Bone functions and the requirements for bone grafts and substitutes in the orofacial region

Bone is the largest calcium storage, has distinctive plasticity and adaptability and is part of the supporting tissue. An adequate composition is thus necessary. The bone matrix consists of organic and anorganic structures. Osteoblasts, osteoclasts and osteocytes are responsible for bone formation, resorption and metabolism. The periosteum, endosteum and bone tissue are a functional unit and provide protection, nutrition and growth. Bone is subject to continuous remodelling

Wound management after the application of bone grafting substitutes in the orofacial region

Surgical dressing after the application of bone grafting material depends on the type and size of the defect. A complete and tension-free wound closure has proved to be successful. In this context the infection problem needs special attention. Bone graft substitutes with an adequate surface structure, porosity and chemical properties, in combination with sufficient blood circulation, hold osteoconductive potential. They serve as a guide rail for the osteoblast-induced formation of new bone tissue, which at best may lead to complete replacement of the grafting material

Critical considerations on the diagnostic appraisal, adaptation and remodelling of bone graft substitutes

The diagnostic assessment of skeletal defects has a long-standing tradition. As a result of the development of new bone grafting materials, the demands on diagnostic assessment have also increased. The mode and quality of diagnostic appraisal are crucial to further clinical use and outcome prediction. Alongside traditional clinical and biological techniques, molecular biological methods have gained a broad scope of application and will be used even more frequently in the future

Uncoupled excitons in semiconductor microcavities detected in resonant Raman scattering

We present an outgoing resonant Raman-scattering study of a GaAs/AlGaAs based microcavity embedded in a p-i-n junction. The p-i-n junction allows the vertical electric field to be varied, permitting control of exciton-photon detuning and quenching of photoluminescence which otherwise obscures the inelastic light scattering signals. Peaks corresponding to the upper and lower polariton branches are observed in the resonant Raman cross sections, along with a third peak at the energy of uncoupled excitons. This third peak, attributed to disorder activated Raman scattering, provides clear evidence for the existence of uncoupled exciton reservoir states in microcavities in the strong-coupling regime

Spintronics: Fundamentals and applications

Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics.Comment: invited review, 36 figures, 900+ references; minor stylistic changes from the published versio

Studies on gap modes and localized modes due to BO2-, N3-, OCN-, SCN-, and SeCN- centres in KI

We have studied gap modes and localized modes above the optical band due to a series of three-atomic linear centres (BO-2, N-3, OCN -, SCN-, SeCN-) in KI by Raman scattering and by vibrational sideband absorption in the middle infra-red We compare our results with previous investigations of far infra-red absorption. A set of three gap modes (A2u ⊕ Eu ⊕ Eg or A u ⊕ 2 E) is established for each centre by experiment — according to group theory. The frequency behaviour within the series of centres is discussed by a linear model. This model explains also the appearance of up to four transverse (E) localized modes which are ascertained by experiment The comparison of sideband absorption and Raman scattering spectra shows that both phenomena obey the same selection and intensity rules. These rules can be deduced theoretically by the Wigner-Eckart theorem and are physically interpreted.Nous avons étudié, par diffusion Raman et par absorption des bandes latérales vibrationnelles dans l'infrarouge moyen, les modes de gap et les modes localisés au-dessus de la bande optique, modes dûs à une série de centres triatomiques linéaires (BO-2, N-3, OCN -, SCN-, SeCN-) dans KI. Nous comparons nos résultats avec des mesures précédentes de l'absorption dans l'infrarouge lointain. Un ensemble de trois modes de gap (A2u ⊕ Eu ⊕ Eg ou A1 ⊕ 2 E) est établi par l'expérience pour chaque centre — en accord avec la théorie des groupes. Pour cette série de centres le comportement en fréquence est discuté par un modèle linéaire. Ce modèle explique aussi l'apparition, au maximum, de quatre modes localisés transversaux (E), ce que nous avons pu vérifier par l' expérience. La comparaison des spectres d'absorption des bandes latérales et des spectres de diffusion Raman démontre que ces deux phénomènes obéissent aux mêmes règles de sélection et d'intensité. Ces règles peuvent être déduites théoriquement par le théorème de Wigner-Eckart et interprétées physiquement

Resonance Raman scattering in GaAs-Al<SUB>x</SUB>Ga<SUB>1-x</SUB>As superlattices: impurity-induced Fröhlich-interaction scattering

We report measurements of Raman scattering from LO phonons in resonance with quasi-two-dimensional excitons in a 104-A GaAs-125-A Al<SUB>0.25</SUB>Ga<SUB>0.75</SUB>As superlattice. Incoming and outgoing resonances are observed at discrete excitons formed from first and second conduction and valence subbands. As already pointed out by Zucker et al., the resonant Raman profile shows a stronger outgoing resonance as compared with the incoming one. We present a quantitative explanation of the observed asymmetry of both resonance channels by invoking the impurity-induced intraband Fr&#246;hlich scattering mechanism, an effect also observed in bulk semiconductors. This analysis differs from that of Zucker et al., which was based on the details of the quantized quasi-two-dimensional excitons. We believe that the latter mechanism may explain resonance asymmetry for a special range of superlattice parameters, while the one proposed here should be more general, extending all the way to the two-dimensional case