Dichloromethylation of enones by carbon nitride photocatalysis

Small organic radicals are ubiquitous intermediates in photocatalysis and are used in organic synthesis to install functional groups and to tune electronic properties and pharmacokinetic parameters of the final molecule. Development of new methods to generate small organic radicals with added functionality can further extend the utility of photocatalysis for synthetic needs. Herein, we present a method to generate dichloromethyl radicals from chloroform using a heterogeneous potassium poly(heptazine imide) (K-PHI) photocatalyst under visible light irradiation for C1-extension of the enone backbone. The method is applied on 15 enones, with γ,γ-dichloroketones yields of 18–89%. Due to negative zeta-potential (−40 mV) and small particle size (100 nm) K-PHI suspension is used in quasi-homogeneous flow-photoreactor increasing the productivity by 19 times compared to the batch approach. The resulting γ,γ-dichloroketones, are used as bifunctional building blocks to access value-added organic compounds such as substituted furans and pyrroles

Energy and Structure of Hard-Sphere Bose Gases in three and two dimensions

The energy and structure of dilute gases of hard spheres in three dimensions is discussed, together with some aspects of the corresponding 2D systems. A variational approach in the framework of the Hypernetted Chain Equations (HNC) is used starting from a Jastrow wavefunction that is optimized to produce the best two--body correlation factor with the appropriate long range. Relevant quantities describing static properties of the system are studied as a function of the gas parameter $x=\rho a^d$ where $\rho$, $a$ and $d$ are the density, $s$--wave scattering length of the potential and dimensionality of the space, respectively. The occurrence of a maximum in the radial distribution function and in the momentum distribution is a natural effect of the correlations when $x$ increases. Some aspects of the asymptotic behavior of the functions characterizing the structure of the systems are also investigated.Comment: Proceedings of the QFS2004 conference in Trento. To appear in JLT

Evaluation Under Grazing of Two Festuca Arundinacia Cultivars with Contrasting Growth Patterns

Two cultivars of Festuca arundinacea, one of temperate origin (El Palenque: PAL) with higher spring and summer growth and one of North African origin (Maris Kasba: MK) with higher winter growth, were compared under grazing during three years. They were grazed continuously, using a “put and take” system, by young steers and the swards maintained at equal heights, but which varied slightly between seasons. Daily live weight gain (LWG) and instantaneous stocking rate (ISR) were used to estimate productivity per unit area. There was no difference between cultivars in LWG, but consistent and important differences in ISR: MK carrying and producing nearly 50% more steers/ha in winter than PAL, while in spring-summer PAL carried nearly 40% more. This strong interaction between cultivar and period meant that overall production on the two was similar

The Effect of Different Oversown Legume Species and Row Spacings Upon the Production of Degraded Cultivated Pastures

The establishment and growth of three leguminous plants Medicago sativa (A), Trifolium pratense (TR) and Lotus corniculatus (LC) was analysed. They were oversown on three different row spacings (10, 20 y 40 cm) on September 12, 1994. Density was estimated by marking and sequential counting of seedlings. Growth was estimated from Leaf Area Index (LAI) and from forage accumulation per area unit on three dates: D1 = 26/01/95; D2 = 11/04/95; D3 = 5/12/95. Total forage accumulation was higher (p\u3c0.05) for the treatments oversown with TR in D1 at the smaller distances (average from 10 and 20 cm, 4130 kg DM/ha, 46% higher than treatment control (C); all the other treatments did not differ from C). In D2 there were no differences between treatments (average 1995 kg DM/ha); in D3 there were no differences among the oversown treatments (average 2498 kg DM/ha) and forage accumulation was 59% higher than C. There was no difference in seedling density between oversown legumes A and TR but both were higher (p\u3c0.05) than that of LC. The relationship between the LAI of the oversown legume and that of the vegetation present was higher (p\u3c0.05) for TR than for the rest of the treatments: D1, TR=1.43, A=0.21, LC=0.1; D2, TR=1.62, A=0.31, LC=0.2 and D3, TR=1.91, A=0.86, LC=1.05 . It is concluded that it is feasible to increase yield and modify botanical composition of degraded pastures by oversowing legumes

