Breakage Frequencies Research Articles

Experimental study on the differences between bubble and drop breakages in agitated turbulent flows

AbstractThe available experimental data focusing on the differences between bubble and drop breakages are still scarce in the literature. This work conducts the experiments of single bubble and single drop breakages in agitated turbulent flows. The effects of fluid particle size and agitation speed on daughter fragment number, breakage time, breakage probability, breakage frequency, and daughter size distribution (DSD) are analyzed. The breakage frequencies of bubble and drop show the monotonic and non‐monotonic variation trends with increasing fluid particle size, respectively. The variations of bubble and drop DSDs exhibit opposite trends, the probability of equal‐sized breakage of bubble increases while that of drop decreases when agitation speed or fluid particle size increases. These different trends cannot be predicted by most of the existing models simultaneously. The processes of elongation and internal flow redistribution during deformation may be the important factors causing these differences.

Population Balance Models for Particulate Flows in Porous Media: Breakage and Shear-Induced Events

Transport and particulate processes are ubiquitous in environmental, industrial and biological applications, often involving complex geometries and porous media. In this work we present a general population balance model for particle transport at the pore-scale, including aggregation, breakage and surface deposition. The various terms in the equations are analysed with a dimensional analysis, including a novel collision-induced breakage mechanism, and split into one- and two-particles processes. While the first are linear processes, they might both depend on local flow properties (e.g. shear). This means that the upscaling (via volume averaging and homogenisation) to a macroscopic (Darcy-scale) description requires closures assumptions. We discuss this problem and derive an effective macroscopic term for the shear-induced events, such as breakage caused by shear forces on the transported particles. We focus on breakage events as prototype for linear shear-induced events and derive upscaled breakage frequencies in periodic geometries, starting from nonlinear power-law dependence on the local fluid shear rate. Results are presented for a two-dimensional channel flow and a three dimensional regular arrangement of spheres, for arbitrarily fast (mixing-limited) events. Implications for linearised shear-induced collisions are also discussed. This work lays the foundations of a new general framework for multiscale modelling of particulate flows.

Does a Defensive Pseudoautotomy Mechanism Exist in the Subfamily Xenodontinae? A Study of the Genus Echinanthera

Pseudoautotomy is presumably a derived character within Lepidosauria and occurs in taxa that have lost the ability to perform autotomy. In general, species capable of employing pseudoautotomy as a defensive strategy against predators present a high frequency of damaged tails in series deposited in herpetological collections. We assessed data from three largely sympatric Echinanthera species in the Brazilian Atlantic Rainforest (E. cephalostriata, E. cyanopleura, and E. undulata) to test previous assumptions that species of Echinanthera use their tails defensively. This hypothesis derives from anecdotal observations during fieldwork and is reinforced by the number of specimens presenting tail breakage in scientific collections. In general, the frequency of damaged tails in these species resembles that of others in which pseudoautotomy has been demonstrated. Statistical analyses revealed no differences in tail breakage frequencies between sexes for the analyzed species or between the two geographical groups defined for E. cyanopleura. In contrast, we detected a significant difference between snout–vent length and sex regarding pseudoautotomy probability for E. cyanopleura, with a positive relationship between tail breakage frequency and snout–vent length.

Human behavior or taphonomy? On the breakage of Eastern North American Paleoindian endscrapers

Endscrapers, the most abundant tool class at Eastern North American Paleoindian sites, are flaked stone specimens predominately used for scraping hides. They are found broken in high frequencies at these sites, a pattern that has been attributed to use. However, previous experimental and ethnographic research on endscrapers suggests that they are difficult to break. We present a series of replication experiments assessing the amount of force required for endscraper breakage, as well as the amount of force generated during human use. We also analyze which morphometric variable best predicts the breakage force. Our results demonstrate that the force humans can generate is far below the breakage force, which is best predicted by endscraper thickness. Finally, we examine an actual Paleoindian endscraper assemblage, concluding that human use was not the cause for breakage. Taphonomic factors such as plowing, or trampling, are a much better potential explanation for the high breakage frequencies present at Paleoindian sites.

