Fragmentation Probability Research Articles

Angular momentum effects on the decay modes of hot compound nuclei formed in 86Kr+134,138Ba reactions

The dependence of decay modes of hot compound nuclei formed in [Formula: see text]Kr[Formula: see text]Ba reactions on the angular momentum has been analyzed using the dynamical cluster-decay model. This has been done by analyzing the change of fragmentation potential, preformation probability, penetrability and cross-section as a function of the fragment mass number at various values of the angular momentum. The evaporation residue cross-section calculated using dynamical cluster-decay model has been compared with the measured one for the channels: [Formula: see text], [Formula: see text], [Formula: see text] for the decay of [Formula: see text]U[Formula: see text] and [Formula: see text] for [Formula: see text]U[Formula: see text]. The summed up fragment cross-sections for the light particles, intermediate mass fragments and fission fragments as a function of angular momentum have been studied which gives an idea for the change of reaction mechanism with angular momentum. The charge distribution of the fission fragment cross-section shows an odd–even staggering, i.e., the probability of even-Z fission fragments is relatively higher than others. The mass distributions obtained within the dynamical cluster-decay model for the decay of [Formula: see text]U[Formula: see text] are in conformity with mass distributions determined by means of the double kinetic-energy technique in literature. The position of the most probable channel has been found to be fixed to a constant atomic number instead of mass number.

Genetic and Ecogeographic Controls on Species Cohesion in Australia's Most Diverse Lizard Radiation.

AbstractSpecies vary extensively in geographic range size and climatic niche breadth. If range limits are primarily determined by climatic factors, species with broad climatic tolerances and those that track geographically widespread climates should have large ranges. However, large ranges might increase the probability of population fragmentation and adaptive divergence, potentially decoupling climatic niche breadth and range size. Conversely, ecological generalism in large-ranged species might lead to higher gene flow across climatic transitions, increasing species' cohesion and thus decreasing genetic isolation by distance (IBD). Focusing on Australia's iconic Ctenotus lizard radiation, we ask whether species range size scales with climatic niche breadth and the degree of population isolation. To this end, we infer independently evolving operational taxonomic units (OTUs), their geographic and climatic ranges, and the strength of IBD within OTUs based on genome-wide loci from 722 individuals spanning 75 taxa. Large-ranged OTUs were common and had broader climatic niches than small-ranged OTUs; thus, large ranges do not appear to simply result from passive tracking of widespread climatic zones. OTUs with larger ranges and broader climatic niches showed relatively weaker IBD, suggesting that large-ranged species might possess intrinsic attributes that facilitate genetic cohesion across large distances and varied climates. By influencing population divergence and persistence, traits that affect species cohesion may play a central role in large-scale patterns of diversification and species richness.

VANET: Optimal Cluster Head Selection Using Opposition Based Learning

Traffic related accidents and route congestions remain to dwell significant issues in the globe. To overcome this, VANET was proposed to enhance the traffic management. However, there are several drawbacks in VANET such as collision of vehicles, data transmission in high probability of network fragmentation and data congestion. To overcome these issues, the Enhanced Pigeon Inspired Optimization (EPIO) and the Adaptive Neuro Fuzzy Inference System (ANFIS) based methods have been proposed. The Cluster Head (CH) has been selected optimally using the EPIO approach, and then the ANFIS has been used for updating and validating the CH and also for enhancing the data transmission procedures. The dijkstra’s algorithm has been used for identifying the shortest path for data transmission. The results showcases that the proposed technique has attained the maximum Packet Delivery Ratios (PDRs) as 73.23% at a sensor radius of 130 m and 70.42% at a velocity of 10 km/h. Moreover, the proposed method has outperformed the existing technique in terms of the CH formation delay, the end to end delay and the PDR.