Gating of L-type Ca2+ channels in embryonic chick ventricle cells: dependence on voltage, current and channel density

1. L-type calcium channels in embryonic chick heart ventricle have voltage-dependent, time-variant kinetics when they conduct inward currents carried by 20 mM-Ba2+. Depolarizing the membrane from -20 to 20 mV increases mean open time from 1.4 to 4.2 ms. Mean open time increases monotonically with voltage. The single-channel conductance, 18 +/- 2 pS, is approximately linear over this voltage range, and the extrapolated reversal potential is 38 +/- 5 mV. 2. In cell-attached patches with five or more L-type Ca2+ channels in the patch, the currents elicited by 500 ms depolarizing steps, from a -80 mV holding potential, inactivate rapidly and have large tail currents. In the same patch, currents from a -40 mV holding potential are smaller, inactivate more slowly, and have practically no tail currents. 3. In cell-attached patches containing one of two L-type Ca2+ channels, currents from -80 or -40 mV are virtually identical, and they are similar to the currents from multichannel patches held at -40 mV. 4. The voltage-dependent, time-variant kinetics of individual L-type Ca2+ channels are unaltered if the patch is removed from the cell and forms an inside-out configuration. In these experiments the internal membrane was bathed with an artificial, intracellular-like solution containing no phosphorylating enzymes or substrates. 5. Cells bathed in 20 mM-Ba2+ solutions and held at -80 mV have currents with an early phase that inactivates in tens of milliseconds, a late phase that inactivates in hundreds of milliseconds, and a large, slow tail current. Currents from -40 mV have only the late phase and practically no tails. However, if the maximum current is less than 0.1 pA pF-1, records from either -80 or -40 mV are virtually identical, and they are similar to currents from cells with higher channel density held at -40 mV. Furthermore, if cells are stimulated before full recovery from inactivation, the reduced current is accompanied by slower inactivation. 6. Whole-cell currents in 1.5 mM-Ca2+ solutions are entirely abolished by addition of 20 microM-nifedipine, and they are enhanced 2-3 times by addition of 30 microM-cyclic AMP and 3 mM-ATP to the whole-cell recording electrode. The whole-cell currents in 20 mM-Ba2+ solutions are also completely blocked by 20 microM-nifedipine, regardless of kinetics or holding potential. Thus, by definition, the cells we are studying contain only L-type channels

Martensitic Thin Wires under Restrained Recovery: Theoretical and Experimental Aspects

A one-dimensional model for the evolution of microstructure in single crystal shape memory wires has been recently proposed in (Rizzoni (2011)). The model is based on the constrained theory of martensite introduced by (Ball et al. (1995); De Simone and James (2002)) and on the assumption that stable equilibrium configurations are deformations lying at the energy wells on most parts of the wire. In this paper we compare the response simulated for restrained recovery conditions (Rizzoni (2011)) with experimental data obtained in restrained recovery tests performed on NiTi wires. As an application, we consider a truss made of shape memory wires and rigid elements, and we calculate its deformation after thermal activation of the shape recovery

Fertilizer Nitrogen and Morphogenetic Response in Avena Sativa and Lolium Multiflorum

A field experiment was carried out at the EEA Balcarce, INTA, Argentina (37° 45’LS, 58° 18’LW) to determine whether Leaf Appearance Rate (LAR) was affected by N fertilization in Italian ryegrass (Lolium multiflorum Lam.) and forage oats (Avena sativa). N treatments (0, 50, 100, 150, 200 and 250 kg N ha-1) were applied in winter 1995, after a defoliation. Subsequently, number of leaves per tiller was determined on 45 labelled tillers in each treatment twice a week. LAR was calculated as the slope of the linear regression of number of leaves on thermal time (air temperature, base 0 °C). Leaf appearance was more rapid with N fertilization in ryegrass, but was not in oats. In situations in which N applied did not affect LAR similar phyllochrons of 112 (± 4,6) and 113 (± 3,6) GDD leaf1 were found for Italian ryegrass and oats, respectively