Crystallization and preliminary X-ray analysis of a D-alanyl-D-alanine ligase (EcDdlB) from Escherichia coli

A recombinant form of Escherichia coli DdlB (EcDdlB) has been prepared and cocrystallized with ADP and D-alanyl-D-alanine to represent the ternary complex of EcDdlB. Furthermore, EcDdlB has been cocrystallized under the same conditions with the ligands ATP and D-alanyl-D-alanine, representing the product-inhibited complex. The crystals belonged to space group P212121, with unit-cell parameters a = 53.0, b = 97.6, c = 109.5 Å and a = 51.2, b = 97.8, c = 110.1 Å, respectively, and both contained two molecules in the asymmetric unit. Complete data sets were collected to 1.5 and 1.4 Å resolution, respectively, from single crystals under cryogenic conditions using synchrotron radiation

Photonic band gaps analysis of Thue-Morse multilayers made of porous silicon

Dielectric aperiodic Thue-Morse structures up to 128 layers have been fabricated by using porous silicon technology. The photonic band gap properties of Thue-Morse multilayers have been theoretically investigated by means of the transfer matrix method and the integrated density of states. The theoretical approach has been compared and discussed with the reflectivity measurements at variable angles for both the transverse electric and transverse magnetic polarizations of light. The photonic band gap regions, wide 70 nm and 90 nm, included between 0 and 30°, have been observed for the sixth and seventh orders, respectively

Automated knowledge capture in 2D and 3D design environments

In Life Cycle Engineering, it is vital that the engineering knowledge for the product is captured throughout its life cycle in a formal and structured manner. This will allow the information to be referred to in the future by engineers who did not work on the original design but are wanting to understand the reasons that certain design decisions were made. In the past, attempts were made to try to capture this knowledge by having the engineer record the knowledge manually during a design session. However, this is not only time-consuming but is also disruptive to the creative process. Therefore, the research presented in this paper is concerned with capturing design knowledge automatically using a traditional 2D design environment and also an immersive 3D design environment. The design knowledge is captured by continuously and non-intrusively logging the user during a design session and then storing this output in a structured eXtensible Markup Language (XML) format. Next, the XML data is analysed and the design processes that are involved can be visualised by the automatic generation of IDEF0 diagrams. Using this captured knowledge, it forms the basis of an interactive online assistance system to aid future users who are carrying out a similar design task

Nonaqueous Fluoride/Chloride Anion-Promoted Delamination of Layered Zeolite Precursors: Synthesis and Characterization of UCB-2

The delamination of layered zeolite precursor PREFER is demonstrated under mild nonaqueous conditions using a mixture of cetyltrimethylammonium bromide, tetrabutylammonium fluoride, and tetrabutylammonium chloride in N,N-dimethylformamide (DMF) as solvent. The delamination proceeds through a swollen material intermediate which is characterized using powder X-ray diffraction (PXRD). Subsequent addition of concentrated HCl at room temperature leads to synthesis of UCB-2 via delamination of the swollen PREFER material and is characterized using PXRD, transmission electron microscopy (TEM), and argon gas physisorption, which shows lack of microporosity in UCB-2. ^(29)Si magic angle spinning (MAS) NMR spectroscopy indicates lack of amorphization during delamination, as indicated by the entire absence of Q^2 resonances, and ^(27)Al MAS NMR spectroscopy shows exclusively tetrahedral aluminum in the framework following delamination. The delamination process requires both chloride and fluoride anions and is sensitive to solvent, working well in DMF. Experiments aimed at synthesizing UCB-2 using aqueous conditions previously used for UCB-1 synthesis leads to partial swelling and lack of delamination upon acidification. A similar lack of delamination is observed upon attempting synthesis of UCB-1 under conditions used for UCB-2 synthesis. The delamination of PREFER is reversible between delaminated and swollen states in the following manner. Treatment of as-made UCB-2 with the same reagents as used here for the swelling of PREFER causes the delaminated UCB-2 material to revert back to swollen PREFER. This causes the delaminated UCB-2 material to revert back to swollen PREFER. Altogether, these results highlight delamination as the reverse of zeolite synthesis and demonstrate the crucial role of noncovalent self-assembly involving the zeolitic framework and cations/anions/structure-directing agent and solvent during the delamination process

