Model for the low-temperature magnetic phases observed in doped YBa_2Cu_3O_{6+x}

A classical statistical model for the antiferromagnetic (AFM) ordering of the Cu-spins in the CuO_2 planes of reduced YBa_2Cu_3O_{6+x} type materials is presented. The magnetic phases considered are the experimentally observed high-temperature AFI phase with ordering vector Q_I=(1/2,1/2,0), and the low-temperature phases: AFII with Q_II=(1/2,1/2,1/2) and intermediate TA (Turn Angle) phases TAI, TAII and TAIII with components of both ordering vectors. It is shown that the AFII and TA phases result from an effective ferromagnetic (FM) type coupling mediated by free spins in the CuO_x basal plane. Good agreement with experimental data is obtained for realistic model parameters.Comment: 11 pages, 2 Postscript figures, Submitted to Phys.Rev.Let

Theory of Electromagnetic Wave Transmission through Metallic Gratings of Subwavelength Slits

We present FDTD calculations for transmission of light and other electromagnetic waves through periodic arrays of slits in a metallic slab. The results show resonant, frequency dependent, transmittance peaks for subwavelength widths of the slits which can be up to a factor of ten with respect to those out of resonance. Although our conclusions agree with previous work by Lezec and Thio as regards both the magnitude of the enhancement and the lack of contribution of surface plasmon polaritons of the metal surface to this effect, we derive an interpretation from a theory that deals with emerging beam- Rayleigh anomalies of the grating, and with Fabry-Perot resonances of the perforated slab considered as an effective medium.Comment: 12 pages 3 figure

Umweltgerechte Prozessführung und Zustandserkennung in Chemieanlagen mit neuronalen Netzen - Teilvorhaben 2: Konzipierung und Erprobung des Zustandserkennungsverfahrens

Im Rahmen des Teilvorhabens wurde ein Online-Monitoring-System für stark exotherme Reaktionen entwickelt, das das Bedienungspersonal bei der optimalen und umweltgerechten Prozessführung von komplexen oder sicherheitstechnisch schwierigen Semibatch-Prozessen in Rührkesselreaktoren (Batch-Reaktoren) unterstützen soll. Das Monitoring-System (MoSys) basiert auf dimensionslosen Stoff- und Wärmebilanzen mit adaptiven Komponenten. MoSys muss zuerst mit den Prozessdaten von normalen und unerwünschten Batch-Verläufen angelernt werden, die im Miniplant unter den Bedingungen des Industrieprozesses durchgeführt wurden. Die Adaption der Bilanzmodelle an die Zielanlage erfolgt durch zweischichtige Perceptron-Netze. Um eine vollständige Maßstabsübertragung zu gewährleisten, sollte MoSys mit Prozessdaten von mindestens einem normalen Batch-Verlauf in der Chemieanlage angepasst und validiert werden. MoSys wurde sowohl für eine homogene exotherme Veresterungsreaktion als auch für einen komplexen heterogenen exothermen Hydrierprozess konzipiert. Experimentelle Tests wurden für die Veresterung in einer Pilotanlage und für die Hydrierung in einer industriellen Chemieanlage durchgeführt. Zur Industrieerprobung wurde MoSys in ein Batch-Informations-Management-System (BIMS) integriert, das auch entwickelt und in das Prozessleitsystem (PLS) einer Mehrzweckanlage im Feinchemie-Werk Radebeul (Degussa AG) implementiert wurde. Dadurch konnten die MoSys-Ausgaben simultan mit wichtigen Prozesssignalen auf den Terminals des PLS visualisiert werden. Zum Beispiel werden der Hydrierungsfortschritt, das vorhergesagte Reaktionsende und die Konzentrationsverläufe des Edukts, Zwischenprodukts und Produkts auf den Terminals der Operatorstationen angezeigt. Wenn unerwünschte Betriebszustände auftreten, wird das Bedienungspersonal frühzeitig alarmiert und Anweisungen für Gegenmaßnahmen, die nur vom Operator ausgeführt werden dürfen, werden auf den Terminals angezeigt. Die Leistungsfähigkeit von MoSys/BIMS konnte während zweier Hydrierungs-Produktionskampagnen nachgewiesen werden

Theoretical study of the absorption spectra of the lithium dimer

For the lithium dimer we calculate cross sections for absorption of radiation from the vibrational-rotational levels of the ground X [singlet Sigma g +] electronic state to the vibrational levels and continua of the excited A [singlet Sigma u +] and B [singlet Pi u] electronic states. Theoretical and experimental data are used to characterize the molecular properties taking advantage of knowledge recently obtained from photoassociation spectroscopy and ultra-cold atom collision studies. The quantum-mechanical calculations are carried out for temperatures in the range from 1000 to 2000 K and are compared with previous calculations and measurements.Comment: 20 pages, revtex, epsf, 6 fig

Tumor Ulceration Does Not Fully Explain Sex Disparities in Melanoma Survival among Adolescents and Young Adults

