Crystal defects and spin tunneling in single crystals of Mn12 clusters

The question addressed in this paper is that of the influence of the density of dislocations on the spin tunneling in Mn12 clusters. We have determined the variation in the mosaicity of fresh and thermally treated single crystals of Mn12 by analyzing the widening of low angle x-ray diffraction peaks. It has also been well established from both isothermal magnetization and relaxation experiments that there is a broad distribution of tunneling rates which is shifted to higher rates when the density of dislocations increases.

Multi-Atlas based Segmentation of Head and Neck CT Images using Active Contour

This paper presents the segmentation of bilateral parotid glands in the Head and Neck (H&N) CT images using an active contour based atlas registration. We compare segmentation results from three atlas selection strategies: (i) selection of "single-most-similar" atlas for each image to be segmented, (ii) fusion of segmentation results from multiple atlases using STAPLE, and (iii) fusion of segmentation results using majority voting. Among these three approaches, fusion using majority voting provided the best results. Finally, we present a detailed evaluation on a dataset of eight images (provided as a part of H&N auto segmentation challenge conducted in conjunction with MICCAI-2010 conference) using majority voting strategy.

Recycling universe

If the effective cosmological constant is nonzero, our observable universe may enter a stage of exponential expansion. In such a case, regions of it may tunnel back to the false vacuum of an inflaton scalar field, and inflation with a high expansion rate may resume in those regions. An ideal eternal observer would then witness an infinite succession of cycles from false vacuum to true, and back. Within each cycle, the entire history of a hot universe would be replayed. If there were several minima of the inflaton potential, our ideal observer would visit each one of these minima with a frequency which depends on the shape of the potential. We generalize the formalism of stochastic inflation to analyze the global structure of the universe when this recycling process is taken into account.

The Moroccan political partisan landscape : a polarized microcosm?

Using an original investigative protocol and a data base of 4,127 national delegates from ten Moroccan political organizations, surveyed between 2008 and 2012, this article examines the characteristics of party members in Morocco. Initial results indicate that the field of Moroccan political parties is a small world dominated by city dwellers, mature men, and the most highly educated, wealthiest individuals. However, far from being isolated from ordinary citizens, there are social dynamics at work. While it cannot be reduced to a segmented clientele, it is, nonetheless, shaped by an ideal-typical opposition between parties of notables and parties of activists.

A post-processing pipeline to reconstruct the developing fetal brain using low-resolution MRI

