Anke Husmann - Academia.edu (original) (raw)
Papers by Anke Husmann
Journal of Physics: Condensed Matter, Feb 20, 2006
The electronic structure of the Heusler alloy Co 2 TiSn is investigated here, with particular att... more The electronic structure of the Heusler alloy Co 2 TiSn is investigated here, with particular attention paid to its potential as a half-metallic ferromagnet. Ab initio calculations are performed using a plane wave pseudopotential code in the framework of density functional theory. These accurate calculations are done with convergence tolerances of 10 −5 and 10 −4 eV on the total energy and Fermi energy, respectively. The alloy is found not to be a half-metal. Minority spin electrons undergo distinctly hole-like dispersion at the point in k space while the majority spin bands are metallic with a multiply connected tube-like Fermi surface. Further, the computed minority band gap and spin polarization at the Fermi level are larger when the calculation is performed using the generalized gradient approximation.
Applied Physics Letters, Jun 20, 2005
Bulletin of the American Physical Society, Mar 18, 2021
Social Science Research Network, 2022
The architectural and physiomechanical properties of regenerative scaffolds have been shown to im... more The architectural and physiomechanical properties of regenerative scaffolds have been shown to improve engineered tissue function at both a cellular and tissue level. The fabrication of regenerative three-dimensional scaffolds that precisely replicate the complex hierarchical structure of native tissue, however, remains a challenge. The aim of this work is therefore twofold: i) demonstrate an innovative multidirectional freeze-casting system to afford precise architectural control of ice-templated collagen scaffolds; and ii) present a predictive simulation as an experimental design tool for bespoke scaffold architecture. We used embedded heat sources within the freeze-casting mold to manipulate the local thermal environment during solidification of icetemplated collagen scaffolds. The resultant scaffolds comprised complex and spatially varied lamellar orientations that correlated with the imposed thermal environment and could be readily controlled by varying the geometry and power of the heat sources. The complex macroarchitecture did not interrupt the hierarchical features characteristic of ice-templated scaffolds, but pore orientation had a significant impact on the stiffness of resultant structures under compression. Furthermore, our finite element model (FEM) accurately predicted the thermal environment and illustrated the freezing front topography within the mold during solidification. The lamellar orientation of freeze-cast scaffolds was also predicted using thermal gradient vector direction immediately prior to phase change. In combination our FEM and bespoke freeze-casting system present an exciting opportunity for tailored architectural design of ice-templated regenerative scaffolds that mimic the complex hierarchical environment of the native extracellular matrix.
Frontiers in Bioengineering and Biotechnology, 2016
Frontiers in Bioengineering and Biotechnology, 2016
Physica B: Condensed Matter, 2000
Muon-spin rotation (μSR) measurements have been used to study the superconducting vortex properti... more Muon-spin rotation (μSR) measurements have been used to study the superconducting vortex properties of the organic superconductors κ-(BEDT-TTF)2Cu(SCN)2, α-(BEDT-TTF)2NH4Hg(SCN)4 and β-(BEDT-TTF)2IBr2. These materials all have highly anisotropic structures consisting of metallic layers of BEDT-TTF molecules alternating with less well conducting anion layers. Varying the anion gives rise to a change in the anisotropy of the superconductivity and also to changes in the superconducting transition temperature. We have used both transverse and longitudinal magnetic fields to study the three-dimensional flux line lattice that is present at low temperatures and fields and to study also the loss of flux lattice order that occurs on increasing the temperature and field.
Series in Material Science and Engineering, 2006
Journal of Materials Science: Materials in Medicine, 2015
The structure of ice-templated collagen scaffolds is sensitive to many factors. By adding 0.5 wt%... more The structure of ice-templated collagen scaffolds is sensitive to many factors. By adding 0.5 wt% of sodium chloride or sucrose to collagen slurries, scaffold structure could be tuned through changes in ice growth kinetics and interactions of the solute and collagen. With ionic solutes (sodium chloride) the entanglements of the collagen molecule decreased, leading to fibrous scaffolds with increased pore size and decreased attachment of chondrocytes. With non-ionic solutes (sucrose) ice growth was slowed, leading to significantly reduced pore size and up-regulated cell attachment. This highlights the large changes in structure and biological function stimulated by solutes in ice-templating systems. Graphical Abstract
Journal of Physics: Condensed Matter, 2001
... Page 7. 2268 Th Jestädt et al temperature dependent but begins to rise rapidly as TC is appro... more ... Page 7. 2268 Th Jestädt et al temperature dependent but begins to rise rapidly as TC is approached. It is possible to relate the relaxation rate to the fluctuation rate of the electronic moments using λ = 2 2τ [17] which is valid in a regime where τ−1 ≫ and where a single time ...
