Dr Geoff Moggridge | University of Cambridge (original) (raw)

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Papers by Dr Geoff Moggridge

Chemical Product Design, 2009

Journal of biomechanical engineering, Jan 28, 2016

Styrene based block co-polymers are promising materials for the development of a polymeric heart ... more Styrene based block co-polymers are promising materials for the development of a polymeric heart valve prosthesis (PHV); the mechanical properties of these polymers can be tuned via the manufacturing process, orienting the cylindrical domains to achieve material anisotropy. The aim of this work is the development of a computational tool for the optimisation of the material microstructure in a new PHV intended for aortic valve replacement to enhance the mechanical performance of the device. An iterative procedure was implemented to orient the cylinders along the maximum principal stress direction of the leaflet. A numerical model of the leaflet was developed; the polymer mechanical behaviour was described by a hyperelastic anisotropic constitutive law. A custom routine was implemented to align the cylinders with the maximum principal stress direction in the leaflet for each iteration. The study was focused on valve closure, since during this phase the fibrous structure of the leaflet...

The Journal of Physical Chemistry, 1995

ABSTRACT

Soft matter, Jan 17, 2015

Load-bearing tissues are composite materials that depend strongly on anisotropic fibre arrangemen... more Load-bearing tissues are composite materials that depend strongly on anisotropic fibre arrangement to maximise performance. One such tissue is the heart valve, with orthogonally arranged fibrosa and ventricularis layers. Their function is to maintain mechanical stress while being resilient. It is postulated that while one layer bears the applied stress, the orthogonal layer helps to regenerate the microstructure when the load is released. The present paper describes changes in the microstructure of a block copolymer with cylindrical morphology, having a bio-inspired microstructure of anisotropic orthogonally oriented layers, under uniaxial strain. To allow structural observations during fast deformation, equivalent to the real heart valve operation, we used a synchrotron X-ray source and recorded 2D SAXS patterns in only 1 ms per frame. The deformation behaviour of the composite microstructure has been reported for two arrangements of the cylinders in skin and core layers. The behav...

Kirk-Othmer Encyclopedia of Chemical Technology, 2000

ABSTRACT Today's chemical industry has goals that range from commodity chemicals to diver... more ABSTRACT Today's chemical industry has goals that range from commodity chemicals to diverse high value added engineered chemical products, such as an exfoliating gel, a disposable nappy or an artificial heart valve. In response to these goals, chemical product engineering has been emerging within chemical engineering. In this chapter, chemical product engineering is described as a body of knowledge structured in terms of three main pillars: the chemical product pyramid; chemical product design and process design integration; and multifaceted multiscale approach. According to this conceptual model, these pillars support chemical product design as the central objective and operational facet of chemical product engineering. A six step template for chemical product design is also presented here. This template starts with the identification of the customer needs a successful product must be able to satisfy, followed by the translation of these needs into objective, quantitative terms. It then proceeds to the generation and selection of alternative product ideas, culminating with the full specification of the product functionality and characteristics. As chemical product engineering increases in importance, it needs systematization and heuristics, just as the well-established traditional process engineering field has. Chemical products are immensely varied and the conceptual model and template discussed here do not offer a panacea; but they provide a framework within which thinking and practice are possible.

Soft Matter, 2014

A bi-directional, layered microstructure in cylinder forming block copolymers results from the lo... more A bi-directional, layered microstructure in cylinder forming block copolymers results from the local balance of shear and extensional flow during slow injection moulding.

Water Science & Technology, 2011

In recent years biofouling from native (bryozoans, sponges) and non-native (Cordylophora) animals... more In recent years biofouling from native (bryozoans, sponges) and non-native (Cordylophora) animals has increased in UK water treatment works (WTW). A survey of six UK water companies and eight WTWs revealed that these taxa were more widespread and abundant than previously recognised.

Thin Solid Films, 1994

ABSTRACT

Surface Science, 1995

Comparative Ni K-edge (8332.8 eV) total electron-yield (TEY) and conversion electron-yield (CEY) ... more Comparative Ni K-edge (8332.8 eV) total electron-yield (TEY) and conversion electron-yield (CEY) XAS spectra were collected from Ni wafers covered by NiO of varying thickness. In contrast to previous predictions, the surface sensitivity of TEY detection was found to be actually higher than for CEY detection. Examination of signal amplification factors upon switching from TEY to CEY detection indicates that the role of the surface insensitive inelastic KLL Auger electrons has been underestimated in the past. These energetic ...

