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[en] The covering of a cooling tower as suggested prevents the escape of steam possibly mixed with other components into the environment, thus preventing the possibility of smog formation. From the cap sealing the cooling tower on its upper side, the steam is sucked off by an external jacket-cooled pipe line by means of a ventilator. The ventilator lies in a bypass of the pipeline, thus keeping condensates developed away from the ventilator. The condensate reaches the draintank in the footing of the cooling tower through the pipeline. This drain tank also takes up the condensate developing directly in the tower. (HP)
[de]Die vorgeschlagene Abdeckung eines Kuehlturmes verhindert das Austreten von evtl. mit anderen Bestandteilen vermengten Wasserdampfes in die Umgebung und verhindert damit die Moeglichkeit der Smogbildung. Aus der den Kuehlturm nach oben dicht abschliessenden Haube wird der Dampf mittels eines Ventilators durch eine aussen liegende mantelgekuehlte Rohrleitung abgesaugt. Der Ventilator liegt in einem Bypass der Rohrleitung, wodurch bis dahin schon angefallenes Kondensat vom Ventilator ferngehalten wird. Das Kondensat gelangt durch die Rohrleitung direkt in das Auffangbecken im Fuss des Kuehlturmes, welches auch das direkt im Turm anfallende Kondensat aufnimmt. (HP)
[en] Among the many interesting possibilities for types of future missions that would benefit strongly from LISA and LISA Pathfinder technology development, three will be discussed. They are in the fields of fundamental physics, Earth science, and gravitational wave astronomy. The first is a mission to measure the gravitational time delay due to the Sun from a spacecraft near the L-1 point of the Earth-Sun system. It would require gravitational reference sensors (GRSs) with roughly 10-13 [10-6 Hz/f] m/s2 /vHz performance at frequencies down to about 0.3 microHz. The second type of mission is future drag-free missions to measure time variations in the Earth's gravitational field. One example of such a mission will be described, with two satellites in the same polar orbit at about 300 km altitude. Changes in the roughly 50 km satellite separation would be measured with 10-14 or better accuracy, and spurious accelerations of the test masses in the GRS on each satellite would be the other main measurement accuracy limitation. The third mission is a possible moderately improved LISA follow-on mission aimed at being able to detect mergers of 10 solar mass black holes with IMBHs out to redshifts of about 10 in order to investigate the formation and growth of IMBHs in more detail than LISA will be able to achieve.
[en] Ni nanorods are dispersed into gelatine gels and used as nanoprobes to estimate the shear modulus of the surrounding gel matrix by magnetization measurements. The nanorods are synthesized via pulsed electrodeposition of Ni into porous alumina, released from the templates by dissolution of the oxide layer and after several processing steps dispersed into gelatine gels with an isotropic orientation-distribution. Magnetization measurements of the resulting gels show a significant influence of the gelatine concentration on their magnetic behavior. In particular, with decreasing gelatine concentration the measured coercivity is reduced indicating a mechanical rotation of the nanorods in the field direction. A theoretical model which relates the measured coercivity to the shear modulus of the surrounding gel matrix is introduced and applied to investigate the ageing process of gelatine gels with different gelatine concentrations at room temperature. - Highlights: • AAO-template synthesis of uniaxial ferromagnetic single domain Ni nanorods. • Embedding nanorods as magnetic probes in soft elastic gelatine hydrogels. • Coercivity of isotropic samples increases with gelation time and gelatine concentration. • Quantitative relationship between coercivity and matrix shear modulus is obtained from an extended Stoner–Wohlfarth-model. • Semi-quantitative method for magnetic rheometry of soft elastic materials
[en] We report on LISA experimental projects being pursued at JILA. Our focus is on the design and testing of a flight-compatible laser stabilization reference cavity. This is a dual cylinder ULE cavity, designed to provide high thermal and thermo-mechanical isolation in the millihertz frequency regime of interest to LISA. A modification of this hard-mounted design may allow for use in space without the need for clamping during launch. Progress so far consists of initial design, performance estimates, and construction. Simple thermal model calculations on the design indicate a thermal attenuation of 106 at 1 mHz, corresponding to a cavity strain of 3*10-16 /rtHz for a 0.01 K/rtHz stability of the mounting surface. Finite element analysis indicates cavity strain attenuation of 5*107 or better due to thermo-mechanical effects in the surrounding environment, and low sensitivity to vibration along the cavity axis. Setup and testing of two identical cavities and a laser-locking test system is ongoing. Another project was recently concluded, testing the low-frequency stability of commercial voltage references. Voltage reference performance is relevant to the stability of electrically applied forces on the LISA proof masses, and commercial references do not have well characterized noise in the sub-Hz regime. Our measurements confirmed that the best commercial reference was the AD587LN, with a typical noise of 2.1±0.6 ppm/rtHz at 0.1 mHz, in a temperature-stabilized environment of ∼10mK/rtHz. This agrees closely with prior work by other groups.