Applied Physics Letters, 2006
We have investigated the 300 K inherent magnetoresistance of undoped InSb epilayers grown on GaAs... more We have investigated the 300 K inherent magnetoresistance of undoped InSb epilayers grown on GaAs(001) by molecular-beam epitaxy. The magnetoresistance of these films can be described well using a simplified model that incorporates gradation of properties away from the InSb/GaAs interface and the interplay between conduction and impurity bands. Although there is no significant intrinsic contribution in InSb bulk crystalline (001) materials due to its isotropic Fermi surface and mobility tensor, the linear and quadratic terms in the magnetoresistance as well as the overall magnitude can be tuned by varying the film thickness from 100 to 2000 nm.
In recent years, there has been a shift from traditional cell culture on two-dimensional substrat... more In recent years, there has been a shift from traditional cell culture on two-dimensional substrates towards the use of three-dimensional scaffolds for tissue engineering. Ice-templating is a versatile tool to create porous scaffolds from collagen. Here we discuss specific considerations for the design of moulds to produce freeze dried collagen scaffolds with pore sizes of around 100µm, a range that is relevant to tissue engineering. A numerical model of heat conduction, implemented in COMSOL Multiphysics ® version 5.0, calculated the temperature contour lines and heat flow vectors during cooling for a variety of mould geometries and materials. We show how temperature distribution within moulds determines the resulting pore structure of the scaffolds by regulating ice growth, and we validate our simulation against experimental results. These simulations are especially useful when working with moulds that contain volumes of more than 1cm in each direction. Key words
The following data files are provided: Python file containing the raw data for wavelengths and ve... more The following data files are provided: Python file containing the raw data for wavelengths and velocities measured at each pressure and Zip file containing all ESEM images taken at each pressure used for publication.
The Heusler alloy Co2TiSn is a ferromagnet with a Curie temperature of 355K. Our theoretical pred... more The Heusler alloy Co2TiSn is a ferromagnet with a Curie temperature of 355K. Our theoretical predictions by CASTEP as well as calculations done by others ootnotetextA. Yamasaki et al., Phys. Rev. B 65, 104410 (2002). show a high spin polarisation in the conduction band making it a promising candidate for a metallic spin injector. We study its magnetotransport properties as
Physica B: Condensed Matter, 2000
... Jestädt a , FL Pratt a , b , IM Marshall a , BW Lovett a , M. Kurmoo c , T. Sugano d and W. H... more ... Jestädt a , FL Pratt a , b , IM Marshall a , BW Lovett a , M. Kurmoo c , T. Sugano d and W. Hayes a. ... In a purely organic metamagnet, tanol suberate, we have observed a spin precession signal with a temperature dependence which has provided evidence of the two-dimensional ...
Physica B: Condensed Matter, 2000
μSR has been used to study a variety of polymers with very different electronic properties. In co... more μSR has been used to study a variety of polymers with very different electronic properties. In conducting polymers, the muon-generated radical states take the form of highly mobile polarons. Muon spin relaxation has been used to study the mobility of these polarons and to measure the temperature dependence of their intra-chain and inter-chain diffusion rates. It is found that the transport properties are strongly influenced by the librational ring modes of the phenylene rings in these polymers. In contrast, the muon-generated radical states in non-conducting polymers such as polybutadiene remain localised near the site of the muon. High field muon spin rotation, avoided level crossing resonance and longitudinal relaxation studies have been made, using the muon radical state as a probe of the dynamical properties of the polymer. Dramatic changes in the μSR signals are seen on going through the glass–rubber transition, as various dynamical degrees of freedom become frozen out. Additional information about the stability of the muon radical states on the microsecond timescale has also been obtained using RF muon spin rotation techniques. Using time-delayed RF resonance of the diamagnetic state at the RIKEN-RAL muon facility, the transition rate between paramagnetic and diamagnetic states could be studied as a function of temperature.