Математическое моделирование процессов коалесценции и дробления капель и пузырей в изотропном турбулентном потоке (обзор)

Предложенный обзор посвящен теоретическому анализу, расчету и моделированию процессов слияния и дробления капель и пузырей в изотропном турбулентном потоке. Проанализирован ряд исследований, посвященных этим проблемам. Рассмотрены вопросы определения минимальных и максимальных размеров капель и пузырей, а также частот дробления и слияния, которые связаны с решением диффузионного уравнения массопереноса. Слияние капель рассматривается как результат утончения межфазной пленки, образованной между двумя каплями в результате их столкновения. Предложено математическое описание утончения межфазной пленки с учетом эффекта Марангони. Анализ множества исследований, в том числе и собственных, показал, что в зависимости от масштаба турбулентных пульсаций экстремальный размер, а также частоты коалесценции и дробления капель и пузырей зависят от удельной энергии диссипации в турбулентном потоке, от их размеров и физических свойств частиц и среды. Важными параметрами, обеспечивающими агрегативную устойчивость дисперсной среды типа «жидкость - жидкость» или «жидкость - газ» к дроблению, деформации и слиянию, являются коэффициент поверхностного натяжения и диссипация энергии, физические свойства среды и частиц, а в изотропном турбулентном потоке - отношение коэффициента поверхностного натяжения к удельной энергии диссипации. Рассмотрены также вопросы, связанные с эволюцией функции распределения частиц по времени и размерам в условиях изотропной турбулентности с использованием решений стохастического уравнения Фоккера-Планка для непрерывного изменения размеров капель и пузырей и интегро-дифференциального кинетического уравнения коалесценции и дробления для скачкообразного изменения размеров частиц. Предложено множество аналитических решений этих уравнений для частных случаев. Более глубокий анализ на основе математических закономерностей явлений переноса позволяет стандартным образом рассчитывать такие системы в некотором приближении как непрерывные с бесконечно малым скачком. Показано, что детерминированное описание этих явлений без учета их стохастической природы является неполным и может приводить к существенным отклонениям от истинной природы указанных выше процессов. Полученные результаты сравнены с существующими экспериментальными данными по коалесценции и дроблению капель и пузырей, что показало удовлетворительное соответствие расчетным значениям.

Cancer chromosome breakpoints cluster in gene-rich genomic regions.

Cancer cells are characterized by chromosome abnormalities, of which some, in particular balanced rearrangements, are associated with distinct tumor entities and/or with specific gene rearrangements that represent important steps in the carcinogenic process. However, the vast majority of cytogenetically detectable structural aberrations in cancer cells have not been characterized at the nucleotide level; hence, their importance and functional consequences are unknown. By ascertaining the chromosomal breakpoints in 22 344 different clonal structural chromosome abnormalities identified in the karyotypes of 49 626 cases of neoplastic disorders we here show that the distribution of breakpoints is strongly associated (P < 0.0001) with gene content within the affected chromosomal bands. This association also remains highly significant in separate analyses of recurrent and nonrecurrent chromosome abnormalities as well as of specific subtypes of cancer (P < 0.0001 for all comparisons). In contrast, the impact of band length was negligible. The breakpoint distribution is thus not stochastic—gene‐rich regions are preferentially affected. Several genomic features relating to transcription, replication, and chromatin organization have been found to enhance chromosome breakage frequencies; this indicates that gene‐rich regions may be more break‐prone. The salient finding in the present study is that a substantial fraction of all structural chromosome abnormalities, not only those specifically associated with certain tumor types, may affect genes that are pathogenetically important. If this interpretation is correct, then the prevailing view that the great majority of cancer chromosome aberrations is cytogenetic noise can be seriously questioned.

