Experimental observation of quantum entanglement in low dimensional spin systems

We report macroscopic magnetic measurements carried out in order to detect and characterize field-induced quantum entanglement in low dimensional spin systems. We analyze the pyroborate MgMnB_2O_5 and the and the warwickite MgTiOBO_3, systems with spin 5/2 and 1/2 respectively. By using the magnetic susceptibility as an entanglement witness we are able to quantify entanglement as a function of temperature and magnetic field. In addition, we experimentally distinguish for the first time a random singlet phase from a Griffiths phase. This analysis opens the possibility of a more detailed characterization of low dimensional materials

Molecular and crystal structure of Sp-thymidin-3'-yl 4-thiothymidin-5'-yl methylphosphonate.

The molecular structure of one diastereomer of the dinucleoside methylphosphonate Tp(Me)sT (1) has been determined by X-ray diffraction methods. The crystal asymmetric unit contains one molecule of 1 and one methanol in an orthorhombic unit cell of dimensions a = 13.241(4), b = 13.844(3), c = 14.944(7) A, space group P2(1)2(1)2(1). Both pyrimidine bases in 1 are oriented anti relative to the 2'-deoxyribose rings, and the sugar conformations are 2E and 2(3)T in the 4-thiothymidine and thymidine moieties, respectively. The deoxyribose-phosphonate backbone has an extended conformation with the bases completely unstacked and almost parallel. The absolute configuration at the phosphorus center in 1 is Sp