer cell growth.
Synthetic Reprogramming of Kinases Expands Cellular Activities of Proteins
Authors: Shoba Veronika M. , Munkanatta Godage Dhanushka N. P. , Chaudhary Santosh K. , Deb Arghya , Siriwardena Sachini U. , Choudhary Amit
Published: June 2022

Phosphorylation‐inducing chimeric small molecules (PHICS) can enable a kinase to act at a new cellular location or phosphorylate non‐native substrates (neo‐substrates)/ sites (neo‐phosphorylations).[1, 2] We report a modular design and high‐yielding synthesis of such PHICS that endowed multiple new activities to protein kinase C (PKC). For example, while PKC is unable to downregulate the activity of a gain‐of‐function variant (S180A) of Bruton's tyrosine kinase that evokes B cell malignancy phenotype, PHICS enabled PKC to induce inhibitory neo‐phosphorylations on this variant. Furthermore, while PKC typically phosphorylates its membrane‐associated substrates, PKC with PHICS phosphorylated multiple cytosol‐based neo‐substrates (e.g., BCR‐ABL). Finally, a PHICS for BCR‐ABL induced death of chronic myeloid leukemia cell lines. These studies show the power of synthetic chemistry to expand the chemical and functional diversity of proteins in cells using bifunctional molecules.
Restoration of the Immunogenicity of Tumor Cells for Enhanced Cancer Therapy via Nanoparticle‐Mediated Copper Chaperone Inhibition
Authors: Ding Feixiang , Li Fei , Tang Dongsheng , Wang Bin , Liu Junyan , Mao Xiaoyuan , Yin Jiye , Xiao Haihua , Wang Jing , Liu Zhaoqian
Published: June 2022

Recent progress in studying copper‐dependent targets and pathways in the context of tumor treatment has provided new insights into therapeutic strategies of leveraging copper‐dependent disease vulnerabilities and pharmacological manipulation of intratumor copper transportation to improve chemotherapy. Here, we developed reactive oxygen species (ROS)‐sensitive nanoparticles loaded with copper chaperone inhibitor DC_AC50 and cisplatin(IV) prodrug. The released DC_AC50 can promote a remarkable accumulation of intracellular cisplatin and copper through inhibition of the Atox1‐ATPase pathways, thereby enhancing the chemotherapeutic effect of cisplatin and inducing significant ROS generation. Excessive ROS then elicits intense endoplasmic reticulin (ER) stress which facilitates the immunogenic cell death (ICD) spurring a sustained immune response. Our study suggests that nanoparticle‐mediated copper chaperone inhibition via DC_AC50 can restore the immunogenicity of tumor cells for enhanced chemotherapy and cancer immunotherapy.
Highly Robust CuI‐TADF Emitters for Vacuum‐Deposited OLEDs with Luminance up to 222 200 cd m−2 and Device Lifetimes (LT90) up to 1300 hours at an Initial Luminance of 1000 cd m−2
Authors: Tang Rui , Xu Shuo , Lam Tsz‐Lung , Cheng Gang , Du Lili , Wan Qingyun , Yang Jun , Hung Faan‐Fung , Low Kam‐Hung , Phillips David Lee , Che Chi‐Ming
Published: June 2022

A critical step in advancing the practical application of copper‐based organic light‐emitting diodes (OLEDs) is to bridge the large gap between device efficiency and operational stability at practical luminance. Described is a panel of air‐ and thermally stable two‐coordinate CuI emitters featuring bulky pyrazine‐ (PzIPr) or pyridine‐fused N‐heterocyclic carbene (PyIPr*) and carbazole (Cz) ligands with enhanced amide‐Cu‐carbene bonding interactions. These CuI emitters display thermally activated delayed fluorescence (TADF) from the 1LL′CT(Cz→PzIPr/PyIPr*) excited states across the blue to red regions with exceptional radiative rate constants of 1.1–2.2×106 s−1. Vapour‐deposited OLEDs based on these CuI emitters showed excellent external quantum efficiencies and luminance up to 23.6 % and 222 200 cd m−2, respectively, alongside record device lifetimes (LT90) up to 1300 h at 1000 cd m−2 under our laboratory conditions, highlighting the practicality of the CuI‐TADF emitters.
Exploration of potential inhibitors for SARS‐CoV‐2 Mpro considering its mutants via structure‐based drug design, molecular docking, MD simulations, MM/PBSA, and DFT calculations
Authors: Ghasemlou Abdulrahman , Uskoković Vuk , Sefidbakht Yahya
Published: June 2022