Classification of puffed snacks freshness based on crispiness-related mechanical and acoustical properties

The use of instrumental methods to support sensory panels in the routine quality control of crispiness remains challenging. Texture analysis is often insufficient to accurately classify this complex sensory attribute. Herein, 70 different food properties were combined via machine learning algorithms to mimic multisensory integration. Force and sound were measured during crushing of puffed snacks equilibrated at different humidity levels. Sensory panels then ranked crispiness-related freshness and preference based on the recorded sounds. Selected feature combinations were used to train machine learning models to recognize the freshness levels at different humidity levels. The classification accuracy was improved compared with traditional texture analysis techniques; an accuracy of up to 92% could be achieved with quadratic support vector machine or artificial neural network algorithms. Moreover, third-octave frequency bands, characterizing breakage frequencies and sound pitches, were determined to be main descriptors to be taken into account during the research and development of puffed snacks.

Analysis of various inverters feeding induction motors with incipient rotor fault using high-resolution spectral analysis

Recently, there has been an increased interest in fault detection on electrical machines in steady-state regimes. Several frequency estimation techniques have been developed to assist the early detection of faults in induction motors, especially in line-fed motors. However, in modern industry, the use of inverters is increasingly present. This paper presents an analysis for comprehending the challenge in detecting incipient rotor faults using the stator current signal under different inverter supplies. The approach is based on the high-resolution technique known as multiple signal classification (MUSIC). In this study, incipient rotor faults in a squirrel-cage rotor, prior to the complete breaking of a rotor bar, are better identified in some inverters than others. The proposed approach finds the adequate MUSIC order that facilitates identification of bar breakage frequencies for early fault detection in each case studied from a wide set of trials. The study has been developed to detect incipient rotor bar breakages in an inverter-fed three-phase induction motor under varying load situations.

Corrigendum: A genome-wide analysis of common fragile sites: What features determine chromosomal instability in the human genome?

Chromosomal common fragile sites (CFSs) are unstable genomic regions that break under replication stress and are involved in structural variation. They frequently are sites of chromosomal rearrangements in cancer and of viral integration. However, CFSs are undercharacterized at the molecular level and thus difficult to predict computationally. Newly available genome-wide profiling studies provide us with an unprecedented opportunity to associate CFSs with features of their local genomic contexts. Here, we contrasted the genomic landscape of cytogenetically defined aphidicolin-induced CFSs (aCFSs) to that of nonfragile sites, using multiple logistic regression. We also analyzed aCFS breakage frequencies as a function of their genomic landscape, using standard multiple regression. We show that local genomic features are effective predictors both of regions harboring aCFSs (explaining ∼77% of the deviance in logistic regression models) and of aCFS breakage frequencies (explaining ∼45% of the variance in standard regression models). In our optimal models (having highest explanatory power), aCFSs are predominantly located in G-negative chromosomal bands and away from centromeres, are enriched in Alu repeats, and have high DNA flexibility. In alternative models, CpG island density, transcription start site density, H3K4me1 coverage, and mononucleotide microsatellite coverage are significant predictors. Also, aCFSs have high fragility when colocated with evolutionarily conserved chromosomal breakpoints. Our models are predictive of the fragility of aCFSs mapped at a higher resolution. Importantly, the genomic features we identified here as significant predictors of fragility allow us to draw valuable inferences on the molecular mechanisms underlying aCFSs.

An innovative numerical approach for simulation of emulsion formation in a Microfluidizer

Abstract Microfluidizer is frequently employed for the homogenization of emulsions in food industries. This paper provides an innovative numerical approach for predicting the Microfluidizer performance in the emulsification process. The model has been based on simultaneous coupling of CFD–PBE in each computational cell, instead of the sequential approach proposed previously by other authors. The class method has been selected for discretization of PBE with appropriate breakage and coalescence frequencies. By changing the significant variables, including pressure, pass number and oil content, it has been observed that the numerical results are in general agreement with the experimental data. The results reveal the potential of the proposed approach in prediction of emulsion formation in the Microfluidizer. The evolution of emulsion size distribution in the whole domain implies that viscosity and inertia in turbulent flow contribute to oil droplet breakage, while the impinging of jets is an auxiliary mechanism.

