Collision Conditions Research Articles

Thermal Reactions of (V2O5)nO–(n= 1–3) Cluster Anions with Ethylene and Propylene: Oxygen Atom Transfer Versus Molecular Association

Vanadium oxide cluster ions are prepared by laser ablation and the (V2O5)nO– (n = 1–3) clusters (V2O6–, V4O11–, and V6O16–) are selected by a quadrupole mass filter and interacted with ethylene (C2H4) and propylene (C3H6) in an ion trap reactor. Molecular association (MA) is observed for all of the reactions and oxygen atom transfer (OAT) is also observed for the V4O11– and V6O16– cluster systems. The branching ratio of the OAT versus the MA channel increases as the size of (V2O5)nO– increases and the OAT becomes the major channel in V6O16– + C2H4 and V6O16– + C3H6. Density functional theory computations are carried out for the reactions of V2O6– and V4O11– with C2H4 and the results are consistent with the experimental observations. Anionic metal oxide clusters are usually much less reactive than their cationic and neutral counterparts and this work is among the first to identify the OAT reactivity for cluster anions with hydrocarbon molecules under thermal collision conditions, to the best of our knowledge.

Research on HGV Collisions with Concrete Bridge Piers

Bridge piers are highly vulnerable to accidental collision with heavy truck vehicles. Current design and assessment codes account the effect of vehicle collision by means of an equivalent static load. This methodology although is simple but have raised many concerns on their suitability to reflect the exact collision condition, which is highly dynamic. Therefore many existing bridge piers are in great danger of malicious impact. Recently, a research collaboration is initiated between JKR and UTP to investigate the impact vulnerability of RC bridge piers when subjected to HGV truck collisions. The work involves using nonlinear finite element (FE) simulation to conduct complex vehicle-pier impact scenarios. This paper is intended to present the general outlook plan of this project with emphasis focused on the consideration of FE models used for HGV trucks and concrete bridge piers.

Study on Steel Railings Installed on Concave- and Convex-Curved Bridge Parapet

This paper reports performance results for steel bridge railings installed on concave- and convex-curved bridge parapet based on new-type posts. Preliminary experimental tests are first conducted to examine the behaviours of these posts when subjected to a collision from a heavy steel ball. The values thus verified are then fed into the LS-DYNA 3D analysis tool to generate improved simulations for the performances of new-type curved steel railings subjected to truck collisions. For some concave road curvatures, it is found that the impact angles between the vehicle and the railings are larger than assumed in the current Japanese specifications. Some researchers and engineers suspect that a curved railing is less effective than a straight one in the same collision conditions. The purposes of this study, in addition to contributing to the further improvement of curved steel railings, are accordingly to test the validity of the said suspicion, and to investigate the performances of these new-type concave-curved steel railings under larger collision impact angles. The performance results for concave- and convex-curved railings are compared against each other as well as with the results for straight railings.

Energy conversion and transfer for plasmas in a magnetic expansion configuration

A two-dimensional axisymmetric particle-in-cell code with Monte Carlo collision conditions has been used to study particle energy transfer in plasmas and conversion in applied magnetic and electric fields appropriate to coaxial acceleration. The research incorporates a computation scheme with: a model of single particle magnetic interactions; a model of single particle interactions in electric and magnetic fields; and a model of multi-particle collisional interactions in order to understand the energy transfer processes and conversion mechanisms of charged plasma particles. This approach predicts electron and ion motions along with their energy variations for physical conditions that occur in the related models; the results allow comparison with experimental data for magnetic field strengths of 0.01–0.05 T and electrode voltages of 22.0–32.0 V. With the incorporation of magnetic and electric field effects on charged particles, the multi-particle model includes electron-neutral ionization collisions, ion-neutral charge exchange collisions, and electron-ion Coulomb collisions. This research presents a new approach to achieve an underlying understanding of the plasma energy transfer and conversion in the external electric and magnetic fields that is not possible using magnetohydrodynamics continuum representations. Results indicate the following innovative conclusions: (1) Radial and azimuthal energies of magnetized electrons are converted into an axial electron energy component in the diverging magnetic field, and the azimuthal kinetic energy of unmagnetized ions is converted into axial and radial components. (2) In electric and magnetic fields, electric field energy is primarily converted into axial kinetic energy of magnetized electrons by the energy transformation effects of magnetic fields, and for unmagnetized ions, the radial kinetic energy component dominates in the conversion of electric field energy. (3) For the collisional plasma, electron kinetic energy tends to increase (or decrease) to a terminal value since electrons lose energy in collisions then gain energy again from the field. Ions acquire most energy directly from the electric field, although part of the electric field energy arrives to the ions by collisions. Further, the ion axial energy component dominates the total ion energy. The collision processes are found to be integral and essential for the conversion of the plasma non-directed energy gain to be converted into the resultant axial energy, the magnitudes of which are found to be in agreement with experimental results.

