It is shown that the Kerr rotation of spin-polarized electrons is modulated by the distance of the electrons from the sample surface. Time-resolved Kerr rotation of optically excited spin-polarized ...electrons in the depletion layer of n-doped GaAs displays fast oscillations that originate from interference between the light reflected from the semiconductor surface and from the front of the electron distribution moving into the semiconductor. Using this effect, the dynamics of the photogenerated charge carriers in the depletion layer of the biased Schottky barrier is measured.
Dacryocystorhinostomy allows by-passing saccal and post-saccal stenoses and has traditionally been performed via an external approach, namely, external dacryocystorhinostomy. Over the past two ...decades, advances in endoscopic equipment have led to the widespread use of the endoscopic transnasal approach to the lacrimal pathway. A retrospective evaluation has been made of personal success rates in endoscopic dacryocystorhinostomy without stenting in 56 patients (15 male, 41 female) treated for nasolacrimal duct obstruction (48 unilateral, 8 bilateral). Of these, 53 were primary endoscopic dacryocystorhinostomy and 11 procedures were revisions of external dacryocystorhinostomy. A total of 64 endoscopic dacryocystorhinostomies were performed. Mean follow-up was 37.3 months (range 12-84 months). The success of surgery was defined by resolution of signs (epiphora and dacryocystitis) and objectively by endoscopic evaluation of the rhinostomy on routine follow-up. Results from patients undergoing primary endoscopic dacryocystorhinostomy were better than those for revision of external dacryocystorhinostomy with overall anatomical and functional results of 94.3% and 90.9%, in our series. The present study confirms that endoscopic dacryocystorhinostomy without stenting is effective for the treatment of nasolacrimal duct obstruction. The endoscopic approach allows simultaneous treatment of associated anatomic anomalies and sino-nasal disorders. Results obtained confirm that a functionally patent dacryocystorhinostomy can be achieved without the need for routine nasolacrimal stenting..
We used (31)P and (13)C solid-state nuclear magnetic resonance (NMR) spectroscopy to detect and analyze the major organic and inorganic components (collagen type I and bioapatite) in natural rabbit ...bone and beta-tricalcium phosphate implants loaded with osteogenically differentiated mesenchymal stem cells. High-resolution solid-state NMR spectra were obtained using the magic-angle spinning (MAS) technique. The (31)P NMR spectra of bone specimens showed a single line characteristic of bone calcium phosphate. (13)C cross-polarization (CP) MAS NMR spectra of bone exhibited the characteristic signatures of collagen type I with good resolution for all major amino acids in collagen. Quantitative measurements of (13)C-(1)H dipolar couplings indicated that the collagen segments are very rigid, undergoing only small amplitude fluctuations with correlation times in the nanosecond range. In contrast, directly polarized (13)C MAS NMR spectra of rabbit bone were dominated by signals of highly mobile triglycerides. These quantitative investigations of natural bone may provide the basis for a quality control of various osteoinductive bone substitutes. We studied the formation of extracellular bone matrix in artificial mesenchymal stem cell-loaded beta-tricalcium phosphate matrices that were implanted into the femoral condyle of rabbits. The NMR spectra of these bone grafts were acquired 3 months after implantation. In the (31)P NMR spectra, beta-tricalcium phosphate and bone calcium phosphate could be distinguished quantitatively, allowing recording of the formation of the natural bone matrix. Further, (13)C CPMAS allowed detection of collagen type I that had been produced in the implants. Comparison with the spectroscopic data from natural bone allowed assessment of the quality of the bone substitute material.
A computer algorithm for optimal voltage control with voltage regulators, suitable for large radial distribution networks is given in this paper. An objective function concerning the total cost of ...the voltage regulators (investment and maintenance cost) as well as the cost of losses of the examined networks is developed and constitutes the base of the algorithm. This algorithm makes the initial selection, installation and tap setting of the voltage regulators, which provide a smooth voltage profile along the network, utilizing former algorithms suitably modified and optimized. Then it attempts to minimize the number of the initially selected voltage regulators as much as possible, by moving them in such a way as to control the network voltage at the minimum possible cost (maximization of the objective function). The algorithm is fast, efficient and reliable as its application to practical distribution networks shows.
Dislocation is the second most frequently encountered complication in primary total hip arthroplasty (THA) and occurs more commonly in the early postoperative rehabilitation phase. Sir Charnley ...recommended the "avoidance of resection of the capsule" and emphasised its contribution to hip joint stability in THA. Several authors, however, doubted its significance and considered resection of the capsule to be essential. Since 2002, some surgeons increasingly adopted a modified, less invasive technique of THA via Bauer approach, including the preservation and repair of the hip joint capsule with focus on maintaining its acetabular origin. Another group of surgeons applied the traditional technique including the resection of the joint capsule via an anterolateral approach. In this case-control study we investigated whether the dislocation rate can be reduced through joint capsule reconstruction and whether any negative impact on patient satisfaction, functional results or revision rate is observed.
All cases of primary THA performed in our institution in a timeframe between 2002 and 2009 were included with the only exceptions of resurfacing arthroplasty, dual mobility and tumour hip replacements. Joint capsule repair cases were gathered in the study group (SG), capsule resection cases in the control group (CG). Additional patient-related data were taken from the anaesthesia records. The WOMAC score and a questionnaire focusing on detection of dislocations and revision surgeries was sent out for each case. Further targeted research was conducted that included requesting records and reports from external hospitals. In the case of non-responding patients, all available data (operating room documentation, electronic files, archive, X-rays) were reviewed for incidents of dislocation and revision surgery. Groupings and classifications were exclusively performed by senior surgeons. SG and CG were compared regarding epidemiologic, implant-associated and surgery-specific data. Statistical evaluations were performed using the Chi-squared test and the Mann-Whitney U test.
1972 cases of primary THA were included: 992 in the SG and 980 in the CG. The follow-up rates were 92.7 % in the SG and 76.4 % in the CG, the mean follow-up times 33.5 months and 73.4 months, respectively, with a follow-up of at least 12 months in all cases. In the SG, the dislocation rate was 0.3 % (n = 3) and thus significantly lower than the 2.55 % in the CG (n = 25, p < 0.001). Both the WOMAC score (SG: 1.46 ± 1.73; CG: 1.53 ± 1.80; p > 0.05) and the revision rate (SG: 5.24 %; CG: 6.84 %; p = 0.139) showed no significant differences.
Preservation and repair of the hip joint capsule causes an 88-%-reduction of the dislocation rate in primary THA in this large series including 1972 cases, operated via the Bauer or the anterolateral approach. Several authors reported comparable results after THA using similar techniques of soft tissue and capsular repair through the posterior or posterolateral approach. Sparing and reconstructing the hip joint capsule therefore seems to reduce the dislocation rate after primary THA by one order of magnitude regardless of the surgical approach and, especially, if the acetabular origin is preserved. Capsule-related specific complications such as an increased revision rate, malfunction or pain were neither recorded in our study nor by others. Thus, careful preservation and reconstruction of the hip joint capsule may be expressly recommended in primary THA.
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