bluuebunny/crossref_metadata_2025 huggingface dataset:
Time‐resolved 3D quantitative flow MRI of the major intracranial vessels: Initial experience and comparative evaluation at 1.5T and 3.0T in combination with parallel imaging
Authors: Bammer Roland , Hope Thomas A. , Aksoy Murat , Alley Marcus T.
Published: December 2006

Exact knowledge of blood flow characteristics in the major cerebral vessels is of great relevance for diagnosing cerebrovascular abnormalities. This involves the assessment of hemodynamically critical areas as well as the derivation of biomechanical parameters such as wall shear stress and pressure gradients. A time‐resolved, 3D phase‐contrast (PC) MRI method using parallel imaging was implemented to measure blood flow in three dimensions at multiple instances over the cardiac cycle. The 4D velocity data obtained from 14 healthy volunteers were used to investigate dynamic blood flow with the use of multiplanar reformatting, 3D streamlines, and 4D particle tracing. In addition, the effects of magnetic field strength, parallel imaging, and temporal resolution on the data were investigated in a comparative evaluation at 1.5T and 3T using three different parallel imaging reduction factors and three different temporal resolutions in eight of the 14 subjects. Studies were consistently performed faster at 3T than at 1.5T because of better parallel imaging performance. A high temporal resolution (65 ms) was required to follow dynamic processes in the intracranial vessels. The 4D flow measurements provided a high degree of vascular conspicuity. Time‐resolved streamline analysis provided features that have not been reported previously for the intracranial vasculature. Magn Reson Med 57:127–140, 2007. © 2006 Wiley‐Liss, Inc.
Effect of tumor necrosis factor α on electrically induced calcium transients elicited in C2C12 skeletal myotubes
Authors: van Kann Lisa N. , Bakker Anthony J.
Published: December 2006

Diseases involving chronic inflammation can lead to prolonged exposure of skeletal muscle to inflammatory cytokines such as tumor necrosis factor α (TNFα), which may contribute to the skeletal muscle weakness seen in these conditions. In this study we examined the effect of a prolonged exposure to TNFα on intracellular Ca2+ transients elicited in skeletal C2C12 myotubes. A 48‐h exposure to TNFα (10 ng/mL) significantly reduced the peaks, time to peak, and rate of Ca2+ decay of electrically induced Ca2+ transients elicited in C2C12 skeletal myotubes. TNFα exposure had no significant effect on the resting Ca2+ levels. The results of this study indicate that prolonged exposure to TNFα decreases sarcoplasmic reticulum Ca2+ release in cultured skeletal muscle cells. This altered Ca2+ release could contribute to the muscle weakness found in conditions involving chronic inflammation. Muscle Nerve, 2006
Quantitative sensory testing of cold and vibration perception during compression of median nerve at the wrist
Authors: Tsuboya Hideshi , Tani Toshikazu , Ishida Kenji , Ushida Takahiro , Taniguchi Shinichirou , Kimura Jun
Published: December 2006

We conducted a sequential study of quantitative sensory testing (QST) during compression‐induced conduction block of the median nerve to determine relative vulnerability of the small and large myelinated nerve fibers. We tested cold (CPT) and vibratory perception thresholds (VPT) of the third digit in 15 healthy subjects during constant, localized compression for 30 min of the median nerve at the wrist. The orthodromic sensory nerve action potentials (SNAPs) recorded at wrist and elbow served to monitor the degree of associated conduction block. After the onset of nerve compression, it took 16 min for CPT to show the first change; VPT remained normal for 26 min. CPT recovered 2 min later than VPT after release of compression. The SNAP amplitude at the wrist diminished immediately at the start of compression and declined progressively, whereas the response at the elbow remained the same initially, showing no latency change for 20 min. A nearly identical time course of SNAP changes in the two experiments justified the comparison of separately tested CPT and VPT as a measure of modality‐specific vulnerability. Contrary to the common belief, a focal compression sufficient to produce rapidly reversible conduction abnormalities affects the slow‐conducting small myelinated fibers mediating cold perception before the fast‐conducting large myelinated fibers transmitting vibration perception. The data document the order of modality‐specific vulnerability of sensory nerve fibers to mild compression. The finding suggests that testing CPT, rather than VPT, provides a better QST to delineate rapidly reversible symptoms induced by compression. Muscle Nerve, 2006
Does motoneuron adaptation contribute to muscle fatigue?
Authors: Nordstrom Michael A. , Gorman Robert B. , Laouris Yiannis , Spielmann John M. , Stuart Douglas G.
Published: December 2006

To help reduce the gap between the cellular physiology of motoneurons (MNs) as studied “bottom‐up” in animal preparations and the “top‐down” study of the firing patterns of human motor units (MUs), this article addresses the question of whether motoneuron adaptation contributes to muscle fatigue. Findings are reviewed on the intracellularly recorded electrophysiology of spinal MNs as studied in vivo and in vitro using animal preparations, and the extracellularly recorded discharge of MUs as studied in conscious humans. The latter “top‐down” approach, combined with kinetic measurements, has provided most of what is currently known about the neurobiology of muscle fatigue, including its task and context dependencies. It is argued that although the question addressed is still open, it should now be possible to design new “bottom‐up” research paradigms using animal preparations that take advantage of what has been learned with the use of relatively noninvasive quantitative procedures in conscious humans. Muscle Nerve, 2006
The standardization of terminology of lower urinary tract function in children and adolescents: Report from the standardization committee of the International Children's Continence Society (ICCS)
Authors: Nevéus Tryggve , Gontard Alexander von , Hoebeke Piet , Hjälmås Kelm , Bauer Stuart , Bower Wendy , Jørgensen Troels Munch , Rittig Søren , Van de Walle Johan , Yeung Chung‐Kwong , Djurhuus Jens Christian
Published: December 2006

Purpose

We updated the terminology in the field of pediatric lower urinary tract function.

