bluuebunny/crossref_metadata_2025 huggingface dataset:
Inherent background coefficients for submerged cylindrical shells
Authors: Choi Myoung-Seon , Joo Young-Sang , Lee Jong-Po
Published: July 2002

The scattering of sound waves by an empty, cylindrical, elastic shell in a fluid is considered in the resonance regime. A long-standing difficulty in the application of the resonance scattering theory is that an exact expression of the acoustical background has been elusive to find over the years. The exact expression, named the inherent background coefficient, is presented here. The coefficient is uniquely determined by the generalized fluid-loading-parameter and leads to the impenetrable background coefficient in appropriate limit. Numerical calculations show that it describes the background for a shell of arbitrary thickness and material correctly over the entire frequency range.
Target flutter rate discrimination by bats using frequency-modulated sonar sounds: Behavior and signal processing models
Authors: Grossetête Anne , Moss Cynthia F.
Published: July 2002

This study utilized psychophysical data and acoustical measurements of sonar echoes from artificial fluttering targets to develop insights to the information used by FM bats to discriminate the wingbeat rate of flying insects. Fluttering targets were produced by rotating blades that moved towards the bat, and the animal learned to discriminate between two rates of movement, a reference rate (30 or 50 Hz) and a slower, variable rate. Threshold discrimination performance depended on the rotation rate of the reference target, with a difference value of 9 Hz for the reference rate of 30 Hz and 14 Hz for the reference rate of 50 Hz. Control experiments demonstrated that the bats used sonar echoes from the moving targets to perform the discrimination task. Acoustical measurements showed that the moving target produced a Doppler shift in the echo and a concomitant change in the arrival time of each frequency in the linear period FM sweep. The difference in delay between echoes from moving and stationary parts varied linearly with flutter rate and depended on the characteristics of the bat’s sonar sounds. Simulations also showed a reduction in average echo bandwidth with increasing flutter rate, which may account for a higher delay discrimination threshold using the 50-Hz reference rate. This work suggests that Doppler-induced changes in echo delays produced by fluttering targets may contribute to the FM bat’s perception of flying insect prey.
The AUDIS catalog of human HRTFs
Authors: Blauert Jens , Brueggen Marc , Bronkhorst Adelbert W. , Drullman Rob , Reynaud Gerard , Pellieux Lionel , Krebber Winfried , Sottek Roland
Published: July 2002

In the European-Union-funded project AUDIS (AUditory DISplay), a multipurpose auditory display for 3D hearing applications is being developed. The main goal is to develop a special sound generator in combination with an auditory-symbol database that can, for example, be used in the avionic and automotive industry. As the project relies heavily on binaural technology and, hence, on the availability of reliable human HRTF data, a special program for collecting data has been undertaken. In the course of this program, round-robin tests have been performed in four different laboratories. Differences in the data across the different laboratories have been analyzed. The analysis resulted in recommendations for common measuring procedures to be applied. A catalog of HRTFs has then been collected and perceptual verification tests have been performed. It is planned to make the catalog publicly available. In the presentation, the measuring methods applied and the contents of the catalog will be discussed.
An improved continuum mixture model for wave propagation in fibrous composites
Authors: Nayfeh Adnan H. , Abdelrahman Wael G.
Published: July 2002

A new improved continuum mixture model is developed for the propagation of axisymmetric longitudinal waves in fibrous composites. The major improvement on the original model of Hegemier, Gurtman, and Nayfeh [Int. J. Solids Struct. 9, 395 (1973)] is achieved by the inclusion of the axial rate of change of the radial displacement in the shear constitutive relations which was neglected previously. This model has also been extended to treat situations in which the fiber and the matrix are anisotropic. The improved model is found superior to the original one, when compared with the recently acquired experimental data and exact solutions.
Vortex sound in bass-reflex ports of loudspeakers. Part I. Observation of response to harmonic excitation and remedial measures
Authors: Roozen N. Bert , Bockholts Marije , van Eck Pascal , Hirschberg A.
Published: July 2002

At high sound pressure levels a bass-reflex port produces blowing sounds, especially in the case of small loudspeaker boxes with narrow bass-reflex ports. The blowing sounds are caused by vortex shedding of the acoustic flow at the end of the port at high flow velocities. It has been found that acoustic standing waves in the longitudinal direction of the port are excited in a pulsatile manner by the periodically generated vortices. This is demonstrated by time history measurements of the blowing sounds of a loudspeaker system with a bass-reflex port driven by a harmonic signal. Broadband turbulence sound appears to be weaker than these deterministic sounds. It has been found that, near the 1-kHz port resonance frequency, the power level of the blowing sounds can be reduced by 8 dB by using a port cross section that diverges gradually toward both port ends with a slope angle at the port ends of about 6°, and rounding the edges at both port ends.
The traveling-wave amplifier model of the cochlea adapted to dolphins
Authors: Andersen Lars N. , Au Whitlow W. L.
Published: July 2002

The traveling-wave amplifier (TWA) model of the cochlea [A. Hubbard, Science 259, 68–71 (1993)] has been shown to produce outputs that compare quite well with experimental data. A TWA model with parameters adjusted to fit the physiological properties of the dolphin cochlea was used as part of a sonar signal discrimination system. The system was tested on a cylinder wall thickness discrimination problem. Broadband echoes from cylinders with different wall thicknesses were aligned using a matched filter and envelope detection. The aligned signals were used as inputs to the TWA model and energy from different locations along the cochlea model were computed in time increments. Data were reduced by principal component analysis and finally classified by a neural network. Results from the experiment demonstrate the potential of the framework.
The perception of music by the human brain: An introductory course
Authors: Roederer Juan G.
Published: July 2002