The main protease (Mpro) of SARS‐COV‐2 plays a vital role in the viral life cycle and pathogenicity. Due to its specific attributes, this 3‐chymotrypsin like protease can be a reliable target for the drug design to combat COVID‐19. Since the advent of COVID‐19, Mpro has undergone many mutations. Here, the impact of 10 mutations based on their frequency and five more based on their proximity to the active site was investigated. For comparison purposes, the docking process was also performed against the Mpros of SARS‐COV and MERS‐COV. Four inhibitors with the highest docking score (11b, α‐ketoamide 13b, Nelfinavir, and PF‐07321332) were selected for the structure‐based ligand design via fragment replacement, and around 2000 new compounds were thus obtained. After the screening of these new compounds, the pharmacokinetic properties of the best ones were predicted. In the last step, comparative molecular dynamics (MD) simulations, molecular mechanics Poisson–Boltzmann surface area calculations (MM/PBSA), and density functional theory calculations were performed. Among the 2000 newly designed compounds, three of them (NE1, NE2, and NE3), which were obtained by modifications of Nelfinavir, showed the highest affinity against all the Mpro targets. Together, NE1 compound is the best candidate for follow‐up Mpro inhibition and drug development studies.
Thermoluminescence characteristics of calcite with a Gaussian process regression model of machine learning
Authors: Isik Esme
Published: June 2022

Thermoluminescence (TL) is defined as a luminescence phenomenon that can be detected when an insulator or semiconductor is thermally stimulated. Defective crystals store radiation until they are stimulated. Thermoluminescence is a method of monitoring the absorbed dose of dosimeters. The irradiation crystal is heated to 500°C to display the absorbed dose as a luminescent light. The TL dosimetric properties of calcite obtained from nature were investigated in this study. Machine learning was also examined using Gaussian process regression (GPR) for stimulated TL characteristics. According to the experimental output, the TL glow curve had two main peaks located at 90°C and 240°C with good dosimetric properties. In the four regression models of GPR, the data for the heating rate of 3°C s−1have the lowest residual.
Biofabricated macrophage and fibroblast membranes synergistically promote skin wound healing
Authors: Wang Dongqing , Chen Heying , Lei Li , Chen Jun , Gao Jimin , Liu Jiahe , Li Qianyin , Xie Yajun , Hu Yi , Ni Yilu
Published: June 2022

Effective skin wound healing is a complex process involving anti‐inflammation, fibrosis, matrix reconstruction, and angiogenesis. This work aimed to integrate the macrophage‐mediated anti‐inflammation and fibroblast‐assisted matrix reconstruction for enhanced skin wound healing. Herein, we utilized the cytomembranes derived from repolarized M2 macrophages and fibroblasts to prepare the natural biologics. Results showed that the inflammatory M1 macrophages were repolarized to M2 phenotype by the M2 macrophage cytomembranes. As a consequence, the cytomembranes of M2 macrophage could facilitate the wound closure in mice. Furthermore, the addition of fibroblast membranes to the macrophage cytomembranes contributed to a better matrix reconstruction, neovascularization and angiogenesis. Next, we used a transforming growth factor‐β (TGF‐β) inhibitor to attenuate cutaneous scar formation. Therefore, our modality could promote skin wound healing and effectively suppress scar formation in the preclinical murine skin wounds. The cytomembrane biologics might provide a biocompatible and versatile tool for wound healing.
Turning adversity into opportunity: Small extracellular vesicles as nanocarriers for tumor‐associated macrophages re‐education
Authors: Donoso‐Meneses Dario , Figueroa‐Valdés Aliosha I. , Georges Nicolás , Tobar Hugo E. , Alcayaga‐Miranda Francisca
Published: June 2022

