Hydrolysis of organometallic and metal-amide precursors: synthesis routes to oxo-bridged heterometallic complexes, metal-oxo clusters and metal oxide nanoparticles.

The hydrolysis reaction between Brønsted basic organometallic or metal-amide reagents with Brønsted acidic OH groups from water or metal-hydroxides may act as a controlled stoichiometric strategy for the formation of M-O-M bonds, if careful consideration of reaction conditions is employed. This article explores the utilisation of highly reactive organometallic and metal-amide complexes from across the periodic table as reagents for the synthesis of metal-oxo clusters, oxo-bridged heterobimetallics and metal oxide nanoparticles. Such reactivity typically occurs at low temperatures with the release of hydrocarbon or amine by-products. The impact of ligand coordination, M-C bond strength, M-OH acidity and reaction temperature are discussed.

Ultrastable glasses portray similar behaviour to ordinary glasses at high pressure.

Pressure experiments provide a unique opportunity to unravel new insights into glass-forming liquids by exploring its effect on the dynamics of viscous liquids and on the evolution of the glass transition temperature. Here we compare the pressure dependence of the onset of devitrification, Ton, between two molecular glasses prepared from the same material but with extremely different ambient-pressure kinetic and thermodynamic stabilities. Our data clearly reveal that, while both glasses exhibit different dTon/dP values at low pressures, they evolve towards closer calorimetric devitrification temperature and pressure dependence as pressure increases. We tentatively interpret these results from the different densities of the starting materials at room temperature and pressure. Our data shows that at the probed pressures, the relaxation time of the glass into the supercooled liquid is determined by temperature and pressure similarly to the behaviour of liquids, but using stability-dependent parameters.

Dielectric Investigation of Parylene D Thin Films: Relaxation and Conduction Mechanisms.

Parylene is a generic name indicating a family of polymers with the basic chemical structure of poly-p-xylylene. Parylene N and Parylene C are the most popular for applications. Curiously, Parylene D (poly( dichloro-p-xylylene), (C8H6Cl2)) was forgotten for applications. This report is the consequence of a later availability of a commercial dimer of Parylene D and also to the recent advent of fluorinated Parylenes allowing extending applications at higher temperatures. In our work, from a dielectric analysis, we present the potentialities of Parylene D for applications particularly interesting for integration in organic field-effect transistors. Dielectric and electrical properties, macromolecular structures, and dynamics interaction with electric field as a function of frequency and temperature are studied in 5.8 µm thick Parylene D grown by chemical vapor deposition. More exactly, the dielectric permittivity, the dissipation factor, the electrical conductivity, and the electric modulus of Parylene D were investigated in a wide temperature and frequency ranges from -140 to +350 °C and from 0.1 Hz to 1 MHz, respectively. According to the temperature dependence of the dielectric permittivity, Parylene D has two different dielectric responses. It is retained as a nonpolar material at very low temperature (like Parylene N) and as a polar material at high temperature (like parylene C). The dissipation factor shows the manifestation of two relaxations mechanisms: γ and ß at very low and high temperatures, respectively. The γ relaxation is assigned to the local motions of the C-H end of the chains when the cryogenic temperature range is approached. A broad peak in tan δ is assigned to the ß relaxation. It corresponds to rotational motion of some polar C-Cl groups. For temperature above 260 °C a mechanism of Maxwell-Wagner-Sillars polarization at the amorphous/crystalline interfaces was identified with two activation energies of Ea1 = 2.12 eV and Ea2 = 3.8 eV. Moreover, the conductivity and the dielectric permittivity relaxation processes have been discussed in terms of nearly constant loss (NCL) and universal dynamic regime (UDR). Finally, ionic conduction and electrode polarization effects are identified at very high temperatures and their physical origins are discussed.

Affinity and its derivatives in the glass transition process.

The thermodynamic treatment of the glass transition remains an issue of intense debate. When associated with the formalism of non-equilibrium thermodynamics, the lattice-hole theory of liquids can provide new insight in this direction, as has been shown by Schmelzer and Gutzow [J. Chem. Phys. 125, 184511 (2006)], by Möller et al. [J. Chem. Phys. 125, 094505 (2006)], and more recently by Tropin et al. [J. Non-Cryst. Solids 357, 1291 (2011); ibid. 357, 1303 (2011)]. Here, we employ a similar approach. We include pressure as an additional variable, in order to account for the freezing-in of structural degrees of freedom upon pressure increase. Second, we demonstrate that important terms concerning first order derivatives of the affinity-driving-force with respect to temperature and pressure have been previously neglected. We show that these are of crucial importance in the approach. Macroscopic non-equilibrium thermodynamics is used to enlighten these contributions in the derivation of C(p),κ(T), and α(p). The coefficients are calculated as a function of pressure and temperature following different theoretical protocols, revealing classical aspects of vitrification and structural recovery processes. Finally, we demonstrate that a simple minimalist model such as the lattice-hole theory of liquids, when being associated with rigorous use of macroscopic non-equilibrium thermodynamics, is able to account for the primary features of the glass transition phenomenology. Notwithstanding its simplicity and its limits, this approach can be used as a very pedagogical tool to provide a physical understanding on the underlying thermodynamics which governs the glass transition process.