The study of the perception of music is a fascinating interdisciplinary endeavor in which musicians, neuroscientists, psychologists, physicists, and physiologists work together. Recent advances in the understanding of how musical sounds are detected in the ear, converted into neural signals, processed, and interpreted in the brain make the subject very attractive for an elective introductory university course. It is possible to present many subject matters in a generally understandable way, without the requirement of previous knowledge beyond that of secondary level [J. G. Roederer, Physics and Psychophysics of Music, 3rd ed. (Springer-Verlag, New York, 1995); German edition: Physikalische und Psychoakustische Grundlagen der Musik (Springer-Verlag, Heidelberg)]. In such a course, many puzzling questions can be addressed (and answered!): Why do people perceive only one pitch when they listen to a musical tone made up on many harmonics? Why are there musical scales? Why is pitch resolved so well, despite the ‘‘bad’’ frequency analysis in the inner ear? What happens in the brain when sounds are imagined? What is the relationship between music and language? Why do listeners react emotionally to musical sounds? The pedagogical challenges of organizing such an interdisciplinary course will be discussed.
Binaural sluggishness in the perception of tone sequences and speech in noise
Authors: Culling John F. , Colburn H. Steven
Published: July 2002

The binaural system is well-known for its sluggish response to changes in the interaural parameters to which it is sensitive. Theories of binaural unmasking have suggested that detection of signals in noise is mediated by detection of differences in interaural correlation. If these theories are correct, improvements in the intelligibility of speech in favorable binaural conditions is most likely mediated by spectro-temporal variations in interaural correlation of the stimulus which mirror the spectro-temporal amplitude modulations of the speech. However, binaural sluggishness should limit the temporal resolution of the representation of speech recovered by this means. The present study tested this prediction in two ways. First, listeners’ masked discrimination thresholds for ascending vs descending pure-tone arpeggios were measured as a function of rate of frequency change in the NoSo and NoSπ binaural configurations. Three-tone arpeggios were presented repeatedly and continuously for 1.6 s, masked by a 1.6-s burst of noise. In a two-interval task, listeners determined the interval in which the arpeggios were ascending. The results showed a binaural advantage of 12–14 dB for NoSπ at 3.3 arpeggios per s (arp/s), which reduced to 3–5 dB at 10.4 arp/s. This outcome confirmed that the discrimination of spectro-temporal patterns in noise is susceptible to the effects of binaural sluggishness. Second, listeners’ masked speech-reception thresholds were measured in speech-shaped noise using speech which was 1, 1.5, and 2 times the original articulation rate. The articulation rate was increased using a phase-vocoder technique which increased all the modulation frequencies in the speech without altering its pitch. Speech-reception thresholds were, on average, 5.2 dB lower for the NoSπ than for the NoSo configuration, at the original articulation rate. This binaural masking release was reduced to 2.8 dB when the articulation rate was doubled, but the most notable effect was a 6–8 dB increase in thresholds with articulation rate for both configurations. These results suggest that higher modulation frequencies in masked signals cannot be temporally resolved by the binaural system, but that the useful modulation frequencies in speech are sufficiently low (<5 Hz) that they are invulnerable to the effects of binaural sluggishness, even at elevated articulation rates.
Influence of primary frequencies ratio on distortion product otoacoustic emissions amplitude. II. Interrelations between multicomponent DPOAEs, tone-burst-evoked OAEs, and spontaneous OAEs
Authors: Moulin A.
Published: July 2002

Distortion product otoacoustic emissions (DPOAEs) are used widely in humans to assess cochlear function. It is well known that 2f1-f2 DPOAE amplitude increases as the f2/f1 ratio increases from 1.0 to about 1.20, and then decreases as the f2/f1 ratio increases above 1.20, showing an amplitude ratio function, which is thought to be related to cochlear filtering properties. Different lower sideband DPOAEs are believed to show the same amplitude ratio functions as the 2f1-f2 DPOAE, with a magnitude peak situated at a constant DPOAE frequency relative to f2. More recently, several studies have suggested the involvement of a DPOAE component coming from its own distortion product place as well as the DPOAE component coming from the f2 place. To investigate DPOAE generation sites and the importance of the DPOAE frequency place, amplitude ratio functions of 2f1-f2, 3f1-2f2, 4f1-3f2 and 2f2-f1, 3f2-2f1, 4f2-3f1 DPOAE components have been systematically studied in 18 normally hearing subjects, using an f2 fixed, f1 sweep method, and an f1 fixed, f2 sweep method, at ten different f2 frequencies. Results show a dependency of the distortion magnitude peak on f2 frequency for each lower sideband DPOAE, and a small frequency shift of the distortion peak for the high order lower sideband DPOAE components. Strong correlation between the different lower sideband DPOAE amplitude were obtained, whether they were recorded with the same f1 (and a different f2) or with the same f2 (and a different f1), suggesting that lower side-band DPOAE amplitude does not depend on small variations in the f2 frequency. Moreover, correlations between DPOAE amplitude and tone-burst evoked otoacoustic emissions (TBOAEs) are highly significant for TBOAEs centered at the f2 frequency and at 12 octave below the f2 frequency, suggesting some degree of importance of the cochlear status at frequencies below f2 in DPOAE amplitude. Subjects presenting spontaneous otoacoustic emissions showed a greater lower sideband DPOAE amplitude recorded for low f2/f1 ratios, and a distortion magnitude peak shifted towards higher frequencies. The best correlation between upper sideband DPOAE amplitude and lower sideband DPOAE amplitude occurred for lower sideband DPOAEs generated by an f2 frequency 12 octave to 1 octave below the primaries used to generate upper sideband DPOAEs, suggesting a site of generation basal to f2 for the upper sideband DPOAEs. Correlations between TBOAE amplitude and upper sideband DPOAE amplitude agreed with a site of upper sideband DPOAE generation basal to f2, and which would move with the DPOAE frequency itself.
Flexural edge waves and Comments on “A new bending wave solution for the classical plate equation” [J. Acoust. Soc. Am. 104, 2220–2222 (1998)]
Authors: Norris A. N. , Krylov V. V. , Abrahams I. D.
Published: July 2002