Materials Science and Engineering: C, 2014
Biopolymer scaolds have great therapeutic potential in the eld of tissue engineering due to the l... more Biopolymer scaolds have great therapeutic potential in the eld of tissue engineering due to the large interconnected porosity and natural biocompatibility of the polymers. Using an ice templated technique, where collagen is concentrated into a porous network by ice nucleation and growth, scaolds with anisotropic pore architecture can be created, mimicking natural tissue environments such as tendon or cardiac muscle. This paper describes a systematic set of experiments which have been undertaken to understand the eects of local temperature control on the anisotropy and architecture of ice templated biopolymer scaolds. The scaolds within this study were at least 10 mm in all dimensions, making them applicable to critical sized defects for biomedical applications. It was found that monitoring the temperature within slurry at specic locations during freezing was critical to predicting anisotropy of scaold architecture. Aligned porosity was produced only when the temperature at nucleation was above the equilibrium freezing temperature (0°C) in parts of the slurry volume. Thus, the key to creating scaold anisotropy is that the local cooling rates within the liquid slurry are suciently dierent to ensure that freezing equilibrium temperature is not reached thoughout the slurry volume at nucleation. This principal was valid over a range of collagen slurries, for the rst time demonstrating that by monitoring the temperature within slurry during freezing, scaold anisotropy with ice templated scaolds can be predicted.
Journal of The Royal Society Interface, 2014
In this paper, we show, for the first time, the key link between scaffold architecture and latent... more In this paper, we show, for the first time, the key link between scaffold architecture and latent heat evolution during the production of porous biomedical collagen structures using freeze-drying. Collagen scaffolds are used widely in the biomedical industry for the repair and reconstruction of skeletal tissues and organs. Freeze-drying of collagen slurries is a standard industrial process, and, until now, the literature has sought to characterize the influence of set processing parameters including the freezing protocol and weight percentage of collagen. However, we are able to demonstrate, by monitoring the local thermal events within the slurry during solidification, that nucleation, growth and annealing processes can be controlled, and therefore we are able to control the resulting scaffold architecture. Based on our correlation of thermal profile measurements with scaffold architecture, we hypothesize that there is a link between the fundamental freezing of ice and the structur...
Journal of Physics: Condensed Matter, Feb 20, 2006
The electronic structure of the Heusler alloy Co 2 TiSn is investigated here, with particular att... more The electronic structure of the Heusler alloy Co 2 TiSn is investigated here, with particular attention paid to its potential as a half-metallic ferromagnet. Ab initio calculations are performed using a plane wave pseudopotential code in the framework of density functional theory. These accurate calculations are done with convergence tolerances of 10 −5 and 10 −4 eV on the total energy and Fermi energy, respectively. The alloy is found not to be a half-metal. Minority spin electrons undergo distinctly hole-like dispersion at the point in k space while the majority spin bands are metallic with a multiply connected tube-like Fermi surface. Further, the computed minority band gap and spin polarization at the Fermi level are larger when the calculation is performed using the generalized gradient approximation.
Applied Physics Letters, Jun 20, 2005
Bulletin of the American Physical Society, Mar 18, 2021
Social Science Research Network, 2022
The architectural and physiomechanical properties of regenerative scaffolds have been shown to im... more The architectural and physiomechanical properties of regenerative scaffolds have been shown to improve engineered tissue function at both a cellular and tissue level. The fabrication of regenerative three-dimensional scaffolds that precisely replicate the complex hierarchical structure of native tissue, however, remains a challenge. The aim of this work is therefore twofold: i) demonstrate an innovative multidirectional freeze-casting system to afford precise architectural control of ice-templated collagen scaffolds; and ii) present a predictive simulation as an experimental design tool for bespoke scaffold architecture. We used embedded heat sources within the freeze-casting mold to manipulate the local thermal environment during solidification of icetemplated collagen scaffolds. The resultant scaffolds comprised complex and spatially varied lamellar orientations that correlated with the imposed thermal environment and could be readily controlled by varying the geometry and power of the heat sources. The complex macroarchitecture did not interrupt the hierarchical features characteristic of ice-templated scaffolds, but pore orientation had a significant impact on the stiffness of resultant structures under compression. Furthermore, our finite element model (FEM) accurately predicted the thermal environment and illustrated the freezing front topography within the mold during solidification. The lamellar orientation of freeze-cast scaffolds was also predicted using thermal gradient vector direction immediately prior to phase change. In combination our FEM and bespoke freeze-casting system present an exciting opportunity for tailored architectural design of ice-templated regenerative scaffolds that mimic the complex hierarchical environment of the native extracellular matrix.
