نتایج جستجو برای: boron wheel molecules

تعداد نتایج: 225222  

2013
Yafang Xue Qian Liu Guanjie He Kaibing Xu Lin Jiang Xianghua Hu Junqing Hu

The insulator characteristic of hexagonal boron nitride limits its applications in microelectronics. In this paper, the fluorinated hexagonal boron nitride nanosheets were prepared by doping fluorine into the boron nitride nanosheets exfoliated from the bulk boron nitride in isopropanol via a facile chemical solution method with fluoboric acid; interestingly, these boron nitride nanosheets demo...

2005
Rolf L. Romer Anette Meixner

The isotopic analysis of boron from material that carries only trace amounts of boron requires low boron blank levels. Large efforts are taken to keep blank levels low by purifying reagents. We performed exposure experiments and determined procedure blanks before and after the air-handling system was modified from silicate glass filters to polyethylene/polystyrole and active carbon filters. Our...

2008
Nevill Gonzalez Szwacki

A family of unusually stable boron cages was identified and examined using first-principles local-density functional method. The structure of the fullerenes is similar to that of the B12 icosahedron and consists of six crossing double-rings. The energetically most stable fullerene is made up of 180 boron atoms. A connection between the fullerene family and its precursors, boron sheets, is made....

2008
Jens Kunstmann Alexander Quandt

Based on an ab initio study, we present a structure model for a broad boron sheet, which is the precursor of boron nanotubes. Furthermore we could show that, in contrast to the armchair types, zigzag boron nanotubes have no surface tension (strain energy). As result, we predict that boron nanotubes will exhibit a chirality dependent stability, something that is unique among all nanotubular mate...

Journal: :Physical review letters 2007
I Suarez-Martinez A A El-Barbary G Savini M I Heggie

Boron strongly modifies electronic and diffusion properties of graphite. We report the first ab initio study of boron interaction with the point defects in graphite, which includes structures, thermodynamics, and diffusion. A number of possible diffusion mechanisms of boron in graphite are suggested. We conclude that boron diffuses in graphite by a kick-out mechanism. This mechanism explains th...

2012
Mehmet Bozkurt Kamil Küçükyılmaz Abdullah Uğur Çatlı Mustafa Çınar Metin Çabuk Erol Bintaş

Three levels of boron (0, 30, 60 ppm) were supplemented in practical corn-soybean based starter and grower diets, containing either adequate or inadequate Ca or P. A total of 1,800, 1-day-old sexed broiler chicks were assigned to six dietary treatments and fed with the experimental diets for 42 days. Boron improved the overall feed conversion ratio, but increased body weight only at 21 days of ...

ژورنال: علوم آب و خاک 2009
تدین, محمدسعید, معافپوریان, غلامرضا,

In arid and semi arid regions with high boron content in irrigation water, boron toxicity is a considerable problem. Critical levels of boron in irrigation water variy between 1 and 10 mg/l for sensitive and resistant plants, respectively. In southern parts of Iran especially large citrus production region as Jahrom and Giroft cities, high boron content in irrigation water at toxic levels in mo...

تدین, محمدسعید, معافپوریان, غلامرضا,

In arid and semi arid regions with high boron content in irrigation water, boron toxicity is a considerable problem. Critical levels of boron in irrigation water variy between 1 and 10 mg/l for sensitive and resistant plants, respectively. In southern parts of Iran especially large citrus production region as Jahrom and Giroft cities, high boron content in irrigation water at toxic levels in mo...

Journal: :Environmental Health Perspectives 1994
D G Blevins K M Lukaszewski

Boron has been recognized since 1923 as an essential micronutrient element for higher plants. Over the years, many roles for boron in plants have been proposed, including functions in sugar transport, cell wall synthesis and lignification, cell wall structure, carbohydrate metabolism, RNA metabolism, respiration, indole acetic acid metabolism, phenol metabolism and membrane transport. However, ...

Journal: :آب و خاک 0
مجتبی مقبلی محسن فرحبخش ناصر برومند

introduction: boron (b) is an essential plant micronutrient whose soil availability is influenced by many soil factors.understanding the processes controling activity of boron (b) in the soil solution is important for soil fertility management. the reaction of adsorption and desorption of boron in soil determines the amount of boron that is available to plants. adsorption–desorption processes p...

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