A brief review is presented of the theory of flexural edge waves, first predicted in 1960 by Yu K. Konenkov using Kirchhoff plate theory. It is demonstrated that the flexural edge wave is also predicted by Mindlin’s plate theory, and that the prediction agrees with measured data. It is noted that the edge wave was erroneously presented as a new type of bending wave solution in a recently published paper in this journal.
Sound propagation in street canyons: Comparison between diffusely and geometrically reflecting boundaries
Authors: Kang Jian
Published: July 2002

This paper systematically compares the sound fields in street canyons with diffusely and geometrically reflecting boundaries. For diffuse boundaries, a radiosity-based theoretical/computer model has been developed. For geometrical boundaries, the image source method has been used. Computations using the models show that there are considerable differences between the sound fields resulting from the two kinds of boundaries. By replacing diffuse boundaries with geometrical boundaries, the sound attenuation along the length becomes significantly less; the RT30 is considerably longer; and the extra attenuation caused by air or vegetation absorption is reduced. There are also some similarities between the sound fields under the two boundary conditions. For example, in both cases the sound attenuation along the length with a given amount of absorption is the highest if the absorbers are arranged on one boundary and the lowest if they are evenly distributed on all boundaries. Overall, the results suggest that, from the viewpoint of urban noise reduction, it is better to design the street boundaries as diffusely reflective rather than acoustically smooth.
The Visco-elastic Behavior of Confined Thin Films of Bitumen in Tension Compression
Authors: Dickinson E. J. , Witt H. P.
Published: July 2002

The behavior of confined thin films of a bitumen under sinusoidal loading both in shear and in a direction normal to the plane of the film (tension/compression) has been investigated. For small strains, behavior in tension/compression like that in shear, is linear and thermorheologically simple and the temperature dependence of the rheological parameters is the same in each case. In tension/compression, the degree of confinement can be defined by the ratio of the radius of the confining plates (r) to the thickness of the film (d). For confinement ratios greater than about one, the longitudinal complex modulus |M*| was found to be greater than three times the complex shear modulus 3|G*| (the value expected for shear behavior). The complex modulus ratio |M*|/3|G*|, where |M*| and |G*| are measured at the same frequency and temperature, was found to be approximately proportional to the square of the confinement ratio over the confinement ratio range 4.5 to 45. This relationship should be predicted by the theory of the purely elastic situation. The energy loss factor under sinusoidal loading, π/2 tan φ (where φ is the angular phase difference between stress and strain), was found to be different in tension/compression from that in shear. As the confinement ratio increases, the energy loss factor decreases more rapidly with frequency than for shear conditions. To indicate the temperature/frequency region for this decrease, the behavior where tan φ=1 was evaluated and found to correspond to an |M*| value of about 8×108 dynes/cm (the same value is obtained in shear for tan φ=1). The particular relationship (for the bitumen tested) between the temperature, the frequency, and the confinement ratio when tan φ=1 was determined for the range of frequencies and temperatures covered experimentally. The theoretical implications of the results and their relation to the deformation, fracture, and fatigue behavior of bitumen bonded road surfacing materials are briefly discussed.
Crystallographic studies and X-ray diffraction patterns of Ba5R8Zn4O21 by Rietveld refinements
Authors: Wong-Ng W. , Kaduk J. A. , Dillingham J.
Published: July 2002

The structure of the Ba5R8Zn4O21 series (R=lanthanides) was investigated using X-ray Rietveld refinements. The compounds were successfully prepared for R=Eu, Gd, Dy, Ho, Er, Tm, and Yb. Ba5R8Zn4O21 crystallizes in the tetragonal space group I4/m; for R=Yb to Eu, a ranges from 13.635 02(5) to 13.960 62(9) Å, c from 5.658 46(3) to 5.784 83(5) Å, and V from 1051.987(8) to 1127.459(14) Å3. The Zn2+ ions adopt a fivefold distorted square pyramidal coordination. The seven-coordinate R3+ reside in monocapped trigonal prisms. These prisms share edges, and form layers stacked along the c axis. There are two types of BaO polyhedra: bicapped square prisms (BaO10), and irregular BaO10 polyhedra. For larger R, Ba5R8Zn4O21 was not stable, and tetragonal BaR2ZnO5(La, Nd) and orthorhombic BaR2ZnO5(Sm) phases were observed instead.
State Policies Could Impede New Efforts to Increase Access to Medications for Opioid Use Disorder
Authors: Barsky Benjamin A. , Mehrotra Ateev , Huskamp Haiden A.
Published: March 2023

This Viewpoint discusses state policies that could impede access to medications for opioid use disorder via telemedicine.
Replicability and Reproducibility
Authors: Kedron Peter
Published: March 2023

