Search

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.

Endogenous volatile organic compounds (VOCs) such as acetone in exhaled human breath are associated with metabolic conditions in the bloodstream. Development of compact, rapid detectors of exhaled breath chemical composition in clinical settings is challenging due to the small sample size that can be collected during a single exhalation as well as spectroscopic interference by the abundance of water. In this paper, we show that the activity of a catalytic polymer membrane (Nafion 117) toward the heterogeneous condensation reaction of immobilized resorcinol reagent with gas-phase acetone can be preserved even at 100% ambient relative humidity through the incorporation of organic acids such as vanillic or tiglic. The reaction produces a colored flavan product that permits highly selective and sensitive correlation to acetone concentration in exhaled breath. Such behavior suggests solvent displacement, analogous to homogeneous liquid-phase systems. However, unlike classic acid-base equilibria, the extent of optode water resistance is shown to increase with the pK a of the imbibed organic acid while peak signal intensity of the imbibed acid undergoes a bathochromic shift to longer wavelengths. These observations are consistent with competition between organic acid deprotonation by water in a mixed solvent system on the one hand and immobilization on the other. Finally, we demonstrate how when applied to the direct chemical analysis of acetone in exhaled human breath, the approach yields excellent correlation to blood glucose in diabetics.

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.

Measurement of acetone in human breath samples has been previously shown to provide significant non-invasive diagnostic insight into the control of a patient's diabetic condition. In patients with diabetes mellitus, the body produces excess amounts of ketones such as acetone, which are then exhaled during respiration. Using various breath analysis methods has allowed for the accurate determination of acetone concentrations in exhaled breath. However, many of these methods require instrumentation and pre-concentration steps not suitable for point-of-care use. We have found that by immobilizing resorcinol reagent into a perfluorosulfonic acid polymer membrane, a controlled organic synthesis reaction occurs with acetone in a dry carrier gas. The immobilized, highly selective product of this reaction (a flavan) is found to produce a visible spectrum color change which could measure acetone concentrations to less than ppm. We here demonstrate how this approach can be used to produce a portable optical sensing device for real-time, non-invasive acetone analysis., (Copyright © 2013 Elsevier B.V. All rights reserved.)

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.

Purpose: The carotid sheath has not been adequately assessed in the literature as a potential site of neck recurrence. The purpose of this prospective study was to investigate the histopathologic characteristics of the carotid sheath in patients with oral cancer, in an effort to clarify whether it is essential or redundant to include the carotid sheath in the neck dissection specimen., Patients and Methods: A total of 29 patients underwent 32 selective neck dissections in the Department of Oral and Maxillofacial Surgery at "Evangelismos" General Hospital of Athens, Greece. Twenty-six unilateral and 3 bilateral neck dissections were performed. The carotid sheath specimens were examined to identify possible traces of metastatic disease. The existence of lymphatic vessels and the possible presence of cancer cells within their lumen was also investigated., Results: Light microscopy of the 32 carotid sheath specimens showed that there was no evidence of tumor invasion. Immunohistochemical evaluation showed an abundance of lymphatic vessels in the carotid sheath with no evidence of microscopic intraluminal metastatic emboli., Conclusions: There was no evidence of carotid sheath invasion or presence of intraluminal lymphatic tumor emboli. Evidence of extracapsular spread warrants carotid sheath excision. Our findings suggest that if no extracapsular spread is present, there is no need to perform a tedious dissection of the carotid sheath. Preserving the carotid sheath adds protection to the neurovascular bundle, cuts operating time, and avoids possible injury to the major vessels and vagus nerve, as well as stimulation of the carotid body., (Copyright © 2010 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)

Two types of silica nanoparticles having differing concentrations of ionizable surface groups are used to investigate the interplay between nanoparticle surface charge and solvent dielectric constant in nanostructure development during layer-by-layer assembly with a cationic polyacrylamide. Zeta (zeta) potential measurements are used to determine the extent of silanol dissociation with pH. For 19-nm-diameter X-Tec 3408 silica nanoparticles from Nano-X GmbH (NanoX), complete dissociation yields a zeta-potential value of about -44mV and occurs between pH 5 and 6 in 50% ethanol-in-water mixture by volume. By contrast, 65-nm-diameter polishing silica from Electron Microscopy Supply (EMS) has a zeta potential that does not equilibrate even up to pH 7 with a value of -59mV under otherwise similar solution conditions. The more negative zeta potential at a given pH is found to substantially reduce nanoparticle adsorption. This behavior is opposite that observed when the dielectric constant of the suspension is decreased, independent of particle size. Nanoparticle surface chemical heterogeneity is discussed as a plausible explanation for such seriously discrepant behavior and the effects on multilayer electrical contact resistance for proton-exchange membrane (PEM) fuel-cell coating applications are presented., (Copyright 2010 Elsevier Inc. All rights reserved.)

