391 research outputs found
Generating Correlated Ordinal Random Values
Ordinal variables appear in many field of statistical research. Since working with simulated data is an accepted technique to improve models or test results there is a need for providing correlated ordinal random values with certain properties like marginal distribution and correlation structure. The present paper describes two methods for generating such values: binary conversion and a mean mapping approach. The algorithms of the two methods are described and some examples of the outcomes are shown
Statistischer Überblick der türkischen Migration in Baden-Württemberg und Deutschland
Diese Arbeit stellt die Eckdaten der türkischen Migration nach Deutschland zusammen. Das erste Kapitel beleuchtet die historischen Meilensteine der Integration, vom Anwerbungsabkommen am 31. Oktober 1961, über das Rückkehrförderungsgesetz 1983 und dem Einbürgerungsgesetz aus dem Jahr 2000. Das zweite Kapitel fasst wesentliche Daten und Fakten über die türkischen Einwanderer in Deutschland - im Vergleich auch zu anderen Migrantengruppen ? zusammen; unter anderem werden dabei Altersstruktur, Bildung und Einbindung in den Arbeitsmarkt analysiert. Im dritten Kapitel wird der Fall Baden-Württemberg näher dargestellt, im vierten kurz auf die Stadt Stuttgart eingegangen. Abschließend werden die positiven und negativen Tendenzen, basierend auf dem zugrundeliegenden Datenmaterial, noch einmal zusammengefasst. Einerseits wird die positive Tendenz vom Gastarbeiter zum Bürger deutlich, andererseits decken die Zahlen nach wie vor bestehende Schwächen deutlich auf. Diese Arbeit soll einen Beitrag dazu leisten, die Vielzahl unterschiedlicher Statistiken zum Thema Deutsch-Türkische Migration prägnant zusammenzufassen und anschaulich darzustellen
Hyperon-nucleon three-body forces and strangeness in neutron stars
Three-body forces acting on a hyperon in a nuclear medium are
investigated, with special focus on the so-called hyperon puzzle in neutron
stars. The hyperon-nucleon two-body interaction deduced from SU(3) chiral
effective field theory is employed at next-to-leading order. Hyperon-nucleon
three-body forces are approximated using saturation by decuplet baryons and are
transcribed to density-dependent effective two-body interactions. These
together are taken as input in a Brueckner-Bethe-Goldstone equation with
explicit treatment of the and coupled channels. Single-particle potentials of a
hyperon in symmetric nuclear matter and neutron matter are
calculated. With parameters of the three-body force constrained by
hypernuclear phenomenology, extrapolations to high baryon density are
performed. By comparison of the and neutron chemical potentials at
densities characteristic of the core of neutron stars it is found that the
combined repulsive effects of two- and three-body correlations makes the
appearance of hyperons in neutron stars energetically unfavourable,
thus offering a possible solution to a longstanding question
Shape-specific characterization of colorectal adenoma growth and transition to cancer with stochastic cell-based models
Colorectal adenoma are precursor lesions on the pathway to cancer. Their removal in screening colonoscopies has markedly reduced rates of cancer incidence and death. Generic models of adenoma growth and transition to cancer can guide the implementation of screening strategies. But adenoma shape has rarely featured as a relevant risk factor. Against this backdrop we aim to demonstrate that shape influences growth dynamics and cancer risk. Stochastic cell-based models are applied to a data set of 197,347 Bavarian outpatients who had colonoscopies from 2006-2009, 50,649 patients were reported with adenoma and 296 patients had cancer. For multi-stage clonal expansion (MSCE) models with up to three initiating stages parameters were estimated by fits to data sets of all shapes combined, and of sessile (70% of all adenoma), peduncular (17%) and flat (13%) adenoma separately for both sexes. Pertinent features of adenoma growth present themselves in contrast to previous assumptions. Stem cells with initial molecular changes residing in early adenoma predominantly multiply within two-dimensional structures such as crypts. For these cells mutation and division rates decrease with age. The absolute number of initiated cells in an adenoma of size 1 cm is small around 10(3), related to all bulk cells they constitute a share of about 10(−5). The notion of very few proliferating stem cells with age-decreasing division rates is supported by cell marker experiments. The probability for adenoma transiting to cancer increases with squared linear size and shows a shape dependence. Compared to peduncular and flat adenoma, it is twice as high for sessile adenoma of the same size. We present a simple mathematical expression for the hazard ratio of interval cancers which provides a mechanistic understanding of this important quality indicator. We conclude that adenoma shape deserves closer consideration in screening strategies and as risk factor for transition to cancer
Gluteus maximus tendon transfer as a salvage option for painful chronic hip abductor insufficiency: clinical and MRI results with a minimum follow-up of 24 months
INTRODUCTION: Chronic hip abductor insufficiency is a rare debilitating condition. In cases refractory to conservative treatment and not amenable to direct repair an augmentation becomes necessary. The preferred salvage method at our institution is augmentation with the anterior third of the gluteus maximus tendon. The aim of this study is to describe the results of 8 patients, treated for painful chronic hip abductor insufficiency with gluteus maximus muscle transfer, after a minimal follow-up of 24 months including a full clinical and MRI evaluation of the hip abductors pre- and postoperatively.
