Zur Diagnostik des Diabetes insipidus unter besonderer Berücksichtigung hypophysektomierter Patienten

Verschiedene, am gleichen Patienten durchgeführte Stimulationsteste für die ADH-Sekretion (17-Std.-Durstversuch, Carter-Robbins-Test, osmotische Diurese) zeigen eine ausgezeichnete Korrelation. Auf Grund dieser Ergebnisse werden Richtlinien zur möglichst einfachen Diagnostik einer Konzentrationsstörung vorgeschlagen. In den meisten Fällen kann allein schon auf Grund eines exakt durchgeführten Durstversuchs eine Konzentrationsstörung nachgewiesen (höchste Urinosmolalität 750 mOsm/kg) werden. Lediglich bei einer höchsten Urinosmolalität im 17-Std.-Durstversuch zwischen 500 und 750 mOsm/kg müssen aufwendigere und den Patienten mehr belastende Tests (z. B. Carter-Robbins-Test) eingesetzt werden, um das Vorliegen bzw. den Grad einer Konzentrationsstörung endgültig diagnostizieren zu können. ADH-Injektionen dienen dabei zur Differenzierung zwischen einem ADH-Mangel und einer mangelhaften ADH-Ansprechbarkeit der Niere. Unsere Untersuchungen an hypophysektomierten Patienten (N=29) zeigen auch bei Patienten ohne polyurisch-polydiptisches Syndrom (N=22) eine gegenüber Normalpersonen signifikant eingeschränkte Konzentrationsleistung im 17-Std.-Durstversuch.The results of three different stimulation tests for ADH (17 hours thirst period, Carter-Robbins-test, osmotic diuresis) correlate well in the same patient. Because of this we propose a simplified procedure for the detection of failure to produce a concentrated urine. In most cases merely on the basis of a precisely executed thirst period test, one can either recognize an abnormality of concentration (highest urine osmolality less than 500 mOsm/kg), or exlude it (highest urine osmolality greater than 750 mOsm/kg). Only when the highest urine osmolality lies between 500 and 750 mOsm/kg after a 17 hour thirst must more painstaking tests (e.g. Carter-Robbins test) be employed to determine both the presence of and the degree of a failure to produce a concentrated urine. An injection of ADH can be used to differentiate between a deficiency of ADH and a defective response of the kidneys to ADH. Our investigations on hypophysectomized patients (n=29) showed that also in patients without the syndrome of polyuria-polydypsia (n=22), there was a significantly reduced capacity to concentrate urine during a 17 hour thirst period, as compared with normal people

K2 Discovers a Busy Bee: An Unusual Transiting Neptune Found in the Beehive Cluster

Open clusters have been the focus of several exoplanet surveys but only a few planets have so far been discovered. The \emph{Kepler} spacecraft revealed an abundance of small planets around small, cool stars, therefore, such cluster members are prime targets for exoplanet transit searches. Kepler's new mission, K2, is targeting several open clusters and star-forming regions around the ecliptic to search for transiting planets around their low-mass constituents. Here, we report the discovery of the first transiting planet in the intermediate-age (800 Myr) Beehive cluster (Praesepe). K2-95 is a faint ($\mathrm{Kp = 15.5\,mag}$) $\mathrm{M3.0\pm0.5}$ dwarf from K2's Campaign 5 with an effective temperature of $\mathrm{3471 \pm 124\,K}$, approximately solar metallicity and a radius of $\mathrm{0.402 \pm 0.050 \,R_\odot}$. We detected a transiting planet with a radius of $\mathrm{3.47^{+0.78}_{-0.53} \, R_\oplus}$ and an orbital period of 10.134 days. We combined photometry, medium/high-resolution spectroscopy, adaptive optics/speckle imaging and archival survey images to rule out any false positive detection scenarios, validate the planet, and further characterize the system. The planet's radius is very unusual as M-dwarf field stars rarely have Neptune-sized transiting planets. The comparatively large radius of K2-95b is consistent with the other recently discovered cluster planets K2-25b (Hyades) and K2-33b (Upper Scorpius), indicating systematic differences in their evolutionary states or formation. These discoveries from K2 provide a snapshot of planet formation and evolution in cluster environments and thus make excellent laboratories to test differences between field-star and cluster planet populations.Comment: 14 pages, 8 figues. Accepted for publication in A

Photoassociation spectroscopy of cold calcium atoms

Photoassociation spectroscopy experiments on 40Ca atoms close to the dissociation limit 4s4s 1S0 - 4s4p 1P1 are presented. The vibronic spectrum was measured for detunings of the photoassociation laser ranging from 0.6 GHz to 68 GHz with respect to the atomic resonance. In contrast to previous measurements the rotational splitting of the vibrational lines was fully resolved. Full quantum mechanical numerical simulations of the photoassociation spectrum were performed which allowed us to put constraints on the possible range of the calcium scattering length to between 50 a_0 and 300 a_0

Permeability of matrix-fracture systems under mechanical loading – constraints from laboratory experiments and 3-D numerical modelling

The permeability of single fractures is commonly approximated by the cubic law assumption, which is however only valid under the condition of a single phase laminar flow between parallel plates. Departure from cubic law are related to many features like aperture fluctuations due to fracture surface roughness, relative shear displacement, the amount of flow exchange between the matrix and the fracture itself, etc. In order to quantify constitutive relationships among the aforementioned aspects, we have conducted a flow-through experiment with a porous rock sample (Flechtinger sandstone) containing a single macroscopic fracture. Based on this experiment, we obtained range of variations of intrinsic rock parameters, permeability and stress-strain relationships of the combined matrix-fracture system under hydrostatic loading. From the measured deformation of the matrixfracture system, we derived the evolution in the mechanical aperture of the fracture. In order to quantify the processes behind the laboratory observations, we carried out coupled hydro-mechanical simulations of the matrix-fracture system. Navier–Stokes flow was solved in the 3-dimensional open rough fracture domain, and back-coupled to the Darcy flow and the poroelastic behaviour of the rock matrix. The results demonstrate that the elastic behaviour and the related permeability alteration of the fracture domain could be captured by the numerical simulation. Furthermore, the stress-strain values obtained in the vicinity of the fracture asperities suggest that inelastic deformation develops at low mechanical load. An attempt was made to quantify the inelastic deformation by using the failure envelope obtained by laboratory experiments (whether tensile, shear, compaction, or a combination of those). However, change in permeability observed in the experiments are significantly larger than that in the simulation showing the importance of plastic deformation during opening and closure of the fracture and its impact on the cubic law approximation