The Effect Of Misleading Prior Information On The Subjective Visual Vertical

When tilted sideways participants misperceive the visual vertical assessed by means of a luminous line in otherwise complete dark- ness. A recent modeling approach (De Vrijer et al., 2009) claimed that these typical patterns of errors (known as A- and E-effects) could be explained by as- suming that participants behave in a Bayes optimal manner. In this study, we experimentally manipulate participants’ prior information about body-in-space orientation and measure the effect of this manipulation on the subjective visual vertical (SVV). Specifically, we explore the effects of veridical and misleading instructions about body tilt orientations on the SVV. We used a psychophys- ical 2AFC SVV task at roll tilt angles of 0 degrees, 16 degrees and 4 degrees CW and CCW. Participants were tilted to 4 degrees under different instruction conditions: in one condition, participants received veridical instructions as to their tilt angle, whereas in another condition, participants received the mis- leading instruction that their body position was perfectly upright. Our results indicate systematic differences between the instruction conditions at 4 degrees CW and CCW. Participants did not simply use an ego-centric reference frame in the misleading condition; instead, participants’ estimates of the SVV seem to lie between their head’s Z-axis and the estimate of the SVV as measured in the veridical condition. All participants displayed A-effects at roll tilt an- gles of 16 degrees CW and CCW. We discuss our results in the context of the Bayesian model by De Vrijer et al. (2009), and claim that this pattern of re- sults is consistent with a manipulation of precision of a prior distribution over body-in-space orientations. Furthermore, we introduce a Bayesian Generalized Linear Model for estimating parameters of participants’ psychometric function, which allows us to jointly estimate group level and individual level parameters under all experimental conditions simultaneously, rather than relying on the traditional two-step approach to obtaining group level parameter estimates.

Twelve percent of hips with a primary cam deformity exhibit a slip-like morphology resembling sequelae of slipped capital femoral epiphysis

BACKGROUND In some hips with cam-type femoroacetabular impingement (FAI), we observed a morphology resembling a more subtle form of slipped capital femoral epiphysis (SCFE). Theoretically, the morphology in these hips should differ from hips with a primary cam-type deformity. QUESTIONS/PURPOSES We asked if (1) head-neck offset; (2) epiphyseal angle; and (3) tilt angle differ among hips with a slip-like morphology, idiopathic cam, hips after in situ pinning of SCFE, and normal hips; and (4) what is the prevalence of a slip-like morphology among cam-type hips? METHODS We retrospectively compared the three-dimensional anatomy of hips with a slip-like morphology (29 hips), in situ pinning for SCFE (eight hips), idiopathic cam deformity (171 hips), and 30 normal hips using radial MRI arthrography. Normal hips were derived from 17 asymptomatic volunteers. All other hips were recruited from a series of 277 hips (243 patients) seen at a specialized academic hip center between 2006 and 2010. Forty-one hips with isolated pincer deformity were excluded. Thirty-six of 236 hips had a known cause of cam impingement (secondary cam), including eight hips after in situ pinning of SCFE (postslip group). The 200 hips with a primary cam were separated in hips with a slip-like morphology (combination of positive fovea sign [if the neck axis did not intersect with the fovea capitis] and a tilt angle [between the neck axis and perpendicular to the basis of the epiphysis] exceeding 4°) and hips with an idiopathic cam. We evaluated offset ratio, epiphyseal angle (angle between the neck axis and line connecting the center of the femoral head and the point where the physis meets the articular surface), and tilt angle circumferentially around the femoral head-neck axis. Prevalence of slip-like morphology was determined based on the total of 236 hips with cam deformities. RESULTS Offset ratio was decreased anterosuperiorly in idiopathic cam, slip-like, and postslip (eg, 1 o'clock position with a mean offset ranging from 0.00 to 0.14; p < 0.001 for all groups) compared with normal hips (0.25 ± 0.06 [95% confidence interval, 0.13-0.37]) and increased posteroinferiorly in slip-like (eg, 8 o'clock position, 0.5 ± 0.09 [0.32-0.68]; p < 0.001) and postslip groups (0.55 ± 0.12 [0.32-0.78]; p < 0.001) and did not differ in idiopathic cam (0.32 ± 0.09 [0.15-0.49]; p = 0.323) compared with normal (0.31 ± 0.07 [0.18-0.44]) groups. Epiphyseal angle was increased anterosuperiorly in the slip-like (eg, 1 o'clock position, 70° ± 9° [51°-88°]; p < 0.001) and postslip groups (75° ± 13° [49°-100°]; p = 0.008) and decreased in idiopathic cam (50° ± 8° [35°-65°]; p < 0.001) compared with normal hips (58° ± 8° [43°-74°]). Posteroinferiorly, epiphyseal angle was decreased in slip-like (eg, 8 o'clock position, 54° ± 10° [34°-74°]; p < 0.001) and postslip (44° ± 11° [23°-65°]; p < 0.001) groups and did not differ in idiopathic cam (76° ± 8° [61°-91°]; p = 0.099) compared with normal (73° ± 7° [59°-88°]) groups. Tilt angle increased in slip-like (eg, 2/8 o'clock position, 14° ± 8° [-1° to 30°]; p < 0.001) and postslip hips (29° ± 10° [9°-48°]; p < 0.001) and decreased in hips with idiopathic cam (-7° ± 5° [-17° to 4°]; p < 0.001) compared with normal (-1° ± 5° [-10° to 8°]) hips. The prevalence of a slip-like morphology was 12%. CONCLUSIONS The slip-like morphology is the second most frequent pathomorphology in hips with primary cam deformity. MRI arthrography of the hip allows identifying a slip-like morphology, which resembles hips after in situ pinning of SCFE and distinctly differs from hips with idiopathic cam. These results support previous studies reporting that SCFE might be a risk factor for cam-type FAI.