Reproducing and replicating the results of other researchers is a fundamental form of error correction in science. However, reproducing and replicating prior research can be difficult for several reasons. A researcher may not make their original data available for reanalysis, or may not provide sufficient details about the design of a study, protocols used, and analytical procedures to allow a result to be reproduced or replicated. At the same time, researchers have a limited ability to control some of the complex systems they study, which complicates repetition of prior analyses. The complex systems geographers study, the variety of approaches geographers use to generate new knowledge, and the intricacies of spatial data analysis all make reproducing and replicating geographic research challenging. Nonetheless, being able to reproduce and replicate geographic research is essential to assessing the reliability of knowledge.
Mobilities
Authors: Adey Peter
Published: March 2023

Debates around “mobilities” have emerged in multiple forms as a disciplinary and interdisciplinary concern. Within human geography it has achieved significant importance alongside other key geographical frames of reference or concepts, such as place and scale. However, the emergence of mobilities has quite a convoluted history of turns and returns, and alternative histories. There have also been fractured discussions around mobility between important subfields within geography. Most crucially, as a set of approaches to the study of movement by human and nonhuman things, mobilities can be seen to have animated key geographical concepts, transformed the focus of much empirical work on movement and nonmovement, and augmented and rethought research methods. Most recently the notion of “mobility justice” has proven a galvanizing approach towards questions of social, racial, and environmental mobility (in)justices.
Nanomaterials Responsive to Endogenous Biomarkers for Cardiovascular Disease Theranostics
Authors: Wei Chuang , Jiang Zeyu , Li Congcong , Li Peifeng , Fu Qinrui
Published: March 2023

Cardiovascular disease (CVD) is the number one cause of death worldwide, which propels the development of advanced technologies for CVD diagnosis and treatment. Biomarker‐responsive nanomaterials are appealing therapeutic platforms that provide new horizons for CVD theranostics. In this review, recent advances in nanomaterials with endogenous biomarkers as stimuli or targets for CVD theranostics is presented. First, the categories of biomarkers involved are comprehensively itemized based on pathological mechanisms including pH, reactive oxygen species, lipids, enzymes, macrophage receptors, subendothelium components, platelet receptors, inflammation, and osteopontin. The role of these biomarkers in bridge‐building between nanomaterials and CVD is then presented. Next, the biomedical applications of nanomaterials responsive to endogenous biomarkers as stimuli or targets for the diagnosis and treatment of CVD are elaborated. Finally, the challenges and future research directions of biomarker‐responsive nanomaterials in CVD are also discussed. This review will provide scientific guidance to facilitate clinical applications of biomarker‐responsive nanomaterials.
Rational Design of PDI‐Based Linear Conjugated Polymers for Highly Effective and Long‐Term Photocatalytic Oxygen Evolution
Authors: Liu Di , Yang Xuan , Chen Peiyan , Zhang Xinling , Chen GaoYuan , Guo Qiwei , Hou Huan , Li Yi
Published: March 2023

Constructed through relatively weak noncovalent forces, the stability of organic supramolecular materials has shown to be a challenge. Herein, the designing of a linear conjugated polymer is proposed through creating a chain polymer connected via bridging covalent bonds in one direction and retainingπ‐stacked aromatic columns in its orthogonal direction. Specifically, three analogs of linear conjugated polymers through tuning the aromatic core and its covalently linked moiety (bridging group) within the building block monomer are prepared. Cooperatively supported by strongπ–πstacking interactions from the extended aromatic core of perylene and favorable dipole–dipole interactions from the bridging group, the as‐expected high crystallinity, wide light absorption, and increased stability are successfully achieved for Oxamide‐PDI (perylene diimide) through ordered molecular arrangement, and present a remarkable full‐spectrum oxygen evolution rate of 5110.25 µmol g−1 h−1without any cocatalyst. Notably, experimental and theoretical studies reveal that large internal dipole moments within Oxamide‐PDI together with its ordered crystalline structure enable a robust built‐in electric field for efficient charge carrier migration and separation. Moreover, density functional theory (DFT) calculations also reveal oxidative sites located at carbon atoms next to imide bonds and inner bay positions based on proven spatially separated photogenerated electrons and holes, thus resulting in highly efficient water photolysis into oxygen.
Engineering Fano‐Resonant Hybrid Metastructures with Ultra‐High Sensing Performances
Authors: Lio Giuseppe Emanuele , Ferraro Antonio , Kowerdziej Rafał , Govorov Alexander O. , Wang Zhiming , Caputo Roberto
Published: March 2023

Metamaterials‐based sensors are of primary interest in physics, materials science, medicine, and biophysics thanks to their ability to detect very tiny amount of molecules spread into a medium. Here, a metastructure utilizing the epsilon near zero (εNZ) and Fano–Rabi physics is engineered to design a system with ultra‐high sensitivity. So far, a dedicated study of such systems has been missing. In this work, the authors report the results of their efforts to fill the gap by considering a metasurface, designed as a periodical array of rings with a cross in their center, placed on top of a silver (Ag) and zinc oxide (ZnO) epsilon near‐zero optical nanocavity (εNZ‐ONC) metamaterial. The accurate selection of the metasurface parameters allows the design of a sensor exhibiting an extremely high sensitivity of about 16 000 and 21 000 nm RIU−1 depending on incoming polarization. This work paves the way for the development of novel groundbreaking devices for biomedical and environmental application based on plasmonic and photonic design principles.
Fluorescence Filter Nanoarchitectonics with Polydiacetylene‐Based Supramolecular Chiral Gel for Generating Tunable Circularly Polarized Luminescence
Authors: Zhai Donghua , Jiang Jian , Yuan Chenhuan , Wang Decai , Jiang Yuqian , Liu Minghua
Published: March 2023