Soft Matter, 2010

This research investigates the dynamics of mechanical and structural transformations of styrenebu... more This research investigates the dynamics of mechanical and structural transformations of styrenebutadiene-styrene block copolymer, known as RCM1, which has cylindrical mesophase morphology. The polymer was processed using a Multipass Rheometer (MPR) with simultaneous X-ray observation. The method allowed investigation of the dynamics with 1 second time resolution. Samples were processed at 160 C and an apparent wall shear rate in the range $1.4 to 1125 s À1 . Microstructural alignment was quantified using a second order X-ray orientation function. The polymer showed self-organization in the melt, aligning along the capillary walls. Shear flow disrupted the organization, which then rebuilt during the post-shearing pause, as the residual pressure relaxed across the capillary. The dynamics of structure ordering and disordering was a function of shear rate. The transition was faster for high shear rate cycles.

Review of Scientific Instruments, 2000

Electron-yield x-ray absorption spectroscopy with gas microstrip detectors. [Review of Scientific... more Electron-yield x-ray absorption spectroscopy with gas microstrip detectors. [Review of Scientific Instruments 71, 3640 (2000)]. Trevor Rayment, Sven LM Schroeder, Geoffrey D. Moggridge, J. Edmond Bateman, Gareth E. Derbyshire, Richard Stephenson. Abstract. ...

Physica B: Condensed Matter, 1995

A brief summary is given of a fundamental study of CEY detection which produced results contrary ... more A brief summary is given of a fundamental study of CEY detection which produced results contrary to published predictions. The aim of this communication is to encourage use of CEY detection for in situ catalysis research.

Optics Express, 2009

The ability to quantify the fluorescence signals from multiply labeled biological samples is high... more The ability to quantify the fluorescence signals from multiply labeled biological samples is highly desirable in the life sciences but often difficult, because of spectral overlap between fluorescent species and the presence of autofluorescence. Several so called unmixing algorithms have been developed to address this problem. Here, we present a novel algorithm that combines measurements of lifetime and spectrum to achieve unmixing without a priori information on the spectral properties of the fluorophore labels. The only assumption made is that the lifetimes of the fluorophores differ. Our method combines global analysis for a measurement of lifetime distributions with singular value decomposition to recover individual fluorescence spectra. We demonstrate the technique on simulated datasets and subsequently by an experiment on a biological sample. The method is computationally efficient and straightforward to implement. Applications range from histopathology of complex and multiply labelled samples to functional imaging in live cells. , "Fluorescence lifetime imaging distinguishes basal cell carcinoma from surrounding uninvolved skin." British Journal of Dermatology 159, 152-161 (2008). 23. A.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1995

Application of synchrotron radiation for in situ studies of catalysis requires construction of su... more Application of synchrotron radiation for in situ studies of catalysis requires construction of suitable environmental cells. We describe here examples of cells for extremes of temperature, pressure and chemical conditions. These cells are suitable for XAS and XRD and have proved reliable over a decade of use. For the first time we show in situ XAS cells for catalysis studies based on conversion electron yield (CEY) detection.

Liquid Crystals, 2009

We report on the capillary flow behaviour of thermotropic liquid crystal mixtures containing 4-n-... more We report on the capillary flow behaviour of thermotropic liquid crystal mixtures containing 4-n-octyl-4′-cyanobiphenyl (8CB) and 4-n-pentyl-4′-cyanobiphenyl (5CB). The liquid crystal mixtures are studied in the Nematic (N) and Smectic (SA) phases at room temperature. Polarised optical microscopy (POM), rheology and simultaneous X-ray diffraction (XRD)/capillary flow experiments are performed to characterise the system.Polarised optical microscopy reveals a dramatic change in optical texture when the 5CB content is increased from 20 to 30% in the mixtures. X-ray diffraction results show that the system goes through a SA–N phase transition, such that the mixtures are smectic for 10–20% 5CB and nematic for 30–90% 5CB. Smectic mixtures flow with the layers aligned along the flow direction (mesogens perpendicular to flow) while nematic mixtures flow with the mesogens aligned in the flow direction. Simultaneous XRD/shear flow experiments show that the SA–N transition is independent of the flow rate in the range 1–6 ml min.The correlation length of the liquid crystal order decreases with increasing 5CB content. Rheology is used to prove that the correlation length behaviour is related to a reduction in the viscosity of the mixture.