Directed gas-phase formation of the ethynylsulfidoboron molecule.

As a member of the organo sulfidoboron (RBS) family, the hitherto elusive ethynylsulfidoboron molecule (HCCBS) has been formed via the bimolecular reaction of the boron monosulfide radical (BS) with acetylene (C2H2) under single collision conditions in the gas phase, exploiting the crossed molecular beams technique. The reaction mechanism follows indirect dynamics via a barrierless addition of the boron monosulfide radical with its boron atom to the carbon atom of the acetylene molecule, leading to the trans-HCCHBS intermediate. As predicted by ab initio electronic structure calculations, the initial collision complex either isomerizes to its cis-form or undergoes a hydrogen atom migration to form H2CCBS. The cis-HCCHBS intermediate either isomerizes via hydrogen atom shift from the carbon to the boron atom, leading to the HCCBHS isomer, or decomposes to ethynylsulfidoboron (HCCBS). Both H2CCBS and HCCBHS intermediates were predicted to fragment to ethynylsulfidoboron via atomic hydrogen losses. Statistical (RRKM) calculations report yields to form the ethynylsulfidoboron molecule from cis-HCCHBS, H2CCBS, and HCCBHS to be 21%, 7%, and 72%, respectively, under current experimental conditions. Our findings open up an unconventional path to access the previously obscure class of organo sulfidoboron molecules, which are difficult to access through "classical" formation.

An experimental and theoretical investigation of the formation of C7H7 isomers in the bimolecular reaction of dicarbon molecules with 1,3-pentadiene

We report on the crossed molecular beam reaction of dicarbon, C2 (X1Σg+, a3Πu), with 1,3-pentadiene (C5H8; X1A′) conducted at a collision energy of 43kJmol−1 under single collision conditions and studied by ab initio and statistical calculations. The reactions involve indirect scattering dynamics initiated by the barrierless addition of dicarbon to the carbon–carbon double bond of 1,3-pentadiene followed by successive rearrangements leading eventually through hydrogen atom elimination to distinct C7H7 radical species. The experimental reaction exoergicity of 412±52kJmol−1 is consistent with the formation of cycloheptatrienyl, m-tolyl, and/or benzyl radicals predicted as the major products by theory.

Gas-Phase Synthesis of Boronylallene (H2CCCH(BO)) under Single Collision Conditions: A Crossed Molecular Beams and Computational Study.

The gas phase reaction between the boron monoxide radical (11BO; X2Σ+) and allene (H2CCCH2; X1A1) was investigated experimentally under single collision conditions using the crossed molecular beam technique and theoretically exploiting ab initio electronic structure and statistical (RRKM) calculations. The reaction was found to follow indirect (complex forming) scattering dynamics and proceeded via the formation of a van der Waals complex (11BOC3H4). This complex isomerized via addition of the boron monoxide radical (11BO; X2Σ+) with the radical center located at the boron atom to the terminal carbon atom of the allene molecule forming a H2CCCH211BO intermediate on the doublet surface. The chemically activated H2CCCH211BO intermediate underwent unimolecular decomposition via atomic hydrogen elimination from the terminal carbon atom holding the boronyl group through a tight exit transition state to synthesize the boronylallene product (H2CCCH11BO) in a slightly exoergic reaction (55 ± 11 kJ mol-1). Statistical (RRKM) calculations suggest that minor reaction channels lead to the products 3-propynyloxoborane (CH2(11BO)CCH) and 1-propynyloxoborane (CH3CC11BO) with fractions of 1.5% and 0.2%, respectively. The title reaction was also compared with the cyano (CN; X2Σ+)-allene and boronyl-methylacetylene reactions to probe similarities, but also differences of these isoelectronic systems. Our investigation presents a novel gas phase synthesis and characterization of a hitherto elusive organyloxoborane (RBO) monomer-boronylallene-which is inherently tricky to isolate in the condensed phase except in matrix studies; our work further demonstrates that the crossed molecular beams approach presents a useful tool in investigating the chemistry and synthesis of highly reactive organyloxoboranes.

Circumambulatory movement of negative charge ("ring walk") during gas-phase dissociation of 2,3,4-trimethoxybenzoate anion.

