bluuebunny/crossref_metadata_2025 huggingface dataset:
Prenatal diagnosis of chronic intestinal pseudo‐obstruction and paternal somatic mosaicism for the ACTG2 pathogenic variant
Authors: Milunsky Aubrey , Lazier Joanna , Baldwin Clinton , Young Carmen , Primack Daniel , Milunsky Jeff M.
Published: October 2017

What's already known about this topic?

Pathogenic variants in the ACTG2 gene cause highly variable autosomal dominant phenotypes from intestinal pseudo‐obstruction to megacystis to constipation. Pathogenic variants in rarer recessive genes (MYH11, MYLK, RAD21, and LMOD1) cause similar phenotypes.

What does this study add?

Autosomal dominant pathogenic variants in the ACTG2 gene may originate from an asymptomatic parent who has somatic mosaicism for this gene mutation, resulting in megacystis‐microcolon‐hypoperistalsis syndrome. Prenatal diagnosis can be offered when fetal bladder prominence is observed.
New generalized Newtonian fluid models for quantitative description of complex viscous behavior in shear flows
Authors: Steller Ryszard , Iwko Jacek
Published: October 2017

Two semiempirical models of generalized Newtonian fluid are discussed. Special attention was focused on the stress dependent model based on the free volume theory. However, the strain‐rate dependent model in form of a modified viscosity function resulting from Oldroyd equation is also presented. Both models (along with specific cases) reflecting pseudoplastic or dilatant behavior of liquids in shear flows are generalized to multimode models (defined as products of two or more basic models), which are able to describe quantitatively the behavior of more complex systems, for example, systems with pseudoplastic and dilatant properties in different shear stress (shear rate) ranges. A number of practical examples for viscosity curves of non‐Newtonian fluids described by these models are given. The questions of inverse models and model efficiency are also discussed. POLYM. ENG. SCI., 58:1446–1455, 2018. © 2017 Society of Plastics Engineers
Assessing Personality–Situation Interplay in Personnel Selection: Toward More Integration into Personality Research
Authors: Lievens Filip
Published: October 2017

Over the years, the personnel selection field has developed methods to assess trait expression in particular situations, but these approaches have evolved mostly outside the field of personality psychology. In this article, I review available personnel selection evidence regarding two such approaches: (i) situational judgement tests that present short scenarios and ask job candidates how they would handle the situations and (ii) assessment centre exercises requiring candidates to display behaviour in specified interactive situations. I describe these approaches and discuss their relations with personality research. I posit that adapting these approaches to personality research creates methodological diversity to address key research themes related to within–person variability, trait–behaviour links, personality disorders, and personality expression and perception. Copyright © 2017 European Association of Personality Psychology
Integrating Personality Structure, Personality Process, and Personality Development
Authors: Baumert Anna , Schmitt Manfred , Perugini Marco , Johnson Wendy , Blum Gabriela , Borkenau Peter , Costantini Giulio , Denissen Jaap J. A. , Fleeson William , Grafton Ben , Jayawickreme Eranda , Kurzius Elena , MacLeod Colin , Miller Lynn C. , Read Stephen J. , Roberts Brent , Robinson Michael D. , Wood Dustin , Wrzus Cornelia
Published: October 2017

In this target article, we argue that personality processes, personality structure, and personality development have to be understood and investigated in integrated ways in order to provide comprehensive responses to the key questions of personality psychology. The psychological processes and mechanisms that explain concrete behaviour in concrete situations should provide explanation for patterns of variation across situations and individuals, for development over time as well as for structures observed in intra–individual and inter–individual differences. Personality structures, defined as patterns of covariation in behaviour, including thoughts and feelings, are results of those processes in transaction with situational affordances and regularities. It cannot be presupposed that processes are organized in ways that directly correspond to the observed structure. Rather, it is an empirical question whether shared sets of processes are uniquely involved in shaping correlated behaviours, but not uncorrelated behaviours (what we term ‘correspondence’ throughout this paper), or whether more complex interactions of processes give rise to population–level patterns of covariation (termed ‘emergence’). The paper is organized in three parts, with part I providing the main arguments, part II reviewing some of the past approaches at (partial) integration, and part III outlining conclusions of how future personality psychology should progress towards complete integration. Working definitions for the central terms are provided in the appendix. Copyright © 2017 European Association of Personality Psychology
Experimental research in school psychology internationally: An assessment of journal publications and implications for internationalization
Authors: Begeny John C. , Levy Rebecca A. , Hida Rahma , Norwalk Kate
Published: October 2017

Past studies have examined the contents of journal articles in school psychology, and more recently there has been increased interest in examining the frequency and characteristics of experimental studies appearing in school psychology journals. However, no prior studies have examined the international representation of experimental and intervention studies. This study evaluated every article published from 2002 to 2016 across eight school psychology journals that publish international scholarship. Several research questions were addressed (e.g., what is the frequency of experimental research internationally, what are the characteristics of those studies, and is the scholarship consistent with the global geography of school psychology?). Overall, findings revealed that although the field of school psychology is arguably international, the experimental research reflected in the eight journals selected for review does not adequately represent the global geography of the field, thereby also suggesting that the degree of internationalization in school psychology is relatively poor. The importance of these and related findings is discussed, and recommendations are provided that may help to improve the geographical representation of experimental research in school psychology as well as its overall internationalization.
Assessment of contact predictions in CASP12: Co‐evolution and deep learning coming of age
Authors: Schaarschmidt Joerg , Monastyrskyy Bohdan , Kryshtafovych Andriy , Bonvin Alexandre M.J.J.
Published: October 2017

