Ultrasmall Water‐Soluble and Biocompatible Magnetic Iron Oxide Nanoparticles as Positive and Negative Dual Contrast Agents

Monodispersed water‐soluble and biocompatible ultrasmall magnetic iron oxide nanoparticles (UMIONs, D = 3.3 ± 0.5 nm) generated from a high‐temperature coprecipitation route are successfully used as efficient positive and negative dual contrast agents of magnetic resonance imaging (MRI). Their longitudinal relaxivity at 4.7 T (r₁ = 8.3 mM^?1 s^?1) is larger than that of clinically used T₁‐positive agent Gd‐DTPA (r₁ = 4.8 mM^?1 s^?1), and three times that of commercial contrast agent SHU‐555C (r₁ = 2.9 mM^?1 s^?1). The transversal relaxivity (r₂ = 35.1 mM^?1 s^?1) is six times that of Gd‐DTPA (r₂ = 5.3 mM^?1 s^?1), half of SHU‐555C (r₂ = 69 mM^?1 s^?1). The in vivo results show that the liver signal from T₁‐weighted MRI is positively enhanced 26%, and then negatively decreased 20% after injection of the iron oxide nanoparticles, which is stronger than those obtained from Gd‐DTPA (<10%) using the same dosage. The kidney signal is positively enhanced up to 35%, similar to that obtained from Gd‐DTPA. Under T₂‐weighted conditions, the liver signal is negatively enhanced ?70%, which is significantly higher than that from Gd‐DTPA (?6%). These results demonstrate the great potential of the UMIONs in dual contrast agents, especially as an alternative to Gd‐based positive contrast agents, which have risks of inducing side effects in patients.     

Chasing the Bad News: An Analysis of 2005 Iraq and Afghanistan War Coverage on NBC and Fox News Channel

This study analyzes all stories aired on NBC Nightly News and Fox News Channel's Special Report With Brit Hume during 2005 about the U.S. wars in Iraq and Afghanistan, and compares that coverage with real‐world indicators to address an important question: Did the news media over‐report bad news from these conflicts, as claimed by the Bush administration and as one might expect given research into the press' negativity bias? This study finds that while both channels focused a fair amount on negative storylines, overall the news actually underplayed bad news from both countries. Fox News was much more sympathetic to the administration than NBC, suggesting that scholars should consider Fox as alternative, rather than mainstream, media.     

Self-Assembled Perovskite Nanoislands on CH3NH3PbI3 Cuboid Single Crystals by Energetic Surface Engineering

Organometal perovskite single crystals have been recognized as a promising platform for high-performance optoelectronic devices, featuring high crystallinity and stability. However, a high trap density and structural nonuniformity at the surface have been major barriers to the progress of single crystal-based optoelectronic devices. Here, the formation of a unique nanoisland structure is reported at the surface of the facet-controlled cuboid MAPbI₃ (MA = CH₃NH₃⁺) single crystals through a cation interdiffusion process enabled by energetically vaporized CsI. The interdiffusion of mobile ions between the bulk and the surface is triggered by thermally activated CsI vapor, which reconstructs the surface that is rich in MA and CsI with reduced dangling bonds. Simultaneously, an array of Cs-Pb-rich nanoislands is constructed on the surface of the MAPbI₃ single crystals. This newly reconstructed nanoisland surface enhances the light absorbance over 50% and increases the charge carrier mobility from 56 to 93 cm² V⁻¹ s⁻¹. As confirmed by Kelvin probe force microscopy, the nanoislands form a gradient band bending that prevents recombination of excess carriers, and thus, enhances lateral carrier transport properties. This unique engineering of the single crystal surface provides a pathway towards developing high-quality perovskite single-crystal surface for optoelectronic applications.     