Continuous, on-site monitoring of personal exposure levels to occupational chemical hazards in ambient air is a long-standing analytical challenge. Such monitoring is required to institute appropriate health measures but is often limited by the time delays associated with batch air sampling and the need for off-site instrumental analyses. In this work, we report on the first attempt to use the catalytic properties of perfluorosulfonic acid (PSA) membranes to obtain a rapid, selective, and highly sensitive optical response to trimellitic anhydride (TMA) in the gas phase for portable sensor device application. TMA is used as starting material for various organic products and is recognized to be an extremely toxic agent by the National Institute for Occupational Safety and Health (NIOSH). Resorcinol dye is shown to become immobilized in PSA membranes and diffusionally constrain an orange brown product that results from acid-catalyzed reaction with more rapidly diffusing TMA molecules. FTIR, UV/vis, reaction selectivity to TMA versus trimellitic acid (TMLA), and homogeneous synthesis are used to infer 5,7- dihydroxyanthraquinone-2-carboxylic acid as the acylation product of the reaction. The color response has a sensitivity to at least 3 parts per billion (ppb) TMA exposure and, in addition to TMLA, excludes maleic anhydride (MA) and phthalic anhydride (PA). Solvent extraction at long times is used to determine that the resorcinol extinction coefficient in 1100 EW PSA membrane has a value of 1210 m(2)/g at 271.01 nm versus a value of 2010 m(2)/g at 275.22 nm in 50 vol% ethanol/water solution. The hypsochromic wavelength shift and reduced extinction coefficient suggest that the polar perfluorosulfonic acid groups in the membrane provide the thermodynamic driving force for diffusion and immobilization. At a resorcinol concentration of 0.376 g/L in the membrane, a partition coefficient of nearly unity is obtained between the membrane and solution concentrations and a maximum conversion rate of one ambient TMA molecule for every two membrane-immobilized resorcinol molecules is observed in 15 min.

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.

Aim: The purpose of this study was to evaluate the adequacy of partial superficial parotidectomy and tumour enucleation in the surgical management of patients with pleomorphic adenoma of the parotid., Material and Methods: A total of 62 patients were treated for pleomorphic adenoma of the parotid during the years 1995-1999; 17 patients were treated with conventional superficial parotidectomy, whereas 42 patients were subjected to partial superficial parotidectomy. In three patients, tumour size and facial nerve proximity essentially resulted in enucleation of the parotid mass. In partial superficial parotidectomy, only the tumour-bearing area of the gland parenchyma was excised with identification of the main trunk and preservation of the facial nerve division that was adjacent to the tumour site with no need for more extensive facial nerve dissection., Results: There was no incidence of recurrence or facial nerve injury in our group of patients. The incidence of Frey's syndrome was 4.8%.

Renal osteodystrophy is a common long-term complication of end-stage renal disease. Involvement of the jaws is common and radiographic alterations are often one of the earliest signs of chronic renal disease. However, marked enlargement of the jaws is a rare complication of renal osteodystrophy. A case of localized asymptomatic enlargement of the mandible in a 38-year-old woman with chronic renal failure is presented. The clinical, radiographic, and histological findings were consistent with renal osteodystrophy. To our knowledge, this is the third case of localized mandibular enlargement of renal osteodystrophy reported in the English-language literature.

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.

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., (Copyright 2000 European Association for Cranio-Maxillofacial Surgery.)

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 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 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.

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 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.

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.

A rare case of hemangioendotheliosarcoma is presented. Our review of the literature confirms the difficulties we encountered in arriving at a correct clinical and pathologic diagnosis of this tumor, which seldom appears in the oral cavity, tends to be aggressive, and has a serious prognosis.

Neurofibroma is a tumor deriving from elements of neural tissue of the peripheral nerves. Its localization in the jaws is rather rare. A case of mandibular neurofibroma is presented.

The development of computerised axial tomography is briefly described and the application of this investigative procedure to the diagnosis of tumours in the maxillo-facial region is illustrated by two cases.

Lymphocyte reactivity in phytohemagglutinin-stimulated peripheral lymphocyte cultures from 22 patients with squamous cell carcinoma of the oral cavity and 29 age- and sex-matched controls was measured by the bromodeoxyuridine-Giemsa method for demonstrating sister chromatid differential staining. One hundred metaphases from each donor were counted, and the proportions of cells in the first, second, and third cycles were scored to estimate the in vitro mitogen responsiveness and cell division rates of the lymphocytes. The in vitro reactivity of peripheral lymphocytes of cancer patients was impaired in comparison with that of the controls, and the degree of reactivity of lymphocytes in cancer patients was not related to the size (greatest diameter) of the primary tumor. Results are discussed in relation to previously existing data.