Materials and Methods

Discussions were held in the board of the International Children's Continence Society and an extensive reviewing process was done involving all members of the International Children's Continence Society, the urology section of the American Academy of Pediatrics, the European Society of Pediatric Urology, as well as other experts in the field.

Results and Conclusions

New definitions and a standardized terminology are provided, taking into account changes in the adult sphere and new research results. Neurourol. Urodynam. 26:90–102, 2007. © 2006 Wiley‐Liss, Inc.
Levator ani trigger point injections: An underutilized treatment for chronic pelvic pain
Authors: Langford Carolyn F. , Udvari Nagy Szilvia , Ghoniem Gamal M.
Published: December 2006

Aims

We conducted this study to examine the role of trigger point injections in females with chronic pelvic pain (CPP) of at least 6 months duration and specific levator ani trigger points.

Methods

This prospective study included 18 consecutive female patients with CPP and specific palpable levator ani trigger points. Pain was evaluated before and after trigger point injection on a Visual Analog Scale (VAS). Patient global satisfaction (PGS) and cure rates (PGC) were also measured by a VAS on a scale of 0–100%. The trigger points were identified manually by intravaginal palpation of the levator ani bilaterally. A mixture of 10 cc of 0.25% bupivacaine, 10 cc of 2% lidocaine and 1 cc (40 mg) of triamcinolone was used for injection of 5 cc per trigger point. A 5.5″ Iowa trumpet pudendal needle guide was used for injection. All but one injection were performed in the office setting without sedation. Pelvic floor muscle exercises were taught for use after injection. Success was defined as a decrease in pain as measured by a VAS of 50% or more, as well as PGS and PGC scores of 60% or greater. There was a mean follow up of 3 months after trigger point injection.

Results

Thirteen of 18 women improved with the first trigger point injection resulting in a comprehensive success rate of 72%. Six (33%) of 18 women were completely pain free.

Conclusion

In the management of CPP, a non‐surgical office‐based therapy such as trigger point injections can be effective in selected patients. Neurourol. Urodynam. 26:59–62, 2007. © 2006 Wiley‐Liss, Inc.
3D‐based hp‐adaptive first‐order shell finite element for modelling and analysis of complex structures—Part 1: The model and the approximation
Authors: Zboiński G. , Jasiński M.
Published: December 2006

The paper presents a 3D‐based adaptive first‐order shell finite element to be applied to hierarchical modelling and adaptive analysis of complex structures. The main feature of the element is that it is equipped with 3D degrees of freedom, while its mechanical model corresponds to classical first‐order shell theory. Other useful features of the element are its modelling and adaptive capabilities. The element is assigned to hierarchical modelling and hpq‐adaptive analysis of shell parts of complex structures consisting of solid, thick‐ and thin‐shell parts, as well as of transition zones, where h, p and q denote the mesh density parameter and the longitudinal and transverse orders of approximation, respectively. The proposed hp‐adaptive first‐order shell element can be
joined with 3D‐based hpq‐adaptive hierarchical shell elements or 3D hpp‐adaptive solid elements by means of the family of 3D‐based hpq/hp‐ or hpp/hp‐adaptive transition elements.

The main objective of the first part of our research, presented in this paper, is to provide non‐standard information on the original parts of the element algorithm. In order to do that, we present the definition of shape functions necessary for p‐adaptivity, as well as the procedure for imposing constraints corresponding to the lack of elongation of the straight lines perpendicular to the shell mid‐surface, which is the procedure necessary for q‐adaptivity. The 3D version of constrained approximation presented next is the basis for h‐adaptivity of the element. The second part of our research, devoted to methodology and results of the numerical research on application of the element to various plate and shell problems, are described in the second part of this paper. Copyright © 2006 John Wiley & Sons, Ltd.
The CIP method embedded in finite element discretizations of incompressible fluid flows
Authors: Banijamali Bahareh , Bathe Klaus‐Jürgen
Published: December 2006

Quite effective low‐order finite element and finite volume methods for incompressible fluid flows have been established and are widely used. However, higher‐order finite element methods that are stable, have high accuracy and are computationally efficient are still sought. Such discretization schemes could be particularly useful to establish error estimates in numerical solutions of fluid flows. The objective of this paper is to report on a study in which the cubic interpolated polynomial (CIP) method is embedded into 4‐node and 9‐node finite element discretizations of 2D flows in order to stabilize the convective terms. To illustrate the capabilities of the formulations, the results obtained in the solution of the driven flow square cavity problem are given. Copyright © 2006 John Wiley & Sons, Ltd.
A natural neighbour‐based moving least‐squares approach for the element‐free Galerkin method
Authors: Most Thomas
Published: December 2006