Modeling Biomass Burning Organic Aerosol Atmospheric Evolution and Chemical Aging

The changes in the concentration and composition of biomass-burning organic aerosol (OA) downwind of a major wildfire are simulated using the one-dimensional Lagrangian chemical transport model PMCAMx-Trj. A base case scenario is developed based on realistic fire-plume conditions and a series of sensitivity tests are performed to quantify the effects of different conditions and processes. Temperature, oxidant concentration and dilution rate all affect the evolution of biomass burning OA after its emission. The most important process though is the multi-stage oxidation of both the originally emitted organic vapors (volatile and intermediate volatility organic compounds) and those resulting from the evaporation of the OA as it is getting diluted. The emission rates of the intermediate volatility organic compounds (IVOCs) and their chemical fate have a large impact on the formed secondary OA within the plume. The assumption that these IVOCs undergo only functionalization leads to an overestimation of the produced SOA suggesting that fragmentation is also occurring. Assuming a fragmentation probability of 0.2 resulted in predictions that are more consistent with available observations. Dilution leads to OA evaporation and therefore reduction of the OA levels downwind of the fire. However, the evaporated material can return to the particulate phase later on after it gets oxidized and recondenses. The sensitivity of the OA levels and total mass balance on the dilution rate depends on the modeling assumptions. The high variability of OA mass enhancement observed in past field studies downwind of fires may be partially due to the variability of the dilution rates of the plumes.

Effect of cocrystallization due to bile acid on molecular‐ion sensitivity of biological phospholipids in Bi cluster time‐of‐flight secondary ion mass spectrometry measurements

Bi cluster time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) is a useful method for evaluating organic surfaces. However, its ability to detect large molecules is limited. One of the problems is that the sensitivities of macromolecules are lower than those of small molecules because larger molecules tend to exhibit lower ionization efficiencies and/or higher probabilities of fragmentation. Matrix‐enhanced (ME)‐SIMS is a sensitivity enhancement technique for intact molecular ions. The crystal structure of a mixed substance composed of an analyte and a matrix is known to affect the sensitivity of the analysis target. In this study, the effect of cocrystallization, which occurs due to the presence of bile acid, on the molecular‐ion sensitivity was investigated using Bi cluster TOF‐SIMS. Biological phospholipids and bile acids, which exhibit surfactant behaviors, were selected as the evaluated molecules and additives, respectively. The mass spectra indicated that the secondary‐ion yields of phospholipids with bile acid were substantially greater than those of the pristine lipid. Specifically, samples with an analyte/bile acid ratio of 1:100 achieved approximately 60–100‐fold sensitivity enhancement of [M + H]+ and [2M + H]+ molecular ions than the sensitivity achieved with the pristine samples. In the evaluation of molecular distribution, higher signal counts of intact ions were obtained from the cocrystallization area, although less‐fragmented ions were emitted from these regions. Consequently, the results indicate that the cocrystallization due to the presence of bile acid provides an effective crystal structure for facilitating emission of larger molecules.

Multiscale modeling of fragmentation in an electrospray plume

We present a 3D-particle-in-cell (PIC) approach to modeling electrospray plumes typical of those formed by externally wetted emitter devices. Numerical grid-resolution techniques suitable for capturing strong electric fields in the emitter region were explored, and grid refinement criteria were quantified. The molecular dynamics simulations of the EMIM−BF4 ionic liquid system were modeled to determine the fragmentation mechanism in the presence of an electric field and dimer temperature as well as to provide fragmentation rates for the PIC simulations. An energy analysis of the molecular dynamics (MD) fragmentation demonstrated that the key mechanism for dimer fragmentation corresponds to a decrease in the Coulomb energy between the cation and anion in the system and that dimers of temperatures 300 and 600 K are extremely stable for electric fields smaller than 1.5 V/nm. Using probabilities of fragmentation consistent with the MD simulations, we implemented a dimer fragmentation model in our PIC simulations. The ion energy distribution functions obtained from the PIC simulations were used to predict retarding potential analysis (RPA) curves that were compared directly to measurements. The sensitivity of the RPA shape to the fragmentation probability was found to be significant. By comparing predicted and measured RPA curves for both negative and positive operation modes, and the fact that dimers do not fragment for electric fields less than 0.6 V/nm, we conclude that fragmentation of dimers occurs spontaneously due to their high thermal energies.

Vibrational Relaxation of XUV-Induced Hot Ground State Cations of Naphthalene.

