A protocol for causally ordered message delivery in mobile computing systems

There is a growing trend in developing applications for mobile computing systems in which mobile host computers retain their network connections while in transit. This paper proposes an algorithm that enforces a useful property, namely, causal ordering, that delivers messages among mobile hosts. This property ensures that causally related messages directed to the same destination will be delivered in an order consistent with their causality, which is important in applications that involve human interaction such as mobile email and mobile teleconferencing. Such applications are envisioned by the proponents of Personal Communications Services (PCS). Without this property, users may receive and read original messages and the corresponding replies out of order. Our algorithm, when compared with previous proposals, provides an alternative with a low handoff cost, medium message overhead, and low probability of unnecessary inhibition in delivering messages.     

Performance evaluation of a bigrating as a beam splitter

The design of a bigrating for use as a beam splitter is presented. It is based on a rigorous formulation of plane-wave scattering by a bigrating that is composed of two individual gratings oriented in different directions. Numerical results are carried out to optimize the design of a bigrating to perform 1 x 4 beam splitting in two dimensions and to examine its fabrication and operation tolerances. It is found that a bigrating can be designed to perform two functions: beam splitting and polarization purification.     

Chiroptical‐Conjugated Polymer/Chiral Small Molecule Hybrid Thin Films for Circularly Polarized Light‐Detecting Heterojunction Devices

Herein, a simple and facile strategy is described to obtain chiroptically active semiconductor thin films by blending of poly(3‐alkylthiophene)s, which are conventional achiral polymer semiconductors, and 1,1′‐binaphthyl (BN), a versatile chiral molecule. As expected, the intermolecular interaction between the two materials is important to extend the chirality of the binaphthyl molecules to the hybrid films. The controlled phase separation and crystallization of poly[3‐(6‐carboxyhexyl)thiophene‐2,5‐diyl] (P3CT) and binaphthyl hybrid films result in unique heterojunction bilayer thin‐film structures that consisted of BN microcrystals at the top and a P3CT/BN mixed layer at the bottom. Such heterojunction bilayer films exhibit significantly amplified chiroptical response with weak broadened tails, which is due to the enhanced crystallization of the chiral BN molecules and formation of heteroaggregates in the hybrid films. Based on the characterization of crystalline structure and photoluminescence analysis, it is found that new electronic energy states are formed in the conduction band region of P3CTs in the P3CT/BN heteroaggregates, which contribute to chirality transfer from BN to the hybrid films. As a proof of concept, a photodiode capable of distinguishably sensing the left‐ and right‐handed circularly polarized light is successfully fabricated by using the hybrid films with the heterojunction bilayer structure.     

UV‐Curable Silver Electrode for Screen‐Printed Thermoelectric Generator

Fabricating thermoelectric generators (TEGs) using the screen‐printing process has advantages, including mass production, device scalability, and system applicability. However, the thick film formed through the process typically has low film density, and reduced performance, because of the presence of pores in the film created by the vaporization of the resin during high‐temperature annealing. During the soldering process used for thermoelectric module fabrication, the printed solder infiltrates into the screen‐printed electrodes through the micropores in the electrodes, causing cracks of the electrode film and an increase in resistivity. In this paper, an ultraviolet radiation (UV)‐curable process for screen‐printed electrodes is reported. The paste for the electrodes is synthesized by mixing Ag flakes that can be cured at low temperature with a UV resin. Scanning electron microscope images show that the UV‐curing process significantly reduces pores and thereby results in a smooth‐surfaced electrode layer. The film density after crystallization is also enhanced. TEGs composed of 72 couples with UV‐curable Ag electrodes generate a high power density of ≈6.69 mW cm^?2 at a temperature difference of 25 °C; the device resistance is ≈0.75 Ω, and the figure of merit of the device is recorded to be 0.57, which is the highest among the printed TEGs.     

Local Immune‐Triggered Surface‐Modified Stem Cells for Solid Tumor Immunotherapy

Here, described are additional treatment strategies that make use of human mesenchymal stem cell (hMSC)‐based local immunotherapeutic agents for the treatment of solid tumors. Dibenzocyclooctyne‐poly(ethylene glycol)‐pheophorbide A conjugates are engineered for cell surface conjugation by copper‐free click chemistry and are subsequently conjugated to hMSC (hMSC‐DPP). hMSC‐DPP can recognize and migrate toward cancer lesions, where they secrete pro‐inflammatory cytokines such as interleukin (IL)‐6, IL‐8, and heat shock protein 70 in pursuance of photodynamic therapy‐mediated cell death. The secreted immune factors trigger interferon gamma, IL‐2, IL‐4, IL‐12, and granulocyte‐macrophage colony‐stimulating factor, resulting in the local accumulation of T cells, B cells, natural killer cells, and antigen presenting cells at the tumor site. Treatment with hMSC‐DPP induces the accumulation of cytokines at the cancer site and minimizes systemic immune‐based side effects. This strategy is expected to increase the vulnerability of cancer cells to immune cells and cytokines, thus aiding in the development of a robust treatment platform for cancer immunotherapy.     