The element‐free Galerkin method (EFG) and the natural element method (NEM) are two well known and widely used meshless methods. Whereas the EFG method can represent moving boundaries like cracks only by modifying the weighting functions the NEM requires an adaptation of the nodal set‐up. But on the other hand the NEM is computationally more efficient than EFG. In this paper a new concept for the automatic adjustment of nodal influence domains in the EFG method is presented in order to obtain an efficiency similar to the NEM. This concept is based on the definition of natural neighbours for each meshless node which can be determined from a Voronoi diagram of the nodal set‐up. In this approach adapted nodal influence domains are obtained by interpolating the distances to the natural neighbours depending on the direction. In the paper we show that this concept leads, especially for problems with grading node density, to a reduced number of influencing nodes at the interpolation points and consequently a significant reduction of the numerical effort. Copyright © 2006 John Wiley & Sons, Ltd.
Arrays of dynamic circular loads moving on an infinite plate
Authors: Sun Lu , Luo Feiquan
Published: December 2006

Steady‐state dynamic responses of a Kirchhoff plate resting on a viscoelastic Winkler foundation subject to arrays of moving constant and harmonic loads with uniform circular distribution is studied in this paper using Fourier transform and generalized Duhamel's integral. A computational schema is constructed based on a two‐fold fast Fourier transform in a moving co‐ordinate system. Numerical case studies using a single moving load as well as four moving loads mimicking four wheel‐loads of a moving vehicle are conducted. Parameters of the plate are typical values of structural and material properties of highway pavements. Displacement responses of the plate to these five loading speeds seem to be very close to each other, though the vertical velocity and acceleration responses show considerable differences. The effect of load frequency on amplitude of response of plate is insignificant for parameters used in this study. Copyright © 2006 John Wiley & Sons, Ltd.
Non‐matching mesh gluing by meshless interpolation—an alternative to Lagrange multipliers
Authors: Tian Rong , Yagawa Genki
Published: December 2006

Rewards of using non‐matching meshes are great in many aspects: sub‐meshing a complex structure in a sub‐structure‐wise manner separately and/or in parallel; selective local refinement; unlimited scalability guarantee for generating meshes in increasingly large‐scale finite element simulation, etc. However, when meshes do not match, a gluing algorithm is required to enforce inter‐domain continuity. ‘Non‐matching’ terminologically originates from mesh discretization in nature, and the non‐matching mesh issue is therefore avoidable or does not exist in a node‐based or meshless discretization in meshless methods. Motivated by this, a gluing algorithm is developed based on meshless interpolation. The gluing is accomplished by continuous trial and test functions across non‐matching meshes constructed using nodes only. The developed gluing algorithm is tested in static and wave propagation problems in two and three dimensions. It is demonstrated that the gluing algorithm does not deteriorate convergence and accuracy compared with the one‐piece conforming mesh. Compared with Lagrange multiplier gluing—one of the most common approaches—the current algorithm has two significant benefits: (1) easier implementation in any dimension and (2) positive definite banded system matrices, not acting against equation solvers, and hence better suited for large‐scale finite element analysis. Copyright © 2006 John Wiley & Sons, Ltd.
Study of EDL effect on 3‐D developing flow in microchannel with Poisson–Boltzmann and Nernst–Planck models
Authors: Ng E. Y. K. , Tan S. T.
Published: December 2006

Microchannels have been suggested to be a very effective heat transfer device. However, the electrical double layer (EDL) effect in a microchannel is anticipated to be significant. In this paper, two EDL models coupled with Navier–Stokes equations were used to compute a 3‐D developing microchannel flow. The Poisson–Boltzmann model (PBM) has been proven to be a promising tool in studying the EDL effect for developed microchannel flow, with respect to its accuracy and efficiency. However, it was commended that the assumption of Boltzmann distribution in PBM, for electric ion concentration distribution in particular was questionable in the developing flow. Nernst–Planck model (NPM), with its two extra partial differential equations (PDEs) to predict the ion concentration distribution, was reported to be a more appropriate model for developing microchannel flow though increased RAM and CPU were needed as compared to the PBM. The governing equations for both models were discretized for developing rectangular microchannel flows in Cartesians co‐ordinate. An additional source term, related to the electric potential, resulting from the EDL effect was introduced in the conventional z‐axis momentum equation as a body force, thereby modifying the flow characteristics. A finite‐volume scheme was used to solve the PDEs. The discrepancy in the results predicted by the two models was more dominant in the near‐wall region and not in the mainstream region. However, the performance of the microchannel was significantly affected by the EDL effect. An increase in Schmidt number will lead to decrease in friction coefficient. For the effect of aspect ratios (ARs), the discrepancy of f Re and Nu values for different ARs was obvious. Therefore, a 3‐D analysis was concluded to be important and necessary for investigating the EDL effect in microchannels. Copyright © 2006 John Wiley & Sons, Ltd.
Poly(propylene)/aspen/liquid polybutadiene composites: maximization of impact strength, tensile and modulus by statistical experimental design
Authors: Kokta B. V. , Michalkova D. , Fortelny I. , Krulis Z.
Published: December 2006

A systematic study of the effect of concentration of maleated poly(propylene) (MAPP), dicumyl peroxide (DCP), polyisobutadiene isocyanate (PBNCO) and fiber content on the mechanical properties of aspen‐poly(propylene)(PP) composite was undertaken with the objective to maintain or increase the impact strength without losing tensile strength reinforcement. Using STAGRAPHIC Plus it was possible to determine the optimum concentration of additives and to maximize both the impact as well as tensile properties well above that of pure PP. Copyright © 2006 John Wiley & Sons, Ltd.
Preimplantation genetic diagnosis for myotonic dystrophy type 1: detection of crossover between the gene and the linked marker APOC2
Authors: Kakourou Georgia , Dhanjal Seema , Daphnis Danny , Doshi Alpesh , Nuttall Sarah , Gotts Sarah , Serhal Paul , Delhanty Joy , Harper Joyce , SenGupta Sioban
Published: December 2006

Objective

To report two cases of preimplantation genetic diagnosis (PGD) for myotonic dystrophy type I (DM1) where cross‐over between the DMPK locus and a linked polymorphic marker APOC2 was detected.

