Chromic and dynamic: soft crystals of platinum(II) complexes pave the way for multi-responsive materials.

The development of smart, stimuli-responsive materials has received increased attention in the past decade for their applications as sensing technologies. This commentary discusses a timely topical review by Kato [(2024). IUCrJ, 11, 442-452] on the fabrication of multi-stimuli responsive crystals comprised of luminescent platinum(II) complexes, which exhibit intriguing chromic phenomena in response to stimuli.

Multi-Catalytic Metal-Based Homogeneous-Heterogeneous Systems in Organic Chemistry.

The combination of metal-based homogeneous and heterogeneous catalysts in the same reaction media is a powerful, yet relatively unexplored approach in organic chemistry. This strategy can address important limitations associated with purely homogeneous or heterogeneous catalysis such as the incompatibility of different catalytic species in solution, or the limited tunability of solid catalysts, respectively. Moreover, the facile reusability of the solid catalyst, contributes to increase the overall sustainability of the process. As a result, this semi-heterogeneous multi-catalytic approach has unlocked significant advances in organic chemistry, improving existing reactions and even enabling the discovery of novel transformations, exemplified by the formal alkane metathesis. This concept article aims to showcase the benefits of this strategy through exploration of diverse relevant examples from the literature, hoping to spur research on new metal-based homogeneous-heterogeneous catalyst combinations that will result in reactivity challenging to achieve by conventional homogeneous or heterogeneous catalysis alone.

A Symmetric Form of the Clausius Statement of the Second Law of Thermodynamics.

Bridgman once reflected on thermodynamics that the laws of thermodynamics were formulated in their present form by the great founders of thermodynamics, Kelvin and Clausius, before all the essential physical facts were in, and there has been no adequate reexamination of the fundamentals since. Thermodynamics still has unknown possibilities waiting to be explored. This paper begins with a brief review of Clausius's work on the second law of thermodynamics and a reassessment of the content of Clausius's statement. The review tells that what Clausius originally referred to as the second law of thermodynamics was, in fact, the theorem of equivalence of transformations (TET) in a reversible cycle. On this basis, a new symmetric form of Clausius's TET is proposed. This theorem says that the two transformations, i.e., the transformation of heat to work and the transformation of work from high pressure to low pressure, should be equivalent in a reversible work-to-heat cycle. New thermodynamic cyclic laws are developed on the basis of the cycle with two work reservoirs (two pressures), which enriches the fundamental of the second law of thermodynamics.

Transition-Metal-Catalyzed Transformations for the Synthesis of Marine Drugs.

Transition metal catalysis has contributed to the discovery of novel methodologies and the preparation of natural products, as well as new chances to increase the chemical space in drug discovery programs. In the case of marine drugs, this strategy has been used to achieve selective, sustainable and efficient transformations, which cannot be obtained otherwise. In this perspective, we aim to showcase how a variety of transition metals have provided fruitful couplings in a wide variety of marine drug-like scaffolds over the past few years, by accelerating the production of these valuable molecules.

Polyelectrolyte-Mediated Modulation of Spatial Internal Stresses of Hydrogels for Complex 3D Actuators.

Hydrogel actuators with complex 3D initial shapes show numerous important applications, but it remains challenging to fabricate such actuators. This article describes a polyelectrolyte-based strategy for modulating small-scale internal stresses within hydrogels to construct complex actuators with tailored 3D initial shapes. Introducing polyelectrolytes into precursor solutions significantly enhances the volume shrinkage of hydrogel networks during polymerization, allowing us to modulate internal stresses. Photopolymerization of these polyelectrolyte-containing solutions through a mask produces mechanically strong hydrogel sheets with large patterned internal stresses. Consequently, these hydrogel sheets attain complex 3D initial shapes at equilibrium, in contrast to the planar initial configuration of 2D actuators. We demonstrate that these 3D actuators can reversibly transform into other 3D shapes (i.e., 3D-to-3D shape transformations) in response to external stimuli. Additionally, we develop a predictive model based on the Flory-Rehner theory to analyze the polyelectrolyte-mediated shrinking behaviors of hydrogel networks during polymerization, allowing precise modulation of shrinkage and internal stress. This polyelectrolyte-boosted shrinking mechanism paves a route to the fabrication of high-performance 3D hydrogel actuators.