A note on handaxe knapping products and their breakage taphonomy: an experimental view

The notion that broken artifacts provide a good indication of the taphonomic history of lithic assemblages is commonly accepted in prehistoric archaeology. High frequencies of broken artifacts are frequently viewed as an indication of the possible role of post-depositional processes such as high-energy fluvial transportation, trampling or plowing. Yet another alternative is that the breakage resulted from the knapping process itself. In this study, the knapping byproducts of biface shaping and thinning (the final stages of handaxe production) originating in several experiments were systematically studied and their breakage frequencies and patterns were determined. The breakage patterns observed for the experimental assemblages were then used in a model designed to simulate the effect of breakage resulting from post-depositional processes, providing the breakage patterns expected for such an assemblage. The breakage pattern and frequencies observed in the experimental assemblages and those provided by the model were then compared to an archaeological assemblage representing the production of Acheulian assemblages that include bifaces from the site of Gesher Benot Ya‘aqov (GBY), Israel. The results indicate that high breakage rates are inherent to the final stages of the Acheulian bifacial knapping process. Furthermore, they demonstrate that taphonomic (post-depositional) breakage changes the breakage pattern of the production stages in a systematic trend. Finally, the results show that the lithic assemblage of GBY presents breakage frequencies and patterns that are more similar to those of the experimental assemblages than those generated by the model. In the light of these results, it is suggested that this assemblage was not subjected to any breakage caused by post-depositional processes.

Analytical solutions of the particle breakage equation by the Adomian decomposition and the variational iteration methods

The breakage in batch and continuous systems has attained high interest in chemical engineering and granulation from a process and from a product quality perspective. The wet granule breakage process in a high shear mixer will influence and may control the final granule size distribution. In this work, we developed analytical solutions of the particle breakage using the population balance equation (PBEs) in batch and continuous flow systems. To allow explicit solutions, we approximate particle breakage mechanisms with assumed functional forms for breakage frequencies. This new framework for solving (PBEs) for batch and continuous flow systems proposed in this work uses the Adomian decomposition method (ADM) and the variational iteration method (VIM). These semi-analytical methods overcome the crucial difficulties of numerical discretization and stability that often characterize previous solutions in of the PBEs. The results obtained in all cases show that the predicted particle size distributions converge exactly in a continuous form to that of the analytical solutions using the two methods.

LLECMOD: A Bivariate Population Balance Simulation Tool for Pulsed Liquid-Liquid Extraction Columns

A rigours mathematical model based on the bivariate population balance frame work (the base of LLECMOD “Liquid-Liquid Extraction Column Module”) for the steady state and dynamic simulation of pulsed liquid-liquid extraction columns is developed. The model simulates the coupled hydrodynamic and mass transfer for pulsed (packed and sieve plate) extraction columns. It is implemented using visual digital FORTRAN and then integrated into the LLECMOD program. Experimental validated correlations are used for the estimation of the droplet terminal velocity in extraction columns based on single and swarm droplet experiments in laboratory scale devices. Additionally, recently published correlations for turbulent energy dissipation, droplet breakage and coalescence frequencies are discussed as being used in this version of LLECMOD. In a case study, LLECMOD is used here to simulate the steady state performance of pulsed extraction columns with two chemical test systems recommended by the European Federation of Chemical Engineering (water- acetone-n-butyl acetate and water-acetone-toluene) and an industrial test system. Model predictions are successfully validated against steady state and transient experimental data, where good agreements are achieved. The simulated results (holdup, mean droplet diameter and mass transfer profiles) compared to the experimental data show that LLECMOD is a powerful simulation tool, which can efficiently predict the dynamic and steady state performance of pulsed extraction columns.

A genome-wide analysis of common fragile sites: What features determine chromosomal instability in the human genome?