Chemical Product Design, 2009

Journal of biomechanical engineering, Jan 28, 2016

Styrene based block co-polymers are promising materials for the development of a polymeric heart ... more Styrene based block co-polymers are promising materials for the development of a polymeric heart valve prosthesis (PHV); the mechanical properties of these polymers can be tuned via the manufacturing process, orienting the cylindrical domains to achieve material anisotropy. The aim of this work is the development of a computational tool for the optimisation of the material microstructure in a new PHV intended for aortic valve replacement to enhance the mechanical performance of the device. An iterative procedure was implemented to orient the cylinders along the maximum principal stress direction of the leaflet. A numerical model of the leaflet was developed; the polymer mechanical behaviour was described by a hyperelastic anisotropic constitutive law. A custom routine was implemented to align the cylinders with the maximum principal stress direction in the leaflet for each iteration. The study was focused on valve closure, since during this phase the fibrous structure of the leaflet...

The Journal of Physical Chemistry, 1995

ABSTRACT

Soft matter, Jan 17, 2015

Load-bearing tissues are composite materials that depend strongly on anisotropic fibre arrangemen... more Load-bearing tissues are composite materials that depend strongly on anisotropic fibre arrangement to maximise performance. One such tissue is the heart valve, with orthogonally arranged fibrosa and ventricularis layers. Their function is to maintain mechanical stress while being resilient. It is postulated that while one layer bears the applied stress, the orthogonal layer helps to regenerate the microstructure when the load is released. The present paper describes changes in the microstructure of a block copolymer with cylindrical morphology, having a bio-inspired microstructure of anisotropic orthogonally oriented layers, under uniaxial strain. To allow structural observations during fast deformation, equivalent to the real heart valve operation, we used a synchrotron X-ray source and recorded 2D SAXS patterns in only 1 ms per frame. The deformation behaviour of the composite microstructure has been reported for two arrangements of the cylinders in skin and core layers. The behav...

Kirk-Othmer Encyclopedia of Chemical Technology, 2000

ABSTRACT Today's chemical industry has goals that range from commodity chemicals to diver... more ABSTRACT Today's chemical industry has goals that range from commodity chemicals to diverse high value added engineered chemical products, such as an exfoliating gel, a disposable nappy or an artificial heart valve. In response to these goals, chemical product engineering has been emerging within chemical engineering. In this chapter, chemical product engineering is described as a body of knowledge structured in terms of three main pillars: the chemical product pyramid; chemical product design and process design integration; and multifaceted multiscale approach. According to this conceptual model, these pillars support chemical product design as the central objective and operational facet of chemical product engineering. A six step template for chemical product design is also presented here. This template starts with the identification of the customer needs a successful product must be able to satisfy, followed by the translation of these needs into objective, quantitative terms. It then proceeds to the generation and selection of alternative product ideas, culminating with the full specification of the product functionality and characteristics. As chemical product engineering increases in importance, it needs systematization and heuristics, just as the well-established traditional process engineering field has. Chemical products are immensely varied and the conceptual model and template discussed here do not offer a panacea; but they provide a framework within which thinking and practice are possible.

Soft Matter, 2014

A bi-directional, layered microstructure in cylinder forming block copolymers results from the lo... more A bi-directional, layered microstructure in cylinder forming block copolymers results from the local balance of shear and extensional flow during slow injection moulding.

Water Science & Technology, 2011

In recent years biofouling from native (bryozoans, sponges) and non-native (Cordylophora) animals... more In recent years biofouling from native (bryozoans, sponges) and non-native (Cordylophora) animals has increased in UK water treatment works (WTW). A survey of six UK water companies and eight WTWs revealed that these taxa were more widespread and abundant than previously recognised.

Thin Solid Films, 1994

ABSTRACT

Surface Science, 1995

Comparative Ni K-edge (8332.8 eV) total electron-yield (TEY) and conversion electron-yield (CEY) ... more Comparative Ni K-edge (8332.8 eV) total electron-yield (TEY) and conversion electron-yield (CEY) XAS spectra were collected from Ni wafers covered by NiO of varying thickness. In contrast to previous predictions, the surface sensitivity of TEY detection was found to be actually higher than for CEY detection. Examination of signal amplification factors upon switching from TEY to CEY detection indicates that the role of the surface insensitive inelastic KLL Auger electrons has been underestimated in the past. These energetic ...