Innovative governance for transformative energy policy in sub-Saharan Africa after COVID-19: Green pathways in Egypt, Nigeria, and South Africa.

Learning from innovations that fail is imperative for innovations that succeed. The theoretical underpinnings for this innovative framing are reflexivity, transformative unlearning, and intelligent failure. This framework proposes a definition of "transformative governance" as governance that creates structural equities. Governments rebuilding their economies after the COVID-19 pandemic seek equitable green transformations; that are gendered, structural, and sustainable, learning from the implemented gender-sensitive responses (hereafter referred to as policy innovations). This paper argues that transformative practices, beliefs, values, assumptions, policies, and systematic learnings are complementary to post-crisis transformations. The aim is to promote systematic learnings from innovation governance failure regarding energy policy through the analysis of COVID-19 practices and the unlearning of policy innovation beliefs, values, and assumptions that are not transformative. I ask: how gender-equitable, structurally equitable, and green-transformative were the COVID-19 policy innovations? The study's approach is qualitative and situated within the constructivist research paradigm. It uses reflexive thematic analysis combined with innovative coded policy narrative and a transformative index-matching technique, to identify the gap within transformative interventions. The study included 58 policy innovations (n = 58) collected from the UNDP, KPMG, government reports, and news flashes from the three most populous nations in sub-Sahara Africa: Egypt, Nigeria, and South Africa. The study found that policy innovations were inequitable in terms of gender, structure, and sustainability whereas the derived transformative pathways are equitable and gender-transformative, structurally transformative, and green-transformative. The rationales behind a transformative approach to policy reflect the systemic failures across key areas: market dynamics, research and development, and green transformation. Policy innovators can align transformative pathways for innovative governance that implements transformative energy policy. To address the needs of multiple fragile and vulnerable identities, the derived post-pandemic framework is an intersectional plan with 10 policy learning pillars. The plan includes local energy transformation and reinforcement of energy justice components, such as the localization of the energy industry, community power, and social norms, including Ubuntu, which translates to "I am because we are." Reengagement in global supply chains requires South-South trade relations to be restrategized.

The Influence of Cyclic Thermal Shocks at High Temperatures on the Microstructure, Hardness and Thermal Diffusivity of the Rene 41 Alloy.

The precipitation-hardenable nickel-based superalloy Rene 41 exhibits remarkable mechanical characteristics and high corrosion resistance at high temperatures, properties that allow it to be used in high-end applications. This research paper presents findings on the influence of thermal shocks on its microstructure, hardness, and thermal diffusivity at temperatures between 700 and 1000 °C. Solar energy was used for cyclic thermal shock tests. The samples were characterized using microhardness measurements, optical microscopic analysis, scanning electron microscopy coupled with EDS elemental chemical analysis, X-ray diffraction, and flash thermal diffusivity measurements. Structural transformations and the variation of properties were observed with an increase in the number of shocks applied at the same temperature and with temperature variation for the same number of thermal shocks.

Modeling of Yb:YAG Laser Beam Caustics and Thermal Phenomena in Laser-Arc Hybrid Welding Process with Phase Transformations in the Solid State.

This paper focuses on the mathematical and numerical modeling of the electric arc + laser beam welding (HLAW) process using an innovative model of the Yb:YAG laser heat source. Laser energy distribution is measured experimentally using a UFF100 analyzer. The results of experimental research, including the beam profile and energetic characteristics of an electric arc, are used in the model. The laser beam description is based on geostatistical kriging interpolation, whereas the electric arc is modeled using Goldak's distribution. Hybrid heat source models are used in numerical algorithms to analyze physical phenomena occurring in the laser-arc hybrid welding process. Thermal phenomena with fluid flow in the fusion zone (FZ) are described by continuum conservation equations. The kinetics of phase transformations in the solid state are determined using Johnson-Mehl-Avrami (JMA) and Koistinen-Marburger (KM) equations. A continuous cooling transformation (CCT) diagram is determined using interpolation functions and experimental research. An experimental dilatometric analysis for the chosen cooling rates is performed to define the start and final temperatures as well as the start and final times of phase transformations. Computer simulations of butt-welding of S355 steel are executed to describe temperature and melted material velocity profiles. The predicted FZ and heat-affected zone (HAZ) are compared to cross-sections of hybrid welded joints, performed using different laser beam focusing. The obtained results confirm the significant influence of the power distribution of the heat source and the laser beam focusing point on the temperature distribution and the characteristic zones of the joint.