Microparticle‐Based Soft Electronic Devices: Toward One‐Particle/One‐Pixel

While microparticle (MP) assemblies have long attracted academic interest, few practical applications of assembled MPs have been achieved because of technological difficulties related to MP synthesis, MP position registration, and the absence of device concepts. The precise positioning of functional MPs in a proper stencil can produce flexible/stretchable electronic devices, even when the MPs themselves are rigid. In recent years, remarkable progress has been made in the programmable position registration of MPs, production of functional MPs, and concepts for MP‐based, pixel‐type electronic devices. This progress report reviews the recent technological advances in MP assembly and discusses the technological challenges preventing the realization of the one‐particle/one‐pixel concept.     

Structural Changes of 2D FexMn1−xO2 Nanosheets for Low‐Temperature Growth of Carbon Nanotubes

The synthesis of carbon nanotubes (CNTs) is usually done by metallic catalysts with a gaseous carbon precursor at high temperature. Yet, mild synthesis conditions can broaden the application of CNTs and their composites. In the present work, it is unraveled why partially substituted Fe ions in 2D MnO₂ nanosheets lead to the growth of CNTs at low temperatures of 400?500 °C. The local formation of Fe₃C by carbon precursor explains the unusually high catalytic activity of 2D Fe_xMn_1?xO₂ nanosheets for preparing CNTs. Finally, Fe₃C is oxidized to Fe₃C/FeO_x yolk/shell morphology in ambient atmosphere after the CNT formation reaction. These results shed light on the development of novel catalyst materials that allow for efficiently prepare CNTs under mild conditions for their wider use in energy‐harvesting applications.     

The new route for realization of 1‐μm‐pixel‐pitch high‐resolution displays

A new pixel structure for the realization of a 1‐μm‐pixel‐pitch display was developed. This structure, named vertically stacked thin‐film transistor (VST), was based on the conventional back‐channel etched thin‐film transistor (TFT), but all the layers except the horizontal gate line were vertically stacked on the embedded data line, enabling the implementation of high‐resolution display panels. The VST device with a channel length of 1 μm showed a high field effect mobility of more than 50 cm²/Vs and low subthreshold slope of 78 mV per decade. It also shows a high uniform electrical characteristic over the entire 6‐in. wafer. The development of a new pixel architecture is expected to enable the implementation of 1‐μm‐pixel‐pitch high‐resolution displays such as spatial light modulators for digital holograms.     

Facilitated Water Transport through Graphene Oxide Membranes Functionalized with Aquaporin‐Mimicking Peptides

Water purification by membranes is widely investigated to address concerns related to the scarcity of clean water. Achieving high flux and rejection simultaneously is a difficult challenge using such membranes because these properties are mutually exclusive in common artificial membranes. Nature has developed a method for this task involving water‐channel membrane proteins known as aquaporins. Here, the design and fabrication of graphene oxide (GO)‐based membranes with a surface‐tethered peptide motif designed to mimic the water‐selective filter of natural aquaporins is reported. The short RF8 (RFRFRFRF, where R and F represent arginine and phenylalanine, respectively) octapeptide is a concentrated form of the core component of the Ar/R (aromatic/arginine) water‐selective filter in aquaporin. The resulting GO‐RF8 shows superior flux and high rejection similar to natural aquaporins. Molecular dynamics simulation reveal the unique configuration of RF8 peptides and the transport of water in GO‐RF8 membranes, supporting that RF8 effectively emulates the core function of aquaporins.     

Broadband High‐Efficiency Chiral Splitters and Holograms from Dielectric Nanoarc Metasurfaces

Simultaneous broadband and high efficiency merits of designer metasurfaces are currently attracting widespread attention in the field of nanophotonics. However, contemporary metasurfaces rarely achieve both advantages simultaneously. For the category of transmissive metadevices, plasmonic or conventional dielectric metasurfaces are viable for either broadband operation with relatively low efficiency or high efficiency at only a selection of wavelengths. To overcome this limitation, dielectric nanoarcs are proposed as a means to accomplish two advantages. Continuous nanoarcs support different electromagnetic resonant modes at localized areas for generating phase retardation. Meanwhile, the geometric nature of nanoarc curvature endows the nanoarcs with full phase coverage of 0–2π due to the Pancharatnam–Berry phase principle. Experimentally incorporated with the chiral‐detour phase principle, a few compelling functionalities are demonstrated, such as chiral beamsplitting, broadband holography, and helicity‐selective holography. The continuous nanoarc metasurfaces prevail over plasmonic or dielectric discretized building block strategies and the findings lead to novel designs of spin‐controllable metadevices.