A dramatic "ortho effect" was observed during gas-phase dissociation of ortho-, meta-, and para-methoxybenzoate anions. Upon activation under mass spectrometric collisional activation conditions, anions generated from all three isomers undergo a CO2 loss. Of the m/z 107 ions generated in this way, only the 1-dehydro-2-methoxybenzene anion from the ortho isomer underwent an exclusive formaldehyde loss. A peak for a formaldehyde loss in the spectra of 2,4-, 2,5-, and 2,6-dimethoxybenzoates and the absence of an analogous peak from 3,4- and 3,5-dimethoxy derivatives confirmed that this is a diagnostically useful ortho-isomer-specific phenomenon. Moreover, the spectrum from 2,3-dimethoxybenzoic acid showed peaks for two consecutive formaldehyde losses. The 1-dehydro-2,3,4-trimethoxybenzene anion (m/z 167) generated from 2,3,4-trimethoxybenzoate in this way endures three consecutive eliminations of formaldehyde units. For this, the negative charge, initially located on position 1, circumambulates to position 2, then to position 3, and finally to position 4 to form the final phenyl anion. The proposed stepwise fragmentation pathway, which resembles the well-known E1cB-elimination mechanism, is supported by tandem mass spectrometric observations made with 2-[(13)C(2)H3]methoxy-3-[(13)C]methoxy-4-methoxybenzoic acid, and ab initio calculations. In addition, the spectra of ions such as 1-dehydro-3,4-dimethoxybenzene anion show peaks for consecutive methyl radical losses, a feature that establishes the 1,2-relationship between the two methoxy groups.

Computational modeling of vibration-induced systemic hydration of vocal folds over a range of phonation conditions.

Predicting phonation conditions that are benign to voice health remains a biomechanically relevant problem. Our objective is to provide insight into vocal fold (VF) hydration based on continuum-based VF models that are able to compute VF stresses during phonation and a scheme for the extraction and generalization of such computational data based on the principle of linear superposition. Because VF tissue is poroelastic, spatial gradients of VF hydrostatic stresses computed for a given phonation condition determine VF interstitial fluid flow. The present approach transforms, based on linear superposition principles, the computed interstitial fluid velocities at the particular phonation to those at an arbitrary phonation condition. Intersititial fluid flow characteristics for a range of phonation conditions are compared. For phonation conditions with no or moderate collision, no dehydration per vibration cycle is predicted throughout the VF. For more severe collision conditions, tissue dehydration is restricted to a region close to the glottal surface. Interstitial fluid displacement in the VF is found to be heterogeneous and strongly dependent on the phonation condition. A phonation condition is found to exist for which dehydration peaks. The proposed method significantly expands the scope and relevance of conducting isolated numerical simulations of VF vibration.

Probing the QCD phase diagram with fluctuations

The relevance of higher order cumulants of conserved charges for the analysis of freeze-out and critical conditions in heavy ion collisions at LHC and RHIC is discussed. Using properties of $O(4)$ scaling functions, the generic structure of these higher cumulants at vanishing baryon chemical potential is discussed. Chiral model calculations are then used to study their properties at non-zero baryon chemical potential. It is argued that the rapid variation of sixth and higher order cumulants at the phase boundary may be used to explore the QCD phase diagram in experiment. Moreover, results for the Polyakov loop susceptibilities in SU(3) lattice gauge theory as well as in (2+1) flavor lattice QCD are discussed. An analysis of the ratios of susceptibilities indicates that the deconfinement transition is reflected in characteristic modifications of these ratios.

Kinetic freeze-out, particle spectra, and harmonic-flow coefficients from mode-by-mode hydrodynamics

The kinetic freeze-out for the hydrodynamical description of relativistic heavy ion collisions is discussed using a background-fluctuation splitting of the hydrodynamical fields. For a single event, the particle spectrum, or its logarithm, can be written as the sum of background part that is symmetric with respect to azimuthal rotations and longitudinal boosts and a part containing the contribution of fluctuations or deviations from the background. Using a complete orthonormal basis to characterize the initial state allows one to write the double differential harmonic flow coefficients determined by the two-particle correlation method as matrix expressions involving the initial fluid correlations. We discuss the use of these expressions for a mode-by-mode analysis of fluctuating initial conditions in heavy ion collisions.

