Influence of vanillic acid immobilization in Nafion membranes on intramembrane diffusion and structural properties

Pulsed field gradient (PFG) NMR in combination with quasielastic neutron scattering (QENS) was used to investigate self-diffusion of water and acetone in Nafion membranes with and without immobilized vanillic acid (VA). Complementary characterization of these membranes was performed by small angle X-ray scattering (SAXS) and NMR relaxometry. This study was motivated by the recent data showing that an organic acid, such as VA, in Nafion can preserve its catalytic activity in the presence of water even at high intra-polymer water concentrations corresponding up to 100% ambient relative humidity. However, there is currently no clear understanding of how immobilized organic acid molecules influence the microscopic transport properties and related structural properties of Nafion. Microscopic diffusion data measured by PFG NMR and QENS are compared for Nafion with and without VA. For displacements smaller than the micrometer-sized domains previously reported for Nafion, the VA addition was not observed to lead to any significant changes in the water and/or acetone self-diffusivity measured by each technique inside Nafion. However, the reported PFG NMR data present evidence of a different influence of acetone concentration in the membranes with and without VA on the water permeance of the interfaces between neighboring micrometer-sized domains. The reported diffusion data are correlated with the results of SAXS structural characterization and NMR relaxation data for water and acetone.

Improved electrocatalytic ethanol oxidation activity in acidic and alkaline electrolytes using size-controlled Pt-Sn nanoparticles

The promotion of the electrocatalytic ethanol oxidation reaction (EOR) on extended single-crystal Pt surfaces and dispersed Pt nanoparticles by Sn under acidic conditions is well known. However, the correlation of Sn coverage on Pt nanoparticle electrocatalysts to their size has proven difficult. The reason is that previous investigations have typically relied on commercially difficult to reproduce electrochemical treatments of prepared macroscopic electrodes to adsorb Sn onto exposed Pt surfaces. We demonstrate here how independent control over both Sn coverage and particle size can yield a significant enhancement in EOR activity in an acidic electrolyte relative to previously reported electrocatalysts. Our novel approach uses electroless nanoparticle synthesis where surface-adsorbed Sn is intrinsic to Pt particle formation. Sn serves as both a reducing agent and stabilizing ligand, producing particles with a narrow particle size distribution in a size range where the mass-specific electrocatalytic activity can be maximized (ca. 1-4 nm) as a result of the formation of a fully developed Sn shell. The extent of fractional Sn surface coverage on carbon-supported Pt nanoparticles can be systematically varied through wet-chemical treatment subsequent to nanoparticle formation but prior to incorporation into macroscopic electrodes. EOR activity for Pt nanoparticles is found to be optimum at a fractional Sn surface coverage of ca. 0.6. Furthermore, the EOR activity is shown to increase with Pt particle size and correlate with the active area of available Pt (110) surface sites for the corresponding Sn-free nanoparticles. The maximum area- and mass-specific EOR activities for the most active catalyst investigated were 17.9 μA/cm(2)Pt and 12.5 A/gPt, respectively, after 1 h of use at 0.42 V versus RHE in an acidic electrolyte. Such activity is a substantial improvement over that of commercially available Pt, Pt-Sn, and Pt-Ru alloy catalysts under either acidic or alkaline conditions.

Enhanced electrocatalytic oxygen reduction through electrostatic assembly of Pt nanoparticles onto porous carbon supports from SnCl2-stabilized suspensions

