Michael J. Powell

Band alignment of rutile and anatase TiO2

The most widely used oxide for photocatalytic applications owing to its low cost and high activity is TiO₂. The discovery of the photolysis of water on the surface of TiO₂ in 1972 launched four decades of intensive research into the underlying chemical and physical processes involved. Despite much collected evidence, a thoroughly convincing explanation of why mixed-phase samples of anatase and rutile outperform the individual polymorphs has remained elusive. One long-standing controversy is the energetic alignment of the band edges of the rutile and anatase polymorphs of TiO₂ (ref. ). We demonstrate, through a combination of state-of-the-art materials simulation techniques and X-ray photoemission experiments, that a type-II, staggered, band alignment of ~ 0.4 eV exists between anatase and rutile with anatase possessing the higher electron affinity, or work function. Our results help to explain the robust separation of photoexcited charge carriers between the two phases and highlight a route to improved photocatalysts.

Supratentorial and infratentorial intraparenchymal hemorrhage secondary to intracranial CSF hypotension following spinal surgery.

Study Design. A single case study was conducted. Objectives. To detail the occurrence of multiple intracranial, intraparenchymal hemorrhages following an iatrogenic acute reduction in cerebral spinal fluid pressure following excision of an intradural extramedullary spinal tumor. Summary of Background Data. Multiple supratentorial, intraparenchymal, intracranial hemorrhages following an acute reduction in cerebral spinal fluid pressure have not been previously reported in the literature. Methods. A case report and literature review are presented. Results. The patient made an uneventful full recovery. Conclusion. Intracranial hemorrhage must be considered in the differential diagnosis of patients presenting with persistent headache following spinal surgery when the dura has been breached and is associated with significant cerebrospinal fluid loss.

Reduced expression of the growth hormone and type 1 insulin‐like growth factor receptors in human somatotroph tumours and an analysis of possible mutations of the growth hormone receptor

objective Clinical acromegaly is characterized by elevated GH secretion in the presence of high circulating IGF‐I levels. We hypothesized that the physiological IGF‐I/GH negative feedback loop may be reset in somatotroph adenomas, specifically in terms of the level of expression of these receptors or mutations of the GH receptor (GH‐R) in such tumours.

The Expression of the F-Box Protein Skp2 is Negatively Associated with p27 Expression in Human Pituitary Tumors

The CDK inhibitor p27 plays a pivotal role in controlling cell proliferation during development, and has been implicated in tumorigenesis. Previous studies have demonstrated changes in p27 protein expression, but not in mRNA levels, in human pituitary tumors. It seems probable that the fall in p27 is due to increased degradation through the ubiquitin-proteasome pathway. Skp2 (S-phase kinase-interacting protein) is a specific F-box protein that allows the recognition and binding of phosphorylated p27 to the ubiquitin complex. The aim of our study was thus to investigate the possible role of Skp2 in pituitary tumorigenesis.A total of 59 human pituitary samples, 7 normal and 52 adenomas, were assessed for transcriptional expression of Skp2; 51 pituitary samples were assessed for protein expression. Real-time RT-PCR was performed on cDNA of reverse-transcribed mRNA for relative quantification of the Skp2 transcript. Immunostaining was performed using mouse monoclonal anti-Skp2 antibody.Skp2 mRNA and protein was detectable in every sample studied. Our results showed no significant difference between the pituitary tumors and normal pituitary tissue in Skp2 mRNA or nuclear protein expression. Individual tumor types had similar mRNA expression and variable protein expression. However, samples with high p27 protein expression showed significantly less Skp2 expression than samples with low p27 staining.Our data suggest that increased p27 degradation through the ubiquitin-proteasome pathway could be regulated in pituitary tumors by changes in Skp2 expression, although other factors probably also play a role.

Optimized Atmospheric-Pressure Chemical Vapor Deposition Thermochromic VO2 Thin Films for Intelligent Window Applications

Monoclinic vanadium(IV) oxide (VO2) has been widely studied for energy-efficient glazing applications because of its thermochromic properties, displaying a large change in transmission of near-IR wavelengths between the hot and cold states. The optimization of the reaction between VCl4 and ethyl acetate via atmospheric-pressure chemical vapor deposition (APCVD) was shown to produce thin films of monoclinic VO2 with excellent thermochromic properties (ΔTsol = 12%). The tailoring of the thermochromic and visible light transmission was shown to be possible by altering the density and morphology of the deposited films. The films were characterized by X-ray diffraction, atomic-force microscopy, scanning electron microscopy, ellipsometry, and UV–vis spectrometry. This article provides useful design rules for the synthesis of high-quality VO2 thin films by APCVD.

Aerosols: A Sustainable Route to Functional Materials

Sustainability is an increasingly important topic in the design and manufacture of materials, with the need to reduce the environmental impact of producing materials being of paramount significance. A competing interest to this is the ability to produce functional materials in large volumes from a fast, on-line process, which can be integrated easily into existing industrial setups. Herein, we present aerosol-assisted chemical vapour deposition (AACVD) routes to advanced functional materials. We will show that by careful design of precursors and manipulation of deposition conditions, it is possible to achieve high sustainability whilst maintaining fast growth rates and large scale production of thin film functional materials.

Characterization of SNARE Proteins in Human Pituitary Adenomas: Targeted Secretion Inhibitors as a New Strategy for the Treatment of Acromegaly?

