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Purpose: To investigate the effect of dorsal clitoral nerve stimulation (DCNS) on bothersome urgency to defecate with or without fecal incontinence and the patient-reported discomfort or adverse effect with the method. Methods: For dorsal clitoral nerve stimulation, a battery powered, handheld stimulator was used, set to a pulse width of 200 µs and a frequency of 20 Hz. One electrode was placed at the preputium of the clitoris and acted as cathode while an anode electrode was placed on the belly. Prior to stimulation the patients were asked to complete a bowel habit diary throughout 14 consecutive days before and during stimulation. Results: Fourteen out of the 16 patients included completed the study. A decrease in the number of episodes (per day) with strong urgency declined in eight patients but increased in four cases during the stimulation period. An increase in episodes with moderate or mild urgency was observed in 11 and 6 cases, respectively, and a decrease in defecation without the feeling of urgency or passive incontinence decreased in two thirds of the patients. Two patients discontinued the study prematurely, on due to worsening in symptoms and one due to pelvic pain. Conclusion: Although the results may be promising, much still must be learned about the method including mode and duration of stimulation, better electrodes and more patient friendly equipment together with the development of better questionnaires to assess the patient burden of urgency. [ABSTRACT FROM AUTHOR]

Precession of the rotation axis is an often neglected mechanical driving mechanism for flows in planetary interiors, through viscous coupling at the boundaries and topographic forcing in non-spherical geometries. We investigate precession-driven flows in spheroidal shells over a wide range of parameters and test the results against theoretical predictions. For Ekman numbers down to 8.0 x 10-7, we see a good accordance with the work of Busse, who assumed the precession-driven flow to be dominated by a rigid rotation component that is tilted to the main rotation axis. The velocity fields show localized small-scale structures for lower Ekman numbers and clear signals of inertial waves for some parameters. For the case of moderate viscosity and strong deformation, we report the realization of multiple solutions at the same parameter combination, depending on the initial condition. [ABSTRACT FROM AUTHOR]

Single-channel current seems to be one of the most obvious characteristics of ion transport. But in some cases, its determination is more complex than anticipated at first glance. Problems arise from fast gating in time series of patch-clamp current, which can lead to a reduced apparent (measured) single-channel current. Reduction is caused by undetected averaging over closed and open intervals in the anti-aliasing filter. Here it is shown that fitting the measured amplitude histograms by Beta distributions is an efficient tool of reconstructing the true current level from measured data. This approach becomes even more powerful when it is applied to amplitude distributions-per-level. Simulated time series are employed to show that the error sum is a good guideline for finding the correct current level. Furthermore, they show that a Markov model smaller than the one used for gating analysis can be used for current determination (mostly O-C, i.e., open-closed). This increases the reliability of the Beta fit. The knowledge of the true current level is not only important for the understanding of the biophysical properties of the channel. It is also a prerequisite for the correct determination of the rate constants of gating. The approach is applied to measured data. The examples reveal the limits of the analysis imposed by the signal-to-noise ratio and the shape of the amplitude distribution. One application shows that the negative slope of the I-V curve of the human MaxiK channel expressed in HEK293 cells is caused by fast gating. [ABSTRACT FROM AUTHOR]

Two recently developed multiscale approaches for simulations of metalization morphologies under ionized sputter deposition conditions are reviewed. These methods are capable of predicting the growth of thin films on the feature scale, based on calculations that are simultaneously carried out on all relevant scales and consistently employ data from atomistic simulations. In both techniques, the first step consists in molecular dynamics simulations that compute the relative probabilities of all relevant reactions taking place during physical vapor deposition. These probabilities are consequently employed in feature-scale simulators. One of the methods employs a two-dimensional cellular automaton technique to calculate the film topographies. The second approach employs a Green function method to combine the molecular dynamics results with a line of sight transport model in a two-dimensional feature, and incorporates all effects of re-emission and re-sputtering in a self-consistent manner. In the final step, a level-set method is used to describe the morphology of the growing film. Both methods provide complete growth rate models that allow the inclusion of energy and angular dependent reaction rates. Several applications of both techniques are discussed. [Copyright &y& Elsevier]

Examines the incidence of hypertension among renal allograft recipients. Heart weight of donors with subarachnoid hemorrhage; Systolic blood pressure of persons receiving allograft from donors with subarachnoid hemorrhage; Inducement of hypertension after transplantation of kidneys from persons affected by subarachnoid hemorrhage.

