Thermal Fragmentation Research Articles

Distribution characteristics of trace elements (As/Cr/Mn/Cu/Pb) in the thermal fragmentation and strengthening fragmentation processes of low-rank coal with high sulfur content

The thermal fragmentation of low-rank coal had been proven to be a new way of desulfurization for char with coarse-size. However, whether harmful trace elements (HTEs) could be effectively removed in coarse-size char by thermal fragmentation action demand for further study. Two high-sulfur low-rank coals were used to explore the distribution behavior of As, Cr, Cu, Mn, and Pb in thermal fragmentation char with different particle sizes obtained by the fixed-bed and rotary kiln pyrolysis. Combined with the occurrence forms of HTEs in raw coal and volatilization characteristics of HTEs obtained by thermodynamic simulation software, the distribution of HTEs in thermal fragmentation char was analyzed. The effectiveness of thermal fragmentation of HTEs components in fixed-bed pyrolysis was reliant on high temperatures, with poor distribution resulting in less than 20 % of As, Cu, and Pb components being allocated to pulverization char. The thermal fragmentation of Cu components in disulfide form, was severely hindered by the binding effect of metaplast. In contrast, rotary kiln pyrolysis facilitated a greater distribution proportion of HTEs components into pulverization char at lower temperatures. Under optimal conditions, the distribution of As, Pb, and Cr into pulverization char surpassed 70 %. The strengthening thermal fragmentation in the rotary kiln reduce the binding effects, effectively increasing the distribution of copper-rich components into pulverized char.

ATOMS: ALMA three-millimetre observations of massive star-forming regions–XVII. High-mass star-formation through a large-scale collapse in IRAS 15394-5358

ABSTRACT Hub-filament systems are considered as natural sites for high-mass star formation. Kinematic analysis of the surroundings of hub-filaments is essential to better understand high-mass star formation within such systems. In this work, we present a detailed study of the massive Galactic protocluster IRAS 15394$-$5358, using continuum and molecular line data from the ALMA three-millimetre observations of massive star-forming regions (ATOMS) survey. The 3 mm dust continuum map reveals the fragmentation of the massive ($\rm M=843~{\rm M}_{\odot }$) clump into six cores. The core C-1A is the largest (radius = 0.04 pc), the most massive ($\rm M=157~{\rm M}_{\odot }$), and lies within the dense central region, along with two smaller cores ($\rm M=7~and~3~{\rm M}_{\odot }$). The fragmentation process is consistent with the thermal Jeans fragmentation mechanism and virial analysis shows that all the cores have small virial parameter values ($\rm \alpha _{vir}\lt \lt 2$), suggesting that the cores are gravitationally bound. The mass versus radius relation indicates that three cores can potentially form at least a single massive star. The integrated intensity map of $\rm H^{13}CO^{+}$ shows that the massive clump is associated with a hub-filament system, where the central hub is linked with four filaments. A sharp velocity gradient is observed towards the hub, suggesting a global collapse where the filaments are actively feeding the hub. We discuss the role of global collapse and the possible driving mechanisms for the massive star formation activity in the protocluster.

Digging into the Interior of Hot Cores with ALMA (DIHCA). IV. Fragmentation in High-mass Star-forming Clumps

Fragmentation contributes to the formation and evolution of stars. Observationally, high-mass stars are known to form multiple-star systems, preferentially in cluster environments. Theoretically, Jeans instability has been suggested to determine characteristic fragmentation scales, and thermal or turbulent motion in the parental gas clump mainly contributes to the instability. To search for such a characteristic fragmentation scale, we have analyzed Atacama Large Millimeter/submillimeter Array (ALMA) 1.33 mm continuum observations toward 30 high-mass star-forming clumps taken by the Digging into the Interior of Hot Cores with ALMA survey. We have identified 573 cores using the dendrogram algorithm and measured the separation of cores by using the Minimum Spanning Tree technique. The core separation corrected by projection effects has a distribution peaked around 5800 au. In order to remove biases produced by different distances and sensitivities, we further smooth the images to a common physical scale and perform completeness tests. Our careful analysis finds a characteristic fragmentation scale of ∼7000 au, comparable to the thermal Jeans length of the clumps. We conclude that thermal Jeans fragmentation plays a dominant role in determining the clump fragmentation in high-mass star-forming regions, without the need to invoke turbulent Jeans fragmentation.

