The genome of the T7 bacteriophage can be mapped by using sequence-specific methyltransferase-induced labeling of DNA. In their Communication on page 3578 ff., E. Weinhold, S. Weiss, Y. Ebenstein, and co-workers show that the location of RNA polymerases that are bound to DNA can be visualized as a linear optical barcode, which allows structural variations in genomic DNA to be analyzed and provides an extra layer of contextual information about the genome at the single-molecule level.
Flat optics foresees a new era of ultra-compact optical devices, where metasurfaces serve as the foundation. Conventional designs of metasurfaces start with a certain structure as the prototype, followed by an extensive parametric sweep to accommodate the requirements of phase and amplitude of the emerging light. Regardless of how computation-consuming the process is, a predefined structure can hardly realize the independent control over the polarization, frequency, and spatial channels, which hinders the potential of metasurfaces to be multifunctional. Besides, achieving complicated and multiple functions calls for designing a meta-optic system with multiple cascading layers of metasurfaces, which introduces super exponential complexity. In this work we present an artificial intelligence framework for designing multilayer meta-optic systems with multifunctional capabilities. We demonstrate examples of a polarization-multiplexed dual-functional beam generator, a second order differentiator for all-optical computation, and a space-polarization-wavelength multiplexed hologram. These examples are barely achievable by single-layer metasurfaces and unattainable by traditional design processes.
Das Genom des Bakteriophagen T7 kann mithilfe einer sequenzspezifischen, Methyltransferase-induzierten DNA-Markierung durchmustert werden. In der Zuschrift auf S. 3638 zeigen E. Weinhold, S. Weiss, Y. Ebenstein et al., wie die Positionen von RNA-Polymerasen, die an DNA gebunden sind, als linearer optischer Strichcode verbildlicht werden können. Dadurch werden Strukturvariationen der genomischen DNA analysierbar, und zusätzliche Informationen über das Genom werden auf Einzelmolekülebene zugänglich.
The past decade has seen an explosive growth in the utilization of single-molecule techniques for the study of complex systems. The ability to resolve phenomena otherwise masked by ensemble averaging has made these approaches especially attractive for the study of biological systems, where stochastic events lead to inherent inhomogeneity at the population level. The complex composition of the genome has made it an ideal system to study at the single-molecule level, and methods aimed at resolving genetic information from long, individual, genomic DNA molecules have been in use for the last 30 years. These methods, and particularly optical-based mapping of DNA, have been instrumental in highlighting genomic variation and contributed significantly to the assembly of many genomes including the human genome. Nanotechnology and nanoscopy have been a strong driving force for advancing genomic mapping approaches, allowing both better manipulation of DNA on the nanoscale and enhanced optical resolving power for analysis of genomic information. During the past few years, these developments have been adopted also for epigenetic studies. The common principle for these studies is the use of advanced optical microscopy for the detection of fluorescently labeled epigenetic marks on long, extended DNA molecules. Here we will discuss recent single-molecule studies for the mapping of chromatin composition and epigenetic DNA modifications, such as DNA methylation.
Magnesium alloys are emerging as promising alternatives to traditional orthopedic implant materials thanks to their biodegradability, biocompatibility, and impressive mechanical characteristics. However, their rapid in-vivo degradation presents challenges, notably in upholding mechanical integrity over time. This study investigates the impact of high-temperature thermal processing on the mechanical and degradation attributes of a lean Mg-Zn-Ca-Mn alloy, ZX10. Utilizing rapid, cost-efficient characterization methods like X-ray diffraction and optical microscopy, we swiftly examine microstructural changes post-thermal treatment. Employing Pearson correlation coefficient analysis, we unveil the relationship between microstructural properties and critical targets (properties): hardness and corrosion resistance. Additionally, leveraging the least absolute shrinkage and selection operator (LASSO), we pinpoint the dominant microstructural factors among closely correlated variables. Our findings underscore the significant role of grain size refinement in strengthening and the predominance of the ternary Ca2Mg6Zn3 phase in corrosion behavior. This suggests that achieving an optimal blend of strength and corrosion resistance is attainable through fine grains and reduced concentration of ternary phases. This thorough investigation furnishes valuable insights into the intricate interplay of processing, structure, and properties in magnesium alloys, thereby advancing the development of superior biodegradable implant materials.
Abstract Magnesium alloys are increasingly recognized as promising materials for biomedical implants due to their low density, biocompatibility, and favorable mechanical properties. However, achieving a balance between mechanical strength and bio-corrosion resistance remains a critical challenge. This study evaluates the effects of three thermomechanical processing techniques — extrusion (EXT), Equal Channel Angular Pressing (ECAP), and ECAP followed by low-temperature annealing at 150°C for 10 hours (ECAP-A) — on the microstructure, mechanical properties, and bio-corrosion behavior of the ZX10 magnesium alloy. EXT resulted in a coarse, elongated grain structure, increased volume fraction of Mg2Ca particles, and moderate mechanical and corrosion performance. ECAP lowered the volume fraction of Mg2Ca particles and significantly refined the grain structure, and increased dislocation density, improving hardness by 80%, yield strength, and ductility. However, the corrosion rate doubled due to the high dislocation density. Post-ECAP annealing (ECAP-A) mitigated this limitation, reducing the corrosion rate to 1.50 mm/year while maintaining a high yield strength (>200 MPa). This improvement was driven by a uniform distribution of the Ca2Mg6Zn3 phase, a further reduction of the Mg2Ca phase, and decreased dislocation density. These findings demonstrate that ECAP, followed by annealing, optimally balances mechanical performance and bio-corrosion resistance, making the ZX10 magnesium alloy a promising candidate for biodegradable implant applications
Several types of additives that contain transition metals can promote the cross-linking of poly(vinyl chloride) (PVC) by a mechanism that apparently involves reductive coupling of the polymer chains. In solid PVC, the cross-linking occurs at 200 °C, and model-compound experiments show that it can be ascribed to the preferential reductive coupling of allylic chloride structures when the coupling agent is Cu(0). However, the concurrent coupling of other chloride moieties has not been entirely ruled out. The evidence for reductive coupling consists of rapid gel formation accompanied by substantial reductions (or minor changes) in the rates of total mass loss (as determined by thermogravimetric analysis), CC formation (as observed by Fourier transform IR spectroscopy), and HCl evolution (as determined by acid−base titrimetry). Additives that promote the coupling process are sources of a zero- or low-valent metal upon pyrolysis. These additives include a number of transition-metal carbonyls, divalent formates or oxalates of the late transition metals, simple Cu(I) halides, and various complexes of Cu(I) containing phosphites or other ligands. Since the reductive coupling agents tend to have low acidities, they are not expected to promote the cationic cracking of char. Thus they are potentially attractive as replacements for the PVC smoke suppressants that stimulate cross-linking by acting as Lewis acids.