Chromosomal common fragile sites (CFSs) are unstable genomic regions that break under replication stress and are involved in structural variation. They frequently are sites of chromosomal rearrangements in cancer and of viral integration. However, CFSs are undercharacterized at the molecular level and thus difficult to predict computationally. Newly available genome-wide profiling studies provide us with an unprecedented opportunity to associate CFSs with features of their local genomic contexts. Here, we contrasted the genomic landscape of cytogenetically defined aphidicolin-induced CFSs (aCFSs) to that of nonfragile sites, using multiple logistic regression. We also analyzed aCFS breakage frequencies as a function of their genomic landscape, using standard multiple regression. We show that local genomic features are effective predictors both of regions harboring aCFSs (explaining ∼77% of the deviance in logistic regression models) and of aCFS breakage frequencies (explaining ∼45% of the variance in standard regression models). In our optimal models (having highest explanatory power), aCFSs are predominantly located in G-negative chromosomal bands and away from centromeres, are enriched in Alu repeats, and have high DNA flexibility. In alternative models, CpG island density, transcription start site density, H3K4me1 coverage, and mononucleotide microsatellite coverage are significant predictors. Also, aCFSs have high fragility when colocated with evolutionarily conserved chromosomal breakpoints. Our models are predictive of the fragility of aCFSs mapped at a higher resolution. Importantly, the genomic features we identified here as significant predictors of fragility allow us to draw valuable inferences on the molecular mechanisms underlying aCFSs.

Embryonic Lethality after Combined Inactivation of Fancd2 and Mlh1 in Mice

DNA repair defects are frequently encountered in human cancers. These defects are utilized by traditional therapeutics but also offer novel cancer treatment strategies based on synthetic lethality. To determine the consequences of combined Fanconi anemia (FA) and mismatch repair pathway inactivation, defects in Fancd2 and Mlh1 were combined in one mouse model. Fancd2/Mlh1 double-mutant embryos displayed growth retardation resulting in embryonic lethality and significant underrepresentation among progeny. Additional inactivation of Trp53 failed to improve the survival of Fancd2/Mlh1-deficient embryos. Mouse fibroblasts were obtained and challenged with cross-linking agents. Fancd2-deficient cells displayed the FA-characteristic growth inhibition after mitomycin C (MMC) exposure. In primary fibroblasts, the absence of Mlh1 did not greatly affect the MMC sensitivity of Fancd2-deficient and Fancd2-proficient cells. However, in Trp53 mutant immortalized fibroblasts, Mlh1 deficiency reduced the growth-inhibiting effect of MMC in Fancd2 mutant and complemented cells. Similar data were obtained using psoralen/UVA, signifying that MLH1 influences the cellular sensitivity to DNA interstrand cross-links. Next, the effect of MLH1 deficiency on the formation of chromosomal aberrations in response to cross-linking agents was determined. Surprisingly, Mlh1 mutant fibroblasts displayed a modest but noticeable decrease in induced chromosomal breakage and interchange frequencies, suggesting that MLH1 promotes interstrand cross-link repair catastrophe. In conclusion, the combined inactivation of Fancd2 and Mlh1 did not result in synthetic lethality at the cellular level. Although the absence of Fancd2 sensitized Mlh1/Trp53 mutant fibroblasts to MMC, the differential survival of primary and immortalized fibroblasts advocates against systemic inactivation of FANCD2 to enhance treatment of MLH1-deficient tumors.

In Vitro Effect of Fludarabine, Cyclophosphamide, and Cytosine Arabinoside on Chromosome Breakage in Fanconi Anemia Patients: Relevance to Stem Cell Transplantation

