Collision Mode Research Articles

Inclusive diffractiveηcproduction in pp, pA, and AA modes at the LHC

In this paper, the inclusive Pomeron-Pomeron, Reggeon-Reggeon, Pomeron-Reggeon as well as gluon-Pomeron(-Reggeon) and photon-Pomeron(-Reggeon) interactions for the $\rm \eta_{c}$ at the LHC energies have been examined in proton-proton, proton-nucleus and nucleus-nucleus collision modes. The cross section has been computed based on the NRQCD factorization and Regge theory formalism. The cross exchange of Pomeron-Reggeon contribution is important in $\rm pp$ and $\rm pA$ modes. The Pomeron-Pomeron contribution is significant in $\rm AA$ mode. The Pomeron contribution is considerable for $\rm AA$ and $\rm pA$ modes in single diffractive process where $\rm A$ undergoes the diffractive process. Reggeon contribution is sizable in $\rm pp$ and $\rm pA$ modes where $\rm p$ only undergoes the diffractive process. The Pomeron and Reggeon contributions in photon-Pomeron and-Reggeon process remain smaller than that of gluon-Pomeron and-Reggeon processes. Our results show that the experimental study of Reggeon, Pomeron and their cross exchange can be carried out in certain kinematic windows with the specific choice of the mode at the LHC. The investigation can be useful to better constrain the Reggeon and Pomeron parton content. The inclusive process serves as the background to related exclusive processes which should be predicted.

Underwater bubble collapse on a ridge-patterned structure

This experimental study reports the collapse of an underwater bubble near a patterned structure with ridges and grooves. When a bubble is generated by a spark above a ridge, the entire bubble collapses toward the structure after its full expansion, or it is split into two smaller bubbles because of a radial jet induced by bubble contraction. These distinct collapse modes are dependent on the surface geometry of the structure and determined by the contracting speed of a bubble part inside the cross section of an adjacent groove. For a bubble that collapses in a groove, water flows induced from the tops of adjacent ridges collide with each other in the middle of the groove cross section, and this collision occurs if the effective width of the groove is small enough. For the bubble-splitting radial jet mode on the ridge and the collision mode in the groove, some energy of the bubble is lost during its contraction and, accordingly, the strength of the re-entrant jet toward the surface is weakened. Thus, these modes may be effective for reducing erosion on the structure surface, which is supported by our simple experiment for damage assessment.

Numerical study of collision modes of multi-core compound droplets in simple shear flow

Collisions of multi-core compound droplets have generated substantial interest in recent years because of their applications in the industry and academia. This study uses the front-tracking method to simulate the transition between the two collision modes of multi-core compound droplets in a simple shear flow. Compound droplets initially assumed identical have two sub-droplets of equal size. Given the shear flow, the droplets collide with one another and behave in two main modes, namely, passing-over and reversing. In the passing-over mode, the droplets pass over one another after coming into contact. The reversing mode appears with two compound droplets returning to their initial sides after the collision. During collision, the sub-droplets circulate approximately at the center of their enclosing outer droplets. Some parameters, including capillary number Ca, viscosity ratios μio and μmo, radius ratio Rio of the sub-droplets to the outer droplets, and sub-droplet angle a0, are investigated to determine their impact on these modes of collisions. We find that the transition from a reversing to passing-over mode occurs when we increase the value of Ca from 0.01 to 0.63}, {tiRio from 0.20 to 0.475, and μio and μmo in the range of 0.16-6.3. However, an increase in the value of a0 between -75° and 90° leads to a change from a passing-over to reversing mode. Diagrams of the colliding modes are also presented in this research.

