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Microstructural Kinetics Group

Department of Materials Science & Metallurgy
 
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This is a superlist combining all those seminars on talks.cam taking place in one of the Departments of the School of Physical sciences, plus occasional other talks which would be of significant interest to researchers in the School. If you would like your talk or list included please contact Duncan (drs45)
Updated: 35 sec ago

Fri 03 Dec 16:00: Prediction of drag for rough wall boundary layer flows

Tue, 12/10/2021 - 22:22
Prediction of drag for rough wall boundary layer flows

Significant progress has been made towards the understanding of rough-wall boundary layers and the subsequent drag penalty. Continued progress is promising since a larger range of parameter space can now be investigated experimentally and numerically. Recent advances in rapid prototyping techniques enables the generation of systematic variations of roughness scales and computationally efficient simulations with creative surface mapping techniques allows for experiments and computations to investigate similar complex roughness. While a universal drag prediction correlation is still elusive and may not be possible, predictive correlations for classes of surface roughness pertinent to engineering applications seem achievable. Three surface parameters based solely on surface statistics are showing promise in predictive correlations for a range of studies. These include a measure of surface elevation a slope parameter and the skewness of the surface elevation probability density function. Other candidate parameters that may be useful in a predictive correlation or a surface filter are the streamwise and spanwise correlation lengths. The challenges to represent this wide range of surface conditions and potential scales to characterize engineering roughness including biofouling in predictive correlations will be discussed.

webinar link: www.cambridge.org/core/journals/journal-of-fluid-mechanics/fluid-mechanics-webinar-series

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Fri 26 Nov 16:00: Reflections on the Geodynamo

Tue, 12/10/2021 - 17:20
Reflections on the Geodynamo

Numerical simulations of the geodynamo are, perhaps, finally beginning to approach a dynamically relevant regime. It seems timely, therefore, to compare the results of those simulations with the various conceptual cartoons of the geodynamo that have been developed over the decades. One such cartoon is presented here, based in part on helical wave dispersion within the Earth’s core. This cartoon is far from the standard model, but nevertheless seems consistent with the evidence of the numerical simulations. Of course, understanding the numerical simulations is not at all the same as understanding the geodynamo, but perhaps it is a start.

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Fri 12 Nov 16:00: Measuring and Modeling the coordination of cilia: from collective waves in the brain to information processing?

Tue, 12/10/2021 - 17:20
Measuring and Modeling the coordination of cilia: from collective waves in the brain to information processing?

In the last decade we have investigated the emergence of synchronised collective states in the dynamics of two or more motile cilia. Motile cilia are filaments of around 10 microns in length, they beat by the coordinated action of molecular motors along the filament. In systems of several cilia, the beat across cilia can become phase locked, leading to fluid transport or propulsion. We have pushed two directions in my team: (1) experiments on lung and brain tissue models, and (2) models that reduce the complexity of each cilium to the extreme, to enable attempts at describing the collective motion. For such a specific organelle (although present in a wide range of eukaryotic cells) the range of physics and phenomena that arise are really diverse. The ciliary collective motions I will show are at play in mammalian embryonic development, in the lungs and brains, but can also carry information directionally and be used to form logical circuits in a form of physical computation. In this talk we will review recent progress and some unpublished results.

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Fri 29 Oct 16:00: Fluid-mechanical models of ice-sheet sliding and dynamics

Tue, 12/10/2021 - 17:20
Fluid-mechanical models of ice-sheet sliding and dynamics

The volume of ice stored in glaciers and ice sheets is the primary control on Earth’s sea level, so the question of how it responds to the changing climate is of profound interest. Fundamental to addressing this question is the fluid-like creep of the ice, and the rate at which it can slip over the underlying ‘bed’. In this talk we will first discuss basic models of ice-sheet volume and evolution, and how these are coupled to the climate. Secondly, we’ll consider the detailed problem of how slip at the ice-bed interface is facilitated by the formation of water-filled cavities; even after various simplifications this results in a very interesting free-boundary problem. Finally, we’ll look at a simplified model for marine ice-sheet dynamics when a Coulomb-like plastic law is assumed for the slip.

