69 research outputs found
Matched ligands for small, stable colloidal nanoparticles of copper, cuprous oxide and cuprous sulfide
This work applies organometallic routes to copper(0/I) nanoparticles and describes how to match ligand chemistries with different material compositions. The syntheses involve reacting an organo-copper precursor, mesitylcopper(I) [CuMes]z (z=4, 5), at low temperatures and in organic solvents, with hydrogen, air or hydrogen sulfide to deliver Cu, Cu2 O or Cu2 S nanoparticles. Use of sub-stoichiometric quantities of protonated ligand (pro-ligand; 0.1-0.2â
equivalents vs. [CuMes]z ) allows saturation of surface coordination sites but avoids excess pro-ligand contaminating the nanoparticle solutions. The pro-ligands are nonanoic acid (HO2 CR1 ), 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (HO2 CR2 ) or di(thio)nonanoic acid, (HS2 CR1 ), and are matched to the metallic, oxide or sulfide nanoparticles. Ligand exchange reactions reveal that copper(0) nanoparticles may be coordinated by carboxylate or di(thio)carboxylate ligands, but Cu2 O is preferentially coordinated by carboxylate ligands and Cu2 S by di(thio)carboxylate ligands. This work highlights the opportunities for organometallic routes to well-defined nanoparticles and the need for appropriate ligand selection
Matched Ligands for Small, Stable Colloidal Nanoparticles of Copper, Cuprous Oxide and Cuprous Sulfide
This work applies organometallic routes to copper(0/I) nanoparticles and describes how to match ligand chemistries with different material compositions. The syntheses involve reacting an organo-copper precursor, mesitylcopper(I) [CuMes]z (z=4, 5), at low temperatures and in organic solvents, with hydrogen, air or hydrogen sulfide to deliver Cu, Cu2O or Cu2S nanoparticles. Use of sub-stoichiometric quantities of protonated ligand (pro-ligand; 0.1â0.2 equivalents vs. [CuMes]z) allows saturation of surface coordination sites but avoids excess pro-ligand contaminating the nanoparticle solutions. The pro-ligands are nonanoic acid (HO2CR1), 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (HO2CR2) or di(thio)nonanoic acid, (HS2CR1), and are matched to the metallic, oxide or sulfide nanoparticles. Ligand exchange reactions reveal that copper(0) nanoparticles may be coordinated by carboxylate or di(thio)carboxylate ligands, but Cu2O is preferentially coordinated by carboxylate ligands and Cu2S by di(thio)carboxylate ligands. This work highlights the opportunities for organometallic routes to well-defined nanoparticles and the need for appropriate ligand selection
New Societal Equations
In a recent paper, W. Haefele established a number of phenomenological equations describing the behavior of a model society. The state variables of this model society were gross national product, population, energy consumption and risk acceptance.
In this paper, the state of the discussion within the IIASA energy project at the time being shall be fixed. Several new sets of equations will be established which extend the set given by Haefele and Manne in the following sense: capital will be included as another state variable; a finite asymptotic population will be assumed; there are several primary energy sources (fossil and nuclear).