Circularly polarized luminescence (CPL) can be generated from chiral luminescent materials. It can also be achieved from achiral emissive dyes by selectively filtering their fluorescence with chiroptical active materials. In this work, a novel polydiacetylene‐based supramolecular chiral gel is fabricated as a handedness‐selective fluorescence filter for generating CPL. The gelator consists of a diacetylene alkyl chain and a chiral histidine (His) head group (HisDA). It can self‐assemble into nanoribbon and turn into the blue phase, purple phase and red phase polydiacetylene‐His (HisPDA) upon photopolymerization. The resulting L/D‐HisPDA gels show variable circular dichroism (CD) with the change in color. Furthermore, multiple CPL signals are achieved after fluorescence excited with achiral dyes D1–D3 passing through HisPDA gel. The intensity of CPL increases gradually in both D1 and D3 dye systems along with the change of the HisPDA gel from blue phase to red phase, while the CPL signal is inverted for the D2 dye system. The handedness of the CPL signal is opposite to the CD signal of HisPDA gel in all the cases, demonstrating that CPL is originated through a handedness‐selective fluorescence adsorption mechanism. This study offers a new strategy for obtaining tunable CPL via adjustable chiral fluorescence filters.
Syntheses and Photophysical Properties of Pnictogen‐ and Chalcogen‐Containing Diheteroanthracenes
Authors: Fujii Toshiki , Urushizaki Aya , Imoto Hiroaki , Naka Kensuke
Published: March 2023

Herein, we synthesized pnictogen (P, As, Sb)‐ and chalcogen (O, S)‐containing diheteroanthracene derivatives with 8π‐electron systems. As opposed to the pnictogen atoms, the chalcogen atoms significantly affected the conformations of the diheteroanthracenes. In addition, the S‐containing compounds exhibited relatively large Stokes shifts owing to significant structural relaxations compared with those of the O‐containing compounds. Computational calculations revealed that the bent conformations of the S‐containing compounds in their ground states planarized upon photoexcitation.
A Traceless Chiral Shift Reagent Based on Nonbonding Interactions with Single‐Handed Helical Poly(quinoxaline‐2,3‐diyl)
Authors: Fujie Takaya , Yamamoto Takeshi , Suginome Michinori
Published: March 2023

A single‐handed poly(quinoxaline‐2,3‐diyl) (PQX) has been found to serve as a new type of chiral shift reagent (CSR) for determining the enantiomeric ratio by NMR spectroscopy. Even though there is no specific binding site in the PQX, its nonbonding interaction with chiral analytes leads to a significant shift of the NMR chemical shift, allowing quantification of the enantiomeric ratio. The new type of CSR has the advantages of a wide scope of analytes including ethers, haloalkanes, and alkanes, easy tunability of the degree of chemical shifts by measurement temperature, and erasability of proton signals of CSR because of the short spin‐spin (T2) relaxation of the macromolecular scaffold.
Methylierung nicht‐aktivierter Alkene mit modifizierten Methyltransferasen zur Diversifizierung von Terpenoiden
Authors: Aberle Benjamin , Kowalczyk Daniel , Massini Simon , Egler‐Kemmerer Alexander‐N. , Gergel Sebastian , Hammer Stephan C. , Hauer Bernhard
Published: March 2023

Terpenoide sind aus Isopren‐Bausteinen aufgebaut und haben zahlreiche biologische Funktionen. Eine selektive Modifizierung ihres Kohlenstoffgerüsts hat das Potenzial die biologischen Aktivitäten zu verändern oder zu optimieren. Die Synthese von Terpenoiden mit einem nicht‐natürlichen Kohlenstoffgerüst ist jedoch aufgrund der Komplexität dieser Moleküle oft ein schwieriges Unterfangen. In dieser Arbeit berichten wir über die Identifizierung und das Engineering von (S)‐Adenosyl‐l‐Methionin‐abhängigen Sterol‐Methyltransferasen für die selektive C‐Methylierung von linearen Terpenoiden. Das entwickelte Enzym katalysiert die selektive Methylierung von nicht‐aktivierten Alkenen in Mono‐, Sesqui‐ und Diterpenoiden zur Herstellung von C11‐, C16‐ und C21‐Derivaten. Die präparative Umsetzung und Isolation der Produkte zeigt, dass dieser Biokatalysator die Bildung von C−C‐Bindungen mit hoher Chemo‐ und Regioselektivität durchführt. Die Methylierung des Alkens erfolgt höchstwahrscheinlich über ein Carbokation‐Zwischenprodukt und eine regioselektive Deprotonierung. Diese Methode eröffnet neue Wege zur Modifizierung des Kohlenstoffgerüsts von Alkenen im Allgemeinen und Terpenoiden im Besonderen.
Triphenylamine‐Derived Solid‐State Emissive Carbon Dots for Multicolor High‐Efficiency Electroluminescent Light‐Emitting Diodes
Authors: Zhao Biao , Ma Huanyu , Jia Haoran , Zheng Mengyun , Xu Kunxiang , Yu Runnan , Qu Songnan , Tan Zhan'ao
Published: March 2023

