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Stephen Mann

Publications and source records attributed to Stephen Mann.

At least 19 recordsLinked to original sources
PubMed2006

Theoretical near-field optical properties of branched plasmonic nanoparticle networks.

Extended branched networks of single-nanoparticle chains have recently been self-assembled from colloidal suspensions. In particular, gold nanoparticle linear chains and complex chain networks have revealed unique signatures of plasmon modes in their extinction spectra. In this Letter, we investigate theoretically their near-field optical properties and show that a real space mapping of these modes can be achieved with a photon scanning tunneling microscope setup. A distinct subwavelength patterning of the optical near-field gives rise to well-resolved photon scanning tunneling microscope images that can be used to identify the network segments able to efficiently carry optical energy.

Journal Article↗
PubMed2006

Synthesis and characterization of cerium phosphate nanowires in microemulsion reaction media.

Synthesis of CePO4 in water-in-oil microemulsions produces crystalline nanowires with uniform thickness (mean width = 3.7 nm) and straight or branched morphologies. The nanowires develop within a period of 1 month by surfactant-mediated slow crystallization from amorphous primary filaments with highly convoluted morphology. Electron microscopy and dynamic light scattering studies suggest that CePO4 crystallization occurs within the confined reaction spaces of preformed Ce(III)-containing rod-shaped micelles, rather than by mesophase aggregation and transformation of primary surfactant-coated nanoparticles.

Cerium↗
PubMed2006

One-step synthesis and solvent-induced exfoliation of hybrid organic-inorganic phyllosilicate-like materials.

A room-temperature sol-gel-based process was used to produce by direct synthesis talc-like organosilicates having hexadecyl or aminopropyl groups pending in the interlayer space. Thermal analyses, Fourier transform infrared and 13C/29Si solid-state nuclear magnetic resonance spectroscopies confirmed the presence of organic moieties bonded to the inorganic network. Exfoliation of these organoclays in polar solvents such as water for the positively charged magnesium phyllo(aminopropyl)silicate, and in low polar solvents such as toluene and chloroform for hydrophobic magnesium phyllo(hexadecyl)silicate, was investigated by TEM. The ability of these layered magnesium organosilicates to exfoliate in appropriate solvents was exploited for the preparation of transparent self-supporting films and ordered macroporous networks using by latex colloidal crystal templates.

Inorganic Chemicals↗
PubMed2005

Fabrication of hydroxyapatite sponges by dextran sulphate/amino acid templating.

We report a new template-directed method for the fabrication of hydroxyapatite (HAp) sponges by using amino-acid-coated HAp nanoparticles dispersed within a viscous polysaccharide (dextran sulfate) matrix, and describe the use of these materials for the viability and proliferation of human bone marrow stromal cells. The nanoparticles were prepared in the presence of excess amounts of aspartic acid, alanine or arginine, and subsequently organised into macroporous frameworks with typical pore sizes of 100-200 microm during thermal degradation of the dextran matrix. The sponge macrostructure was influenced by changes in the heating rate and sintering time, as well as the use of different amino acids or variations in dextran functional groups. Biocompatibility testing showed retention of cell viability, production of extracellular matrix and alkaline phosphatase expression, suggesting that it should be possible to exploit this novel fabrication method for potential applications in cartilage or soft tissue engineering.

Alanine↗
PubMed2005

Fabrication of hybrid nanocapsules by calcium phosphate mineralization of shell cross-linked polymer micelles and nanocages.

Self-assembled shell cross-linked poly(acrylic acid-b-isoprene) (PAA78-b-PI97) micelles or cross-linked PAA nanocages in aqueous solution were used as templates for the preparation of novel polymer-inorganic nanocapsules. The hybrid nanostructures were typically 50-70 nm in diameter and consisted of spherical polymer nanoparticles or nanocages enclosed within a continuous 10-20 nm thick surface layer of amorphous calcium phosphate. Nucleation of calcium phosphate specifically in association with the polymer nanoparticles was facilitated by low supersaturation levels and by sequestration of Ca2+ ions within the carboxylate-rich PAA domains prior to addition of HPO4(2-). Modifications in ionic concentrations were used to control the calcium phosphate surface layer thickness and prepare mineralized cross-linked PAA-b-PI micelles with variable shell permeability. The permeability of beta-carotene into the hydrophobic PI core of mineralized shell cross-linked PAA-b-PI micelles was reduced by approximately 50 or 100% respectively for hybrid nanostructures enclosed within 10 or 20 nm thick calcium phosphate layers. Our results suggest that calcium phosphate-polymer cross-linked nanocapsules could have potential applications as pH-responsive biocompatible hybrid nanostructures for use in applications such as drug delivery, bioimaging, and therapeutics.