Methods

Embryos from in vitro fertilisation (IVF) were biopsied at day 3 of development and single blastomeres collected. Diagnosis was performed by duplex or triplex fluorescent‐polymerase chain reaction (F‐PCR) to amplify DMPK and APOC2 loci, or DMPK with APOC2 and D19S112 polymorphic markers.

Results

A total of 22 oocytes were retrieved from the two patients, 20 were inseminated of which 15 fertilized (75%) and were suitable for biopsy on day 3. A diagnosis was obtained for 12 embryos (80%) and was confirmed in all un‐transferred embryos. Crossover between DM1 and APOC2 was detected in two embryos from the two different couples. Transfer of two embryos took place in both cases resulting in two pregnancies. Each couple have had a healthy baby.

Conclusion

The above cases highlight the importance of using more than one linked polymorphic marker in PGD‐PCR protocols and emphasize the danger of using APOC2 as the sole marker to identify the DM1 mutation. Copyright © 2006 John Wiley & Sons, Ltd.
On the stereomicrostructure‐based mechanisms of physical properties of poly(methyl methacrylate): 1. space charge behaviour and physical ageing
Authors: Guarrotxena Nekane , de Frutos Manuel
Published: December 2006

Three samples of poly(methyl methacrylate) (PMMA) were characterized after careful purification. Their composition in terms of some repeating stereosequences, especially mmr termini of isotactic sequences, was determined. Their space charge behaviour was analysed using the thermal step (TS) method. A correlation between the electrical current intensity, as given by the TS method, and the stereochemical microstructure content in each sample was evidenced. The results are explained in the light of previous data on the specific microstructures present in the samples at different contents. The physical ageing of the samples was studied, quantitatively, through differential scanning calorimetry measurements prior to and after equally performed thermal treatments of the samples. The corresponding values of the loss of enthalpy agree with the content of mmr tetrad termini of isotactic sequences. The results are analysed on the basis of the differences in stereochemical composition of the samples. The results give further evidence of the role of some definite stereosequences in physical properties as proposed in earlier works on poly(vinyl chloride) and polypropylene. Copyright © 2006 Society of Chemical Industry
Bone cell attachment and growth on well‐characterized chitosan films
Authors: Hamilton Virginia , Yuan Youling , Rigney Debbie A , Chesnutt Betsy M , Puckett Aaron D , Ong Joo L , Yang Yunzhi , Haggard Warren O , Elder Steven H , Bumgardner Joel D
Published: December 2006

Chitosan has been widely researched for bone tissue and implant applications. While initial results are promising, there are inconsistent reports regarding the biological responses. This may be due to inadequate evaluation of chitosan material properties. This study evaluated normal human osteoblast precursor cell attachment and proliferation on a series of well‐characterized chitosan films. The chitosan films exhibited a range of properties: 76–96% degree of de‐acetylation (DDA), 2400–8200 kDa viscosity‐average molecular weight, 62–90° contact angle, 0.24–2.46% residual ash, 5.3–287 µg cm−2 residual protein and 23–40% crystallinity. There was no trend or correlation between DDA, crystallinity, contact angle, molecular weight, residual ash or protein content and the attachment or growth of bone cells on chitosan films. All films supported higher levels of bone cell proliferation than tissue culture plastic, which supports the general hypothesis that chitosans are osteocompatible. The 78 and 92% DDA chitosan films supported the most cell proliferation, approximately 16 times that of tissue culture plastic controls, but no chitosan physiochemical property correlated with the increased cell growth. The lack of correlation is hindered since more than one physiochemical property changed for each chitosan material. Data do indicate that there may be much variability in chitosan materials, and this variability may make understanding and comparing biological performance of chitosan materials difficult. These results highlight the need for systematic characterizations of chitosan materials for predictable biomedical applications. Copyright © 2006 Society of Chemical Industry
Study of the effect of hyperbranched polyols on cationic UV curable coating properties
Authors: Chen Zhigang , Webster Dean C
Published: December 2006

Cycloaliphatic epoxide‐based cationic UV curable coatings containing three different hyperbranched polyols (HBPs) were systematically formulated and characterized. Polyether polyols were found to deter epoxide conversion under low UV intensity. For high UV intensity, the cycloaliphatic epoxide conversion increased with polyol content. Coatings with HBPs had better flexibility and solvent resistance than those containing a reference triol. Compared to the triol and polyester HBPs, polyether HBPs imparted lower Tg and hardness but a better flexibilizing effect to the coatings. At higher R values, the coating solvent resistance decreased except for those with one polyether HBP.