Double-duty isomerases: a case study of isomerization-coupled enzymatic catalysis.

Enzymes can usually be unambiguously assigned to one of seven classes specifying the basic chemistry of their catalyzed reactions. Less frequently, two or more reaction classes are catalyzed by a single enzyme within one active site. Two examples are an isomerohydrolase and an isomero-oxygenase that catalyze isomerization-coupled reactions crucial for production of vision-supporting 11-cis-retinoids. In these enzymes, isomerization is obligately paired and mechanistically intertwined with a second reaction class. A handful of other enzymes carrying out similarly coupled isomerization reactions have been described, some of which have been subjected to detailed structure-function analyses. Herein we review these rarefied enzymes, focusing on the mechanistic and structural basis of their reaction coupling with the goal of revealing catalytic commonalities.

Inverting social innovation to transform health system responses to climate change adaptation and mitigation in the global south.

Systems thinking is aimed at understanding and solving complex problems that cut across sectors, an approach that requires accurate, timely, and multisectoral data. Citizen-driven big data can advance systems thinking, considering the widespread use of digital devices. Using digital platforms, data from these devices can transform health systems to predict and prevent global health crises and respond rapidly to emerging crises by providing citizens with real-time support. For example, citizens can obtain real-time support to help with public health risks via a digital app, which can predict evolving risks. These big data can be aggregated and visualized on digital dashboards, which can provide decision-makers with advanced data analytics to facilitate jurisdiction-level rapid responses to evolving climate change impacts (e.g., direct public health crisis communication). In the context of climate change, digital platforms can strengthen rapid responses by integrating information across systems (e.g., food, health, and social services) via citizen big data. More importantly, these big data can be used for rapid decision-making,a paradigm-changing approach that can invert social innovation, which we define as co-conceptualizing societal solutions with vulnerable communities to improve economic development with a focus on community wellbeing. However, to foster equitable and inclusive digital partnerships that invert social innovation, it is critical to avoid top-down approaches that sometimes result when researchers in the Global North and South collaborate. Equitable Global South-North partnerships can be built by combining digital citizen science and community-based participatory research to ethically leverage citizen-driven big data for rapid responses across international jurisdictions.

Understanding the Correlation between Electrochemical Performance and Operating Mechanism of a Co-free Layered-Spinel Composite Cathode for Na-Ion Batteries.

Compositing different crystal structures of layered transition metal oxides (LTMOs) is an emerging strategy to improve the electrochemical performance of LTMOs in sodium-ion batteries. Herein, a cobalt-free P2/P3-layered spinel composite, P2/P3-LS-Na1/2Mn2/3Ni1/6Fe1/6O2 (LS-NMNF), is synthesized, and the synergistic effects from the P2/P3 and spinel phases were investigated. The material delivers an initial discharge capacity of 143 mAh g-1 in the voltage range of 1.5-4.0 V and displays a capacity retention of 73% at the 50th cycle. The material shows a discharge capacity of 72 mAh g-1 at 5C. This superior rate performance by the material could be by virtue of the increased electronic conductivity contribution of the incorporated spinel phase. The charge compensation mechanism of the material is investigated by in operando X-ray absorption spectroscopy (in a voltage range of 1.5-4.5 V vs Na+/Na), which revealed the contribution of all transition metals toward the generated capacity. The crystal structure evolution of each phase during electrochemical cycling was analyzed by in operando X-ray diffraction. Unlike in the case of many reported P2/P3 composite cathode materials and spinel-incorporated cobalt-containing P2/P3 composites, the formation of a P'2 phase at the end of discharge is absent here.