Determination of Total Selenium and Extractability of Selenium in Commercially-Available Dietary Supplements by Inductively Coupled Plasma - Mass Spectrometry (ICP-MS)

Upper limits for the supplementation of micronutrients are still undecided in many European countries. These limits are of particular interest for selenium because of the narrow range of acceptable intake. Standard analytical protocols to check for compliance must be consistent for a variety of dietary supplements. Emerging products in the evolving market for dietary supplements and over-the-counter (OTC)-medications must be factored in as well. The ICP-MS determination of selenium is well established for scientific research, but a systematic comparison of the operation modes for a realistic set of samples is still missing. In this manuscript, five common cell-techniques for interference removal were approved by a certified reference material (CRM) and applied to a variety of 28 different dietary supplements after microwave digestion. The comparison reveals these operation modes are less consistent for some supplements than for the CRM, whereas 78Se in collision mode was identified as being the most robust. The results for the supplements varied within tolerable limits from the labeled dosage. Extraction with TRIS-buffer was employed as a minimally invasive method to determine the impact in comparison to the total selenium quantification, showing variation among the labeled species (selenomethionine (∼100%), methyl-seleno-cysteine (94%), selenite and selenate (60–100%), selenized yeast (11–28%), spirulina algae (70%)).

Study on Coagulation Kinetics of Disk-like Particles under Simple Shear Flow.

In this study, a theoretical study is carried out on the collision of two disk-like particles to understand the coagulation of disk-like particles suspended in liquid under a shear flow. The diameter of the particle is fixed at 2 μm while the length is varied so that the aspect ratio (length/diameter) varies from 0.1 to 0.4. The liquid viscosity is changed from 0.01 to 1 Pa s. The minimum Peclet number is 10, and the Brownian motion is considered to be negligible. Both hydrodynamic and van der Waals interactions are included in tracking the position and the orientation of each particle. The Hamaker constant is fixed at 1.06 × 10-20 J. The boundary integral formulation is used to calculate the hydrodynamic interaction. To obtain the kinetic constant of coagulation, the time-independent orientation distribution function for a particle is obtained under the noninteracting condition. The kinetic constant of coagulation is obtained by considering the presence of collision between two particles initially separated by a long distance, the orientations of two particles, and the flux of the liquid flow. The result shows that the kinetic constant of coagulation is reduced to approximately 1/3 of the value for the noninteracting particles when the viscosity is 1 Pa·s. As collision modes, side-side, face-edge, side-edge, and edge-edge are considered. The edge-edge mode is frequently observed in the given range of the aspect ratio. The collision mode does not change much from the noninteracting case except for the side-side mode.

Interaction of Liquid Droplets in Gas and Vapor Flows

We investigated the conditions, characteristics, and outcomes of liquid droplet interaction in the gas medium using video frame processing. The frequency of different droplet collision outcomes and their characteristics were determined. Four interaction regimes were identified: bounce, separation, coalescence, and disruption. Collision regime maps were drawn up using the Weber, Reynolds, Ohnesorge, Laplace, and capillary numbers, as well as dimensionless linear and angular parameters of interaction. Significant differences were established between interaction maps under ideal conditions (two droplets colliding without a possible impact of the neighboring ones) and collision of droplets as aerosol elements. It was shown that the Weber number could not be the only criterion for changing the collision mode, and sizes and concentration of droplets in aerosols influence collision modes. It was established that collisions of droplets in a gaseous medium could lead to an increase in the liquid surface area by 1.5–5 times. Such a large-scale change in the surface area of the liquid significantly intensifies heat transfer and phase transformations in energy systems.

Parametric study of the collision modes of compound droplets in simple shear flow