Hypertension in kidney transplant recipients (KTRs) is a risk factor for cardiovascular mortality and graft loss. Data on the prevalence of hypertension and uncontrolled hypertension (uHT) in paediatric and young adult KTRs are scarce. Also, it is unknown whether 'transition' (the transfer from paediatric to adult care) influences control of hypertension. We assessed the prevalence of hypertension and uHT among Dutch paediatric and young adult KTRs and analysed the effects of transition. Additionally, we made an inventory of variations in treatment policies in Dutch transplant centres. Cross-sectional and longitudinal national data from living KTRs a parts per thousand currency sign30 years of age (a parts per thousand yen1-year post-transplant, eGFR > 20 mL/min) were extracted from the 'RICH Q' database, which comprises information about all Dutch KTRs <19 years of age, and the Netherlands Organ Transplant Registry database for adult KTRs (a parts per thousand yen18-30 years of age). We used both upper-limit blood pressure (BP) thresholds for treatment according to Kidney Disease: Improving Global Outcomes (KDIGO) guidelines. uHT was defined as a BP above the threshold. A questionnaire on treatment policies was sent to paediatric and adult nephrologists at eight Dutch transplant centres. Hypertension and uHT were more prevalent in young adult KTRs (86.4 and 75.8%) than in paediatric KTRs (62.7 and 38.3%) according to the KDIGO definition. Time after transplantation was comparable between these groups. Longitudinal analysis showed no evidence of effect of transition on systolic BP or prevalence of uHT. Policies vary considerably between and within centres on the definition of hypertension, BP measurement and antihypertensive treatment. Average BP in KTRs increases continuously with age between 6 and 30 years. Young adult KTRs have significantly more uHT than paediatric KTRs according to KDIGO guidelines. Transition does not influence the prevalence of uHT

Continuous-flow in-line solvent-swap crystallization of vitamin D(3)

A continuous tandem in-line evaporation–crystallization is presented. The process includes an in-line solvent-swap step, suitable to be coupled to a capillary based cooler. As a proof of concept, this setup is tested in a direct in-line acetonitrile mediated crystallization of Vitamin D₃. This configuration is suitable to be coupled to a new end-to-end continuous microflow synthesis of Vitamin D₃. By this procedure, vitamin particles can be crystallized in continuous flow and isolated using an in-line continuous filtration step. In one run in just 1 min of cooling time, ∼50% (w/w) crystals of Vitamin D₃ are directly obtained. Furthermore, the polymorphic form as well as crystals shape and size properties are described in this paper.Marc Escribà-Gelonch, Volker Hessel, Manuel C. Maier, Timothy Noël, Maria Fernanda Neira d’Angelo and Heidrun Gruber-Woelfle

Long-Term Transplantation Outcomes in Patients With Primary Hyperoxaluria Type 1 Included in the European Hyperoxaluria Consortium (OxalEurope) Registry

INTRODUCTION: In primary hyperoxaluria type 1 (PH1), oxalate overproduction frequently causes kidney stones, nephrocalcinosis, and kidney failure. As PH1 is caused by a congenital liver enzyme defect, combined liver–kidney transplantation (CLKT) has been recommended in patients with kidney failure. Nevertheless, systematic analyses on long-term transplantation outcomes are scarce. The merits of a sequential over combined procedure regarding kidney graft survival remain unclear as is the place of isolated kidney transplantation (KT) for patients with vitamin B6-responsive genotypes. METHODS: We used the OxalEurope registry for retrospective analyses of patients with PH1 who underwent transplantation. Analyses of crude Kaplan–Meier survival curves and adjusted relative hazards from the Cox proportional hazards model were performed. RESULTS: A total of 267 patients with PH1 underwent transplantation between 1978 and 2019. Data of 244 patients (159 CLKTs, 48 isolated KTs, 37 sequential liver–KTs [SLKTs]) were eligible for comparative analyses. Comparing CLKTs with isolated KTs, adjusted mortality was similar in patients with B6-unresponsive genotypes but lower after isolated KT in patients with B6-responsive genotypes (adjusted hazard ratio 0.07, 95% CI: 0.01–0.75, P = 0.028). CLKT yielded higher adjusted event-free survival and death-censored kidney graft survival in patients with B6-unresponsive genotypes (P = 0.025, P < 0.001) but not in patients with B6-responsive genotypes (P = 0.145, P = 0.421). Outcomes for 159 combined procedures versus 37 sequential procedures were comparable. There were 12 patients who underwent pre-emptive liver transplantation (PLT) with poor outcomes. CONCLUSION: The CLKT or SLKT remains the preferred transplantation modality in patients with PH1 with B6-unresponsive genotypes, but isolated KT could be an alternative approach in patients with B6-responsive genotypes

A retrospective analysis of noise-induced hearing loss in the Dutch construction industry

Purpose Noise exposure is an important and highly prevalent occupational hazard in the construction industry. This study examines hearing threshold levels of a large population of Dutch construction workers and compares their hearing thresholds to those predicted by ISO-1999. Methods In this retrospective study, medical records of periodic occupational health examinations of 29,644 construction workers are analysed. Pure-tone audiometric thresholds of noise-exposed workers are compared to a non-exposed control group and to ISO-1999 predictions. Regression analyses are conducted to explore the relationship between hearing loss and noise intensity, noise exposure time and the use of hearing protection. Results Noise-exposed workers had greater hearing losses compared to their non-noise-exposed colleagues and to the reference population reported in ISO-1999. Noise exposure explained only a small proportion of hearing loss. When the daily noise exposure level rose from 80 dB(A) towards 96 dB(A), only a minor increase in hearing loss is shown. The relation of exposure time and hearing loss found was similar to ISO-1999 predictions when looking at durations of 10 years or more. For the first decade, the population medians show poorer hearing than predicted by ISO-1999. Discussion Duration of noise exposure was a better predictor than noise exposure levels, probably because of the limitations in noise exposure estimations. In this population, noise-induced hearing loss was already present at the beginning of employment and increased at the same rate as is predicted for longer exposure duration