Designing stem cell transplantation (SCT) conditioning regimens for Fanconi anemia (FA) has proved difficult because of hypersensitivity to the DNA cross-linking agents. We performed chromosome fragility tests with 56 FA patients and with 50 non-FA patients with severe aplastic anemia or myelodysplastic syndrome. We evaluated peripheral blood lymphocyte specimens cultured for 72 hours and treated with mitomycin C, diepoxybutane (DEB), cyclophosphamide (CY) metabolites, cytosine arabinoside (Ara-C), and fludarabine (Flu) metabolite (9-beta-D-arabinofuranosyl-2-fluoroadenine [2-F-Ara-A]). The DEB and CY metabolite tests were highly sensitive and specific for FA (P<10(-4)) for both tests), and the number of aberrations per cell for DEB correlated with that for the CY metabolite test (P < 10(-4)) but did not correlate with the number of aberrations per cell for the Ara-C and 2-F-Ara-A tests. The difference in breakage frequencies between FA and non-FA patients for cultures treated with 2-F-Ara-A was not statistically significant. Most of the breakages observed in cells treated with 2-F-Ara-A-and Ara-C were chromatid breaks. It may be possible to determine the appropriate CY dose in the preconditioning regimen for SCT in FA patients on the basis of the in vitro effects on fragility, and Flu or Ara-C may be a safer drug than high-dose CY for conditioning in FA patients.

LLECMOD: A Windows-based program for hydrodynamics simulation of liquid–liquid extraction columns

The simulation of liquid–liquid extraction columns based on a droplet population balance approach provides a useful means for getting more insight into the transient and the steady state behavior of such an extremely important unit operation. This numerical simulation is carried out based on a recently developed algorithm for solving the population balance equation. The algorithm is implemented via a computer program called liquid–liquid extraction column module (LLECMOD). The LLECMOD is designed in a flexible way that allows the user to define the breakage and coalescence frequencies, droplet terminal velocity, and the other internal geometrical details of the column. The user input dialog makes the LLECMOD a user-friendly program that enables the user to select the simulation parameters and functions in an easy way. The program is reinforced by a parameter estimation package for the droplet coalescence models. In this work, a sample of small laboratory and pilot plant simulations as compared to the experimental data is presented as carried out by the LLECMOD.

Population balance modeling of bubble size distributions in a direct-contact evaporator using a sparger model

The study of bubble size distributions in direct-contact evaporators was addressed both theoretically and experimentally. Recently developed models for calculating bubble coalescence and breakage frequencies in isothermal bubble columns were adapted to the population balance equation using the bubble mass as the internal coordinate which was discretized using an expansion of the number density function by impulse functions. A sparger model was developed based on experimental data for a non-coalescing system and using bubble formation models for isothermal and non-isothermal conditions. Bubble size distributions in a direct-contact evaporator operating in the quasi-steady-state regime for four different gas superficial velocities, including the homogeneous and heterogeneous regimes, together with the sparger model, were used for estimating the three empirical parameters from the population balance model, which were observed to be functions of the gas superficial velocity. In all cases considered, the population balance model fitted the experimental data rather well and the regressed parameters exhibit the physically expected behavior with changes in the gas superficial velocity.

CFD Simulation of Nonideal Dispersed Phase Flow in Stirred Extraction Columns

This paper will focus on hydrodynamic relations arising from single-droplet movement in a rotating disc extraction column (RDC) geometry. These relations can be regarded as the basis for a general estimation strategy for the determination of dispersed-phase flow parameters in connection with droplet population balance modeling. The droplet population balance based modeling of countercurrent liquid-liquid extraction column offers a considerable advance in describing the real droplet swarm behavior. The main problem encountered is the determination of the characteristic droplet model parameters, such as droplet rising velocity, axial backmixing, droplet breakage and droplet coalescence frequencies. The scope of this paper is to estimate fluid and particle residence times and thus the backmixing characteristics.

Scale-up effects on the drop size distribution of liquid–liquid dispersions in agitated vessels

A multifractal formalism describing the fine-scale structure of turbulence, including its intermittency, is applied to express the drop breakage and coalescence frequencies for drops whose diameter falls within the inertial subrange of turbulence. The model predicts the transient drop size distributions of dispersions in stirred tanks and is used to test four methods of scaling-up agitated vessels. Fast and slow coalescing dispersions are considered.