Introduction. Development of the fetal brain surfacewith concomitant gyrification is one of the majormaturational processes of the human brain. Firstdelineated by postmortem studies or by ultrasound, MRIhas recently become a powerful tool for studying in vivothe structural correlates of brain maturation. However,the quantitative measurement of fetal brain developmentis a major challenge because of the movement of the fetusinside the amniotic cavity, the poor spatial resolution,the partial volume effect and the changing appearance ofthe developing brain. Today extensive efforts are made todeal with the âeurooepost-acquisitionâeuro reconstruction ofhigh-resolution 3D fetal volumes based on severalacquisitions with lower resolution (Rousseau, F., 2006;Jiang, S., 2007). We here propose a framework devoted tothe segmentation of the basal ganglia, the gray-whitetissue segmentation, and in turn the 3D corticalreconstruction of the fetal brain. Method. Prenatal MRimaging was performed with a 1-T system (GE MedicalSystems, Milwaukee) using single shot fast spin echo(ssFSE) sequences in fetuses aged from 29 to 32gestational weeks (slice thickness 5.4mm, in planespatial resolution 1.09mm). For each fetus, 6 axialvolumes shifted by 1 mm were acquired (about 1 min pervolume). First, each volume is manually segmented toextract fetal brain from surrounding fetal and maternaltissues. Inhomogeneity intensity correction and linearintensity normalization are then performed. A highspatial resolution image of isotropic voxel size of 1.09mm is created for each fetus as previously published byothers (Rousseau, F., 2006). B-splines are used for thescattered data interpolation (Lee, 1997). Then, basalganglia segmentation is performed on this superreconstructed volume using active contour framework witha Level Set implementation (Bach Cuadra, M., 2010). Oncebasal ganglia are removed from the image, brain tissuesegmentation is performed (Bach Cuadra, M., 2009). Theresulting white matter image is then binarized andfurther given as an input in the Freesurfer software(http://surfer.nmr.mgh.harvard.edu/) to provide accuratethree-dimensional reconstructions of the fetal brain.Results. High-resolution images of the cerebral fetalbrain, as obtained from the low-resolution acquired MRI,are presented for 4 subjects of age ranging from 29 to 32GA. An example is depicted in Figure 1. Accuracy in theautomated basal ganglia segmentation is compared withmanual segmentation using measurement of Dice similarity(DSI), with values above 0.7 considering to be a verygood agreement. In our sample we observed DSI valuesbetween 0.785 and 0.856. We further show the results ofgray-white matter segmentation overlaid on thehigh-resolution gray-scale images. The results arevisually checked for accuracy using the same principlesas commonly accepted in adult neuroimaging. Preliminary3D cortical reconstructions of the fetal brain are shownin Figure 2. Conclusion. We hereby present a completepipeline for the automated extraction of accuratethree-dimensional cortical surface of the fetal brain.These results are preliminary but promising, with theultimate goal to provide âeurooemovieâeuro of the normal gyraldevelopment. In turn, a precise knowledge of the normalfetal brain development will allow the quantification ofsubtle and early but clinically relevant deviations.Moreover, a precise understanding of the gyraldevelopment process may help to build hypotheses tounderstand the pathogenesis of several neurodevelopmentalconditions in which gyrification have been shown to bealtered (e.g. schizophrenia, autismâeuro¦). References.Rousseau, F. (2006), 'Registration-Based Approach forReconstruction of High-Resolution In Utero Fetal MR Brainimages', IEEE Transactions on Medical Imaging, vol. 13,no. 9, pp. 1072-1081. Jiang, S. (2007), 'MRI of MovingSubjects Using Multislice Snapshot Images With VolumeReconstruction (SVR): Application to Fetal, Neonatal, andAdult Brain Studies', IEEE Transactions on MedicalImaging, vol. 26, no. 7, pp. 967-980. Lee, S. (1997),'Scattered data interpolation with multilevel B-splines',IEEE Transactions on Visualization and Computer Graphics,vol. 3, no. 3, pp. 228-244. Bach Cuadra, M. (2010),'Central and Cortical Gray Mater Segmentation of MagneticResonance Images of the Fetal Brain', ISMRM Conference.Bach Cuadra, M. (2009), 'Brain tissue segmentation offetal MR images', MICCAI.

Quantitative x-ray photoelectron spectroscopy study of Al/AlOx bilayers

An x-ray photoelectron spectroscopy (XPS) analysis of Nb/Al wedge bilayers, oxidized by both plasma and natural oxidation, is reported. The main goal is to show that the oxidation state¿i.e., O:(oxidize)Al ratio¿, structure and thickness of the surface oxide layer, as well as the thickness of the metallic Al leftover, as functions of the oxidation procedure, can be quantitatively evaluated from the XPS spectra. This is relevant to the detailed characterization of the insulating barriers in (magnetic) tunnel junctions