A two‐peak phenomenon was discovered in the residual thermal reaction heat curve after photoDSC experiments. These two peaks were found to be related to the thermal relaxation behavior of the photocured inhomogeneous film, and the reactivation and reaction of the ‘trapped living cationic species’. The capability of the polyol to lower the high‐temperature‐peak temperature corresponded well with the flexibilizing ability. Copyright © 2006 Society of Chemical Industry
Dornröschen und Mauerblümchen: Nachzügler und vergessene Arbeiten in der Physik
Authors: Marx Werner
Published: December 2006

Wissenschaftliche Publikationen werden von Fachkollegen im Durchschnitt in den ersten drei Jahren am häufigsten zitiert, danach fällt die Rate rasch ab. Es gibt jedoch Arbeiten, die erst nach vielen Jahren oder Jahrzehnten ihre volle Wirkung entfalten. Berühmte Beispiele für solche “Dörnröschen” sind Walter Kohns und Lu Shams Pionierarbeiten über die Dichtefunktionaltheorie oder die EPR‐Arbeit von Albert Einstein, Boris Podolsky und Nathan Rosen. Manche Pionierarbeiten waren jedoch ihrer Zeit zu weit voraus und gerieten wie ihre Verfasser in Vergessenheit. Ein Beispiel für ein solches “Mauerblümchen” ist die Arbeit von Ralph Alpher und Robert Herman von 1949 mit der ersten theoretischen Vorhersage der kosmischen Hintergrundstrahlung.
Jeder Schuss ein Treffer: Physik und Treffsicherheit beim Sport
Authors: Mathelitsch Leopold , Thaller Sigrid
Published: December 2006

Bei Sportarten, in denen es auf Treffsicherheit ankommt, zählen nicht Kraft oder Schnelligkeit, sondern präzise Bewegungen. Beim Basketball erhöht eine geringe Fluggeschwindigkeit gepaart mit einem steileren Flugwinkel die Trefferchance. Bei Schießsportarten kommt es auch darauf an, wie groß der Schütze die Zielscheibe tatsächlich sieht. Dartprofis neigen sich vor, um die Schussdistanz erlaubt zu reduzieren. Beim Bowling kann der Ball nur dann alle Pins auf einen Schlag abräumen, wenn er auf einer perfekt gekrümmten Bahn läuft. Das ermöglicht ein Gleitfilm aus Öl auf der Bahn, dessen Dicke zum Ziel hin abnimmt.
Der falsche Knick im Licht: Materialien mit negativem Brechungsindex
Authors: Dolling Gunnar , Wegener Martin , Linden Stefan
Published: December 2006

Durch Maßschneidern funktioneller nanoskaliger Baugruppen photonische Atome, dicht zusammengepackt zu einem effektiven Medium, können künstliche Materialien mit qualitativ neuartigen optischen Eigenschaften hergestellt werden. Ein Beispiel sind Materialien mit einer negativen Brechzahl. Die Strahlen‐ und Wellenoptik dieser Materialien steckt voller Überraschungen, wie bereits einfache computergenerierte Abbildungen und erste Experimente zeigen.
Wasser auf dem Mars: Neue Ergebnisse der Mars‐Rover und Raumsonden
Authors: Hauber Ernst
Published: December 2006

Der NASA‐Rover Opportunity fand in Meridiani Planum morphologische, chemische und mineralogische Hinweise auf ehemaliges Wasser an der Oberfläche. Die Analysen weisen auf ein insgesamt trockenes Klima hin, in dem episodisch salziges Wasser in einer sauren und oxidierenden Umgebung vorhanden war. Die besten derzeitigen Analogien auf der Erde sind möglicherweise saure Salzseen in Südwestaustralien, die durch kurzzeitige Überflutung, Verdunstung und nachfolgende Austrocknung entstehen. Die Ergebnisse der ESA‐Mission Mars Express unterstützen die Ergebnisse von Opportunity durch den Nachweis von Tonmineralen und Sulfaten, deren Bildung ebenfalls Wasser erfordert. Das Klima auf dem Mars scheint nach einem relativ feuchten Beginn vor etwa 3,8 Milliarden Jahren zunehmend trockener geworden zu sein.
Herzdiagnose mit Spins: Magnetokardiographie mit optisch gepumpten Magnetometern
Authors: Bison Georg , Weis Antoine
Published: December 2006

Die Magnetokardiographie (MKG) misst das extrem schwache Magnetfeld der Herzmuskeln mit hoch empfindlichen Sensoren. Es kann verschiedene Herzkrankheiten wesentlich zuverlässiger diagnostizieren als etablierte Verfahren. Ihr heutiger Nachteil liegt in der Verwendung von SQUID‐Sensoren. Diese müssen auf Temperaturen von 4 K gekühlt werden, was hohe Anschaffungs‐ und Betriebskosten verursacht. Optisch gepumpte Magnetometer könnten der MKG zum Durchbruch in der Praxis verhelfen. Diese Sensoren arbeiten bei Raumtemperatur, was den technischen Aufwand und die Kosten erheblich reduziert. Ein Demonstrationsaufbau an der Universität Fribourg zeigt, dass die Methode zuverlässig funktioniert.
Das Bild vom Bild – der Zauberspiegel Mirage. Spielwiese
Authors: Ucke Christian
Published: December 2006

Der Zauberspiegel, Mirage genannt, besteht aus zwei gleichen, annähernd parabolischen Hohlspiegeln. Diese liegen mit der Öffnung aufeinander. Der obere Spiegel hat ein zentrales Loch, in dem zwei reelle Bilder eines Gegenstandes erscheinen, die man auf den ersten Blick nicht von der Wirklichkeit unterscheiden kann. Der Gegenstand selbst befindet sich am Boden des unteren Spiegels. Mit den Gesetzen der geometrischen Optik lässt sich dieses Phänomen erklären.
Das Deutsche Museum in München
Authors: Teichmann Jürgen
Published: December 2006