Examines the Rayleigh-number dependence of stagnant-lid convection with a temperature-dependent viscosity. Transition of the flow with increasing Rayleigh number; Occurrence of stagnant-lid type of convection; Dependence of interior temperature on the Rayleigh number.

So far, numerical simulations have mostly considered buoyancy as the driving mechanism of the dynamo process. However, also precession can drive a dynamo, as first suggested by Bullard in 1949. We investigate the properties of precession-driven dynamos in ellipsoidal planets by the use of a finite volume code. In planets, it is much more effective to drive a precessional flow by the pressure differences induced by the topography of the precessing body rather than by viscous coupling to the walls. Numerical simulations are the only method offering the possibility to investigate the influence of the topography since laboratory experiments normally are constrained by the predetermined geometry of the vessel. We discuss how ellipticity of the planets can be included in our simulations by the use of a non-orthogonal grid. Here, we will present some first results and conclude that laminar precession-driven flows can drive kinematic dynamos. [ABSTRACT FROM AUTHOR]

Abstract: Super-Earths, a recently discovered class of exoplanets, have been inferred to be of a similar rock and metal composition to the Earth. As a result, the possibility that they are characterised by the presence of plate tectonics has been widely debated. However, as the super-Earths have higher masses than Earth, it is assumed that they will also have higher Rayleigh numbers and non-dimensional heating rates. Accordingly, we conduct a systematic 2D study to investigate the influence of these parameters on the surface behaviour of mantle convection. The main focus of our work considers the response of surface motion to the mantle''s internal heating. However, we also include an analysis of other parameters scaling with planet mass, such as viscosity. In agreement with the findings of Valencia and O''Connell (2009) and van Heck and Tackley (2011) we find plate-like surface mobilisation for increased Rayleigh numbers. But increasing the internal heating leads to the formation of a strong stagnant-lid because the mantle heating effects thermally activated viscosity. Additionally, viscosity is affected by the increased pressures and temperatures of super-Earths. In total, our findings indicate that surface mobility will likely be reduced on super-sized Earths. Our numerical models show that the interior temperature of the convecting system is of vital importance. In planets with a hotter interior plate tectonics is less likely. [Copyright &y& Elsevier]

Abstract: Our numerical study focuses on convection in a rotating spherical shell with the objective to model combined thermal and compositional convection as proposed for the Earth’s core. Since the core is cooling, a thermal gradient is established, which can drive thermal convection. Simultaneously, due to the solidification of the inner core latent heat is released at the freezing front and the concentration of the light constituents of the liquid phase increases thus providing a source for compositional buoyancy. Typically, the molecular diffusivities of both driving components differ by some orders of magnitude. To account for this difference it is indicated to adopt a double-diffusive convection model in treating Earth’s core dynamics. As opposed to purely thermal or purely compositional convection the double-diffusive system is controlled by two Rayleigh numbers associated with the respective buoyancy sources. Using the Rayleigh numbers as control parameters neutral curves of the linear onset of convection in the rotating shell are determined for different Ekman numbers and diffusivity ratios. It is found that the neutral curves depend significantly on the system parameters. By comparison with the analytical solutions of the rotating cylindrical annulus it is shown that the neutral curves represent a superposition of curves associated with solutions for different azimuthal wave numbers. Furthermore, fully non-linear simulations are presented in order to elucidate the effect of isochemical and fixed chemical flux boundary conditions on the convection. We consider three driving scenarios with varying thermo-chemical forcing ratios. Both the forcing ratio and the chemical boundary condition have distinct effects on the system that are discussed separately. [Copyright &y& Elsevier]