Gas‐Phase Synthesis of the Benzyl Radical (C6H5CH2)

AbstractDicarbon (C2), the simplest bare carbon molecule, is ubiquitous in the interstellar medium and in combustion flames. A gas‐phase synthesis is presented of the benzyl radical (C6H5CH2) by the crossed molecular beam reaction of dicarbon, C2(X1Σg+, a3Πu), with 2‐methyl‐1,3‐butadiene (isoprene; C5H8; X1A′) accessing the triplet and singlet C7H8 potential energy surfaces (PESs) under single collision conditions. The experimental data combined with ab initio and statistical calculations reveal the underlying reaction mechanism and chemical dynamics. On the singlet and triplet surfaces, the reactions involve indirect scattering dynamics and are initiated by the barrierless addition of dicarbon to the carbon–carbon double bond of the 2‐methyl‐1,3‐butadiene molecule. These initial addition complexes rearrange via multiple isomerization steps, leading eventually to the formation of C7H7 radical species through atomic hydrogen elimination. The benzyl radical (C6H5CH2), the thermodynamically most stable C7H7 isomer, is determined as the major product.

Gas‐Phase Synthesis of the Benzyl Radical (C6H5CH2)

Dicarbon (C2 ), the simplest bare carbon molecule, is ubiquitous in the interstellar medium and in combustion flames. A gas-phase synthesis is presented of the benzyl radical (C6 H5 CH2 ) by the crossed molecular beam reaction of dicarbon, C2 (X(1) Σg (+) , a(3) Πu ), with 2-methyl-1,3-butadiene (isoprene; C5 H8 ; X(1) A') accessing the triplet and singlet C7 H8 potential energy surfaces (PESs) under single collision conditions. The experimental data combined with ab initio and statistical calculations reveal the underlying reaction mechanism and chemical dynamics. On the singlet and triplet surfaces, the reactions involve indirect scattering dynamics and are initiated by the barrierless addition of dicarbon to the carbon-carbon double bond of the 2-methyl-1,3-butadiene molecule. These initial addition complexes rearrange via multiple isomerization steps, leading eventually to the formation of C7 H7 radical species through atomic hydrogen elimination. The benzyl radical (C6 H5 CH2 ), the thermodynamically most stable C7 H7 isomer, is determined as the major product.

Reactions of Size-Selected Copper Cluster Cations and Anions with Nitric Oxide: Enhancement of Adsorption in Coadsorption with Oxygen

Reactions of size-selected Cu(n)(±) and Cu(n)O(m)(±) (n = 3-19, m ≤ 9) clusters with NO were investigated in the near-thermal energy region under single collision conditions using a tandem-type mass spectrometer with two ion-guided cells. Oxygen atoms preadsorbed on the cluster can significantly enhance the NO adsorption probability and cause additional reactions. NO adsorption is observed particularly for anionic copper cluster dioxides, Cu(n)O2(-) (n ≥ 8), followed by the release of a Cu atom from Cu(n)O2(-) (n = 8, 10, and 12), which suggests that NO adsorbs strongly, i.e., dissociatively on these clusters. Density functional theory calculations support that dissociative adsorption of NO occurs in the reaction of Cu8O2(-) under the present experimental conditions. On the other hand, NO oxidation proceeds in reactions of oxygen-rich cluster cations such as Cu4O3(+), Cu6O5(+), Cu9O7(+), and Cu11O8(+).

Oxygen–Sulfur Exchange and the Gas-Phase Reactivity of Cobalt Sulfide Cluster Anions with Molecular Oxygen

We present here a study of gas-phase reactivity of cobalt sulfide cluster anions Co(m)S(n)(-) with molecular oxygen. Nascent Co(m)S(n)(-) clusters were prepared via a laser ablation source and reacted with oxygen in a fast flow reactor under thermal collision conditions. We chose (18)O2 in place of (16)O2 to avoid mass degeneration with sulfur, and a time-of-flight (TOF) mass spectrometer was used to detect the cluster distributions in the absence and presence of the reactant. It was found that oxygen-sulfur exchange occurs in the reactions for those with specific compositions (CoS)(n)(-) and (CoS)(n)S(-) (n = 2-5) according to a consistent pathway, "Co(m)S(n)(-) + (18)O2 → Co(m)S(n-1)(18)O(-) + S(18)O". Typically, for "Co2S2(-) + (18)O2" we have calculated the reaction coordinates by employing the density functional theory (DFT), where both the oxygen-sulfur exchange and SO molecule release are thermodynamically and kinetically favorable. It is noteworthy that the reaction with molecular oxygen (triplet ground state) needs to overcome a spin excitation as well as a large O-O activation energy. This study sheds light on the activation of molecular oxygen by cobalt sulfides on one hand and also provides insight into the regeneration mechanism of cobalt oxides from the counterpart sulfides in the presence of oxygen gas on the other hand.