Experimental and Theoretical Electron Density Analysis of Copper Pyrazine Nitrate Quasi-Low-Dimensional Quantum Magnets

The accurate electron density distribution and magnetic properties of two metal-organic polymeric magnets, the quasi-one-dimensional (1D) Cu(pyz)(NO3)2 and the quasi-two-dimensional (2D) [Cu(pyz)2(NO3)]NO3·H2O, have been investigated by high-resolution single-crystal X-ray diffraction and density functional theory calculations on the whole periodic systems and on selected fragments. Topological analyses, based on quantum theory of atoms in molecules, enabled the characterization of possible magnetic exchange pathways and the establishment of relationships between the electron (charge and spin) densities and the exchange-coupling constants. In both compounds, the experimentally observed antiferromagnetic coupling can be quantitatively explained by the Cu-Cu superexchange pathway mediated by the pyrazine bridging ligands, via a σ-type interaction. From topological analyses of experimental charge-density data, we show for the first time that the pyrazine tilt angle does not play a role in determining the strength of the magnetic interaction. Taken in combination with molecular orbital analysis and spin density calculations, we find a synergistic relationship between spin delocalization and spin polarization mechanisms and that both determine the bulk magnetic behavior of these Cu(II)-pyz coordination polymers.

Pulse-front tilt for short-wavelength lasing by means of traveling-wave plasma-excitation

Generation of coherent short-wavelength radiation across a plasma column is dramatically improved under traveling-wave excitation (TWE). The latter is optimized when its propagation is close to the speed of light, which implies small-angle target-irradiation. Yet, short-wavelength lasing needs large irradiation angles in order to increase the optical penetration of the pump into the plasma core. Pulse-front back-tilt is considered to overcome such trade-off. In fact, the TWE speed depends on the pulse-front slope (envelope of amplitude), whereas the optical penetration depth depends on the wave-front slope (envelope of phase). Pulse-front tilt by means of compressor misalignment was found effective only if coupled with a high-magnification front-end imaging/focusing component. It is concluded that speed matching should be accomplished with minimal compressor misalignment and maximal imaging magnification.