Time-resolved XUV-IR photoion mass spectroscopy of naphthalene conducted with broadband as well as with wavelength-selected narrowband XUV pulses reveals a rising probability of fragmentation characterized by a lifetime of 92 ± 4 fs. This lifetime is independent of the XUV excitation wavelength and is the same for all low appearance energy fragments recorded in the experiment. Analysis of the experimental data in conjunction with a statistical multistate vibronic model suggests that the experimental signals track vibrational energy redistribution on the potential energy surface of the ground-state cation. In particular, populations of the out-of-plane ring twist and the out-of-plane wave bending modes could be responsible for opening new IR absorption channels, leading to enhanced fragmentation.

Collective Movement and Collective Information Acquisition With Signaling

We consider a population of mobile agents able to make noisy observations of the environment and communicate their observation by production and comprehension of signals. Individuals try to align their movement direction with their neighbors. Besides, they try to collectively find and travel towards an environmental direction. We show that, when the fraction of informed individuals is small, by increasing the noise in communication, similarly to the Vicsek model, the model shows a discontinuous order-disorder transition with strong finite-size effects. In contrast, for a large fraction of informed individuals, it is possible to go from the ordered phase to the disordered phase without passing any phase transition. The ordered phase is composed of two phases separated by a discontinuous transition. Informed collective motion, in which the population collectively infers the correct environmental direction, occurs for a high fraction of informed individuals. When the fraction of informed individuals is low, the misinformed collective motion, where the population fails to find the environmental direction, becomes stable as well. Besides, we show that an amount of noise in the production of signals is more detrimental for the inference capability of the population and increases temporal fluctuations, the density fluctuations, and the probability of group fragmentation, compared to the same amount of noise in the comprehension.

RDRSA: A reactive defragmentation based on rerouting and spectrum assignment (RDRSA) for spectrum convertible elastic optical network

In this paper, a reactive defragmentation rerouting and spectrum assignment (RDRSA) strategy when existing connection requests terminated and network resources released is presented. In RDRSA with spectrum conversion (SC), the existing connections are re-established to new route or reassigned to new frequency slots. Defragmentation has three advantages over the conventional RSA: (1) at the time of connection setup, shorter routes may be unavailable, but after the termination of the existing requests; possibility of re-assignment of shorter route becomes high, (2) fragmentation of network also reduces which results load balancing over the entire network, (3) network resource utilization increases due to more connection acceptance. The performance of RDRSA-SC is compared with the conventional RSA with spectrum conversion (SC), and non spectrum conversion (NSC). The simulation results on NSFNET and ARPANET network topologies show that the proposed RDRSA-SC has lower fragmentation and bandwidth blocking probability, and more utilization of network capacity than the existing RSA-SC and RSA-NSC.

Effect of stochastic brittle fragmentations on cyclic loading/unloading hysteresis behavior of fiber-reinforced ceramic-matrix composites

Under monotonic tensile and cyclic tensile loading, the occurrence of stochastic brittle fragmentations will affect monotonic and cyclic loading/unloading mechanical behavior of fiber-reinforced ceramic-matrix composites (CMCs). In this work, synergistic effects of stochastic brittle matrix and fiber fragmentations on monotonic and cyclic loading/unloading hysteresis behavior of fiber-reinforced CMCs were investigated. Different matrix fragmentation lengths and distributions of stresses between intact and broken fibers were determined using stochastic fragmentation models, taking into account cyclic loading/unloading hysteresis constitutive relationships. Experimental monotonic tensile and hysteresis curves, matrix fragmentation density, and fiber fragmentation probability for two different SiC/SiC minicomposites were forecasted. Theoretical tensile curves and loading/unloading hysteresis loops for different peak stresses agreed well with the actual data collected. Interface slip is constrained by the debonding of the interface for long matrix brittle fragmentation (LMBF) length and the fragmentation length of the matrix for short matrix brittle fragmentation (SMBF) length. The impacts of fiber volume fraction and fiber's strength on monotonic and cyclic tensile loading/unloading hysteresis loops were analyzed. Fiber volume fraction increase resulted in increased proportional limit stress and tensile fractured strength and decreased tensile failure strain; in addition, the peak strain of hysteresis loops as well as valley strain and area decreased, with increased hysteresis loops modulus for different matrix fragmentations.

