Genetic Manipulation of Iron Biomineralization Enhances MR Relaxivity in a Ferritin-M6A Chimeric Complex

Ferritin has gained significant attention as a potential reporter gene for in vivo imaging by magnetic resonance imaging (MRI). However, due to the ferritin ferrihydrite core, the relaxivity and sensitivity for detection of native ferritin is relatively low. We report here on a novel chimeric magneto-ferritin reporter gene – ferritin-M6A – in which the magnetite binding peptide from the magnetotactic bacteria magnetosome-associated Mms6 protein was fused to the C-terminal of murine h-ferritin. Biophysical experiments showed that purified ferritin-M6A assembled into a stable protein cage with the M6A protruding into the cage core, enabling magnetite biomineralisation. Ferritin-M6A-expressing C6-glioma cells showed enhanced (per iron) r2 relaxivity. MRI in vivo studies of ferritin-M6A-expressing tumour xenografts showed enhanced R2 relaxation rate in the central hypoxic region of the tumours. Such enhanced relaxivity would increase the sensitivity of ferritin as a reporter gene for non-invasive in vivo MRI-monitoring of cell delivery and differentiation in cellular or gene-based therapies

Dysregulation of Dicer1 in Beta Cells Impairs Islet Architecture and Glucose Metabolism

microRNAs (miRNAs) play important roles in pancreas development and in regulation of insulin expression in the adult. Here we show that loss of miRNAs activity in beta-cells during embryonic development results in lower beta-cell mass and in impaired glucose tolerance. Dicer1-null cells initially constitute a significant portion of the total beta-cell population. However, during postnatal development, Dicer1-null cells are depleted. Furthermore, wild-type beta cells are repopulating the islets in complex compensatory dynamics. Because loss of Dicer1 is also associated with changes in the distribution of membranous E-cadherin, we hypothesized that E-cadherin activity may play a role in beta cell survival or islet architecture. However, genetic loss of E-cadherin function does not impair islet architecture, suggesting that miRNAs likely function through other or redundant effectors in the endocrine pancreas

US Cosmic Visions: New Ideas in Dark Matter 2017: Community Report

This white paper summarizes the workshop "U.S. Cosmic Visions: New Ideas in Dark Matter" held at University of Maryland on March 23-25, 2017.Comment: 102 pages + reference

Assessing China's Engagement in the Middle East: Emerging Power Transition?

本研究主要探討中國如何介入中東地區，並且檢視其多重戰略操作現況，其中包括了安全議題、能源議題、以及經貿議題。透過中國藉由上述議題介入中東事務的發展，本研究期望能呈現中國的中東外交政策及其未來發展趨勢。本研究以中國與美國兩強是否會在中東地區發生權力轉移的可能作為研究問題，有鑑於此，本研究以AFK Organski的權力轉移理論作為全文的概念化基礎，並且重新檢視權力轉移理論在近年來的發展與實踐。就此，本研究將回應下列幾個問題:中國的中東外交政策之主要戰略目的為何?此一政策在中國全方位外交政策中的權重與定位為何?中國與中東國家的交往及雙邊關係中，所具備的優勢與劣勢為何?從結構層次來說，中國與美國在中東是否將達到權力平衡的局面?最後，中國是否滿意現階段自身在中東的地位以及中東地緣政治本身的現況?又或者中國傾向改變中東現狀，並且有意取代美國。本研究透過對上述問題的重新檢視，發現如果中國在中東所介入的勢力與議題越廣泛，並且以挑戰美國霸權為前提全力推進中國的中東介入政策，這意味著中東的現狀與規則將會被調整與改變，進而產生權力轉移的情況。不過，中國現階段並未有意、有能力挑戰美國在中東的戰略地位，因為這將使得中國與美國的結構性矛盾導向衝突。This study aims at examining the different aspects of China’s involvement in the Middle East: security, energy and economy, in the context of its evolving foreign policy and changing international status. The main question of the research is whether a power transition between the US and China is possible in the region of the Middle East. Hence. The power transition theory developed by AFK Organski in the 1950s is the basis of this research. The main question is answered by several secondary questions: What is China's foreign policy in the Middle East, and how does it combine into its overall foreign policy; What are the strong points as opposed to the weak points of China's relations with Middle Eastern countries; Is China on the course of achieving parity with the US in the region of Middle East? And the last one, is China satisfied with its current role in the Middle East and the regional existing order, or it would like to alter it in order for it to be able to replace the US as the hegemonic power in the area. If China is indeed becoming more powerful in the area and is challenging the American hegemony, the transformation of the current order and accepted rules of the games in the region could be changed to accommodate China’s needs, and this might lead to tension between China and the US or even conflicts

