Reticular chemistry at the atomic,molecular,and framework scales

"There's plenty of room at the bottom."Feynmans talk has been frequently quoted for the advent of nanoscience,which gives profound perspectives of arranging atoms in the way we want[1].With the same bottom-up manner,reticular chemistry is concerned with linking of molecular building blocks by strong bonds to make crystalline open frameworks[2].The most im portant category practicing this bottom-up strategy at framework scale is m etal-organic frameworks(MOFs)coined in 1995[3],which leads to synthetic crystals featuring ultrahigh surface areas,fine-tuned pore metrics,and multivariate functionalities[4-16].The same strategy has also been successfully extended to crystalline covalent organic frameworks(COFs)from entirely organic building blocks through strong covalent bonds[17-19],whose crystal structures are now possible to be determ ined by 3D electron diffraction[20]and even X-ray diffraction[21].Recently,molecular weaving adds exotic flavors to reticular chemistry enabling the interlacing,knitting,and crocheting with molecular threads to make resilient nanotextiles[22].We envision the future of this field lays on the anisotropic reticular chem istry[23],where the components can be precisely arranged and manipulated along a specific direction.The atomic arrangement of various metals in the structures can be eventually read.     

Luting Cement,the Stronghold or the Weak Link in Ceramic Restorations?

A luting agent for fixing indirect dental restorations has to be a sophisticated material as, apart from being biocompatible, it must allow complete seating, provide mechanical support, has to secure the retention and to seal the gap between restoration and tooth structure for many years of function in an aggressive bio‐chemical and mechanical environment. Because of their adhesive potential, the latest generations of dental cements, the glass‐ionomer and resin‐based composites offer improved results. However, a major disadvantage of both classes of materials is their setting, being accompanied by shrinkage, which eventually leads to fracturing of the brittle ceramic. Apparently conflicting interests like being at the same time flexible as well as rigid, hold for luting cements for full ceramic restorations. The interaction between layer thickness, curing shrinkage stress, visco‐elasticity, module and strength for a thin adhesive cement layer will be discussed in the perspective of durable functioning of ceramic restorations.     

A review of some elements in the history of grain boundaries,centered on Georges Friedel,the coincident ‘site’ lattice and the twin index

I trace the origin of the inverse density of coincident lattice sites to Georges Friedel in 1904 (Études sur les groupements cristallins). Georges Friedel (1865–1933), son of the Chemist and Mineralogist Charles Friedel, called this parameter the twin (macle) index and defined it as the ratio of the total number of nodes of the primitive lattice to the number of coincident nodes restored by the twin operation. Friedel’s 1904 ‘multiple lattice’ is our Coincident Site Lattice. Georges Friedel introduced the Σ symbol in 1920 (Contribution à l’étude géométrique des macles) as the ratio of the volume of a (not necessarily primitive) multiple cell to the volume of the primitive cell. G. Friedel provides his reader with several formulae which, in the cubic case, give Σ = h ² + k ² + l ² (h, k and l being the indices of the twin plane) and a twin index I equal to Σ if Σ is odd, equal to Σ/2 if Σ is even. All these definitions and formulae are included in the 1926 version of his celebrated textbook ‘Leçons de Cristallographie’. Georges Friedel was also concerned with the ‘material lattice’ (the crystal structure) behind the mathematical lattice, but besides his contributions to the study of liquid crystals, Georges Friedel was mainly interested in Mineralogy and not in Metallurgy. This may explain why Walter Rosenhain apparently never knew of Friedel’s work and why Kronberg and Wilson had to re-discover the importance of the density of coincidence sites, at the atomistic level, in 1949 in copper. Georges Friedel’s grandson, Jacques Friedel, made the first numerical estimate of interface energies using interatomic potentials that same year but only published these results in 1953. Knowledge of these past events may help us to better understand the present theories and, hopefully, to develop our future understanding more efficiently.     