Modeling fragmentation probability of land-use and land-cover using the bagging, random forest and random subspace in the Teesta River Basin, Bangladesh

Land-use and land-cover (LULC) changes have become a crucial issue that urgently needs to be addressed due to global environmental change. Many studies have employed remote sensing data for assessing LULC changes, however, the investigation of fragmentation probability modeling is still scarce in the existing literature. Thus, the coupling of bagging, random forest (RF), random subspace (RSS), and their ensemble model with multi-temporal datasets within the GIS environment makes it possible to model the fragmentation probability of LULC in the Teesta River Basin (TRB), Bangladesh. The number of patch (NP), edge density (ED), largest patch index (LPI), contagion index (%) (CONTAG), aggregation index (AI), perimeter area ratio (P/A ratio), the class area (CA), percentage of landscape (PLAND), patch density (PD), total edge (TE), largest shape index (LSI) and total core area (TCA) were the landscape and class matrices, which were derived from the LULC maps using FRAGSTATS software. The machine learning-based sensitivity models, such as decision tree and support vector machine-based feature selection techniques were implemented to explore the influence of the parameters for fragmentation probability modeling. The results showed that water bodies and barren land were substantially decreased by (6.21%), and (14.59%) respectively while the built-up areas increased by 1.45% from 2010 to 2019. Results revealed that the dominance of the agricultural area has been increased as human interference has been elevated in the TRB. However, twelve class-level and landscape matrices were used to delineate the fragmentation probability zone with the aid of bagging, RF, and RSS algorithms. LULC images and fragmentation probability models were validated using the kappa coefficient and the area under curve (AUC) of the receiver operating characteristics (ROC). The validation outcomes depicted that the three models such as bagging (AUC = 0.864), RF (AUC = 0.819), RSS (AUC = 0.859), and ensemble model (AUC = 0.912) have a good capability to appraise the fragmentation probability, and ensemble model has the highest precision level among three models. Nearly 49% (1789 km2) of the LULC was under a high to very high fragmentation potential zone that requires to be protected with direct measures. The results of sensitivity analysis showed that the number of patches significantly influenced the fragmentation probability model, while the largest patch index was the least sensitive parameter for modeling.

Steam cavity and explosion intensity of molten copper column interaction with water

The steam explosion is one of the most serious accidents in the metallurgical industry. In this paper, an experimental study on the interaction of molten copper column with cooling water was carried out using high-speed camera and transient pressure measurement system. The effects of temperature, falling height, diameter and mass of molten copper column on the interaction were investigated. The steam cavity phenomenon was observed in the interaction and the percentage of steam cavity volume affects the probability of fragmentation of molten copper column. The maximum percentage of steam cavity volume increases firstly and then decreases with the increase of temperature and falling height. It increases with the increase of diameter of molten copper column, but the mass has a weak effect. The pressure wave generated by the interaction of molten copper column with cooling water gradually increases with an increase in the temperature of molten copper column. The energy conversion rate in the interaction of molten copper column with cooling water was calculated. The rate of energy conversion from the thermal energy of molten copper column to the energy of pressure wave is low because most of the thermal energy is dissipated into the cooling water by heat transfer.

Machine learning algorithm-based risk assessment of riparian wetlands in Padma River Basin of Northwest Bangladesh.

Wetland risk assessment is a global concern especially in developing countries like Bangladesh. The present study explored the spatiotemporal dynamics of wetlands, prediction of wetland risk assessment. The wetland risk assessment was predicted based on ten selected parameters, such as fragmentation probability, distance to road, and settlement. We used M5P, random forest (RF), reduced error pruning tree (REPTree), and support vector machine (SVM) machine learning techniques for wetland risk assessment. The results showed that wetland areas at present are declining less than one-third of those in 1988 due to the construction of the dam at Farakka, which is situated at the upstream of the Padma River. The distance to the river and built-up area arethe two most contributing drivers influencing the wetland risk assessment based on information gain ratio (InGR). The prediction results of machine learning models showed 64.48% of area by M5P, 61.75% of area by RF, 62.18% of area by REPTree, and 55.74% of area by SVM have been predicted as the high and very high-risk zones. The results of accuracy assessment showed that the RF outperformed than other models (area under curve: 0.83), followed by the SVM, M5P, and REPTree. Degradation of wetlands explored in this study demonstrated the negative effects on biodiversity. Therefore, to conserve and protect the wetlands, continuous monitoring of wetlands using high resolution satellite images, feeding with the ecological flow, confining built up area and agricultural expansion towards wetlands, and new wetland creation isessential for wetland management.