Following up on the encouraging results of residue‐residue contact prediction in the CASP11 experiment, we present the analysis of predictions submitted for CASP12. The submissions include predictions of 34 groups for 38 domains classified as free modeling targets which are not accessible to homology‐based modeling due to a lack of structural templates. CASP11 saw a rise of coevolution‐based methods outperforming other approaches. The improvement of these methods coupled to machine learning and sequence database growth are most likely the main driver for a significant improvement in average precision from 27% in CASP11 to 47% in CASP12. In more than half of the targets, especially those with many homologous sequences accessible, precisions above 90% were achieved with the best predictors reaching a precision of 100% in some cases. We furthermore tested the impact of using these contacts as restraints in ab initio modeling of 14 single‐domain free modeling targets using Rosetta. Adding contacts to the Rosetta calculations resulted in improvements of up to 26% in GDT_TS within the top five structures.
Assessment of protein assembly prediction in CASP12
Authors: Lafita Aleix , Bliven Spencer , Kryshtafovych Andriy , Bertoni Martino , Monastyrskyy Bohdan , Duarte Jose M. , Schwede Torsten , Capitani Guido
Published: October 2017

We present the results of the first independent assessment of protein assemblies in CASP. A total of 1624 oligomeric models were submitted by 108 predictor groups for the 30 oligomeric targets in the CASP12 edition. We evaluated the accuracy of oligomeric predictions by comparison to their reference structures at the interface patch and residue contact levels. We find that interface patches are more reliably predicted than the specific residue contacts. Whereas none of the 15 hard oligomeric targets have successful predictions for the residue contacts at the interface, six have models with resemblance in the interface patch. Successful predictions of interface patch and contacts exist for all targets suitable for homology modeling, with at least one group improving over the best available template for each target. However, the participation in protein assembly prediction is low and uneven. Three human groups are closely ranked at the top by overall performance, but a server outperforms all other predictors for targets suitable for homology modeling. The state of the art of protein assembly prediction methods is in development and has apparent room for improvement, especially for assemblies without templates.
Assessment of the model refinement category in CASP12
Authors: Hovan Ladislav , Oleinikovas Vladimiras , Yalinca Havva , Kryshtafovych Andriy , Saladino Giorgio , Gervasio Francesco Luigi
Published: October 2017

We here report on the assessment of the model refinement predictions submitted to the 12th Experiment on the Critical Assessment of Protein Structure Prediction (CASP12). This is the fifth refinement experiment since CASP8 (2008) and, as with the previous experiments, the predictors were invited to refine selected server models received in the regular (nonrefinement) stage of the CASP experiment. We assessed the submitted models using a combination of standard CASP measures. The coefficients for the linear combination of Z‐scores (the CASP12 score) have been obtained by a machine learning algorithm trained on the results of visual inspection. We identified eight groups that improve both the backbone conformation and the side chain positioning for the majority of targets. Albeit the top methods adopted distinctively different approaches, their overall performance was almost indistinguishable, with each of them excelling in different scores or target subsets. What is more, there were a few novel approaches that, while doing worse than average in most cases, provided the best refinements for a few targets, showing significant latitude for further innovation in the field.
Designing Phase I Shewhart X¯charts: Extended tables and software
Authors: Yao Y. , Hilton C.W. , Chakraborti S.
Published: October 2017

Control charts play an important role in Phase I studies, which are conducted to establish process control and generate reference data for parameter estimation and calculation of prospective (Phase II) control limits. Researchers have tabulated the necessary charting constants for the normal theory–based Phase I Shewhart
chart for the process mean to achieve a desired nominal false alarm probability given the number of Phase I subgroups, m, up to 15. However, in practice, when parameters are estimated, the currently recommended number of Phase I subgroups is much larger than covered by their tables. Recognizing the need and taking advantage of some recently available software and computing resources, an extension to these tables is provided for m = 3(1)10 , 15(5)30 , 50(25)300 and n = 3 , 5 , 7 , 10. In addition to the tables, an R program is provided to calculate the charting constant, on demand, for user‐given values of nominal false alarm probability, m, and n. An appendix shows the details of how the program should be used.
A Framework for Understanding and Achieving Sustainability of Complex Systems
Authors: Mobus George
Published: October 2017

