bluuebunny/crossref_metadata_2025_split huggingface dataset:
Duration and Continuity of Medicaid Enrollment Before the COVID-19 Pandemic
Authors: Ku Leighton , Platt Isabel 
Published: December 2022

ImportanceCOVID-19 relief legislation created a temporary moratorium on Medicaid disenrollment, but when the public health emergency ends, states will begin to “unwind” Medicaid enrollment. Prepandemic data shed light on factors that can affect Medicaid coverage stability.ObjectiveTo assess factors associated with the duration and continuity of Medicaid enrollment.Design, Setting, and ParticipantsIn this cross-sectional analyses of a Medicaid data set for 2016 that was released by the Agency for Healthcare Research and Quality in June of 2022, we analyze a nationally representative data set of 5.7 million persons, weighted to represent 70 million Medicaid beneficiaries in 2016. We focus on 22 million nondisabled, nonelderly adults for this analysis. The data were analyzed between July and September of 2022.Main Outcomes and MeasuresThe main outcomes were the average months of Medicaid enrollment in 2016 and the probability of churning, defined as a break in coverage between 2 periods of enrollment during the calendar year. We compared these outcomes by eligibility category, state, demographic characteristics, and key Medicaid policies, including whether the state expanded Medicaid and whether it used ex parte reviews (automated reviews of other administrative data to reduce renewal paperwork burdens).ResultsIn this cross-sectional analysis, we analyze a nationally representative Medicaid data set of 5.7 million persons, weighted to represent 70 million Medicaid beneficiaries in 2016, released by the Agency for Healthcare Research and Quality in June of 2022. The analysis focused on nonelderly, nondisabled adults (aged 18-64 years) with a weighted population size of 22.7 million, of which 18.4% were Black, 19.2% were Latino, 39.5% were White, 7.3% were other/Asian/Native American, and 15.5% had unknown race. Multivariable regression analysis indicated that those living in states that expanded Medicaid but did not use ex parte reviews had longer average duration (0.31 months longer; 95% CI, 0.03-0.59) and lower risk of churning(odds ratio [OR], .40; 95% CI, 0.39-0.40), whereas those living in nonexpansion states that used ex parte reviews had lower odds of churning (OR, .68; 95% CI, 0.66-0.70) but also had shorter average duration (3.1 months shorter; 95% CI, −3.4 to −2.8). Those living in expansion states that used ex parte reviews also had reduced churning (OR, .83; 95% CI, 0.82-0.85). The average duration varied widely by state, even after adjustments for demographic and state policy factors.Conclusions and RelevanceIf state Medicaid programs revert to prepandemic policies after the temporary moratorium ends, Medicaid coverage, particularly for nondisabled, nonelderly adults, is likely to become less stable again. Medicaid expansions are associated with improved continuity, but ex parte review may have a more complex role.
Analysis of Daily Ambient Temperature and Firearm Violence in 100 US Cities
Authors: Lyons Vivian H. , Gause Emma L. , Spangler Keith R. , Wellenius Gregory A. , Jay Jonathan 
Published: December 2022

ImportanceFirearm violence is a leading public health crisis in the US. Understanding whether and how ambient temperature is associated with firearm violence may identify new avenues for prevention and intervention.ObjectiveTo estimate the overall and regional association between hotter temperatures and higher risk of firearm violence in the US.Design, Setting, and ParticipantsThis cross-sectional study used distributed lag nonlinear models, controlling for seasonality and long-term time trends by city and pooled results overall and by climate region. The most populous cities in the US with the highest number of assault-related firearm incidence (ie, shootings) from 2015 to 2020 were analyzed. Data analysis was performed from October 2021 to June 2022.ExposuresMaximum daily temperature by city.Main Outcomes and MeasuresThe primary outcome was the number of assault-related firearm shootings by city.ResultsA total of 116 511 shootings in 100 cities were included in this analysis. The pooled analysis estimated that 6.85% (95% CI, 6.09%-7.46%) of all shootings were attributable to days hotter than city-specific median temperatures. This equates to 7973 total shootings (95% CI, 7092-8688 total shootings) across the 100 cities over the 6-year study period, although the number of total persons injured or killed would be higher. Estimated risk of firearm incidents increased almost monotonically with higher temperatures, with a local peak at the 84th percentile of the temperature range corresponding to a relative risk of 1.17 (95% CI, 1.12-1.21) compared with the median temperature. However, even moderately hot temperatures were associated with higher risk of shootings. Although significant, there was low heterogeneity between cities (I2 = 11.7%; CochranQtest,P = .02), indicating regional or climate-specific variation in the daily temperature and incident shootings relationship.Conclusions and RelevanceThese findings underscore the importance of heat adaptation strategies broadly throughout the year to reduce shootings, rather than focusing on only the hottest days.
Catalyst Modeling – Biological
Authors: Villà Jordi , Warshel Arieh 
Published: December 2022

