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51.
Schoolyard Shade and Sun Exposure: Assessment of Personal Monitoring During Children's Physical Activity 下载免费PDF全文
Jennifer K. Vanos Grant R. McKercher Kylie Naughton Marc Lochbaum 《Photochemistry and photobiology》2017,93(4):1123-1132
Childhood exposure to ultraviolet radiation (UVR) is a major risk factor for the development of melanoma later in life. However, it is challenging to accurately determine personal outdoor exposure to UVR, specifically erythemally weighted UVR (UVEry), due to technological constraints, variable time–activity patterns, and the influence of outdoor environmental design. To address this challenge, this study utilized mobile and stationary techniques to examine the UVEry exposures of 14 children in a schoolyard in Lubbock, TX, in spring 2016. The aims of the study were to examine the influence of artificial shade on personal UVEry exposures and to assess full sun exposure ratios (ERs) within the same playground microenvironment. On average, personal wrist dosimeters worn during play in the sun measured 18% of the total onsite UVEry measured by a stationary UV pyranometer. Shade was found to significantly reduce the personal UVEry exposures by 55%, UVB280–315 nm exposures by 91%, and the overall solar radiation by 84%. Substantial benefits can be garnered through focused design of children's recreational space to utilize shade—both natural and artificial—to reduce UVR exposures during play, and to extend safe outdoor stays. Finally, although the wrist is a practical location for a dosimeter, it often underestimates full exposures, particularly during physical activity. 相似文献
52.
Activation of Molecular Hydrogen by Bis(η5,η1‐pentafulvene)‐titanium Complexes – Efficient Formation of Titanium(III)hydrides 下载免费PDF全文
The synthesis and crystal structures of two dinuclear titanocene hydride complexes are reported. Both complexes, namely bis(η5‐(di‐para‐tolylmethyl)cyclopentadienyl)titanium hydride dimer, [(η5‐C20H19)2Ti(μ‐H)]2 ( 2a ), and bis(η5‐2‐adamantylcyclopentadienyl)‐titanium hydride dimer, [(η5‐C15H19)2Ti(μ‐H)]2 ( 2b ), are formed via activation of molecular hydrogen by the corresponding bis(η5,η1‐pentafulvene)titanium complexes 1a and 1b at ambient temperatures and pressures in high yields. The hydride complexes 2a and 2b exhibit planar [Ti2H2] cores and, as a result of the heterolytic cleavage of molecular hydrogen, substituted Cp Ligands were formed during the reaction. 相似文献
53.
Imines in the Titanium Coordination Sphere – Transformation of Imidoyl Chlorides to Nitrilium Ions 下载免费PDF全文
In the reaction of TiCl4 in benzene as solvent with the imidoyl chloride p‐Tolyl(Cl)C=NPh ( 1 ) the abstraction of the chloride substituent is observed, leading to the nitrilium salt [p‐Tolyl–C≡N–Ph]+[Ti2Cl9]– ( 2 ) in quantitative yield. The highly electrophilic salt 2 is characterized by IR‐ and NMR spectroscopy. The observed band for the C≡N stretching mode of 2 clearly indicates the formation of a nitrilium ion. Especially a characteristic line broadening of the 13C{1H}‐NMR signals related to carbon atoms next to the nitrogen is observed. By 15N,1H‐HMBC NMR experiments it is shown that the nitrogen signal of 2 is significantly shifted to high‐field in relation to nitriles and imines. The molecular structure of 2 was confirmed by single‐crystal X‐ray diffraction. The C≡N bond length and the linearity of the C–C≡N–C unit in 2 confirm the triple bond character of this bond. 相似文献
54.
Reis Thaiene A. Matos Breno N. Lima Eliana M. Chaker Juliano A. Gratieri Tais Cunha-Filho Marcílio S. S. Gelfuso Guilherme M. 《Journal of Thermal Analysis and Calorimetry》2017,128(3):1671-1682
Journal of Thermal Analysis and Calorimetry - The objectives of this study were to verify the viability of the photoinitiating system using curcumin as a photoinitiator and glycerol as a... 相似文献
55.
This paper shows that monotone self-dual Boolean functions in irredundant disjuntive normal form (IDNF) do not have more variables than disjuncts. Monotone self-dual Boolean functions in IDNF with the same number of variables and disjuncts are examined. An algorithm is proposed to test whether a monotone Boolean function in IDNF with n variables and n disjuncts is self-dual. The runtime of the algorithm is O(n3). 相似文献
56.
