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排序方式： 共有1747条查询结果，搜索用时 15 毫秒
141.
Nai-Hao Yin Anthony W. Parker Pavel Matousek Helen L. Birch 《International journal of molecular sciences》2022,23(23)
The purpose of this study is to determine whether age-related changes to tendon matrix molecules can be detected using Raman spectroscopy. Raman spectra were collected from human Achilles (n = 8) and tibialis anterior (n = 8) tendon tissue excised from young (17 ± 3 years) and old (72 ± 7 years) age groups. Normalised Raman spectra underwent principal component analysis (PCA), to objectively identify differences between age groups and tendon types. Certain Raman band intensities were correlated with levels of advanced glycation end-product (AGE) collagen crosslinks, quantified using conventional destructive biochemistry techniques. Achilles and tibialis anterior tendons in the old age group demonstrated significantly higher overall Raman intensities and fluorescence levels compared to young tendons. PCA was able to distinguish young and old age groups and different tendon types. Raman intensities differed significantly for several bands, including those previously associated with AGE crosslinks, where a significant positive correlation with biochemical measures was demonstrated. Differences in Raman spectra between old and young tendon tissue and correlation with AGE crosslinks provides the basis for quantifying age-related chemical modifications to tendon matrix molecules in intact tissue. Our results suggest that Raman spectroscopy may provide a powerful tool to assess tendon health and vitality in the future. 相似文献
142.
143.
Undecylenic acid, glycerol, and CO2 were used as building blocks for obtaining a fully bio-based carbonated monomer, useful for polyurethanes. The functionality of the monomer was close to 3 cyclic carbonates/mol, located in terminal positions. In a first stage, a synthetic triglyceride was obtained with 99% selectivity by esterification of glycerol and undecylenic acid at 160°C. The triglyceride was then epoxidized using H2O2 and Amberlyst 15 or Amberlite IR-120 acidic exchange resins at 57°C. The selectivity to epoxide was kept constant at 98% using Amberlite IR-120. Terminal cyclic carbonates were then inserted through epoxide moieties under mild conditions by the chemical fixation of CO2 at 80°C and 6 MPa in 6 h. A complete conversion was obtained in 6 h reaction while the selectivity to carbonate groups was near to 99% during all the reaction time. An elastomeric polyhydroxyurethane was obtained by aminolysis of the carbonated monomer with ethylenediamine at 70°C, affording a Young's modulus of 22.6 MPa and Tg of −15.2°C. The material showed a good thermal stability below 240°C. 相似文献
144.
Quanxiang Yan Tao Zhang Christine O'Connor James W. Barlow John Walsh Gaia Scalabrino Feng Xu Helen Sheridan 《Food Science & Nutrition》2023,11(4):1634-1656
Vitamin K1 (VitK1) and Vitamin K2 (VitK2), two important naturally occurring micronutrients in the VitK family, found, respectively, in green leafy plants and algae (VitK1) and animal and fermented foods (VitK2). The present review explores the multiple biological functions of VitK2 from recently published in vitro and in vivo studies, including promotion of osteogenesis, prevention of calcification, relief of menopausal symptoms, enhancement of mitochondrial energy release, hepato- and neuro-protective effects, and possible use in treatment of coronavirus disease. The mechanisms of action associated with these biological effects are also explored. Overall, the findings presented here suggest that VitK, especially VitK2, is an important nutrient family for the normal functioning of human health. It acts on almost all major body systems and directly or indirectly participates in and regulates hundreds of physiological or pathological processes. However, as biological and clinical data are still inconsistent and conflicting, more in-depth investigations are warranted to elucidate its potential as a therapeutic strategy to prevent and treat a range of disease conditions. 相似文献
145.
