3D printing for bio-synthetic biliary stents

Three-dimensional (3D) printing is an additive manufacturing method that holds great potential in a variety of future patient-specific medical technologies. This project validated a novel crosslinked polyvinyl alcohol (XL-PVA) 3D printed stent infused with collagen, human placental mesenchymal stem cells (PMSCs), and cholangiocytes. The biofabrication method in the present study examined 3D printing and collagen injection molding for rapid prototyping of customized living biliary stents with clinical applications in the setting of malignant and benign bile duct obstructions. XL-PVA stents showed hydrophilic swelling and addition of radiocontrast to the stent matrix improved radiographic opacity. Collagen loaded with PMSCs contracted tightly around hydrophilic stents and dense choloangiocyte coatings were verified through histology and fluorescence microscopy. It is anticipated that design elements used in these stents may enable appropriate stent placement, provide protection of the stent-stem cell matrix against bile constituents, and potentially limit biofilm development. Overall, this approach may allow physicians to create personalized bio-integrating stents for use in biliary procedures and lays a foundation for new patient-specific stent fabrication techniques

The Haldane gap for the S=2 antiferromagnetic Heisenberg chain revisited

Using the density matrix renormalization group (DMRG) technique, we carry out a large scale numerical calculation for the S=2 antiferromagnetic Heisenberg chain. Performing systematic scaling analysis for both the chain length $L$ and the number of optimal states kept in the iterations $m$, the Haldane gap $\Delta (2)$ is estimated accurately as $(0.0876\pm0.0013)J$. Our systematic analysis for the S=2 chains not only ends the controversies arising from various DMRG calculations and Monte Carlo simulations, but also sheds light on how to obtain reliable results from the DMRG calculations for other complicated systems.Comment: 4 pages and 1 figur

Altered functional resting-state hypothalamic connectivity and abnormal pituitary morphology in children with Prader-Willi syndrome

Background: Prader-Willi syndrome (PWS) is a complex neurodevelopmental disorder, characterized by endocrine problems and hyperphagia, indicating hypothalamic-pituitary dysfunction. However, few studies have explored the underlying neurobiology of the hypothalamus and its functional connectivity with other brain regions. Thus, the aim of this study was to examine the anatomical differences of the hypothalamus, mammillary bodies, and pituitary gland as well as resting state functional connectivity of the hypothalamus in children with PWS. Methods: Twenty-seven children with PWS (13 DEL, 14 mUPD) and 28 typically developing children were included. Manual segmentations by a blinded investigator were performed to determine the volumes of the hypothalamus, mammillary bodies, and pituitary gland. In addition, brain-wide functional connectivity analysis was performed using the obtained masks of the hypothalamus. Results: Children with PWS showed altered resting state functional connectivity between hypothalamus and right and left lateral occipital complex, compared to healthy controls. In addition, children with PWS had on average a 50% smaller pituitary volume, an irregular shape of the pituitary, and a longer pituitary stalk. Pituitary volume did not increase in volume during puberty in PWS. No volumetric differences in the hypothalamus and mammillary bodies were found. In all subjects, the posterior pituitary bright spot was observed. Conclusions: We report altered functional hypothalamic connectivity with lateral occipital complexes in both hemispheres, which are implicated in response to food and reward system, and absence of connectivity might therefore at least partially contribute to the preoccupation with food in PWS

Neonatal critical illness and development: white matter and hippocampus alterations in school-age neonatal ECMO survivors

Aim: Examine the neurobiology of long-term neuropsychological deficits following neonatal extracorporeal membrane oxygenation (ECMO). Method: This cross-sectional study assessed white matter integrity and hippocampal volume of ECMO survivors (8-15yrs) and healthy controls (8-17yrs) using Diffusion Tensor Imaging and structural MRI, respectively. Neuropsychological outcome was evaluated in patients. Included clinical predictors of white matter integrity: age start ECMO, ECMO duration, highest oxygenation index before ECMO, highest mean airway pressure and mechanical ventilation duration. Results: Patients (n=23) had lower global fractional anisotropy than controls (n=54)(patients=.368; controls=.381; p=.02), but similar global mean diffusivity (p=.41). Patients had lower fractional anisotropy in the left cingulum bundle (patients=.345; controls=.399; p<.001) and higher mean diffusivity in a region of the left parahippocampal cingulum (patients=.916; controls=.871; p<.001). Higher global mean diffusivity predicted worse verbal memory in patients (n=17)(β=-.74, p=.01). Patients (n=23) had smaller bilateral hippocampal volume than controls (n=43)(left: p< .001; right: p< .001). In patients, this was related to worse verbal memory (left: β=.65, p=.02; right: β=.71, p=.01). Interpretation: Neonatal ECMO survivors are at risk for long-term brain alterations, which may partly explain long-term neuropsychological impairments. Neuroimaging may contribute to better risk stratification of long-term impairments