Delamination of Layered Zeolite Precursors under Mild Conditions: Synthesis of UCB-1 via Fluoride/Chloride Anion-Promoted Exfoliation

New material UCB-1 is synthesized via the delamination of zeolite precursor MCM-22 (P) at pH 9 using an aqueous solution of cetyltrimethylammonium bromide, tetrabutylammonium fluoride, and tetrabutylammonium chloride at 353 K. Characterization by powder X-ray diffraction, transmission electron microscopy, and nitrogen physisorption at 77 K indicates the same degree of delamination in UCB-1 as previously reported for delaminated zeolite precursors, which require a pH of greater than 13.5 and sonication in order to achieve exfoliation. UCB-1 consists of a high degree of structural integrity via ^(29)Si MAS NMR and Fourier transform infrared spectroscopies, and no detectable formation of amorphous silica phase via transmission electron microscopy. Porosimetry measurements demonstrate a lack of hysteresis in the N_2 adsorption/desorption isotherms and macroporosity in UCB-1. The new method is generalizable to a variety of Si:Al ratios and leads to delaminated zeolite precursor materials lacking amorphization

Cu isotopes in groundwater for hydrogeochemical mineral exploration: A case study using the world-class Mount Isa Cu–Pb–Zn deposit (Australia)

Copper is the crux resource in the transition to renewable energy sources, with green technologies such as solar panels, wind turbines and batteries all relying on this critical metal for their componentry, and more importantly for connection to electrical grids. While demand intensifies, copper discovery rates continue to fall due to increased scarcity of deposits that are outcropping and/or detectable by conventional means. This has engendered novel methods of detecting Cu-bearing ore under cover, such as hydrogeochemical analyses to trace ore mineral interaction with natural waters. This notably includes the development of Cu isotope systematics in natural waters, wherein proximal to Cu-bearing ore bodies enrichment of water in the heavier Cu isotope occurs (e.g. from oxidative weathering), thus providing a fingerprint of water interaction with Cu-bearing sulfides. Here, Cu isotope compositions for eighteen groundwater samples overlying and distal to the world-class, sediment-hosted stratiform Mount Isa Cu–Zn–Pb deposit were analyzed to assess the utility of groundwater Cu isotope compositions as an exploration tool for Cu-bearing ore under cover. A further 12 chalcopyrite Cu isotope compositions were determined from two drill cores directly overlying the main Cu-bearing ore body, to establish a baseline Cu isotope composition for the Mt Isa deposit. Cu isotope data were synthesized together with field water parameters and placed within a geological context to construct a framework for interpretation. When accounting for industrially impacted sites and underlying geology, results show a clear trend towards heavy Cu isotope enrichment in groundwater proximal to known mineralization, with enrichments of ∼1 per mil (‰) or more relative to distal groundwater and primary deposit chalcopyrite. These results corroborate and expand upon similar work from surface and groundwater samples around porphyry, exotic and IOCG Cu-bearing deposits. Moreover, these results strongly indicate that groundwater Cu isotope systematics for exploration under cover has great potential as a vectoring tool, illustrating that thus far the technique is applicable across deposit types

Playing with light in diatoms: microalgae with a natural photonic crystal structure

