Dissociative electron attachment to the radiosensitizing chemotherapeutic agent hydroxyurea.

Dissociative electron attachment to hydroxyurea was studied in the gas phase for electron energies ranging from zero to 9 eV in order to probe its radiosensitizing capabilities. The experiments were carried out using a hemispherical electron monochromator coupled with a quadrupole mass spectrometer. Diversified fragmentation of hydroxyurea was observed upon low energy electron attachment and here we highlight the major dissociation channels. Moreover, thermodynamic thresholds for various fragmentation reactions are reported to support the discussion of the experimental findings. The dominant dissociation channel, which was observed over a broad range of energies, is associated with formation of NCO(-), water, and the amidogen (NH2) radical. The second and third most dominant dissociation channels are associated with formation of NCNH(-) and NHCONH2 (-), respectively, which are both directly related to formation of the highly reactive hydroxyl radical. Other ions observed with significant abundance in the mass spectra were NH2 (-)/O(-), OH(-), CN(-), HNOH(-), NCONH2 (-), and ONHCONH2 (-).

Electron ionization of different large perfluoroethers embedded in ultracold helium droplets: effective freezing of short-lived decomposition intermediates.

RATIONALE: Electron ionization of three perfluoroethers (PFEs), C(6)F(14)O(3), C(8)F(18)O(4), and C(10)F(20)O(5), is studied in the gas phase and when the molecules are embedded in ultracold helium (He) droplets. The molecules investigated are model compounds for perfluoropolyethers used as lubricants in technical applications. The present study gives insight into possible radiolysis pathways upon radiation exposure. METHODS: The experiments utilized a crossed electron/droplet beam apparatus consisting of a He droplet source and pick-up chamber combined with a commercial time-of-flight mass spectrometer. The doped droplets were ionized by electron ionization at 70 eV. RESULTS: The He environment strongly affects the ionization patterns in the way that both the molecular ion M(+) and high-mass fragment ions formed by the loss of light neutral species such as F([M-F](+)), or CF(3)OCF(2) ([M-CF(3)OCF(2)](+)), etc., became strong signals in the mass spectrum. These signals were not or only barely visible in the gas-phase experiment and were identified as short lived (< µs) dissociation intermediates which in the gas phase immediately decomposed into lower-mass fragment ions. CONCLUSIONS: Ionic fragmentation intermediates are frozen and subsequently stabilized in the He environment. Helium droplets can hence be viewed as a cryogenic laboratory transforming short-lived decomposition intermediates into stable fragment ions appearing as strong signals in the mass spectrum.

The three-dimensional morphometry of the odontoid peg and its impact on ventral screw osteosynthesis.

Ventral screw osteosynthesis is a common surgical method for treating fractures of the odontoid peg, but there is still no consensus about the number and diameter of the screws to be used. The purpose of this study was to develop a more accurate measurement technique for the morphometry of the odontoid peg (dens axis) and to provide a recommendation for ventral screw osteosynthesis. Images of the cervical spine of 44 Caucasian patients, taken with a 64-line CT scanner, were evaluated using the measuring software MIMICS. All measurements were performed by two independent observers. Intraclass correlation coefficients were used to measure inter-rater variability. The mean length of the odontoid peg was 39.76 mm (SD 2.68). The mean screw entry angle α was 59.45° (SD 3.45). The mean angle between the screw and the ventral border of C2 was 13.18° (SD 2.70), the maximum possible mean converging angle of two screws was 20.35° (SD 3.24). The measurements were obtained at the level of 66% of the total odontoid peg length and showed mean values of 8.36 mm (SD 0.84) for the inner diameter in the sagittal plane and 7.35 mm (SD 0.97) in the coronal plane. The mean outer diameter of the odontoid peg was 12.88 mm (SD 0.91) in the sagittal plane and 11.77 mm (SD 1.09) in the coronal plane. The results measured at the level of 90% of the total odontoid peg length were a mean of 6.12 mm (SD 1.14) for the sagittal inner diameter and 5.50 mm (SD 1.05) for the coronal inner diameter. The mean outer diameter of the odontoid peg was 11.10 mm (SD 1.0) in the sagittal plane and 10.00 mm (SD 1.07) in the coronal plane. In order to calculate the necessary screw length using 3.5 mm cannulated screws, 1.5 mm should be added to the measured odontoid peg length when anatomical reduction seems possible. The cross-section of the odontoid peg is not circular but slightly elliptical, with a 10% greater diameter in the sagittal plane. In the majority of cases (70.5%) the odontoid peg offers enough room for two 3.5 mm cannulated cortical screws.

Promontory of radius: a new anatomical description on the distal radius.

Surgical treatment of distal radius fractures with palmar plates has gained popularity as the preferred approach to achieve anatomical fracture reposition. One hundred and thirty four radii of human cadavers were examined to elucidate the anatomy of the distal radius, especially the transition of the anterior into the lateral surface and a new term was given: promontory of radius. The promontory was located on the lateral surface between the changing of the convex to the concave curvature and the base of the styloid process. The anterior surface increased gradually from the ulnar notch to the lateral surface and formed the "base" of the promontory. The length of the promontory on the lateral surface measured 14-28 mm (mean 20.766 mm, SD 2.69 mm). The width of the promontory was found in between 10 and 27 mm (mean 13.857 mm, SD 2.14 mm). The width of the distal radius was 16-38 mm (mean 31.015 mm, SD 3.26 mm) and did not show any statistical correlation to the promontory. On the anterior surface the minimal width of promontory measured 4.9 mm, the maximal one 17.9 mm (mean 8.95 mm, SD 3.60). The height of the promontory on the anterior surface ranged in between 1.2 and 4.3 mm (mean 2.90 mm, SD 1.05 mm). The promontory of radius must be kept in mind to avoid any dorsal dislocation of the radial fragment often described as complication of intraarticular fractures. Based on this anatomical survey the data can be used for a new palmar radius plate designs.