Die Wurzeln der heutigen Science Center in Deutschland finden sich im Deutschen Museum in München. Es wurde 1903 gegründet, geistiger Vater und ideenreicher hartnäckiger Organisator war der Bau‐ und Elektroingenieur Oskar von Miller. Das damals neuartige Konzept sah vor, nicht nur die Geschichte von “Meisterwerken” zu präsentieren, sondern Wissenschaft und Technik mit Vorführungen, eigenen Experimenten der Besucher und neuen Medien dem Volk nahe zu bringen. Ein bis heute erfolgreiches Konzept.
Nicht leicht zu durchschauende Lichtgitter
Authors: Schlichting H. Joachim
Published: December 2006

Ein Spaziergang am Morgen, wenn das Wasser des Teichs noch leicht vom Nebel der kühlen Nacht verhangen ist, gibt manchmal zu einem eindrucksvollen Lichtschauspiel Anlass. Wenn die Sonne sich nämlich langsam Bahn bricht und ihr Licht an dem in der kühlen Nacht entstandenen Nebel gestreut wird, können unter günstigen Bedingungen interessante, auf den ersten Blick nicht zu durchschauende Lichtgitter entstehen.
Kolloquium bei Tee und Gebäck
Authors: Loos Andreas
Published: December 2006

Als der Junge in Berlin zur Welt kommt, geben ihm seine jüdischen Eltern die Vornamen Joseph Meyer. Doch als der Sohn fünf Jahre alt ist, beschließt die Familie zu konvertieren. Zusammen mit seinem Vater und vier Brüdern wird der Junge christlich getauft und erhält zwei neue Vornamen. Das behütet ihn vor der Diskriminierung von Juden.
Zergeht im Mund und nicht im Glas
Authors: Vilgis Thomas
Published: December 2006

Wenn Sie Ihren Gästen eine kleine Überraschung bieten möchten, dann servieren Sie Ihren Campari‐Orange doch einmal als fest‐flüssiges Zweiphasensystem: Campari‐Perlen schwimmen im Orangensaft, mischen sich aber nicht mit ihm. Kaum zu glauben, aber die Physik der weichen Materie macht es möglich.
Feinheiten im Sonarsystem von Fledermäusen
Authors: Müller Rolf
Published: December 2006

Strukturen in den extrem faltigen Gesichtern von Fledermäusen können eine physikalische Funktion haben: Sie sind Teil des Sonarsystems, mit dem sich die Tiere orientieren. Numerische Verfahren zeigen, wie diese Strukturen die ausgesandten und empfangenen Ultraschallfelder beeinflussen.
KATRIN unterwegs
Authors: Bührke Thomas
Published: December 2006

Ende November erhielt das Forschungszentrum Karlsruhe eine außergewöhnlich voluminöse Fracht: Das Hauptspektrometer des Karlsruher Tritium Neutrino Experimentes KATRIN. Gebaut wurde es im bayerischen Deggendorf. Doch wegen der gewaltigen Länge von 24 Metern, einem Durchmesser von 10 Metern und einem Gewicht von 200 Tonnen kam der Transport über Land nicht in Frage. Stattdessen ging das Spektrometer auf eine 8800 km lange Reise.
Androgen‐insensitive prostate cancer cells transiently respond to castration treatment when growing in an androgen‐dependent prostate environment
Authors: Halin Sofia , Hammarsten Peter , Wikström Pernilla , Bergh Anders
Published: December 2006

BACKGROUND

Castration‐induced involution of the normal prostate is caused by primary effects in the prostate stroma and vasculature, but if this is the case also in tumors is unknown.

METHODS

Androgen‐independent AT‐1 prostate tumor cells were therefore injected into the ventral prostate (VP) in Copenhagen rats. Seven days later when the growing tumor was surrounded by normal VP tissue the rats were castrated and the effect examined 3 and 7 days later.

RESULTS

Castration reduced vascular density in the surrounding VP tissue and this was accompanied by tumor cell hypoxia, apoptosis, and temporarily retarded tumor growth. Castration‐induced VP tissue regression occurred more rapidly in the contra‐lateral than in the tumor‐bearing lobe.

CONCLUSIONS

Androgen‐independent tumor cell respond to castration when growing in an androgen‐dependent environment. The presence of a tumor influences the castration response in the surrounding normal tissue. The microenvironment determines how prostate epithelial cells respond to castration. Prostate 67: 370–377, 2007. © 2006 Wiley‐Liss, Inc.
Genomic scan of 12 hereditary prostate cancer families having an occurrence of pancreas cancer
Authors: Pierce Brandon L. , Friedrichsen‐Karyadi Danielle M. , McIntosh Laura , Deutsch Kerry , Hood Lee , Ostrander Elaine A. , Austin Melissa A. , Stanford Janet L.
Published: December 2006

BACKGROUND

Prostate cancer is a genetically heterogeneous disease. Using the occurrence of other cancers in hereditary prostate cancer (HPC) families is a promising strategy for developing genetically homogeneous data sets that can enhance the ability to identify susceptibility loci using linkage analysis.

METHODS

Twelve HPC families with the co‐occurrence of adenocarcinoma of the pancreas were selected from the Prostate Cancer Genetic Research Study (PROGRESS). Non‐parametric linkage analysis for a prostate/pancreas cancer susceptibility phenotype was performed using 441 genome‐wide microsatellite markers.

RESULTS

No statistically significant linkage signal was detected in this analysis. The strongest linkage signals, as measured by Kong and Cox LOD score (KC LOD), were observed on chromosomes 2q37.2‐q37.3 (KC LOD = 1.01; P = 0.02) and 16q23.2 (KC LOC = 1.05; P = 0.01).