Experimental study on fragmentation characteristics of molten stainless steel discharged into liquid Lead-Bismuth Eutectic pool

The LFR is a candidate for the Generation-IV nuclear systems, where the process of MFCI differs from that occurred in LWRs and SFRs. In the absence of experimental study and widely applied theoretical models for LFRs, experiments on the interaction between molten SS and liquid LBE are conducted in this study under eight conditions. The morphological characteristics and fragment sizes of the products are analyzed based on the hydrodynamic effect parameter (We) and thermal effect parameter (Tic). Simplified thermal fragmentation models are established, where the innermost layer of the solidified shell is subjected to the maximum tangential compressive stress, while the outermost layer is subjected to the maximum tangential tensile stress. As the shell thickness increases, the total tangential stress of the outermost layer decreases. The fragmentation will occur when the maximum tangential stress on the shell exceeds the shell tensile strength.

A comprehensive metric scheme for characterizing the heterogeneity of urban thermal landscapes: A case study of 14-year evaluation in Beijing

Urbanization has affected land surface temperature (LST) significantly. The spatial average of LST is widely applied to evaluate urban heat islands (UHI), but a simple comparison of mean temperature is insufficient to evaluate the heterogeneity of LST and the effectiveness of urban heat mitigation strategies. This study took the spatial distribution of LST as the thermal landscape and firstly employed 3D landscape metrics to analyze its spatial heterogeneity. To perform collaborative analysis with UHI, the urban–rural differences of landscape metrics were defined as thermal metric islands (TMI). Significant UHI and TMI were revealed by temperature amplitude, aggregation, and complexity parameters, indicating higher temperature fluctuation and fragmentation in urban regions. Before 2007, the standard deviation of thermal surface, landscape fragmentation, and shape irregularity increased significantly, particularly in the suburbs. Later, benefiting from the Summer Olympic Games, the temperature fluctuation, fragmentation, and shape complexity decreased obviously, and UHI intensity hit the lowest. Both UHI intensities and TMI increased after 2010, and various metrics suggest that maximum temperatures, landscape fragmentation, and shape complexity declined over most of the district, even as the mean temperatures increased. This study concludes that urban temperatures have risen at a higher rate than suburban areas, but the thermal landscape composition and configuration have changed more dramatically in rural areas.

Thermal habitat fragmentation in stratified lakes induces resource waves that brook charr track across seasons

The spatial configuration of thermal habitats constrains the thermoregulatory performance of ectotherms. Thermal landscapes also vary through time, which is particularly relevant in seasonal environments such as temperate lakes. Indeed, elevated temperatures in the epilimnion of dimictic lakes during summer could substantially reduce the use of this habitat by cold‐stenothermic fish during the stratified period. The main objective of this study was to evaluate whether thermal habitat fragmentation in stratified lakes modulates accessibility to resources that brook charr, Salvelinus fontinalis, which is a mobile consumer, can track across seasons. More specifically, we hypothesize that reduced access to the littoral habitat during summer enhances foraging opportunities in this habitat during winter. We used an automatic acoustic telemetry system offering full coverage of the lake to continuously record brook charr locations across seasons, and we estimated zoobenthos abundances in the littoral habitat using image processing and semi‐automatic classification. While brook charr concentrate in the metalimnion of the pelagic habitat in summer, most individuals in winter shift to a shallow bay that is unexploited in summer due to thermal constraints. In this habitat, zoobenthos abundance is more than twice as high at the end of the summer compared to littoral habitats close to the thermal refuge in the pelagic habitat. Surprisingly, brook charr showed strong within‐lake site fidelity between two consecutive summers, which suggests that spatial memory could be a key driver of seasonal habitat use in this lacustrine population. Overall, our results suggest that thermal barriers create fragmentation between littoral and pelagic habitats that in turn produces resource opportunities that brook charr can track across seasons.

