Measurement of the Structural Unit in magnetic dispersions

Measurement of the Structural Unit (SU - containing both the solid phase and trapped­fluid within their associated structures) in magnetic dispersions has been carried out using Hindered Settling (HS) analysis that uses scanning column magnetometry and cone & plate rheology techniques. From this, an equivalent Stokes' particle diameter, d, of (5.2 ≤ d ≤ 8.2) microns was determined that is approximately 22 times larger than the iron oxide particles of our formulation. A previous computer simulation based on HS theory produces complete concentration­height profiles of the sedimenting system over time that compare well when using a correspondingly large trapped­liquid fraction of around the 84% of the SU volume determined here, giving confidence in the result. As interest in iron oxide suspensions for potential biomedical and chemical decontamination/catalysis applications continues to grow an understanding of their structures is likely to become increasingly important

The Observed Linearity and Detection Response of Magnetic Fluid Concentration Magnetometry - A Theoretical and Experimental Description

The response of a Scanning Column Magnetometer (SCM) used to measure concentration profiles of columns of magnetic dispersions has been investigated experimentally and theoretically. From the observed linearity of the total SCM output signal as a function of magnetic particle concentration, a consistent theoretical description is developed that assumes a small sensing coil field and no on-going particle agglomeration. Further theoretical development resulted in a detection coil response function that compared well with the measured response of a delta function approximation in the form of a thin ferrite disk and means that the SCM response function and spatial resolution may be determined from the coil design alone

Effects of structure on noise in very thin particulate data storage media

The effects of structure on noise in very thin particulate data storage tapes have been investigated using DC and tone-noise methods. The results from a set of five commercial development tapes indicate that large structural correlations of size ~ 5 μm become increasingly apparent as the magnetic layer of the tapes becomes thinner over the range 140 – 50 nm. As the samples were fabricated from identical particles (MP4 – length ~ 60nm) using the same double coating process, and with the tone-noise results showing comparable top surface roughness, these findings are consistent with large in-plane structures at the magnetic/non-magnetic interface that may be expected from mixing effects during production drying. Since this interface moves ever closer to the head with increasing data density, its effects on media noise will become increasingly important

Gender Needs Assessment for Blantyre City, Malawi

The main objectives of this needs assessment are to outline the major obstacles to gender equality and women's empowerment in Blantyre City, and to present interventions with the potential to address to these issues. The costs associated with these interventions are also presented

Development of a Method to Identify in-Plane Anisotropy Axes in Soft Magnetic Materials Using a Standard Vibrating Sample Magnetometer

A method of identifying in-plane anisotropy axes in soft magnetic materials has been developed using an in-field-only measurement technique. The method is based on an extended bi-axial vibrating sample magnetometer (VSM) technique that simulates the torque on a sample; giving rise to equivalent torque curves that are comparable with those determined directly using a torque magnetometer. Testing of the new methodology was carried out on magnetically soft and multi-axial nickel ferrite textured films deposited with various crystal orientations. The results compare well with the accepted bi-axial VSM technique, identifying the same in-plane anisotropy directions and relative easy and hard axes from the in-field measurement alone. This means that these characteristics could be determined using a standard VSM measuring magnetization in the field direction as long as it is fitted with a rotating sample stage

The fabrication and characterization of stable core-shell superparamagnetic nanocomposites for potential application in drug delivery

Two systems of core-shell superparamagnetic nanoparticles in the size range 45 to 80 nm have been fabricated by the coating of bare magnetite particles with either mesoporous silica or liposomes and the loading/release of the anti-cancer drug Mitomycin C (MMC) from their surfaces has been investigated. The magnetic cores of size ~ 10 nm were produced by a co-precipitation method in aqueous solution, with the silica coating containing an unstructured network of pores of size around 6 nm carried out using a surfactant-templating approach and the liposome coating achieved by an evaporation-immersion technique of the particles in a lipid solution. Stability measurements using a scanning column magnetometry technique indicated that the lipid-coating of the particles halts the sedimentation otherwise apparent in < 1 hour for the bare magnetite to produce an ultra-stable system and thereby overcome one of the main barriers to potential in-vivo applications. Whilst an increase in stability was also observed in the silica-coated system, it was still unstable over a few hours and will require further investigation. Magnetization curves of the coated systems were indicative of superparamagnetic behavior whilst the in vitro loading and release of MMC resulted in two distinctly different outcomes for the two systems: (i) the silica-coated particles saturated in < 4 hours to a loading of around 7 µg/mg of material, releasing about 6 % at a near constant rate over 48 hours whilst (ii) the lipid-coated particles saturated to around only 4 µg/mg over the same time period but with a subsequent rapid release rate over the first 3 hours to 27 % then rising near-linearly to a value of about 45 % at the 48 hour mark. This gives scope for systems’ to be tuned to the appropriate rate and load delivery as required by clinical need with further investigations underway