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Fri 22 Oct 16:00: Are confluent cell layers extensile or contractile?

Tue, 12/10/2021 - 17:20
Are confluent cell layers extensile or contractile?

A lot is understood about the ways in which single cells move over a surface, but the motion of confluent layers of epithelial cells, which are coupled through strong intercellular junctions, remains puzzling.

The cells in epithelial layers can be jammed in a glass-like state, they can flock, or they can show active turbulent-like motility with chaotic flows and motile topological defects. Active turbulence characterises active nematics, and we have been trying to understand why cells that are, on average, isotropic can show nematic properties. Moreover, it is surprising that single cells are contractile, whereas the direction of motion of topological defects in many confluent cell layers suggests that the layers are behaving as an extensile material.

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Fri 15 Oct 16:00: Urban trees: how do they affect air quality?

Tue, 12/10/2021 - 17:20
Urban trees: how do they affect air quality?

In this seminar I will discuss the effect that trees have on air flow of air pollutant transport. The interaction of trees with their environment is extremely complex: trees provide shading, absorb and emit radiation, evaporate water, cause drag and absorb/deposit pollutants. All these processes are incorporated in to a minimalistic tree model. Analysis of the tree model reveals the parameter space that map the cooling regimes of the tree. The model is then incorporated into an urban large-eddy simulation code uDALES, and the effect of trees on urban air quality is investigated. It is shown that trees can be both beneficial and detrimental to urban air quality, depending on how much they block the interaction between the street and the atmosphere.

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Fri 29 Oct 16:00: Fluid-mechanical models of ice-sheet sliding and dynamics

Tue, 12/10/2021 - 17:19
Fluid-mechanical models of ice-sheet sliding and dynamics

The volume of ice stored in glaciers and ice sheets is the primary control on Earth’s sea level, so the question of how it responds to the changing climate is of profound interest. Fundamental to addressing this question is the fluid-like creep of the ice, and the rate at which it can slip over the underlying ‘bed’. In this talk we will first discuss basic models of ice-sheet volume and evolution, and how these are coupled to the climate. Secondly, we’ll consider the detailed problem of how slip at the ice-bed interface is facilitated by the formation of water-filled cavities; even after various simplifications this results in a very interesting free-boundary problem. Finally, we’ll look at a simplified model for marine ice-sheet dynamics when a Coulomb-like plastic law is assumed for the slip.

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Tue 19 Oct 14:30: (A)typical intersections and where to find them https://maths-cam-ac-uk.zoom.us/j/92192959944?pwd=OVJ3d0pJS3RRaWhKOVBuMFJIM3FiQT09

Tue, 12/10/2021 - 17:18
(A)typical intersections and where to find them

I will present two seemingly unrelated results: (1) There exists a smooth projective curve C of genus 4, defined over some number field K, whose Jacobian J satisfies: End(J)=\Z and the image of the absolute Galois group of K in End(T_\ell (J)) is not open in GSp_8(Z_\ell). (2)The Hodge locus of positive period dimension of the universal family of degree d hypersurfaces in \mathbb{P}^{n+1} is algebraic as soon as n>2 and d>5.

The proof of both results builds on an ‘’Extended Zilber—Pink philosophy’’ for varieties supporting a variation of Hodge structure which predicts the behaviour of typical and atypical intersections (whose combination describes the whole Hodge locus). This is a joint work with B. Klingler and E. Ullmo.

https://maths-cam-ac-uk.zoom.us/j/92192959944?pwd=OVJ3d0pJS3RRaWhKOVBuMFJIM3FiQT09

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Wed 20 Oct 16:30: Statistics Clinic Michaelmas 2021 I

Tue, 12/10/2021 - 16:18
Statistics Clinic Michaelmas 2021 I

If you would like to participate, please fill in the following form. The deadline for signing up of a remote session is 3pm on Monday the 18th of October. Subject to availability of members of the Statistics Clinic team, we will confirm your in-person or remote appointment.