METHODS: We retrospectively reviewed a consecutive series of 8 patients who were surgically managed for painful chronic hip abductor insufficiency. All patients had a Trendelenburg sign, impaired muscle strength (M ⩽ 3) as well as a complete avulsion of the hip abductors with marked fatty degeneration (⩾3). Pain levels, muscle strength, functional scores as well as a postoperative MRI was obtained after a minimal follow-up of 24 months.
RESULTS: The mean age of the patients was 69 years, mean follow-up was 35 (26-54) months. Pain was significantly reduced postoperatively to VAS 2.5 from VAS 5 (p = 0.046). Trendelenburg sign remained positive in all patients and hip abductor strength did not improve significantly from 2.4 to 3.1 (p = 0.19). Complete healing of the transferred tendon was confirmed by MRI in all patients at last follow-up.
CONCLUSIONS: In the setting of painful chronic hip abductor insufficiency refractory to conservative treatment with advanced muscle degeneration without the possibility of a direct reconstruction the gluteus maximus tendon transfer significantly decreased pain. The effect on hip abductor strength and patient-reported functional outcome scores is limited. Despite the modest results it remains our preferred salvage treatment option for lack of better alternatives. Larger studies are necessary to confirm these findings
Combining the advantages of 3-D and 2-D templating of total hip arthroplasty using a new tin-filtered ultra-low-dose CT of the hip with comparable radiation dose to conventional radiographs
BACKGROUND
Inaccurately scaled radiographs for total hip arthroplasty (THA) templating are a source of error not recognizable to the surgeon and may lead to inaccurate reconstruction and thus revision surgery or litigation. Planning based on computed tomography (CT) scans is more accurate but associated with higher radiation exposure. The aim of this study was (1) to retrospectively assess the scaling deviation of pelvic radiographs; (2) to prospectively assess the feasibility and the radiation dose of THA templating on radiograph-like images reconstructed from a tin-filtered ultra-low-dose CT dataset.
METHODS
120 consecutive patients were retrospectively analyzed to assess the magnification error of our current THA templates. 27 consecutive patients were prospectively enrolled and a radiographic work-up in the supine position including a new tin-filtered ultra-low-dose CT scan protocol was obtained. THA was templated on both images. Radiation dose was calculated.
RESULTS
Scaling deviations between preoperative radiographs and CT of ≥ 5% were seen in 25% of the 120 retrospectively analyzed patients. Between the two templates trochanter tip distance differed significantly (Δ2.4 mm, 0-7 mm, p = 0.035)), predicted femoral shaft size/cup size was the same in 45%/41%. The radiation dose of the CT (0.58 mSv, range 0.53-0.64) was remarkably low.
CONCLUSION
Scaling deviations of pelvic radiographs for templating THA may lead to planning errors of ≥ 3 mm in 25% and ≥ 6 mm in 2% of the patients. 2-D templating on radiograph-like images based on tin-filtered ultra-low-dose CT eliminates this source of error without increased radiation dose.
LEVEL OF EVIDENCE
Retrospective and prospective comparative study, Level III
Accuracy of pelvic measurements on virtual radiographic projections based on computed tomography scans compared to conventional radiographs pre- and postoperatively
BACKGROUND
The anteroposterior (ap) radiograph of the pelvis is decisive in the diagnosis of different pathologies of the hip joint. Technical advantages have reduced the radiation dose of pelvic CT to levels comparable to radiographs. The purpose of this study was to validate if standard radiographic parameters (lateral center edge angle, medial center edge angle, acetabular index, acetabular arc, extrusion index, crossover sign and posterior wall sign) can accurately be determined on radiograph-like projections reconstructed from the CT dataset pre- and postoperatively.
METHODS
A consecutive series of patient with symptomatic dysplasia of the hip and a full radiologic workup (radiographs and CT scan pre- and postoperatively) who underwent periacetabular osteotomy were included. Standard radiographic parameters were compared between radiographs and radiograph-like projections by two authors pre- and postoperatively.
RESULTS
A total of 16 hips (32 radiographs/32 radiograph-like projections) were included in the study. No significant difference was found between the radiographs and radiograph-like images for all parameter for both examiners. ICC between radiograph and radiograph-like projections for all investigated parameters showed good to excellent reliability (0.78-0.99) pre- and postoperatively.
CONCLUSION
Radiograph-like projections show comparable results to radiographs with regard to the important investigated parameters (lateral center edge angle, medial center edge angle, acetabular index, acetabular arc, extrusion index, crossover sign and posterior wall sign). Thus, ultra-low-dose CT scans may reduce the need for conventional radiographs in pre- and postoperative analyses of 3-dimensional hip pathologies in the future, as the advantages increasingly outweigh the disadvantages
Systematic Identification of Hazardous States and Approach for Condition Monitoring in the Context of Li-ion Battery Disassembly
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