SOIL PHOSPHORUS THRESHOLDS IN EVALUATING RISK OF ENVIRONMENTAL TRANSFER TO SURFACE WATERS IN SANTA CATARINA, BRAZIL

The State of Santa Catarina, Brazil, has agricultural and livestock activities, such as pig farming, that are responsible for adding large amounts of phosphorus (P) to soils. However, a method is required to evaluate the environmental risk of these high soil P levels. One possible method for evaluating the environmental risk of P fertilization, whether organic or mineral, is to establish threshold levels of soil available P, measured by Mehlich-1 extractions, below which there is not a high risk of P transfer from the soil to surface waters. However, the Mehlich-1 extractant is sensitive to soil clay content, and that factor should be considered when establishing such P-thresholds. The objective of this study was to determine P-thresholds using the Mehlich-1 extractant for soils with different clay contents in the State of Santa Catarina, Brazil. Soil from the B-horizon of an Oxisol with 800 g kg-1 clay was mixed with different amounts of sand to prepare artificial soils with 200, 400, 600, and 800 g kg-1 clay. The artificial soils were incubated for 30 days with moisture content at 80 % of field capacity to stabilize their physicochemical properties, followed by additional incubation for 30 days after liming to raise the pH(H2O) to 6.0. Soil P sorption curves were produced, and the maximum sorption (Pmax) was determined using the Langmuir model for each soil texture evaluated. Based on the Pmax values, seven rates of P were added to four replicates of each soil, and incubated for 20 days more. Following incubation, available P contents (P-Mehlich-1) and P dissolved in the soil solution (P-water) were determined. A change-point value (the P-Mehlich-1 value above which P-water starts increasing sharply) was calculated through the use of segmented equations. The maximum level of P that a soil might safely adsorb (P-threshold) was defined as 80 % of the change-point value to maintain a margin for environmental safety. The P-threshold value, in mg dm-3, was dependent on the soil clay content according to the model P-threshold = 40 + Clay, where the soil clay content is expressed as a percentage. The model was tested in 82 diverse soil samples from the State of Santa Catarina and was able to distinguish samples with high and low environmental risk.

Clinical picture of the amyloid arthropathy in patients with chronic renal failure maintained on haemodialysis using cellulose membranes.

The clinical picture of 15 patients (10 male, five female) with amyloid arthropathy secondary to chronic renal failure treated with haemodialysis has been studied. The average period of haemodialysis was 10.8 years. Joint symptoms appeared between three and 13 years after starting haemodialysis. No patient had renal amyloidosis. Early symptoms were varied and often overlapped: knee swelling (seven patients), painful and stiff shoulders (seven), and carpal tunnel syndrome (six) were the most prominent. Follow up showed extension to other joints. Joint effusions were generally of the non-inflammatory type. Radiologically, geodes and erosions of variable sizes were seen in the affected joints, which can develop into a destructive arthropathy. Amyloid was found in abdominal fat in three of the 12 patients on whom a needle aspiration was performed. Four of 12 patients showed changes compatible with amyloid infiltration in the echocardiogram. One patient had amyloid in the gastric muscular layer, another in the colon mucus, and two of four in rectal biopsy specimens. Amyloid deposits showed the presence of beta 2 microglobulin in 10 patients. The clinical and radiological picture was similar to the amyloid arthropathy associated with multiple myeloma. These patients can develop systemic amyloidosis.

Amyloid arthropathy in patients undergoing periodical haemodialysis for chronic renal failure: a new complication.

Seven patients (five male and two female) with chronic renal failure (CRF) treated by periodical haemodialysis presented with swelling and effusion of more than three months' duration in knees (four bilateral), shoulders (two, one of them bilateral), elbow (one), and ankle (one). Four had a carpal tunnel syndrome both clinically and electromyographically (three bilateral). All patients had hyperparathyroidism secondary to their CRF, which was not due to amyloidosis in any of them. The dialysis duration period varied from five to 14 years, with an average of 8.6 years. Amyloid deposits (Congo red positive areas with green birefringence under polarising microscopy) were shown in six of the seven synovial biopsy specimens of the knee, in five of the sediments of the synovial fluids, and in specimens removed during carpal tunnel syndrome surgery. No amyloid was found in the biopsy specimen of abdominal fat of six of the patients. The finding of amyloid only in the synovial membrane and fluid, and carpal tunnel, its absence in abdominal fat, and the lack of other manifestations of generalised amyloidosis (cardiomyopathy, malabsorption syndrome, macroglossia, etc.) and of Bence Jones myeloma (protein immunoelectrophoresis normal) raises the possibility that this is a form of amyloidosis which is peculiar to CRF treated by periodical haemodialysis.