This event is open only to members of the University of Cambridge (and affiliated institutes). Please be aware that we are unable to offer consultations outside clinic hours.

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Fri 15 Oct 13:00: Stabilizing relativistic fluids on slowly expanding cosmological spacetimes

Tue, 12/10/2021 - 12:42
Stabilizing relativistic fluids on slowly expanding cosmological spacetimes

On a background Minkowski spacetime, the relativistic Euler equations are known, for a relatively general equation of state, to admit unstable homogeneous solutions with finite-time shock formation. By contrast, such shock formation can be suppressed on background cosmological spacetimes whose spatial slices expand at an accelerated rate. The critical case of linear, ie zero-accelerated, spatial expansion, is not as well understood. In this talk, I will present two recent works concerning the relativistic Euler and the Einstein-Dust equations for geometries expanding at a linear rate. This is based on joint works with David Fajman, Todd Oliynyk and Max Ofner.

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Wed 02 Mar 14:30: Title to be confirmed

Tue, 12/10/2021 - 12:21
Title to be confirmed

Abstract not available

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Wed 16 Feb 14:30: Title to be confirmed

Tue, 12/10/2021 - 12:14
Title to be confirmed

Abstract not available

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Fri 22 Oct 16:00: Searches for new interactions within the SMEFT framework at the LHC

Tue, 12/10/2021 - 10:41
Searches for new interactions within the SMEFT framework at the LHC

The existence of Beyond Standard Model (BSM) physics is firmly suggested by both experimental observations (Dark Matter, neutrino masses) and theoretical arguments. In the hypothesis that the scale of new physics is considerably higher than the energies probed at colliders, we can parametrise modified interactions induced by BSM effects among SM particles in a model-independent framework, the Standard Model Effective Field Theory (SMEFT). Searches for indirect evidence of new physics are conceptually different from the direct ones that have characterised the first part of the LHC program, and both experimental and phenomenological studies are needed in order to maximise the chances of uncovering a BSM signal. A characteristic feature of modified interactions is that they can induce unitarity violating effects which can be exploited to gain sensitivity. In this direction, a study of the top quark electroweak sector will be presented, focusing on 2 → 2 scatterings and their embeddings in physical processes at colliders. One of the key features of the SMEFT is that deviations from the SM interactions are correlated and global interpretations are therefore of fundamental importance. A combined interpretation of the Higgs, top and diboson data from the LHC will be presented and the interplay between the various datasets discussed.

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Wed 20 Oct 14:30: Nucleation in first order phase transitions starting from the top

Tue, 12/10/2021 - 07:57
Nucleation in first order phase transitions starting from the top

The first step of the transition from a mestastable arrangement of particles to a stable one is the nucleation of the latter somewhere within the former. We use computer simulations to investigate this phenomenon. The common denominator in all our studies is that we start with the nucleus already formed, an approach we call “Seeding”. Although information on the path leading to the formation of the nucleus is obviously lost, we gain a wide overview on the nucleation rate trend, which provides physical understanding of the nucleation behaviour upon changes of the thermodynamic conditions. With this approach, for instance, we have been able to understand the effect of pressure [1,2] or solutes [3,4] on ice nucleation from supercooled water; investigate the irreconcilable discrepancies between experiments and simulations of hard sphere crystallization [5]; or even propose a new way of polymorph selection in charged colloids [6]. I will discuss these interesting phase transition phenomena in my presentation introducing first the basic theoretical concepts to understand nucleation.