AbstractThe catalytic power of enzymes reflects billions of years of refinement by evolution. Thus, understanding enzyme action should be very instructive as a guide for general principles of catalysis. This review describes the emerging use of computer modeling as a key toll in correlating enzyme structures and catalysis. The review starts by describing general computer simulation approaches for calculations of free energies and related properties. It then moves to methods that allow one to evaluate the free energy of enzymatic reactions. This includes hybrid quantum mechanical/molecular mechanics (QM/MM) molecular orbitals methods, the empirical valence bond (EVB) method, and other approaches. Emphasis is placed on specifying the requirement from reliable simulation approaches, including the need for accurate potential surfaces and a proper configurational sampling. The ability of different approaches to satisfy these serious requirements is critically examined. Next, we examine what has been learned from simulations of enzymatic reactions about the origin of enzyme catalysis. It is pointed out that consistent simulation studies concluded that electrostatic effects are the key catalytic factor and that the corresponding catalytic energy is stored in preorganized polar active sites. Studies that examined the magnitude of other catalytic contributions and the validity of the corresponding catalytic proposals are also considered. These include studies of various ground state destabilization effects (e.g. entropic, strain, and desolvation contributions), studies of dynamical effects, and studies of the low barrier hydrogen bond proposal. It is concluded that these contributions do not play a major role in enzyme catalysis. Finally, the future of computer simulations as a critical tool in studies of enzymatic reaction is briefly considered.
Catalytic Distillation
Authors: Ng Flora T. T. , Rempel Garry L. 
Published: December 2022

AbstractCatalytic distillation (CD) is a “green” reactor technology that combines a heterogeneous catalytic reaction and the separation of reactants and products via distillation in a single reactor/distillation column. CD is a rapidly developing field that incorporates catalysis, kinetics, and mass transfer to provide more selective and energy efficient processes. The heterogeneous catalyst provides the sites for catalytic reactions and also the interfacial surface for liquid/vapor separation. The distinct difference between the CD column and the conventional distillation column lies in the placement of solid catalysts usually incorporated in some kind of packing (CD packing) within the distillation column to provide a reaction section in addition to the traditional trays or random packings used for separations in the stripping the rectifying sections of the distillation column. Mass transfer characteristics of the CD packing in the reaction zone has significant influence on the product yield and selectivity. Equilibrium and nonequilibrium models have been developed to simulate and design CD processes. The benefits of CD include energy and capital savings, enhanced conversion and product selectivity, longer catalyst lifetime, and reduction of waste streams. Equilibrium limited and exothermic processes will benefit from CD. The first commercial application of CD was for the production of methyl tertiary butyl ether (MTBE). There are many other possible applications of CD such as the hydration of olefins, alkylations, esterifications, hydrolysis, aldol condensation, hydrogenation, desulfurization, and oligomerization of olefins. Currently most of the CD processes are related to the petroleum and petrochemical industries. The use of CD for the production of bulk and fine chemicals remain largely unexplored. Besides the development of new “green” processes using CD, fruitful areas of future research and development on CD include fundamental aspects of combining catalysis, reaction engineering, multiphase flow and separation, and the development of novel CD packings.
Diboration
Authors: Broene Richard D. , Baker R. Tom 
Published: December 2022

