Magneto-optic Kerr effect of strongly correlated electron compounds

The optical conductivity and the magneto-optic polar Kerr effect of RAl 2 (R = La, Ce, Pr), RFe2 (R = Y, Ce), RNi 2B2C (R = Tm, Yb), CeB6, and YbBiPt were measured between 1.4 and 5.4 eV using a rotating analyzer ellipsometer and a normal incidence Kerr spectrometer. Optical absorption of RAl2, RFe 2, and RNi2B2C shows metallic behavior. For the low carrier concentration metals CeB6 and YbBiPt the spectrum is dominated by interband transitions. Spectra of RAl2 and RFe 2 show absorption at 2 eV which is also found in heavier RFe2 compounds. This structure is attributed to R-derived transitions. At higher energy transitions are governed by Fe-derived states. Alloying CeFe2 with 10% Co leads to a magnetic instability with a low-temperature antiferromagnetic ground state. The metamagnetic transition to the field-induced ferromagnetic state was observed using the Kerr effect. We measured the Kerr rotation at 1.8 and 4 eV across this transition, which occurs between 35 and 40 kOe at 50 K. For the magnetic superconductor TmNi2B2C the transition from the superconducting to the normal state was found in the Kerr rotation. A critical field of 10 kOe was estimated, which is in excellent agreement with the value derived from magnetization data. CeB6 shows a peak in the Kerr effect, which coincides with the plasma edge at 2 eV. No such feature was found in YbBiPt. The plasma edge appears to be screened by interband transitions;We used the tight-binding linear muffin-tin orbital method to calculate the band structure and density of states. The spin magnetic moment obtained by the local density approximation (LDA) is generally in good agreement with experiment. The orbital moment of localized states is overestimated by LDA. For the more itinerant 4f states found in CeFe2 the magnetic moments predicted by LDA are close to the experimentally observed moments. The optical conductivity for LaAl2 and YFe2 agrees well with the one measured. LDA does not reproduce the conductivity for the other compounds, which we attribute to an inadequate treatment of the localized 4f states in the LDA. Spectra were analyzed using band structure plots which included the orbital character of the bands

Interpreting process data of wet pressing process: Part 1: Theoretical approach

The wet pressing process represents a new production method for carbon fibre-reinforced plastics components. Due to the low cycle times, it is suitable for use in the automotive industry. Therefore, a sufficient degree of industrialisation needs to be achieved, which is characterised by a stable process. The knowledge about relevant process parameters, their interactions, and influence on the part quality builds the basis of an economic process. This is a major challenge, since in the early stage of process development the available amount of recorded process data is small and the data sets are not complete. As the implementation of time-, material-, and cost-intensive experiments represents no acceptable alternative, a theoretical approach is chosen. This article describes a theoretical procedure to define the critical factors of the wet pressing process with significantly less resource input

Multivalvular Disease: Percutaneous Management in 2019 and Beyond

Patients with multivalvular disease (MVD) are common and often present with heterogeneous valve defects. Evaluation is complicated by interactions among various valve pathologies. Trials and guidelines focus primarily on single-valve disease, providing few recommendations for the treatment of patients with MVD. This article provides an insight into percutaneous treatment possibilities for this heterogeneous patient population

Impact of the indexed effective orifice area on mid-term cardiac-related mortality after aortic valve replacement

Background There has been ongoing controversy as to whether prosthesis-patient mismatch (PPM, defined as indexed effective orifice area (EOAI) <0.85 m(2)/cm(2)) influences mortality after aortic valve replacement (AVR). In most studies, PPM is anticipated by reference tables based on mean EOAs as opposed to individual assessment. These reference values may not reflect the actual in vivo EOAI and hence, the presence or absence of PPM may be based on false assumptions. Objective To assess the impact of small prosthesis EOA on survival after aortic valve replacement AVR. Methods 645 patients had undergone an AVR between 2000 and 2007 entered the study. All patients underwent transthoracic echocardiography for determination of the actual EOAI within 6 months postoperatively. In order to predict time from surgery to death a proportional hazards model for competing risks (cardiac death vs death from other causes) was used. EOAI was entered as a continuous variable. Results PPM occurred in 40% of the patients. After a median follow-up of 2.35 years, 92.1% of the patients were alive. The final Cox regression model showed a significantly increased risk for cardiac death among patients with a smaller EOAI (HR=0.32, p=0.022). The effect of EOAI on the 2-5 year mortality risk was demonstrated by risk plots. Conclusions In contrast to previous studies these EOAI values were obtained through postoperative echocardiography, substantially improving the accuracy of measurement, and the EOAI was modelled as a continuous variable. There was a significantly improved survival for larger EOAIs following AVR. Strategies to avoid PPM should become paramount during AVR

Impact of preoperative positron emission tomography in patients with severely impaired LV-function undergoing surgical revascularization

In patients with ischemic cardiomyopathy, coronary artery bypass grafting (CABG) offers an important therapeutic option but is still associated with high perioperative mortality. Although previous studies suggest a benefit from revascularization for patients with defined viability by a non-invasive technique, the role of viability assessment to determine suitability for revascularization in patients with ischemic cardiomyopathy has not yet been defined. This study evaluates the hypothesis that the use of PET imaging in the decision-making process for CABG will improve postoperative patient survival. We reviewed 476 patients with ischemic cardiomyopathy (LV ejection fraction ≤0.35) who were considered candidates for CABG between 1994 and 2004 on the basis of clinical presentation and angiographic data. In a Standard Care Group, 298 patients underwent CABG. In a second PET-assisted management group of 178 patients, 152 patients underwent CABG (PET-CABG) and 26 patients were excluded from CABG because of lack of viability (PET-Alternatives). Primary endpoint was postoperative survival. There were two in hospital deaths in the PET-CABG (1.3%) and 30 (10.1%) in the Standard Care Group (P = 0.018). The survival rate after 1, 5 and 9.3 years was 92.0, 73.3 and 54.2% in the PET-CABG and 88.9, 62.2 and 35.5% in the Standard Care Group, respectively (P = 0.005). Cox-regression analysis revealed a significant influence on long-term survival of patient selection by viability assessment via PET (P = 0.008), of LV-function (P = 0.017), and age >70 (P = 0.016). Preoperative assessment of myocardial viability via PET identifies patients, who will benefit most from CABG

Analyse komplexer biologischer Proben mittels oberflächenverstärkter Ramanspektroskopie (SERS)

Diese Studie beschäftigt sich mit dem Nachweis biologischer Proben mit Hilfe der Raman-Mikroskopie. Um ausreichende Signalintensitäten auch bei niedrigen Konzentrationen zu erhalten, wurde insbesondere der Effekt der oberflächenverstärkten Raman-Streuung (SERS) näher untersucht. Als Proben dienten DNA aus Hering-Sperma und das Protein Albumin. Zur Verstärkung des Raman-Spektrums wurden zwei unterschiedliche Methoden verwendet. Zum Einen wurden in einem chemischen Reduktionsprozess Nanosilberpartikel hergestellt und den biologischen Proben zugemischt. Zum Anderen wurden mit Hilfe laserangeregter periodischer Oberflächenstrukturierung (LIPSS) erzeugte nanostrukturierte Silberoberflächen als Substrate für die Proben verwendet. Diese Methode wurde bislang nicht für die SERS-Analyse biologischer Proben eingesetzt. Erste hier präsentierte Messungen zeigen, dass beide Verfahren signifikante SERS-Verstärkungen liefern und potentiell leistungsstarke Methoden für die zerstörungsfreie Analyse biologischer Proben darstellen