Which Radiographic Hip Parameters Do Not Have to Be Corrected for Pelvic Rotation and Tilt?

Background Acetabular anatomy on AP pelvic radiographsdepends on pelvic orientation during radiograph acquisition. However, not all parameters may change to a clinically relevant degree with differences in pelvic orientation. This issue may influence the diagnosis of acetabular pathologies and planning of corrective acetabular surgery (reorientation or rim trimming). However, to this point, it has not been well characterized. Questions/purposes We asked (1) which radiographic parameters change in a clinical setting when normalized to neutral pelvic orientation; (2) which parameters do not change in an experimental setting when the pelvis is experimentally rotated/tilted; and (3) which of these changes are ‘‘ultimately’’ relevant based on a prespecified definition of relevance. Methods In a clinical setup, 11 hip parameters were evaluated in 101 patients (126 hips) by two observers and the interobserver difference was calculated. All parameters were normalized to an anatomically defined neutral pelvic orientation with the help of a lateral pelvic radiograph and specific software. Differences between nonnormalized and normalized values were calculated (effect of normalization). In an experimental setup involving 20 cadaver pelves (40 hips), the maximum range for each parameter was computed with the pelvis rotated (range, −12° to 12°) and tilted (range, −24° to 24°). ‘‘Ultimately’’ relevant changes existed if the effect of normalization exceeded the interobserver difference (eg, 37% versus 6% for prevalence of a positive crossover sign) and/or the maximum experimental range exceeded 1 SD of interobserver difference (eg, 27% versus 6% for anterior acetabular coverage). Results In the clinical setup, all parameters except the ACM angle and craniocaudal acetabular coverage changed when being normalized, eg, effect of normalization for lateral center-edge angle, acetabular index, and sharp angle ranged from −5° to 4° (p values < 0.029). In the experimental setup, five parameters showed no major changes, whereas six parameters did change (all p values < 0.001). Ultimately relevant changes were found for anteroposterior acetabular coverage, retroversion index, and prevalence of a positive crossover or posterior wall sign. Conclusions Lateral center-edge angle, ACM angle, Sharp angle, acetabular and extrusion index, and craniocaudal acetabular coverage showed no relevant changes with varying pelvic orientation and can therefore be acquired independent from individual pelvic tilt and rotation in clinical practice. In contrast, anteroposterior acetabular coverage, crossover and posterior wall sign, and retroversion index call for specific efforts that address individual pelvic orientation such as computer-assisted evaluation of radiographs. Level of Evidence Level III, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

The ischial spine sign: does pelvic tilt and rotation matter?

Although the ischial spine sign (ISS) has been advocated to detect acetabular retroversion, it is unknown whether the sign is valid on anteroposterior (AP) pelvic radiographs with tilted or rotated pelves. We therefore evaluated reliability of the ISS as a tool for diagnosing acetabular retroversion in the presence of considerable pelvic tilt and/or malrotation. We obtained radiographs of 20 cadaver pelves in 19 different malorientations resulting in 380 pelvis images (760 hips) for evaluation. In addition, 129 clinical radiographs of patients' hips that had varying pelvis orientations were reviewed. We found an overall sensitivity of 81% (90%), specificity of 70% (71%), positive predictive value of 77% (80.7%), and negative predictive value of 75% (85%) in the cadaver (patient) hips. Our data suggest the ISS is a valid tool for diagnosing acetabular retroversion on plain radiographs taken using a standardized technique regardless of the degree of pelvic tilt and rotation.

A study of progress of labour using intrapartum translabial ultrasound, assessing head station, direction, and angle of descent

Intrapartum translabial ultrasound (ITU) has the potential to objectively and quantitatively assess the progress of labour. The relationships between the different ITU parameters and their development during normal term labour have not been studied.