Laser-Printed Photoanode: Femtosecond Laser-Induced Crystalline Phase Transformation of WO3 Nanorods for Space-Efficient and Flexible Thin-Film Solar Water-Splitting Cells.

Despite its potential for clean hydrogen harvesting, photoelectrochemical (PEC) water-splitting cells face challenges in commercialization, particularly related its harvesting performance and productivity at an industrial scale. Herein, a facile fabrication method of flexible thin-film photoanode for PEC water-splitting to overcome these limitations, based on laser processing technologies, is proposed. Laser-induced graphene, a carbon structure produced through direct laser writing carbonization (DLWC), plays a dual role: a flexible and stable current collector and a substrate for the hydrothermal synthesis of tungsten trioxide (WO3) nanorods (NRs). To facilitate water-splitting, a femtosecond-pulsed laser (fs laser) is focused on the WO3 NRs, converting their crystalline phase from pristine orthorhombic to monoclinic structure without thermal damage. With NiFe layered double hydroxide (LDH) catalyst, the flexible thin-film photoanode exhibits good PEC performance (1.46 mA cm-2 at 1.23 VRHE) and retains ≈90% of its performance after 3000 bending cycles. With its excellent mechanical properties, the flexible photoanode can be operated in various shapes with different curvatures, enabling space-efficient PEC water-splitting by loading larger photoanode within a given space. This study is expected to contribute to the advancement of large-scale solar water-splitting cells, introducing a new approach to enhance H2/O2 production and expand its application range.

Moving Object Detection in Freely Moving Camera via Global Motion Compensation and Local Spatial Information Fusion.

Motion object detection (MOD) with freely moving cameras is a challenging task in computer vision. To extract moving objects, most studies have focused on the difference in motion features between foreground and background, which works well for dynamic scenes with relatively regular movements and variations. However, abrupt illumination changes and occlusions often occur in real-world scenes, and the camera may also pan, tilt, rotate, and jitter, etc., resulting in local irregular variations and global discontinuities in motion features. Such complex and changing scenes bring great difficulty in detecting moving objects. To solve this problem, this paper proposes a new MOD method that effectively leverages local and global visual information for foreground/background segmentation. Specifically, on the global side, to support a wider range of camera motion, the relative inter-frame transformations are optimized to absolute transformations referenced to intermediate frames in a global form after enriching the inter-frame matching pairs. The global transformation is fine-tuned using the spatial transformer network (STN). On the local side, to address the problem of dynamic background scenes, foreground object detection is optimized by utilizing the pixel differences between the current frame and the local background model, as well as the consistency of local spatial variations. Then, the spatial information is combined using optical flow segmentation methods, enhancing the precision of the object information. The experimental results show that our method achieves a detection accuracy improvement of over 1.5% compared with the state-of-the-art methods on the datasets of CDNET2014, FBMS-59, and CBD. It demonstrates significant effectiveness in challenging scenarios such as shadows, abrupt changes in illumination, camera jitter, occlusion, and moving backgrounds.

Photoinduced bidirectional mesophase transition in vesicles containing azobenzene amphiphiles.

The functionality and efficiency of proteins within a biological membrane are highly dependent on both the membrane lipid composition and the physiochemical properties of the solution. Lipid mesophases are directly influenced by changes in temperature, pH, water content or due to individual properties of single lipids such as photoswitchability. In this work, we were able to induce light- and temperature-driven mesophase transitions in a model membrane system containing a mixture of 1,2-dipalmitoyl-phosphatidylcholine phospholipids and azobenzene amphiphiles. We observed reversible and reproducible transitions between the lamellar and Pn3m cubic phase after illuminating the sample for 5 min with light of 365 and 455 nm wavelengths, respectively, to switch between the cis and trans states of the azobenzene N=N double bond. These light-controlled mesophase transitions were found for mixed complexes with up to 20% content of the photosensitive molecule and at temperatures below the gel-to-liquid crystalline phase transition temperature of 33°C. Our results demonstrate the potential to design bespoke model systems to study the response of membrane lipids and proteins upon changes in mesophase without altering the environment and thus provide a possible basis for drug delivery systems.

