114 research outputs found

    Two-dimensional confinement for generating thin single crystals for applications in time-resolved electron diffraction and spectroscopy: an intramolecular proton transfer study

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    Thin single organic crystals (≤1 μm) with large area (≥100 × 100 μm2) are desirable to explore photoinduced processes using ultrafast spectroscopy and electron-diffraction. Here, we present a general method based on spatial confinement to grow such crystals using the prototypical proton transfer system, 1,5-dihydroxyanthraquinone, as an example, and provide the protocol for optically characterizing structural dynamics to enable proper assignments using diffraction methods

    The effects of material formulation and manufacturing process on mechanical and thermal properties of epoxy/clay nanocomposites

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    A holistic study was conducted to investigate the combined effect of three different pre-mixing processes, namely mechanical mixing, ultrasonication and centrifugation, on mechanical and thermal properties of epoxy/clay nanocomposites reinforced with different platelet-like montmorillonite (MMT) clays (Cloisite Na+, Cloisite 10A, Cloisite 15 or Cloisite 93A) at clay contents of 3–10 wt%. Furthermore, the effect of combined pre-mixing processes and material formulation on clay dispersion and corresponding material properties of resulting composites was investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), flexural and Charpy impact tests, Rockwell hardness tests and differential scanning calorimetry (DSC). A high level of clay agglomeration and partially intercalated/exfoliated clay structures were observed regardless of clay type and content. Epoxy/clay nanocomposites demonstrate an overall noticeable improvement of up to 10 % in the glass transition temperature (Tg) compared to that of neat epoxy, which is interpreted by the inclusion of MMT clays acting as rigid fillers to restrict the chain mobility of epoxy matrices. The impact strength of epoxy/clay nanocomposites was also found to increase by up to 24 % with the addition of 3 wt% Cloisite Na+ clays. However, their flexural strength and hardness diminished when compared to those of neat epoxy, arising from several effects including clay agglomeration, widely distributed microvoids and microcracks as well as weak interfacial bonding between clay particles and epoxy matrices, as confirmed from TEM and SEM results. Overall, it is suggested that an improved technique should be used for the combination of pre-mixing processes in order to achieve the optimal manufacturing condition of uniform clay dispersion and minimal void contents

    New AMS 14C dates track the arrival and spread of broomcorn millet cultivation and agricultural change in prehistoric Europe

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    Broomcorn millet (Panicum miliaceum L.) is not one of the founder crops domesticated in Southwest Asia in the early Holocene, but was domesticated in northeast China by 6000 bc. In Europe, millet was reported in Early Neolithic contexts formed by 6000 bc, but recent radiocarbon dating of a dozen 'early' grains cast doubt on these claims. Archaeobotanical evidence reveals that millet was common in Europe from the 2nd millennium bc, when major societal and economic transformations took place in the Bronze Age. We conducted an extensive programme of AMS-dating of charred broomcorn millet grains from 75 prehistoric sites in Europe. Our Bayesian model reveals that millet cultivation began in Europe at the earliest during the sixteenth century bc, and spread rapidly during the fifteenth/fourteenth centuries bc. Broomcorn millet succeeds in exceptionally wide range of growing conditions and completes its lifecycle in less than three summer months. Offering an additional harvest and thus surplus food/fodder, it likely was a transformative innovation in European prehistoric agriculture previously based mainly on (winter) cropping of wheat and barley. We provide a new, high-resolution chronological framework for this key agricultural development that likely contributed to far-reaching changes in lifestyle in late 2nd millennium bc Europe

    Pentalogy of Cantrell: two patients and a review to determine prognostic factors for optimal approach

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    Two patients with incomplete pentalogy of Cantrell are described. The first was a girl with a large omphalocele with evisceration of the heart, liver and intestines with an intact sternum. Echocardiography showed profound intracardiac defects. The girl died 33 h after birth. The second patient was a female fetus with ectopia cordis (EC) without intracardiac anomalies; a large omphalocele with evisceration of the heart, stomach, spleen and liver; a hypoplastic sternum and rib cage; and a scoliosis. The pregnancy was terminated. A review of patients described in the literature is presented with the intention of finding prognostic factors for an optimal approach to patients with the pentalogy of Cantrell. In conclusion the prognosis seems to be poorer in patients with the complete form of pentalogy of Cantrell, EC, and patients with associated anomalies. Intracardial defects do not seem to be a prognostic factor

    Long term in-vivo studies of a photo-oxidized bovine osteochondral transplant in sheep