Marc P. Renault 《Central European Journal of Operations Research》2017,25(4):953-966
This paper studies the problem of maximizing the number of items packed into n bins, known as the dual bin packing problem, in the advice per request model. In general, no online algorithm has a constant competitive ratio for this problem. An online algorithm with 1 bit of advice per request is shown to be 3/2-competitive. Next, for \(0< \varepsilon < 1{/}2\), an online algorithm with advice that is \((1/(1-\varepsilon ))\)-competitive and uses \({O}(1/\varepsilon )\) bits of advice per request is presented. 相似文献
57.
Cathodic corrosion is an enigmatic electrochemical process that etches metallic electrodes at potentials below 0 V versus the normal hydrogen electrode. Although this phenomenon was discovered in the late 1800s by Fritz Haber, it remained mostly unnoticed during the 20th century and only attracted increased attention in the past decade. This recent attention has generated marked improvements in both the fundamental knowledge and the applications of cathodic corrosion. Fundamental new insights were gained into the effects and possible reaction intermediates of cathodic corrosion. Complementing these insights, recent advances involve applications of cathodic corrosion for nanoparticle synthesis and electrocatalyst modification. Both these applied and fundamental advances will be discussed in this short review on cathodic corrosion. 相似文献
58.
Localized pH measurements are important in various areas of electrochemistry, from corrosion to bio-electrochemistry and electrocatalysis. Different techniques are available to perform these measurements and offer numerous possibilities in terms of spatial and temporal resolution, sensitivity, and precision. In this brief review we present the recent progress made and summarize the main techniques available for localized pH measurements in electrochemistry such as scanning probe techniques (SECM, SICM, SIET), laser (confocal) fluorescence microscopy, rotating ring-disc electrode (RRDE) voltammetry, and infra-red spectroscopy, among others. 相似文献
59.
Holly E. Bonfield Dr. Damien Valette Dr. David M. Lindsay Dr. Marc Reid 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(1):158-174
Exploration of novel, three-dimensional chemical space is of growing interest in the drug discovery community and with this comes the challenge for synthetic chemists to devise new stereoselective methods to introduce chirality in a rapid and efficient manner. This Minireview provides a timely summary of the development of palladium-catalyzed asymmetric redox-relay Heck-type processes. These reactions represent an important class of transformation for the selective introduction of remote stereocenters, and have risen to prominence over the past decade. Within this Minireview, the vast scope of these transformations will be showcased, alongside applications to pharmaceutically relevant chiral building blocks and drug substances. To complement this overview, a mechanistic summary and discussion of the current limitations of the transformation are presented, followed by an outlook on future areas of investigation. 相似文献
60.
Dr. Selina Beatrice van der Meer Theresa Seiler Christin Buchmann Georgia Partalidou Dr. Sophia Boden Dr. Kateryna Loza Dr. Marc Heggen Dr. Jürgen Linders Dr. Oleg Prymak Prof. Dr. Cristiano L. P. Oliveira Prof. Dr. Laura Hartmann Prof. Dr. Matthias Epple 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(4):1451-1464
Ultrasmall gold nanoparticles (diameter about 2 nm) were surface-functionalized with cysteine-carrying precision macromolecules. These consisted of sequence-defined oligo(amidoamine)s (OAAs) with either two or six cysteine molecules for binding to the gold surface and either with or without a PEG chain (3400 Da). They were characterized by 1H NMR spectroscopy, 1H NMR diffusion-ordered spectroscopy (DOSY), small-angle X-ray scattering (SAXS), and high-resolution transmission electron microscopy. The number of precision macromolecules per nanoparticle was determined after fluorescent labeling by UV spectroscopy and also by quantitative 1H NMR spectroscopy. Each nanoparticle carried between 40 and 100 OAA ligands, depending on the number of cysteine units per OAA. The footprint of each ligand was about 0.074 nm2 per cysteine molecule. OAAs are well suited to stabilize ultrasmall gold nanoparticles by selective surface conjugation and can be used to selectively cover their surface. The presence of the PEG chain considerably increased the hydrodynamic diameter of both dissolved macromolecules and macromolecule-conjugated gold nanoparticles. 相似文献