The American Constitution : democratic 'checks and balances'

In July 1976, the United States of America will be celebrating the bicentenary of the adoption of the Declaration of Independence and, naturally, a whole nation will be nostalgically reviewing the many landmarks which colour and give meaning to the two hundred years of United States history. As usually happens on such occasions, special attention will be devoted co the very origins of the United States and, no doubt, also to the day when the thirteen rebellious former British colonial settlements took the plunge and decided to draft a constitution that would unite this nation, still in its early stages of existence, as well as to its eventual development into the really democratic and, at the same time, practical instrument of government which America has today.peer-reviewe

Many-spin effects in inelastic neutron scattering and electron paramagnetic resonance of molecular nanomagnets

Many molecular magnetic clusters, such as single-molecule magnets, are characterized by spin ground states with defined total spin S exhibiting zero-field-splittings. In this work, the spectroscopic intensities of the transitions within the ground-state multiplet are analyzed. In particular, the effects of a mixing with higher-lying spin multiplets, which is produced by anisotropic interactions and is neglected in the standard single-spin description, are investigated systematically for the two experimental techniques of inelastic neutron scattering (INS) and electron paramagnetic resonance (EPR), with emphasis on the former technique. The spectroscopic transition intensities are calculated analytically by constructing corresponding effective spin operators perturbationally up to second order and consequently using irreducible tensor operator techniques. Three main effects of spin mixing are observed. Firstly, a pronounced dependence of the INS intensities on the momentum transfer Q, with a typical oscillatory behavior, emerges in first order, signaling the many-spin nature of the wave functions in exchange-coupled clusters. Secondly, as compared to the results of a first-order calculation, the intensities of the transitions within the spin multiplet are affected differently by spin mixing. This allows one, thirdly, to differentiate the higher-order contributions to the cluster magnetic anisotropy which come from the single-ion ligand-field terms and spin mixing, respectively. The analytical results are illustrated by means of the three examples of an antiferromagnetic heteronuclear dimer, the Mn-[3 x 3] grid molecule, and the single-molecule magnet Mn12.Comment: 18 pages, 3 figures, REVTEX4, to appear in PR

RELATION BETWEEN BIRTH WEIGHT OF LAMBS AND MILK PRODUCTION IN EWES

Čini se da je proizvodnja mlijeka u ovaca povezana s težinom janjadi pri janjenju. To se vjerojatno može pripisati laktogenom hormonu placente čije izlučivanje ovisi o težini placente. Obavljena su 4 pokusna ispitivanja, 2 na ovcama Sarda (S) i 2 na Merino(M) i Awassi x Merino (A x M) ovcama, u razdoblju izmedu 5. i 8. tjedna post partum. Sakupljeni su podaci o tjelesnoj težini ovaca, težini janjadi pri janjenju i proizvodnji mlijeka. Analize linearne regresile između grama janjadi kod janjenja na kg tjelesne težine ovce te grama mlijeka proizvedenog na kg tjelesne težine ovce pokazuju da su ove dvije varijable u pozitivnoj uzajamnoj vezi i da uklanjanje mlijeka u slučaju janjaca blizanaca povećava davanje mlijeka.Milk production in sheep seem to be related to lamb weight at birth. This is probably due to the lactogen placental hormone whose secretion depends on the weight of the placenta. 4 experimental trials were carried out, 2 on Sarda ewes (S) and 2 on Merino (M) and Awasi x Merino (A x M) ewes, during the period between 5-th and 8-th week post partum. Data of body weight of ewes, weight at birth weight of lambs and milk production were collecteds. Linear regresion analysis between grams of lamb at birth per kg of ewe\u27s body weight and grams of milk produced per kg of ewe\u27s body weight show that the two variables are positively correlated and that milk removal by twin lambs increased milk yield

Field-induced level crossings in spin clusters: Thermodynamics and magneto-elastic instability

Quantum spin clusters with dominant antiferromagnetic Heisenberg exchange interactions typically exhibit a sequence of field-induced level crossings in the ground state as function of magnetic field. For fields near a level crossing, the cluster can be approximated by a two-level Hamiltonian at low temperatures. Perturbations, such as magnetic anisotropy or spin-phonon coupling, sensitively affect the behavior at the level-crossing points. The general two-level Hamiltonian of the spin system is derived in first-order perturbation theory, and the thermodynamic functions magnetization, magnetic torque, and magnetic specific heat are calculated. Then a magneto-elastic coupling is introduced and the effective two-level Hamilitonian for the spin-lattice system derived in the adiabatic approximation of the phonons. At the level crossings the system becomes unconditionally unstable against lattice distortions due to the effects of magnetic anisotropy. The resultant magneto-elastic instabilities at the level crossings are discussed, as well as the magnetic behavior.Comment: 13 pages, 8 figures, REVTEX

Thermal anomalies and fluid geochemistry framework in occurrence of the 2000-2001 Nizza Monferrate seismic sequence (northern Italy): Episodic changes in the fault zone heat flow or chemical mixing phenomena?