Compound droplet collision has been found in various industrial and academic applications. Such colliding phenomena of two droplets in simple shear flow are numerically resolved by a front-tracking technique. Initially, each compound droplet, assumed cylindrical, contains one concentric inner droplet. They are separated at the lateral and vertical intervals denoted by Δx0 and Δy0. Because of the shear flow, the compound droplets interact with each other and exhibit three collision modes: passing-over, merging (i.e. coalescence) and reversing. These modes and their transition are affected by many parameters including the Reynolds Re and Capillary Ca numbers (based on the properties of the outer fluid), the viscosity ratios μ13 and μ23, the interfacial tension ratio σ12 of the inner to outer interfaces, the ratio of the radii of the inner to outer droplets R12 and the initial distance between them (in terms of Δx0 and Δy0). It is found that from a merging mode, decreasing Re from 2.51 to a value less than or equal to 1.0 induces a transition to a reversing mode, whereas, increasing Ca from 0.005 to a value greater than or equal to 0.04 leads to a transition to a passing-over mode. A transition from the merging to passing-over modes also appears when varying μ23 in the range of 0.1–10.0 or varying R12 in the range of 0.2–0.8. A transition from a passing-over mode to a reversing one is available when increasing Δx0 or decreasing Δy0. Three modes of collision all occur when μ13 is varied in the range of 0.1–10.0. However, the variation of σ12 does not induce any transition between different modes. Several phase diagrams in terms of Re versus Ca, or Δx0 versus Δy0 are also proposed to show the transitions between these modes.

Interaction of Water and Suspension Droplets during Their Collisions in a Gas Medium

The results of the experimental studies of collisions of water and water suspension droplets in a gas medium using high-speed video recording and specialized software for tracking the initial droplets and the resulting fragments were presented. Videograms that illustrate the typical drop collision modes (bounce , separation, coalescence, and disruption) were given. The effects of droplet collisions under free fall conditions in air at ambient temperature (20°C) and during their motion in the counter-flows of heated air (500°C) and combustion products (800–850°C) were considered. A statistical analysis of collision modes was performed. The dependences of their occurrence on some factors (size, rate, collision angle, and criterial expressions that include the dimensionless linear and angular interaction parameters) were presented. The ranges of fluid surface area during fragmentation and separation of droplets due to collisions in gas media with different temperatures were determined.

Circling in on Convective Organization

AbstractCold pools (CPs) contribute to convective organization. However, it is unclear by which mechanisms organization occurs. By using a particle method to track CP gust fronts in large eddy simulations, we characterize the basic collision modes between CPs. Our results show that CP interactions, where three expanding gust fronts force an updraft, are key at triggering new convection. Using this, we conceptualize CP dynamics into a parameter‐free mathematical model: circles expand from initially random points in space. Where two expanding circles collide, a stationary front is formed. However, where three expanding circles enclose a single point, a new expanding circle is seeded. This simple model supports three fundamental features of CP dynamics: precipitation cells constitute a spatially interacting system, CPs come in generations, and scales steadily increase throughout the diurnal cycle. Finally, this model provides a framework for how CPs act to cause convective self‐organization, clustering, and extremes.

Extending the constraint for axion-like particles as resonances at the LHC and laser beam experiments

We study the discovery potential of axion-like particles (ALP), pseudo-scalars weakly coupled to Standard Model fields, at the Large Hadron Collider (LHC). Our focus is on ALPs coupled to the electromagnetic field, which would induce anomalous scattering of light-by-light. This can be directly probed in central exclusive production of photon pairs in ultra-peripheral collisions at the LHC in proton and heavy-ion collisions. We consider non-standard collision modes of the LHC, such as argon-argon collisions at sNN=7 TeV and proton-lead collisions at sNN=8.16 TeV, to access regions in the parameter space complementary to the ones previously considered for lead-lead and proton-proton collisions. In addition, we show that, using laser beam interactions, we can constrain ALPs as resonant deviations in the refractive index induced by anomalous light-by-light scattering effects. If we combine the aforementioned approaches, ALPs can be probed in a wide range of masses from the eV scale up to the TeV scale.

