Climatic aging of composite aviation materials: I. Aging mechanisms

The review of investigations performed by the All-Russia Research Institute of Aviation Materials and Altai State University for 1976–2010 is devoted to the climatic aging of polymer composite aviation materials. The primary physicochemical transformations in epoxy binders and reinforcing fibers under the action of climatic factors are considered.     

Measurements of the orthogonal magnetic components of the pulse component of infralow and very low electromagnetic fields at svalbard

A complex of equipment for recording three components H _x , H _y , and H _z of the pulse component of an electromagnetic field in the range of infralow-very low frequencies, which is incorporated in the geophysical observatory of the Polar Geophysical Institute (Barentzburg, Spitsbergen archipelago), is described. The complex operates under the control of the Linux operational system and is integrated in the local observatory computer network, thus providing both the remote access to data and the GPS time synchronization. The use of buffer transformers in both the signal circuit and the circuit for connection to the collective observatory supply line made it possible to improve the electromagnetic compatibility of this complex with the main instruments of the observatory. The technique for conducting the absolute calibration of the equipment is described.     

Artefacts of electron paramagnetic resonance dosimetry caused by a mechanical effect on samples of tooth enamel

It has been ascertained that in the process of the mechanical preparation of tooth enamel, two types of paramagnetic centres are formed. The centres of one type, the long-lived ones, occurred in the process of friction of dental borers against the enamel. Their number grew with an increase of the treated surface area and the rotation rate of the borers. The electron paramagnetic resonance signal of such radicals looked like a symmetric singlet with the width deltaHpp=0.094 mT and g=2.0029. The other, short-lived centres, occurred when tooth enamel was crushed into small granules, which caused an increase in the background signal intensity. The mechanism of formation of paramagnetic centres in enamel during the process of teeth treatment and prepartion has been considered. The estimation of an increase in the reconstructed absorbed dose due to the contribution from the mechanically induced signal has been made. Contamination of tooth enamel samples with diamond crumb during diamond borer preparation has been shown to lead to an imaginary increase in radiation-induced signal intensity and, consequently, to an increase in the reconstructed dose.     

Mosaicism in sporadic neurofibromatosis 2 patients

More than half of neurofibromatosis 2 (NF2) patients represent de novo mutations which could have occurred at either pre-zygotic or post-zygotic stages. A post-zygotic mutation can result in mosaicism. In four sporadic NF2 patients, we found NF2 mutations in only a portion of corresponding leukocytes. In two other sporadic patients, no mutations were found in leukocytes but constitutional NF2 mutations were suggested by identical mutations in different tumors from each patient. We screened leukocyte DNA from a total of 16 inherited and 91 sporadic NF2 patients, and found NF2 mutations in 13 (81%) of the former and in 46 (51%) of the latter cases. The 30% difference in the rate of detection of mutations ( P = 0.051) might be partially explained by mosaicism in a portion of sporadic NF2 patients who carry the mutations in such a fashion that their leukocytes are unaffected. Among sporadic cases, we found mutations more frequently in patients with severe phenotypes (59%) than in patients with mild phenotypes (23%) (difference of 36%, P = 0.007). Mosaicism might be more common in the latter patient group since small populations of mutation-bearing cells can in some cases result in mild phenotypes and can also lead to difficulties in identifying mutations. No mutations were found in eight patients suspected of having NF2. Mosaicism with an extremely small population of affected cells may explain the incomplete phenotypes in some of these patients and the lack of mutations in their leukocytes. These findings suggest that mosaicism is relatively common in NF2 and may have important implications for diagnosis, prognosis and genetic counseling.     

Nasopharyngeal carcinoma with intracranial spread: CT and MR characteristics

PURPOSE: Nasopharyngeal carcinoma (NPC) frequently spreads intracranially. We compare CT and MRI in identifying intracranial spread and reexamine the route of infiltration. METHOD: One hundred fourteen consecutive patients with proven NPC were evaluated prospectively with T1-, T2-weighted, contrast-enhanced MRI and CT. RESULTS: MRI showed 35 (31%) patients with middle cranial fossa involvement. Twenty-nine (25%) patients had cavernous sinus infiltration, while six (5%) showed only dural thickening. The most common route of spread is through the foramen ovale (FO) (12/35 patients, 34%), followed by skull base destruction (6/35 patients, 17%), foramen lacerum (FL) (6/35 patients, 17%), sphenoid sinus (6/35 patients, 17%), and combined FO and FL (5/35 patients, 14%). Using MRI as a standard, CT demonstrated the following involvement: cavernous sinus in 26 of 29 (90%) patients, FO in 9 of 12 patients, skull base in 6 of 6 patients, FO and FL in 3 of 5 patients, FL in 6 of 6 patients, sphenoid sinus in 6 of 6 patients and dura in 0 of 18 patients. CONCLUSION: It is believed that NPC most commonly spreads intracranially via the FL or by direct erosion. Perineural spread through the FO is an important route, which explains why with CT evidence of cavernous sinus involvement there may be no skull base erosion. These findings are best seen on MRI.