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    BACKGROUND: Articular cartilage has limited capacity to repair. Defects greater than 3 mm heal with formation of inferior fibrous cartilage. Therefore, many attempts have been made to find the ideal graft for larger cartilage lesions. Different grafts, such as untreated or cryopreserved osteochondral transplants, have been used with variable success. METHODS: Photo-oxidized osteochondral grafts were implanted in both femoral condyles of one ovine knee. Untreated xenogeneic and autogeneic grafts served as controls. Three groups of 8 sheep each were formed and they were sacrificed 6, 12 or 18 months after surgery. RESULTS: The macroscopic evaluation of the condyle and graft showed a well-maintained cartilage surface in most grafts at all time points. However, the host cartilage matrix deteriorated considerably in all xenogeneic, most autogeneic and fewer of the photo-oxidized grafts at 12 and 18 months, respectively. The blue colour of the photo-oxidized grafts resulting from the process of photo-oxidation was visible in all grafts at 6 months, had diminished at 12 months and had completely disappeared at 18 months after surgery. Histologically a loss of matrix staining was almost never noticed in untreated xenografts, transiently at 6 months in photo-oxidized grafts and increased at 12 and 18 months. Fusion between graft and host cartilage could be seen in photo-oxidized grafts at 12 and 18 months, but was never seen in autografts and xenografts. CONCLUSIONS: The photo-oxidation of osteochondral grafts and its use as transplant appears to have a beneficial effect on cartilage and bone remodelling. Osteochondral grafts pre-treated with photo-oxidation may be considered for articular cartilage replacement and therefore may delay artificial joint replacements in human patients

    Honey, a Gift from Nature to Health and Beauty: A Review

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    Benefits of honey are contributed by the composition of its elements such as glucose, fructose, glucose oxidase, vitamins and phenolic compounds. For health, honey can be used to treat wounds due to the antibacterial activity conferred by the hydrogen peroxide produced by glucose oxidase in honey. Anti-inflammatory, anti-oxidant, deodorizing and tissue regeneration activities in honey also help in the wound healing process. It can also be an alternative sweetener for diabetic patients to ensure compliance to a healthy diet. Moreover, honey exerts several effects such as lowering low density lipids and increasing high density lipids, thus reducing risk of atherosclerosis. In terms of beauty, honey can be used on skin and hair. It moisturizes skin through its natural humectant properties contributed by high contents of fructose and glucose. Honey treats acne on the skin due to its antibacterial activity, anti-inflammatory action and tissue repair. The hair can benefit from honey in such a way that the hair has abundance, and becomes easier to comb. However, there have not been as many studies regarding the use of honey in skin in comparison to its use for health. Therefore, future studies on honey could research its use, action and benefits in both cosmetics and dermatology

    Comments on a Double Mummy Containing a Spear Thrower in the "Anker Nielsen Collection", Iquique, Northern Chile

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    Este estudio describe y discute un fardo funerario encontrado en Patillos 2, un sitio en la costa meridional de Chile ubicado a 58 kilómetros al sur de la ciudad de Iquique. Las momias pertenecen a la "Anker Nielsen Collection" del Museo Arqueológico de la Universidad de Chile, Iquique. El fardo contiene los cadáveres momificados de dos niños y una estólica. Para poner esta información en su contexto, hemos resumido lo que se conoce con respecto a la Cultura Chinchorro y a otras manifestaciones culturales en el norte de Chile. En cuanto a la estólica encontrada dentro del fardo funerario se trata, probablemente, de uno de los hallazgos más antiguos de Sudamérica publicado hasta la fecha. Eventualmente, su objetivo fue sujetar firmemente las momias e impedir que éstas se rompieran. Por otro lado, no se puede descartar la posibilidad de que cumplía un fin "mágico", "simbólico" o "ceremonial"

    El arco en América: Evidencia temprana y directa de la Cultura Chinchorro (Norte del Chile)

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    Se presenta en este trabajo la evidencia directa más temprana del uso del arco en América. Consiste en un arco de unos 1,56 ms de longitud que apareció en el cuerpo de una momia artificial formando parte de su estructura de sostén. Esta momia pertenece a la llamada Cultura Chinchorro que existió en la costa norte de Chile entre los 3000 y 1000 años antes de Cristo. Se compara esta evidencia con la que presentan otras fases culturales más tardías del área y, también, se reinterpretan las hipótesis generales que se han propuesto para América en relación con el origen y la antigüedad de este elemento

    Momificación artificial en el Pacífico Sur, ¿paralelismo o difusión?

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    Se describe y compara la momificación artificial que se practicaba en épocas históricas en Melanesia y aquella que aparece en épocas precolombinas en América (Cultura Chinchorro, Chile), las que presentan grandes similitudes a pesar de estar separadas por más de 10.000kmsen el espacio y 5000 años en el tiempo. De acuerdo con el conocimiento actual que se tiene acerca del desarrollo cultural en ambas regiones y con la ausencia de este tipo de momificación en otras áreas, se estima éste como un caso de paralelismo cultural
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