Effect of glycerol on blood flow distribution in tumoral and peritumoral brain tissue

The effect of glycerol on blood flow in tumoral and peritumoral tissue was measured in 32 patients with brain tumor, 17 gliomas and 15 meningiomas. Blood flow before and after the administration of glycerol was measured by stable xenon-enhanced computed tomography. The tumor part of glioma was significantly hypoperfused. In contrast, the tumor part of meningioma was significantly hyperperfused. Peritumoral edema of both glioma and meningioma was hypoperfused. After the administration of glycerol, blood flow increased in all regions except for the tumor part of glioma. Vascular responses to glycerol may be different in these two tumor types. The steal phenomena of blood flow might occur in cases of glioma.     

Measuring strain distributions in amorphous materials.

A number of properties of amorphous materials including fatigue, fracture and component performance are governed by the magnitude of strain fields around inhomogeneities such as inclusions, voids and cracks. At present, localized strain information is only available from surface probes such as optical or electron microscopy. This is unfortunate because surface and bulk characteristics in general differ. Hence, to a large extent, the assessment of strain distributions relies on untested models. Here we present a universal diffraction method for characterizing bulk stress and strain fields in amorphous materials and demonstrate its efficacy by work on a material of current interest in materials engineering: a bulk metallic glass. The macroscopic response is shown to be less stiff than the atomic next-neighbour bonds because of structural rearrangements at the scale of 4-10 A. The method is also applicable to composites comprising an amorphous matrix and crystalline inclusions.     

Do Dislocation Loops Destroy Facet Flatness?

Following our discovery of a new surface state near the facet edges of ⁴ He crystals, it was argued that thermally excited dislocation loops could destroy the facet flatness. Recent measurements of facet profiles of very small ⁴ He crystals indicate that the activation energy of these loops would have to be more than 20 K, which is quite high. The possible consequences of this result are discussed.     

Carbamazepine and its metabolites in human perfused placenta and in maternal and cord blood

Placental transfer and metabolism of carbamazepine (CBZ) was studied in a dual recirculating placental cotyledon perfusion system and was also evaluated in 16 pairs of maternal venous and cord blood samples. Among the parameters studied as possible indicators of a successful perfusion, volume changes in perfusate divided the perfusions into two groups, whereas no significant differences between perfusions were noted in blood gas analysis or in antipyrine transfer. CBZ added into the maternal circulation crosses the placenta in the beginning quicker than antipyrine which is in agreement with the different lipid solubilities of these compounds. Because the transfer rates of antipyrine and CBZ were about the same, the mechanism of transfer of CBZ is probably similar to that of antipyrine (passive diffusion). No metabolites of CBZ could be detected in the perfusate by high-performance liquid chromatography (HPLC) or gas chromatography/mass spectrometry. With the improved HPLC methodology for CBZ metabolites, six metabolites were detected in clinical samples, including 10-hydroxy-10,11-dihydro-CBZ (10-OH-CBZ), which has been described earlier in only 1 uremic patient. Relative levels of metabolites showed significant individual differences. CBZ crosses perfused placenta rapidly, but this does not contribute to CBZ metabolites detected in maternal and fetal circulation.     

