Enhancement of the dielectric response in polymer nanocomposites with low dielectric constant fillers.

In order to increase the dielectric constants of polymer-based dielectrics, composite approaches, in which inorganic fillers with much higher dielectric constants are added to the polar polymer matrix, have been investigated. However, high dielectric constant fillers cause high local electric fields in the polymer, resulting in a large reduction of the electric breakdown strength. We show that a significant increase in the dielectric constant can be achieved in polyetherimide nanocomposites with nanofillers whose dielectric constant can be similar to that of the matrix. The presence of nanofillers reduces the constraints on the dipole response to the applied electric field, thus enhancing the dielectric constant. Our results demonstrate that through nanostructure engineering, the dielectric constant of nanocomposites can be enhanced markedly without using high dielectric constant nanofillers.

Decoupling of ionic conductivity from structural dynamics in polymerized ionic liquids.

Charge transport and structural dynamics in low molecular weight and polymerized 1-vinyl-3-pentylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids (ILs) are investigated by a combination of broadband dielectric spectroscopy, dynamic mechanical spectroscopy and differential scanning calorimetry. While the dc conductivity and fluidity exhibit practically identical temperature dependence for the non-polymerized IL, a significant decoupling of ionic conduction from structural dynamics is observed for the polymerized IL. In addition, the dc conductivity of the polymerized IL exceeds that of its molecular counterpart by four orders of magnitude at their respective calorimetric glass transition temperatures. This is attributed to the unusually high mobility of the anions especially at lower temperatures when the structural dynamics is significantly slowed down. A simple physical explanation of the possible origin of the remarkable decoupling of ionic conductivity from structural dynamics is proposed.

Charge transport and dipolar relaxations in imidazolium-based ionic liquids.

Charge transport and dipolar relaxations in a series of imidazolium-based ionic liquids are studied by means of broadband dielectric spectroscopy. Despite the shift of more than 5 decades in the dielectric spectra upon systematic variation of the anion, scaling with respect to the dc conductivities and the characteristic rates yields a collapsing plot. The dielectric spectra are described at higher frequencies in terms of dipolar relaxations whereas hopping conduction in a random spatially varying energy landscape is quantitatively shown to dominate the spectra at lower frequencies. The beta-relaxations observed for both the precursor and the ionic liquids are assigned to librational motion of the imidazolium ring. The corresponding dielectric strength exhibits a strong dependence on the anion.

Universal scaling of charge transport in glass-forming ionic liquids.

Charge transport and glassy dynamics of a variety of glass-forming ionic liquids (ILs) are investigated in a wide frequency and temperature range by means of broadband dielectric spectroscopy, differential scanning calorimetry and rheology. While the absolute values of dc conductivity and viscosity vary over more than 11 decades with temperature and upon systematic structural variation of the ILs, quantitative agreement is found between the characteristic frequency of charge transport and the structural alpha-relaxation. This is traced back to dynamic glass transition assisted hopping as the underlying mechanism of charge transport.

Charge transport and glassy dynamics in imidazole-based liquids.

Broadband dielectric spectroscopy, differential scanning calorimetry, rheology, and pulsed field gradient-nuclear magnetic resonance (PFG NMR) are combined to study glassy dynamics and charge transport in a homologous series of imidazole-based liquids with systematic variation of the alkyl chain length. The dielectric spectra are interpreted in terms of dipolar relaxation and a conductivity contribution. By applying the Einstein, Einstein-Smoluchowski, and Stokes-Einstein relations, translational diffusion coefficients--in quantitative agreement with PFG NMR measurements--are obtained. With increasing alkyl chain length, it is observed that the viscosity increases, whereas the structural alpha-relaxation rate decreases, in accordance with Maxwell's relation. Between the rate omega(e) of electrical relaxation and the rate omega(alpha) of the structural alpha-relaxation, scaling is observed over more than six decades with a decoupling index of about 2.

Electrical conductivity and translational diffusion in the 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid.