International audienceThe paper discusses the correlation between the heating of shallow groundwater over a 10 × 20 km wide area close to the town of Nizza Monferrato (Piemonte Region, Northern Italy) and the concomitant local seismic sequences during the period August 2000 ? July 2001. The first seismic sequence started on 21 August 2000 with a Ml = 5.2 earthquake. Within few hours, the local authorities received calls alerting that the groundwater temperature rose from 10 to 30°C in many shallow wells. Our geochemical experimental data and the geological-seismotectonic framework do not allow the hypothesis of simple fluid mixing between the thermal reservoir of Acqui Terme and the Nizza-Monferrato shallow groundwater to explain the observed thermal anomalies. On the other hand, we invoke more complex processes such as frictional heating, mechano-chemistry, fault-valve mechanism, adiabatic decompression and hydrogeologically driven heat flow i.e., thermal effects due to variations of basin-scale permeability field. All these processes are able to transmit heat to the surface and to generate a transient incremental heat flow better than the mass transfer occurring typically when fluids from different reservoirs mix

Exchange-coupling constants, spin density map, and Q dependence of the inelastic neutron scattering intensity in single-molecule magnets

The Q dependence of the inelastic neutron scattering (INS) intensity of transitions within the ground-state spin multiplet of single-molecule magnets (SMMs) is considered. For these transitions, the Q dependence is related to the spin density map in the ground state, which in turn is governed by the Heisenberg exchange interactions in the cluster. This provides the possibility to infer the exchange-coupling constants from the Q dependence of the INS transitions within the spin ground state. The potential of this strategy is explored for the M = +-10 -> +- 9 transition within the S = 10 multiplet of the molecule Mn12 as an example. The Q dependence is calculated for powder as well as single-crystal Mn12 samples for various exchange-coupling situations discussed in the literature. The results are compared to literature data on a powder sample of Mn12 and to measurements on an oriented array of about 500 single-crystals of Mn12. The calculated Q dependence exhibits significant variation with the exchange-coupling constants, in particular for a single-crystal sample, but the experimental findings did not permit an unambiguous determination. However, although challenging, suitable experiments are within the reach of today's instruments.Comment: 11 pages, 6 figures, REVTEX4, to appear in PR

Field dependent anisotropy change in a supramolecular Mn(II)-[3x3] grid

The magnetic anisotropy of a novel Mn(II)-[3x3] grid complex was investigated by means of high-field torque magnetometry. Torque vs. field curves at low temperatures demonstrate a ground state with S > 0 and exhibit a torque step due to a field induced level-crossing at B* \approx 7.5 T, accompanied by an abrupt change of magnetic anisotropy from easy-axis to hard-axis type. These observations are discussed in terms of a spin Hamiltonian formalism.Comment: 4 pages, 4 figures, to be published in Phys. Rev. Let

High-field Electron Spin Resonance of Cu_{1-x}Zn_{x}GeO_{3}

High-Field Electron Spin Resonance measurements were made on powder samples of Cu_{1-x}Zn_{x}GeO_{3} (x=0.00, 0.01, 0.02, 0.03 and 0.05) at different frequencies (95, 110, 190, 220, 330 and 440 GHz) at low temperatures. The spectra of the doped samples show resonances whose positions are dependent on Zn concentration, frequency and temperature. The analysis of intensity variation of these lines with temperature allows us to identify them as originating in transitions within states situated inside the Spin Peierls gap. A qualitative explanation of the details of the spectra is possible if we assume that these states in the gap are associated with "loose" spins created near the Zn impurities, as recently theoreticaly predicted. A new phenomenon of quenching of the ESR signal across the Dimerized to Incommensurate phase-boundary is observed.Comment: 4 pages, 5 ps figures in the text, submitted to Phys. Rev. Let

Experimental study of CO2 sequestration by ECBM recovery: the case of Sulcis coal.

An ECBM (Enhanced Coal Bed Methane) feasibility study started for the Sulcis Coal Province (SW Sardinia, Italy) in December 2004: geochemical, structural-geology, stratigraphic and reservoir engineering considerations are discussed. The first newly gathered experimental data are discussed, including: fluid geochemistry (major and minor elements, dissolved gases, C and He isotopic ratios) of the reservoir, coal composition and experimental data on CO2/CH4 adsorption on coal. A MapInfo GIS structure was built up including stratigraphical, geo-structural, hydrogeochemical, coal-compositional and environmental impact information as well as the CO2 sources location and typology. Even if these data could be preliminary with respect to the coal characteritics effectively located at the future injection depth, they highlighted both the challenging positive and negative aspects of the Sulcis Coal Province versus the exploitation of the ECBM technique. The most important objective of this phase I of the project is the selection of the best Sulcis ECBM test-pilot site, which will be followed (Phase II) by the choice of a scaled up site and possibly by a future network (Phase III). These phases are foreseen to be accompanied by the selection of progressively added CO2 industrial sources, to be used within the project economic spreadsheet model, actually in evolution. CO2 geological storage and CH4 production potentials in Sulcis have been grossly evaluated as a whole, in the frame of the Sardinia region CO2 sources, including the coal-fired power plants, both existent and foreseen (hundreds of millions of tonns of CO2 are possible to be stored underground in the next decades). The reservoir estimates, both for the CO2 injection and for the CH4 production are clearly involving to start the test-site phase exploitation, in the frame of an auspicabile international operative project