Monodisperse Pt nanoparticles with atomic structures that span the cluster to crystal transition have recently been synthesized in electrostatically stabilized, aqueous-based suspensions. In the present study, the anionic charge from the stabilizing SnCl(2) sheath adsorbed on the surface of these particles is used for the first time to assemble Pt directly onto porous carbon supports via electrostatic assembly. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) reveals that these assemblies have substantially higher Pt-C dispersions than obtained from precipitation methods commonly used for commercial electrocatalyst systems. Energy dispersive spectroscopy (EDS) and inductively coupled plasma-mass spectrometry (ICP-MS) are used to determine that loadings of 10-30% by weight Pt (particle packing fractions from 0.05 to 0.25) are obtained through a single electrostatic application of these particles on Vulcan carbon, depending on particle size. The highest average oxygen reduction reaction (ORR) mass activity obtained using this approach is 90.4 A/g(Pt) at 0.9 V vs RHE in 0.1 M perchloric acid is with 1-2 nm particles that exhibit a transitional atomic structure. This activity compares to an average value of 74.0 A/g(Pt) obtained from densely packed electrostatic layer-by-layer (LbL) assemblies of unsupported particles and 36.7 A/g(Pt) commercial Vulcan electrocatalyst from Tanaka Kikinzoku Kogyo (TKK). Enhanced activity is observed with electrostatic assembly of any particle size on Vulcan relative to unsupported or commercial electrocatalyst with comparable durability. Such enhanced activity is attributed to improved reactant accessibility to the catalyst surface due to the increase in particle dispersion. An extinction coefficient of 7.41 m(2)/g at 352 nm is obtained across the entire cluster to crystal transition from 20 atom clusters to 2.9 nm single crystal nanoparticles, indicating that observed variation in ORR activity with particle size may be associated primarily with changes in atomic surface structure as opposed to the metallic character of the nanoparticles as assessed by UV-vis spectroscopy.

The Use of Aqueous Enzymatic Polymerization of Amphyphilic Alkyl Tyrosine Derivatives as Environmentally Benign Coatings in the Microelectronics Industry

The surface coating properties of enzymatically polymerized decyl esters of d-tyrosine from aqueous solutions onto gold surfaces have been investigated utilizing the complementary techniques of Potentiometeric Titration, UV-VIS Spectroscopy, and X-ray Photoelectron Spectroscopy (XPS). The aqueous-based coatings are of interest as environmentally friendly and cost-effective replacements for epoxy-based coatings currently employed in the microelectronics industry for both chemical protection and electrical insulation of gold-covered metallic conductors. Experimental results with respect to polymerization pH, immersion pH, and immersion time are presented and compared to the ionization behavior of the monomers in solution. Optimum processing conditions have been established, which yield uniform aqueous-based polymeric coatings on gold conductor surfaces.

Silica nanoparticle layer-by-layer assembly on gold

Layer-by-layer (LBL) assembly of silica nanoparticles is investigated as a means of controlling the surface wetting properties of gold electroplated onto 316 L stainless-steel substrates while maintaining a low electrical surface contact resistance. The strong polyelectrolyte acrylamide/beta-methacryl-oxyethyl-trimethyl-ammonium copolymer is used as the cationic binder. The impact of silica nanoparticle zeta (zeta) potential for a range of -37.1 to 5.9 mV in the thickness, wettability, and contact resistance of the final LBL-assembled coatings is presented. The zeta potential is varied by altering both the pH and alcohol (ethanol) content of the silica suspensions and polymer suspension, consistent with the predictions of the Debye-Huckel equation. Nanoparticle adsorption is found to occur rapidly, with surface coverage equilibration obtained after only 1 min and uptake that is nearly linear with respect to the number of bilayers deposited. An increase in the absolute value of the (negative) zeta potential in the silica suspension is found to increase the bilayer thickness to an average value as high as 82% of the individual nanoparticle diameter for the smaller nanoparticles investigated, suggesting that nearly complete surface coverage may be achieved after the application of only a single nanoparticle-polymer bilayer (a coating thickness as low as 15.6 nm) and that nanoparticle adsorption is enhanced by electrostatic attraction between substrate and adsorbate. Counterintuitively, a more porous bilayer structure is observed if the zeta potential of the previously deposited nanoparticles is increased while the substrate is immersed in the cationic copolymer suspension, suggesting that copolymer adsorption in inhibited by substrate-solvent interactions. Wetting measurements demonstrate that silica LBL assembly results in a substantial reduction in contact angle from 84 degrees on the bare substrate surface to as low as 15 degrees after the application of a single bilayer and 7 degrees after the application of eight bilayers. A monotonic increase in coating contact resistance is observed with an increase in the thickness with a characteristic volumetric electrical through-plane resistivity of as low as 1.63 kOmega.cm obtained from contact resistance measurement.