CONCLUSIONS

Despite the lack of statistically significant findings, four chromosomal regions, three of which (2q, 16q, 17q) were previously noted as harboring potential susceptibility loci, showed suggestive linkage results in this scan. Prostate 67: 410–415, 2007. © 2006 Wiley‐Liss, Inc.
Atlantic air–sea interaction and seasonal predictability
Authors: Rodwell M. J. , Folland C. K.
Published: December 2006

We analyse patterns of North Atlantic air–sea interaction in observations and model output throughout the annual cycle with the dual aims of validating natural variability in climate models, and quantifying seasonal predictability of the atmosphere and of ocean surface temperatures.

The Met Office's HadCM3 coupled ocean–atmosphere model is shown to represent well the atmospheric forcing of sea surface temperature (SST) in the North Atlantic region through the action of latent‐heat fluxes. Winter ocean temperature anomalies in both observations and model appear to be preserved below the shallow summer mixed layer and to re‐emerge in the following autumn.

We find observational evidence from the last half of the twentieth century for SST forcing of the atmospheric circulation in the North Atlantic region. Results validate our atmospheric model (HadAM2b) and confirm the levels of potential predictability of the North Atlantic Oscillation (NAO) that have been found in recent modelling studies. We suggest that the ultimate correlation skill of a winter NAO hindcast in this period is in the range 0.45 to 0.63.

Analysis of observational and atmospheric model data from the first half of the twentieth century identifies very little predictability of the winter NAO. We suggest that the change in seasonal predictability is genuine and may be related to the strength of decadal oscillations.

The ocean–atmosphere model, which incorporates a different atmospheric component (HadAM3), fails to show a causal link between North Atlantic temperatures and the atmospheric circulation even during periods where low‐frequency variability is as strong as in the recent observations.

A brief observational investigation suggests that any implied predictability of the winter NAO based on a knowledge of South Atlantic SSTs depends on the existence of secular trends in the data. Tropical Pacific SSTs appear to influence the winter climate of the North Atlantic region, but not via trends in the NAO. © Crown copyright, 2002.
Study of hail density parametrizations
Authors: Castellano N. E. , Nasello O. B. , Levi L.
Published: December 2006

One aspect of hailstone growth that has received attention over the last twenty years is the importance of low‐density riming growth in hail. Density is an important parameter in riming growth because it regulates hail size and is also involved in other atmospheric processes, like crystal multiplication, charge transfer, etc. New numerical dynamic and cinematic models take into account the variability of density with growth parameters (such as size of cloud droplets, impact velocity and surface temperature) in order to attain more realistic results. These kinds of models need to have a function that describes the real low‐density riming process.

Analysing previous results, it is clear that several different empirical parametrizations are employed to describe density. These parametrizations relate density to growth parameters through the variable X=Vob/Ts, where Vo is the impact velocity of droplets into the target, b is the droplet size, and Ts the hail surface temperature.

These empirical expressions give different density values for identical growth conditions. It is important to note that these parametrizations stem from experimental data obtained in very different growth conditions and with different collector geometries.

Working with experimental density data, we can show that different parametrizations are equivalent if X is defined in an appropriate way (taking into account correct impact velocity and collector geometry). Different environmental conditions are taken into account by means of Stokes' parameter.

Due to this finding, we have aimed at developing a parametrization to be used in cloud models, which satisfactorily represents all experimental results. Copyright © 2002 Royal Meteorological Society
Linearized radiation and cloud schemes in the ECMWF model: Development and evaluation
Authors: Janiskov'a Marta , Mahfouf Jean‐françois , Morcrette Jean‐jacques , Chevallier Frederic
Published: December 2006

A proper consideration of cloud–radiation interactions in linearized models is required for variational assimilation of cloud properties. Therefore, both a linearized cloud scheme and a linearized radiation scheme have been developed for the European Centre for Medium‐Range Weather Forecasts (ECMWF) data assimilation system. The tangent‐linear and adjoint versions of the ECMWF short‐wave radiation scheme are prepared without a priori modifications. The complexity of the radiation scheme for the long‐wave part of the spectrum makes accurate computations expensive. To reduce its computational cost, a combination of artificial neural networks and Jacobian matrices is defined for the linearized long‐wave radiation scheme. The linearized cloud scheme is diagnostic and has been adapted for this study. The accuracy of the linearization of both radiation and diagnostic cloud schemes is examined. The inclusion of a more sophisticated radiation scheme within the existing linearized parametrizations improves the accuracy of the tangent‐linear approximation. However, the impact of the linearized diagnostic cloud scheme is small, suggesting that the linearized model will require further developments of cloud parametrization.

The adjoint technique is used to investigate the sensitivity of the radiation schemes to changes in temperature, humidity and cloud properties. This study shows which variables can be adjusted when certain observations of the surface and/or of the top‐of‐atmosphere radiation fluxes are used in data assimilation. It also indicates the vertical extent of the influence of such observations. Copyright © 2002 Royal Meteorological Society.
Near‐surface turbulent fluxes in stable stratification: Calculation techniques for use in general‐circulation models
Authors: Zilitinkevich S. S. , Perov V. L. , King J. C.
Published: December 2006