Two kinds of triphenylamine‐derived solid‐state emissive carbon dots (CDs) with orange and yellow color are facilely synthesized through solvothermal treatment, taking advantage of the nonplanar structure and good carrier mobility of triphenylamine unit. Theoretical calculations show that the triphenylamine structure could greatly inhibit the direct π–π stacking of aromatic skeletons and enhance the fluorescence properties of CDs in aggregation state. By adopting the CDs as single emissive layer, high‐performance orange‐color and green‐color electroluminescent light‐emitting diodes (LEDs) are successfully fabricated, with maximum brightness of 9450/4236 cd m−2, high current efficiency of 1.57/2.34 cd A−1 and low turn‐on voltage of 3.1/3.6 eV are respectively achieved. Significantly, white‐color LED device is further prepared. This work provides a universal platform for the construction of novel solid‐state emissive CDs with significant applications in photoelectric device.
Manipulating Electric Double Layer Adsorption for Stable Solid‐Electrolyte Interphase in 2.3 Ah Zn‐Pouch Cells
Authors: Wang Yu , Liang Bochun , Zhu Jiaxiong , Li Geng , Li Qing , Ye Ruquan , Fan Jun , Zhi Chunyi
Published: March 2023

Constructing a reliable solid‐electrolyte interphase (SEI) is imperative for enabling highly reversible zinc metal (Zn0) electrodes. Contrary to conventional “bulk solvation” mechanism, we found the SEI structure is dominated by electric double layer (EDL) adsorption. We manipulate the EDL adsorption and Zn2+ solvation with ether additives (i.e. 15‐crown‐5, 12‐crown‐4, and triglyme). The 12‐crown‐4 with medium adsorption on EDL leads to a layer‐structured SEI with inner inorganic ZnFx/ZnSx and outer organic C−O−C components. This structure endows SEI with high rigidness and strong toughness enabling the 100 cm2 Zn||Zn pouch cell to exhibit a cumulative capacity of 4250 mAh cm−2 at areal‐capacity of 10 mAh cm−2. More importantly, a 2.3 Ah Zn||Zn0.25V2O5⋅n H2O pouch cell delivers a recorded energy density of 104 Wh Lcell−1 and runs for >70 days under the harsh conditions of low negative/positive electrode ratio (2.2 : 1), lean electrolyte (8 g Ah−1), and high‐areal‐capacity (≈13 mAh cm−2).
CuNi Nanoalloys with Tunable Composition and Oxygen Defects for the Enhancement of the Oxygen Evolution Reaction**
Authors: Gioria Esteban , Li Shuang , Mazheika Aliaksei , Naumann d'Alnoncourt Raoul , Thomas Arne , Rosowski Frank
Published: March 2023

Colloidal synthesis is an excellent tool for the study of cooperative effects in nanoalloys. In this work, bimetallic CuNi nanoparticles of defined size and composition are fully characterized and tested for the oxygen evolution reaction. Copper addition to nickel leads to modifications in the structural and electronic properties, showing a higher concentration of surface oxygen defects and formation of active Ni3+ sites under reaction conditions. The ratio OV/OL between oxygen vacancies and lattice oxygen shows a clear correlation with the overpotential, being an excellent descriptor of the electrocatalytic activity. This is attributed to modifications in the crystalline structure, leading to lattice strain and grain size effects. Bimetallic Cu50Ni50NP showed the lowest overpotential (318 mV vs RHE), low Tafel slope (63.9 mV dec−1), and excellent stability. This work unravels the relative concentration between oxygen defects and lattice oxygen (OV/OL) as an excellent descriptor of the catalytic activity of bimetallic precatalysts.
Methylation of Unactivated Alkenes with Engineered Methyltransferases To Generate Non‐natural Terpenoids
Authors: Aberle Benjamin , Kowalczyk Daniel , Massini Simon , Egler‐Kemmerer Alexander‐N. , Gergel Sebastian , Hammer Stephan C. , Hauer Bernhard
Published: March 2023

Terpenoids are built from isoprene building blocks and have numerous biological functions. Selective late‐stage modification of their carbon scaffold has the potential to optimize or transform their biological activities. However, the synthesis of terpenoids with a non‐natural carbon scaffold is often a challenging endeavor because of the complexity of these molecules. Herein we report the identification and engineering of (S)‐adenosyl‐l‐methionine‐dependent sterol methyltransferases for selective C‐methylation of linear terpenoids. The engineered enzyme catalyzes selective methylation of unactivated alkenes in mono‐, sesqui‐ and diterpenoids to produce C11, C16 and C21 derivatives. Preparative conversion and product isolation reveals that this biocatalyst performs C−C bond formation with high chemo‐ and regioselectivity. The alkene methylation most likely proceeds via a carbocation intermediate and regioselective deprotonation. This method opens new avenues for modifying the carbon scaffold of alkenes in general and terpenoids in particular.
A New Series of D1‐A‐D2‐type ESIPT‐TICT‐AIE Active Orange‐to‐red Emissive Unsymmetrical Azines: Their All‐throughout Mechanochemical Synthesis and Exploration of Photophysical Properties
Authors: Bhosle Akhil A. , Banerjee Mainak , Hiremath Sharanabasava D. , Bhasikuttan Achikanath C. , Chatterjee Amrita
Published: March 2023