This article introduces a systems framework for understanding the sustainability of complex adaptive and evolvable systems such as the human social system, viewed as a subsystem of the whole Earth system. The argument is advanced that subsystems of semi‐closed supra‐systems must fulfil a ‘purpose’ in the context of the larger supra‐system in order to achieve sustained continuance. The success of the system in interacting with its environment over an extended time frame depends on that system's ability to regulate its activities, both internal and external so as to remain ‘fit’. The roles of adaptivity and evolvability and the mechanisms of a hierarchical cybernetic governance subsystem in maintaining these are discussed as the means for achieving sustainability in all types of complex systems. An operational definition of sustainability is put forth along with a set of necessary conditions that must be obtained in order for complex systems to achieve it. Copyright © 2017 John Wiley & Sons, Ltd.
The First Quinary Rare Earth Thiophosphates: Cs5Ln3X3(P2S6)2(PS4) (Ln = La, Ce, X = Br, Cl) and the Quasi‐Quaternary Cs10Y4Cl10(P2S6)3
Authors: Schoop Leslie Mareike , Eger Roland , Nuss Jürgen , Pielnhofer Florian , Lotsch Bettina Valeska
Published: October 2017

We report the first examples of quinary rare earth thiophosphates with a fully ordered cation and anion distribution, Cs5Ln3X3(P2S6)2(PS4), (Ln = La, Ce and X = Br, Cl) as well as the quasi‐quaternary Cs10Y4Cl10(P2S6)3. These four new compounds crystallize in three different, unknown structure types. The yellowish, transparent, brittle Cs5Ce3Br3(P2S6)2(PS4) crystallizes in the orthorhombic space group Pnma (no. 62) with a = 13.276(3), b = 14.891(3), c = 19.593(4) Å, and V = 3873(1) Å3 in a novel structure type. Colorless crystals of Cs5La3Br3(P2S6)2(PS4) and Cs5La3Cl3(P2S6)2(PS4) are isotypic and were obtained in the monoclinic space group P21/m (no. 11) with a = 9.715(2), b = 14.310(3), c = 13.685(3) Å, β = 100.16(3)° and V = 1873(1) Å3 and a = 9.513(2), b = 14.182(3), c = 13.699(3) Å, β = 99.39(3)° and V = 1823(1) Å3, respectively. Both structures contain isolated hexathiohypodiphosphate(IV) [P2S6]4– and thiophosphate [PS4]3– units that are arranged alternately in layers. Cs10Y4Cl10(P2S6)3 crystallizes in colorless transparent platelets in the orthorhombic space group Pnnm (no. 58) with a = 13.153(3), b = 28.964(6), c = 7.780(2) Å, and V = 2964(1) Å3. The structure is composed of isolated [P4/2S6]4– octahedra containing four half occupied P positions surrounded octahedrally by sulfur. We show with Raman scattering that this disordered thiophosphate anion shows a Raman spectrum that is distinct from spectra published for other literature‐known thiophosphate anions.
Correction to: Surface‐Active Properties of Solvent‐Extracted Panax ginseng Saponin‐Based Surfactants
Authors: Mesgarzadeh Iraj , Akbarzadeh Ali Reza , Rahimi Rahmatollah
Published: October 2017

In the original version of the paper, the corresponding author was listed as Iraj Mesgarzadeh. At the request of the authors, the corresponding author changed to Rahmatollah Rahimi. Dr. Rahimi can be contacted at rahimi_rah@iust.ac.ir.
Immune profiling of human prostate epithelial cells determined by expression of p38/TRAF‐6/ERK MAP kinases pathways
Authors: Bouraoui Yosra , Achour Mongia , Royuela Mar , Oueslati Ridha
Published: October 2017

The aim of the present work was to study the immune profiling of prostate epithelial cells by the expression of ASK‐1/p38 and Raf‐1/ERK MAP Kinases signaling pathways mediated by TRAF‐6. Immunohistochemical and Western blot analyses for TRAF‐6, ASK‐1, MEK‐6, p38, Raf‐1, MEK‐1, ERK‐1, ERK‐2 and PSA were carried out in 5 samples of normal prostate gland, 24 samples of BPH and 19 samples of PC. Immunoreaction to TRAF‐6 was found in the cytoplasm of epithelial cells of BPH and tumor cells of PC samples. For patients with the profile (TRAF‐6+), optical densities revealed a weak immunoexpression of ASK‐1 in PC compared to BPH patients. Whereas, immunoexpression to Raf‐1 was higher in PC than in BPH. According to the expression of ASK‐1 and Raf‐1, two main profiles were identified: (TRAF‐6+, ASK‐1+, Raf‐1+) and (TRAF‐6+, ASK‐1+, RAF‐1−) in both BPH and PC. In addition, ASK‐1/p38 axis expression was increased in BPH. Raf‐1/ERK signaling pathway was increased in PC samples. On the other hand, representing of individual signaling protein expression enclosing each of p38 and ERK MAP Kinases according to TRAF‐6+ showed a qualitative behavior of ASK61/p38 and Raf‐1/ERK signaling pathways and a dynamic expression of PSA associated with immune and inflammatory process. These findings suggest that prostate epithelial cell could able an immune and inflammatory setting.
Greek Historical Influence on Early Roman History
Authors: Trundle Matthew
Published: October 2017