Measurement properties of the wheelchair outcome measure in individuals with spinal cord injury.

STUDY DESIGN: One-week retest methodological study. OBJECTIVES: To assess the reliability and validity of the wheelchair outcome measure (WhOM) in a sample of individuals with spinal cord injury (SCI). SETTING: Vancouver, British Columbia, Canada. METHODS: The WhOM measures the impact of wheelchair interventions on a user's self-selected participation outcomes. The WhOM was administered to 50 participants on two occasions by the same rater, 1 week apart, to assess test-retest reliability. To determine inter-rater reliability, the WhOM was administered a third time approximately 72 h later by a different rater. Validity was evaluated by correlating scores from the WhOM with scores from the Assessment of Life Habits (LIFE-H). RESULTS: The test-retest intraclass correlation coefficients (ICC(2, 2)) for the WhOM satisfaction (Sat) and WhOM importance (Impt) × Sat scores were 0.83 (95% confidence interval (CI), 0.72-0.90) and 0.88 (95% CI, 0.79-0.93), respectively. The inter-rater ICC for the WhOM Sat and WhOM Impt × Sat scores were 0.91 (95% CI, 0.85-0.95) and 0.90 (95% CI, 0.83-0.94), respectively. As hypothesized, most scores on the WhOM were fair to moderate (r=0.3-0.5) and positively correlated with scores on the LIFE-H. CONCLUSION: The WhOM is a new outcome measure that demonstrates good reliability and validity among individuals with SCI. It is designed to assist wheelchair users identify and evaluate the impact of wheelchair interventions on participation level outcomes. The WhOM may be applicable for clinical- or research-oriented purposes.

Highly sensitive parylene membrane-based ac-calorimeter for small mass magnetic samples.

We report the microfabrication and operation of a highly sensitive ac-calorimeter designed to characterize small mass magnetic systems operating at very low frequencies (from 0.1 to 5 Hz) in a temperature range from 20 to 300 K. The calorimetric cell is built in the center of a 500 nm thick polymeric membrane of parylene C held up by a Cu frame. On both sides of the membrane defining a three layer structure, electrical leads, heater, and thermometer are deposited as thin film layers of NbN(x), with different nitrogen contents, taking benefit of the poor thermal conductance of niobium nitride to thermally isolate the system. This suspended structure ensures very low heat capacity addenda with values in the microJ/K over the 1 mm(2) area of the measurement cell. The structuring of the membrane along with suspending of the sensing part only by the parylene bridges leads to a highly reduced thermal link. The calorimeter has been characterized as a function of frequency, temperature, and magnetic field. The thermal link measured is really small reaching values well below 10(-8) W/K at 50 K. With these characteristics the frequency of adiabaticity is typically around few hertz and energy exchanges as small as 1 pJ can be detected. Measurements have been performed on Co/Au thin films and on the GdAl(2) microcrystal where the ferromagnetic phase transition is clearly evidenced.

Satisfaction with participation using a manual wheelchair among individuals with spinal cord injury.

STUDY DESIGN: Cross-sectional. OBJECTIVES: To describe self-identified indoor and outdoor wheelchair-oriented participation outcomes and to report satisfaction with the identified outcomes by people with spinal cord injury (SCI). SETTING: Vancouver, British Columbia. METHODS: Participation outcomes were identified using the Wheelchair Outcome Measure and classified using the International Classification of Functioning, Disability, and Health (ICF). RESULTS: The average age of the 51 community-dwelling subjects with SCI was 43.7(+/-10.7) years. Of them, 84% were men, 64% had tetraplegia and 66% used a manual wheelchair. There were 258 indoor and 257 outdoor participation outcomes identified by this sample with most outcomes falling into the 'community, social, and civil life' (36.5%), 'domestic life' (23.7%) and 'mobility' (18%) domains of the ICF. All domains had a mean satisfaction score of 7.1/10 or greater except for the indoor 'mobility' domain that had a mean satisfaction score of 6.1/10. Satisfaction scores with performance of the specific participation outcomes ranged from high (10/10) to low (2/10) with most scores falling above 7/10. CONCLUSION: Community-dwelling people with SCI commonly engage in wheelchair-oriented participation outcomes related to 'community, social, and civil life', 'domestic life' and 'mobility' and tend to be satisfied with their performance of these participation outcomes. This information is useful for clinicians and may help to guide assessment and intervention.