Azines are interesting compounds exhibiting aggregation‐induced‐emission (AIE) and twisted‐intramolecular‐charge‐transfer (TICT) properties that have exciting prospects in chemosensing and bioimaging applications. They commonly have symmetrical structures and there is no report on red‐emissive unsymmetrical azines. Herein, we report a novel class of orange‐to‐red emissive hydroxybenzothiazole(HBT)‐based unsymmetrical azines (BTDPA) with triple photophysical characteristics of ESIPT‐TICT‐AIE. The dyes were synthesized by an all‐throughout mechanochemical route in a sustainable way. They displayed D1‐A‐D2 character and fluoresce strongly both in organic solvents due to ESIPT and in the solid state by AIE via TICT. The incorporation of different electron‐withdrawing groups (EWGs) and electron‐donating groups (EDGs) at either HBT or diphenyl‐methylene moiety resulted in tunable fluorescence properties. The red‐emissive character was achieved by keeping EDG both at HBT (−OMe) and the diphenyl‐methylene moiety (−NMe2) (λem 680 nm). The dyes exhibited good quantum yields, large Stoke shifts (upto 293 nm) and were utilized in nitroaromatics and Cu2+ sensing.
Ferritin in cancer therapy: A pleiotropic tumoraffin nanocage‐based transport
Authors: Deng Guodong , Li Yang , Liang Ning , Hu Pingping , Zhang Yan , Qiao Lili , Zhang Yingying , Xie Jian , Luo Hui , Wang Fei , Chen Fangjie , Liu Fengjun , Xu Deguo , Zhang Jiandong
Published: March 2023

Background

Ferritin, a ubiquitously distributed iron storage protein, can specifically target tumor cells through transferrin receptor 1. Due to its rearrangeable nanocage structure, ferritin can be loaded with anticancer drugs. Combined with amino acid modifications on the outer‐ and/or inner‐spaces of the nanocage, ferritins can be further coupled with antigens, antibodies, and nucleotide sequences. Since ferritin is naturally presented in the human body, when used in vivo, ferritin exhibits good biocompatibility, and no immunogenic response occurs. These makes ferritin an ideal nanocarrier which shows broad application prospects in cancer therapy.

Methods

In this study, to find articles, a search was made in PubMed with the keywords ferritin, drug delivery, drug delivery, and cancer treatment.

Results

According to the investigation, some studies suggest that ferritin can be loaded with drugs and targeted for delivery to tumor tissue. Therefore, ferritin nanocarriers loaded with drugs can be used in chemotherapy, photodynamic therapy (PDT), photothermal therapy (PTT) and immunotherapy. Importantly, the specific targeting of ferritin nanocarriers to tumor cells increases the effectiveness of related therapies and reduces side effects.

Conclusions

We conclude in this paper that the superior properties of ferritin nanocarriers as an emerging drug delivery system make them a promising cancer treatment strategy. In the future, it is worth conducting clinical trials to further investigate the safety and efficacy of ferritin nanocarriers in patients.
Transcriptomic data in tumor‐adjacent normal tissues harbor prognostic information on multiple cancer types
Authors: Oh Euiyoung , Lee Hyunju
Published: March 2023

Background

In identifying prognostic markers in cancer, the roles of tumor‐adjacent normal tissues are often confined to drawing expression differences between tumor and normal tissues rather than being treated as the main targets of investigations. Thus, differential expression analysis between tumors and adjacent normal tissues is performed prior to prognostic analysis in previous studies. However, recent studies have suggested that the prognostic relevance of differentially expressed genes (DEGs) is insignificant for some cancers, contradicting conventional approaches

Methods

This study investigated the prognostic efficacy of transcriptomic data from tumors and adjacent normal tissues using The Cancer Genome Atlas dataset. Prognostic analysis using Cox regression models and survival prediction using machine‐learning models and feature selection methods were employed.

Results

The results revealed that for kidney, liver, and head and neck cancer, adjacent normal tissues harbored higher proportions of prognostic genes and exhibited better survival prediction performance than tumor tissues and DEGs in machine‐learning models. Furthermore, the application of a distance correlation‐based feature selection method to kidney and liver cancer using external datasets revealed that the selected genes for adjacent normal tissues exhibited higher prediction performance than those for tumor tissues. The study results suggest that the expression levels of genes in adjacent normal tissues are potential prognostic markers. The source code of this study is available athttps://github.com/DMCB‐GIST/Survival_Normal.
Minimizing Product Inhibition in DNA Self‐Replication: Insights for Prebiotic Replication from the Role of the Enzyme in Lesion‐Induced DNA Amplification**
Authors: Park Hansol , Parshotam Shyam , Hales Sarah C. , Mittermaier Anthony K. , Gibbs Julianne M.
Published: March 2023

Self‐replication of nucleic acids in the absence of enzymes represents an important and poorly understood step in the origin of life as such reported systems are strongly hindered by product inhibition. Studying one of the few successful examples of enzymatic DNA self‐replication based on a simple ligation chain reaction, lesion‐induced DNA amplification (LIDA), can shed light on how this fundamental process may have originally evolved. To identify the unknown factors that lead LIDA to overcome product inhibition we have employed isothermal titration calorimetry and global fitting of time‐dependent ligation data to characterize the individual steps of the amplification process. We find that incorporating the abasic lesion into one of the four primers substantially decreases the stability difference between the product and intermediate complexes compared with complexes without the abasic group. In the presence of T4 DNA ligase this stability gap is further reduced by two orders of magnitude revealing that the ligase also helps overcome product inhibition. Kinetic simulations reveal that the intermediate complex stability and the magnitude of the ligation rate constant significantly impact the rate of self‐replication, suggesting that catalysts that both facilitate ligation and stabilize the intermediate complex might be a route to efficient nonenzymatic replication.
Boronic Acid Assisted Self‐Assembly of Functional RNAs
Authors: Lelièvre‐Büttner Amandine , Schnarr Theodor , Debiais Mégane , Smietana Michael , Müller Sabine
Published: March 2023