Currently, small extracellular vesicles (sEV) as a nanoscale drug delivery system, are undergoing biotechnological scaling and clinical validation. Nonetheless, preclinical pharmacokinetic studies revealed that sEV are predominantly uptaken by macrophages. Although this “sEV‐macrophage” propensity represents a disadvantage in terms of sEV targeting and their bioavailability as nanocarriers, it also represents a strategic advantage for those therapies that involve macrophages. Such is the case of tumor‐associated macrophages (TAMs), which can reprogram/repolarize their predominantly immunosuppressive and tumor‐supportive phenotype toward an immunostimulatory and anti‐tumor phenotype using sEV as nanocarriers of TAMs reprogramming molecules. In this design, sEV represents an advantageous delivery system, providing precision to the therapy by simultaneously matching their tropism to the therapeutic cell target. Here, we review the current knowledge of the role of TAMs in the tumoral microenvironment and the effect generated by the reprogramming of these phagocytic cells fate using sEV. Finally, we discuss how these vesicles can be engineered by different bioengineering techniques to improve their therapeutic cargo loading and preferential uptake by TAMs.
New Spiro‐Sesquiterpenoids from the Marine Sponge Myrmekioderma sp.
Authors: Zhou Mei‐Hong , Luo Xiang‐Chao , Zhao Hui‐Min , Lu Jing‐Rong , Dai Ying , Yu Yong , Zhang Liang , Lin Hou‐Wen , Yang Fan
Published: June 2022

Three new spiro‐sesquiterpenoids, myrmekiones A−C (1–3), were isolated from the marine sponge Myrmekioderma sp. collected from the South China Sea. The structures of 1–3 were experimentally illuminated though comprehensive NMR spectra, X‐ray diffraction analysis and calculated ECD. These three compounds possessed a special spiro skeleton. Compound 1 was characterized by a chamigrane‐type structure, it is the first time to obtain the single‐crystal of this type of oil compounds. 2 and 3 were a pair of diastereoisomers that possessed an acorane skeleton. This study expands the chemical diversity of marine origin spiro‐metabolites.
Exploring the Temperature Effect on Enantioselectivity of a Baeyer‐Villiger Biooxidation by the 2,5‐DKCMO Module: The SLM Approach
Authors: Röllig Robert , Paul Caroline E. , Duquesne Katia , Kara Selin , Alphand Véronique
Published: June 2022

Temperature is a crucial parameter for biological and chemical processes. Its effect on enzymatically catalysed reactions has been known for decades, and stereo‐ and enantiopreference are often temperature‐dependent. For the first time, we present the temperature effect on the Baeyer‐Villiger oxidation of rac‐bicyclo[3.2.0]hept‐2‐en‐6‐one by the type II Bayer‐Villiger monooxygenase, 2,5‐DKCMO. In the absence of a reductase and driven by the hydride‐donation of a synthetic nicotinamide analogue, the clear trend for a decreasing enantioselectivity at higher temperatures was observed. “Traditional” approaches such as the determination of the enantiomeric ratio (E) appeared unsuitable due to the complexity of the system. To quantify the trend, we chose to use the ‘Shape Language Modelling’ (SLM), a tool that allows the reaction to be described at all points in a shape prescriptive manner. Thus, without knowing the equation of the reaction, the substrate ee can be estimated that at any conversion.
Revealing the illumination effect on the discharge products in high‐performance Li–O2 batteries with heterostructured photocatalysts
Authors: Gong Hao , Wang Tao , Chang Kun , Li Peng , Liu Lequan , Yu Xingyu , Gao Bin , Xue Hairong , Ma Renzhi , He Jianping , Ye Jinhua
Published: June 2022

Aprotic lithium–oxygen batteries (LOBs) have been recognized as novel energy storage devices for their outstanding specific energy density, while the large discharge/charge overpotential is a tough barrier to be overcome. Here, hetero‐structured MoS2/ZnIn2S4 nanosheets have been prepared to capture visible light and the generated charge carriers are utilized for promoting both the oxygen reduction reaction and the oxygen evolution reaction. With the light illumination in the discharge process, the abundant photo‐inspired electrons serve as the reaction sites to promote the reduction of O2 into LiO2 which is finally deposited as Li2O2. On the contrary, the generated holes in the valence band can contribute to the low oxidization potential of Li2O2 during the charge process. It delivers a low charge potential of 3.29 V, with an excellent resulting energy efficiency of 96.7%, much superior to that of 69.2% in the dark condition. It is noted that the involvement of photoelectrons has influenced the growth of Li2O2 films on the MoS2/ZnIn2S4 nanosheets through the surface‐adsorption pathway. The insights from the theoretical calculation confirm that the photoelectrons favor the absorption of LiO2 and the formation of the Li2O2 film through the surface route. Therefore, this paper provides a deeper understanding of the mechanism of photo‐inspired charge carriers in LOBs and will enable further exploration of photo‐involved energy storage systems.
Unified Approach to Diverse Fused Fragments via Catalytic Dehydrative Cyclization
Authors: Basson Ashley J. , Halcovitch Nathan R. , McLaughlin Mark G.
Published: June 2022