Temperature of systems out of thermodynamic equilibrium.

Two phenomenological approaches are currently used in the study of the vitreous state. One is based on the concept of fictive temperature introduced by Tool [J. Res. Natl. Bur. Stand. 34, 199 (1945)] and recently revisited by Nieuwenhuizen [Phys. Rev. Lett. 80, 5580 (1998)]. The other is based on the thermodynamics of irreversible processes initiated by De Donder at the beginning of the last century [L'Affinite (Gauthier-Villars, Paris, 1927)] and recently used by Moller et al. for a thorough study of the glass transition [J. Chem. Phys. 125, 094505 (2006)]. This latter approach leads to the possibility of describing the glass transition by means of the freezing-in of one or more order parameters connected to the internal structural degrees of freedom involved in the vitrification process. In this paper, the equivalence of the two preceding approaches is demonstrated, not only for glasses but in a very general way for any system undergoing an irreversible transformation. This equivalence allows the definition of an effective temperature for all systems departed from equilibrium generating a positive amount of entropy. In fact, the initial fictive temperature concept of Tool leads to the generalization of the notion of temperature for systems out of thermodynamic equilibrium, for which glasses are just particular cases.

Laser treatment of pigmented lesions and tattoos.

Benign pigmented lesions and tattoos are often very responsive to laser treatment. The chromophore in most cases is melanin, although other endogenous and exogenous pigments can be targeted. The chromophore and its distribution in the skin, as well as the underlying biological processes, all help determine the best laser, if any, for a given pigmented lesion. Epidermal lesions respond well to shorter wavelengths (up to 755 nm), whereas for deeper lesions, 694 nm or longer are typically used. The 1,064-nm Nd:YAG laser is best for treating darker skinned individuals. Multicolored tattoos may need several wavelengths to best target individual ink colors.

The pulsed dye laser for cutaneous vascular and nonvascular lesions.

The pulsed dye laser was originally developed for the treatment of vascular lesions, especially hemangiomas and port-wine stains. The central concept of pulsed-dye laser is to preserving the epidermis by allowing hemoglobin to be more precisely targeted within lesions. More recently, the pulsed dye laser has also been used in the treatment of a wide spectrum of nonvascular lesions. Because of its safety profile, and its selectivity in targeting lesions, therapists can comfortably treat a wide variety of lesions in all age groups and anatomic sites.

Laser treatment of port-wine stains and hemangiomas.

Since their discovery, lasers have truly advanced and broadened our options for the treatment of port-wine stains and hemangiomas. It is a blending of many sciences and much effort that allows us the opportunity today to selectively treat these vascular processes with relative effectiveness and significant safety. Ongoing study and development continue to offer hope on increasing benefit for our patients. Laser systems with variable wavelengths, pulse durations, and delivery methods will help accommodate the diversity of various port-wine stains and hemangiomas that are encountered in medicine.

Bowen's disease of the distal digit. Outcome of treatment with carbon dioxide laser vaporization.

BACKGROUND: Bowen's disease (squamous cell carcinoma in situ) is an intraepithelial neoplasm that can transform into invasive squamous cell carcinoma. The preferred method of eradication for Bowen's disease is surgical excision. However, when Bowen's disease occurs on the digit, surgical removal can lead to scar contracture and loss of use of the finger. OBJECTIVE: To assess the utility of carbon dioxide (CO2) laser vaporization in eradicating Bowen's disease of the finger while maintaining the full range of motion and use of the digit. METHODS: Five patients were treated with CO2 laser vaporization for Bowen's disease of the digit. Patients were followed postoperatively for recurrence, clinical appearance, especially for scar formation, and function of the involved joints over a 6-month to 3-year period. RESULTS: Four of five patients had no recurrence. Healing resulted in only modest alterations in the cosmetic appearance in comparison with the surrounding untreated skin. Posttreatment biopsy showed slight thinning of the epidermis and mild fibroplagia limited to the papillary dermis. Patients reported only mild post-procedure discomfort and no patients had any loss of function of the digit. CONCLUSIONS: CO2 laser vaporization may be a safe and effective means by which to eradicate Bowen's disease of the finger without the risk of scar contracture and loss of function of the digit.

Psoriasis response to the pulsed dye laser.