Epidermal nevus syndrome with development of a mandibular ameloblastoma

Epidermal nevus syndrome (ENS) is a hamartoneoplastic syndrome characterized by the association of epidermal nevi with abnormalities in other organ systems. We report a 32-year-old woman with ENS that, in addition to cutaneous manifestations, showed red plaques on the maxillary and mandibular labial alveolar mucosa and a papillomatous lesion of the midline posterior hard palate. Radiographic examination of the jaws was noncontributory. Approximately 5 years later, a follicular ameloblastoma developed in the mandible. The tumor showed duct-like cystic spaces, continuity with the overlying epithelium, and globular myxomatous areas in the connective tissue. The palatal lesion was diagnosed as papilloma, whereas the maxillary plaques showed nonspecific mucositis. The association of ameloblastoma with ENS is discussed. This is the second case of ENS associated with ameloblastoma reported in the medical literature.

Secondary orbital melanomas: analysis of 15 cases

Orbital melanomas comprise a heterogeneous group of pigmented tumours originating from melanocytes of the ophthalmic tissues, or represent distant metastases of cutaneous melanomas to the orbit. They can be classified into primary and secondary orbital melanomas. Whereas primary orbital melanomas are extremely rare, secondary orbital melanomas are seen more often and usually represent massive extrascleral extensions of uveal melanomas. Their diagnosis is difficult and controversy exists both about the treatment policy and regarding the prognosis. In an effort to clarify some of the aspects of the biological behaviour of these intriguing lesions, we retrospectively reviewed all orbital melanomas treated in our departments during the last eight years. The records of 15 patients with massive secondary orbital melanomas treated surgically were reviewed and analysed. Eleven of the patients were female and four were male. The mean age at the time of surgery was 68 years. Presenting features included unilateral orbital mass, often with painless proptosis, conjuctival bleeding, acute glaucoma crisis, decreased visual acuity and intermittent diplopia. The site of origin was the uveal tract in nine cases, the conjunctiva in three, the eyelids in two and the skin of the lower extremity in one patient. All patients were treated surgically with various types of orbital exenteration. Additional treatment included radiotherapy and chemotherapy. Two patients died from intracranial extension of the disease and 10 died from distant metastases. Three patients are alive with no evidence of disease. The longest survival was 33 months and the mean survival was 16.6 months. Early diagnosis and proper management of ocular melanoma prevents orbital extension and prolongs patient survival. Surgical treatment of secondary orbital melanoma with or without adjuvant radiotherapy and/or chemotherapy does not seem to improve patient survival when compared with conservative treatment used in other reports. However, orbital exenteration is effective for local control of the disease.

The use of the buccal fat pad for reconstruction of oral defects: review of the literature and report of 15 cases

PURPOSE

Although the buccal fat pad (BFP) was originally used as an alternative method for the closure of small to medium-sized oroantral and oronasal communications, its use has now been extended to use after excision of oral malignancies. This report describes experience with this technique.

PATIENTS AND METHODS

The BFP was used as a pedicled graft to reconstruct medium-sized surgical defects of the oral soft and hard tissues in 15 patients suffering from oral malignant tumors. Six of the defects were in the maxilla, 3 in the retromandibular area, and 6 in the cheek and oral commissure. The BFP was left uncovered to epithelialize in 14 patients, and in one it was covered with lyophilized dura.

RESULTS

The BFP healed without complications within 3 to 4 weeks in 13 patients, whereas in 2 patients with maxillary defects there was partial loss of the graft, requiring the additional use of an obturator in 1 case and a tongue flap in another to prevent oronasal leakage. Harvesting the graft proved to be extremely easy, and care was only necessary to avoid severing the supporting vascular plexus and the thin capsule covering the BFP.

