A series of tripodal receptors that are different from each other in their end groups were synthesized. The extraction ability and the transport rate of these receptors were evaluated for transition metal ions (Fe(3+), Ni(2+), Cu(2+), Zn(2+) and Hg(2+)). The receptor bearing pyridyl nitrogens extracted Hg(2+) from a buffered aqueous medium containing a mixture of metal ions and transported it into an organic phase with a complete selectivity over the other metal ions. This receptor was effectively used for transporting Hg(2+) from aqueous buffered source phase to aqueous receiving phase through a chloroform membrane.
[Show abstract][Hide abstract] ABSTRACT: Previously presented interference subspace rejection (ISR)
proposed a family of new efficient multiuser detectors for CDMA. We
reconsider in this paper the modes of ISR using decision feedback (DF).
DF modes share similarities with parallel interference cancellation
(PIC) but attempt to cancel interference by nulling rather than
subtraction. However like the PIC they are prone to wrong tentative
decisions. We propose a modification to DF modes that performs partial
ISR instead of complete interference cancellation. When tentative
decisions are correct, interference is therefore not perfectly rejected
anymore. This drawback is compensated by improved robustness to wrong
tentative decisions. We show that in hard handoff systems, partial ISR
can only provide negligible performance improvements in high loaded
systems outside the region of interest due to out-sector interference.
In situations where both in-sector and out-sector interferences are
cancelled, as may occur in soft handoff situations, BER performance may
improve by more than I dB
[Show abstract][Hide abstract] ABSTRACT: The transport of Cr(VI) from aqueous solutions through bulk liquid membrane was studied using p-tert-butylcalixarene 3-diethylaminopropyl diamide derivative as a carrier. The aqueous solution of potassium dichromate was used as the model contaminant. The kinetic parameters (k1, k2, tmax, Rmmax, Jdmax and Jamax) for the forward and the back extraction were calculated by means of Cr(VI) concentrations of the donor and the acceptor phase. The results showed that it was possible to transport 96.65% of Cr(VI) from the acidic donor solutions to the acceptor solutions at the optimum operating conditions after 10h contact time. The highest transport efficiency was observed at pH 2 in the donor phase and at pH 5 in the acceptor phase. It was shown that the transport of Cr(VI) stem from pH difference between the donor and the acceptor phases. The activation energy values were calculated as 5.77 and 7.99 kJmol−1 for the forward and the back extraction, respectively. It was indicated that the process was diffusionally controlled by dichromate anions. The experimental results demonstrated that p-tert-butylcalixarene derivative was an effective carrier for the transport of Cr(VI).
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