A range of highly functionalized polycyclic fragments have been synthesized, employing a catalytic dehydrative cyclization. A range of nucleophiles are shown to be successful, with the reaction producing numerous high value motifs.
Synthesis of Oxygenated Sesquiterpenoids Enabled by Combining Metabolic Engineering and Visible‐Light Photocatalysis
Authors: Liu Chenguang , Cui Xiaoyi , Chen Wei , Ma Xiaoqiang , Prather Kristala J. , Zhou Kang , Wu Jie
Published: June 2022

The diversification of natural products to expand biologically relevant chemical space for drug discovery can be achieved by combining complementary bioprocessing and chemical transformations. Herein, genetically engineered Escherichia coli fermentation to produce amorphadiene and valencene was combined with metal‐free photocatalysis transformations to further access nootkatone, cis‐nootkatol and two hydration derivatives. In fermentation, using a closed, anaerobic condition avoided the use of organic overlay, increased the productivity, and simplified the work‐up process. Metal‐free photocatalysis hydration and allylic C−H oxidation were designed and implemented to make the whole process greener. It was shown that the anti‐Markovnikov selectivity of photocatalyzed alkene hydration could be reversed by stereo‐electronic and steric effects existing in complex natural products. The combination of bioprocessing and photocatalysis may provide an efficient and greener way to expand the chemical space for pharmaceutical, flavor and fragrance industry.
Carbon‐Supported Potassium Hydride for Efficient Low‐Temperature Desulfurization
Authors: Chang Fei , Fedorov Alexey
Published: June 2022

The industrial removal of organosulfur impurities from fossil fuels relies on transition‐metal‐based catalysts in harsh conditions (ca. 400 °C, up to 100 bar H2), yet desulfurization (DS) of refractory alkyl dibenzothiophenes (DBTs) remains challenging. Here, we report that carbon‐supported potassium hydride (KH/C) enables efficient DS of DBTs in mild conditions, viz. >97 % conversion of DBTs is achieved at 165 °C in 3–6 h while the yields of respective biphenyls are 84–95 % by using only 15 % excess of KH per a C−S bond. In addition, KH/C allows to lower the concentration of 4,6‐Me2DBT in the mesitylene solution from 1000 ppm to <3 ppm (165 °C, 20 h) and provides deoxygenation, denitrogenation and catalytic aromatic hydrogenation reactions. DS of various sulfur heterocycles by using KH/C, a transition‐metal‐free material based on earth abundant elements, is viable at low temperature and has prospects for the further development towards decentralized removal of organosulfur species from fossil fuels.
Adaptive inference for Bayesian network soft‐sensor in the presence of process and sensor drift
Authors: Khosbayar Anudari , Valluru Jayaram , Huang Biao
Published: June 2022

Due to its incorporation of prior process knowledge and handling of uncertainty in a probabilistic sense, Bayesian network (BN)‐based soft‐sensors have shown significant advantages compared to conventional regression‐based soft‐sensors. In the literature, these soft‐sensors are developed under the assumption that the process is operated around certain operating points. Due to the time‐varying nature of the process, the prediction performance of the existing BN‐based soft‐sensors may deteriorate over time. To account for this, in the current work, adaptive Bayesian inference using a random walk model for both process and sensor drift is proposed. The efficacy of the proposed approaches is demonstrated through simulation and industrial case studies, and they are shown to perform better than the conventional bias updated approach.
Peptide‐Modulated pH Rhythms
Authors: Liu Mengfei , Yuan Ling , Zhu Chenghao , Pan Changwei , Gao Qingyu , Wang Hongzhang , Cheng Zhenfang , Epstein Irving R.
Published: June 2022

Many drugs adjust and/or control the spatiotemporal dynamics of periodic processes such as heartbeat, neuronal signaling and metabolism, often by interacting with proteins or oligopeptides. Here we use a quasi‐biocompatible, non‐equilibrium pH oscillatory system as a biomimetic biological clock to study the effect of pH‐responsive peptides on rhythm dynamics. The added peptides generate feedback that can lengthen or shorten the oscillatory period during which the peptides alternate between random coil and coiled‐coil conformations. This modulation of a chemical clock supports the notion that short peptide reagents may have utility as drugs to regulate human body clocks.