Fluid dynamics with saturated minijet initial conditions in ultrarelativistic heavy-ion collisions

Using next-to-leading order perturbative QCD and a conjecture of saturation to suppress the production of low-energy partons, we calculate the initial energy densities and formation times for the dissipative fluid dynamical evolution of the quark–gluon plasma produced in ultrarelativistic heavy-ion collisions. We identify the model uncertainties and demonstrate the predictive power of the approach by a good global agreement with the measured centrality dependence of charged particle multiplicities, transverse momentum spectra and elliptic flow simultaneously for the Pb+Pb collisions at the LHC and Au+Au at RHIC. In particular, the shear viscosity in the different phases of QCD matter is constrained in this new model simultaneously by all these data.

On the formation of ethynylbiphenyl (C14D5H5; C6D5C6H4CCH) isomers in the reaction of D5-phenyl radicals (C6D5; X2A1) with phenylacetylene (C6H5C2H; X1A1) under single collision conditions

Reaction dynamics of the D5-phenyl radical with phenylacetylene were investigated in crossed molecular beams at a collision energy of 120.7kJmol−1 supported by ab initio calculations. The reaction displays indirect, complex forming scattering dynamics, and adduct formation, with D5-phenyl attacking the phenyl ring of phenylacetylene at the ortho, meta and para positions over small entrance barriers. The adduct (C6D5C8H6) undergoes hydrogen emission through tight exit transition states of 34–47kJmol−1 above the separated products. The phenyl addition–hydrogen elimination mechanism produces various ethynylbiphenyls exoergically by 25–38kJmol−1. No phenanthrene was formed under our experimental conditions.

An experimental and theoretical study of electron impact ionization and dissociative electron attachment to trimethyl borate

We report a combined experimental and theoretical study of electron impact ionization (EII) to B(OCH3)3 molecule. The electron impact ionization experiment was carried out using crossed beams technique under single collision conditions with mass spectrometric analysis of the ions. The experimentally determined ionization energy of B(OCH3)3 is 10.33±0.15eV. The appearance energies of dominant fragment ions formed via OCH3 and CH3 group cleavages were determined. The experiment was supported by complex energy calculation using G3 quantum chemical method to determine the ionization energy and the reaction enthalpies leading to the experimentally observed products. Additionally, dissociative electron attachment to B(OCH3)3 has been investigated. We were able to detect only one negative ion (OCH3)− at very low intensity formed via broad resonance at 7eV.

Consecutive Oxygen-for-Sulfur Exchange Reactions between Vanadium Oxide Cluster Anions and Hydrogen Sulfide

Vanadium oxide cluster anions Vm(16)On(-) and Vm(18)On(-) were prepared by laser ablation and reacted with hydrogen sulfide (H2S) in a fast flow reactor under thermal collision conditions. A time-of-flight mass spectrometer was used to detect the cluster distributions before and after the interactions with H2S. The experiments suggest that the oxygen-for-sulfur (O/S) exchange reaction to release water was evidenced in the reactor for most of the cluster anions: VmOn(-) + H2S → VmOn-1S(-) + H2O. For reactions of clusters VO3(-) and VO4(-) with H2S, consecutive O/S exchange reactions led to the generation of sulfur containing vanadium oxide cluster anions VO3-kSk(-) (k = 1-3) and VO4-kSk(-) (k = 1-4). Density functional theory calculations were performed for the reactions of VO3-4(-) with H2S, and the results indicate that the O/S exchange reactions are both thermodynamically and kinetically favorable, which supports the experimental observations. The reactions of VmOn(+) cluster cations with H2S have been reported previously (Jia, M.-Y.; Xu, B.; Ding, X.-L.; Zhao, Y.-X.; He, S.-G.; Ge, M.-F. J. Phys. Chem. C 2012, 116, 9043), and this study of cluster anions provides further new insights into the transformations of H2S over vanadium oxides at the molecular level.

1A1-T03 形状を考慮した全方向搬送ロボットの経路計画(作業移動ロボット)

This paper describes a path planning that considers the robot shape with a transported object for an omnidirectional transportation mobile robot. The path planning considering the robot shape is usually treated in a Configuration Space. However, a mapping to the Configuration Space needs much computational complexity to check the collision of the robot and obstacles. Therefore, we propose a method for reducing the computational complexity using the domain decomposition according to the collision condition that the robot posture depends on or not. The effectiveness of the path generated by combining a distance transform and a potential method is verified through some simulations.