Chemical Analysis of Exhaled Vape Emissions: Unraveling the Complexities of Humectant Fragmentation in a Human Trial Study.

Electronic cigarette smoking (or vaping) is on the rise, presenting questions about the effects of secondhand exposure. The chemical composition of vape emissions was examined in the exhaled breath of eight human volunteers with the high chemical specificity of complementary online and offline techniques. Our study is the first to take multiple exhaled puff measurements from human participants and compare volatile organic compound (VOC) concentrations between two commonly used methods, proton-transfer-reaction time-of-flight mass spectrometry (PTR-ToF-MS) and gas chromatography (GC). Five flavor profile groups were selected for this study, but flavor compounds were not observed as the main contributors to the PTR-ToF-MS signal. Instead, the PTR-ToF-MS mass spectra were overwhelmed by e-liquid thermal decomposition and fragmentation products, which masked other observations regarding flavorings and other potentially toxic species associated with secondhand vape exposure. Compared to the PTR-ToF-MS, GC measurements reported significantly different VOC concentrations, usually below those from PTR-ToF-MS. Consequently, PTR-ToF-MS mass spectra should be interpreted with caution when reporting quantitative results in vaping studies, such as doses of inhaled VOCs. Nevertheless, the online PTR-ToF-MS analysis can provide valuable qualitative information by comparing relative VOCs in back-to-back trials. For example, by comparing the mass spectra of exhaled air with those of direct puffs, we can conclude that harmful VOCs present in the vape emissions are largely absorbed by the participants, including large fractions of nicotine.

Analysis of thermomechanical coupled accelerated aging of HTPB propellants

AbstractThis study employed macroscopic uniaxial compression tests at low and medium strain rates, coupled with microscopic electron microscopy, to extensively analyse the impact of thermomechanical coupled aging on the accelerated aging of Hydroxyl‐terminated Polybutadiene (HTPB) propellants, contrasting it with the effects of isolated factors such as heat and dynamic reciprocating force. Results indicate that at various environmental temperatures (323 K, 343 K, and 363 K), thermomechanical coupled aging more significantly affects HTPB propellants than isolated factors. This effect is macroscopically evident in increased ease of deformation, permanent deformation during aging, continual increase in dissipated energy, and a decrease in average stress and ultimate strain post‐aging. Microscopically, the effect predominantly arises from the interplay between matrix thermal degradation and particle fragmentation, which rapidly accumulate and substantially impact the material's macroscopic mechanical properties. Furthermore, as the aging temperature rises, the alterations in both macroscopic mechanical properties and microscopic morphology of HTPB propellants become more pronounced. However, overly high temperatures may swiftly result in substantial material performance deterioration. Consequently, while elevating temperature effectively accelerates thermomechanical aging, the potential adverse effects on material performance must be judiciously considered. This underscores the necessity of balancing temperature regulation with aging efficiency enhancement in HTPB propellants to ensure effective control and quantitative assessment of the aging process, while minimizing material degradation.

The ALMA Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES). XI. Statistical Study of Early Fragmentation