Practically oriented flux‐calculation techniques based on correction functions to the neutral drag and heat/mass transfer coefficients are further developed. In the traditional formulation, the correction functions depend only on the bulk Richardson number. However, data from measurements of turbulent fluxes and mean profiles in stable stratification over different sites exhibit too strong variability in this type of dependencies. Indirect evidence from climate and weather prediction modelling also shows that the traditional flux‐calculation technique is not sufficiently advanced. It is conceivable that other mechanisms besides the surface‐layer stratification and, therefore, other arguments besides the bulk Richardson number must be considered. The proposed technique includes a newly discovered effect of the static stability in the free atmosphere on the surface‐layer scaling and accounts for the general essential difference between the roughness lengths for momentum and scalars. Besides bulk Richardson number, recommended correction functions depend on one more stability parameter, involving the Brunt–Väisälä frequency in the free atmosphere, and on the roughness lengths. Copyright © 2002 Royal Meteorological Society.
Potential improvement to forecasts of two severe storms using targeted observations
Authors: Leutbecher M. , Barkmeijer J. , Palmer T. N. , Thorpe A. J.
Published: December 2006

The potential to improve short‐range forecasts of two extratropical storms by using supplementary observations in regions lacking accurate observations is investigated. In the idealized framework used here, a control and a truth experiment are selected from a set of forecasts initialized with analyses from different numerical weatherprediction centres. Synthetic soundings of wind and temperature are created from the truth experiment and are assimilated with four‐dimensional variational analysis using the operational observation‐error estimates for radiosondes and the initial condition of the control experiment as background. Through multiple analysis/forecast experiments we obtain a nonlinear estimate of the optimal zone for observing (OZO); that is the zone in which the use of a given number of supplementary observations leads to the largest reduction in forecast error. We evaluate targeting techniques based on either total‐energy singular vectors (TESVs) or on Hessian singular vectors (HSVs) by comparison with the OZO and by comparison with experiments in which the same amount of supplementary observations are distributed in an untargeted manner, namely with a random distribution scheme (RDS).

Overall, the HSV targeting is superior to the TESV targeting in the two cases. In one case there is a significant difference between the target regions determined with TESVs and HSVs. The HSV‐based observing strategy resembles the OZO in terms of the observing region and the achieved forecast‐error reduction. With the RDS, the forecast error is variable and likely to be larger than the forecast error obtained with singular‐vector targeting. Experiments with target regions of different sizes show that supplementary observations in an area of about 3×106 km2 are required to achieve a significant forecast improvement. A two‐dimensional sampling pattern with soundings spaced at a distance of about 1–2 times the horizontal correlation length‐scale of the backgrounderror estimate appears very efficient. In additional impact experiments for one case, observations were perturbed with noise to represent observational error. The perturbations are almost as likely to improve the forecast as to worsen it compared with the forecast using unperturbed observations. Copyright © 2002 Royal Meteorological Society.
Variational assimilation of ocean tomographic data: Twin experiments in a quasi‐geostrophic model
Authors: Rémy Elisabeth , Gaillard Fabienne , Verron Jacques
Published: December 2006

The possibility of using tomography data as a constraint in variational data assimilation is explored by performing twin experiments. Realistic travel‐time data are generated in a quasi‐geostrophic model applied to the western Mediterranean Sea. After checking the robustness of the method with this dataset, a sensitivity study analyses the propagation of information by the model, and tests the effect of different parameters such as the starting point of the optimization or the length of the assimilation period. It appears that the variational method is well adapted to the nature of tomographic data that provide at the same time high time resolution and space integrals. The results clearly show the ability of this dataset to recover the temporal evolution of heat content in each layer and improve various components of the circulation described by the model. Tomography must then be considered as an important source of information that may contribute with altimetry or local in situ measurement to the description of the ocean state and its evolution. Copyright © 2002 Royal Meteorological Society.
The counter‐propagating Rossby‐wave perspective on baroclinic instability. I: Mathematical basis
Authors: Heifetz E. , Bishop C. H. , Hoskins B. J. , Methven J.
Published: December 2006

It is shown that Bretherton's view of baroclinic instability as the interaction of two counter‐propagating Rossby waves (CRWs) can be extended to a general zonal flow and to a general dynamical system based on material conservation of potential vorticity (PV). The two CRWs have zero tilt with both altitude and latitude and are constructed from a pair of growing and decaying normal modes. One CRW has generally large amplitude in regions of positive meridional PV gradient and propagates westwards relative to the flow in such regions. Conversely, the other CRW has large amplitude in regions of negative PV gradient and propagates eastward relative to the zonal flow there. Two methods of construction are described. In the first, more heuristic, method a ‘home‐base’ is chosen for each CRW and the other CRW is defined to have zero PV there. Consideration of the PV equation at the two home‐bases gives ‘CRW equations’ quantifying the evolution of the amplitudes and phases of both CRWs. They involve only three coefficients describing the mutual interaction of the waves and their self‐propagation speeds. These coefficients relate to PV anomalies formed by meridional fluid displacements and the wind induced by these anomalies at the home‐bases. In the second method, the CRWs are defined by orthogonality constraints with respect to wave activity and energy growth, avoiding the subjective choice of home‐bases. Using these constraints, the same form of CRW equations are obtained from global integrals of the PV equation, but the three coefficients are global integrals that are not so readily described by ‘PV‐thinking’ arguments. Each CRW could not continue to exist alone, but together they can describe the time development of any flow whose initial conditions can be described by the pair of growing and decaying normal modes, including the possibility of a super‐modal growth rate for a short period. A phase‐locking configuration (and normal‐mode growth) is possible only if the PV gradient takes opposite signs and the mean zonal wind and the PV gradient are positively correlated in the two distinct regions where the wave activity of each CRW is concentrated. These are easily interpreted local versions of the integral conditions for instability given by Charney and Stern and by Fjørtoft. Copyright © 2004 Royal Meteorological Society