Improved Formability of Mg-AZ80 Alloy under a High Strain Rate in Expanding-Ring Experiments

Magnesium alloys offer a favored alternative to steels and aluminum alloys due to their low density and relatively high specific strength. Their application potentials are, however, impeded by poor formability at room temperature. In the current work, improved formability for the commercial magnesium AZ80 alloy was attained through the application of the high-rate electro-magnetic forming (EMF) technique. With the EMF system, elongation of 0.2 was achieved while only 0.11 is obtained through quasistatic loading. Systematic microstructural and textural investigations prior, during and post deformation under high strain-rate experiments were carried out using electron back-scattered diffraction (EBSD) and other microscopic techniques. The analysis indicates that enhanced elongation is achieved as a result of the combination of deformation, comprising basal and non-basal slip systems, twinning and dynamic recrystallization. An adopted EMF-forming technique is tested which results in enhanced elongation without failure and a higher degree of dynamically annealed microstructure

Design and test of a reverse osmosis pressure cell for in-situ small-angle neutron scattering studies

We introduce a new method for real-time studies of membrane scaling and biofouling on thin film composite membranes (TFC) in reverse osmosis and nanofiltration water treatment using in-situ small-angle neutron scattering (SANS). SANS delivers information on nano and microscopic structures that support the interpretation of relevant engineering parameters such as membrane permeability and water flux. A flow cell high pressure SANS is described, followed by SANS characterization of TFC membranes finding ~ 0.5 μm large cavities and ~ 300 Å diameter large rod-like cavities inside the non-woven polyester and micro-porous polysulfone layer, respectively. In-situ desalination experiments in cross-flow mode at an applied pressure of 6 bars and feed flow velocity of 0.2 cm/s are followed. The scattering cross-section times sample thickness (μt = Σt × DS) derived from the transmission coefficient shows an overall enhancement due to newly formed scattering centers which is accompanied by a reduced membrane permeability measured simultaneously. This observation is supported by enhanced scattering of the membrane due to μm large domains of mass fractal structure. The addition of the protein BSA to the feed after desalination of 30 h effectuates strong enhancement of the permeability accompanied by a about a 50% decline of μm large scattering centers

Silica Fouling in Reverse Osmosis Systems–Operando Small-Angle Neutron Scattering Studies

We present operando small-angle neutron scattering (SANS) experiments on silica fouling at two reverse osmose (RO) membranes under almost realistic conditions of practiced RO desalination technique. To its realization, two cells were designed for pressure fields and tangential feed cross-flows up to 50 bar and 36 L/h, one cell equipped with the membrane and the other one as an empty cell to measure the feed solution in parallel far from the membrane. We studied several aqueous silica dispersions combining the parameters of colloidal radius, volume fraction, and ionic strength. A relevant result is the observation of Bragg diffraction as part of the SANS scattering pattern, representing a crystalline cake layer of simple cubic lattice structure. Other relevant parameters are silica colloidal size and volume fraction far from and above the membrane, as well as the lattice parameter of the silica cake layer, its volume fraction, thickness, and porosity in comparison with the corresponding permeate flux. The experiments show that the formation of cake layer depends to a large extent on colloidal size, ionic strength and cross-flow. Cake layer formation proved to be a reversible process, which could be dissolved at larger cross-flow. Only in one case we observed an irreversible cake layer formation showing the characteristics of an unstable phase transition. We likewise observed enhanced silica concentration and/or cake formation above the membrane, giving indication of a first order liquid–solid phase transformation