InAs quantum-dot (QD) lasers were investigated in the temperature range 20-300 K and under hydrostatic pressure in the range of 0-12 kbar at room temperature. The results indicate that Auger recombination is very important in 1.3-m QD lasers at room temperature and it is, therefore, the possible cause of the relatively low characteristic temperature observed, of 0 = 41 K. In the 980-nm QD lasers where 0 = 110-130 K, radiative recombination dominates. The laser emission photon energy las increases linearly with pressure at 10.1 and 8.3 meV/kbar for 980 nm and 1.3m QD lasers, respectively. For the 980-nm QD lasers the threshold current increases with pressure at a rate proportional to the square of the photon energy 2 las . However, the threshold current of the 1.3m QD laser decreases by 26% over a 12-kbar pressure range. This demonstrates the presence of a nonradiative recombination contribution to the threshold current, which decreases with increasing pressure. The authors show that this nonradiative contribution is Auger recombination. The results are discussed in the framework of a theoretical model based on the electronic structure and radiative recombination calculations carried out using an 8 8 k p Hamiltonian.

The clinical application of cellular based therapies with ex vivo cultivation for the treatment of diseases of the musculoskeletal system has until now been limited. In particular, the advanced laboratory and technical effort necessary, regulatory issues as well as high costs are major obstacles. On the other hand, newly developed cell therapy systems permit intra-operative enrichment and application of mesenchymal and progenitor stem cells from bone marrow aspirate concentrate (BMAC) in one single operative session. The objective of the present clinical surveillance study was to evaluate new bone formation after the application of BMAC as well as to record any possible therapy-specific complicationsFor this purpose, the clinical-radiological progress of a total of 101 patients with various bone healing disturbances was documented (surveillance study). The study included 37 necrosis of the head of the femur, 32 avascular necroses/bone marrow edema of other localization, 12 non-unions, 20 other defects. The application of BMAC was performed in the presence of osteonecrosis via a local injection as part of a core decompression (n=72) or by the local adsorption of intra-operative cellular bone substitution material (scaffold) incubated with BMAC during osteosynthesis (n=17) or in further surgery (n=12).After an average of 14 months (2–24 months), the patients were re-examined clinically and radiologically and interviewed. Further surgery was necessary in 2 patients within the follow-up period. These were due to a progression of a collapsed head of the femur with initial necrosis in ARCO Stage III, as well as inadequate new bone formation with secondary loss of correction after periprosthetic femoral fracture. The latter healed after repeated osteosynthesis plus BMAC application without any consequences. Other than these 2 patients, no further complications were observed. In particular, no infections, no excessive new bone formation, no induction of tumor formation, as well as no morbidity due to the bone marrow aspiration from the iliac crest were seen.There were no specific complications within the short follow-up period and a simple intra-operative use of the system for different forms of bone loss could be demonstrated. In the authors' opinion, the on-site preparation of the bone marrow cells within the operating theater eliminates the specific risk of ex vivo cell proliferation and has a safety advantage in the use of autologous cell therapy for bone regeneration. Additional studies should be completed to determine efficacy.

Background: Proteorhodopsin (pR) is a light-activated proton pump homologous to bacteriorhodopsin and recently discovered in oceanic γ -proteobacteria. One perplexing difference between these two proteins is the absence in pR of homologues of bR residues Glu-194 and Glu-204. These two residues, along with Arg-82, have been implicated in light-activated fast H + release to the extracellular medium in bR. It is therefore uncertain that pR carries out its physiological activity using a mechanism that is completely homologous to that of bR.

Proteorhodopsin (pR) is a bacteriorhodopsin (bR) homologue, recently discovered in oceanic bacterioplankton, which functions as a light-driven proton pump. Resonance Raman spectra of pR excited with 532-nm light indicate that there are two subpopulations of pR within the sample solubilized in octylglucoside detergent and maintained in a light-adapted state in a spinning Raman cell. The subpopulations exhibit two distinct chromophore environments, as evidenced by two sets of split peaks, 1642/1655 cm -1 (corresponding to the Schiff base υ CdN vibration) and 1244/1252 cm -1 (corresponding to a retinylidene-lysine N-C-H rock). These populations most likely arise either from different post-translational modifications of the heterologously expressed protein or from a mixture of retinal isomers (all-trans and 13-cis) that was previously reported to be present in light-adapted pR in a 60:40 ratio. However, the latter possibility seems at odds with the resonance Raman fingerprint spectral patterns in both natural-abundance and 15-2 H-retinal-subsituted pR, which are consistent with an all-trans chromophore configuration similar to that of light-adapted bR.

Proteorhodopsin (pR) is a homologue of bacteriorhodopsin (bR) that has been recently discovered in oceanic bacterioplankton. Like bR, pR functions as a light-driven proton pump. As previously characterized by laser flash induced absorption spectroscopy (Krebs, R. A.; Alexiev, U.; Partha, R.; DeVita, A. M.; Braiman, M. S. BMC Physiol. 2002, 2, 5), the pR photocycle shows evidence of light-induced H(+) release on the 10-50 micros time scale, and of substantial accumulation of the M intermediate, only at pH values above 9 and after reconstitution into phospholipid followed by extensive washing to remove detergent. We have therefore measured the time-resolved FTIR difference spectra of pR intermediates reconstituted into DMPC vesicles at pH 9.5. A mixture of K- and L-like intermediates, characterized by a 1516 cm(-1) positive band and a 1742 cm(-1) negative band respectively, appears within 20 micros after photolysis. This mixture decays to an M-like state, with a clear band at 1756 cm(-1) due to protonation of Asp-97. The 50-70 micros rise of M at pH 9.5 is similar to (but a little slower than) the rise times for M formation and H(+) release that were reported earlier based on flash photolysis measurements of pR reconstituted into phospholipids with shorter acyl chains. We conclude that, at pH 9.5, H(+) release occurs while Asp-97 is still protonated; i.e., this aspartic acid cannot be the H(+) release group observed by flash photolysis under similar conditions.