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The thermally activated recombination reaction O+O2→O3 is observed in solid xenon matrices and in free-standing crystals of xenon at 14–25 K on the time scale 102–105 s. The reactants are prepared as spatially separated O...O2 pairs immobilized in solid Xe at 10 K by 266 nm photodissociation of O3 precursor molecules. The temperature dependence of the ozone recovery rate yields an activation energy for diffusion of O atoms in solid xenon of 2.0±0.5 kJ/mol. This value also represents an upper limit to the potential energy barrier to the O+O2 recombination reaction itself. In dilute samples (mole fraction of ozone less than 2×10-4) more than 90% of the initial O3 is recovered during the warming cycle. Only a small fraction of O atoms (<20%) escape geminate recombination with the partner oxygen molecule within the pair and react with other O2 molecules or O atoms. The experimental results are interpreted within the framework of a continuous diffusion model in which the initial spatial distribution of reactants is nonrandom. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The inhomogeneous broadening caused by dipole–dipole interactions between molecules having strongly allowed optical transitions is considered for the case in which the chromophores are randomly distributed at low concentration in a transparent matrix. Model calculations show that absorption in the wings of the spectrum is caused almost exclusively by strongly interacting pairs of chromophores. This result has important implications for the interpretation of recent experiments in which the spectra of single dye molecules have been observed in organic matrices. The generalized lineshape in these wings is shown to be proportional to the inverse square of the detuning from line center. The line shape is also somewhat asymmetric, with the red wing being more intense than the blue. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Dipole–dipole interaction between molecular vibrations is the most important source of inhomogeneous line broadening in the strongest infrared absorption bands of amorphous films of N2O and O3 prepared by vapor deposition at cryogenic temperatures. This type of broadening occurs in all strongly allowed absorption bands of amorphous solids. Comparison of spectra obtained for amorphous and polycrystalline ozone show that the crystal structure is anisotropic, and most likely uniaxial. The absorption line shape of amorphous films is satisfactorily predicted by a computational model in which orientationally disordered molecules on a regular lattice interact through long-range dipole interactions. It is shown that the normal vibrations are delocalized throughout the solid, and the absorption line shape depends on the macroscopic shape and orientation of the sample. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The photochemistry of solid ozone and solid solutions of ozone in argon has been investigated at 10–30 K using 266 nm laser irradiation and detection by ultraviolet and infrared absorption spectroscopies. Pure ozone is converted to O2 with a quantum yield of 2.0±0.3 (independent of temperature) due to reaction of each photolytically generated O atom with a second ozone molecule. The quantum yield decreases when O3 is diluted in argon because geminate recombination of O+O2 becomes competitive with the O+O3 reaction. Photodissociation of ozone monomers is thought to occur by direct cage escape, which forms a separated O+O2 pair. This is the first experimental study in which the temperature dependence of the escape probability has been systematically investigated. The apparent activation energy of the process, 0.38±0.08 kJ/mol, is consistent with excitation of librations of ozone in the argon lattice, which brings it into orientations that are favorable for direct cage escape of the O atom. [ABSTRACT FROM AUTHOR]

Mixing of near-degenerate vibrational modes by long-range dipole–dipole interactions can lead to complicated band shapes in the infrared spectra of clusters and microcrystals, particularly when the bands are inhomogeneously broadened as a result of distributions of crystal shapes and orientations in the sample. For the special case in which the clusters have isotropic crystal structures, the equivalence of amplitude vectors for all IR-active vibrational phonon modes permits the band shapes of dipole-mixed modes to be predicted from those of isolated modes. This analysis is successfully applied to experimental infrared spectra of thin films containing weakly interacting microcrystals of CO2 or N2O, as well as to CO2 clusters prepared by condensation in the gas phase. The results prove that these gas-phase clusters of CO2 have an isotropic crystalline structure. [ABSTRACT FROM AUTHOR]