Abstract: We present a new finite volume code for modeling three-dimensional thermal convection in a spherical shell with strong temperature- and pressure-dependent viscosity. A new discretization formulation of the viscous term, tailored to the finite volume method on a colocated grid, enables laterally variable viscosity. A smoothed cubed–sphere grid is used to avoid pole problems which occur in latitude–longitude grids with spherical coordinates. The spherical shell is topologically divided into six cubes. The equations are formulated in primitive variables, and are treated in the Cartesian cubes. In order to ensure mass conservation a SIMPLER pressure correction procedure is applied and to handle strong viscosity variations of Δη =107 and high Rayleigh numbers of Ra =108 the pressure correction algorithm is combined with a pressure weighted interpolation method to satisfy the incompressibility condition and to avoid oscillatory pressure solutions. The model is validated by a comparison of diagnostical parameters of steady-state cubic and tetrahedral convection with other published spherical models and a detailed convergence test on successively refined grids. Lateral variable fluid properties have a significant influence on the convection pattern and heat flow dynamics. The influence of temperature- and pressure-dependent viscosity on the flow is systematically analyzed for basal and mixed-mode heated thermal convection in the spherical shell. A new method to classify the simulations to the mobile, transitional or stagnant-lid regime is given by means of a comparison of selected diagnostical parameters, a significantly improved classification as compared to the common surface layer mobility criterion. A scaling law for the interior temperature and viscosity in the stagnant-lid regime is given. Purely basal heating and strongly temperature-dependent rheology stabilize plume positions and yield with a weak time dependence of the convecting system, while the amount of additional internal heating controls the strength of time dependence. Strength and partitioning of basal and internal heat sources in the mantle seems to be of major importance to specify the dynamics of the flow field and therefore the evolution of the Earth and other planets. Additional pressure dependence strongly influences the dynamics even if the magnitude of pressure variation is relatively small. For an appropriate combination of pressure and temperature dependence we observe a kind of low and high viscosity zone in the asthenosphere and deep in the mantle. The viscosity–depth profile of such a flow shows striking similarities to viscosity profiles from inversion of seismic, geoid and post-glacial rebound data. [Copyright &y& Elsevier]

Examines the impact of calcium ion-dependent potassium channel activation on the hyperpolarization of the plasma membrane in unicelular green algae Eremosphaera viridis. Messengers involved in the regulation of potassium channels; Effect of InsP[sub 3] microinjection on the polarity of the plasma membrane.

Investigates the mixing in three-dimensional stationary convection of a Boussinesq fluid at infinite Prandtl number. Dispersion of passive point tracers for a range of Rayleigh numbers in both square-cell convection and artificially stabilized hexagonal-cell convection; Tracer algorithm used.

We present experimental evidence for a quantum phase transition in the easy-axis S=3/2 anisotropic quasi-one-dimensional ferromagnet CoCl2⋅2D2O in a transverse field. Elastic neutron scattering shows that the magnetic order parameter vanishes at a transverse critical field μ0Hc=16.05(4) T, while inelastic neutron scattering shows that the gap in the magnetic excitation spectrum vanishes at the same field value, and reopens for H>Hc. The field dependence of the order parameter and the gap are well described by critical exponents β=0.45±0.09 and zν close to 1/2, implying that the quantum phase transition in CoCl2⋅2D2O differs significantly from the textbook version of a S=1/2 Ising chain in a transverse field. We attribute the difference to weak but finite three-dimensionality of the magnetic interactions. [ABSTRACT FROM AUTHOR]