Broadband dielectric and terahertz spectroscopy (10(-2)-10(+12) Hz) are combined with pulsed field gradient nuclear magnetic resonance (PFG-NMR) to explore charge transport and translational diffusion in the 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid. The dielectric spectra are interpreted as superposition of high-frequency relaxation processes associated with dipolar librations and a conductivity contribution. The latter originates from hopping of charge carriers on a random spatially varying potential landscape and quantitatively fits the observed frequency and temperature dependence of the spectra. A further analysis delivers the hopping rate and enables one to deduce--using the Einstein-Smoluchowski equation--the translational diffusion coefficient of the charge carriers in quantitative agreement with PFG-NMR measurements. By that, the mobility is determined and separated from the charge carrier density; for the former, a Vogel-Fulcher-Tammann and for the latter, an Arrhenius temperature dependence is obtained. There is no indication of a mode arising from the reorientation of stable ion pairs.

18-Fluorine-labelled 2-deoxy-2-fluoro-D-glucose positron emission tomography/computed tomography standardised uptake values: a non-invasive biomarker for the risk of metastasis from choroidal melanoma.

AIMS: To correlate the clinical, ultrasound and pathological features of the eyes first evaluated by 18-fluorine-labelled 2-deoxy-2-fluoro-d-glucose (FDG) positron emission tomography (PET)/computed tomography and then enucleated for choroidal melanoma. METHODS: 14 consecutive patients enucleated for choroidal melanoma were examined. At presentation, clinical, ultrasound and PET/computed tomography imaging were carried out. Ultrasound was used to measure the tumour size and evaluate the tumour shape and intrinsic vascularity (blood flow). Histopathological and immunohistochemical evaluations included tumour cell type, necrosis, glycogen content, vascularity and extrascleral extension. RESULTS: 13 tumours were T3 and one T2 (American Joint Committee on Cancer - International Union against Cancer). The mean tumour height was 10.6 (range 3.5-17.7) mm with a largest basal dimension of 19.3 (range 14.5-30) mm. Patients having melanoma with the highest six standardised uptake values ((SUV) > or =4.0) were (on average) >10 years older, their melanomas had larger basal dimensions and were epithelioid-cell type; three melanomas were centred anterior to the equator; three contained enlarged blood vessels (>150 mum in diameter); and three formed extrascleral extension. Patients with the two highest SUV tumours died due to metastatic melanoma. CONCLUSION: PET/computed tomography imaging offers a physiological assessment of glucose metabolism in primary choroidal melanomas. Increased FDG PET/computed tomography SUV was positively correlated with known clinical, pathological and ultrasound features linked to metastatic potential of choroidal melanoma.

Anterior chamber paracentesis cytology (cytospin technique) for the diagnosis of intraocular lymphoma.

AIM: To report on the diagnosis of intraocular lymphoma by aqueous cytology. METHODS: Four patients suspected of having intraocular lymphoma were evaluated by anterior chamber (AC) paracentesis with cytology (cytospin technique). All had a history of non-ocular lymphoma and presented with at least one plus anterior chamber cells despite intensive glucocorticoid therapy. A 25 gauge needle was inserted through clear cornea (bevel up), over the iris stroma, so as to drain the AC. The aqueous humour was sent for cytopathology (cytospin technique), culture, and sensitivity tests. RESULTS: All procedures were diagnostic. Three were lymphoma and the fourth was culture positive for Propionibacterium endophthalmitis. No secondary glaucoma, hyphaema, cataract or infections were related to AC paracentesis. CONCLUSIONS: In this series, AC aspiration cytology enhanced by the cytospin technique was an effective, minimally invasive alternative to vitrectomy based biopsy. This technique should be considered to rule in the diagnosis of intraocular lymphoma in selected cases with cells in the anterior chamber.

A simple method for fixation and microdissection of frozen fresh tissue sections for molecular cytogenetic analysis of cancers.