Boronate esters formed by reaction of an oligonucleotide carrying a 5′‐boronic acid moiety with the 3′‐terminalcis‐diol of another have been shown previously to assist assembly of fragmented DNAzymes. Here we demonstrate that boronate esters replacing the natural phosphodiester linkage at selected sites of two functional RNAs, the hairpin ribozyme and the Mango aptamer, allow assembly of functional structures. The hairpin ribozyme, a small naturally occurring RNA that supports the reversible cleavage of appropriate RNA substrates, is very sensitive to fragmentation. Splitting the ribozyme at four different sites led to a significant decrease or even loss of cleavage and ligation activity. Ribozymes assembled from fragments capable of boronate ester formation showed restoration of cleavage activity in some but not all cases, dependent on the split site. Ligation proved to be more challenging, no supportive effect of the boronate ester was observed. Split variants of the Mango aptamer also showed a dramatic loss of functionality, which however, was restored when 5′‐boronic acid modified fragments were used for assembly. These studies show for the first time that boronate esters as internucleoside linkages can act as surrogates of natural phosphodiesters in functional RNA molecules.
Sweetened Alkylated Verdazyls Effectively Kill Cancer Cells under Light Irradiation
Authors: Votkina Darya E. , Abramov Alexander A. , Kovalskaya Ekaterina S. , Plotnikov Evgenii V. , Postnikov Pavel S. , Stepanova Elena V. , Petunin Pavel V.
Published: March 2023

The development of novel photo‐dynamic therapy (PDT) agents enabling to treat the oxygen‐deficient tumors is the emerging tasks for the modern medicinal chemistry. Herein, we describe the design and preparation of water‐soluble agents for PDT which generate active radical species upon light irradiation. Two conjugates of carbohydrates with 1,2,4,6‐substituted‐1,4‐dihydro‐1,2,4,5‐tetrazin‐3(2H)‐ones (AlkVZs) demonstrated high oxygen‐independent cytotoxicity on PC‐3 and Jurkat cancer cells under light irradiation combining with low toxicity in the dark. The efficacy of prepared compounds was estimated using MTT and Alamar Blue tests as well as microscopic dead/live colored images and flow cytometry. The analysis of obtained results reveals the influence of sugar moiety on the activity of AlkVZs. We believe that obtained compounds have high potency as platform for design of new agents for photo‐dynamic therapy.
Conjugates of 1,3‐ and 1,2‐Acylglycerols with Stigmasterol: Synthesis, NMR Characterization, and Impact on Lipid Bilayers
Authors: Gładkowski Witold , Chojnacka Anna , Włoch Aleksandra , Pruchnik Hanna , Grudniewska Aleksandra , Dunal Anna , Dudek Anita , Maciejewska Gabriela , Rudzińska Magdalena
Published: March 2023

The main aim of research was synthesis and spectroscopic characterization of new conjugates in which stigmasterol was linked via carbonate or succinyl linker with 1,3‐ and 1,2‐acylglycerols of palmitic and oleic acid. Acylglycerols containing stigmasterol residue at internal position have been synthesized from 2‐benzyloxypropane‐1,3‐diol or dihydroxyacetone. Their asymmetric counterparts containing stigmasterol residue attached to sn‐3 position have been obtained from (S)‐solketal. Eight synthesized conjugates were used to create the liposomes as nanocarriers of phytosterols to increase their stability and protect them from degradation during thermal‐oxidative treatments. Fluorimetric and ATR‐FTIR methods were used to determine the impact of synthesized conjugates on the physicochemical properties of the lipid bilayer. The results indicate that conjugates with palmitic acid are better candidates for use as the potential stigmasterol nanocarriers compared to those with oleic acid because they increase the stiffness of the lipid bilayer and temperature of the main phase transition. The obtained results are the first step in designing of stigmasterol‐enriched liposomal carriers with higher thermo‐oxidative stability for their potential use in the food industry.
Structural Reconstruction Strategy Enables CoFe LDHs for High‐Capacity NH4+ Storage and Application in High‐Energy Density Ammonium‐Ion Hybrid Supercapacitors**
Authors: Wang Dewei , Sun Jiaqi , Chen Long
Published: March 2023

Exploration of high‐performance aqueous ammonium‐ions hybrid supercapacitor has attracted tremendous research attention recently. Herein, structural reconstructed cobalt‐iron layered double hydroxides (SR‐CoFe LDHs) featuring copious structure defects (i. e., oxygen‐vacancies, M−O bonds, MOO− bonds, coexistence of Co2+/Co3+ and Fe2+/Fe3+) are reported as a high‐capacity cathode for NH4+ storage. The resulting SR‐CoFe LDHs can deliver a reversible capacity of 167.9 mAh g−1 at 0.5 A g−1, which is 3.3 folds higher than that of pristine CoFe‐LDHs. Ex‐situ experimental results and theoretical studies denote that the presence of structural defects in the CoFe‐LDHs can lower the NH4+ adsorption energy and induced electron delocalization to enhance the electrical conductivity, rendering the CoFe‐LDHs exhibits excellent performance for NH4+ storage. As a proof of concept, ammonium‐ion hybrid supercapacitor has been assembled with CoFe‐LDHs as the cathode and hierarchical carbon as the anode, which can deliver a large specific capacitance of 238.3 F g−1, long cycle stability over 10000 cycles, and high energy density of 66.2 Wh kg−1 within a wide working voltage of 2 V. Overall, this work offers some insights into the design of high capacity cathode for aqueous NH4+ storage and also illustrates the construction of aqueous hybrid devices with NH4+ as the charge carrier.