Fragmentation during the early stages of high-mass star formation is crucial for understanding the formation of high-mass clusters. We investigated fragmentation within 39 high-mass star-forming clumps as part of the Atacama Large Millimeter/submillimeter Array Survey of 70 μm Dark High-mass Clumps in Early Stages (ASHES) survey. Considering projection effects, we have estimated core separations for 839 cores identified from the continuum emission and found mean values between 0.08 and 0.32 pc within each clump. We find compatibility of the observed core separations and masses with the thermal Jeans length and mass, respectively. We also present subclump structures revealed by the 7 m array continuum emission. Comparison of the Jeans parameters using clump and subclump densities with the separation and masses of gravitationally bound cores suggests that they can be explained by clump fragmentation, implying the simultaneous formation of subclumps and cores within rather than a step-by-step hierarchical fragmentation. The number of cores in each clump positively correlates with the clump surface density and the number expected from the thermal Jeans fragmentation. We also find that the higher the fraction of protostellar cores, the larger the dynamic range of the core mass, implying that the cores are growing in mass as the clump evolves. The ASHES sample exhibits various fragmentation patterns: aligned, scattered, clustered, and subclustered. Using the Q -parameter, which can help distinguish between centrally condensed and subclustered spatial core distributions, we finally find that in the early evolutionary stages of high-mass star formation, cores tend to follow a subclustered distribution.

Physical Regimes and Mechanisms of Picosecond Laser Fragmentation of Gold Nanoparticles in Water from X-ray Probing and Atomistic Simulations.

Laser fragmentation in liquids has emerged as a promising green chemistry technique for changing the size, shape, structure, and phase composition of colloidal nanoparticles, thus tuning their properties to the needs of practical applications. The advancement of this technique requires a solid understanding of the mechanisms of laser-nanoparticle interactions that lead to the fragmentation. While theoretical studies have made impressive practical and mechanistic predictions, their experimental validation is required. Hence, using the picosecond laser fragmentation of Au nanoparticles in water as a model system, the transient melting and fragmentation processes are investigated with a combination of time-resolved X-ray probing and atomistic simulations. The direct comparison of the diffraction profiles predicted in the simulations and measured in experiments has revealed a sequence of several nonequilibrium processes triggered by the laser irradiation. At low laser fluences, in the regime of nanoparticle melting and resolidification, the results provide evidence of a transient superheating of crystalline nanoparticles above the melting temperature. At fluences about three times the melting threshold, the fragmentation starts with evaporation of Au atoms and their condensation into small satellite nanoparticles. As fluence increases above five times the melting threshold, a transition to a rapid (explosive) phase decomposition of superheated nanoparticles into small liquid droplets and vapor phase atoms is observed. The transition to the phase explosion fragmentation regime is signified by prominent changes in the small-angle X-ray scattering profiles measured in experiments and calculated in simulations. The good match between the experimental and computational diffraction profiles gives credence to the physical picture of the cascade of thermal fragmentation regimes revealed in the simulations and demonstrates the high promise of the joint tightly integrated computational and experimental efforts.

A mechanism for spontaneous thermal fragmentation with coolant entrainment during the molten fuel–sodium interaction

Experimental investigation of two interactions between metallic corium jets and sodium, pertaining to severe accidents in a sodium-cooled fast reactor, have been undertaken at the MELT facility. X-ray imaging and debris analysis reveal rapid formation of a crust at the melt coolant-interface, instigating thermal fragmentation events. Heat transfer calculations at the jet-coolant interface, supported by particle tracking velocimetry characterisation of the jet velocity, imply the formation of a solid crust within milliseconds of contact with the coolant. A mechanism for enhanced thermal fragmentation is proposed, inspired by observations from the X-ray imaging of coolant entrainment into the jet. Elevated pressures at the internal crust wall compete with densification and contraction of the crust, resulting in significant stress in the crust. Modelling of the thermoelastic stress field indicates that fracture is dictated by the tangential stress at the outer crust wall, consistent with 200–300 μm long fractures observed during SEM imaging of the outer crust surface. The elevated pressure at the internal crust wall appears to dominate on short timescales, imparting tensile stress at the outer crust wall which may initiate fracture. On longer cooling times, the densification and contraction of the jet dominate resulting in tangential compression. Thus, coolant entrainment and vaporisation within the jet appears to impart competing stresses in the crust which may influence the mode of jet rupture.

Enantioselective Potassium-Catalyzed Wittig Olefinations.