[1] Espinosa, Jorge R.; Zaragoza, Alberto; Rosales-Pelaez, Pablo; Navarro, Caridad; Valeriani, Chantal; Vega, Carlos; Sanz, Eduardo; Physical Review Letters, 117, 135702, 2016

[2] V Bianco, PM de Hijes, CP Lamas, E Sanz, C Vega, Physical Review Letters 126 (1), 015704, 2021

[3] Soria, G. D., Espinosa, J. R., Ramirez, J., Valeriani, C., Vega, C., & Sanz, E.; The Journal of Chemical Physics, 148(22), 222811., 2018

[4] JR Espinosa, GD Soria, J Ramirez, C Valeriani, C Vega, E Sanz; The Journal of Physical Chemistry Letters 8 (18), 4486-4491, 2017

[5] JR Espinosa, C Vega, C Valeriani, D Frenkel, E Sanz, Soft matter 15 (47), 9625-9631, 2019

[6] I Sanchez-Burgos, A Garaizar, C Vega, E Sanz, JR Espinosa, Soft Matter 17 (3), 489-505, 2021

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Wed 20 Oct 16:30: Statistics Clinic Michaelmas 2021 I

Mon, 11/10/2021 - 13:40
Statistics Clinic Michaelmas 2021 I

If you would like to participate, please fill in the following form: (form will be added soon). The deadline for signing up of a remote session is 3pm on Monday the 18th of October. Subject to availability of members of the Statistics Clinic team, we will confirm your in-person or remote appointment.

This event is open only to members of the University of Cambridge (and affiliated institutes). Please be aware that we are unable to offer consultations outside clinic hours.

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Wed 13 Oct 16:00: ApoE, Ab and Alzheimer’s disease: From test tube to transgenic mice

Mon, 11/10/2021 - 11:20
ApoE, Ab and Alzheimer’s disease: From test tube to transgenic mice

Seminar Outline (Major concepts to be discussed):

Background:
  • Alzheimer’s disease (AD) is the most common cause of dementia. While rare, familial AD is caused by genetic mutations that increase the production of Ab42.
  • Age, APOE genotype and sex are the universal biological variables (UBV) of AD risk.
SDS -stable apoE/Ab complexes are apoE isoform specific (apoE3/Ab > apoE4/Ab).
  • Biochemical detection
  • In vitro function
Ab42 oligomers and fibrils
  • Biochemical assembly
  • In vitro function
The development of reagents for in vivo studies:
  • Optimization of a 3-step sequential protein extraction
  • Characterization of a new Ab-specific monoclonal antibody
  • Development of oligomer-specific ELISA
  • Generation of the EFAD transgenic mouse model

The EFAD transgenic mice develop AD-relevant pathology that increases significantly with age, APOE4 and female sex, mirroring human AD risk.

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Wed 20 Oct 16:30: Statistics Clinic Michaelmas 2021 I

Mon, 11/10/2021 - 10:21
Statistics Clinic Michaelmas 2021 I

If you would like to participate, please fill in the following form: (form will be added soon). The deadline for signing up of a remote session is 3pm on Monday the 18th of October. Subject to availability of members of the Statistics Clinic team, we will confirm your in-person or remote appointment.

This event is open only to members of the University of Cambridge (and affiliated institutes). Please be aware that we are unable to offer consultations outside clinic hours.

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Fri 15 Oct 16:00: The Geometric SMEFT description of curved Higgs Field Space(s) - Michael Trott

Mon, 11/10/2021 - 10:01
The Geometric SMEFT description of curved Higgs Field Space(s) - Michael Trott

The seminar will take place in the Potter Room at DAMPT and will be broadcast via Zoom here.

Abstract: In recent years, the effective field theory approach to the Standard Model, the SMEFT , has been used to study LHC data with ever increasing theoretical precision and sophistication. However, the complexity of this theory lead to several barriers to substantial theoretical progress. In particular, the explosion in the number of parameters in the SMEFT as a function of operator mass dimension, and the technical challenge or reformulating SM predictions consistently into the SMEFT were very serious problems, that called into question the possible success and value of the SMEFT physics program over the long term. I will discuss how these challenges have been overcome. The key point leading to this advance is the understanding that the projection of curved scalar field spaces generated by the Higgs onto a naive flat field space understanding implicitly embedded into the usual SMEFT Lagrangian and approach was the root cause of many problems, technical challenges and confusions. Many outstanding issues have now been addressed and immediately overcome by reformulating the SMEFT noting its curved scalar field space(s) – in the Geometric SMEFT . Some examples of the benefits of this approach will be presented, and explained.

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