Ulnar nerve transposition at the elbow : local anesthesia should be preferred to general anesthesia

Après la compression du nerf médian au niveau du tunnel carpien, la compression du nerf ulnaire au niveau du coude est le deuxième syndrome compressif le plus fréquent des nerfs périphériques. La chirurgie des nerfs périphériques consiste dans une décompression nerveuse et est caractérisée par un suivi post¬opératoire parfois très douloureux avec des douleurs qui peuvent chroniciser si insuffisamment traitées. Le traitement chirurgical de décompression nerveuse se fait traditionnellement sous anesthésie générale ou régionale. Une analgésie post-opératoire plus efficace et durable avec moindre risque de chronicisation avait justifié ce choix jusqu'à ce jour. Grâce au développement de la chirurgie ambulatoire ces dernières années, un grand nombre d'interventions chirurgicales au niveau de la main sont effectués sous anesthésie locale. Au vu d'une meilleure connaissance de cette technique d'anesthésie, son rôle dans la chirurgie des nerfs périphériques a été remis en question. Alors que plusieurs études ont démontré que l'anesthésie locale est aussi efficace que l'anesthésie générale et régionale au sujet de la chirurgie du tunnel carpien, son utilisation pour la chirurgie du nerf ulnaire reste peu connue. La raison de l'hésitation à l'utilisation de l'anesthésie locale pour le traitement du tunnel ulnaire est due au fait que dans plus de la moitié des cas, une simple décompression n'est pas suffisante et qu'il est souvent nécessaire de transposer le nerf ulnaire devant l'épicondyle ulnaire. La seule publication disponible au sujet de l'utilisation de l'anesthésie locale dans le traitement du tunnel ulnaire considère comme irréalisable d'utiliser cette méthode dans le cas d'une transposition. Malgré cette mise en garde, nous avons, depuis plusieurs années, des excellents résultats avec la transposition du nerf ulnaire sous anesthésie locale. Avec le but d'objectiver notre expérience dans ce domaine nous avons souhaité analyser nos résultats de façon rétrospective avec particulière attention aux douleurs post-opératoires et à la satisfaction des patients. Les dossiers de cinquante patients Consécutifs (26F, 24M) opérés par le même chirurgien dans notre service de 2002 à 2012 ont été analysés rétrospectivement. Les critères suivants ont été récoltés: l'âge du patient, la profession, la main dominante, les détails des techniques opératoires utilisées, le type d'anesthésie, l'intensité du suivi ainsi que les complications, le niveau de douleur dans l'immédiat post-opératorie ainsi que à une année de l'intervention. Les patients ont été divisés en 4 groupes: les opérés sous anesthésie générale avec transposition du nerf (n=17) ou sans transposition (n=10) et les opérés sous anesthésie locale avec transposition (n=12) ou sans transposition (n=11). Au premier jour la douleur était comparable dans tous les groupes. A une semaine, elle était deux fois plus importante lorsque la transposition avait été réalisée sous anesthésie générale par rapport à si une anesthésie locale avait été effectuée (p=0.03). La satisfaction s'est révélée plus élevée mais non significative chez les patients opérés sous anesthésie locale. Ces derniers étaient significativement plus enclins à répéter la chirurgie comparé a ceux opérés sous anesthésie générale (p=0.04). En conclusion, les résultats de cette étude suggèrent que l'anesthésie locale est au moins autant efficace que l'anesthésie générale en termes de complications et de douleurs post-opératoires indépendamment du fait qu'une transposition nerveuse soit effectuée ou pas. Un meilleur contrôle des douleurs à une semaine post-opératoire a contribué à une haute satisfaction des patients de notre étude.

Spectrally selective B1-insensitive T2 magnetization preparation sequence.