Complex micro- and nano-structured materials for photonic applications are designed and fabricated using top technologies. A completely different approach to engineering systems at the sub-micron-scale consists in recognizing the nanostructures and morphologies that nature has optimized during life’s history on earth. In fact, biological organisms could exhibit ordered geometries and complex photonic structures which often overcome the products of the best available fabrication technologies [1]. An example is given by diatoms, microalgae with a peculiar cell wall consisting of amorphous hydrated silica valves reciprocally interconnected in a structure called the frustule. Valve surfaces exhibit specie-specific patterns of regular arrays of chambers, called areolae, developed into the frustule depth. Areolae range in diameter from few hundreds of nanometers up to few microns, and can be circular, polygonal or elongate [2]. The formation of these patterns can be modeled by self-organised, genetically controlled processes. Despite of the high level of knowledge on the genesis and morphology of diatom frustules, their functions are not completely understood [2]. In this work, we show that the silica valves of marine diatoms, characterized by a photonic crystal-like structure, have surprising optical properties, being capable of filtering and focalizing light, as well as exhibiting optical sensing capabilities

Fear and Loathing in H.S. Thompson's America : searching for Hope Amidst Decadence

In this paper, I will argue that Thompson's Fear and Loathing in Las Vegas exposes the decadence that accompanied the increasing power of a rich minority by commenting on the consequences Thompson sees projected onto his society, namely, his denunciation of the moral decadence that dominates American society. I will also comment on the forces that fought against the dominant decadence during the 1960s, and the counterculture movement that emerged from the subsequent freedom of this fight. Finally, I will mention the reaction of the powerful, who joined efforts to reduce the "excess" of democracy that the Civil Rights Movement brought about, thus, giving place to the death of the American Dream.En aquest treball, argumentaré que la novel·la de Thompson Fear and Loathing in Las Vegas exposa la decadència que va acompanyar el poder adquirit per una minoría rica comentant les consequències que Thompson veu projectades en la seva societat, és a dir, la seva denúncia de la decadència moral que domina la societat Americana. També, comentaré sobre les forces que van lluitar contra aquesta decadència en el període dels anys 1960, i la contracultura que va emergir de la llibertat consequent d'aquesta llüita. Finalment, mencionaré la reacció dels poderosos, qui van unir-se per redüir "l'excès" de democracia que va es van aconseguir en el Moviment de Drets Civils, donant pas així, a la mort del Somni Americà

Natural history and clinical outcome of differentiated thyroid carcinoma: a retrospective analysis of 1503 patients treated at a single institution

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Site 1220

Site 1220 (10°10.600´N, 142°45.503´W; 5218 meters below sea level (mbsl); Fig. F1) forms a southerly component of the 56-Ma transect drilled during Leg 199. It is situated about midway between the Clipperton and Clarion Fracture Zones in typical abyssal hill topography. On the basis of regional magnetic anomalies, we anticipated basement age at Site 1220 to be equivalent to Chron C25n (~56 Ma; Cande et al., 1989), slightly older than at Site 1219. At the outset of drilling at Site 1220, our estimate for total sediment depth was ~225 meters below seafloor (mbsf) (Fig. F2). Based upon a fixed hotspot model (Gripp and Gordon, 1990, for 0- to 5-Ma Pacific hotspot rotation pole; Engebretson et al., 1985, for older poles), Site 1220 should have been located ~3° south of the equator at 56 Ma and in an equatorial position at 40 Ma. Thus, Site 1220 should have been situated underneath the South Equatorial Current in the early Eocene. A nearby piston core (EW9709-13PC) taken during the site survey cruise recovered >16 m of red clay, with the base of the core dated as middle-early Miocene on the basis of radiolarian biostratigraphy (Lyle, 2000). Site 1220 will be used to study equatorial ocean circulation from the late Paleocene through the late Eocene during the early Cenozoic thermal maximum. Sediment records from this site will help to define the calcite compensation depth (CCD) and lysocline during the Paleocene-Eocene and Eocene-Oligocene transitions. In this and other respects, Site 1220 will act as an interesting analog to Site 1218. Both sites are thought to have been located on the equator at ~40 Ma, but the older crustal age anticipated at Site 1220 dictates a greater paleowater depth than for contemporaneous sediments accumulating at Site 1218