Manuel González Salazar,the Peruvian Atget

The Lima-born photographer Manuel González Salazar documented the colonial architectural heritage of his native city, as well as other major Peruvian cities such as Cusco, Arequipa, Ayacucho, Cajamarca and Trujillo. Just as Eugène Atget had documented the old Paris that he saw gradually disappearing, González Salazar chose to photograph the architectural and artistic heritage of the colonial era, which dominated the urban environment of the Peru of his day, but which was threatened by modernisation and social change. Like Atget in the French context, González Salazar is an anomaly in the history of Peruvian twentieth-century photography, which is best known on the international stage for indigenismo and the depiction of pre-Hispanic customs. The rediscovery of González Salazar’s work invites scholars to pay greater attention to the cultural heritage of the colonial era, as well as to the archives that documented it in all its splendour.     

CAS Delegation Visited the Aprica Childcare Institute,Japan

Adelegation from the China Association of Standardization(CAS), headed by Mr. Ma Lin-cong, secretary-general, visited Aprica Childcare In-stitute, Japan from June 19 to June 26, 2004, to carry out technical investigation for the drafting of a new standard for in-car child restraints. With continual economic development, China sees more and more families buying cars every year, and children are traveling by car much more often. Therefore, safety issues have attracted attention. However…     

Definition and measurement of the shear-lag parameter, β, as an index of the stress transfer efficiency in polymer composites

The shear-lag parameter, , employed in various problems of shear-lag analysis of composites is an unknown parameter which, in certain cases, is impossible to define. In this paper, a new methodology is proposed for the definition and subsequent experimental measurement of for various single-fibre model composites. It is argued that, if is defined as a fitting parameter for the solution of the shear-lag differential equation, then it can effectively serve as a stress-transfer efficiency index. The dependence of upon the conditions prevailing at the fibre–matrix interface will be demonstrated by measuring as a function of the fibre sizing in a carbon–epoxy composite system. © 1998 Chapman & Hall     

In situ statistical study of the nucleation,the variant selection and the orientation memory effect during the α⇌β titanium martensitic transformation

The h c p bcc and reverse phase transformation of titanium has been watched in situ and in real time by synchrotron X-ray topography from large single crystals. Due to the large crystal volume investigated, the results can be considered as statistical. The heterogeneous nucleation character of this transformation has been shown and the orientation relationships between the two phases have been elucidated. This transformation is characterized by a severe selection of the variants. Very frequently, the transformation product, in the direct and reverse transformation, resolves into a texture composed of several little crystals with a same and sole orientation. An orientation memory effect of the titanium single crystals has been displayed. Also the sample geometric shape, the unit cell volumes, the shape deformation and the unusual temperature dependence of the vibrational entropy have been taken into account in discussing the results.     

Safety,health or the environment--which comes first?

This paper describes the development and application of two integrated models which can be used for assessing the life cycle risk (to life) and environmental impact of a number of possible concept options for new offshore oil and gas developments. The two models can also be used for ranking the designs in terms of lowest human risk and environmental impact. The paper also gives values/criteria for both risks to safety, health and the environment by which the total safety, health and environmental assessment/impact may be balanced as a whole. The paper illustrates the use of the models and shows that the pragmatic or cosmetic improvement to safety, health or the environment may not be advantageous to the overall safety, health and environmental objectives. While the models were developed originally for offshore installations, the basic framework can be readily adapted for use on onshore petrochemical processes.     

What makes a great journal great in the sciences? Which came first,the chicken or the egg?