BACKGROUND AND OBJECTIVE: In psoriasis the blood vessels are enlarged and dilated. These vessels, the psoriatic microvasculature, have been implicated as participating in the pathogenesis of psoriasis. The purpose of this preliminary study was to use the flash-lamp-pumped pulsed dye laser, which selectively damages dermal vessels, to treat psoriatic plaques and to evaluate the role of the vasculature in the therapeutic response. MATERIALS AND METHODS: Ten patients with psoriasis were treated with the pulsed dye laser on single, stable psoriasis plaques. Treatments varied between one and three times, and the lesional response was graded using a scale for erythema, scaling, and infiltration. RESULTS: Six of 10 patients experienced a beneficial clinical effect after therapy. The psoriasis severity scale in these patients was reduced to 2.2 +/- 1.3 compared with a 7.2 +/- 1.7 grade for control areas. The plaques readily developed crusting with therapy, with one leg lesion healing with atrophy. Histopathology in three patients immediately after therapy showed no epidermal damage. One week after laser therapy, the necrotic former epidermis was apparent in superficial crusting. Epidermal thinning and regeneration was seen without any signs of psoriasis. CONCLUSIONS: Pulsed dye laser therapy may improve plaque psoriasis. This improvement may be related to the role the microvasculature plays in psoriasis.

Cryoglobulinemia and cutaneous leukocytoclastic vasculitis associated with hepatitis C virus infection.

Hepatitis C virus infection is a frequent cause of non-A, non-B hepatitis worldwide. Resultant morbidity is significant; chronic liver disease develops in 50% of infected persons. Since serologic testing has become available there have been several reports of cutaneous findings in association with hepatitis C virus infection, including vasculitis, cryoglobulinemia, urticaria, and lichen planus. We describe a patient with cryoglobulinemia, chronic cutaneous leukocytoclastic vasculitis, and hepatitis C virus infection. Hepatitis C virus infection should be included in the differential diagnosis of the causes of cryoglobulinemia and leukocytoclastic vasculitis.

Clinical efficacy of the pulsed dye laser in the treatment of vascular lesions.

BACKGROUND: Increasing the selectivity of laser-induced damage is an ongoing goal for the laser treatment of cutaneous lesions. The flashlamp-pumped pulsed dye laser has significantly participated and advanced this pursuit. This is especially true in its use for the treatment of cutaneous vascular lesions. OBJECTIVE: A review of the development and current use of this laser for the treatment of cutaneous vascular lesions will be presented. METHODS: The laser has been designed to limit laser energy absorption and damage to hemoglobin and the blood vessel. This has been done by setting the wavelength at 577 to 585 nm and the pulse duration at 360 to 450 microseconds. RESULTS: The therapeutic results have been beneficial for almost all types of superficial small vessel vascular lesions regardless of lesional anatomic site or patient age. These lesions include port-wine stains, telangiectasia, capillary hemangioma, and other angiomata and vascular ectasia. Deeper cutaneous vascular processes and lower extremity telangiectases have proven to be less responsive to therapy. The increased vascular selectivity has allowed for a dramatic decrease in adverse effects when compared to previously used laser systems. CONCLUSION: Based on many thousands of treatment sessions and follow-up evaluation, the pulsed dye laser appears to have the greatest margin of safety in the treatment of cutaneous vascular lesions, especially for the pediatric population.

Treatment of cutaneous hemangiomas by the flashlamp-pumped pulsed dye laser: prospective analysis.

Thirty-three cutaneous capillary and mixed hemangiomas in 24 patients were treated prospectively with the flashlamp-pumped pulsed dye laser. Patients ranged in age from 2 weeks to 7 months; the follow-up period was up to 22 months. Some patients received therapy until the lesion was almost clear or until the lesion failed to respond; others received treatment only until active capillary lesional proliferation abated. In the first group of patients, 18 of 25 lesions that were 3 mm or less in elevation lightened with therapy (93.9% +/- 4.6% in 4.1 +/- 1.6 treatment sessions) and flattened to 0.3 +/- 0.4 mm in thickness. The seven lesions that were 4 mm or more in thickness lightened 85.7% +/- 7.3% in 7.0 +/- 2.0 treatment sessions but showed less diminution in thickness (to 3.4 +/- 3.6 mm; p less than 0.01). The second group of patients, who received therapy until proliferation ceased, required just one to three therapeutic sessions. Three of the four lesions that showed residual atrophy were 4 mm or greater in thickness; the fourth lesion was ulcerated on presentation. None of the lesions had residual induration or scarring. We conclude that the flashlamp-pumped pulsed dye laser may successfully prevent enlargement and promote involution of capillary hemangiomas with minimal adverse effects. Therapy is most appropriate for patients with hemangiomas at sites of potential functional impairment, of maceration or ulceration, and of significant cosmetic disfigurement. Therapy should be initiated as early as possible, when lesions are relatively flat, for optimal results.