Ashleigh Massam Helen Smith Valeriya Filipova Simon Waller Nurfashareena Muhamad Joy Jacqueline Pereira 《Journal of Flood Risk Management》2023,16(3):e12907
A novel approach to consider local-scale defence infrastructure in an urban environment, coupled with a broadscale hydraulic model framework, is applied to the capital city of Kuala Lumpur, Malaysia. Broadscale hydraulic modelling frameworks are often able to employ more complex models, but are typically limited to homogenous decision-making to ensure standardised outputs across large regions. Conversely, small-scale hydraulic modelling frameworks tend to better integrate local-scale features but can be computationally expensive to scale up beyond a regional view. Improvements to the broadscale hydraulic model framework through the incorporation of defence systems yield a more accurate representation of fluvial flood risk. This study incorporates defences in Kuala Lumpur, yielding a reduction in our estimates of fluvial flood extent by around 40%. The results of this study are validated against a set of high-quality observations, demonstrating the capability of the model framework in capturing flood risk in more than 95% of known flood risk zones in the city. Incorporating defence infrastructure using data-driven decision making and existing functionality in the hydraulic model could be automated in future model builds. This new approach bridges the gap between local-scale model frameworks and the broadscale, homogenous 2D hydraulic modelling studies. 相似文献
146.
Baptiste Wilmet Jacques Callebert Robert Duvoisin Ruben Goulet Christophe Tourain Christelle Michiels Helen Frederiksen Frank Schaeffel Olivier Marre Jos Alain Sahel Isabelle Audo Serge Picaud Christina Zeitz 《International journal of molecular sciences》2023,24(1)
Mutations in GPR179 are one of the most common causes of autosomal recessive complete congenital stationary night blindness (cCSNB). This retinal disease is characterized in patients by impaired dim and night vision, associated with other ocular symptoms, including high myopia. cCSNB is caused by a complete loss of signal transmission from photoreceptors to ON-bipolar cells. In this study, we hypothesized that the lack of Gpr179 and the subsequent impaired ON-pathway could lead to myopic features in a mouse model of cCSNB. Using ultra performance liquid chromatography, we show that adult Gpr179−/− mice have a significant decrease in both retinal dopamine and 3,4-dihydroxyphenylacetic acid, compared to Gpr179+/+ mice. This alteration of the dopaminergic system is thought to be correlated with an increased susceptibility to lens-induced myopia but does not affect the natural refractive development. Altogether, our data added a novel myopia model, which could be used to identify therapeutic interventions. 相似文献
147.
Passage-time densities are important for the detailed performance analysis of distributed computer and communicating systems. We provide a proof and demonstration of a practical iterative algorithm for extracting complete passage-time densities from expressive semi-Markov systems. We end by showing its application to a distributed web-server cluster model of 15.9 million states. 相似文献
148.
This paper examines how the use of novel hybrid inorganic membrane technology is enabling natural gas processing and the production of high density hydrogen without any impurities. 相似文献
149.
Helen H. Franzwa 《The Journal of communication》1974,24(2):104-109
150.
Two fluorescent lipids were isolated from a chloroform-methanol (2∶1 v/v) extract of bovine brain white matter by two-step
preparative thin layer chromatography on Silica Gel G. The first step was performed with chloroform-diethyl ether-acetic acid
(70∶30∶1 v/v) as developing solvent and revealed a single fluorescent band below the solvent front. The band was scraped off,
and the lipid was eluted in chloroform and reapplied to Silica Gel G plates. In the second step, benzene-methanol-ethyl acetate
(85∶10∶5 v/v) as developing solvent revealed two fluoresent bands (A and B) with Rf values of 0.72 and 0.65. The lipids were eluted and the UV and visible absorption spectra were measured in heptane, as were
the excitation and fluorescence spectra. Sulfuric acid absorption spectra (2 and 24 hr treatment at 22 C) as well as the resulting
excitation and fluorescence spectra were also determined. The fluorescent lipids reacted positively in a number of nonspecific
color tests for steroids, but the chemical nature of these minor components of the neutral lipid fraction remains to be established. 相似文献