AbstractThe metal‐catalyzed addition of diboron compounds B2(OR)4to unsaturated organic molecules—including alkenes, allenes, alkynes, carbonyls, and imines and combinations of these groups—is reviewed, with emphasis on synthetically useful transformations. Mechanistic details of the reaction are discussed. Particular attention is paid to catalyst‐based chemo‐ and regioselectivity and substrate diastereoselection using chiral diboron compounds. Synthetically useful transformations of the resulting boronate esters are also presented.
Hydroamination – Heterogeneous
Authors: Müller T. E. 
Published: December 2022

AbstractThe direct addition of amines to carbon–carbon double and triple bonds (hydroamination) is of high interest for new processes for the production of amines. Currently, the reaction of ammonia with C2–C4 alkenes under supercritical conditions is studied most. Possible catalysts for this reaction are solid acids, mostly zeolites in the proton form. Structural, mechanistic, as well as thermodynamic and kinetic aspects are discussed. For the corresponding addition of amines to alkyne groups, zeolites ion‐exchanged with late transition metals proved to be most effective. Here, co‐catalysis between Lewis and Brønsted acid sites seems to be an important aspect.
Hydrocracking – Industrial Processes
Authors: Towler Gavin P. , Hoehn Richard K. 
Published: December 2022

Abstract
Hydrocracking can be used to accomplish several different processing objectives, treating feeds ranging from residual oils to naphtha and producing lighter products with lower sulfur and nitrogen content. The choice of process configuration depends on the feed and processing objective. Once‐through, single‐stage, two‐stage, separate hydrotreater and reverse‐flow process flowsheets are described. In all cases the reactor selection must address the issues of fluid distribution, heat removal, pressure drop, catalyst deactivation, and bed plugging. Common approaches to gas separation and product recovery are also described. Commercially licensed processes including H‐Oil, IFP hydrocracking, Isocracking, LC‐Fining, moderate pressure hydrocracking, Shell hydrocracking, and Unicracking are described with reference to the generic flowsheets. Relevant engineering issues such as fluid distribution, quench zone design, mercaptan recombination, heavy polynuclear aromatics control, heat integration, metallurgy considerations, process safety, and hydrogen management are discussed in detail. Approximate correlations for estimation of process utility requirements and capital investment are given.
Hydroformylation – Industrial
Authors: Kohlpaintner Christian 
Published: December 2022

AbstractAfter its discovery in 1938 the hydroformylation reaction soon became the most successful example for a homogeneously catalyzed industrial process, with an estimated installed annual capacity of almost 8 million tons in 2000. After the first plant start‐up in 1942, several companies developed cobalt‐based high pressure oxo processes. Shell and others developed high pressure processes with unmodified rhodium catalysts during the mid‐sixties. The introduction of ligand‐modified rhodium catalysts in 1976 allowed for smoother reaction conditions (pressure and temperature) and better selectivities toward linear products. Further milestones include usage of water‐soluble (Ruhrchemie/Rhone‐Poulenc Process, 1984) and phosphite‐modified rhodium catalysts (Union Carbide Mark IV, 1995). Both processes have their advantages in the catalyst/product separation (RCH/RP) or the improved yield of linear products (UCC Mark IV). All processes are discussed in depth in the article.
Hydrogenation – Heterogeneous
Authors: Gallezot Pierre 
Published: December 2022

AbstractThe development of heterogeneous hydrogenation catalysis started at the beginning of the twentieth century. It is still the most developed field of catalysis in terms of the varieties of catalysts and applications. This article gives a survey in two parts of all the aspects of heterogeneous catalysis dealing with the hydrogenation of organic molecules. The first deals with all the fundamental aspects including molecular mechanisms, kinetics of reactions, catalyst structure–activity/selectivity relationships, and all the physicochemical factors affecting the rate and selectivity of hydrogenation reactions. The second part deals with more practical aspects such as the description of the different types of hydrogenation catalysts, on their selection to achieve a specific hydrogenation reaction, and of their utilization in reactors.
Isotope Methods – Homogeneous
Authors: Bullock R. Morris , Bender Bruce R. 
Published: December 2022

