Helicity Amplitudes for Charmonium Production in Hadron-Hadron and Photon-Hadron Collisions

We present the gluon-gluon and photon-gluon helicity amplitudes for color singlet and octet charmonium production in polarized and unpolarized hadron-hadron and photon-hadron collisions.Comment: 11 pages amstex no figure

Mesoscopic order and the dimentionality of long-range resonance energy transfer in supramolecular semiconductors

We present time-resolved photoluminescence measurements on two series of oligo-p-phenylenevinylene materials that self-assemble into supramolecular nanostructures with thermotropic reversibility in dodecane. One set of derivatives form chiral, helical stacks while the second set form less organised, frustrated stacks. Here we study the effects of supramolecular organisation on the resonance energy transfer rates. We measure these rates in nanoassemblies formed with mixed blends of oligomers and compare them with the rates predicted by Foerster theory. Our results and analysis show that control of supramolecular order in the nanometre lengthscale has a dominant effect on the efficiency and dimentionality of resonance energy transfer.Comment: 17 Pages, 5 Figures, Submitted to J. Chem. Phy

Anharmonic magnetic deformation of self-assembled molecular nanocapsules

High magnetic fields were used to deform spherical nanocapsules, self-assembled from bola-amphiphilic sexithiophene molecules. At low fields the deformation -- measured through linear birefringence -- scales quadratically with the capsule radius and with the magnetic field strength. These data confirm a long standing theoretical prediction (W. Helfrich, Phys. Lett. {\bf 43A}, 409 (1973)), and permits the determination of the bending rigidity of the capsules as (2.6$\pm$0.8)$\times 10^{-21}$ J. At high fields, an enhanced rigidity is found which cannot be explained within the Helfrich model. We propose a complete form of the free energy functional that accounts for this behaviour, and allows discussion of the formation and stability of nanocapsules in solution.Comment: 4 pages, 3 figures, accepted in Phys. Rev. Let

Can Polymer Coils be modeled as "Soft Colloids"?

We map dilute or semi-dilute solutions of non-intersecting polymer chains onto a fluid of ``soft'' particles interacting via a concentration dependent effective pair potential, by inverting the pair distribution function of the centers of mass of the initial polymer chains. A similar inversion is used to derive an effective wall-polymer potential; these potentials are combined to successfully reproduce the calculated exact depletion interaction induced by non-intersecting polymers between two walls. The mapping opens up the possibility of large-scale simulations of polymer solutions in complex geometries.Comment: 4 pages, 3 figures ReVTeX[epsfig,multicol,amssymb] references update

The development of a questionnaire on metacognition for students in higher education

Background Interest in the role of metacognition has been steadily rising in most forms of education. This study focuses on the construction of a questionnaire for measuring metacognitive knowledge, metacognitive regulation and metacognitive responsiveness among students in higher education and the subsequent process of testing to determine its validity. Purpose The aim of the study was to construct an original instrument for measuring features of metacognition, henceforth referred to as the Awareness of Independent Learning Inventory (AILI), and further to establish the similarities and differences between this model and existing instruments for measuring metacognition. Sample The AILI questionnaire was distributed to 1058 students in various types of Teacher Training Institutes in the Netherlands and Belgium. The abridged English version of the questionnaire was administered to another sample of 729 students reading Economics and Business Administration at the University of Maastricht in the south of the Netherlands. Design and methods The AILI instrument was constructed on the basis of a facet design along two dimensions: components of metacognition and topics of concern to students in higher education. The data gathered with the instrument was analyzed by means of a generalisability study and a decision study, respectively. The validity of the instrument was investigated by using confirmatory factor analysis. Results The generalisability study showed that the reliability of the instrument was satisfactory. The decision study revealed that the number of items included in the questionnaire could be reduced substantially by leaving out two components of one of the dimensions in the facet design, without losing too much generalisability. The validity study showed that there was a considerable level of congruity between parts of the AILI questionnaire and the relevant parts of the Motivated Strategies for Learning Questionnaire (MSLQ). Conclusions The AILI questionnaire is a reliable and valid instrument for measuring metacognitive knowledge, regulation and responsiveness. It is suitable for use in the evaluation of the effects of interventions that purport to increase metacognitive knowledge, regulation and responsiveness of students in higher education