This study employs a comparative approach using Greek models of historical enquiry, especially those of Herodotus, to illustrate how Romans prior to the Punic Wars, and indeed as early as the fifth and fourth centuriesBC, might have developed their own historical consciousness and historical traditions concerning their early past in much the same way as we know the Greeks had done by the fifth centuryBC. What follows is not at all new. Many have identified Roman historical and historiographical roots, connections, and even parallels with Greek history and historians.1What follows reiterates those connections, explicitly by assessing how Herodotus presented his inquiries to his Greek audience, laying the foundations for the discipline ofhistoria, and then by examining specifically the story of the Fabii at the Cremera in Livy, Dionysius and Diodorus. Through this one historical example, I hope to show that the roots of genuine historical thought can be found in the sources of our sources for early Roman traditions. Despite the fact that these traditions appear in works written much later than the events they describe, the nature of the stories preserved in our extant accounts suggests similar historiographical roots and interest as those preserved by Herodotus for the Greeks in the stories he told in hisHistories.
Politics, Power, and the Divine: TheRex Sacrorumand the Transition from Monarchy to Republic at Rome
Authors: Glinister Fay
Published: October 2017

Whether the result of internal revolution or external factors, in the late sixth centuryBCRome underwent regime change. A king, or at least a sole ruler of some sort, was replaced by a governmental system in which power was distributed amongst a wider aristocratic group. Just what that elite group comprised at that point in time remains open to question, and the institutional reality is certainly more complicated than the simple shift from monarchy to consulship portrayed in the later literary sources;1but as part of that change, according to Roman tradition, a priesthood was instituted to perform the deposed king’s sacred duties. This priesthood provides us with an opportunity to reappraise the role of religion in the development of the Roman state, and a useful locus from which to assess changes in religious and political power in the transition from monarchy to Republic at Rome.
The South Dakota Model: Health Care Professions Student Disaster Preparedness and Deployment Training
Authors: Owens Matt P. , Buffington Cheri , Frost Michael P. , Waldner Randall J.
Published: October 2017

Objective

The Association of American Medical Colleges recommended an increase in medical education for public health emergencies, bioterrorism, and weapons of mass destruction in 2003. The University of South Dakota Sanford School of Medicine (USD SSOM) implemented a 1-day training event to provide disaster preparedness training and deployment organization for health professions students called Disaster Training Day (DTD).

Methods

Hospital staff and emergency medical services personnel provided the lecture portion of DTD using Core Disaster Life Support (CDLS; National Disaster Life Support Foundation) as the framework. Pre-test and post-test analyses were presented to the students. Small group activities covered leadership, anaphylaxis, mass fatality, points of dispensing deployment training, psychological first aid, triage, and personal protective equipment. Students were given the option to sign up for statewide deployment through the South Dakota Statewide Emergency Registry of Volunteers (SERV SD). DTD data and student satisfaction surveys from 2009 to 2016 were reviewed.

Results

Since 2004, DTD has provided disaster preparedness training to 2246 students across 13 health professions. Significant improvement was shown on CDLS post-test performance with a t-score of −14.24 and a resulting P value of <0.00001. Students showed high levels of satisfaction on a 5-level Likert scale with overall training, small group sessions, and perceived self-competency relating to disaster response. SERV SD registration increased in 2015, and 77.5% of the participants registered in 2016.

Conclusion

DTD at the USD SSOM provides for an effective 1-day disaster training course for health professions students. Resources from around the state were coordinated to provide training, liability coverage, and deployment organization for hundreds of students representing multiple health professions. (Disaster Med Public Health Preparedness. 2017;11:735–740)
Hegel and Marx on the Necessity of the Reign of Terror
Authors: James David
Published: October 2017

Both Hegel and Marx appear committed to the idea that the Reign of Terror was in some sense necessary. I argue that Hegel explains this necessity in terms of the concept of ‘absolute freedom’, together with the associated self-conception and normative picture of the world. It will be argued that Marx also views the Reign of Terror as necessary because of an abstract conception of political freedom and the citizen which conflicts with a determinate individuality that is characterized by particular interests and identities. In connection with Marx’s critique of Hegel’s theory of the modern state I draw attention to a puzzle, the discussion of which will lead to a brief account of how Marx’s attempt to overcome the opposition between the state and civil society differs from Hegel’s.
Evaluating the Relationship Between Hospital Antibiotic Use and Antibiotic Resistance in Common Nosocomial Pathogens
Authors: Wang Annie , Daneman Nick , Tan Charlie , Brownstein John S. , MacFadden Derek R.
Published: October 2017

OBJECTIVE

The relationship between hospital antibiotic use and antibiotic resistance is poorly understood. We evaluated the association between antibiotic utilization and resistance in academic and community hospitals in Ontario, Canada.

METHODS

We conducted a multicenter observational ecological study of 37 hospitals in 2014. Hospital antibiotic purchasing data were used as an indicator of antibiotic use, whereas antibiotic resistance data were extracted from hospital indexes of resistance. Multivariate regression was performed, with antibiotic susceptibility as the primary outcome, antibiotic consumption as the main predictor, and additional covariates of interest (ie, hospital type, laboratory standards, and patient days).