AbstractThe article reviews the use of isotopes to determine mechanisms of homogeneously catalyzed reactions. Kinetic isotope effects (KIEs) and equilibrium isotope effects (EIEs) on single steps as well as those on complete catalytic cycles are considered. Coverage includes EIEs and KIEs for the addition and elimination of H2and hydrocarbons to metal complexes. Isotope effects for proton, hydrogen atom, and hydride transfer to and from metal complexes, along with insertions into metal–hydrogen bonds, are discussed in detail. Isotope effects on olefin polymerization, oxidation, hydrogenation, and hydroformylation are discussed. Isotope effects on spectroscopic properties are included by way of discussion and interpretation.
Isotope Methods in Catalysis – Biological
Authors: Schowen Richard L. , Schowen K. Barbara 
Published: December 2022

Abstract
Isotopic methods in the study of biocatalysis are chiefly used to characterize the mechanisms by which enzymes catalyze their target reactions. The techniques in use include tracer methods, by which the positions of individual atoms in a starting molecule are traced in downstream intermediates or products; exchange methods, in which isotopic mixing between distinct pools such as the solvent and enzyme‐bound intermediates is measured in order to test mechanistic hypotheses; and kinetic isotope effects, in which the relative rates of reaction of different isotopes of the same element are measured to identify rate‐limiting steps and determine transition‐state structures and other mechanistic information. Tracer and exchange methods are illustrated but, not being subject to easy generalization, are not treated in detail. The bulk of the article is devoted to kinetic isotope effects in the study of biocatalysts.
Kinetics of Catalyzed Reactions – Homogeneous
Authors: Espenson James H. 
Published: December 2022

Abstract
Catalysts are not static entities, instead they are species that repetitively recycle through at least two forms, and sometimes more. The catalyst opens a new pathway with a lower Gibbs energy of activation; it does not somehow lower the activation energy of an existing pathway. Certain mathematical approaches to the analysis of data from catalytic kinetics are given. Forms that are useful in practice must allow for the coexistence, at comparable concentration, of these three species: the catalyst (C), its complex with substrate (C·S) and very likely with product (C·P). The steady‐state approximation often provides a tractable solution, although its form may require one to rely on initial‐rate method rather than integration of the reaction progress over its entire time course. A more precise solution can be obtained by methods employing numerical integration or its equivalent, programs for which can be downloaded from the Internet. Some catalytic systems require the consideration of inhibitory phenomena, and the case of competitive, noncompetitive, and uncompetitive inhibition are presented. Data from the very earliest stages of a reaction, before product has accumulated, can provide rate constants for the important catalytst–substrate binding phase.
Kinetics of Catalyzed Reactions – Biological
Authors: McDonald Andrew G. , Tipton Keith F. 
Published: December 2022

AbstractAn understanding of the kinetic reaction pathways (mechanisms) followed by enzymes is an essential prerequisite to understanding how enzymes might function in their normal complex metabolic enviroments within cells and tissues. It is also important for the interpretation of the behavior of mutant enzymes, the design and behavior of enzyme inhibitors for drug use, and the meaningful comparison of enzyme activities between laboratories, tissue, and individuals. This account describes the kinetic behavior of enzymes that catalyze reactions involving one or more substrates, the mechanisms that may be followed and the application of inhibition and other approaches to determining the mechanism followed. Systems obeying simple saturation kinetics are described together with those that may lead to more complex behavior. Enzyme classification and nomenclature are outlined and possible complexities in the initial‐rate behavior of enzyme‐catalyzed reactions and in the dependence of rate upon enzyme concentration are also described along with accepted standards for the expression of enzyme activities.
Methanation
Authors: Tomoyuki Inui 
Published: December 2022

AbstractMethanation, i.e., catalytic hydrogenation of carbon oxides (CO and CO2), especially methanation of CO, has been studied extensively from the beginning of the twentieth century. Focus of academic and indusrial interests of methanation has shifted during the long period, and the history of methanation can be divided into three stages. In the first stage, methantion of CO had been studied as a typical catalytic reaction of simple molecules associated with Fischer–Tropsch reaction, which aims at the synthesis of higher carbon‐number hydrocarbons. In the second stage, methanation was applied to the production of high caloric gaseous fuel from coke oven gas and/or syngas, called SNG process. Methanation was also applied to a chemical heat pipe system, so‐called FVA–ADAM process, which aimed to establish an energy saving technology. In the third stage, the knowledge of methanation was extended to solve the problem of global warming with CO2. Especially, design of the catalyst for ultrarapid methanation of carbon oxides contributes in a practical way to solve global warming owing to CO2accumulation. Both catalyst components and pore structure of the catalyst support are significant factors that contribute to whether a catalyst may be used for ultrarapid methanation. Simultaneous methanation of CO and CO2is also described.
Michael Addition
Authors: Christoffers Jens 
Published: December 2022