The paper is concerned with analysing what makes a great journal great in the sciences, based on quantifiable Research Assessment Measures (RAM). Alternative RAM are discussed, with an emphasis on the Thomson Reuters ISI Web of Science database (hereafter ISI). Various ISI RAM that are calculated annually or updated daily are defined and analysed, including the classic 2-year impact factor (2YIF), 5-year impact factor (5YIF), Immediacy (or 0-year impact factor (0YIF)), Eigenfactor, Article Influence, C3PO (Citation Performance Per Paper Online), h-index, Zinfluence, PI-BETA (Papers Ignored—By Even The Authors), Impact Factor Inflation (IFI), and three new RAM, namely Historical Self-citation Threshold Approval Rating (H-STAR), 2 Year Self-citation Threshold Approval Rating (2Y-STAR), and Cited Article Influence (CAI). The RAM data are analysed for the 6 most highly cited journals in 20 highly-varied and well-known ISI categories in the sciences, where the journals are chosen on the basis of 2YIF. The application to these 20 ISI categories could be used as a template for other ISI categories in the sciences and social sciences, and as a benchmark for newer journals in a range of ISI disciplines. In addition to evaluating the 6 most highly cited journals in each of 20 ISI categories, the paper also highlights the similarities and differences in alternative RAM, finds that several RAM capture similar performance characteristics for the most highly cited scientific journals, determines that PI-BETA is not highly correlated with the other RAM, and hence conveys additional information regarding research performance. In order to provide a meta analysis summary of the RAM, which are predominantly ratios, harmonic mean rankings are presented of the 13 RAM for the 6 most highly cited journals in each of the 20 ISI categories. It is shown that emphasizing THE impact factor, specifically the 2-year impact factor, of a journal to the exclusion of other informative RAM can lead to a distorted evaluation of journal performance and influence on different disciplines, especially in view of inflated journal self citations.     

LC-Biosensor System for the Determination of the Neurotoxin β-N-Oxalyl-l-α,β-diaminopropionic Acid

An analysis system is described for the determination of the neurotoxin β-N-oxalyl-l-α,β-diaminopropionic acid (β-ODAP). The system is based on liquid chromatographic separation of β-ODAP from interfering amino acids on an anion exchange column coupled with an amperometric enzyme electrode for the registration of β-ODAP. The electrode is based on a graphite rod modified with an Os(2+/3+) redox polymer cross-linked with l-glutamate oxidase and horseradish peroxidase. This LC-bienzyme electrode analytical system enabled monitoring of as low as 4 μM β-ODAP (injection volume 100 μL). The β-ODAP content in real grass pea samples was measured to range between 3.3 and 5.2 g kg(-)(1) in dry grass pea.     

A correlation of ΔK th-value with the exponent,m, in the equation of fatigue crack growth for various steels

Literature (mainly in Japan) relating to fatigue-crack-growth-data at R=0 in an air environment for a wide range of steels is reviewed with particular attention to the threshold stress intensity, K _th. The collected data are analyzed in terms of the exponent, m(the slope of the linear portion of the log(da/dN)-logD relationship) by taking account of microstructure, material strength, fracture toughness and specimen thickness. The mean rate of fatigue crack growth for ductile steels in the range from the intermediate growth rate to threshold level and the relevant threshold values at R=0, K _th0, can be represented asda/dN = 1.700 × 10^-4(K103.6)^m - 10^-6andK _th0 = 103.6(5.88 × 10^-3)^1/m,where (da/dN) and K are measured by the units of mm/cycle and kgf/mm^3/2, respectively. Contrary to this, in the case of extremely brittle steels with K _IC-value below 200 kgf/mm^3/2 (the fracture occurs by the intergranular separation), the relationships are given byda/dN = 2.893 × 10^-5(K/49.94)^m - 2.5 × 10^-7andK _th0 = 49.94(8.64 × 10^-3)^1/m.