We report asymmetric potassium-isothiourea-boronate-catalyzed Wittig olefinations of 4-substituted cyclohexanones with non-stabilized phosphorus ylides to afford highly enantioenriched axially chiral alkenes. The optimal catalyst features an unusual macrocyclic amide-potassium-boronate chelate. Kinetic and spectroscopic analyses are consistent with a Lewis acid mechanism for the catalytic olefination that results in the formation of the oxaphosphetane adduct under cryogenic conditions. Thermal fragmentation of the oxaphosphetane to the alkene product occurs after the reaction is complete. Computational studies indicate that cycloaddition proceeds via a stepwise mechanism involving enantiodetermining polar 1,2-addition to afford an intermediate potassium betaine complex.

Microfacies shift in the Late Paleocene–Early Eocene Patala Formation in the Upper Indus Basin (Pakistan): Implications for development of the Ceno-Tethys Ocean

Field observations, petrography, and laboratory interpretations of the Patala Formation were utilized in an integrated petrologic study aimed at deciphering the genesis mechanism and controlling factors of the limestone/shale alternation during the mature development of the Ceno-Tethys Ocean in the Upper Indus Basin of Pakistan. To achieve this goal, the Patala Formation is categorized into four integrated microfacies (MM-I to MM-IV). Multiple cycles of transgression/regression are noted through fluctuations in eustatic sea level, controlled by climate and regional tectonism. Consequently, a deepening, upward retrogradation sequence was deposited on a carbonate platform of the Ceno-Tethys Ocean. The sediments of the Patala Formation exhibit a facies shift from a shallow-marine to a relatively deep-marine platform. It is indicated by the transition in fossils from shallow-marine green algae, trending towards a relatively deeper-shelf comprising benthic foraminifera such as Discocyclina, Ranikothalia, red coralline algae, echinoids (Echinothrix), and Alveolina, species. The deeper species possess robust shells adapted by organisms to maximize oxygen and light at greater depths. Additionally, mineralogical features, including gypsum (deposited in a lagoon within the platform) and pyrite (found in a deep slope toward a deep shelf), confirm deepening upward interpretations. Thermophilic dinoflagellates, thermal dissolution fragments, and hardground surfaces indicate a Paleocene-Eocene Thermal Maximum (PETM; in the lower part, ca. 56 Ma) of the Patala Formation, assigning a relative chronological age from the late Paleocene to early Eocene. These results highlight the joint influence of climate change, sea level rise, and continuous tectonic activity (associated with the Indo-Eurasian collision) on the pattern of sediment filling, and facies shift. Furthermore, the study contributes to understanding sedimentary environments, paleoenvironmental reconstruction, and paleotectonic evolution of the basin. This ideal case study provides a breakthrough advancement in globally comprehending the complex relationships between periodic autocyclic processes and aperiodic allocyclic events.

Laser-Pulse-Length Effects in Ultrafast Laser Desorption.

Shortening the laser pulse length opens up new opportunities for laser desorption (LD) of molecules, with benefits for mass spectrometry (MS) sampling and ionization. The capability to ablate any material without the need for an absorbing matrix and the decrease of thermal damage and molecular fragmentation has promoted various applications with very different parameters and postionization techniques. However, the key issues of the optimum laser pulse length and intensity to achieve efficient and gentle desorption of molecules for postionization in MS are not resolved, although these parameters determine the costs and complexity of the required laser system. Here, we address this research gap with a systematic study on the effect of the pulse length on the LD of molecules. Keeping all other optical and ionization parameters constant, we directly compared the pulses in the femtosecond, picosecond, and nanosecond range with respect to LD-induced fragmentation and desorption efficiency. To represent real-world applications, we investigated the LD of over-the-counter medicaments naproxen and ibuprofen directly from tablets as well as the LD of retene and ship emission aerosols from a quartz filter. With our study design, we excluded interfering effects on fragmentation and LD efficiency from, for example, collisional cooling or postionization by performing the experiments in vacuum with resonance-enhanced multiphoton ionization as the postionization technique. Regarding LD-induced fragmentation, we already found benefits for the picosecond pulses. However, the efficiency of LD was found to continuously increase with decreasing pulse length, pointing to the application potential of ultrashort pulses in trace analytics. Because many interfering effects beyond the LD pulse length could be excluded in the experiment, our results may be directly transferable to the LD applied in other techniques.