AbstractThe Michael reaction is defined as the conjugate 1,4‐addition of carbon nucleophiles to acceptor‐substituted CC bonds. Enolates of β‐dicarbonyl compounds represent typical nucleophiles in this classical base‐catalyzed CC‐bond‐forming reaction, yielding 1,5‐dicarbonyl compounds as products. In some cases, metal catalysts as simple as FeCl3 6 H2O can be applied, avoiding basic reaction conditions and thus resulting in an improved chemoselectivity compared with base catalysis. The Michael reaction can be performed in an intramolecular or vinylogous fashion, and is known as an elementary step in several reaction sequences. In most cases, Michael reaction products have at least one new stereogenic center. In order to achieve asymmetric reactions, chiral auxiliaries, chiral Brönstedt bases, or metal complexes bearing chiral ligands have been reported as catalysts for the Michael reaction.
Molybdendium Enzymes and Models
Authors: Neiter Burgmayer Sharon 
Published: December 2022

Abstract

Enzymes whose catalytic reactions occur at a molybdenum center are described. These molybdoenzymes are found in organisms throughout the entire kingdom of life, from simple bacteria to humans, and are critical to the ecosphere. With only one exception, these approximately 40 enzymes catalyze reactions where an oxygen atom is added to or removed from the biological substrate. This generalization explains the terminology applied to these enzymes, which are variously called molybdenum hydroxylases, oxotransferases, and oxo–molybdenum enzymes. A survey of the four main families of molybdenum enzymes and a list of selected molybdoenzymes is provided. A brief discussion of the special dithiolene ligand called molybdopterin that is bound to molybdenum (and tungsten) in all of these enzymes is given, highlighting its structure and associated nomenclatural difficulties. Representative examples of mechanisms are illustrated. A considerable progress in understanding the special attributes of molybdenum and its associated ligand has been accomplished through studies of smaller molecules, called
analogue
or
model
systems. Several key examples of these model systems are described. These provide independent confirmation of the reasonableness of proposed mechanistic steps as well as point to unique aspects of molybdenum in the enzymes not easily mimicked by synthetic systems.
Nitrile Hydratase
Authors: Shearer Jason , Kovacs Julie A. 
Published: December 2022

Abstract

Nitrile hydratases (NHases) are metalloenzymes, found in soil bacteria, first isolated from toxic wate sites, which catalyze the hydration of nitrile to amides. These contain either a mononuclear non‐heme Fe
3+
or a non‐corrinoid Co
3+
. Initial spectroscopic studies demonstrated that both the metal centers are low spin (
S
= 1/2 for Fe
3+
and
S
= 0 Co
3+
). Two crystal structures of Fe‐NHase from
Rhodococcus
R312 have shown that the iron center is ligated by three cysteinates in a
fac
configuration, two amide nitrogens from the peptide backbone, and a hydroxide (active form) or NO (inactive form) in a site
trans
to a cysteinate. The electronic spectrum of the active form of Fe‐NHase is dominated by an intense π‐sulfur‐to‐metal charge transfer band near 700 nm. The EPR and electronic absorption spectra of Fe‐NHase are both substrate‐ and pH‐dependent. NHase has been used industrially in the multi‐kiloton production of commodity amides, has been utilized to a limited extent as a reagent for organic synthesis, and may find use in the field of chemical waste treatment. Model compounds, in combination with biochemical and biophysical techniques, have proven useful in answering fundamental questions concerning NHase, but several key issues remain unresolved. For examle, the mechanism of NHase catalysis remains to be elucidated, and the involvement of low spin, rather than the more reactive high spin metal ions (Co
3+
, Fe
3+
) in these reactions has yet to be explained.