Structural basis of fast- and slow-severing actin–cofilactin boundaries

Members of the ADF/cofilin family of regulatory proteins bind actin filaments cooperatively, locally change actin subunit conformation and orientation, and sever filaments at “boundaries” between bare and cofilin-occupied segments. A cluster of bound cofilin introduces two distinct classes of boundaries due to the intrinsic polarity of actin filaments, one at the “pointed” end side and the other at the “barbed” end-side of the cluster; severing occurs more readily at the pointed end side of the cluster (“fast-severing” boundary) than the barbed end side (“slow-severing” boundary). A recent electron-cryomicroscopy (cryo-EM) model of the slow-severing boundary revealed structural “defects” at the interface that potentially contribute to severing. However, the structure of the fast-severing boundary remains uncertain. Here, we use extensive molecular dynamics simulations to produce atomic resolution models of both severing boundaries. Our equilibrated simulation model of the slow-severing boundary is consistent with the cryo-EM structural model. Simulations indicate that actin subunits at both boundaries adopt structures intermediate between those of bare and cofilin-bound actin subunits. These “intermediate” states have compromised intersubunit contacts, but those at the slow-severing boundary are stabilized by cofilin bridging interactions, accounting for its lower fragmentation probability. Simulations where cofilin proteins are removed from cofilactin filaments favor a mechanism in which a cluster of two contiguously bound cofilins is needed to fully stabilize the cofilactin conformation, promote cooperative binding interactions, and accelerate filament severing. Together, these studies provide a molecular-scale foundation for developing coarse-grained and theoretical descriptions of cofilin-mediated actin filament severing.

Effect of impeller geometry on bubble breakage and the contributions of different breakage mechanisms in a stirred tank

The effect of impeller geometry on bubble breakage in a stirred tank was investigated for a range of impeller Reynolds number (Re) using a high speed imaging method. The bubble dynamic behavior and breakage mechanism were investigated for four different impeller geometries namely, two-flat blades impeller, four-flat blades impeller, four-twisted blades impeller, and two-pinned blades impeller. The performance of each geometry was investigated by determining the breakage probability and number of fragments (daughter bubbles) produced. The contributions of dominant breakage mechanisms for each geometry were specified and discussed by identifying the breakage locations relative to the impeller. Three main breakage mechanisms were observed, namely: bubble collision with the blade, bubble breakage by blade shear, and breakage by turbulent fluctuation away from the blade. The number of fragments by each breakage mechanism was specified for the entire range of Re. The four-flat blades impeller exhibited the highest breakage probability and produced the highest number of fragments. The Pinned blades gave a high performance compared to the smooth blades, especially at higher Re. This is considered to be due to the high turbulence level provided by this type of impeller. The twisted blades impeller showed low bubble breakage probability compared with the other geometries. Breakages by collision with the blades and by shearing effect resulted in a higher number of fragments compared to the breakages caused by turbulent fluctuations. The number of fragments produced by ‘collision with blade’ exhibited a higher dependence on Re than by ‘blade shear’ or by ‘turbulent fluctuations’.

Quantum control of the dissociation of LiH molecules with two intense laser pulses

The dissociation dynamics of LiH molecules induced by two overlapping femtosecond pulses is investigated based on the time-dependent quantum wave packet method. The first pulse induces population transfer from the ground state $X{\phantom{\rule{0.16em}{0ex}}}^{1}{\mathrm{\ensuremath{\Sigma}}}^{+}$ to the excited state $A{\phantom{\rule{0.16em}{0ex}}}^{1}{\mathrm{\ensuremath{\Sigma}}}^{+}$ which is coupled with the repulsive state $B{\phantom{\rule{0.16em}{0ex}}}^{1}\mathrm{\ensuremath{\Pi}}$ and the state $X{\phantom{\rule{0.16em}{0ex}}}^{1}{\mathrm{\ensuremath{\Sigma}}}^{+}$ by the second pulse. The two products $\mathrm{Li}(2p)$ and $\mathrm{Li}(2s)$ can be obtained via the ladder and $\mathrm{\ensuremath{\Lambda}}$ transitions, respectively, and the branching ratio of the products can be controlled by varying the second pulse frequency $\ensuremath{\hbar}{\ensuremath{\omega}}_{2}$. The choice of the intermediate state can affect the dissociation probability and angular distribution of fragments. As the second pulse intensity is increased, more products occur in other directions besides the directions $\ensuremath{\theta}={0}^{\ensuremath{\circ}}$ and ${180}^{\ensuremath{\circ}}$. The delay time of two pulses also has influence on the angular distribution.