CONCLUSIONS

The findings support the view that the BFP is a useful, easy, and uncomplicated alternative method for the reconstruction of small to medium-sized surgical defects of the oral hard and soft tissues.

The Effect of Polymer Substrate Surface Basicity on the Adsorption of a Cationic Polyacrylamide

The adsorption of a cationic polyacrylamide onto polytetrafluoroethylene, bisphenol-A based epoxy resins, and acrylate substrates was characterized with X-ray photoelectron spectroscopy (XPS) and dynamic contact angle measurement in water. Surface acidity-basicity was quantified via dynamic contact angle measurement in water, ethylene glycol, and diiodomethane. The epoxy resins exhibited intermediate surface basicity and adsorbed the most polyelectrolyte, suggesting that specific substrate-adsorbate acid-base interactions govern adsorption of the cationic polyacrylamide onto surfaces of low to intermediate basicity. In general polar interactions appear to dominate the adsorption process. Advancing contact angle measurements have yielded quantitative fractional surface coverage information for polymer-on-polymer adsorption comparable to that obtained via XPS. Copyright 1999 Academic Press.

Tumours of the head and neck in the elderly: analysis of 190 patients

Tumours of the head and neck represent approximately 5% of human neoplasms. More than 50% of the patients are above 65 years of age. During the years 1991-1996, 190 patients aged 65 or more and suffering from oro-facial neoplasms were treated in our department. They represent 48.6% of the total number of hospitalized tumour patients. One hundred and ten were male and 80 female. Benign tumours were found in 42 patients whereas 148 patients presented with malignant tumours. Of the malignant tumours, squamous cell carcinoma occurred in 103 patients and salivary gland tumours were the most frequently encountered benign tumours (12 patients). All patients with benign tumours were treated surgically. Of the 148 patients with malignant neoplasms, 116 were treated by surgery alone or in combination with radiotherapy and/or chemotherapy, and the remaining 32 with radiotherapy. Mortality from cancer was 28.1% and mortality from other causes was 5.8%. Postoperative morbidity in the benign tumour group of patients was minimal. In the malignant tumour group of patients, where the magnitude of surgical treatment was greater, there were no intraoperative or immediate postoperative deaths. Five patients died postoperatively whilst in hospital. Deaths were attributed to pre-existing medical problems. It is concluded that the age of the patient is not an important factor in determining the extent of surgical treatment in patients with tumours of the head and neck.

Cationic Polyacrylamide Adsorption on Epoxy Surfaces

The adsorption of a cationic polyacrylamide (acrylamide/beta-methacryloxyethyltrimethylammonium methyl sulfate copolymer) onto an imidazole catalyzed bisphenol-A based epoxy resin surface was examined by surface wetting. The work of adhesion of diodomethane, ethylene glycol and water was measured on microscopically smooth epoxy surfaces using a Wilhemy plate method, in both advancing and receding modes. The cationic polyacrylamide was adsorbed from aqueous solutions as a function of the pH of the solution. In addition to the cationic quaternary amine groups along the polymer chain, there were carboxylate groups from amide hydrolysis, which had a pKa of 10.73. The surface wetting of neither diodomethane nor ethylene glycol was sensitive to the adsorbed polyacrylamide. Wetting of the surface by water was very sensitive to the presence of adsorbed polyacrylamide. Polyacrylamides in solutions below pH 9 adsorbed onto the epoxy surface resulting in increased water adhesion to the surface. When the polyacrylamide solution was greater than pH 9 carboxylate groups ionized and the anions inhibited adsorption of the polyacrylamide. The water wetting measurements were shown to correlate with the adsorption of Pd/Sn colloidal particles used for electroless deposition of copper circuit lines on printed circuit boards.

[Polymorphous low-grade adenocarcinoma of the minor salivary glands. A case report and review of the literature]

Polymorphous low-grade adenocarcinoma is a distinct type of salivary gland carcinoma arising most often intraorally and primarily in the palate. It is characterized by bland nuclear chromatin, variation in histomorphology and low-grade malignancy. We report a case of this recently described entity in a 66 year old male, presenting most of the characteristic clinical and histologic features. A short review of the current literature concerning this tumor is included.