Biocompatible Materials↗
PubMed2005

Dysplastic naevi: to shave, or not to shave? A retrospective study of the use of the shave biopsy technique in the initial management of dysplastic naevi.

The management of dysplastic naevi is a controversial subject. This study sought to assess the usefulness of the shave biopsy technique in the initial management of dysplastic naevi, and to demonstrate the advantages over the punch biopsy technique. We report a retrospective observational study of histopathology specimens examined in one histopathology practice over a 14-month period. Patients who had a clinical diagnosis of 'dysplastic naevus', which had initially been biopsied using either a shave or punch biopsy, and then followed up with a full-thickness elliptical excision, were included in the study. Histopathological concordance between the shave and punch biopsy specimens and their respective follow-up elliptical excisions was compared. We found that 21 of 22 (95.5%) shave biopsies were concordant with their respective excision specimens, and that 29 of 41 (70.7%) punch biopsies were concordant with their respective elliptical excision specimens. Of the shave biopsy specimens reviewed, 66% showed that the dysplastic naevi were completely excised with the initial biopsy, compared with 21.2% of the punch biopsy specimens. These findings confirm that shave biopsies provide accurate diagnostic information in the assessment of dysplastic naevi. Shave biopsies enable the entire lesion to be submitted for histopathological assessment, improving the chances of an accurate diagnosis.

Adult↗
PubMed2005

Acral pseudolymphomatous angiokeratoma of children (APACHE).

13-year-old girl presented with a 10-year history of multiple discrete red firm papules situated on her right upper arm. The histopathology examination revealed a massive subepidermal lymphohistiocytic infiltrate, consistent with acral pseudolymphomatous angiokeratoma of children. Treatment with topical application of mometasone furoate 0.1% cream once daily for 6 months improved the lesions partially. However, these papules returned to their pretreatment appearance and consistency within 6 months after the cessation of the topical corticosteroid. The authors prefer the term 'papular angiolymphoid hyperplasia' for this entity, based on the absence of histological angiokeratomatous features, the benign nature of the lesion and the previously reported cases from adults and non-acral sites.

Administration, Topical↗
PubMed2005

Orbital leiomyoma: a case report with clinical, radiological and pathological correlation.

Orbital leiomyoma is a benign tumour of smooth muscle origin that can be clinically, radiologically and histopathologically difficult to diagnose due to the rarity of leiomyomas in this location. A 74-year-old woman presented with a 2-month history of painless proptosis. Computed tomography and magnetic resonance imaging studies revealed a well-circumscribed intraconal lesion separate from the optic nerve, and not eroding adjacent bone. A right lateral orbitotomy via a lid crease incision was performed to remove the firm lobulated lesion. Postoperatively there was an obvious decrease in proptosis. Microscopically the lesion was a well-circumscribed tumour composed of spindle cells. There were no light microscopic features to suggest malignancy, and immunohistochemistry was used to confirm the diagnosis of leiomyoma. Leiomyoma is a tumour that is rarely found in the orbit most likely due to the paucity of smooth muscle in this location. The differential diagnosis is wide, and the role of radiology, histology and immunohistochemistry in the diagnosis of leiomyoma is discussed. Surgical excision in this case excluded malignancy, provided a definitive diagnosis of a rare entity and resulted in marked clinical improvement.

Actins↗
PubMed2003

Morphosynthesis of complex inorganic forms using pollen grain templates.

Porous micron-sized particles of silica, calcium carbonate or calcium phosphate are prepared with complex morphologies by template-directed synthesis employing intact pollen grains; the materials adsorb and release drug molecules and can be functionalized with metallic or magnetic nanoparticles.

Calcium Carbonate↗