Infrared and Raman spectroscopy are used to examine effects of solid structure on vibrational line shapes in thin solid films of CO2 and N2O prepared by vapor deposition. A new method is described for forming films consisting of weakly-interacting microcrystals by deposition of the solute in an argon matrix followed by complete evaporation of the argon. The infrared absorption bands of these films exhibit inhomogeneous spectral broadening in the range between the transverse and longitudinal frequencies of the bulk crystal. The origin of this broadening is shown to be the dependence of vibrational frequencies on size and shape of the microcrystals due to long-range dipole interactions. In contrast, the spectra of polycrystalline films formed by direct vapor deposition are the same as for single crystals because the long-range dipole interactions effectively couple vibrational motions across the grain boundaries. An analysis shows that inhomogenously broadened spectra are obtained whenever the separation between the individual crystal grains is comparable to or greater than their dimensions. [ABSTRACT FROM AUTHOR]

Reports on the shock waves which were generated in thin films of glycidyl azide polymer by pulsed laser vaporization of a thin aluminum film. Experimental details; Results and discussion.

The photodissociation of gaseous Co(CO)3(NO) and Co(CO)2(NO)(PX3), where X=CH3, C2H5, n-C3H7, and n-C4H9 has been investigated near 225 nm by state-selective multiphoton ionization detection of nitric oxide fragments. The observed NO photofragment rotational distributions in v=0 are approximately Boltzmann, and the characteristic temperature decreases with increasing size of the phosphine ligand. The yield of photofragments appearing within the 10 ns detection time scale also decreases with increasing molecular size. An analogous effect is observed for the v=1/v=0 vibrational population ratio of the NO photoproducts. These results show that intramolecular energy transfer is fast compared with scission of the Co–NO bond. A dissociation model is proposed involving initial loss of CO followed by loss of other ligands via an RRKM-like process. [ABSTRACT FROM AUTHOR]

The rotational state distribution for NO produced by dissociation of (η5–C5H5)NiNO near 225 nm has been obtained by [1+1] resonance-enhanced multiphoton ionization. The distribution is approximately characterized by a Boltzmann distribution at T=900±200 K. The relative populations of the two spin–orbit components of the ground 2Π manifold are also consistent with this temperature. No preference is observed for populating either of the lambda–doublet components, even at high rotational quantum numbers. Comparison of the results with statistical models shows that the state distribution is significantly colder than expected. One plausible explanation for this is that the parent molecule dissociates to produce cyclopentadienylnickel fragments in an excited electronic state. [ABSTRACT FROM AUTHOR]

Electronic-to-vibration (E–V) energy transfer from excited Br(4 2P1/2) atoms to nitrosyl bromide has been investigated by an infrared fluorescence technique. The excited bromine atoms are generated by pulsed laser photolysis of Br2 at 500 nm. Approximately 50% of the quenching collisions of Br*+BrNO yield BrNO molecules excited in the 1800 cm-1 v1 stretching mode. Of these, six times as many BrNO molecules are produced in the v1=1 state as in v1=2, despite the fact that the latter is nearly resonant with the electronic energy of Br*. The total rate coefficient for removal of Br* by BrNO is determined to be (1.5±0.2)×10-11 cm3 molecule-1 s-1. Indirect comparison of our results with previous work suggests that quenching proceeds primarily by inelastic collisions; reactive quenching to form Br2+NO is probably a minor channel. [ABSTRACT FROM AUTHOR]

Vibrational, rotational, and spin-orbit state distributions are obtained for inelastic collisions of H+NO at 2.2 and 0.95 eV. The H atoms are generated by excimer laser photolysis of H2S at 193 and 248 nm, respectively, and the excited states of the NO molecules are probed by laser-induced fluorescence using a tunable dye laser. The rotational state distribution accompanying the T-V excitation of v=1–3 at 2.2 eV is approximately characterized by a Boltzmann distribution at 1275 K, and is essentially independent of the vibrational level excited. At 0.95 eV, the rotational populations are approximately characterized by a 1050 K distribution. In each case, the temperatures of the spin-orbit state populations and the rotational states are the same. No selective population of Λ-doublet states is observed. The results are discussed in terms of chemical interactions between these two open-shell species on the HNO potential energy surfaces. [ABSTRACT FROM AUTHOR]