Lateral periodontal cyst. Review of the literature and report of a case

The lateral periodontal cyst is a rare odontogenic cyst of developmental origin. It occurs on the lateral periodontal region of a vital tooth and has specific histologic features. In this paper a case of a lateral periodontal cyst is presented and cases previously reported in the literature are reviewed. The present case concerns a 50-year old woman who presented for an asymptomatic gingival swelling of the left canine mandibular region of 2 month's duration. X-ray examination showed a well circumscribed radiolucency with a radiopaque margin lying between the roots of the lateral incisor and canine. The associated teeth were vital. Enucleation of the lesion was performed. The histologic examination of the specimen showed a cyst lined by thin non-keratinized epithelium with focal thickenings containing clear cells.

Polymorphous low-grade adenocarcinoma of the palate: report of a case with electron microscopy

A case of polymorphous, low-grade adenocarcinoma of the palate is presented with special emphasis on the histologic and ultrastructural features of this recently described entity.

Peripheral giant cell granuloma. Clinicopathologic study of 224 new cases and review of 956 reported cases

The clinical and histopathological features of 224 new cases of peripheral giant cell granuloma were studied. In addition, the data from 956 previously reported cases in the literature were evaluated and compared with the present series. Females were found to be more commonly affected than males. All age groups were found to be affected with a relative predilection from 40 to 60 years of age. The mandible was more often affected than the maxilla. Clinically, the lesions were red in color, had a smooth surface and were rubbery or with a soft consistency. The most characteristic histologic features included a non-encapsulated highly cellular mass with abundant giant cells, inflammation, interstitial hemorrhage, hemosiderin deposits, mature bone or osteoid.

The therapeutic effect of an aromatic retinoid (RO-109359) on hamster buccal pouch carcinomas

Forty male hamsters were divided into three groups. Group 1 (16 animals) received topical applications with a 0.5% solution of DMBA in liquid paraffin on the right buccal pouch for 16 weeks. Group 2 (16 animals) received DMBA for 16 weeks, plus the retinoid RO-109359 three times during the 17th week in doses of 200 mg/kg. Group 3 (8 animals) remained untreated for 16 weeks and, during the 17th week, received the retinoid as in group 2. After administration of the retinoid, a marked regression in the size of the carcinomas of the right pouch in group 2 animals was observed clinically. Histologically, these tumors consisted mostly of large necrotic areas and showed an excessive keratin loss. Although the hypervitaminosis A symptoms could not be avoided, the findings suggest that high doses have a therapeutic effect on hamster buccal pouch carcinomas.

Chromosomal breaks and sister chromatid exchanges (SCE) in patients with herpetic stomatitis

Chromosomal breakage and sister-chromatid exchanges (SCE) were studied in peripheral lymphocytes of 9 patients with primary herpetic stomatitis (PHS), 12 patients with secondary herpetic stomatitis (SHS) and 12 controls. The incidence of chromosomal breakage was significantly higher in PHS patients (mean 23%, P. = 0.0002) and in SHS patients (mean 20.25%, P. = 0.0003) compared to the controls (mean 4.2%). The incidence of SCE per 46 chromosomes was significantly higher in SHS patients (mean 16.564) compared with (P. less than 0.001) the controls (mean 11.367) and compared with (P. = 0.006) the PHS patients (mean 12.131). It is concluded that both PHS and SHS patients exhibit structural chromosomal damage; SHS patients in addition exhibit more repaired chromosomal lesions.

Sister chromatid exchanges in lymphocytes of patients with oral carcinoma

Sister chromatid exchanges (SCEs) were studied in cultured peripheral lymphocytes of 22 untreated patients with squamous cell carcinoma of the oral cavity and 29 age- and sex-matched controls. The SCE rate in cancer patients was not significantly higher compared with that found in controls, but there was a significant correlation between the SCE rate in lymphocytes of the cancer patients and the size of the primary tumor.