RESULTS

With resistance data representing more than 90,000 isolates, we found the increased antibiotic consumption in defined daily doses per 1,000 patient days (DDDs/1,000 PD) was associated with decreased antibiotic susceptibility forPseudomonas aeruginosa(−0.162% per DDD/1,000 PD;P=.119). However, increased antibiotic consumption predicted increased antibiotic susceptibility significantly forEscherichia coli(0.173% per DDD/1,000 PD;P=.005),Klebsiellaspp (0.124% per DDD/1,000 PD;P=.004),Enterobacterspp (0.194% per DDD/1,000 PD;P=.003), andEnterococcusspp (0.309% per DDD/1,000 PD;P=.001), and nonsignificantly forStaphylococcus aureus(0.012% per DDD/1,000 PD;P=.878). Hospital type (P=.797) and laboratory standard (P=.394) did not significantly predict antibiotic susceptibility, while increased hospital patient days generally predicted increased organism susceptibility (0.728% per 10,000 PD;P<.001).

CONCLUSIONS

We found that hospital-specific antibiotic usage was generally associated with increased, rather than decreased hospital antibiotic susceptibility. These findings may be explained by community origins for many hospital-diagnosed infections and practitioners choosing agents based on local antibiotic resistance patterns.

Infect Control Hosp Epidemiol2017;38:1457–1463
Two-phase gravity currents resulting from the release of a fixed volume of fluid in a porous medium
Authors: Golding Madeleine J. , Huppert Herbert E. , Neufeld Jerome A.
Published: October 2017

We consider the instantaneous release of a finite volume of fluid in a porous medium saturated with a second, immiscible fluid of different density. The resulting two-phase gravity current exhibits a rich array of behaviours due to both the residual trapping of fluid as the current recedes and the differing effects of surface tension between advancing and receding regions of the current. We develop a framework for the evolution of such a current with particular focus on the large-scale implications of the form of the constitutive relation between residual trapping and initial saturation. Pore-scale hysteresis within the current is represented by families of scanning curves relating capillary pressure and relative permeability to saturation. In the resulting vertically integrated model, all capillary effects are incorporated within specially defined saturation and flux functions specific to each region. In the long-time limit, when the height of the current and the saturations within it are low, the saturation and flux functions can be approximated by mathematically convenient power laws. If the trapping model is approximately linear at low saturations, the equations admit a similarity solution for the propagation rate and height profile of the late-time gravity current. We also solve the governing partial differential equation numerically for the nonlinear Land’s trapping model, which is commonly used in studies of two-phase flows. Our investigation suggests that for trapping relations for which the proportion of trapped to initial fluid saturation increases and tends to unity as the initial saturation decreases, both of which are properties of Land’s model, a gravity current slows and eventually stops. This trapping behaviour has important applications, for example to the ultimate distance contaminants or stored carbon dioxide may travel in the subsurface.
Shock–boundary layer interaction and energetics in transonic flutter
Authors: Karnick Pradeepa T. , Venkatraman Kartik
Published: October 2017

We study the influence of shock and boundary layer interactions in transonic flutter of an aeroelastic system using a Reynolds-averaged Navier–Stokes (RANS) solver together with the Spalart–Allmaras turbulence model. We show that the transonic flutter boundary computed using a viscous flow solver can be divided into three distinct regimes: a low transonic Mach number range wherein viscosity mimics increasing airfoil thickness thereby mildly influencing the flutter boundary; an intermediate region of drastic change in the flutter boundary due to shock-induced separation; and a high transonic Mach number zone of no viscous effects when the shock moves close to the trailing edge. Inviscid transonic flutter simulations are a very good approximation of the aeroelastic system in predicting flutter in the first and third regions: that is when the shock is not strong enough to cause separation, and in regions where the shock-induced separated region is confined to a small region near the trailing edge of the airfoil. However, in the second interval of intermediate transonic Mach numbers, the power distribution on the airfoil surface is significantly influenced by shock-induced flow separation on the upper and lower surfaces leading to oscillations about a new equilibrium position. Though power contribution by viscous forces are three orders of magnitude less than the power due to pressure forces, these viscous effects manipulate the flow by influencing the strength and location of the shock such that the power contribution by pressure forces change significantly. Multiple flutter points that were part of the inviscid solution in this regime are now eliminated by viscous effects. Shock motion on the airfoil, shock reversal due to separation, and separation and reattachment of flow on the airfoil upper surface, also lead to multiple aerodynamic forcing frequencies. These flow features make the flutter boundary quantitatively sensitive to the turbulence model and numerical method adopted, but qualitatively they capture the essence of the physical phenomena.
Continuum theory for rapid cohesive-particle flows: general balance equations and discrete-element-method-based closure of cohesion-specific quantities
Authors: Kellogg Kevin M. , Liu Peiyuan , LaMarche Casey Q. , Hrenya Christine M.
Published: October 2017