A T(2) magnetization-preparation (T(2) Prep) sequence is proposed that is insensitive to B(1) field variations and simultaneously provides fat suppression without any further increase in specific absorption rate (SAR). Increased B(1) inhomogeneity at higher magnetic field strength (B(0) > or = 3T) necessitates a preparation sequence that is less sensitive to B(1) variations. For the proposed technique, T(2) weighting in the image is achieved using a segmented B(1)-insensitive rotation (BIR-4) adiabatic pulse by inserting two equally long delays, one after the initial reverse adiabatic half passage (AHP), and the other before the final AHP segment of a BIR-4 pulse. This sequence yields T(2) weighting with both B(1) and B(0) insensitivity. To simultaneously suppress fat signal (at the cost of B(0) insensitivity), the second delay is prolonged so that fat accumulates additional phase due to its chemical shift. Numerical simulations as well as phantom and in vivo image acquisitions were performed to show the efficacy of the proposed technique.

Pieces of Iowa’s Past, February 27, 2008

Pieces of Iowa’s Past, published by the Iowa State Capitol Tour Guides weekly during the legislative session, features historical facts about Iowa, the Capitol, and the early workings of state government. All historical publications are reproduced here with the actual spelling, punctuation, and grammar retained. February 27, 2008 THIS WEEK: Tunnel of Progress

Coronary magnetic resonance angiography in adolescents and young adults with kawasaki disease.

BACKGROUND: In patients with Kawasaki disease, serial evaluation of the distribution and size of coronary artery aneurysms (CAA) is necessary for risk stratification and therapeutic management. Although transthoracic echocardiography is often sufficient for this purpose initially, visualization of the coronary arteries becomes progressively more difficult as children grow. We sought to prospectively compare coronary magnetic resonance angiography (MRA) and x-ray coronary angiography findings in patients with CAA caused by Kawasaki disease. METHODS AND RESULTS: Six subjects (age 10 to 25 years) with known CAA from Kawasaki disease underwent coronary MRA using a free-breathing T2-prepared 3D bright blood segmented k-space gradient echo sequence with navigator gating and tracking. All patients underwent x-ray coronary angiography within a median of 75 days (range, 1 to 359 days) of coronary MRA. There was complete agreement between MRA and x-ray angiography in the detection of CAA (n=11), coronary artery stenoses (n=2), and coronary occlusions (n=2). Excellent agreement was found between the 2 techniques for detection of CAA maximal diameter (mean difference=0.4 +/- 0.6 mm) and length (mean difference=1.4 +/- 1.6 mm). The 2 methods showed very similar results for proximal coronary artery diameter (mean difference=0.2 +/- 0.5 mm) and CAA distance from the ostia (mean difference=0.1 +/- 1.5 mm). CONCLUSION: Free-breathing 3D coronary MRA accurately defines CAA in patients with Kawasaki disease. This technique may provide a non-invasive alternative when transthoracic echocardiography image quality is insufficient, thereby reducing the need for serial x-ray coronary angiography in this patient group.

Web decoration of Micrathena sexpinosa (Araneae: Araneidae): a frame-web-choice experiment with stingless bees

The function of silk web decorations in orb weaving spiders has been debated for decades. The most accepted hypothesized functions are that web decorations I) provide camouflage against predators, 2) are an advertisement for vertebrates to avoid web damage, or 3) increase the attraction of prey to the web. Most studies have focused on only a few genera, Argiope being the most common. In this study, I evaluated the prey attraction hypothesis of silk decorations for a species of a poorly studied genus in this topic, Micrathena sexpinosa Hahn 1822. I used a web-choice experiment in which I presented empty or web-bearing frames at the end of a tunnel to stingless bees (Tetragonisca angustula). This frame-choice experiment consisted of the following comparisons: decorated web vs. empty frame, decorated web vs. undecorated web, and undecorated web vs. empty frame. Webs with decoration intercepted significantly more bees than empty frames and undecorated webs. Therefore, the decorations of Micrathena sexpinosa might play a role in increasing foraging success.