186 research outputs found
Cubic Nonlinear Optical Properties of Platinum-Terminated Polyynediyl Chains
The wavelength dependence of the cubic nonlinearity of ligated platinum-terminated polyynes trans,trans-{(p-MeC6H4) 3P}2(p-MeC6H4)Pt(C≡C) nPt(p-C6H4Me){P(p-C6H 4Me)3}2 (n = 3-6, 8, 10, 12) has been examined by femtosecond Z-scan studies in the waveleng
Potentiometric Selectivities of Ionophore-Doped Ion-Selective Membranes: Concurrent Presence of Primary Ion or Interfering Ion Complexes of Multiple Stoichiometries
The
selectivities of ionophore-doped ion-selective electrode (ISE)
membranes are controlled by the stability and stoichiometry of the
complexes between the ionophore, L, and the target and interfering
ions (Izi and Jzj, respectively). Well-accepted models predict how these selectivities
can be optimized by selection of ideal ionophore-to-ionic site ratios,
considering complex stoichiometries and ion charges. These models
were developed for systems in which the target and interfering ions
each form complexes of only one stoichiometry. However, for a few
ISEs, the concurrent presence of two primary ion complexes of different
stoichiometries, such as ILzi and IL2zi, was reported. Indeed, similar
systems were probably often overlooked and are, in fact, more common
than the exclusive formation of complexes of higher stoichiometry
unless the ionophore is used in excess. Importantly, misinterpreted
stoichiometries misguide the design of new ionophores and are likely
to result in the formulation of ISE membranes with inferior selectivities.
We show here that the presence of two or more complexes of different
stoichiometries for a given ion may be inferred experimentally from
careful interpretation of the potentiometric selectivities as a function
of the ionophore-to-ionic site ratio or from calculations of complex
concentrations using experimentally determined complex stabilities.
Concurrent formation of JLzj and JL2zj complexes of an interfering ion is shown here to shift the ionophore-to-ionic site ratio that
provides the highest selectivities. Formation of ILn–1zi and ILnzi complexes of a primary ion is less of a concern because an optimized membrane
typically contains an excess of ionophore, but lower than expected
selectivities may be observed if the stepwise complex formation constant, KILn, is not sufficiently large and the ionophore-to-ionic
site ratio does not markedly exceed n
An unexpected insertion of acetone into the silicon–carbon terminus of an sp carbon chain: syntheses and structures of model monoplatinum hexatriynyl and octatetraynyl complexes
Syntheses, structures, and stabilities of aliphatic and aromatic fluorous iodine(I) and iodine(III) compounds::the role of iodine Lewis basicity
The title molecules are sought in connection with various synthetic applications. The aliphatic fluorous alcohols RfnCH2OH (Rfn = CF3(CF2)n–1; n = 11, 13, 15) are converted to the triflates RfnCH2OTf (Tf2O, pyridine; 22–61%) and then to RfnCH2I (NaI, acetone; 58–69%). Subsequent reactions with NaOCl/HCl give iodine(III) dichlorides RfnCH2ICl2 (n = 11, 13; 33–81%), which slowly evolve Cl2. The ethereal fluorous alcohols CF3CF2CF2O(CF(CF3)CF2O)xCF(CF3)CH2OH (x = 2–5) are similarly converted to triflates and then to iodides, but efforts to generate the corresponding dichlorides fail. Substrates lacking a methylene group, RfnI, are also inert, but additions of TMSCl to bis(trifluoroacetates) RfnI(OCOCF3)2 appear to generate RfnICl2, which rapidly evolve Cl2. The aromatic fluorous iodides 1,3-Rf6C6H4I, 1,4-Rf6C6H4I, and 1,3-Rf10C6H4I are prepared from the corresponding diiodides, copper, and RfnI (110–130 °C, 50–60%), and afford quite stable RfnC6H4ICl2 species upon reaction with NaOCl/HCl (80–89%). Iodinations of 1,3-(Rf6)2C6H4 and 1,3-(Rf8CH2CH2)2C6H4 (NIS or I2/H5IO6) give 1,3,5-(Rf6)2C6H3I and 1,2,4-(Rf8CH2CH2)2C6H3I (77–93%). The former, the crystal structure of which is determined, reacts with Cl2 to give a 75:25 ArICl2/ArI mixture, but partial Cl2 evolution occurs upon work-up. The latter gives the easily isolated dichloride 1,2,4-(Rf8CH2CH2)2C6H3ICl2 (89%). The relative thermodynamic ease of dichlorination of these and other iodine(I) compounds is probed by DFT calculations
Experimental Study of the Shortest Reset Word of Random Automata
In this paper we describe an approach to finding the shortest reset word of a
finite synchronizing automaton by using a SAT solver. We use this approach to
perform an experimental study of the length of the shortest reset word of a
finite synchronizing automaton. The largest automata we considered had 100
states. The results of the experiments allow us to formulate a hypothesis that
the length of the shortest reset word of a random finite automaton with
states and 2 input letters with high probability is sublinear with respect to
and can be estimated as $1.95 n^{0.55}.
NA49 Results on Single Particle and Correlation Measurements in Central Pb+Pb Collisions
Single-particle spectra and two-particle correlation functions measured by the NA49 collaboration in central Pb+Pb collisions at 158 GeV/nucleon are presented. These measurements are used to study the kinetic and chemical freeze-out conditions in heavy ion collisions. We conclude that large baryon stopping, high baryon density and strong transverse radial flow are achieved in central Pb+Pb collisions at the SPS.Single-particle spectra and two-particle correlation functions measured by the NA49 collaboration in central Pb+Pb collisions at 158 GeV/nucleon are presented. These measurements are used to study the kinetic and chemical freeze-out conditions in heavy ion collisions. We conclude that large baryon stopping, high baryon density and strong transverse radial flow are achieved in central Pb+Pb collisions at the SPS
Underlying Event measurements in pp collisions at and 7 TeV with the ALICE experiment at the LHC
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