Heterogeneous Porous Synergistic Photocatalysts for Organic Transformations.

Recent interest has surged in using heterogeneous carriers to boost synergistic photocatalysis for organic transformations. Heterogeneous catalysts not only facilitate synergistic enhancement of distinct catalytic centers compared to their homogeneous counterparts, but also allow for the easy recovery and reuse of catalysts. This mini-review summarizes recent advancements in developing heterogeneous carriers, including metal-organic frameworks, covalent-organic frameworks, porous organic polymers, and others, for synergistic catalytic reactions. The advantages of porous materials in heterogeneous catalysis originate from their ability to provide a high surface area, facilitate enhanced mass transport, offer a tunable chemical structure, ensure the stability of active species, and enable easy recovery and reuse of catalysts. Both photosensitizers and catalysts can be intricately incorporated into suitable porous carriers to create heterogeneous dual photocatalysts for organic transformations. Notably, experimental evidence from reported cases has shown that the catalytic efficacy of heterogeneous catalysts often surpasses that of their homogeneous analogues. This enhanced performance is attributed to the proximity and confinement effects provided by the porous nature of the carriers. It is expected that porous carriers will provide a versatile platform for integrating diverse catalysts, thus exhibiting superior performance across a range of organic transformations and appealing prospect for industrial applications.

Bispidine Based Hg(II) 1D Coordination Polymers of Helical Topology: Stability, Selective Adsorption and 1D to 2D Dimensionality Change Via SC-to-SC Transformation.

Bispidine based Hg(II) coordination polymers of helical topology CP-MeOH and CP-EtOH are almost isostructural (they mainly differ for the solvent included in their lattice and by a small % in unit cell parameters) but they differ for everything else: i) their intrinsic stability, ii) their ability to adsorb solvents upon prior evacuation, iii) their accessible structural transformations. In particular, one of the two starting materials, once evacuated, is capable to adsorb methanol from atmospheres containing binary and ternary mixtures of volatile organic compounds (MeOH, CHCl3 and EtOH) under ambient conditions (25 °C, 1 atm) and with a marked selectivity. The other one is not, but undergoes a 1D to 2D dimensionality change which can be monitored in situ by SC-XRD through a SC-to-SC process.

Raman spectroscopy of thermo- and laser-induced transformations of gouache paint layer of copper phthalocyanine blue.

Methods to control polymorphic modifications of phthalocyanines using optical (laser) radiation and possible photoinduced transformations of polymorphs are of practical interest in problems of identification and attribution of paintings, laser (micro)sampling, and the development of phthalocyanine structures for technical applications in optics, optoelectronics, and medicine. In this work, we compare the thermal and laser-induced changes of a gouache paint layer based on copper phthalocyanine (CuPc) PB15. The thermally induced color changes of the paint layer are quantified using the CIE Lab D65/10 color space. (Nano)rods formed in the paint layer when the sample is heated to 450°C at normal pressure without humidity control are studied using absorption spectroscopy, Raman microspectroscopy, and scanning electron microscopy. It is shown that the formation of (nano)rods is related to the αâ†’ß polymorph transition of CuPc. Low-frequency markers of the CuPc ß-polymorph are revealed in the Raman spectra. For the sample containing (nano)rods, the a* color coordinate substantially increases (by about 30 units), whereas the L* and b* coordinates remain almost unchanged. Irradiation with a single nanosecond laser pulse at a wavelength of 532 nm leads to the laser ablation of the paint layer at fluences exceeding a threshold level of about 3 J/cm2. Irradiation at fluences of greater than 0.5 J/cm2, but lower than the ablation threshold leads to color change of the paint layer due to the α→ε transition of CuPc. Similar transformations are observed at the periphery of and inside ablation crater.

A comparison of the isostructural [Co(NH3)5NO2]XNO3 and [Co(NH3)5ONO]XNO3, X = Cl- or Br- in relation to nitro-nitrito linkage isomerization and photomechanical effects.