Abstract: A solid phase explosives deflagration and detonation model capable of surface burning, convective bulk burning and detonation is formulated in the context of Eulerian–Lagrangian material mechanics. Well-validated combustion and detonation models, WSB and JWL++, are combined with two simple, experimentally indicated transition thresholds partitioning the three reaction regimes. Standard experiments are simulated, including the Aluminum Flyer Plate test, the Cylinder test, the rate stick test and the Steven test in order to validate the model. Cell and particle resolution dependence of simulation metrics are presented and global uncertainties assigned. Error quantification comparisons with experiments led to values generally below 7% (1σ). Finally, gas flow through porous media is implicated as the driving force behind the deflagration to detonation transition. [Copyright &y& Elsevier]

Proposes a statistical procedure for estimating realistic confidence intervals for the activation energy determined by using an advanced isoconversional method. Capability of the proposed statistical procedure of adequately estimating the actual uncertainty in the activation energy determined from a small number of measurements.

This review covers both the history and present state of the kinetics of thermally stimulated reactions in solids. The traditional methodology of kinetic analysis, which is based on fitting data to reaction models, dates back to the very first isothermal studies. The model fitting approach suffers from an inability to determine the reaction model uniquely,and this does not allow reliable mechanistic conclusions to be drawn even from isothermal data. In non-isothermal kinetics, the use of the traditional methodology results in highly uncertain values of Arrhenius parameters that cannot be compared meaningfully with isothermal values. An alternative model-free methodology is based on the isoconversional method. The use of this model-free approach in both isothermal and non-isothermal kinetics helps to avoid the problems that originate from the ambiguous evaluation of the reaction model. The model-free methodology allows the dependence of the activation energy on the extent of conversion to be determined. This, in turn, permits reliable reaction rate predictions to be made and mechanistic conclusions to be drawn. [ABSTRACT FROM AUTHOR]

The laser-initiated reaction of chlorine with cyclobutane, deposited as a thin amorphous film at 77 K, is found to produce exclusively chlorocyclobutane and HC1 via a free radical chain mechanism. The reactions are initiated by pulsed laser photolysis of molecular chlorine at 308 nm. Product formation is monitored by Fourier transform infrared absorption spectroscopy. The quantum yield for reaction increases from 1.1±0.3 in an equimolar mixture to a yield of 7.4±0.8 for mixtures rich in cyclobutane. These results are consistent with a reaction mechanism which involves the transfer of a hydrogen atom from cyclobutane to cyclobutyl radical, permitting the radical site to propagate freely in the solid. [ABSTRACT FROM AUTHOR]

Laser multiphoton dissociation–resonance-enhanced multiphoton ionization (MPD–REMPI) and time-of-flight photoelectron spectra (TOF-PES) of Fe(C5H5)2, Co(C5H5)2, and Ni(C5H5)2 have been obtained in the range 380–390 nm, and the MPD–REMPI of Fe(C5H5)2 and Co(C5H5)2 have been obtained in the range 445–455 nm. The only ions produced by the pulsed dye laser are Fe+, Co+, and Ni+. Transitions observed in the MPD–REMPI spectra are assigned to resonant states of the neutral atoms. Final states of the atomic ions are determined from the TOF-PES spectra. For Ni and Co, there appears to be a propensity for core preservation of the resonant state upon ionization if the resonant state has an electron configuration with an electron in a d-type Rydberg orbital. For Fe, no such propensity is observed. [ABSTRACT FROM AUTHOR]

Laser multiphoton dissociation-resonance-enhanced multiphoton ionization (MPD-REMPI) and time-of-flight photoelectron spectra (TOF-PES) of Co(CO)3NO and Fe(CO)5 have been obtained in the range 445–455 nm. The only ions produced by the pulsed dye laser are Co+ and Fe+. Transitions observed in the MPD-REMPI spectra are assigned to resonant states of the neutral atoms. Final states of the atomic ions are determined from the TOF-PES spectra. The multiphoton dissociation process produces metal atoms in a broad distribution of states, ranging in energies up to 33 000 cm-1 for Co, and 32 000 cm-1 for Fe. The most intense REMPI lines are associated with low-lying electronic states (<8500 cm-1 for Fe and Co). By tuning the laser to appropriate wavelengths, neutral metal atoms in selected electronic states may be ionized. At most laser wavelengths, the atomic metal ions are formed in a distribution of states, only some of which are consistent with preservation of the core configuration of the Rydberg intermediate in the ionization step. An exception appears for ionization of Co atoms via 4d Rydberg intermediate states. [ABSTRACT FROM AUTHOR]