The continuum description of rapid cohesive-particle flows comprises the population balance, which tracks various agglomerate sizes in space and time, and kinetic-theory-based balances for momentum and granular energy. Here, fundamental closures are provided in their most general form. In previous population balances, the probability (‘success factor’) that a given collision results in agglomeration or breakage has been set to a constant even though it is well established that the outcome of a collision depends on the impact (relative) velocity. Here, physically based closures that relate the success factors to the granular temperature, a (continuum) measure of the impact velocity, are derived. A key aspect of this derivation is the recognition that the normal component of the impact velocity dictates whether agglomeration occurs. With regard to the kinetic-theory balances, cohesion between particles makes the collisions more dissipative, thereby decreasing the granular temperature. The extra dissipation due to cohesion is accounted for using an effective coefficient of restitution, again determined using the derived distribution of normal impact velocities. This collective treatment of the population and kinetic-theory balances results in a general set of equations that contain several parameters (e.g. critical velocities of agglomeration) that are cohesion-specific (van der Waals, liquid bridging, etc.). The determination of these cohesion-specific quantities using simple discrete element method simulations, as well as validation of the resulting theory, is also presented.
Dynamics of falling films on the outside of a vertical rotating cylinder: waves, rivulets and dripping transitions
Authors: Rietz Manuel , Scheid Benoit , Gallaire François , Kofman Nicolas , Kneer Reinhold , Rohlfs Wilko
Published: October 2017

Falling liquid films on the underside of a plate or on the outside of a rotating cylinder are subject to a destabilizing body force. The evolution of the film topology is determined by interactions between the Kapitza and the Rayleigh–Taylor instability, leading to complex patterning of the film surface and eventually fluid detachment from the substrate. This study experimentally investigates the evolution of the surface topology for a film on the outside of a vertical rotating cylinder of large radius. Shear at the liquid/air interface is suppressed through an outer, co-rotating cylinder. The film evolution is captured through high speed visualization in dependence of the control parameters, namely Reynolds number and rotation frequency. An increasing influence of the Rayleigh–Taylor instability for an increasing destabilizing body force (increasing rotational speed of the cylinder) is most notably observed in the form of a decreasing inception length of rivulet structures dominating the film topology. Wavelength as well as inception length of rivulets match the predictions from linear stability analysis of the classical Rayleigh–Taylor problem. In this context, experimental and supporting numerical results suggest that the emergence of rivulets occurs for any non-zero value of the destabilizing body force after a given evolution length that decreases with increasing body force. Fluid detachment from the substrate is found to be intimately related to the existence of rivulet structures. In dependence of the control parameters, detaching droplets are either observed as a result of interactions of solitary pulses of varying phase speed on rivulets, directly after destabilization of two-dimensional waves into rivulets or immediately at the fluid inlet. By comparison to the convective/absolute instability transition predicted by linear stability analysis of an integral boundary layer formulation of the problem in question, it is shown that the prediction of a predominant dripping mechanism lies beyond the scope of linear analysis.
Thermosolutal convection in an evolving soluble porous medium
Authors: Corson Lindsey T. , Pritchard David
Published: October 2017

We describe a mathematical model of double-diffusive (thermosolutal) convection in a saturated porous layer, when the solubility of the solute depends on the temperature, and the porosity and permeability of the porous medium evolve through dissolution and precipitation. We present the results of linear and weakly nonlinear stability analyses and explore the longer-term development of the system numerically. When the solutal concentration gradient is destabilising, the dynamics are somewhat similar to those previously found for single-species convection (Ritchie & Pritchard, J. Fluid Mech., vol. 673, 2011, pp. 286–317), including the occurrence of subcritical instabilities driven by a reaction–diffusion mechanism. However, when the solutal concentration gradient is stabilising and the thermal gradient is destabilising, novel dynamics emerge. These include a vertical segregation of circulation cells and porosity perturbations near the onset of convection, and over longer time scales the formation of a low-permeability region in the middle of the layer, pierced by occasional high-permeability channels. Under these conditions, convection may die away to nearly zero for extended periods before resuming vigorously in localised regions at later times.
The near-field pressure radiated by planar high-speed free-shear-flow turbulence
Authors: Buchta David A. , Freund Jonathan B.
Published: October 2017

Jets with Mach numbers $M\gtrsim 1.5$ are well known to emit an intense, fricative, so-called crackle sound, having steep compressions interspersed with weaker expansions that together yield a positive pressure skewness $S_{k}>0$. Its shock-like features are obvious hallmarks of nonlinearity, although a full explanation of the skewness is lacking, and wave steepening alone is understood to be insufficient to describe its genesis. Direct numerical simulations of high-speed free-shear flows for Mach numbers $M=0.9$, $1.5$, $2.5$ and $3.5$ in the Reynolds number range $60\leqslant Re_{\unicode[STIX]{x1D6FF}_{m}}\leqslant 4200$ are used to examine the mechanisms leading to such pressure signals, especially the pressure skewness. For $M=2.5$ and $3.5$, the pressure immediately adjacent the turbulence already has the large $S_{k}\gtrsim 0.4$ associated with jet crackle. It also has a surprisingly complex three-dimensional structure, with locally high pressures at compression-wave intersections. This structure is transient, and it simplifies as radiating waves subsequently merge through nonlinear mechanisms to form the relatively distinct and approximately two-dimensional Mach-like waves deduced from laboratory visualizations. A transport equation for $S_{k}$ is analysed to quantify factors affecting its development. The viscous dissipation that decreases $S_{k}$ is balanced by a particular nonlinear flux, which is (of course) absent in linear acoustic propagation and confirmed to be independent of the simulated Reynolds numbers. Together these effects maintain an approximately constant $S_{k}$ in the near acoustic field.
Optimal transient growth on a vortex ring and its transition via cascade of ringlets
Authors: Mao X. , Hussain F.
Published: October 2017