Investigating the Impact of Pores on Rock Damage during Thermal Spalling Drilling

Numerous microcracks and pores in geological rock formations cause early flaws. High temperatures increase these fractures and pores, thermally damaging reservoir rocks and changing the rock failure mechanism. However, research on pores' high-temperature thermal spalling and fragmentation effects on heterogeneous rocks is sparse. This study built a finite element numerical model of heterogeneous granite rock thermal damage with pores based on rock thermal fracture theory and the Voronoi method and explored the mechanism under varied pore settings. The research's findings indicate that the application of high temperatures to local heterogeneous porous rocks results in a higher proportion of tensile damage. The proportion of shear damage and tensile damage constantly varies due to the changing position and shape of the pores. The rock's porosity has the effect of decreasing temperature in the direction of heat transfer while increasing the extent of temperature transfer along the pore parallel to the heating surface. The potential degree of damage increases as the density of pores increases, the distances between them decrease, and the pore lengths increase. The thermal damage resulting from heating in the vicinity of the pore is primarily localized in the area between the pore and the heated surface. This effect becomes more significant as the distance between them decreases. The findings of this study can serve as a theoretical framework for understanding the impact of rock pores on rock thermal fracturing and fragmentation in the thermal spalling-assisted development of deep oil and gas resources.

Synthesis of new Fe(III), Co(II), and Cr(III) complexes of N‐(benzo[d]thiazol‐2‐ylcarbamothioyl)benzamide (H2L2): Structural characterization and biological activities

N‐(benzo[d]thiazol‐2‐ylcarbamothioyl)benzamide (H2L2) was synthesized as a novel thiosemicarbazide containing benzothiazole moiety, by the reaction of benzoyl isothiocyanate with 2‐aminobenzothiazole in benzene. The (H2L2) thiosemicarbazide and its isolated Cr(III), Fe(III), and Co(II) complexes were fully analyzed by different spectroscopic techniques. The thermal fragmentation of [Cr (HL2)Cl2(H2O)2].10H2O, [Co (HL2)Cl(H2O)2].6H2O, and [Fe(L2)Cl(H2O)2] were analyzed. We have also calculated the thermal parameters with using two different methods. The ligand undergoes tranamidation in the presence of PdCl2. Crystal structure of the product obtained by tranamidation is measured. Biological activities of those compounds were assessed as antioxidants, anticancer, and antimicrobial.

Role of magnetic fields in the fragmentation of the Taurus B213 filament into Sun-type star-forming cores

Fragmentation is a key step in the process of transforming clouds (and their substructures, such as filaments, clumps and cores) into protostars. The thermal gas pressure and gravitational collapse are believed to be the primary agents governing this process, referred as thermal Jeans fragmentation. However, the contributions of other factors (such as magnetic fields and turbulence) to the fragmentation process remain less explored. In this work, we have tested possible fragmentation mechanisms by estimating the mean core mass and mean inter-core separation of the B213 filament. We have used the $$\sim $$ 14 $$^\circ $$ resolution James Clerk Maxwell Telescope (JCMT) Submillimeter Common-User Bolometer Array 2 (SCUBA-2)/POL-2 850 $$\mu $$ m dust continuum map and combined it with a Planck 850 $$\mu $$ m map and Herschel data. We find that in addition to the thermal contribution, the presence of ordered magnetic fields could be important in the fragmentation of the B213 filament.