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Résumé La littérature, principalement japonaise, relative aux données sur la propagation des fissures de fatigue pour R=0 dans un environnement d'air et pour une large catégorie d'aciers fait l'objet d'une revue avec une attention particulière pour l'intensité de contrainte de seuil, K _th. Les données collectées sont analysées en terme de l'éxposant m (qui représente la pente de la portion linéaire de la relation log(da/dN)-log K, en tenant compte de la microstructure, de la résistance du matériau, de la ténacité à la rupture et de l'épaisseur de l'éprouvette. La vitesse moyenne de propagation d'une fissure de fatigue dans le cas des aciers ductiles dans la fourchette entre la vitesse intermédiaire de fissuration et le niveau critique, et les valeurs correspondantes de seuil à R=0, K _th0 peuvent être représentées par la relation:da/dN = 1.700 × 10^-4(K103.6)^m - 10^-6etK _th0 = 103.6(5.88 × 10^-3)^1/m,où (da/dN) et K sont mesurés en unités de mm/cycle et en kgf/mm^3/2 respectivement. En contraste, dans le cas d'aciers extrèmement fragiles avec des valeurs K _IC en dessous de 200 kgf/mm^3/2 (la rupture se produit par une séparation intergranulaire), ces relations sont données par:da/dN = 2.893 × 10^-5(K/49.94)^m - 2.5 × 10^-7etK _th0 = 49.94(8.64 × 10^-3)^1/m.

     

Preparation,characterization, and pharmacokinetics of the inclusion complex of genipin-β-cyclodextrin

Objective: The aim of this study was to prepare the inclusion complex of genipin (GP) and β-cyclodextrin (β-CD) with improved stability, solubility, and bioavailability and to study the pharmacokinetics of β-CD inclusion complex in mice. Methods: Lyophilization was employed in the preparation of the inclusion complex of GP–β-CD, whose formation was confirmed by infrared, ultraviolet, differential scanning calorimetry, X-ray diffraction, and phase solubility method. Comparative studies on the in vitro solubility and stability and in vivo evaluation of GP in mice were investigated. Liquid–liquid extraction was used for the isolation of GP in the assay of its concentration. After injection in the caudal vein at equal doses of the inclusion complex of free GP, the drug concentration in mice plasma at fixed time after administration was determined by high-performance liquid chromatography method. Results: The results demonstrated that GP–β-CD solid powders showed improved stability and solubility in aqueous solution, when comparing with free GP. The results of the in vivo study showed that the inclusion complex of GP–β-CD exhibited the dissimilar pharmacokinetics from that of free GP after intravenous administration. The inclusion complex of GP–β-CD displayed longer MRT_0–∞ and higher AUC_0–∞ than free GP did. Conclusions: The relative bioavailability of the inclusion complex of GP–β-CD to free GP was 305.3%, which demonstrated that GP formulations containing β-CD significantly increased the bioavailability.     

Evaluating the performance of the Harshaw™ DXTRAD LiF:Mg,Cu,P finger ring with two different thickness filters

Amongst the dosemeters offered by the Health Protection Agency (HPA) Personal Dosimetry Service are finger rings, which use the Harshaw? DXTRAD element. This paper describes restricted-type testing carried out by HPA on the previously untried combination of the LiF:Mg,Cu,P material and a thicker filter (42 mg cm(-2)). The tests were based on ISO 12794 [International Organization for Standardization. ISO 12794:2000 nuclear energy--radiation protection--individual thermoluminescence dosemeters for the extremities and eyes. ISO (2000)] and included energy and angle dependence of response for photons. The conclusion was, for photon dosimetry applications the thicker filter is acceptable for use in the HPA service.     

Specific heat,pressure, and the Grüneisen relation in solid hydrogen

We report systematic measurements ofC _v and (P/T) _v in solid hydrogen below 1 K and for orthohydrogen molar concentrations 0.58X _ortho0.20. This is the temperature and concentration range associated with a proposed quadrupolar glass phase. The results show no overtly glassy properties such as remanence or hysteresis upon warming and cooling, and there is no evidence of anomalous thermal relaxations. We have calculated the quadrupolar Grüneisen constant from our data and find that is only a slowly varying function of temperature and orthohydrogen concentration. TheC _v results are compared with theoretical models and the behavior of a corresponding classical solid, N₂-argon. There are several similarities between the N₂-argon and H₂ behaviors, but the semiempirical single-particle model does not correspond well with the experimental results.