Recent results on B → μ+μ− decays with the CMS experiment

Results on [Formula: see text] decays with the CMS experiment are reported, using 61 fb[Formula: see text] of data recorded during LHC Run 1 and 2016. With an improved muon identification algorithm and refined unbinned maximum likelihood fitting methods, the decay [Formula: see text] is observed with a significance of 5.6 standard deviations. Its branching fraction is measured to be [Formula: see text], where the first error is the combined statistical and systematic uncertainty and the second error quantifies the uncertainty of the [Formula: see text] and [Formula: see text] fragmentation probability ratio. The [Formula: see text] effective lifetime is [Formula: see text]. No evidence for the decay [Formula: see text] is found and an upper limit of [Formula: see text] (at 95% confidence level) is determined. All results are consistent with the standard model of particle physics.

Fragmentation function of gluon into spin-singlet P -wave quarkonium

Following the operator definition of the fragmentation function developed by Collins and Soper, we compute the gluon-to-$h_c$ fragmentation function at the lowest order in the velocity expansion in NRQCD factorization approach. Utilizing some modern technique developed in the area of multi-loop calculation, we are able to analytically deduce the infrared-finite color-singlet short-distance coefficient associated with the fragmentation function. The fragmentation probability for gluon into $h_c$ is estimated to be order $10^{-6}$.

Production of Bc Meson at NLO

In this study, the fragmentation functions (FF) for the production of Bc meson (1S and 2S-states) in c → Bc and b → Bc processes at the leading order (LO) and next-to-leading order (NLO) are derived. Moreover, some technical details about the contributions of the first two sets, n = 1 and n = 2 of S-wave states currents in dimensional regularization scheme are discussed. The differences between the fragmentation functions indicated that the NLO corrections enhanced the fragmentation probability (FP). Also, the probability of production of Bc meson in 1S state and in b → Bc process was more than the one in 1S state and c → Bc process.

Fragmentation and agglomeration of biomass in fluidised bed pyrolysis and combustion

The results of experiments on primary fragmentation of wood biomass particles during fast pyrolysis in an inert medium at different temperatures are presented. Growth of temperature and initial size in the range t = 800 – 950°C increases the probability and intensity of fragmentation in the process of rapid pyrolysis of wood particles. Oblong particles are more prone to fragmentation than quasi-circular (cubic) particles with the same equivalent diameter. The critical diameter of fragmentation for spruce wood particles at a process temperature of 950 °C is dv0 =18-19 mm at the ratio of longitudinal and transverse size h/a =1 and is in the range of 7-9 mm at h/a =8. Study of microstructure and chemical composition of coke particles (fragmentes) by microscope with SEM analysis showed existence of thin outer layer (0-15 μm) on the particle faces, containing increased quantity of mineral components. Microspheres with a size of 13-23 μm and increased content of sulfur were detected on the particle faces, resulting at 950°C. Coinciding of maximum and minimum of chlorine, sodium and potassium content in the outer layer denotes on existence of sodium and potassium chlorides on the surface of coke particles. Results of experimental studies of physical and chemical processes occurring between the fuel ash and the bed materials under prolonged temperature exposure were obtained. The aim of these studies was to determine the time and proportion of agglomerated (sintered) particles of several types of biomass depending on the bed temperature. The experiments were carried out in a furnace on biomass ash, sand and mixture of sand and ash. First experiments showed a clear dependence of the temperature of agglomeration beginning on the potassium concentration in the bed and gave the boundary values of the concentrations and temperatures in the bed.