Microdissection has been widely used for procuring DNA from specific microscopic regions of formalin fixed, paraffin embedded tissue sections. We have developed a method for fixation and microdissection of frozen fresh biopsy tissue sections. Five micrometer frozen fresh tissue sections were fixed with ethanol and stored at room temperature. Well defined regions from hematoxylin and eosin (H & E) stained or unstained sections were briefly steamed and microdissected using a needle. The dissected tissue was digested with proteinase K and DNA was isolated. Whole genome amplifications were obtained by degenerate oligonucleotide primed polymerase chain reaction (DOP-PCR) from these samples. The reliability of this technique was demonstrated by comparing conventional comparative genomic hybridization (CGH) with DOP-PCR-CGH. The advantages of this method are that frozen fresh sections can be fixed easily and stored for more than 4 years, it is easy to microdissect and pick-up very minute regions (0.1 mm(2)), and it is rapid; microdissection and purification can be accomplished within 3 h. Using DNA from microdissected sections, DOP-PCR-CGH revealed genetic abnormalities more accurately than conventional CGH. Although this novel method was demonstrated using DOP-PCR-CGH, we believe that it will be useful for other genetic analyses of specific small regions and cell populations. We also observed whether storage time, H & E staining and crude DNA extracts affected the quality of amplified DNA. DNA integrity was maintained for at least 49 months in ethanol fixed sections that were stored at room temperature, but DNA was gradually degraded after one month if the ethanol fixed sections had been H & E stained and stored. When crude DNA extracts from H & E stained sections were used, the size of the DOP-PCR product was reduced. Our study suggests that ethanol fixed tissue sections may be stored at room temperature for at least 4 years without DNA degradation, the H & E stains may not affect the quality of amplified DNA, but H & E or other components in the staining process may reduce the size of DOP-PCR product, which is critical for the quality of CGH hybridization.

The Finger iridectomy technique: small incision biopsy of anterior segment tumours.

AIMS: To develop a minimally invasive, maximally effective method to biopsy anterior segment tumours. METHODS: A 25 gauge aspiration cutter (vitrector) was used to biopsy anterior segment tumours. The probe was introduced under sodium hyaluronate 1% and through a 1 mm incision. Aspiration (600 mm Hg) cutting (300 cpm) was performed to obtain specimens for cytology and histopathology. RESULTS: Diagnostic material was obtained in nine of 10 (90%) cases. Diagnoses included iris naevus, iris stroma, malignant melanoma, melanocytoma, epithelial inclusion cyst, and sarcoid granuloma. All corneal wounds were self sealing. One patient developed a transient postoperative increase in intraocular pressure. Within the follow up of this study, no patients suffered intraocular haemorrhage, infection, cataract or vision loss. CONCLUSION: The Finger iridectomy technique was a minimally invasive and very effective biopsy technique. Aspiration cutting yielded relatively large pieces of tissue (and cells) used for cytopathological and histopathological evaluation. Small incision surgery allowed for rapid rehabilitation and no significant complications.

[The clinical, imaging and electrophysiological correlations in Paget's disease]. / Corelatii clinice, imagistice si electrofiziologice în boala Paget.

The work presents two cases of Paget disease with a complex neurological description. The first case, a woman of 59 years, presents a spastic paraparesis with multiple syndrome of cranial nerves. The second case, a woman of 60 years, presents a spastic tetraparesis with myoclonus. The cranial radiography stood out to both patients the thickness of the bones of the skull in the context of the existence of some grown titres of the alkaline phosphate. The examination CT to the second patient indicates an important cerebral atrophy. Auditory evoked potentials (AEPs) show to the first patient the increasing in time of the latency of the first wave and to the second patient the inequality of latency from the right to left a wave I and the growing latency of the interval I-III to the left. Visual evoked potentials (VEPs) to the second patient indicate the delay of all the component parts. If the radiological examination asserts the diagnosis, the electrophysiological probings diagnose the complications and the evolution of the disease.

Fine structure of lipid storage in epithelial cells lining bile ducts in Niemann-Pick's disease.

Lipid lamellated vacuoles have been found in epithelial cells lining bile ducts in a case of Niemann-Pick's disease. The lipidic vacuoles were few and small within these cells and were placed in the cell apical area.