CONTEXT Targeted secretion inhibitors (TSIs), a new class of recombinant biotherapeutic proteins engineered from botulinum toxin, represent a novel approach for treating diseases with excess secretion. They inhibit hormone secretion from targeted cell types through cleavage of SNARE (soluble N-ethylmaleimide-sensitive factor-activating protein receptor) proteins. qGHRH-LH(N)/D is a TSI targeting pituitary somatotroph through binding to the GHRH-receptor and cleavage of the vesicle-associated membrane protein (VAMP) family of SNARE proteins. OBJECTIVE Our objective was to study SNARE protein expression in pituitary adenomas and to inhibit GH secretion from somatotropinomas using qGHRH-LH(N)/D. DESIGN We analyzed human pituitary adenoma analysis for SNARE expression and response to qGHRH-LH(N)/D treatment. SETTING The study was conducted in University Hospitals. PATIENTS We used pituitary adenoma samples from 25 acromegaly and 47 nonfunctioning pituitary adenoma patients. OUTCOME Vesicle-SNARE (VAMP1-3), target-SNARE (syntaxin1, SNAP-23, and SNAP-25), and GHRH-receptor detection with RT-qPCR, immunocytochemistry, and immunoblotting. Assessment of TSI catalytic activity on VAMPs and release of GH from adenoma cells. RESULTS SNARE proteins were variably expressed in pituitary samples. In vitro evidence using recombinant GFP-VAMP2&3 or pituitary adenoma lysates suggested sufficient catalytic activity of qGHRH-LH(N)/D to degrade VAMPs, but was unable to inhibit GH secretion in somatotropinoma cell cultures. CONCLUSIONS SNARE proteins are present in human pituitary somatotroph adenomas that can be targeted by TSIs to inhibit GH secretion. qGHRH-LH(N)/D was unable to inhibit GH secretion from human somatotroph adenoma cells. Further studies are required to understand how the SNARE proteins drive GH secretion in human somatotrophs to allow the development of novel TSIs with a potential therapeutic benefit.

Aluminium/gallium, indium/gallium, and aluminium/indium co-doped ZnO thin films deposited via aerosol assisted CVD

Aluminium/gallium co-doped ZnO (AGZO), indium/gallium co-doped ZnO (IGZO), and aluminium/indium co-doped ZnO (AIZO) thin films were synthesised on glass substrates via aerosol assisted chemical vapour deposition (AACVD). The films were fully characterised by X-ray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy. The optoelectronic properties of the films were determined using UV/vis spectroscopy and Hall effect measurements. The AGZO film displayed the lowest resistivity (1.3 × 10−2 Ω cm) and highest carrier mobility (7.9 cm2 V−1 s−1), due the relatively low amount of disorder in the structure. The incorporation of In3+ resulted in the most disorder in the structure due to its large radius, which led to an increase in optical absorption, and a decrease in resistivity.

Magnetic hyperthermia controlled drug release in the GI tract: solving the problem of detection

Drug delivery to the gastrointestinal (GI) tract is highly challenging due to the harsh environments any drug- delivery vehicle must experience before it releases it’s drug payload. Effective targeted drug delivery systems often rely on external stimuli to effect release, therefore knowing the exact location of the capsule and when to apply an external stimulus is paramount. We present a drug delivery system for the GI tract based on coating standard gelatin drug capsules with a model eicosane- superparamagnetic iron oxide nanoparticle composite coating, which is activated using magnetic hyperthermia as an on-demand release mechanism to heat and melt the coating. We also show that the capsules can be readily detected via rapid X-ray computed tomography (CT) and magnetic resonance imaging (MRI), vital for progressing such a system towards clinical applications. This also offers the opportunity to image the dispersion of the drug payload post release. These imaging techniques also influenced capsule content and design and the delivered dosage form. The ability to easily change design demonstrates the versatility of this system, a vital advantage for modern, patient-specific medicine.

Particle size, morphology and phase transitions in hydrothermally produced VO2(D)

Different morphologies and sizes of VO2(D) particles were synthesised via hydrothermal synthesis using ammonium metavanadate (NH4VO3) or vanadium pentoxide (V2O5) as a vanadium precursor. By adjusting the concentration of vanadium precursors and the pH of the starting solution, a variety of morphologies and sizes of VO2(D) particles from 20 nm to 3 μm could be produced. A flower-shape morphology was obtained under strongly acidic conditions, passing through star-shape particles of 1 μm at pH 2.5 and finally obtaining homogeneous round balls of around 3 μm at pH 6.9. Nanoparticles were produced hydrothermally using V2O5 as a precursor and hydrazine as a reducing agent. The transition from VO2(D) to thermochromic VO2(R) in micron scale particles occurred at 350 °C under vacuum. However, the nanoparticles of VO2(D) had a significantly lower VO2(D) to thermochromic VO2(R) transition temperature of 165 °C after annealing for only a few minutes. This is, to our knowledge, the lowest annealing temperature and time reported in the literature in order to obtain a thermochromic VO2 material via another VO2 phase. After the conversion of VO2(D) microparticles to thermochromic VO2(R), the metal to insulator transition temperature is 61 ± 1 °C for the heating cycle and 53 ± 1 °C for the cooling cycle. However, VO2(R) nanoparticles showed a significantly reduced metal insulator transition temperature of 59 ± 1 °C and 42 ± 1 °C for the cooling cycle lower than that reported in the literature for bulk VO2. This is important due to the need for having a compound with a switching temperature closer to room temperature to be used in smart window devices for energy consumption. W-VO2(D) star shape microparticle samples were prepared using 2–7 at% of the dopant (using ammonium metavanadate as a precursor), although unexpectedly this does not seem to be a viable route to a reduced metal to insulator transition in this system.