Introduction: An important question related to the composition of Earth's present day mantle composition is the relatively high concentration of highly siderophile elements (HSE) [1]. However, this could be explained by the addition of metal cores of differentiated asteroids impacting during the late accretion phase [2]. At this time the Earth was most likely covered by a deep magma ocean as a result of the moon forming impact [3]. To better understand to what extent impactor material and in particular the impactor's core mix with the magma ocean more knowledge of the fragmentation and subsequent mixing is required. Are impactors completely dispersed upon the penetration process or do large fragments or the entire core remain more or less intact so that they almost directly settle into Earth's core and do not contribute to the HSE budget of the mantle? Experimental and numerical approaches have been used to answer this in the past [4,5]. To expand on the numerical work, we improved the treatment of fragmentation of impactor material in the Eulerian shock physics code iSALE. We developed and implemented a new method that allows determining the size frequency distribution of the impactor core as a function of different model parameters, such as impactor size, velocity and the magma ocean depth. Methods: We use the grid-based Eulerian shock physics code iSALE-2D [6,7] to perform simulations of impacts of differentiated impactors into a magma ocean. However, since such codes are primarily optimized to accu - rately produce large scale features of the impact process, like the size or depth of the resulting crater, artifacts may occur when looking at behavior close to the resolution limit. The fragmentation of the impactor, here we focus on the metal cores, may be considered as a multi-scale process, which causes artifacts if the fragment size is of the or - der of the grid resolution. To reduce the influence of such resolution-controlled effects, we developed and imple - mented a new method to improve the fragmentation in our simulations. The idea is to identify when a fragment as a whole or in part approaches the resolution limit and use petrophysical criterions to determine if fragmentation occurs. If it is the case, we replace the material by a particle with size and mass of a given fragment. This particle then represents the fragment for the rest of the simulation. The setup of our simulations consists of a differentiated impactor hitting a magma ocean target. The radius of the impactor is on the order of hundreds of kilometers and varies between simulations. The impact velocity ranges between 5 and 20 km/s and we assume different depths of the magma ocean. Results: We analyze the size-frequency distribution of the impactor core fragments for different simulation setups to understand how these parameters influence the fragmentation. The preliminary results show that the impactor core breaks apart quite significantly during impacts. The higher the impact velocity the smaller the average fragment sizes. Larger impactor radii also result in larger fragment sizes. A comparison between simulations with and without the new method also shows that its usage generates significantly more and smaller fragments, which is expected since regular iSALE has the tendency to artificially clump material which results in larger fragments. Acknowledgments: We gratefully acknowledge the developers of iSALE-2D, including Gareth Collins, Kai Wünnemann, Dirk Elbeshausen, Tom Davison, Boris Ivanov and Jay Melosh. This work was funded by the Deutsche Forschungsgemeinschaft (SFB-TRR170, subproject C2 and C4). [ABSTRACT FROM AUTHOR]

Boundary layers play an important role in controlling convective heat transfer. Their nature varies considerably between different application areas characterized by different boundary conditions, which hampers a uniform treatment. Here, we argue that, independent of boundary conditions, systematic dissipation measurements in Rayleigh-Bénard convection capture the relevant near-wall structures. By means of direct numerical simulations with varying Prandtl numbers, we demonstrate that such dissipation layers share central characteristics with classical boundary layers, but, in contrast to the latter, can be extended naturally to arbitrary boundary conditions. We validate our approach by explaining differences in scaling behavior observed for no-slip and stress-free boundaries, thus paving the way to an extension of scaling theories developed for laboratory convection to a broad class of natural systems. [ABSTRACT FROM AUTHOR]

Introduction: to optimise the clinical outcome of medial patellofemoral ligament (MPFL) reconstruction, restoration of normal patellofemoral kinematics is important. This pilot study aimed to assess the potential of a computer modelling technique for subject-specific surgical planning in anatomically normal knees. Material and methods: a finite element modelling technique to analyse contact and kinematics of subject-specific patellofemoral joints (PFJs) was developed. The technique was validated against in vitro experimental results. Eight normal knees with MPFL intact were analysed in three stages; when MPFL was intact, following MPFL transection and following MPFL reconstruction. Three femoral tunnel positions: anatomical, 5mm distal and 5mm proximal to the anatomical one were investigated. Five grafts: single and double bundle gracilis and semitendinosus grafts and a quadriceps graft were used. Results: following MPFL transection, peak lateral contact pressures were elevated and medial patellofemoral joint contact pressures were reduced. The patella shifted and tilted laterally following MPFL transection. PFJ contact pressure and tracking were restored after MPFL reconstruction with an anatomical femoral tunnel position. Too proximal and distal femoral tunnel positions elevated medial joint contact pressures and increased medial patellar tilting. Using different tendons in the normal knees affected joint contact characteristics and patellar tracking. Conclusions: the potential of using the computer modelling technique to evaluate contact mechanics and patellar stability of pre- and post- MPFL reconstruction in normal knees is evident. Future study will develop this work and enable analysis of MPFL reconstruction in patients with trochlear dysplasia without limitations inherent with in vitro and in vivo investigation. [ABSTRACT FROM AUTHOR]

