Cavitation in adhesives

The bubbles that usually appear in the bulk of an adhesive film during separation allow for a significant deformation of the adhesive material and are therefore an essential ingredient for a high dissipation. Recent observations have shown that they appear in the early stages of separation. The present model describes the early deformations induced in the film by the bubbles, and predicts how many will appear, depending on the separation velocity and on the number of weak points in the film. The trends we obtain are in agreement with observations.     

Ueber Untersuchung von Jodoform und Jod enthaltenden Verbandstoffen und Arzneimitteln

Ohne Zusammenfassung     

Middle School Students' Understanding of Number Sense Related to Percent

This study examined middle school students' understanding of percent, focusing on number sense. Participants in the study were 106 seventh-grade and 93 eighth-grade students. Students were given a written test that included 21 multiple-choice questions and an open-ended item. Research interviews were conducted with 28 selected students. Students performed better interpreting a quantity expressed as a percent given a pictorial continuous region than when a pictorial discrete set of circles was given. Students had difficulty interpreting a quantity expressed as a percent of a number. The strategies used by students to make comparisons about percents represent a wide range of correct and incorrect approaches to the questions. In addition to the use of 50% and 100% as common reference points, students successfully applied fractional relationships, estimation and mental computation to make comparisons. A variety of inappropriate strategies which included computational procedures and numerical comparisons were also employed, some of which resulted in the correct multiple-choice response.     

Ultrastructure, histochemistry, and mineralization patterns in the ecdysial suture of the blue crab, Callinectes sapidus.

The ecdysial suture is the region of the arthropod exoskeleton that splits to allow the animal to emerge during ecdysis. We examined the morphology and composition of the intermolt and premolt suture of the blue crab using light microscopy and scanning electron microscopy. The suture could not be identified by routine histological techniques; however 3 of 22 fluorescein isothiocyanate-labeled lectins tested (Lens culinaris agglutinin, Vicia faba agglutinin, and Pisum sativum agglutinin) differentiated the suture, binding more intensely to the suture exocuticle and less intensely to the suture endocuticle. Back-scattered electron (BSE) and secondary electron observations of fracture surfaces of intermolt cuticle showed less mineralized regions in the wedge-shaped suture as did BSE analysis of premolt and intermolt resin-embedded cuticle. The prism regions of the suture exocuticle were not calcified. X-ray microanalysis of both the endocuticle and exocuticle demonstrated that the suture was less calcified than the surrounding cuticle with significantly lower magnesium and phosphorus concentrations, potentially making its mineral more soluble. The presence or absence of a glycoprotein in the organic matrix, the extent and composition of the mineral deposited, and the thickness of the cuticle all likely contribute to the suture being removed by molting fluid, thereby ensuring successful ecdysis.     

Growth and oxidation of aluminum thin films deposited on Ag(1 1 1)

Auger electron spectroscopy (AES) and low energy electron diffraction (LEED) were used to study the first steps of growth and oxidation of aluminum on Ag(1 1 1) substrate. We find that the growth of aluminum at room temperature (RT) shows the formation of a complete monolayer (ML) in epitaxy with the substrate. After deposition at RT of one aluminum ML, the dissolution kinetics is recorded at 200 °C and the bulk diffusion coefficient is deduced. We also show that the oxidation at RT of one aluminum ML is very rapid, and that both aluminum and oxygen do not dissolve in silver up to 500 °C. From the AES intensities variations, we deduce the composition profile of the oxide layer which corresponds probably to the stacking …/Ag/Ag/Al/O.     

Collision induced transitions between Zeeman substates of laser excited sodium atoms in very high magnetic fields

This is a report on a new method of measuring cross sections for the collision induced population transfer between single Na — 3p ² P fine structure Zeeman states. The experiments are done for the five inert gases at the magnetic field strengths of 6, 17, 24, and 51 kOe. From the optically excited² P _3/2,±3/2 and² P _1/2,±1/2 states, respectively, the transfer to the other Zeeman states is studied. The method allows the determination of cross sections for which the influence of the magnetic field is cancelled and which render possible the calculation of cross sections for the transfer and the relaxation of all² P density tensor components of the degreek=1, 2, and 3. The comparison with previous theoretical and experimental results gives satisfactory agreement. As an application the six Grawert parameters are deduced for the inert gases.     

Division et extension dans l'algèbreA ∞ (Ω) d'un ouvert pseudo-convexe à bord lisse de ℂ n

Sans résumé     

Magnetization prepared rapid gradient-echo (MP-RAGE) MR imaging of the liver: comparison with spin-echo imaging.

We have implemented an MR technique that employs a rapid gradient echo sequence, preceded by magnetization preparation pulses to provide T1- and T2-weighted tissue contrast. With this technique, which can be identified as a member of a new family of pulse sequences, generically named Magnetization Prepared RApid Gradient Echo (MP-RAGE), very short repetition times are used, allowing acquisition times of less than one second and images virtually free of motion-induced artifacts during quiet respiration. Fifteen patients with known liver lesions (metastases, hemangiomas, and cysts) were examined using T1- and T2-weighted 2-dimensional MP-RAGE sequences, and the images were compared with conventional T1- and multi-echo T2-weighted spin-echo (SE) sequences. Signal difference-to-noise ratios (SD/Ns) of the lesions were calculated for all pulse sequences using corresponding axial images and were normalized for voxel volume. The mean normalized SD/Ns of the MP-RAGE sequences were generally comparable to those for the SE sequences. In addition, there were no noticeable respiratory artifacts on the MP-RAGE images whereas these were clearly present on the T2-weighted SE images and to a lesser degree on the T1-weighted SE images. It is concluded that the MP-RAGE technique could become an important method for evaluating the liver for focal disease.