Background: Pembrolizumab is a humanized monoclonal antibody that is used to treat a variety of cancers. It exerts its mechanism of action by blocking the programmed death receptor-1 (PD-1). Toxicity concerns include immune-related toxicities, including colitis, hepatitis, pneumonitis, nephritis, endocrine toxicities and more rarely, myocarditis and other organ system toxicities. Objective: To review a real-world case involving immunotherapy induced myocarditis after a patient received pembrolizumab and discuss how the current pandemic created complexity in toxicity management. Discussion: An 83 year old male with metastatic lung cancer developed fatal myocarditis after receiving 2 doses of pembrolizumab. Applying the Naranjo score, the likelihood of pembrolizumab causing the myocarditis is probable, with a score of 6. Severe cardiac toxicities are rare with pembrolizumab, but can still occur. It is vital to be aware of these toxicities, and educate patients on signs and symptoms. Complicating the situation even further was the global pandemic, which created fear and hesitation in the patient and the patient's family to seek medical treatment out of fear of exposure. This pandemic adds another layer to the complexity of care for patients with cancer and management of toxicities. Pharmacists play a significant role in ensuring the safety and efficacy of medications, especially oncology agents. Conclusion: Proper education of patients regarding symptoms and when to report are paramount to assisting in early detection and intervention for immunotherapy-related adverse events. New management and treatment strategies will need to be discussed and implemented considering the changing landscape around the SARS-CoV-2 pandemic. [ABSTRACT FROM AUTHOR]

Thermal analysis has been employed to determine the kinetics and the energetics of the slow cook-off chemistry of 2,4,6-trinitrotoluene (TNT) by isothermal differential scanning calorimetry (DSC) in high-pressure crucibles sealed under air. Model-free isoconversional analysis of the DSC kinetic traces has been used to determine activation energies (Eα) and the functional form of the reaction model (dependence of reaction rate on the extent of conversion, α). While the variation in Eα with α is in qualitative agreement with the literature it is nevertheless constant within the 95% confidence limits at 140±10 kJ mol−1. Hence, no systematic variation in Eα occurs over the course of the reaction. Rather, the reaction model exhibits a large increase in the range 0.1<α<0.25 and a decrease for 0.25<α<0.43. Thus, the observed acceleratory period is caused by an increase in the reaction model, not by a decrease in activation energy, as might be expected for autocatalysis. This kinetic behavior is ascribed to nucleation and growth of reaction centers in liquid state TNT. In addition, a heat of reaction, Q=(4.9±1.5)×102 kJ mol−1 during the thermal decomposition of TNT has been shown to be independent of the heating rate and sample size. [Copyright &y& Elsevier]

Photochemical reaction of the π-type fluoromethylene amidogen radical HFC=N... was studied by infrared, electroparamagnetic resonance, and laser-induced fluorescence spectroscopies in solid argon matrices. Laser excitation of the 0-0 band of the first excited state of HFC=N... at 488.1 nm leads to complete conversion to another structural isomer, the σ-type fluoroiminomethyl radical FC...= NH. The quantum yield of the photoisomerization reaction is φ[sub H] &assymp; 0.5 at temperatures T ≤ 30 K. Experiments using pulsed laser excitation show that the rate constant for hydrogen atom transfer is k[sub H]=5 x 10[sup 4] s[sub -1] at T≤ 30K, whereas the rate constant of the analogous process in DFC=N... is only k[sub D]= 30 s[sup -1] under the same experimental conditions. The large kinetic isotope effect k[sub H]/k[sub D] &assymp; 1400 and absence of temperature dependence of k[sub H] show that the mechanism of photoisomerization is intramolecular tunneling transfer of the hydrogen atom in the first excited òA" state. Simple one-dimensional consideration of the tunneling transfer of an H or D atom fails to describe the observed values of k[sub H] and k[sub D]. Therefore, multidimensional character of the hydrogen atom tunneling transfer should be taken into account, and a multidimensional potential energy surface of the excited state is required to describe correctly the chemical dynamics of the HFCN molecular system. [ABSTRACT FROM AUTHOR]