Investigation of different apple cultivars by high resolution magic angle spinning NMR. A feasibility study

(1)H HR-MAS NMR spectroscopy was applied to apple tissue samples deriving from 3 different cultivars. The NMR data were statistically evaluated by analysis of variance (ANOVA), principal component analysis (PCA), and partial least-squares-discriminant analysis (PLS-DA). The intra-apple variability of the compounds was found to be significantly lower than the inter-apple variability within one cultivar. A clear separation of the three different apple cultivars could be obtained by multivariate analysis. Direct comparison of the NMR spectra obtained from apple tissue (with HR-MAS) and juice (with liquid-state HR NMR) showed distinct differences in some metabolites, which are probably due to changes induced by juice preparation. This preliminary study demonstrates the feasibility of (1)H HR-MAS NMR in combination with multivariate analysis as a tool for future chemometric studies applied to intact fruit tissues, e.g. for investigating compositional changes due to physiological disorders, specific growth or storage conditions.

Advanced morphological 3D magnetic resonance observation of cartilage repair tissue (MOCART) scoring using a new isotropic 3D proton-density, turbo spin echo sequence with variable flip angle distribution (PD-SPACE) compared to an isotropic 3D steady-state free precession sequence (True-FISP) and standard 2D sequences

To evaluate a new isotropic 3D proton-density, turbo-spin-echo sequence with variable flip-angle distribution (PD-SPACE) sequence compared to an isotropic 3D true-fast-imaging with steady-state-precession (True-FISP) sequence and 2D standard MR sequences with regard to the new 3D magnetic resonance observation of cartilage repair tissue (MOCART) score.

Effects of enamel abrasion, salivary pellicle, and measurement angle on the optical assessment of dental erosion

The present study assessed the effects of abrasion, salivary proteins, and measurement angle on the quantification of early dental erosion by the analysis of reflection intensities from enamel. Enamel from 184 caries-free human molars was used for in vitro erosion in citric acid (pH 3.6). Abrasion of the eroded enamel resulted in a 6% to 14% increase in the specular reflection intensity compared to only eroded enamel, and the reflection increase depended on the erosion degree. Nevertheless, monitoring of early erosion by reflection analysis was possible even in the abraded eroded teeth. The presence of the salivary pellicle induced up to 22% higher reflection intensities due to the smoothing of the eroded enamel by the adhered proteins. However, this measurement artifact could be significantly minimized (p<0.05) by removing the pellicle layer with 3% NaOCl solution. Change of the measurement angles from 45 to 60 deg did not improve the sensitivity of the analysis at late erosion stages. The applicability of the method for monitoring the remineralization of eroded enamel remained unclear in a demineralization/remineralization cycling model of early dental erosion in vitro.

Exploring High-resolution Magic Angle Spinning (HR-MAS) NMR Spectroscopy for Metabonomic Analysis of Apples

Classical liquid-state high-resolution (HR) NMR spectroscopy has proved a powerful tool in the metabonomic analysis of liquid food samples like fruit juices. In this paper the application of (1)H high-resolution magic angle spinning (HR-MAS) NMR spectroscopy to apple tissue is presented probing its potential for metabonomic studies. The (1)H HR-MAS NMR spectra are discussed in terms of the chemical composition of apple tissue and compared to liquid-state NMR spectra of apple juice. Differences indicate that specific metabolic changes are induced by juice preparation. The feasibility of HR-MAS NMR-based multivariate analysis is demonstrated by a study distinguishing three different apple cultivars by principal component analysis (PCA). Preliminary results are shown from subsequent studies comparing three different cultivation methods by means of PCA and partial least squares discriminant analysis (PLS-DA) of the HR-MAS NMR data. The compounds responsible for discriminating organically grown apples are discussed. Finally, an outlook of our ongoing work is given including a longitudinal study on apples.