Frontiers in Bioengineering and Biotechnology, 2016
Frontiers in Bioengineering and Biotechnology, 2016
Physica B: Condensed Matter, 2000
Muon-spin rotation (μSR) measurements have been used to study the superconducting vortex properti... more Muon-spin rotation (μSR) measurements have been used to study the superconducting vortex properties of the organic superconductors κ-(BEDT-TTF)2Cu(SCN)2, α-(BEDT-TTF)2NH4Hg(SCN)4 and β-(BEDT-TTF)2IBr2. These materials all have highly anisotropic structures consisting of metallic layers of BEDT-TTF molecules alternating with less well conducting anion layers. Varying the anion gives rise to a change in the anisotropy of the superconductivity and also to changes in the superconducting transition temperature. We have used both transverse and longitudinal magnetic fields to study the three-dimensional flux line lattice that is present at low temperatures and fields and to study also the loss of flux lattice order that occurs on increasing the temperature and field.
Series in Material Science and Engineering, 2006
Journal of Materials Science: Materials in Medicine, 2015
The structure of ice-templated collagen scaffolds is sensitive to many factors. By adding 0.5 wt%... more The structure of ice-templated collagen scaffolds is sensitive to many factors. By adding 0.5 wt% of sodium chloride or sucrose to collagen slurries, scaffold structure could be tuned through changes in ice growth kinetics and interactions of the solute and collagen. With ionic solutes (sodium chloride) the entanglements of the collagen molecule decreased, leading to fibrous scaffolds with increased pore size and decreased attachment of chondrocytes. With non-ionic solutes (sucrose) ice growth was slowed, leading to significantly reduced pore size and up-regulated cell attachment. This highlights the large changes in structure and biological function stimulated by solutes in ice-templating systems. Graphical Abstract
Journal of Physics: Condensed Matter, 2001
... Page 7. 2268 Th Jestädt et al temperature dependent but begins to rise rapidly as TC is appro... more ... Page 7. 2268 Th Jestädt et al temperature dependent but begins to rise rapidly as TC is approached. It is possible to relate the relaxation rate to the fluctuation rate of the electronic moments using λ = 2 2τ [17] which is valid in a regime where τ−1 ≫ and where a single time ...
Applied Physics Letters, 2006
We have investigated the 300 K inherent magnetoresistance of undoped InSb epilayers grown on GaAs... more We have investigated the 300 K inherent magnetoresistance of undoped InSb epilayers grown on GaAs(001) by molecular-beam epitaxy. The magnetoresistance of these films can be described well using a simplified model that incorporates gradation of properties away from the InSb/GaAs interface and the interplay between conduction and impurity bands. Although there is no significant intrinsic contribution in InSb bulk crystalline (001) materials due to its isotropic Fermi surface and mobility tensor, the linear and quadratic terms in the magnetoresistance as well as the overall magnitude can be tuned by varying the film thickness from 100 to 2000 nm.
In recent years, there has been a shift from traditional cell culture on two-dimensional substrat... more In recent years, there has been a shift from traditional cell culture on two-dimensional substrates towards the use of three-dimensional scaffolds for tissue engineering. Ice-templating is a versatile tool to create porous scaffolds from collagen. Here we discuss specific considerations for the design of moulds to produce freeze dried collagen scaffolds with pore sizes of around 100µm, a range that is relevant to tissue engineering. A numerical model of heat conduction, implemented in COMSOL Multiphysics ® version 5.0, calculated the temperature contour lines and heat flow vectors during cooling for a variety of mould geometries and materials. We show how temperature distribution within moulds determines the resulting pore structure of the scaffolds by regulating ice growth, and we validate our simulation against experimental results. These simulations are especially useful when working with moulds that contain volumes of more than 1cm in each direction. Key words
The following data files are provided: Python file containing the raw data for wavelengths and ve... more The following data files are provided: Python file containing the raw data for wavelengths and velocities measured at each pressure and Zip file containing all ESEM images taken at each pressure used for publication.
