The Kinetics of Polyacrylamide Adsorption on Polycrystalline Gold

Fast potential step measurements (0.9 ® 1.9 ® 0.9 V, E vs. she) with simultaneous monitoring of the double layer capacity were applied in the study of the kinetics of PAA adsorption on gold from 0.5 M H2SO4, at 293 K. It was shown that the addition of PAA to the solution at 1.9 V (in the presence of a very thin oxide layer at the gold surface of 1 nm) does not affect the value of the capacity of the Au/Au2O3/PAA-solution interface, which was also confirmed by Electrochemical Impedance Spectroscopy. After the very fast cathodic reduction of the thin oxide layer (step 1.9 ® 0.9 V) for several milliseconds, the initial adsorption of PAA molecules at the bare gold surface reappeared in approx. 10 ms, causing exhaustion of the metal/solution boundary layer. The induction region (dq/dt = 0) as well as the diffusion controlled region (dq/dt = const. = f Mn((PAA); cPAA) are characteristic of low concentrations in the solution. According to the experimentally obtained linear parts of the (q / logt)-dependences, values of the diffusion coefficient of PAA-molecules with different molecular weights were calculated. These values follow fairly well the empirical equation: DPAA = 7.03 × 10–4 Mn–0.66 cm2 s–1. Using the same procedure, the diffusion coefficient of 9 × 10–6 cm2 s–1 for adsorption of »small« organic molecules, such as HMBT, was calculated

Brown Tumour in the Mandible and Skull Osteosclerosis Associated with Primary Hyperparathyroidism – A Case Report

BACKGROUND: The hyperparathyroidism (HPT) is a condition in which the parathyroid hormone (PTH) levels in the blood are increased. HPT is categorised into primary, secondary and tertiary. A rare entity that occurs in the lower jaw in association with HPT is the so-called brown tumour, which an osteolytic lesion is predominantly occurring in the lower jaw. It is usually a manifestation of the late stage of the disease. Osteosclerotic changes in other bones are almost always associated with renal osteodystrophy in secondary HPT and are extremely rare in primary HPT. This article reports a rare case of a brown tumour in the mandible as the first sign of a severe primary HPT, associated with osteosclerotic changes on the skull.CASE REPORT: A brown tumour in the mandible was diagnosed in 60 - year old female patient with no previous history of systemic disease. The x - rays showed radiolucent osteolytic lesion in the frontal area of the mandible affecting the lamina dura of the frontal teeth, and skull osteosclerosis in the form of salt and pepper sign. The blood analyses revealed increased values of PTH, calcitonin and β – cross-laps, indicating a primary HPT. The scintigraphy of the parathyroid glands showed a presence of adenoma in the left lower lobe. The tumour lesion was surgically removed together with the lower frontal teeth, and this was followed by total parathyroidectomy. The follow - up of one year did not reveal any signs of recurrence.CONCLUSION: It is critical to ensure that every osteolytic lesion in the maxillofacial region is examined thoroughly. Moreover, a proper and detailed systemic investigation should be performed. Patients should undergo regular check-ups to prevent late complications of HPT

Geranylgeraniol Reverses the Toxicity Induced by Clinical Doses of Zoledronic Acid on Gingival Epithelial Cells and Gingival Fibroblasts

BACKGROUND: Medication-related osteonecrosis of the jaw (MRONJ) is of considerable concern among clinicians and researchers, with no clear pathology mechanism, preventive, or treatment protocols. AIM: This study aimed to assess the effects of geranylgeraniol (GGOH) on the toxicity induced by clinical doses of zoledronic acid (ZOL) on gingival epithelial cells and gingival fibroblasts in vitro. METHODS: Human gingival fibroblasts and gingival epithelial cells were treated with 5, 25, or 50 μM ZOL ± 50 μM GGOH for 3 days. Viability of the cells was determined using the 3-[4, 5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide assay. Calculation of percentage of the control group, analysis of variance and Tukey post-hoc comparisons were performed to test the significance between groups, which was set at p = 0.05. Cell morphology was evaluated using light microscopy. RESULTS: ZOL significantly reduced the viability of both epithelial cells and fibroblasts at all concentrations (p < 0.05), with the exception of fibroblasts at concentration of 5 μM (p = 0.44). GGOH had positive effects on the viability of the cells treated with ZOL at all concentrations. However, statistically significant improvement was obtained only in epithelial cells at 5 and 25 μM ZOL. The cell morphology of both types of cells was improved after addition of GGOH. CONCLUSION: GGOH reverses the toxic effects of clinical doses of ZOL on gingival epithelial cells and has slightly positive, but not significant effects on gingival fibroblasts. This study suggests that GGOH may be effective in the prevention and treatment of MRONJ

Corrosion inhibition of iron in hydrochloric acid by polyacrylamide

The corrosion protection and/or adsorption of polyacrylamide (PAA) of number average molecular weight, , between 15,000 – 1,350,000 g mol-1 on mild steel and iron (99.99 % Fe) in 3 M HCl at room temperature was studied using spectrophotometry (the phenanthroline method), the weight loss method and EIS (Electrochemical Impedance Spectroscopy). It was found that the corrosion protect­tion efficiency of the PAA – adsorbed layers strongly depends on both the molar concentration of PAA in the solution and its molecular weight, reaching limiting values between 85 and 96 %. Simultaneously, it was also concluded that a relatively high surface coverage could be obtained with very low PAA concentrations (0.5 – 2 ppm), indicating the good adsorption characteristics of PAA on mild steel and iron in hydrochloride acid. The experimentally obtained results follow a Lan­gmuir adsorption isotherm. According to the best fitting parameters, the adsorption coef­f­i­cient B ranged between 2×107 and 4×108 mol-1 and depended strongly on the mole­cular weight of the PAA: B = k (for a ≈ 0.67 and k = 2.95×104) or the size of the polymer coil. As was found by EIS, the thickness of the adsorbed PAA layer was approx. 1.1 nm (for er = 15) and corresponded only to the polymer segments attached to the metal surface. On the other hand, as was found by ellipsometry, the limiting layer of the adsorbed PAA molecules was highly voluminous and relatively thick (100 – 200 nm), containing entangled polymer coils

PET PACKAGING CHARACTERIZATION BY MEANS OF DIELECTRIC THERMAL ANALYSIS AND IMPEDANCE SPECTROSCOPY

Chemical inertness and physical properties like adequate gas barrier, transparency, light weight and good recyclability, have made poly(ethylene therephtalate) (PET) particularly suitable in food packaging applications, especially in beverages and drinking water. However, several studies have shown the presence of compounds not expected a priori in packed food or bottled water and other beverages. One of the possible sources of these substances is a migration of constituents like monomers, catalysts, additives, degradation products, impurities in starting substances etc, from PET packaging. Therefore, migration of possible contaminants from PET, in normal and extreme conditions, is extensively studied and huge amount of data are reported elsewhere. As the migration process from plastics is closely related to the structure and physical properties of the packaging material, the aim of this work was to study structural changes of PET packaging in different media and under different conditions, and to correlate the data with the possibilities for migration of possible contaminants into the food in contact. It was shown that both techniques, especially DETA, could indicate structural changes into the polymer material, under certain conditions related with packaging applications, which could promote migration process

Impedance characteristics of conducting polypyrrole-poly(ethylvinylether) graft films

Impedance characterization of graft copolymers of poly(2-(N-pyrrolyl)ethylvinylether) and polypyrrole (doped with BF4-) was elucidated in comparison with pure polypyrrole doped with BF4-