We will outline three different approaches, namely: (1) an approach where a complete system of equations, including one primary energy source, is established and where the topological features (separatrices, fix points, etc.) can be studied in detail; (2) a "control theoretical approach," including two primary energy sources, where we limit the number of state variables in such a way that there remains only one "control variable" subject to optimization with respect to an appropriate objective function; and (3) a "linear programming approach" where we introduce the same number of energy supply variables as in the work of Haefele and Manne, and where we optimize the (more than one) free state variables according to different objective functions. The total energy demand is either taken from a model of the first kind or is assumed to be an independent control variable subject to optimization
Stopping and Radial Flow in Central 58Ni + 58Ni Collisions between 1 and 2 AGeV
The production of charged pions, protons and deuterons has been studied in
central collisions of 58Ni on 58Ni at incident beam energies of 1.06, 1.45 and
1.93 AGeV. The dependence of transverse-momentum and rapidity spectra on the
beam energy and on the centrality of the collison is presented. It is shown
that the scaling of the mean rapidity shift of protons established for AGS and
SPS energies is valid down to 1 AGeV. The degree of nuclear stopping is
discussed; the IQMD transport model reproduces the measured proton rapidity
spectra for the most central events reasonably well, but does not show any
sensitivity between the soft and the hard equation of state (EoS). A radial
flow analysis, using the midrapidity transverse-momentum spectra, delivers
freeze-out temperatures T and radial flow velocities beta_r which increase with
beam energy up to 2 AGeV; in comparison to existing data of Au on Au over a
large range of energies only beta_r shows a system size dependence
K^+ production in the reaction at incident energies from 1 to 2 AGeV
Semi-inclusive triple differential multiplicity distributions of positively
charged kaons have been measured over a wide range in rapidity and transverse
mass for central collisions of Ni with Ni nuclei. The transverse
mass () spectra have been studied as a function of rapidity at a beam
energy 1.93 AGeV. The distributions of K^+ mesons are well described by a
single Boltzmann-type function. The spectral slopes are similar to that of the
protons indicating that rescattering plays a significant role in the
propagation of the kaon. Multiplicity densities have been obtained as a
function of rapidity by extrapolating the Boltzmann-type fits to the measured
distributions over the remaining phase space. The total K^+ meson yield has
been determined at beam energies of 1.06, 1.45, and 1.93 AGeV, and is presented
in comparison to existing data. The low total yield indicates that the K^+
meson can not be explained within a hadro-chemical equilibrium scenario,
therefore indicating that the yield does remain sensitive to effects related to
its production processes such as the equation of state of nuclear matter and/or
modifications to the K^+ dispersion relation.Comment: 24 pages Latex (elsart) 7 PS figures to be submitted to Nucl. Phys
Nuclear energy in the public sphere: Anti-nuclear movements vs. industrial lobbies in Spain (1962-1979)
The final publication is available at Springer via http://dx.doi.org/10.1007/s11024-014-9263-0This article examines the role of the Spanish Atomic Forum as the
representative of the nuclear sector in the public arena during the golden years of the
nuclear power industry from the 1960s to 1970s. It focuses on the public image
concerns of the Spanish nuclear lobby and the subsequent information campaigns
launched during the late 1970s to counteract demonstrations by the growing and
heterogeneous anti-nuclear movement. The role of advocacy of nuclear energy by
the Atomic Forum was similar to that in other countries, but the situation in Spain
had some distinguishing features. Anti-nuclear protest in Spain peaked in 1978
paralleling the debates of a new National Energy Plan in Congress, whose first draft
had envisaged a massive nuclearization of the country. We show how the approval
of the Plan in July 1979, with a significant reduction in the nuclear energy component,
was influenced by the anti-nuclear protest movements in Spain. Despite the
efforts of the Spanish Atomic Forum to counter its message, the anti-nuclear
movement was strengthened by reactions to the Three Mile Island accident in March
1979
Central Collisions of Au on Au at 150, 250 and 400 A MeV
Collisions of Au on Au at incident energies of 150, 250 and 400 A MeV were
studied with the FOPI-facility at GSI Darmstadt. Nuclear charge (Z < 16) and
velocity of the products were detected with full azimuthal acceptance at
laboratory angles of 1-30 degrees. Isotope separated light charged particles
were measured with movable multiple telescopes in an angular range of 6-90
degrees. Central collisions representing about 1 % of the reaction cross
section were selected by requiring high total transverse energy, but vanishing
sideflow. The velocity space distributions and yields of the emitted fragments
are reported. The data are analysed in terms of a thermal model including
radial flow. A comparison with predictions of the Quantum Molecular Model is
presented.Comment: LateX text 62 pages, plus six Postscript files with a total of 34
figures, accepted by Nucl.Phys.
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