A new photoactive cobalt coordination compound, [Co(NH3)5NO2]BrNO3 (I), was obtained. Its crystal structure was shown to be isostructural with previously known [Co(NH3)5NO2]ClNO3 (II) for which linkage isomerization accompanied with mechanical response of the crystal has been already reported. Single crystals of I are transformed into nitrito isomer [Co(NH3)5ONO]BrNO3 (III) on irradiation with blue light (λ = 465 nm) without being destroyed. The crystal structure of III was also solved using single-crystal X-ray diffraction and compared with previously known [Co(NH3)5ONO]ClNO3 (IV). A detailed comparison of the structures of I, II, III and IV, including unit-cell parameters, the distribution of free space (in particular, reaction cavities around the nitro ligand), the lengths of hydrogen bonds, coordination and Voronoi-Dirichlet polyhedra has been performed. Single-crystal X-ray diffraction data were complemented with IR spectra. The effect of the replacement of Cl- by Br- on the crystal structure and on the nitro-nitrito photoisomerization is discussed.

Chiral Ligand-Concentration Mediating Asymmetric Transformations of Silver Nanoclusters: NIR-II Circularly Polarized Phosphorescence Lighting.

Near infrared (NIR) emitter with circularly polarized phosphorescence (CPP), known as NIR CPP, has emerged as a key part in the research of cutting-edge luminescent materials. However, it remains a challenge to obtain nanoclusters with NIR CPP activity. Here, we propose an asymmetric transformation approach to efficiently synthesize two pairs of chiral silver nanoclusters (R/S-Ag29 and R/S-Ag16) using an achiral Ag10 nanocluster as starting material in the presence of different concentration chiral inducer (R/S)-1,1'-binaphthyl-2,2'-diyl hydrogenphosphate (R/S-BNP). R/S-Ag29, formed in the low-concentration R/S-BNP, exhibits a unique kernel-shell structure consisting of a distorted Ag13 icosahedron and an integrated cage-like organometallic shell with a C3 symmetry, and possesses a superatomic 6-electron configuration (1S2|1P4). By contrast, R/S-Ag16, formed in the high-concentration R/S-BNP, features a sandwich-like pentagram with AgI-pure kernel. Profiting from the hierarchically chiral structures and superatomic kernel-dominated phosphorescence, R/S-Ag29 exhibits infrequent CPP activity in the second near-infrared (975 nm) region, being the first instance of NIR-II CPP observed among CPL-active metal nanoclusters. This study presents a new approach to reduce the difficulty of de novo synthesis for chiral silver nanomaterials, and facilitates the design of CPP-active superatomic nanoclusters in NIR region.

Mercury abatement in the environment: Insights from industrial emissions and fates in the environment.

Mercury's neurotoxic effects have prompted the development of advanced control and remediation methods to meet stringent measures for industries with high-mercury feedstocks. Industries with significant Hg emissions, including artisanal and small-scale gold mining (ASGM)-789.2 Mg year-1, coal combustion-564.1 Mg year-1, waste combustion-316.1 Mg year-1, cement production-224.5 Mg year-1, and non-ferrous metals smelting-204.1 Mg year-1, use oxidants and adsorbents capture Hg from waste streams. Oxidizing agents such as O3, Cl2, HCl, CaBr2, CaCl2, and NH4Cl oxidize Hg0 to Hg2+ for easier adsorption. To functionalize adsorbents, carbonaceous ones use S, SO2, and Na2S, metal-based adsorbents use dimercaprol, and polymer-based adsorbents are grafted with acrylonitrile and hydroxylamine hydrochloride. Adsorption capacities span 0.2-85.6 mg g-1 for carbonaceous, 0.5-14.8 mg g-1 for metal-based, and 168.1-1216 mg g-1 for polymer-based adsorbents. Assessing Hg contamination in soils and sediments uses bioindicators and stable isotopes. Remediation approaches include heat treatment, chemical stabilization and immobilization, and phytoremediation techniques when contamination exceeds thresholds. Achieving a substantially Hg-free ecosystem remains a formidable challenge, chiefly due to the ASGM industry, policy gaps, and Hg persistence. Nevertheless, improvements in adsorbent technologies hold potential.