Experimental and numerical studies of thermal convection have shown that sufficiently vigorous convective flows exhibit a large-scale thermal wind component sweeping along small-scale thermal boundary layer instabilities. A characteristic feature of these flows is an intermittent behavior in the form of irregular reversals in the orientation of the large-scale circulation. There have been several attempts toward a better understanding and description of the phenomenon of flow reversals, but so far most of these models are based on a statistical analysis of few-point measurements or on simplified theoretical assumptions. The analysis of long-term data sets (>5 x 105 turnover times &taut, = d/ums) obtained by numerical simulations of turbulent two-dimensional Rayleigh-Benard convection allows us to get a more comprehensive view of the spatio-temporal flow behavior. By means of a global statistical analysis of the characteristic spatial modes of the flow we extract information about the stability of dominant large-scale modes as well as the reversal paths in state subspace. We examine probability density functions and drift vector fields of two-dimensional state subspaces spanned by different large-scale spatial modes. This also provides information about the coexistence of dominant modes. [ABSTRACT FROM AUTHOR]

Mannan-binding lectin (MBL) and MBL-associated serine protease 2 (MASP-2) are key factors of the lectin pathway of complement activation. Polymorphisms of the MBL2 and MASP-2 genes affect serum levels of MBL and MASP-2. In patients with colorectal cancer (CRC), the MBL and MASP-2 serum levels are increased and high MASP-2 levels are associated with recurrence and poor survival, whereas low MBL levels predict post-operative pneumonia. It is not known whether these associations are genetically based. In this study, the MBL and MASP-2 genotypes are investigated in 593 patients with CRC and 348 healthy controls. The potential association between genetic profile and infections, recurrence and survival is evaluated. Four single-nucleotide polymorphisms (SNPs) of MBL2 were analysed using TaqMan assays, with characterization of MBL2 wildtype A, variants B, C and D and alleles H/L, Y/X and P/Q. The SNP D120G for MASP-2 was determined. Serum levels of MBL and MASP-2 were measured. The MBL2 and MASP-2 genotype distribution was similar among patients with CRC and healthy controls and MBL2 genotype significantly associated with MBL concentration in serum ( P < 0.0001). No significant association between MBL2/MASP-2 genotype and post-operative infectious complications ( P = 0.33 and 0.22), recurrent cancer or survival ( P = 0.74 and P = 0.61 respectively) was found. Thus, the increased serum levels of MBL and MASP-2 found in patients with CRC are not explained for by genetic profiles. In contrast to what has been demonstrated for serum levels of MBL and MASP-2, the genotypes do not predict disease course of the CRC patients. [ABSTRACT FROM AUTHOR]

