Prebiotic synthesis of sequential peptides on the Hadean beach by a molecular engine working with nitrogen oxides as energy sources

Addressing the still open question of the prebiotic origin of sequential macromolecules (peptides, nucleic acids) on the primitive Earth, we describe a molecular engine (the primary pump), which works at ambient temperature and continuously generates, elongates and complexifies sequential peptides. This new scenario is based on a cyclic reaction sequence, whose keystep is the activation of amino acids into their N‐carboxyanhydrides (NCA) through nitrosation by NOx. This process could have taken place on tidal beaches; it requires a buffered ocean, emerged land and a nitrosating atmosphere. With the help of geochemical studies and computer simulations of atmosphere photochemistry, we show that the primitive Earth during the Hadean may have satisfied all these requirements. © 2001 Society of Chemical Industry.     

认知无线电多址接入系统的研究

针对认知无线电(Cognitive Radio)频谱不连续,随机性和变化性大,以及TDMA,FDMA,CDMA不适用的问题,提出了一个基于变换域通信(Transform Domain Communication System)平台的认知无线电多址接入系统.该系统发射机通过将非空闲的频谱幅度置0,实现对授权用户的躲避;采用m状态序列产生的伪随机相位矢量,生成近似正交的调制基函数实现用户的多址接入;接收端通过本地基函数与接收信号相关估计出原始数据,并理论分析了系统的误码率.仿真表明,系统的检测概率,多址接入的用户数以及收发两端基函数的不一致会影响系统的性能.该系统能利用非连续频谱,并且基函数能够自适应变化,适合认知无线电。     

Two new aluminophosphates, IST-1 and IST-2: First examples of a dual templating role of water and methylamine in generating microporous structures

This study is aimed at exploring the ability of very small sized N-bearing molecules to generate and stabilize microporous aluminophosphates. Two new AlPO₄-n materials, called IST-1 and IST-2, have been obtained in aqueous media using, as main template, methylamine (MA), directly added, or generated in situ from methylformamide (MF) degradation. While IST-1 topology proved to be novel, IST-2 appears structurally related to AlPO₄-53(A). The obtained materials were characterized by powder XRD, TG/DSC, SEM and solid-state NMR. Tetraalkylammonium (TEA) cations were used as potential co-templates but only MA and water were found incorporated in the pore volumes of both structures, which argues for their true templating role. In IST-1, ¹³C solid-state NMR studies showed that half of MA species, presumably protonated, is H-bonded to framework oxygens while the other half surprisingly bonds directly to framework Al atoms. ¹³C NMR showed that only protonated MA occurs in IST-2 channels. TEA⁺ cations definitely do not play any specific template role. They indirectly favor the crystallization of IST-1 or IST-2 devoid from other crystalline or amorphous side phases, by interacting with part of the Al and P in solution and forming soluble [AlPO₄(OH)]–[TEA,HMA] complexes, substantially modifying the compositions of gels precursors to each phase during nucleation and/or growth steps. While both IST-1 and IST-2 crystallize from gels of similar initial compositions, it was demonstrated that the new MA/T ratio (T = Al or P) obtained after in situ complexation was the key parameter that specifically governs the crystallization of each phase.     

Dual concentric core dispersion compensating fibre optimised for WDM application

A dual concentric core fibre exhibiting a chromatic dispersion coefficient around -350 ps/(nm km) is used in a dispersion compensating module designed for WDM application. The optimised length ratio is larger than 20 and the residual chromatic dispersion is measured at 0.4 ps/(nm km) in the C-band     

Development of an odor wheel classification scheme for wastewater.

Overall, in the air pollution control field, odor concentration and intensity as well as hedonic rating have been well studied to the point where some level of standardization is being developed or is already in place. However, there has been no standardization with respect to odor quality characterization. There is now sufficient understanding of the types of odorous compounds that can arise from wastewater treatment processes to develop an odor classification scheme. This article presents the first wastewater odor wheel or classification scheme that should form the foundation for the evolution of odor quality data reporting with links to chemical causes.     

Sensory evaluation of the odors produced during bromophenol formation using a multi-level statistical model.

In response to reports of medicinal taste and odor problems in suburban Paris, a lab scale study was conducted to investigate the contribution of different water quality parameters--pH, phenol, bromide, chlorine, temperature and dissolved oxygen levels--on bromophenol medicinal odor formation using the Flavor Profile Analysis (FPA) method. A study of six parameters at 2 levels (64 experiments) analyzed by the FPA method suggests that chlorine at high concentration is more important as a controlling agent than phenol under similar conditions and the ratio of HOBr:Phenol and the time for reaction will control subsequent brominated products of reaction. Results from a three-level statistical model indicate that high pH was associated with lower odor intensities, whereas high levels of chlorine, phenol and temperature were associated with high odor intensities. Potential worst case scenarios of water quality conditions were determined for evaluation by chemical identification and kinetics.     

