Stability Constants of Cobalt(II) and Copper(II) Complexes with 3-[(o-Carboxy-p-nitrobenzene)azo]chromotropic Acid and Selective Determination of Copper(II) by Competition Coordination

A method for selective determination of copper(II) based on the reactions of copper(II) or cobalt(II) with 3-[(o-carboxy-p-nitrobenzene)azo]chromotropic acid (CNBAC) at pH = 11.4 was developed. Results have shown that two complexes, Co(CNBAC)2 and Cu(CNBAC), were formed, whose cumulative stability constants were 5.22 × 109 and 7.61 × 105 dm3 mol–1, respectively, and their molar absorption coefficients were 1.19 × 104 and 2.12 × 104 dm3 mol–1 cm–1 at 610 nm. The competition coordination of CuII and CoII with CNBAC was applied for selective determination of CuII by the spectral correction technique. In the absence of any masking reagent, the recommended method was selective and was applied for quantitative determination of copper(II) in river and waste water samples

Langmuir Aggregation of Dahliaviolett on DNA

Formation of double electrostatic films in DNA causes Langmuir aggregation of small ions and molecules only in a monolayer. We studied the interaction of dahliaviolett (DLV) with DNA at pH = 7.24 by a spectral correction technique. Results showed that the ad-sorption ratio of DLV to DNA-P was 1 : 4, the adsorption constant of the DLV-DNA aggregate was 4.44 x 104 and its molar absorption coefficient was 1.02 x 105 dm3 mol-1 cm-1 at 615 nm. This aggregation was applied to the quantitative determination of DNA in samples

Differential isospin-fractionation in dilute asymmetric nuclear matter

The differential isospin-fractionation (IsoF) during the liquid-gas phase transition in dilute asymmetric nuclear matter is studied as a function of nucleon momentum. Within a self-consistent thermal model it is shown that the neutron/proton ratio of the gas phase becomes {\it smaller} than that of the liquid phase for energetic nucleons, although the gas phase is overall more neutron-rich. Clear indications of the differential IsoF consistent with the thermal model predictions are demonstrated within a transport model for heavy-ion reactions. Future comparisons with experimental data will allow us to extract critical information about the momentum dependence of the isovector strong interaction.Comment: Rapid Communication, Phys. Rev. C (2007) in pres

catena-Poly[copper(II)-bis­(μ-2-formyl-6-meth­oxy­phenolato-κ4 O 2,O 1:O 1,O 6)-[(methanol-κO)sodium]-μ-perchlorato-κ2 O:O′]

In the title heterodinuclear complex, [CuNa(C8H7O3)2(ClO4)(CH3OH)]n, the CuII ion is five-coordinated by four O atoms from two 2-formyl-6-meth­oxy­phenolate anions and one O atom from a perchlorate anion in a distorted square-pyramidal geometry. The Na+ ion is six-coordinated by four O atoms from two 2-formyl-6-meth­oxy­phenolate ligands, one O atom of a methanol mol­ecule and one O atom of a perchlorate anion. The perchlorate anions link the Na+ and CuII ions, forming a chain along [010]. O—H⋯O hydrogen bonds connect the chains. π–π inter­actions are present between the benzene rings [centroid–centroid distances = 3.566 (2) and 3.702 (2) Å]. The O atoms of the perchlorate anion are disordered over two sets of sites, with an occupancy ratio of 0.481 (8):0.519 (8)

Pseudogap, Superconducting Energy Scale, and Fermi Arcs in Underdoped Cuprate Superconductors

Through the measurements of magnetic field dependence of specific heat in $La_{2-x}Sr_xCuO_4$ in zero temperature limit, we determined the nodal slope $v_\Delta$ of the quasiparticle gap. It is found that $v_\Delta$ has a very similar doping dependence of the pseudogap temperature $T^*$ or value $\Delta_p$. Meanwhile the virtual maximum gap at ($\pi,0$) derived from $v_\Delta$ is found to follow the simple relation $\Delta_q=0.46k_BT^*$ upon changing the doping concentration. This strongly suggests a close relationship between the pseudogap and superconductivity. It is further found that the superconducting transition temperature is determined by both the residual density of states of the pseudogap phase and the nodal gap slope in the zero temperature limit, namely, $T_c \approx \beta v_\Delta \gamma_n(0)$, where $\gamma_n(0)$ is the extracted zero temperature value of the normal state specific heat coefficient which is proportional to the size of the residual Fermi arc $k_{arc}$. This manifests that the superconductivity may be formed by forming a new gap on the Fermi arcs near nodes below $T_c$. These observations mimic the key predictions of the SU(2) slave boson theory based on the general resonating-valence-bond (RVB) picture.Comment: 6 pages, 6 figures, to be published in Phys. Rev.