New cubane MOCVD precursors for gallium sulphide and gallium selenide: Synthesis of [(Et2MeC)GaS]4 and [(Me2EtC)GaS]4: Structural determinations of [(Et2MeC)GaS]4 by X-ray diffraction and [(tBu)GaSe]4 by electron diffraction

The gallium sulphide cubane compounds [(Me₂EtC)GaS]₄ and [(Et₂MeC)GaS]₄, have been synthesised, and their potential as MOCVD precursors for GaS is discussed. The molecular structure of [(Et₂MeC)GaS]₄ has been determined by X-ray diffraction. In addition, the vapour phase structure of the GaSe precursor, [(^tBu)GaSe]₄ has been determined by gas phase electron diffraction and is compared with that previously determined in the solid state by X-ray diffraction.     

Second-Order optical non-linearities of {4-(dimethylamino) stilben z & e 4'-yl} dimesityl borane

Samples of {4-(dimethylamino) stilben Z & E 4'-yl} dimesityl borane (BNS) were synthesised and investigated for their non-linear optical properties. The results show that the quadratic hyperpolarisability of the Z-isomer is smaller than that of the E-isomer, the beta value found for the latter being as high as 60 × 10^?30 esu.     

下扬子地区中上二叠统页岩有机孔发育特征

下扬子地区中上二叠统发育一套海陆过渡相页岩,其显微组成与海相页岩存在明显的差异,为了研究该套页岩有机孔的发育特征及影响因素,开展了有机岩石学、扫描电镜、氩离子抛光扫描电镜、气测孔隙度和压汞等相关分析。研究表明,中上二叠统页岩中有机孔整体发育较好,但不同有机质组分中孔隙的发育存在明显的差别,具体表现为镜质体内孔隙发育差,固体沥青内发育少量孤立的孔隙,腐泥质内具有丰富的孔隙。黄铁矿或黏土矿物常与有机质形成有机/矿物复合体,复合体内有机孔普遍发育较好,可能与黄铁矿或黏土矿物促进有机质生烃和分解有关。中上二叠统页岩TOC含量与比表面积之间存在明显的线性正相关性,但与孔隙度之间具有复杂的关系,当w（TOC）<6.16%时,孔隙度随TOC含量的增加而增加,而当w（TOC）>6.16%时,孔隙度普遍较低且与TOC含量之间存在微弱的负相关性。孔径分布特征也揭示高TOC页岩的中—大孔体积明显低于低TOC页岩。页岩孔隙结构发育特征表明,TOC含量越高、固体沥青组分以及贫氢组分的含量越高,这些组分占据的矿物孔隙越多,降低了页岩总的孔隙空间,且TOC含量越高,页岩越易被压实,造成中大孔塌陷,进一步降低了页岩的孔隙度。     

The Control of Shrinkage and Thermal Instability in SU‐8 Photoresists for Holographic Lithography

The negative‐tone epoxy photoresist, SU‐8, expands ≈1% by volume after postexposure baking. However, if the maximum optical fluence is comparable to that at the insolubility threshold, as in a holographic exposure, the developed resist shrinks (≈35% by volume) due to the removal of light oligomers not incorporated into the polymeric network. IR spectroscopy shows that, at this level of exposure, only 15% of the epoxy groups in the insoluble polymer have reacted; consequently microstructural elements soften and collapse at >100 °C. When the light oligomers are removed, the sensitivity of the resist is unchanged, provided that 5% (w/w) of a high‐molecular‐weight reactive plasticizer (glycidoxy‐terminated polyethylene glycol) is added, but it shrinks less on development and, when used as a photonic crystal template, shows improved uniformity with less cracking and buckling. Reinforcing the polymer network by reaction with the polyfunctional amine (bis‐N,N′‐(3‐aminopropyl)ethylenediamine) increases the extent of cross‐linking and the thermal stability, allowing inverse replicas of photonic crystal templates to be fabricated from both Al:ZnO and Zr₃N₄ using atomic layer deposition at temperatures up to 200 °C.     

FULL-RCMA: a high utilization EPON

This paper proposes an alternate solution for Ethernet passive optical networks. Our solution uses a novel protocol named full utilization local loop request contention multiple-access protocol to efficiently provide communications in passive optical networks. We study the physical layer implementation, as well as medium access control (MAC) layer protocol performance to illustrate the feasibility and benefit of our solution. The performance studies show that the MAC protocol is capable of offering 95% channel utilization under heavy load conditions. The performance results also indicate that delivery of multimedia traffic with a high quality-of-service can be achieved with our solution.     

Efficient parasitic substrate modeling for monolithic mixed-A/D circuit design and verification

Parasitic analog-digital noise coupling has been identified as a key issue facing designers of mixed-signal integrated circuits. In particular, signal crosstalk through the common chip substrate has become increasingly problematic. This paper demonstrates a methodology for developing simulation, synthesis, and verification models to analyze the global electrical behavior of the non-ideal semiconductor substrate. First, a triangular discretization method is employed to generate RC equivalent-circuit substrate models which are far less complex than those formulated by conventional techniques. The networks are then accurately approximated for subsequent analysis by an efficient reduction algorithm which uses a well-conditioned Lanczos moment-matching process. Through congruence transformations, the network admittance matrices are transformed to reduced equivalents which are easily post-processed to derive passive, SPICE-compatible netlist representations of the reduced models. The pure-RC properties of the extracted substrate networks are fully exploited to formulate an efficient overall algorithm. For validation, the strategy has been successfully applied to several mixed-signal circuit examples.     