Investigation of thermal decomposition of nitrobenzene: An energetic material

Oxidation and pyrolysis mechanisms of energetic materials shape their macro properties such as autoignition and detonation. The high reaction-enthalpy, microsecond order reaction time, and toxicity necessitate investigation of their detailed chemical kinetics. A shock tube combined with laser absorption diagnostic provides time-resolved, high-sensitivity, and homogeneous environment to study thermal degradation of energetic and hazardous materials. In this work, we investigated the thermal fragmentation of nitrobenzene (C6H5NO2), a prototypical energetic material and nitro-aromatic representative, behind reflected shock waves. We studied its pyrolysis and decomposition branching channels over temperatures of 1155–1434 K and pressures of 0.82–1.78 bar. Channel-specific branching ratio was determined by employing a two-color laser absorption diagnostic. Two decomposition pathways are found to be significant under our experimental conditions. The first channel (k1) produces phenyl radical (C6H5) and NO2 while the second channel (k2) generates phenoxy radical (C6H5O) and NO. We monitored the reaction progress by tracing channel-specific products, i.e., phenyl radical (C6H5) and NO, using ultraviolet–visible (UV–vis) and infrared (IR) absorption diagnostics. UV–vis light at 445 nm for phenyl radical detection came from the frequency doubling of 890 nm light, generated by a titanium–sapphire laser, which was pumped by a green (532 nm) Nd:YAG laser. IR light at 5.517 μm for NO detection was generated by an external-cavity quantum cascade laser. We extracted the rate coefficients of the two decomposition channels and fitted them in Arrhenius form (units of s−1):k1=8.49×1014exp(−30476KT)k2=2.31×1013exp(−27618KT)Rate coefficients of both channels show positive temperature dependence while we did not observe discernible pressure dependence over 0.82–1.78 bar. Our measurements agree with a previous theoretical work qualitatively that, under these high-temperature conditions, the decomposition channel producing phenyl radicals and NO2 (k1) prevails over the NO-producing channel. Quantitatively, however, the theoretical work overestimates the importance of k1 channel, particularly at low temperatures. Our rate of production analysis shows that most of the phenyl radicals are consumed through their self-recombination while N atoms are mainly converted to NO2. This work benefits high-fidelity chemical modeling of the relevant safety and ignition aspects of nitrogen-containing energetic/hazardous materials.

New Chemistry of Chiral 1,3-Dioxolan-4-Ones.

(2S,5S)-5-Phenyl-2-t-butyl-1,3-dioxolan-4-one, readily derived from mandelic acid, undergoes the Michael addition to butenolide and 4-methoxy-β-nitrostyrene with the absolute configuration of the products confirmed by X-ray diffraction in each case. In the former case, thermal fragmentation gives the phenyl ketone, thus illustrating use of the dioxolanone as a chiral benzoyl anion equivalent. The Diels-Alder cycloaddition chemistry of (2S)-5-methylene-2-t-butyl-1,3-dioxolan-4-one, derived from lactic acid, has been further examined with the X-ray structures of four adducts determined. In one case, thermal fragmentation of the adduct gives a chiral epoxy ketone resulting from the dioxolanone acting as a chiral ketene equivalent, while in others the products give insight into the mechanism of the dioxolanone fragmentation process.

A data-driven sequencer that unveils latent "codons" in synthetic copolymers.

The recent emergence of sequence engineering in synthetic copolymers has been innovating polymer materials, where short sequences, hereinafter called "codons" using an analogy from nucleotide triads, play key roles in expressing functions. However, the codon compositions cannot be experimentally determined owing to the lack of efficient sequencing methods, hindering the integration of experiments and theories. Herein, we propose a polymer sequencer based on mass spectrometry of pyrolyzed oligomeric fragments. Despite the random fragmentation along copolymer main-chains, the characteristic fragment patterns of the codons are identified and quantified via unsupervised learning of a spectral dataset of random copolymers. The codon complexities increase with their length and monomer component number. Our data-driven approach accommodates the increasing complexities by expanding the dataset; the codon compositions of binary triads, binary pentads and ternary triads are quantifiable with small datasets (N < 100). The sequencer allows describing copolymers with their codon compositions/distributions, facilitating sequence engineering toward innovative polymer materials.