We present a numerical study on convection in a rotating spherical shell that explores the influence of the two possible driving sources in planetary iron cores: temperature differences exceeding the adiabatic gradient and compositional differences that arise from the rejection of light elements at the inner core freezing front. Similarly, both effects play an important role in driving convection in Earth's outer core but their individual contribution remains uncertain. Dynamically, both components significantly differ in terms of their diffusion timescales since heat diffuses much faster than chemical elements. To investigate the influence of the driving mechanisms on the convective flow pattern, we consider different scenarios including the two extreme cases of purely thermally and purely compositionally driven convection and the more likely situation of a joint action of both sources. We solely focus on implications resulting from the given difference in the thermal and chemical diffusivity. For the present, we disregard the effects that might arise from the more realistic case of distinct thermal and chemical boundary conditions. We show that the driving mechanism strongly affects the resulting flow pattern, for example, differential rotation and global quantities such as mean energy and transport efficiencies. Additionally, we use a selected case for a specific comparison of two different codes based on a pseudospectral and a finite volume formulation, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Snake venom metalloproteinases (SVMPs) are multifunctional enzymes involved in several symptoms following snakebite, such as severe local hemorrhage. Multidomain P-III SVMPs are strongly hemorrhagic, whereas single domain P-I SVMPs are not. This indicates that disintegrin-like and cysteine-rich domains allocate motifs that enable catalytic degradation of ECM components leading to disruption of capillary vessels. Interestingly, some P-III SVMPs are completely devoid of hemorrhagic activity despite their highly conserved disintegrin-like and cysteine-rich domains. This observation was approached in the present study by comparing the effects of jararhagin, a hemorrhagic P-III SVMP, and berythractivase, a pro-coagulant and non-hemorrhagic P-III SVMP. Both toxins inhibited collagen-induced platelet aggregation, but only jararhagin was able to bind to collagen I with high affinity. The monoclonal antibody MAJar 3, that neutralizes the hemorrhagic effect of Bothrops venoms and jararhagin binding to collagen, did not react with berythractivase. The three-dimensional structures of jararhagin and berythractivase were compared to explain the differential binding to collagen and MAJar 3. Thereby, we pinpointed a motif within the Da disintegrin subdomain located opposite to the catalytic domain. Jararhagin binds to both collagen I and IV in a triple helix-dependent manner and inhibited in vitro fibrillogenesis. The jararhagin–collagen complex retained the catalytic activity of the toxin as observed by hydrolysis of fibrin. Thus, we suggest that binding of hemorrhagic SVMPs to collagens I and IV occurs through a motif located in the Da subdomain. This allows accumulation of toxin molecules at the site of injection, close to capillary vessels, where their catalytic activity leads to a local hemorrhage. Toxins devoid of this motif would be more available for vascular internalization leading to systemic pro-coagulant effects. This reveals a novel function of the disintegrin domain in hemorrhage formation. [Copyright &y& Elsevier]

Fast gating in time series of patch-clamp current demands powerful tools to reveal the rate constants of the adequate Hidden Markov model. Here, two approaches are presented to improve the temporal resolution of the direct fit of the time series. First, the prediction algorithm is extended to include intermediate currents between the nominal levels as caused by the anti-aliasing filter. This approach can reveal rate constants that are about 4 times higher than the corner frequency of the anti-aliasing filter. However, this approach is restricted to time series with very low noise. Second, the direct fit of the time series is combined with a beta fit, i.e., a fit of the deviations of the amplitude histogram from the Gaussian distribution. Since the "theoretical" amplitude histograms for higher-order Bessel filters cannot be calculated by analytical tools, they are generated from simulated time series. In a first approach, a simultaneous fit of the time series and of the Beta fit is tested. This simultaneous fit, however, inherits the drawbacks of both approaches, not the benefits. More successful is a subsequent fit: The fit of the time series yields a set of rate constants. The subsequent Beta fit uses the slow rate constants of the fit of the time series as fixed parameters and the optimization algorithm is restricted to the fast ones. The efficiency of this approach is illustrated by means of time series obtained from simulation and from the dominant K+ channel in Chara. This shows that temporal resolution can reach the microsecond range. [ABSTRACT FROM AUTHOR]

Level or jump detectors generate the reconstructed time series from a noisy record of patch-clamp current. The reconstructed time series is used to create dwell-time histograms for the kinetic analysis of the Markov model of the investigated ion channel. It is shown here that some additional lines in the software of such a detector can provide a powerful new means of patch-clamp analysis. For each current level that can be recognized by the detector, an array is declared. The new software assigns every data point of the original time series to the array that belongs to the actual state of the detector. From the data sets in these arrays distributions-per-level are generated. Simulated and experimental time series analyzed by Hinkley detectors are used to demonstrate the benefits of these distributions-per-level. First, they can serve as a test of the reliability of jump and level detectors. Second, they can reveal beta distributions as resulting from fast gating that would usually be hidden in the overall amplitude histogram. Probably the most valuable feature is that the malfunctions of the Hinkley detectors turn out to depend on the Markov model of the ion channel. Thus, the errors revealed by the distributions-per-level can be used to distinguish between different putative Markov models of the measured time series. [ABSTRACT FROM AUTHOR]

