Monte Carlo modeling of production of three alpha-particles in low energy n +12C interactions

To describe [Formula: see text] interactions with production of three [Formula: see text]-particles at incident neutron kinetic energy of 14 MeV in a nuclear (photo) emulsion, a Monte Carlo model is proposed for four channels of decay of an excited carbon-12 nucleus into three [Formula: see text]-particles. The Monte Carlo calculation results describe well the experimental data on the distribution of the angle between the three-dimensional momenta of all pairs of [Formula: see text]-particles in a collision event, on the distribution of the angle between the projections of the momentum vectors of all pairs of [Formula: see text]-particles in collision event on each of the coordinate planes, on the distribution of the sum of the kinetic energies of all pairs of [Formula: see text]-particles in a collision event, and the distribution of projections of the momenta of [Formula: see text]-particles on the coordinate planes. The best agreement of the Monte Carlo model results with the experimental data is achieved if the direct decay [Formula: see text] and decay through the formation of an intermediate beryllium nucleus [Formula: see text] are generated with equal probabilities, while the excitation energies of 3.04 MeV, 1.04 MeV, and 0.1 MeV for the beryllium nucleus are generated with relative weights of 75%, 15%, and 10%, respectively.

Tuning of NASA Standard Breakup Model for Fragmentation Events Modelling

The continuous growth of space debris motivates the development and the improvement of tools that support the monitoring of a more and more congested space environment. Satellite breakup models play a key role to predict and analyze orbital debris evolution, and the NASA Standard Breakup Model represents a widely used reference, with current activities relevant to its evolution and improvements especially towards fragmentation of small mass spacecraft. From an operational perspective, an important point for fragmentation modelling concerns the tuning of the breakup model to achieve consistency with orbital data of observed fragments. In this framework, this paper proposes an iterative approach to estimate the model inputs, and in particular, the parents’ masses involved in a collision event. The iterative logic exploits the knowledge of Two Line Elements (TLE) of the fragments at some time after the event to adjust the input parameters of the breakup model with the objective of obtaining the same number of real fragments within a certain tolerance. Atmospheric re-entry is accounted for. As a result, the breakup model outputs a set of fragments whose statistical distribution, in terms of number and size, is consistent with the catalogued ones. The iterative approach is demonstrated for two different scenarios (i.e., catastrophic collision and non-catastrophic collision) using numerical simulations. Then, it is also applied to a real collision event.

FOREST unbiased Galactic plane imaging survey with the Nobeyama 45 m telescope (FUGIN). VIII. Possible evidence of cloud–cloud collisions triggering high-mass star formation in the giant molecular cloud M 16 (Eagle Nebula)

M 16, the Eagle Nebula, is an outstanding H ii region which exhibits extensive high-mass star formation and hosts remarkable “pillars.” We herein obtained new 12COJ = 1–0 data for the region observed with NANTEN2, which were combined with the 12COJ = 1–0 data obtained using the FOREST unbiased galactic plane imaging with Nobeyama 45 m telescope (FUGIN) survey. These observations revealed that a giant molecular cloud (GMC) of ∼1.3 × 105 M⊙ is associated with M 16, which extends for 30 pc perpendicularly to the galactic plane, at a distance of 1.8 kpc. This GMC can be divided into the northern (N) cloud, the eastern (E) filament, the southeastern (SE) cloud, the southeastern (SE) filament, and the southern (S) cloud. We also found two velocity components (blueshifted and redshifted components) in the N cloud. The blueshifted component shows a ring-like structure, and the redshifted one coincides with the intensity depression of the ring-like structure. The position–velocity diagram of the components showed a V-shaped velocity feature. The spatial and velocity structures of the cloud indicated that two different velocity components collided with each other at a relative velocity of 11.6 km s−1. The timescale of the collision was estimated to be ∼4 × 105 yr. The collision event reasonably explains the formation of the O9V star ALS 15348, as well as the shape of the Spitzer bubble N19. A similar velocity structure was found in the SE cloud, which is associated with the O7.5V star HD 168504. In addition, the complementary distributions of the two velocity components found in the entire GMC suggested that the collision event occurred globally. On the basis of the above results, we herein propose a hypothesis that the collision between the two components occurred sequentially over the last several 106 yr and triggered the formation of O-type stars in the NGC 6611 cluster in M 16.

Fast Fragmentation During Surface-Induced Dissociation: An Examination of Peptide Size and Structure

We present the results of direct dynamics simulations of surface-induced dissociation for protonated versions of A$_\mathrm{n}$K, KA$_\mathrm{n}$ (n = 1, 3, and 5), AcA$_\mathrm{7}$K, and AcKA$_\mathrm{7}$ for collisions with a fluorinated self-assembled monolayer surface. We focus on elucidating fast fragmentation events, which takes place in coincidence with the collision event. Such events generate a large number of products, and hence, are not easily understood through chemical intuition. Our simulations show distinct differences between the A$_{\mathrm{n}}$K/AcA$_\mathrm{7}$K and KA$_{\mathrm{n}}$/AcKA$_7$ series of peptides, with the former being more reactive, and the latter more selective. Backbone rearrangements and sidechain fragmentation are also seen.<br>

Fast Fragmentation During Surface-Induced Dissociation: An Examination of Peptide Size and Structure

We present the results of direct dynamics simulations of surface-induced dissociation for protonated versions of A$_\mathrm{n}$K, KA$_\mathrm{n}$ (n = 1, 3, and 5), AcA$_\mathrm{7}$K, and AcKA$_\mathrm{7}$ for collisions with a fluorinated self-assembled monolayer surface. We focus on elucidating fast fragmentation events, which takes place in coincidence with the collision event. Such events generate a large number of products, and hence, are not easily understood through chemical intuition. Our simulations show distinct differences between the A$_{\mathrm{n}}$K/AcA$_\mathrm{7}$K and KA$_{\mathrm{n}}$/AcKA$_7$ series of peptides, with the former being more reactive, and the latter more selective. Backbone rearrangements and sidechain fragmentation are also seen.<br>

Fast Fragmentation During Surface-Induced Dissociation: An Examination of Peptide Size and Structure

We present the results of direct dynamics simulations of surface-induced dissociation for protonated versions of A$_\mathrm{n}$K, KA$_\mathrm{n}$ (n = 1, 3, and 5), AcA$_\mathrm{7}$K, and AcKA$_\mathrm{7}$ for collisions with a fluorinated self-assembled monolayer surface. We focus on elucidating fast fragmentation events, which takes place in coincidence with the collision event. Such events generate a large number of products, and hence, are not easily understood through chemical intuition. Our simulations show distinct differences between the A$_{\mathrm{n}}$K/AcA$_\mathrm{7}$K and KA$_{\mathrm{n}}$/AcKA$_7$ series of peptides, with the former being more reactive, and the latter more selective. Backbone rearrangements and sidechain fragmentation are also seen.<br>

Shattering During Surface-Induced Dissociation: An Examination of Peptide Size and Structure

We present the results of direct dynamics simulations of surface-induced dissociation for A_nK, KA_n (n = 1, 3, and 5), AcA₇K, and AcKA₇ for collisions with a fluorinated self-assembled monolayer surface. Our focus is on elucidating shattering fragmentation events, which takes place in coincidence with the collision event and frequently occurs in a charge remote fashion. Shattering events typically generate a large number of fragmentation products, and hence, are not easily understood through chemical intuition. Our simulations show distinct differences between the A_nK/AcA₇K and KA_n/AcKA₇ series of peptides, with the former being more reactive, while the latter is more selective regarding the type of bond that will break. In addition, we examine the possible backbone rearrangements seen as well as sidechain fragmentation.