Linear and nonlinear transient growths of perturbations on a vortex ring up to Reynolds number ($\equiv$ circulation/viscosity) $Re=27\,000$ are studied. For short time intervals, perturbations around the ring axis undergo the strongest linear transient growth and lead to secondary structures in the form of ringlets, owing to the Orr mechanism and an inviscid vorticity-amplification mechanism: in contrast to the well-reported instabilities and lobe structures along the vortex ring core. These secondary ringlet structures induce a tertiary group of ringlets through similar transient perturbation growth. This cascade of ringlets lead to the breakup of the main ring even before activation of the vortex-core instabilities. Such a cascade scenario is also observed in the development of a vortex ring perturbed by random disturbance in the axis region. These new modes and mechanisms for the generation and breakup of vortex ring structures bring insights into the dynamics and control of vortex ring flows.
Vortex-dipole collapse induced by droplet inertia and phase change
Authors: Ravichandran S. , Govindarajan Rama
Published: October 2017

Droplet-laden flows with phase change are common. This study brings to light a mechanism by which droplet inertial dynamics and local phase change, taking place at sub-Kolmogorov scales, affect vortex dynamics in the inertial range of turbulence. To do this we consider vortices placed in a supersaturated ambient initially at constant temperature, homogeneous vapour concentration and uniformly distributed droplets. The droplets also act as sites of phase change. This allows the time scales associated with particle inertia and phase change, which could be significantly different from each other and from the time scale of the flow, to become coupled, and for their combined dynamics to govern the flow. The thermodynamics of condensation and evaporation have a characteristic time scale $\unicode[STIX]{x1D70F}_{s}$. The water droplets are treated as Stokesian inertial particles with a characteristic time scale $\unicode[STIX]{x1D70F}_{p}$, whose behaviour we approximate using an $O(\unicode[STIX]{x1D70F}_{p})$ truncation of the Maxey–Riley equation for heavy particles. This inertia leads the water droplets to vacate the vicinity of vortices, leaving no nuclei for the vapour to condense. The condensation process is thus spatially inhomogeneous, and leaves vortices in the flow colder than their surroundings. The combination of buoyancy and vorticity generates a lift force on the vortices perpendicular to their velocity relative to the fluid around them. In the case of a vortex dipole, this lift force can propel the vortices towards each other and undergo collapse, a phenomenon studied by Ravichandran et al. (Phys. Rev. Fluids, vol. 2, 2017, 034702). We find, spanning the space of the two time scales, $\unicode[STIX]{x1D70F}_{p}$ and $\unicode[STIX]{x1D70F}_{s}$, the region in which lift-induced dipole collapse can occur, and show numerically that the product of the time scales is the determining parameter. Our findings agree with our results from scaling arguments. We also study the influence of varying the initial supersaturation, and find that the strength of the lift-induced mechanism has a power-law dependence on the phase-change time scale $\unicode[STIX]{x1D70F}_{s}$. We then study systems of many vortices and show that the same coupling between the two time scales alters the dynamics of such systems, by energising the smaller scales. We show that this effect is significantly more pronounced at higher Reynolds numbers. Finally, we discuss how this effect could be relevant in conditions typical of clouds.
The aeroacoustics of finite wall-mounted square cylinders
Authors: Porteous Ric , Moreau Danielle J. , Doolan Con J.
Published: October 2017

This paper presents the results of an experimental study that relates the flow structures in the wake of a square finite wall-mounted cylinder with the radiated noise. Acoustic and hot-wire measurements were taken in an anechoic wind tunnel. The cylinder was immersed in a near-zero-pressure gradient boundary layer whose thickness was 130 % of the cylinder width,$W$. Aspect ratios were in the range$0.29\leqslant L/W\leqslant 22.9$(where$L$is the cylinder span), and the Reynolds number, based on width, was$1.4\times 10^{4}$. Four shedding regimes were identified, namely R0 ($L/W<2$), RI ($2<L/W<10$), RII ($10<L/W<18$) and RIII ($L/W>18$), with each shedding regime displaying an additional acoustic tone as the aspect ratio was increased. At low aspect ratios (R0 and RI), downwash dominated the wake, creating a highly three-dimensional shedding environment with maximum downwash at$L/W\approx 7$. Looping vortex structures were visualised using a phase eduction technique. The principal core of the loops generated the most noise perpendicular to the cylinder. For higher aspect ratios in RII and RIII, the main noise producing structures consisted of a series of inclined vortex filaments, where the angle of inclination varied between vortex cells.
Effect of base topography on dynamics and transition in a dense granular flow
Authors: Bharathraj S. , Kumaran V.
Published: October 2017