The Heusler alloy Co2TiSn is a ferromagnet with a Curie temperature of 355K. Our theoretical pred... more The Heusler alloy Co2TiSn is a ferromagnet with a Curie temperature of 355K. Our theoretical predictions by CASTEP as well as calculations done by others ootnotetextA. Yamasaki et al., Phys. Rev. B 65, 104410 (2002). show a high spin polarisation in the conduction band making it a promising candidate for a metallic spin injector. We study its magnetotransport properties as
Physica B: Condensed Matter, 2000
... Jestädt a , FL Pratt a , b , IM Marshall a , BW Lovett a , M. Kurmoo c , T. Sugano d and W. H... more ... Jestädt a , FL Pratt a , b , IM Marshall a , BW Lovett a , M. Kurmoo c , T. Sugano d and W. Hayes a. ... In a purely organic metamagnet, tanol suberate, we have observed a spin precession signal with a temperature dependence which has provided evidence of the two-dimensional ...
Physica B: Condensed Matter, 2000
μSR has been used to study a variety of polymers with very different electronic properties. In co... more μSR has been used to study a variety of polymers with very different electronic properties. In conducting polymers, the muon-generated radical states take the form of highly mobile polarons. Muon spin relaxation has been used to study the mobility of these polarons and to measure the temperature dependence of their intra-chain and inter-chain diffusion rates. It is found that the transport properties are strongly influenced by the librational ring modes of the phenylene rings in these polymers. In contrast, the muon-generated radical states in non-conducting polymers such as polybutadiene remain localised near the site of the muon. High field muon spin rotation, avoided level crossing resonance and longitudinal relaxation studies have been made, using the muon radical state as a probe of the dynamical properties of the polymer. Dramatic changes in the μSR signals are seen on going through the glass–rubber transition, as various dynamical degrees of freedom become frozen out. Additional information about the stability of the muon radical states on the microsecond timescale has also been obtained using RF muon spin rotation techniques. Using time-delayed RF resonance of the diamagnetic state at the RIKEN-RAL muon facility, the transition rate between paramagnetic and diamagnetic states could be studied as a function of temperature.
Materials Science and Engineering: C, 2014
Biopolymer scaolds have great therapeutic potential in the eld of tissue engineering due to the l... more Biopolymer scaolds have great therapeutic potential in the eld of tissue engineering due to the large interconnected porosity and natural biocompatibility of the polymers. Using an ice templated technique, where collagen is concentrated into a porous network by ice nucleation and growth, scaolds with anisotropic pore architecture can be created, mimicking natural tissue environments such as tendon or cardiac muscle. This paper describes a systematic set of experiments which have been undertaken to understand the eects of local temperature control on the anisotropy and architecture of ice templated biopolymer scaolds. The scaolds within this study were at least 10 mm in all dimensions, making them applicable to critical sized defects for biomedical applications. It was found that monitoring the temperature within slurry at specic locations during freezing was critical to predicting anisotropy of scaold architecture. Aligned porosity was produced only when the temperature at nucleation was above the equilibrium freezing temperature (0°C) in parts of the slurry volume. Thus, the key to creating scaold anisotropy is that the local cooling rates within the liquid slurry are suciently dierent to ensure that freezing equilibrium temperature is not reached thoughout the slurry volume at nucleation. This principal was valid over a range of collagen slurries, for the rst time demonstrating that by monitoring the temperature within slurry during freezing, scaold anisotropy with ice templated scaolds can be predicted.
Journal of The Royal Society Interface, 2014
In this paper, we show, for the first time, the key link between scaffold architecture and latent... more In this paper, we show, for the first time, the key link between scaffold architecture and latent heat evolution during the production of porous biomedical collagen structures using freeze-drying. Collagen scaffolds are used widely in the biomedical industry for the repair and reconstruction of skeletal tissues and organs. Freeze-drying of collagen slurries is a standard industrial process, and, until now, the literature has sought to characterize the influence of set processing parameters including the freezing protocol and weight percentage of collagen. However, we are able to demonstrate, by monitoring the local thermal events within the slurry during solidification, that nucleation, growth and annealing processes can be controlled, and therefore we are able to control the resulting scaffold architecture. Based on our correlation of thermal profile measurements with scaffold architecture, we hypothesize that there is a link between the fundamental freezing of ice and the structur...