Fluoromethylene amidogen radicals, HFC=N..., were generated in solid argon by solid-state chemical reactions of mobile F atoms with hydrogen cyanide. Highly resolved infrared and electroparamagnetic resonance spectra of HFC=N... were obtained in the temperature range 15-30 K. All six vibrational frequencies and the complete set of isotropic hyperfine coupling constants on magnetic nuclei ¹H, [sup 19]F, and [sub 14]N were determined experimentally. Calculated spectroscopic characteristics are in excellent agreement with experiments, showing that HFC=N... radical has a planar structure in the ground state. Two electronic absorption transitions were observed in the near-ultraviolet and visible spectral region. The first excited ²A" state of HFC=N... radical is calculated to have a planar structure very similar to the ground state, and lies 20 726 cm[sup -1] above the ground state [at the CCSD(T)/cc-pVTZ level of theory], in good agreement with the experimental value, 20430 cm[sup -1]. The observed Franck-Condon envelope in the laser-induced fluorescence spectra provides strong evidence for the similarity of the structures of the ground and first excited states. An intense absorption band centered at 355 nm is attributed to electronic transition between the ground and second excited states. [ABSTRACT FROM AUTHOR]

Highlights • Asian countries have among the highest numbers of people exposed to the impacts of climate-related hazards. • The article models and map sub-national “climate security vulnerability” in 11 countries in Asia. • Bangladesh, southern and western Myanmar, and parts of Pakistan were the most vulnerable locations. • In terms of populations exposed to climate hazards, the largest numbers were in India and Bangladesh. • The model is compared with the EM-DAT International Disaster Database, an expert survey, and alternative specifications. Abstract Asian countries have among the highest numbers of people exposed to the impacts of climate-related hazards and, thus, at greatest risk of mass death. Floods, droughts, and storms have always tested civilian governments and international humanitarian aid agencies. However, climate change threatens to make the problem worse by increasing the intensity and possibly the frequency of climate-related hazards. Humanitarian emergencies potentially upend and reverse progress on development priorities, making improved spatial awareness of likely hot spots a priority for adaptation and preparedness. This article presents the findings of the effort to map sub-national “climate security vulnerability” in 11 countries in South and Southeast Asia. Climate security vulnerability is defined as areas where large numbers of people are at risk of death due to exposure to climate-related hazards and the follow-on consequences of exposure, including but not limited to conflict. The Asian Climate Security Vulnerability Model Version 1 (ACSV V1) found that Bangladesh, parts of southern and western Myanmar (the Ayeyarwady region and Rakhine state), and parts of southern and northwest Pakistan (Sindh and Khyber Pakhtunkhwa provinces) were the most vulnerable from a climate security perspective. In terms of absolute numbers, the largest numbers of people who are exposed to climate hazards are in India followed by Bangladesh. Model results are compared with a geo-referenced version of the EM-DAT Disaster Database and by creating alternative model specifications informed by a survey of 18 regional experts. [ABSTRACT FROM AUTHOR]

The Uintah software framework for the solution of a broad class of fluid-structure interaction problems has been developed by using a problem-driven approach that dates back to its inception. Uintah uses a layered task-graph approach that decouples the problem specification as a set of tasks from the adaptive runtime system that executes these tasks. Using this approach, it is possible to improve the performance of the software components to enable the solution of broad classes of problems as well as the driving problem itself. This process is illustrated by a motivating problem: the computational modeling of the hazards posed by thousands of explosive devices during a deflagration-to-detonation transition that occurred on Highway 6 in Utah. In order to solve this complex fluid-structure interaction problem at the required scale, substantial algorithmic and data structure improvements were needed to Uintah. These improvements enabled scalable runs for the target problem and provided the capability to model the transition to detonation. The solution to the target problem from these runs provided insight as to why the detonation happened, as well as demonstrating a possible remediation strategy that may have avoided detonation. [ABSTRACT FROM AUTHOR]

A correction is provided for the article "In Harm's Way: Climate Security Vulnerability in Asia" by Joshua Busby, Todd G. Smith, Nisha Krishnan, Charles Wight, and Santiago Vallejo-Gutierrez which appears in a 2018 issue of the journal.