Research on the Effect of Tree Barriers on Rockfall Using a Three-Dimensional Discontinuous Deformation Analysis Method

On rockfall slopes, trees can play a natural and efficient protective role in preventing the occurrence of rockfall disasters. This paper presents a study on the tree barrier effect on rockfall based on a three-dimensional discontinuous deformation analysis (3D DDA) method. The tree barrier effect on rockfall is studied considering the 3D spatial effect of rockfall movement and the 3D spatial distribution of trees. The basic movement forms and collision modes of rockfall related to the tree barrier are classified, and the impact factors of tree arrangements on rockfall are proposed. The contact mechanism employed in the 3D DDA method is illustrated, and the accuracy of the 3D DDA rockfall simulation is verified by comparing with the results obtained from laboratory experiments. Numerical examples are conducted to study the effect of the tree barrier on rockfall, and general laws are derived by analyzing the variation of kinetic energies and motion trajectories of moving blocks. The results show that the 3D DDA method can effectively predict the 3D motion behaviors of rockfall and assess the tree barrier effect. Furthermore, a reasonable arrangement of trees or a combination of protective facilities and trees can prevent or mitigate the rockfall hazards.

Determination of polybrominated diphenyl ethers in fish tissue using gas chromatography-isotope dilution tandem inductively coupled plasma mass spectrometry with a mass-shift mode

Gas chromatography inductively coupled plasma triple quadrupole mass spectrometry (GC-ICP-MS/MS) operated in N2O reaction mode (mass-shift mode) was established for the analysis of six congeners of polybrominated diphenyl ethers (PBDEs): BDE 28, BDE 47, BDE 99, BDE 100, BDE 153 and BDE 154 in fish samples. The spectral interference on the determination of PBDEs was eliminated by measuring the product ion (BrO+) instead of traditional methods measuring Br+. After comparing the signal intensities of the three reaction gases (O2, H2, and N2O), the highest sensitivity was found using N2O as the reaction gas. The results showed that bromine is an element that suffers from strong spectral overlap in ICP, mainly from Ar-based polyatomic interferences. Spectral interference was assessed by measuring the bromine isotope ratio of 81Br+ and 79Br+ of the six priority PBDEs in the He collision mode and N2O reaction mode, respectively. In the conventional He collision mode, the relative isotope ratio of 79Br/81Br (the measured isotope ratio to the natural isotope ratio) of the analytes ranged from 0.955 to 0.965, which proves that using He as the collision gas cannot completely eliminate the spectral interference. In the N2O reaction mode, the relative isotope ratio of 79Br/81Br ranged from 0.991 to 1.004, demonstrating that spectral interference can be fully eliminated. Samples were processed using the modified QuEChERs method with detection limits ranging from 0.03 to 0.09 ng g−1 with a relative standard deviation of less than 3%. Six priority PBDEs in the NIST reference materials SRM 1947 (frozen fish tissue homogenate) were determined by mass-shift mode to verify this conclusion. No statistically significant difference was observed between the measured value and the certified value, with recoveries between 95% and 114%. The method was applied to the analysis of PBDEs in marine fish samples and five PBDEs were observed (BDE28,BDE-47, BDE-99, BDE-100 and BDE-153) at concentrations ranging from 0.04 to 0.54 ng g−1.

Investigation on propagation characteristics of rotating detonation wave in a radial-flow turbine engine combustor model

In this experiment, the propagation characteristics of rotating detonation waves in a radial-flow turbine engine combustor model were investigated. An annular combustor, with an inner diameter of 94 mm and an outer diameter of 106 mm was used as the rotating detonation combustor, and the H2 and air were separately injected into the combustor. The stability of the detonation wave propagation with and without a guide vane at the exit of the combustor was analyzed. The velocity of the detonation wave for the guide vane tests is higher than that of no guide vane tests, and the guide vane has a significant effect on the oscillating pressure. For the no guide vane tests, only the two-wave collision mode of detonation wave is obtained for all the equivalence ratios, and there is an unstable phenomenon of the collision point displacement. For the guide vane tests, the detonation-wave gradually stabilizes with the increase of the equivalence ratio, and then the stability gradually weakens. The phenomenon of the low-frequency pressure fluctuation occurs with the equivalence ratio larger than 1, and the fluctuation frequency is lower than 400 Hz.