Soft Matter, 2010

This research investigates the dynamics of mechanical and structural transformations of styrenebu... more This research investigates the dynamics of mechanical and structural transformations of styrenebutadiene-styrene block copolymer, known as RCM1, which has cylindrical mesophase morphology. The polymer was processed using a Multipass Rheometer (MPR) with simultaneous X-ray observation. The method allowed investigation of the dynamics with 1 second time resolution. Samples were processed at 160 C and an apparent wall shear rate in the range $1.4 to 1125 s À1 . Microstructural alignment was quantified using a second order X-ray orientation function. The polymer showed self-organization in the melt, aligning along the capillary walls. Shear flow disrupted the organization, which then rebuilt during the post-shearing pause, as the residual pressure relaxed across the capillary. The dynamics of structure ordering and disordering was a function of shear rate. The transition was faster for high shear rate cycles.

Review of Scientific Instruments, 2000

Electron-yield x-ray absorption spectroscopy with gas microstrip detectors. [Review of Scientific... more Electron-yield x-ray absorption spectroscopy with gas microstrip detectors. [Review of Scientific Instruments 71, 3640 (2000)]. Trevor Rayment, Sven LM Schroeder, Geoffrey D. Moggridge, J. Edmond Bateman, Gareth E. Derbyshire, Richard Stephenson. Abstract. ...

Physica B: Condensed Matter, 1995

A brief summary is given of a fundamental study of CEY detection which produced results contrary ... more A brief summary is given of a fundamental study of CEY detection which produced results contrary to published predictions. The aim of this communication is to encourage use of CEY detection for in situ catalysis research.

Optics Express, 2009

The ability to quantify the fluorescence signals from multiply labeled biological samples is high... more The ability to quantify the fluorescence signals from multiply labeled biological samples is highly desirable in the life sciences but often difficult, because of spectral overlap between fluorescent species and the presence of autofluorescence. Several so called unmixing algorithms have been developed to address this problem. Here, we present a novel algorithm that combines measurements of lifetime and spectrum to achieve unmixing without a priori information on the spectral properties of the fluorophore labels. The only assumption made is that the lifetimes of the fluorophores differ. Our method combines global analysis for a measurement of lifetime distributions with singular value decomposition to recover individual fluorescence spectra. We demonstrate the technique on simulated datasets and subsequently by an experiment on a biological sample. The method is computationally efficient and straightforward to implement. Applications range from histopathology of complex and multiply labelled samples to functional imaging in live cells. , "Fluorescence lifetime imaging distinguishes basal cell carcinoma from surrounding uninvolved skin." British Journal of Dermatology 159, 152-161 (2008). 23. A.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1995

Application of synchrotron radiation for in situ studies of catalysis requires construction of su... more Application of synchrotron radiation for in situ studies of catalysis requires construction of suitable environmental cells. We describe here examples of cells for extremes of temperature, pressure and chemical conditions. These cells are suitable for XAS and XRD and have proved reliable over a decade of use. For the first time we show in situ XAS cells for catalysis studies based on conversion electron yield (CEY) detection.

Liquid Crystals, 2009

We report on the capillary flow behaviour of thermotropic liquid crystal mixtures containing 4-n-... more We report on the capillary flow behaviour of thermotropic liquid crystal mixtures containing 4-n-octyl-4′-cyanobiphenyl (8CB) and 4-n-pentyl-4′-cyanobiphenyl (5CB). The liquid crystal mixtures are studied in the Nematic (N) and Smectic (SA) phases at room temperature. Polarised optical microscopy (POM), rheology and simultaneous X-ray diffraction (XRD)/capillary flow experiments are performed to characterise the system.Polarised optical microscopy reveals a dramatic change in optical texture when the 5CB content is increased from 20 to 30% in the mixtures. X-ray diffraction results show that the system goes through a SA–N phase transition, such that the mixtures are smectic for 10–20% 5CB and nematic for 30–90% 5CB. Smectic mixtures flow with the layers aligned along the flow direction (mesogens perpendicular to flow) while nematic mixtures flow with the mesogens aligned in the flow direction. Simultaneous XRD/shear flow experiments show that the SA–N transition is independent of the flow rate in the range 1–6 ml min.The correlation length of the liquid crystal order decreases with increasing 5CB content. Rheology is used to prove that the correlation length behaviour is related to a reduction in the viscosity of the mixture.