Planned dose of intensity modulated proton beam therapy versus volumetric modulated arch therapy to tooth-bearing regions

Background: Intensity modulated proton beam therapy (IMPT) for head and neck cancer offers dosimetric benefits for the organs at risk when compared to photon-based volumetric modulated arch therapy (VMAT). However, limited data exists about the potential benefits of IMPT for tooth-bearing regions. The aim of this study was to compare the IMPT and VMAT radiation dosimetrics of the tooth-bearing regions in head and neck cancer patients. Also, we aimed to identify prognostic factors for a cumulative radiation dose of ≥40 Gy on the tooth-bearing areas, which is considered the threshold dose for prophylactic dental extractions. Methods: A total of 121 head and neck cancer patients were included in this retrospective analysis of prospectively collected data. We compared the average Dmean values of IMPT versus VMAT of multiple tooth-bearing regions in the same patients. Multivariate logistic regression analysis was performed for receiving a cumulative radiation dose of ≥40 Gy to the tooth-bearing regions (primary endpoint) in both VMAT and IMPT. Results: A lower Dmean was seen after applying IMPT to the tooth-bearing tumour regions (p &lt; 0.001). Regarding VMAT, oral cavity tumours, T3-T4 tumours, molar regions in the mandible, and regions ipsilateral to the tumour were risk factors for receiving a cumulative radiation dose of ≥40 Gy. Conclusions: IMPT significantly reduces the radiation dose to the tooth-bearing regions.</p

Inter- and intraobserver reproducibility of buccal bone measurements at dental implants with cone beam computed tomography in the esthetic region

BACKGROUND: Sufficient buccal bone is important for optimal esthetic results of implant treatment in the anterior region. It can be measured with cone beam computed tomography (CBCT), but background scattering and problems with standardization of the measurements are encountered. The aim was to develop a method for reliable, reproducible measurements on CBCTs. METHODS: Using a new method, buccal bone thickness was measured on ten CBCTs at six positions along the implant axis. Inter- and intraobserver reproducibility was assessed by repeated measurements by two examiners. RESULTS: Mean buccal bone thickness measured by observers 1 and 2 was 2.42 mm (sd: 0.50) and 2.41 mm (sd: 0.47), respectively. Interobserver intraclass correlation coefficient was 0.96 (95% CI 0.93 to 0.98). The mean buccal bone thickness of the first measurement and the second measurement of observer 1 was 2.42 mm (sd: 0.50) and 2.53 mm (sd: 0.49), respectively, with an intraobserver intraclass correlation coefficient of 0.93 (95% CI 0.88 to 0.96). The mean buccal bone thickness of the first measurement and the second measurement of observer 2 was 2.41 mm (sd: 0.47) and 2.52 mm (sd: 0.47), respectively, with an intraobserver intraclass correlation coefficient of 0.96 (95% CI 0.93 to 0.97). CONCLUSIONS: Applying the methods used in this study, CBCTs are suitable for reliable and reproducible measurements of buccal bone thickness at implants

Buccal bone thickness at dental implants in the maxillary anterior region with large bony defects at time of immediate implant placement:A 1-year cohort study

Background There is lack of studies regarding preservation and possible changes in BBT at dental implants. Purpose To assess, on cone beam computer tomograms, the presence of bone at the time of tooth extraction in the maxillary esthetic region and the mean buccal bone thickness 1 month and 1 year after final restoration placement in patients with large bony defects. Material and Methods In a cohort study, patients were selected presenting a failing tooth with a large bony defect (test group [n = 20]: large bony defect, immediate placed implant and delayed provisionalization). Results were compared with a group in which patients presented a failing tooth without or with a small bony defect: (control group [n = 20]: without or small bony defect, immediate placed implant and delayed provisionalization). Cone beam computer tomograms were made preoperatively, and 1 month and 1 year after placement of the restoration, and buccal bone thickness was analyzed. Results In both groups approximately 1 mm of buccal bone thickness was present after 1 month and 1 year, without a significant difference between the groups. Conclusion In patients with large bony defects at a failing tooth it was possible to create a bone layer buccally of the implant and this bone layer remained stable during a 1-year follow-up; there were no significant differences between thickness of buccal bone at 1 month and 1 year in patients with large buccal bony defects and patients without or with small bony defects

Volumetric rheology of polymers

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