Role of an additional interfacial spin-transfer torque for current-driven skyrmion dynamics in chiral magnetic layers

Skyrmions can be driven by spin-orbit torques as a result of the spin Hall effect. Here we model an additional contribution in ultra-thin multilayers, arising from the spin accumulation at heavy metal / ferromagnetic interfaces and observe the effects on a large range of skyrmion diameters. The combination of the interfacial spin-transfer torque and the spin-orbit torque results in skyrmion motion which helps to explain the observation of small skyrmion Hall angles for skyrmion diameters less than 100 nm. We show that this additional term has a significant effect on the skyrmion dynamics and leads to rapidly decreasing skyrmion Hall angles for small skyrmion diameters, as well as a skyrmion Hall angle versus skyrmion velocity dependence nearly independent of the surface roughness characteristics. Also, the effect of various disordered energy landscapes, in the form of surface roughness, on the skyrmion Hall angle and velocity is shown to be largely drive-dependent. Our results show good agreement with those found in experiments thus concluding that the interfacial spin-transfer torque should be included in micromagnetics simulations for the reproduction of experimental results

Production of perovskite-like La(1-x)Ca(x)MnO(3+delta) ferromagnetic thin films by electrochemical reduction

Ferromagnetic and perovskite-like thin films (< 1 micron) of La(1-x)Ca(x)MnO(3+delta) have been routinely prepared by heat treatment of an amorphous La Ca Mn precursor. The precursor was electrodeposited cathodically in the absence of oxygen and water onto polished silver substrates from a non-aqueous solution of the components’ nitrates. Analysis by X-Ray diffraction and SQUID magnetometry shows these materials exhibit the appropriate structural and magnetic phases indicative of Colossal Magnetoresistance

Hindered settling of particulate dispersions

A computer simulation has been developed that models hindered settling in particulate recording media dispersions. The resulting effective pigment concentration profiles compare well with experimental observations carried out using a scanning column magnetometry technique. Rigorous testing for mass conservation gives added confidence in the feasibility of this model as an aid in the study of suspension structure. As this structure is important in the media manufacturing processes of coating, orientation and drying, these investigations offer the potential to enhance the qualities of the final product

A case of pediatric stiff-person syndrome in Kenya

Background: Stiff-person syndrome (SPS) is a rare progressive autoimmune disease that is especially uncommon in the pediatric population. SPS is often undiagnosed for years. Case: Here we present a 12 year-old girl with a history of insulin dependent diabetes mellitus who presented with epigastric pain and whole body rigidity to a hospital in Eldoret, Kenya. A high-clinical suspicion led to targeted autoimmune testing and diagnosis in 15 days. The serum anti–glutamic acid decarboxylase (GAD) level was greater than 2000 (normal 0-10 IU/ml), strongly supporting the diagnosis of stiff-person syndrome plus. The patient recovered with diazepam, baclofen, and supportive care. Intravenous immunoglobulin was unavailable due to the patient’s economic constraints and challenges in accessing the health facility. Several weeks later she returned with recrudescence of her symptoms. Conclusion: We hope this case presentation will help illustrate the need to build care systems that can address the longitudinal care of patients with neurologic diseases in resource-limited settings. &nbsp; French title:Un cas pédiatrique de syndrome de la personne raide au Kenya Introduction: Le syndrome de la personne raide (SPR) est une maladie auto-immune progressive rare qui est particulièrement rare dans la population pédiatrique. Le SPR n'y est souvent pas diagnostiqué pendant des années. Observation: Nous présentons ici le cas d’une fille de 12 ans ayant des antécédents de diabète sucré insulino-dépendant qui s'est présentée avec des douleurs épigastriques et une rigidité corporelle totale dans un hôpital d'Eldoret, au Kenya. Une forte suspicion clinique a conduit à des tests auto-immuns ciblés et à un diagnostic en 15 jours. Le taux sérique d'acide anti-glutamique décarboxylase (GAD) était supérieur à 2000 (normal 0-10 UI/ml), ce qui étaye fortement le diagnostic du syndrome de la personne raide plus. Le patient s'est rétabli avec du diazépam, du baclofène et des soins de soutien. L’immunoglobuline intraveineuse n’était pas disponible en raison des contraintes économiques du patient et des difficultés d’accès au centre de santé. Plusieurs semaines plus tard, elle est revenue avec une recrudescence de ses symptômes. Conclusion Nous espérons que cette observation aidera à illustrer la nécessité de créer des systèmes de soins capables de prendre en charge les soins longitudinaux des patients atteints de maladies neurologiques dans des milieux à ressources limitées