Since its invention, holography has emerged as a powerful tool to fully reconstruct the wavefronts of light including all the fundamental properties (amplitude, phase, polarization, wave vector, and frequency). For exploring the full capability for information storage/display and enhancing the encryption security of metasurface holograms, smart multiplexing techniques together with suitable metasurface designs are highly demanded. Here, we integrate multiple polarization manipulation channels for various spatial phase profiles into a single birefringent vectorial hologram by completely avoiding unwanted cross-talk. Multiple independent target phase profiles with quantified phase relations that can process significantly different information in different polarization states are realized within a single metasurface. For our metasurface holograms, we demonstrate high fidelity, large efficiency, broadband operation, and a total of twelve polarization channels. Such multichannel polarization multiplexing can be used for dynamic vectorial holographic display and can provide triple protection for optical security. The concept is appealing for applications of arbitrary spin to angular momentum conversion and various phase modulation/beam shaping elements.

The long hydrocarbon fatty acyl chain is energy rich, making it an ideal precursor for liquid transportation fuels and high-value oleo chemicals. As Saccharomyces cerevisiae has many advantages for industrial production compared to Escherichia coli. Here, we attempted to engineer Saccharomyces cerevisiae for overproduction of fatty acids. First, disruption of the beta-oxidation pathway, elimination of the acyl-CoA synthetases, overexpression of different thioesterases and acetyl-CoA carboxylase ACC1, and engineering the supply of precursor acetyl-CoA. The engineered strain XL122 produced more than 120 mg/L of fatty acids. In parallel, we inactivated ADH1, the dominant gene for ethanol production, to redirect the metabolic flux to fatty acids synthesis. The engineered strain DG005 produced about 140 mg/L fatty acids. Additionally, Acetyl-CoA carboxylase was identified as a critical bottleneck of fatty acids synthesis in S. cerevisiae with a cell-free system. However, overexpression of ACC1 has little effect on fatty acids biosynthesis. As it has been reported that phosphorylation of ACC1 may influent its activity, so phosphorylation sites of ACC1 were further identified. Although the regulatory mechanisms remain unclear, our results provide rationale for future studies to target this critical step. All these efforts, particularly the discovery of the limiting step are critical for developing a "cell factory" for the overproduction of fatty acids by using type I fatty acids synthase in yeast or other fungi.

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Web applications are one of the most prevalent platforms for information and service delivery over the Internet today. As they are increasingly used for critical services, web applications have become a popular and valuable target for security attacks. Although a large body of techniques have been developed to fortify web applications and mitigate attacks launched against them, there has been little effort devoted to drawing connections among these techniques and building the big picture of web application security research.This article surveys the area of securing web applications from the server side, with the aim of systematizing the existing techniques into a big picture that promotes future research. We first present the unique aspects of the web application development that cause inherent challenges in building secure web applications. We then discuss three commonly seen security vulnerabilities within web applications: input validation vulnerabilities, session management vulnerabilities, and application logic vulnerabilities, along with attacks that exploit these vulnerabilities. We organize the existing techniques along two dimensions:(1) the security vulnerabilities and attacks that they address and (2) the design objective and the phases of a web application during which they can be carried out. These phases are secure construction of new web applications, security analysis/testing of legacy web applications, and runtime protection of legacy web applications. Finally, we summarize the lessons learned and discuss future research opportunities in this area. ACM Reference Format:Xiaowei Li and Yuan Xue. 2014. A survey on server-side approaches to securing web applications. ACM Comput.