Electrolyte‐Gated n‐Type Transistors Produced from Aqueous Inks of WS2 Nanosheets

Solution‐processed, low cost thin films of layered semiconductors such as transition metal dichalcogenides (TMDs) are potential candidates for future printed electronics. Here, n‐type electrolyte‐gated transistors (EGTs) based on porous WS₂ nanosheet networks as the semiconductor are demonstrated. The WS₂ nanosheets are liquid phase exfoliated to form aqueous/surfactant stabilized inks, and deposited at low temperatures (T < 120 °C) in ambient atmosphere by airbrushing. No solvent exchange, further additives, or complicated processing steps are required. While the EGTs are primarily n‐type (electron accumulation), some hole transport is also observable. The EGTs show current modulations > 10⁴ with low hysteresis, channel width‐normalized on‐conductances of up to 0.27 µS µm^?1 and estimated electron mobilities around 0.01 cm² V^?1 s^?1. In addition, the WS₂ nanosheet networks exhibit relatively high volumetric capacitance values of 30 F cm^?3. Charge transport within the network depends significantly on the applied lateral electric field and is thermally activated, which supports the notion that hopping between nanosheets is a major limiting factor for these networks and their future application.     

An Analysis of SAFER

We investigate some of the algebraic properties of the SAFER block cipher when the message space is considered as a Z -module. In particular, we consider the invariant Z -submodules of the PHT layer and show how these invariant Z -submodules give potential cryptographic weaknesses. Received 12 June 1995 and revised 22 July 1997     

Photoinduced Proton Transfer between Photoacid and pH‐Sensitive Dyes: Influence Factors and Application for Visible‐Light‐Responsive Rewritable Paper

Ink‐free printing based on rewritable paper is an efficient and environmental friendly way to reuse paper, protect resources, and save energy for sustainable development of human society. Among various kinds of rewritable media, light responsive rewritable paper (LRP) is one of the most popular research areas due to its clean and favorable noncontact writing. Visible light is more suitable for LRP for its superior penetration and much less damages to organic molecules than UV light. However, visible‐light‐responsive rewritable paper (VLRP) has only limited successes so far. Herein, a VLRP is newly designed and fabricated based on photoinduced proton transfer (PPT) between photoacid and pH‐sensitive dyes. Success of it is highly benefited from systematical investigation and in‐depth understanding on the key influence factors, such as concentration‐induced undesired isomerization, temperature, humidity, and light intensity, on the PPT and its inverse process. As‐prepared VLRP shows long‐awaited properties, such as, high color contrast and resolution, appropriate legible time of prints, excellent reversibility (>100 cycles), easiness to achieve multicolor prints, and agreeing well with environmental concept of green printing. In addition, study of influence factors on PPT in this work, to some extent, may also help people understand complex photocycle process in biosystem.     

Biocompatible Electromechanical Actuators Composed of Silk‐Conducting Polymer Composites

Single‐component, metal‐free, biocompatible, electromechanical actuator devices are fabricated using a composite material composed of silk fibroin and poly(pyrrole) (PPy). Chemical modification techniques are developed to produce free‐standing films with a bilayer‐type structure, with unmodified silk on one side and an interpenetrating network (IPN) of silk and PPy on the other. The IPN formed between the silk and PPy prohibits delamination, resulting in a durable and fully biocompatible device. The electrochemical stability of these materials is investigated through cyclic voltammetry, and redox sensitivity to the presence of different anions is noted. Free‐end bending actuation performance and force generation within silk‐PPy composite films during oxidation and reduction in a biologically relevant environment are investigated in detail. These silk–PPy composites are stable to repeated actuation, and are able to generate forces comparable with natural muscle (>0.1 MPa), making them ideal candidates for interfacing with biological tissues.     

微杯电子纸及其后加工制程

SiPix利用独特的微杯(Microcup)结构和顶部灌注封装技术，通过连续整卷高速涂布的制程成功地制造出高性能的双稳性、装填电泳微粒的电子纸。SiPix可提供下列两种规格形式任意的EPD卷式成品：(A)用于有源矩阵EPD和直接驱动产品的可剥离保护膜／已灌装及密封的Microcup／无图案导体膜夹层卷；及（P）用于无源矩阵的行导体膜／已灌装及密封的Microcup／列导体膜夹层卷。已经开发出将EPD卷制成不同的显示模块或产品的简单的后续加工制程。