نتایج جستجو برای: silica boron

تعداد نتایج: 55027  

Journal: :Environmental Health Perspectives 1994
R F Moseman

Elemental boron was isolated in 1808. It typically occurs in nature as borates hydrated with varying amounts of water. Important compounds are boric acid and borax. Boron compounds are also used in the production of metals, enamels, and glasses. In trace amounts, boron is essential for the growth of many plants, and is found in animal and human tissues at low concentrations. Poisoning in humans...

Journal: :Physical chemistry chemical physics : PCCP 2015
Mounesha N Garaga Ming-Feng Hsieh Zalfa Nour Michael Deschamps Dominique Massiot Bradley F Chmelka Sylvian Cadars

Boron heteroatom distributions are shown to be significantly different in two closely related layered borosilicates synthesized with subtly different alkylammonium surfactant species. The complicated order and disorder near framework boron sites in both borosilicates were characterized at the molecular level by using a combination of multi-dimensional solid-state nuclear magnetic resonance (NMR...

Journal: :پژوهش های خاک 0
مریم آقایی دانش آموخته کارشناسی ارشد دانشگاه تربیت مدرس رسول راهنمایی استادیار دانشگاه تربیت مدرس

plants uptake boron (b) from the soil solution, in which boron concentration is controlled by adsorption and desorption reactions on soil organic and inorganic colloids. considering the importance of aluminosilicate minerals in ion adsorption and desorption reactions in soil, in this research, b adsorption behavior on kaolinite was studied as a function of equilibrium concentration, ph, kaolini...

Journal: :iranian journal of radiation research 0
j.k. kim korea atomic energy research institute, jeongeup, 580-185, south korea t.w. park hyundai ep, bundang, songnam, 463-811, south korea a. cebulska-wasilewska the nenryk niewodniczanski institute of nuclear physics, 31-342 krakōw, poland m. nili dawnesh radiation research institute, 08007 barcelona, spain

background: boron and gadolinium are among the nuclides that hold a unique property of being a neutron capture therapy agent. neutron beams have often a considerable portion of gamma rays with fast neutrons. gamma rays, as beam contaminants, can cause considerable damage to normal tissues even if such tissues do contain high boron concentrations. materials and methods: the modification of radio...

Journal: :BioFactors 2004
Forrest H Nielsen

Female and male rats weighing about 170 g and 200 g, respectively, were fed diets (approximately 70 microg boron/kg) in a factorial arrangement with supplemental boron at 0 (deficient) and 3 (adequate) mg/kg and canola oil or palm oil at 75 g/kg of diet as variables. After 5 weeks, six females in each treatment were bred. Dams and pups continued on their respective dietary treatments through ge...

2017
Takahiro Kondo

Various types of zero, one, and two-dimensional boron nanomaterials such as nanoclusters, nanowires, nanotubes, nanobelts, nanoribbons, nanosheets, and monolayer crystalline sheets named borophene have been experimentally synthesized and identified in the last 20 years. Owing to their low dimensionality, boron nanomaterials have different bonding configurations from those of three-dimensional b...

2002
Gregory S. Kelly

Boron is a trace mineral which is found in highest amounts in fruits, vegetables, nuts, and legumes. Although it has not been demonstrated unequivocally to be an essential nutrient for humans, increasing evidence indicates that boron deficiency and supplementation exert measurable biological effects. Boron has been shown to impact mineral metabolism, brain function and performance, and selected...

Journal: :Nano letters 2013
Liuyan Zhao Mark Levendorf Scott Goncher Theanne Schiros Lucia Pálová Amir Zabet-Khosousi Kwang Taeg Rim Christopher Gutiérrez Dennis Nordlund Cherno Jaye Mark Hybertsen David Reichman George W Flynn Jiwoong Park Abhay N Pasupathy

We use scanning tunneling microscopy and X-ray spectroscopy to characterize the atomic and electronic structure of boron-doped and nitrogen-doped graphene created by chemical vapor deposition on copper substrates. Microscopic measurements show that boron, like nitrogen, incorporates into the carbon lattice primarily in the graphitic form and contributes ~0.5 carriers into the graphene sheet per...

Journal: :Plant physiology 1943
A D Moinat

Lettuce, which is being grown in ever increasing quantities, suffers from a number of nutritional disorders which have been the subject of considerable speculation and study. Much of the difficulty with lettuce is evidently the result of the type of forcinig culture which is used to obtain the most firm and succulent heads. Among the micro-nutrient elements, boron has been given considerable at...

Journal: :Organometallics 2013
Henry Fong Marc-Etienne Moret Yunho Lee Jonas C Peters

Reversible, heterolytic addition of H2 across an iron-boron bond in a ferraboratrane with formal hydride transfer to the boron gives iron-borohydrido-hydride complexes. These compounds catalyze the hydrogenation of alkenes and alkynes to the respective alkanes. Notably, the boron is capable of acting as a shuttle for hydride transfer to substrates. The results are interesting in the context of ...

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