Continental lithospheric-scale subduction versus crustal-scale underthrusting in the collision zone: Numerical modeling

Two distinct styles of continental collision are observed in nature, i.e. lithospheric-scale subduction versus crustal-scale underthrusting. The former refers to a collision scenario where the lower plate subducts below the lithospheric mantle of the overriding plate, whereas the latter is characterized by the underthrusting of the subducting plate beneath the crust of the overriding plate. Systematic numerical models were constructed to study the dynamics of these two different collision modes. The model results indicate that low convergence rate and cold overriding plate contribute to the lithospheric-scale subduction, which incorporates limited shortening of the overriding lithosphere during collision. In contrast, the crustal-scale underthrusting requires relatively high convergence rate and hot/weak overriding plate, in which the thickened lithospheric mantle of the overriding plate is progressively delaminated from the overlying crust and is replaced by the sub-horizontally underthrusted plate. The model results were systematically compared with four ongoing collisional orogens along the Alpine–Himalayan belt, i.e. the central-western Alps, the East Anatolian plateau, the Zagros–Iranian plateau, and the southern Tibetan plateau. It indicates that the lithospheric-scale subduction is widely observed and generally consistent with the natural orogens, for example, the Alps, Anatolia, and Zagros. On the other hand, the crustal-scale underthrusting is reconciled with the India–Asia collision zone, with respect to the geodynamic conditions, crustal-lithospheric structure, as well as the uplift history.

Germanium speciation using liquid chromatography-inductively coupled plasma-triple quadrupole mass spectrometry: Germanium in biological and chemical leaching solutions of fine-grained residues from copper smelting

A new method for the speciation analysis of inorganic germanium (Ge(OH)4), monomethylgermanium (MMGe) and dimethylgermanium (DMGe) in complex acidic aqueous leachates by liquid chromatography coupled to inductively coupled plasma mass spectrometry (LC-ICP-MS) was developed. The species are separated using anion exchange chromatography with tartrate added as complexing agent. When tartrate was added to the sample and the eluent chromatography was not affected by sulfate concentrations up to 100 mM. The He collision mode (MS/MS mode) removes polyatomic plasma- and matrix-based interferences, thus providing the selectivity in Ge speciation required for the complex samples. With LOQs of 62 ng L−1 (DMGe), 67 ng L−1 (MMGe) and 164 ng L−1 (Ge(OH)4) the method was sufficiently sensitive for the intended application. The developed method was applied to biological and chemical leachates of sulfidic flue dust from copper shale smelting (Theisen sludge). Only small amounts of methylated Ge species were determined next to inorganic Ge in these leachates.

Pair production of the lightest chargino at γγ-collider

Chargino pair production via photon–photon collision is investigated in the Minimal Supersymmetric Standard Model at a future linear collider. The process is computed using all the possible diagrams at the next-to-leading order, including box, triangle, and self-energy diagrams. The numerical analysis is carried out for the production rates of the lightest chargino pair in RNS, NS, mSUGRA, BB, and NUGM scenarios. These distinct benchmark models were introduced in the light of the LHC results presented at s=7–8 TeV. Among these scenarios, the RNS has the highest production rate for the γγ→χ˜1+χ˜1−. The partonic cross section reaches up to 3.94 pb at sˆ=310 GeV. The total convoluted cross section with the photon luminosity in a e+e− machine is calculated as a function of the center-of-mass energy up to 1 TeV. The convoluted cross section is ∼1.05 pb at s=350 GeV depending on the polarization of the initial electron and laser polarization. The RNS along with the BB scenarios are accessible at s=500 GeV with a γγ collision mode on e+e−-collider.