The effect of base roughness on the transition and dynamics of a dense granular flow down an inclined plane is examined using particle based simulations. Different types of base topographies, rough bases made of frozen particles in either random or hexagonally ordered configurations, as well as sinusoidal bases with height modulation in both the flow and the spanwise directions, are examined. The roughness (characteristic length of the base features scaled by the flowing particle diameter) is defined as the ratio of the base amplitude and particle diameter for sinusoidal bases, and the ratio of frozen and moving particle diameters for frozen-particle bases. There is a discontinuous transition from an ordered to a disordered flow at a critical base roughness for all base topographies studied here, indicating that it is a universal phenomenon independent of base topography. The transition roughness does depend on the base configuration and the height of the flow, but is independent of the contact model and is less than 1.5 times the flowing particle diameter for all of the bases considered here. The bulk rheology is independent of the base topography, and follows the Bagnold law for both the ordered and the disordered flows. The base topography does have a dramatic effect on the flow dynamics at the base. For flows over frozen-particle bases, there is ordering down to the base for ordered flows, and the granular temperature is comparable to that in the bulk. There is virtually no velocity slip at the base, and the mean angular velocity is equal to one-half of the vorticity down to the base. For flows over sinusoidal bases, there is significant slip at the base, and the mean angular velocity is approximately an order of magnitude higher than that in the bulk within a region of height approximately one particle diameter at the base. This large particle spin results in a disordered and highly energetic layer of approximately 5–10 particle diameters at the base, where the granular temperature is an order of magnitude higher than that in the bulk. Thus, this study reveals the paradoxical result that gentler base topographies result in large slip and large agitation at the base, whereas rougher topographies such as frozen-particle bases result in virtually no slip and no agitation at the base for both ordered and disordered flows.
Streak instability in turbulent channel flow: the seeding mechanism of large-scale motions
Authors: de Giovanetti Matteo , Sung Hyung Jin , Hwang Yongyun
Published: October 2017

It has often been proposed that the formation of large-scale motion (or bulges) is a consequence of successive mergers and/or growth of near-wall hairpin vortices. In the present study, we report our direct observation that large-scale motion is generated by an instability of an ‘amplified’ streaky motion in the outer region (i.e. very-large-scale motion). We design a numerical experiment in turbulent channel flow up to $Re_{\unicode[STIX]{x1D70F}}\simeq 2000$ where a streamwise-uniform streaky motion is artificially driven by body forcing in the outer region computed from the previous linear theory (Hwang & Cossu, J. Fluid Mech., vol. 664, 2015, pp. 51–73). As the forcing amplitude is increased, it is found that an energetic streamwise vortical structure emerges at a streamwise wavelength of $\unicode[STIX]{x1D706}_{x}/h\simeq 1{-}5$ ($h$ is the half-height of the channel). The application of dynamic mode decomposition and the examination of turbulence statistics reveal that this structure is a consequence of the sinuous-mode instability of the streak, a subprocess of the self-sustaining mechanism of the large-scale outer structures. It is also found that the statistical features of the vortical structure are remarkably similar to those of the large-scale motion in the outer region. Finally, it is proposed that the largest streamwise length of the streak instability determines the streamwise length scale of very-large-scale motion.
A scaling for vortex formation on swept and unswept pitching wings
Authors: Onoue Kyohei , Breuer Kenneth S.
Published: October 2017

We examine the dynamics of the leading-edge vortex (LEV) on a rapidly pitching plate with the aim of elucidating the underlying flow physics that dictates the stability and circulation of the LEV. A wide variety of flow conditions is considered in the present study by systematically varying the leading-edge sweep angle ($\unicode[STIX]{x1D6EC}=0^{\circ }$,$11.3^{\circ }$,$16.7^{\circ }$) and the reduced frequency ($f^{\ast }=0.064{-}0.151$), while keeping the pitching amplitude and the Reynolds number fixed. Tomographic particle image velocimetry is used to characterise the three-dimensional fluid motion inside the vortex core and its relation to the LEV stability and growth. A series of control volume analyses are performed to quantify the relative importance of the vorticity transport phenomena taking place inside the LEV to the overall vortex development. We show that, near the wing apex where tip effects can be neglected, the vortex develops in a nominally two-dimensional manner, despite the presence of inherently three-dimensional vortex dynamics such as vortex stretching and compression. Furthermore, we demonstrate that the vortex formation time and circulation growth are well-described by the principles of optimal vortex formation number, and that the occurrence of vortex shedding is dictated by the relative energetics of the feeding shear layer and the resulting vortex.
Dissolution instability and roughening transition
Authors: Claudin Philippe , Durán Orencio , Andreotti Bruno
Published: October 2017

We theoretically investigate the pattern formation observed when a fluid flows over a solid substrate that can dissolve or melt. We use a turbulent mixing description that includes the effect of the bed roughness. We show that the dissolution instability at the origin of the pattern is associated with an anomaly at the transition from a laminar to a turbulent hydrodynamic response with respect to the bed elevation. This anomaly, and therefore the instability, disappears when the bed becomes hydrodynamically rough, above a threshold roughness-based Reynolds number. This suggests a possible mechanism for the selection of the pattern amplitude. The most unstable wavelength scales as observed in nature on the thickness of the viscous sublayer, with a multiplicative factor that depends on the dimensionless parameters of the problem.