calcium dichloride tetra urea was prepared by the reaction of calcium chloride with urea in aqueous solution. the crystals are monoclinic, a= 7.633, b= 12.45 1, c= 8.118 ?,? = 113.17, z = 4, space group p 2,/a. the crystal structure was determined by single crystal x-ray methods and refined to r= 0.041. the calcium atoms are coordinated to four oxygen atoms of urea and to two chloride ions. the...

the structure of n,n'-bis(2-hydroxybenzylidene)-2,2-dimethyl-1,3-propanediamine, c19h22n2o2, has been studied at low temperature (120k) by means of single-crystal x-ray diffraction. solving the structure shows an orthorhombic unit cell, with p212121 space group, z = 4, a = 6.1046 (4) å, b = 15.8349 (11)å, c = 17.2898 (12) å and v = 1671.3 (2) å3. there are two relatively strong hydrogen bonds (...

The reaction of gallium (III) nitrate octahydrate with the proton transfer compound (pydaH2)2+ (pydc)2– ( where  pyda  is 2,6-pyridinediamine and pydcH2 is 2,6-pyridinedicarboxylic acid) leads to the formation of (C5H8N3) [Ga(C7H3NO4)2] · 4H2O · CH3OH. The crystal system of the anionic complex is triclinic with space group Pī and two molecules per unit cell. The unit cell parameters are a=10.23...

Recently, photonic crystals doped with liquid crystal (LC) material havegained much research interest. In this article new ternary one-dimensional photoniccrystal introduced and studied. The liquid crystal layer of 5CB and 5PCH is sandwichedby two dielectric layers. For the first time, we use four structures SiO2/UCF35/CaF2,SiO2/5CB/CaF2, NFK51/UCF35/NPSK53 and NFK51/5CB/NPSK53. The effect ofte...

Introduction:  In  this  study,  we  utilized  the  MCNP4C  Monte  Carlo  code  to  quantitatively  evaluate  the  influence of crystal size and material on intercrystal scatter and parallax effects.   Materials and Methods:  For each of the 5 selected crystals (BGO, LSO, LYSO, LuAP, GSO), transport of  511  keV  photons  originating  from  a  point  source  and  incident  on  the  central  cry...

Abstract— This work investigates the improvement of the active reflection coefficient of waveguide-fed phased-array antenna using liquid crystal layers. The anisotropy properties of liquid crystal layer can be employed to eliminate blind scan angle and improve the wide angle impedance matching of the waveguide-fed phased array antennas. The authors have expressed the modal analysis of the waveg...

The use of a two stage crystal collimation system in the RHIC yellow ring is examined. The system includes a copper beam scraper and a bent silicon crystal. While scrapers were installed in both of the RHIC rings before the year 2000 run, the crystal is installed for the 2001 run in one ring only, forming a two stage collimation system there. We present simulations of the expected channeling th...