How to diagnose chronic rejection. A study in porcine intestinal allografts

The conventional Spin-Echo sequences have been the most used acquisition techniques on Magnetic Resonance Imaging (MRI) of the brain, since the beginning of 1990s. Recently, however, technological developments proposed such new fast acquisition techniques, with a dramatic reduction in acquisition time as Gradient Echo, Turbo Spin Echo, Gradient Spin Echo ed Echo Planar sequences. We investigated the comparative adequacy of the new fast sequences, in brain MR studies versus conventional sequences, on medium field strength MR equipment (.5 T). On in vitro exams S/N ratio was evaluated and on in vivo study C/N ratio between white substance grey substance and fluid were evaluated, in 15 healthy volunteers. All the exams were carried out on Philips NT5 Gyroscan MR unit operating at .5 T, with 15 mT/m power gradients. Both conventional and fast sequences Spin-Echo (SE), Inversion Recovery (IR), Gradient-Echo (GE), Turbo Spin-Echo (TSE), Gradient Spin-Echo (GRASE) and Echo Planar (EPI), all optimized to obtain T1, T2 and T1-IR weighted images, were performed. The sequences were evaluated separately comparing different acquisition techniques relative to the same type of contrast (T1, T2, and T1-IR). The results indicate the superiority of the fast acquisition techniques, both in terms of quality and acquisition times, except for T1-weighted images, where the conventional Spin-Echo sequences confirmed to be superior. In conclusion, the present study suggests that fast acquisition techniques can improve the conventional protocol of sequences, in the anatomical representation of the normal brain even with medium field strength equipment only on T2 and T1-IR weighted images. On T1-weighted imaging conventional SE acquisition technique is still the best choice. The time saving obtained with fast sequences can therefore be used for an overall improvement in the quality of images, and to apply accessory acquisition plans on routine exams.     

Ultrahigh-speed direct digital synthesizer using InP DHBT technology

Direct digital synthesizers (DDS) offer advantages such as precise beam shaping and forming over conventional RF approaches. This paper discusses novel design and process techniques that enable direct digital synthesis of S-band output frequencies using our current InP double-heterojunction bipolar transistor technology with a cantilevered base layer and undercut collector. The DDS chip operates at the world record clock rate of 9.2 GHz and capable of generating sinewaves up to 4.56 GHz. It also demonstrates state-of-the-art phase noise of -140 dBc at a frequency offset of 1 kHz and a clock frequency of 2.5 GHz. Further design and process improvements will be implemented in future generation circuits that will enable synthesis of Ku-band frequencies.     

Multilayer resonators and a bandpass filter fabricated from a novel low-temperature co-fired ceramic

The main objective of this study was to make components from a novel low-loss, low-temperature Co-fired ceramic (LTCC) dielectric, which was also compatible with a high-conductivity silver paste. The multilayer-component fabrication procedure is presented together with a composition for a tape-casting slurry, choice of conductor paste, and LTCC process parameters. A good Q factor, >100 at 2 GHz, using the novel material system has been achieved for λ/2 resonators operating in the frequency range 1.7–3.7 GHz. An excellent frequency response for a 2 GHz bandpass filter has also been achieved; the insertion losses in the passband were less than −2 dB (bandwidth 60 MHz) and the attenuation more than 25 dB in the stopband located 190 MHz higher.     

Distribution and localization of galectin purified from Rana catesbeiana oocytes

Galectins are a family of lectins that recognize beta-D-galactosides independently of calcium ions, and are widely distributed in animals. To characterize a galectin previously purified from oocytes of Rana catesbeiana (American bullfrog), we studied its distribution and localization in several tissues from this frog. Hemagglutination assay and western blotting showed that this lectin is present in many tissues including the liver, skin, kidney, skeletal muscle, and sciatic nerve, but is particularly concentrated in the ovary. Light microscopic immunohistochemistry showed that this lectin is localized in such places as cell-cell junctions, basement membranes, extracellular matrix, or secretory substances in several organs, indicating that this galectin is mainly distributed extracellularly. However, in the ovary, light microscopy showed that this lectin is present in or associated with the yolk platelet. Electron microscopy further revealed that it is localized in the periphery of the yolk platelet (the yolk plasm), but not in the cortical granule. These results indicate that Rana oocytes contain abundant galectin in their yolk platelets in contrast to Xenopus laevis oocytes, which have been found not to contain galectins but other classes of lectins in their yolk platelets and cortical granules.     

Nuclear antiferromagnetic exchange in two dimensional solid3He

Measurements are reported of the magnetic susceptibility of pure³He films, at coverages for which the nuclear exchange interaction is antiferromagnetic. A comparison is made with earlier results obtained on preplated graphite. The data suggest that all the spins participate in the exchange.