A new methodology for the identification of ball bond degradation during high-temperature aging tests on devices in standard plastic packages

We describe a new methodology for the “in situ” identification of wire-bond degradation at early stages during high-temperature aging tests on devices with standard plastic packages. This methodology is based on the measurement of the changes in wire bond resistance, which is deduced from the I(V) characteristics of the ESD protection diodes on each contact pad of the circuit. In a first stage, the measurement procedure is described, with emphasis on the initial temperature calibration. This procedure allows for an “in situ” measurement sequence, where the packages stay in the aging chamber, at elevated temperature, during the electrical tests on the pad connections performed at different aging durations. By following accurately the package temperature, using a thermocouple, it is possible to correct for slight changes and thus get a reliable I–V measurement for each interconnection. In the second stage, the aging test results are described, showing the evolution of each individual interconnection. We were able to identify the onset of wire-bond degradation through the progressive increase of their resistance. To allow for better determination of the degradation process, once an increase in wire bond resistance was detected, complete I(V) curves were recorded at the pin(s) of interest. For each pin of a TQFP64 package, the tests were performed at least twice a day, with increased density when initial failure is detected (one complete measurement every 3 h). This strategy allowed for the detection of different behaviors on the wire bonds: good ball bonds (i.e. ball bonds with no change in their resistance), ball bond with intermittent opens (these ball bonds are in the process of degradation, and thermo-mechanical stresses induced in the resin by very small temperature changes are sufficient to open or close the circuits) and completely destroyed ball bonds, for which the resistance stays in an “high” level. This approach to wire-bond degradation in plastic packages is very powerful in terms of the number of interconnections which can be followed “in real time” and especially has the advantage, over other classical approaches, that the devices under test stay operational, contrary to what occurs with other types of destructive testing. These electrical test results are compared with metallographic investigations performed after a series of mechanical tests on the ball bonds (wire pull/ball shear tests) on a set of identical devices which undergone exactly the same High Temperature Storage (HTS) aging for 2000 h at 165 °C.     

Addressing Nanomaterial Immunosafety by Evaluating Innate Immunity across Living Species

The interaction of a living organism with external foreign agents is a central issue for its survival and adaptation to the environment. Nanosafety should be considered within this perspective, and it should be examined that how different organisms interact with engineered nanomaterials (NM) by either mounting a defensive response or by physiologically adapting to them. Herein, the interaction of NM with one of the major biological systems deputed to recognition of and response to foreign challenges, i.e., the immune system, is specifically addressed. The main focus is innate immunity, the only type of immunity in plants, invertebrates, and lower vertebrates, and that coexists with adaptive immunity in higher vertebrates. Because of their presence in the majority of eukaryotic living organisms, innate immune responses can be viewed in a comparative context. In the majority of cases, the interaction of NM with living organisms results in innate immune reactions that eliminate the possible danger with mechanisms that do not lead to damage. While in some cases such interaction may lead to pathological consequences, in some other cases beneficial effects can be identified.     

Application of pyrolysis-gas chromatography-mass spectrometry to the characterization of humic substances resulting from decay of aquatic plants in sediments and waters

Pyrolysis-GC-MS, elemental analysis and i.r. spectroscopy reveal major differences between humic substances from aquatic plants (algae and aquatic phanerogams) and lagoonal, marine and lacustrine deposits. Algae are enriched in proteins and their pyrolysis yields numerous nitrogenous by-products (alkylpyrroles, nitriles and alkylpyridines) along with aromatic compounds which are thought to reflect the decomposition of individual amino-acids (styrene, toluene, phenol and p-cresol). These compounds are less abundant in the pyrolysis products of humic substances from phanerogams with increasing amounts of methoxyphenols, characteristics of lignins.In the deposits of the Kerguelen Islands and of a “blue lake” in Greenland, the importance of algal populations is emphasized by pyrolysis products corresponding to nitrogenous and carbohydrate derivatives. Phenols and cresols in the pyrochromatograms of these samples are interpreted as evidence of polypeptides rather that lignin: p-cresol is much more abundant than the other cresols, suggesting the formation of phenols by way of tyrosine.Lagoonal sediments, in contrast, seem typical of intermixed development of algae and phanerogams.Differences between fulvic and humic acids are emphasized by the development of polyphenols and protein derivatives in humic acids compared to polysaccharide derivatives in fulvic acids. Other constituents revealed by PY-GC-MS include N-acetyl aminosugars, phthalates and aliphatic compounds.     

Biologically Inspired and Magnetically Recoverable Copper Porphyrinic Catalysts: A Greener Approach for Oxidation of Hydrocarbons with Molecular Oxygen

An efficient synthetic method for magnetically recoverable hybrid copper porphyrinic nanomaterials is reported. These functionalized magnetic materials prove to be efficient bioinspired oxidation catalysts of olefins and thiols, using molecular oxygen as oxidant, in total absence of reductants and solvents, with the highest TON (turnover number) yet achieved for this reaction (≈200 000). A comparative study between homogeneous and heterogeneous oxidation of cyclohexene is discussed, revealing the heterogeneous system to be the most promising concerning stability and reusability of the catalysts. The full characterization of the magnetic hybrid porphyrinic nanomaterials, by transmission electron microscopy, flame atomic absorption spectrometry, thermogravimetry, N₂ sorption, and infrared spectroscopy, is also described.