Hadronic production of the doubly charmed baryon via the proton\u2013nucleus and the nucleus\u2013nucleus collisions at the RHIC and LHC

We present a detailed discussion on the doubly charmed baryon Xi _{cc} production at the RHIC and LHC via the proton–nucleus (p–N) and nucleus–nucleus (N–N) collision modes. The extrinsic charm mechanism via the subprocesses g+crightarrow (cc)[n]+bar{c} and c+crightarrow (cc)[n]+g together with the gluon-gluon fusion mechanism via the subprocess g+grightarrow (cc)[n]+bar{c}+bar{c} have been taken into consideration, where the intermediate diquark is in [n]=[^1S_0]_mathbf{6}-state or [^3S_1]_{bar{mathbf{3}}}-state, respectively. Total and differential cross sections have been discussed under various collision energies. To compare with the Xi _{cc} production via proton-proton collision mode at the LHC, we observe that sizable Xi _{cc} events can also be generated via p–N and N–N collision modes at the RHIC and LHC. For examples, about 8.1times 10^7 and 6.7times 10^7Xi _{cc} events can be accumulated in p-Pb and Pb-Pb collision modes at the LHC within one operation year.

Multi-terrane structure controls the contrasting lithospheric evolution beneath the western and central\u2013eastern Tibetan plateau

The Tibetan plateau is manifested by contrasting along-strike lithospheric structures, but its formation mechanism and the relationship with the heterogeneous multi-terrane configuration is a challenging problem. Here we conduct systematic numerical modeling to explore the roles of width, density, and rheological properties of the multiple terranes in the lithospheric evolution of the Tibetan plateau, which reveals two distinct collision modes. In Mode-I, the lithospheric mantles of both the strong and weak terranes in the Tibetan plate are completely detached, followed by the underthrusting of Indian lithosphere beneath the whole plateau. Alternatively, Mode-II is characterized by full detachment of the weak terranes, but (partial) residue of the strong terranes during collision. These two contrasting modes, broadly consistent with the lithospheric structures of western and central–eastern Tibetan plateau, respectively, are strongly dependent on the along-strike variation of the width of the strong Lhasa–Qiangtang terranes.

Collision Incidents of Single Tetrahexahedral Platinum Nanocrystals Recorded by a Carbon Nanoelectrode

AbstractRecently, collision mode has been adopted to study the electrochemical or photoelectrochemical behavior of single particles touching and/or attaching on a biased ultramicroelectrode (UME). However, to correlate the reaction activity to the nanocrystal structure still remains challenging because of: (1) the uncontrolled structure and size of the single nanoparticle; (2) the uncertainty of one particle in each collision incident since the size of UME is much larger than that of the single nanoparticle. To these problems, we synthesized well‐defined convex tetrahexahedral platinum nanocrystals (THH Pt NC) with an average size of 30 nm and fabricated a carbon nanoelectrode through pyrolysis of butane. The current fluctuation caused by oxygen reduction reaction (ORR) during the single collision incident of THH Pt NC was detected by the carbon nanoelectrode. It is reasonable to use nanocrystals with well‐defined morphology and size in the collision experiments. However, the adoption of nanoelectrode will decrease the collision frequency and shorten the standing time of nanocrystals on the electrode surface. How to figure out the kinetics from the current fluctuations in the single collision incident still remains challenging.

Bc(*) -meson production via the proton-nucleus and the nucleus-nucleus collision modes at the colliders RHIC and LHC

In the paper, we make a comprehensive study on the hadroproduction of the $B_c (B_c^*)$ meson via the gluon-gluon fusion mechanism at the RHIC and LHC colliders. Total and differential cross sections via the proton-nucleus ($p$-N) and nucleus-nucleus (N-N) collision modes have been discussed under various collision energies. To compare with those via the proton-proton collision mode at the LHC, we observe that sizable number of $B_c (B_c^*)$-meson events can also be produced via the $p$-N and N-N collision modes at the RHIC and LHC. If assuming the spin-triplet $B^*_c$ meson directly decays to the spin-singlet $B_c$ meson with $100\%$ probability, $1.2 \times 10^5$ and $4.7 \times 10^5$ $B_c$-meson events can be produced via the $p$-Au and Au-Au collision modes at the RHIC in one operation year; $5.8 \times 10^6$ and $4.6 \times 10^6$ $B_c$-meson events can be produced via the $p$-Pb and Pb-Pb collision modes at the LHC in one operation year.