Spin-1/2 J1-J2 model on the body-centered cubic lattice

Using exact diagonalization (ED) and linear spin wave theory (LSWT) we study the influence of frustration and quantum fluctuations on the magnetic ordering in the ground state of the spin-1/2 J1-J2 Heisenberg antiferromagnet (J1-J2 model) on the body-centered cubic (bcc) lattice. Contrary to the J1-J2 model on the square lattice, we find for the bcc lattice that frustration and quantum fluctuations do not lead to a quantum disordered phase for strong frustration. The results of both approaches (ED, LSWT) suggest a first order transition at J2/J1 $\approx$ 0.7 from the two-sublattice Neel phase at low J2 to a collinear phase at large J2.Comment: 6.1 pages 7 figure

Coronal Shock Waves, EUV waves, and their Relation to CMEs. II. Modeling MHD Shock Wave Propagation Along the Solar Surface, Using Nonlinear Geometrical Acoustics

We model the propagation of a coronal shock wave, using nonlinear geometrical acoustics. The method is based on the Wentzel-Kramers-Brillouin (WKB) approach and takes into account the main properties of nonlinear waves: i) dependence of the wave front velocity on the wave amplitude, ii) nonlinear dissipation of the wave energy, and iii) progressive increase in the duration of solitary shock waves. We address the method in detail and present results of the modeling of the propagation of shock-associated extreme-ultraviolet (EUV) waves as well as Moreton waves along the solar surface in the simplest solar corona model. The calculations reveal deceleration and lengthening of the waves. In contrast, waves considered in the linear approximation keep their length unchanged and slightly accelerate.Comment: 15 pages, 7 figures, accepted for publication in Solar Physic

Prematurity, Opioid Exposure and Neonatal Pain: Do They Affect the Developing Brain?

Background: Traditionally, 10 years ago, children born preterm often routinely received morphine, especially during mechanical ventilation. Studies in neonatal rats, whose stage of brain development roughly corresponds to that of children born preterm, found negative long-term effects after pain and opioid exposure. Objectives: We studied possible effects of prematurity, procedural pain and opioids in humans 10 years later. We hypothesized that these factors would negatively influence neurobiological, neuropsychological and sensory development later in life. Methods: We included 19 children born preterm who as neonates participated in an RCT on the short-term effects of morphine administration and who previously participated in our follow-up studies at ages 5 and 8/9 years. We assessed associations between brain morphology (n = 11), neuropsychological functioning (n = 19) and thermal sensitivity (n = 17) and prematurity, opioid exposure and neonatal pain. Results: Significant correlations (coefficients 0.60-0.85) of gestational age, number of painful procedures and morphine exposure with brain volumes were observed. Significant correlations between these factors and thermal sensitivity were not established. Neuropsychological outcome was significantly moderately correlated with morphine exposure in only two subtests, and children performed in general 'average' by Dutch norms. Conclusions: Although prematurity, opioid exposure and neonatal pain were significantly associated with brain volume, no major associations with neuropsychological functioning or thermal sensitivity were detected. Our findings suggest that morphine administration during neonatal life does not affect neurocognitive performance or thermal sensitivity during childhood in children born preterm without brain damage during early life. Future studies with larger sample sizes are needed to confirm these findings

Studies on two stage sludge digestion, 1928-29

At head of title: State of Illinois. Department of registration and education. Division of the state Water survey."Bulletins of the state water survey": 1 leaf at end."Literature cited": p. 92.Enumeration continues from preceding title

Guiding the Way to Gamma-Ray Sources: X-ray Studies of Supernova Remnants

Supernova remnants have long been suggested as a class of potential counterparts to unidentified gamma-ray sources. The mechanisms by which such gamma-rays can arise may include emission from a pulsar associated with a remnant, or a variety of processes associated with energetic particles accelerated by the SNR shock. Imaging and spectral observations in the X-ray band can be used to identify properties of the remnants that lead to gamma-ray emission, including the presence of pulsar-driven nebulae, nonthermal X-ray emission from the SNR shells, and the interaction of SNRs with dense surrounding material.Comment: 16 pages, 11 figures, To appear in the proceedings of the workshop: "The Nature of the Unidentified Galactic Gamma-Ray Sources" held at INAOE, Mexico, October 2000, (A.Carraminana, O. Reiner and D. Thompson, eds.