[en] The local mechanical coupling of ferromagnetic nanorods in hydrogels was characterized by magnetization measurements. Nickel nanorods were synthesized by the AAO-template method and embedded in gelatine hydrogels with mechanically soft or hard matrix properties determined by the gelatine weight fraction. By applying a homogeneous magnetic field during gelation the nanorods were aligned along the field resulting in uniaxially textured ferrogels. The magnetization curves of the soft ferrogel exhibited not only important similarities but also characteristic differences as compared to the hard ferrogel. The hystereses measured in a field parallel to the texture axis were almost identical for both samples indicating effective coupling of the nanorods with the polymer network. By contrast, measurements in a magnetic field perpendicular to the texture axis revealed a much higher initial susceptibility of the soft as compared to the hard ferrogel. This difference was attributed to the additional rotation of the nanorods allowed by the reduced shear modulus in the soft ferrogel matrix. Two methods for data analysis were presented which enabled us to determine the shear modulus of the gelatine matrix which was interpreted as a local rather than macroscopic quantity in consideration of the nanoscale of the probe particles. - Highlights: • Nanorods are embedded as magnetic probes in gelatine gels. • Elastic rotation of the rods can be induced by applying a homogeneous magnetic field. • Rod rotation has significant influence on the magnetization curves. • Two methods are presented to estimate the shear modulus of the matrix from the magnetization curves
[en] In this study the influence of dipolar interactions on the orientation-dependent magnetization behavior of an ensemble of single-domain nickel nanorods was investigated. The rods were synthesized by electrodeposition of nickel into porous alumina templates. Some of the rods were released from the oxide and embedded in gelatine hydrogels (ferrogel) at a sufficiently large average interparticle distance to suppress dipolar interactions. By comparing the orientation-dependent hystereses of the two ensembles in the template and the gel-matrix it could be shown that the dipolar interactions in the template considerably alter the functional form of the angular-dependent coercivity. Analysis of the magnetization curves for an angle of 60° between the rod-axes and the field revealed a significantly reduced coercivity of the template compared to the ferrogel, which could be directly attributed to a stray field induced magnetization reversal of a steadily increasing number of rods with increasing field strength. The magnetization curve of the template could be approximated by a weighted linear superposition of the hysteresis branches of the ferrogel. The magnetization reversal process of the rods was investigated by analyzing the angular-dependent coercivity of the non-interacting nanorods. Comparison of the functional form with analytical models and micromagnetic simulations emphasized the assumption of a localized magnetization reversal. Additionally, it could be shown that the nucleation field of rods with diameters in the range 18–29 nm tends to increase with increasing diameter. (paper)
[en] Colloidal dispersions of Ni nanorods were synthesized by pulsed electrodeposition of Ni into nanoporous aluminum oxide layers followed by dissolution of the templates. Geometrical characterization of the nanorods by transmission electron microscopy and scanning electron microscopy allowed us to determine the average length (100-250 nm) and diameter (20-40 nm) of the rods and to estimate the thickness of the polyvinylpyrrolidone surfactant layer. Due to their acicular shape, nanorods of the given size are uniaxial ferromagnetic single domain particles and exhibit a distinct anisotropic polarizability. These two characteristic properties are the physical basis for magnetic field-dependent optical transmission and allow us to investigate the rotational diffusion of the nanorods in liquid dispersion. In the present study, we employed AC magnetization measurements, dynamical light scattering and optical transmission measurements in a rotating magnetic field to determine the rotational diffusion coefficient. The results from all three methods were consistent and agree with theory within a factor of 2.
[en] Electromagnetic transitions in 22F were investigated using the 9Be(14C, p) reaction at Elab=22 MeV. Proton-γ and proton-γ-γ coincidences were measured using a segmented E-ΔE Si telescope and the Florida State University γ detector array. γ-ray energies, intensities, and branching ratios were measured, and mean lifetimes were inferred using the Doppler-shift attenuation method. Several new states and many new γ-decay branches were observed. The results are compared with sd shell model calculations using the USD, USDA, and USDB interactions. The excitation energies of the states below 2 MeV agree slightly better with the calculations using the USD interaction, while the levels between 2 and 4 MeV agree somewhat better with those using the newer USDA and USDB interactions
[en] The low-lying level structure of 94Zr was recently studied at the University of Kentucky Accelerator Laboratory with the (n,n'γ) reaction, and lifetimes were obtained for the majority of the levels up to about 3.5 MeV in excitation. A remarkable outcome from this study was that the measured lifetime for the 22+ state, found to be 183-12+13 fs, yielded a B(E2) value for the 22+ → 01+ transition about 1.5 times larger than that for the 21+ → 01+ transition, thus making this a unique case among even-even nuclei. Recent results obtained in subsequent measurements in other laboratories using different probes indicate that the value of the lifetime for the state must be somewhat larger than reported. This discrepancy motivated our remeasurement of the lifetime for the 22+ state in 94Zr using the (n,n'γ) reaction, and an extensive set of measurements was conducted