Fluorometric determination of the chlorophyll (Chl) content of cyanobacteria is impeded by the unique structure of their photosynthetic apparatus, i.e., the phycobilisomes (PBSs) in the light-harvesting antennae. The problems are caused by the variations in the ratio of the pigment PC to Chl a resulting from adaptation to varying environmental conditions. In order to include cyanobacteria in fluorometric analysis of algae, a simplified energy distribution model describing energy pathways in the cyanobacterial photosynthetic apparatus was conceptualized. Two sets of mathematical equations were derived from this model and tested. Fluorescence of cyanobacteria was measured with a new fluorometer at seven excitation wavelength ranges and at three detection channels (650, 685 and 720 nm) in vivo. By employing a new fit procedure, we were able to correct for variations in the cyanobacterial fluorescence excitation spectra and to account for other phytoplankton signals. The effect of energy-state transitions on the PC fluorescence emission of PBSs was documented. The additional use of the PC fluorescence signal in combination with our recently developed mathematical approach for phytoplankton analysis based on Chl fluorescence spectroscopy allows a more detailed study of cyanobacteria and other phytoplankton in vivo and in situ. [Copyright &y& Elsevier]

Physical disruptions to intervertebral discs (IVDs) can cause mechanical changes that lead to degeneration and to low back pain which affects 75% of us in our lifetimes. Quantifying the effects of these changes on internal IVD strains may lead to better preventative strategies and treatments. Digital Volume Correlation (DVC) is a non-invasive technique that divides volumetric images into subsets, and measures strains by tracking the internal patterns within them under load. Applying DVC to MRIs may allow non-invasive strain measurements. However, DVC-MRI for strain measurements in IVDs has not been used previously. The purpose of this study was to quantify the strain and deformation errors associated with DVC-MRI for measurements in human IVDs. Eight human lumbar IVDs were MRI scanned (9.4 T) for a 'zero-strain study' (multiple unloaded scans to quantify noise within the system), and a loaded study (2 mm axial compression). Three DVC methodologies: Fast-Fourier transform (FFT), direct correlation (DC), and a combination of both FFT and DC approaches were compared with subset sizes ranging from 8 to 88 voxels to establish the optimal DVC methodology and settings which were then used in the loaded study. FFT + DC was the optimal method and a subset size of 56 voxels (2520 µm) was found to be a good compromise between errors and spatial resolution. Displacement and strain errors did not exceed 28 µm and 3000 microstrain, respectively. These findings demonstrate that DVC-MRI can quantify internal strains within IVDs non-invasively and accurately. The method has unique potential for assessing IVD strains within patients. [ABSTRACT FROM AUTHOR]

The crystal structure of the mineral boleite contains clusters of 24 S=1/2Cu2+ ions that have the shape of a truncated cube formed of eight trimers connected by edges. Susceptibility measurements and exact diagonalization calculations suggest that there are strong antiferromagnetic intratrimer interactions, such that effective S=1/2 degrees of freedom emerge on the trimers below T≲100 K. Weaker intertrimer interactions lead to the formation of a singlet ground state for these effective spins at T≲5 K. The clusters in boleite offer a situation similar to single molecule magnetism, accessible to both experiment and numerics, in which the interplay of quantum spins, geometric frustration, spin entanglement, and mesoscopic system size can be studied. [ABSTRACT FROM AUTHOR]

Experiment and theory indicate that UPt3 is a topological superconductor in an odd-parity state, based in part from the temperature independence of the NMR Knight shift. However, quasiparticle spin-flip scattering near a surface, where the Knight shift is measured, might be responsible. We use polarized neutron scattering to measure the bulk susceptibility with H||c, finding consistency with the Knight shift but inconsistency with theory for this field orientation. We infer that neither spin susceptibility nor a Knight shift are a reliable indication of odd parity. [ABSTRACT FROM AUTHOR]