Entropy-constrained tree-structured vector quantizer design

Current methods for the design of pruned or unbalanced tree-structured vector quantizers such as the generalized Breiman-Friedman-Olshen-Stone (GBFOS) algorithm proposed in 1980 are effective, but suffer from several shortcomings. We identify and clarify issues of suboptimality including greedy growing, the suboptimal encoding rule, and the need for time sharing between quantizers to achieve arbitrary rates. We then present the leaf-optimal tree design (LOTD) method which, with a modest increase in design complexity, alters and reoptimizes tree structures obtained from conventional procedures. There are two main advantages over existing methods. First, the optimal entropy-constrained nearest-neighbor rule is used for encoding at the leaves; second, explicit quantizer solutions are obtained at all rates without recourse to time sharing. We show that performance improvement is theoretically guaranteed. Simulation results for image coding demonstrate that close to 1 dB reduction of distortion for a given rate can be achieved by this technique relative to the GBFOS method.     

Concurrent Knowledge Extraction in Public-Key Models

Knowledge extraction is a fundamental notion, modeling machine possession of values (witnesses) in a computational complexity sense and enabling one to argue about the internal state of a party in a protocol without probing its internal secret state. However, when transactions are concurrent, say over the Internet, with players possessing public keys (as is common in cryptography), assuring that entities “know” what they claim to know, where adversaries may be well coordinated across different transactions, turns out to be much more subtle and in need of re-examination. In such settings, mixing the public-key structure as part of the language and statements is a natural adversarial strategy. Here, we investigate how to formally treat knowledge possession by parties interacting concurrently in the public-key model. More technically, we look into the relative power of the notion of “concurrent knowledge extraction” (CKE) for concurrent zero knowledge (CZK) in the bare public-key (BPK) model, where the language and statements being proved can be dynamically and adaptively chosen by the prover and may be possibly based on verifiers’ public keys. By concrete attacks against some existing natural protocols, we first show that concurrent soundness and normal arguments of knowledge do not guarantee concurrent verifier security in the public-key setting. Here, roughly speaking, concurrent verifier security says that the malicious concurrent prover should “know" all the witnesses to all the possibly public-key-related statements adaptively chosen and successfully proved in the concurrent sessions. These concrete attacks serve as a good motivation for understanding “possession of knowledge” for concurrent transactions with registered public keys, i.e., the subtleties of concurrent knowledge extraction in the public-key model. This motivates us to introduce and formalize the notion of CKE, along with clarifications of various subtleties. Two implementations are then presented for constant-round concurrently knowledge extractable concurrent zero-knowledge (CZK–CKE) argument for \(\mathcal {NP}\) in the BPK model: One protocol is generic and based on standard polynomial-time assumptions, whereas the other protocol is computationally efficient and employs complexity leveraging in a novel way. Both protocols can be practically instantiated for some specific number-theoretic languages without going through general \(\mathcal {NP}\)-reductions. Of independent interest are the discussions about the subtleties surrounding the fundamental structure of Feige–Shamir zero knowledge in the BPK model.     

Magnetically Driven Silver‐Coated Nanocoils for Efficient Bacterial Contact Killing

The increasing threat of multidrug‐resistant bacterial strains against conventional antibiotic therapies represents a significant worldwide health risk and intensifies the need for novel antibacterial treatments. In this work, an effective strategy to target and kill bacteria using silver‐coated magnetic nanocoils is reported. The coil palladium (Pd) nanostructures are obtained by electrodeposition and selective dealloying, and subsequently coated with nickel (Ni) and silver (Ag) for magnetic manipulation and antibacterial properties, respectively. The efficiency of the nanocoils is tested in the treatment of Gram‐negative Escherichia coli (E. coli) and Gram‐positive methicillin‐resistant Staphylococcus aureus (S. aureus), both of which represent the leading multidrug‐resistant bacterial pathogens. The nanocoils show highly effective bacterial killing activity at low concentrations and in relatively short durations of treatment time. Three different investigation techniques, LIVE/DEAD assay, colony‐forming unit counting, and scanning electron microscope, reveal that the antibacterial activity is a result of bacterial membrane damage caused by direct contact with the nanocoil. The low cytotoxicity toward fibroblast cells along with the capability of precise magnetic locomotion makes the proposed nanocoil an ideal candidate to combat multidrug‐resistant bacteria in the field of biomedical and environmental applications.     

Efficient Internet traffic delivery over wireless networks

The high demand for wireless Internet connectivity has driven the development of highly efficient radio link technologies. However, their performance can be compromised by inadvertent interactions with the higher-layer TCP flow control protocol. Maximizing the performance of wireless links requires that mechanisms operating at every layer of the protocol stack interact efficiently. This article provides a brief tutorial of some of these radio link enhancements. It then outlines how higher-layer flow control protocols should behave, and provides techniques for taming the behavior of TCP, to ensure that the performance of lower-layer enhancements is not compromised.