Ethyl 2‐methoxy‐6‐[(triphenylphosphoranylidene)amino]nicotinate and ethyl 2‐methylsulfanyl‐6‐[(triphenylphosphoranylidene)amino]nicotinate

The molecules of ethyl 2‐methoxy‐6‐[(triphenylphosphoranylidene)amino]nicotinate, C₂₇H₂₅N₂O₃P, (I), and ethyl 2‐methylsulfanyl‐6‐[(triphenylphosphoranylidene)amino]nicotinate, C₂₇H₂₅N₂O₂PS, (II), have almost identical bond lengths and molecular conformations, and both show evidence for polarized electronic structures. However, the crystal structures, as illustrated by the weak hydrogen bonds linking the molecules, are significantly different. The significance of this study lies in the observation that two compounds which are almost identical in constitution, configuration and conformation nonetheless adopt different crystal structures.     

Perturbative quantum gravity in analogy with Fermi theory of weak interactions using bosonic tensor fields

In this paper we work in perturbative quantum gravity and we introduce a new effective model for gravity. Expanding the Einstein–Hilbert Lagrangian in graviton field powers we have an infinite number of terms. In this paper we study the possibility of an interpretation of more than three graviton interacting vertices as effective vertices of a most fundamental theory that contain tensor fields. Here we introduce a Lagrangian model named I.T.B. (intermediate-tensor-boson) where four gravitational pseudo-currents that contain two gravitons couple to three massive tensorial fields of ranks one, three and five, respectively. We show that the exchange of those massive particles reproduces, at low energy, the interacting vertices for four or more gravitons. In a particular version, the model contains a dimensionless coupling constant g and the mass M of the intermediate bosons as free parameters. The universal gravitational constant G_N is shown to be proportional to the inverse of mass squared of mediator fields, particularly . A foresighting choice of the dimensionless coupling constant could lower the energy scale where quantum gravity aspects show up.     

Dinuclear (Fe(II), Gd(III)) complexes deriving from hexadentate Schiff bases: synthesis,structure, and Mössbauer and magnetic properties

The dinuclear (Fe(II), Gd(III)) complexes studied in this report derive from hexadentate Schiff base ligands abbreviated H(2)L(i)() (i = 1, 2, 3). H(2)L(1) = N,N'-bis(3-methoxysalicylidene)-1,3-diamino-2,2'-dimethyl-propane, H(2)L(2) = N,N'-bis(3-methoxysalicylidene)-1,2-diamino-2-methylpropane, and H(2)L(3) = N,N'-bis(3-methoxysalicylidene)-1,2-diaminoethane. The crystal and molecular structures of three complexes have been determined at 160 K. Depending on the solvent used in the preparation, L(1)Fe(CH(3)OH)Gd(NO(3))(3)(CH(3)OH)(2), 1, or L(1)Fe((CH(3))(2)CO)Gd(NO(3))(3), 1', is obtained from H(2)L(1). A similar complex, L(2)Fe((CH(3))(2)CO)Gd(NO(3))(3), 2, is obtained from H(2)L(2). Complex 1 crystallizes in the orthorhombic space group Pca2(1) (No. 29): a = 22.141(3) A, b = 9.4159(16) A, c = 15.2075(17) A, V = 3170.4(7) A(3), Z = 4. Complexes 1' and 2 crystallize in the monoclinic space group P2(1)/c (No. 14): 1', a = 9.6264(17) A, b = 19.662(3) A, c = 16.039(3) A, beta = 95.15(2) degrees, V = 3023.6(9) A(3), Z = 4; 2, a = 9.7821(13) A, b = 18.7725(17) A, c = 16.100(2) A, beta = 96.497(16) degrees, V = 2937.5(6) A(3), Z = 4. Complexes 1, 1', and 2 possess an Fe(O(phenoxo))(2-)Gd core. The mononuclear L(3)Fe complex could be prepared from H(2)L(3) but not the related dinuclear (Fe, Gd) species. M?ssbauer spectroscopy evidences that the iron center is in the +2 oxidation state for the six complexes. The experimental magnetic susceptibility and magnetization data of complexes 1, 1', and 2 indicate the occurrence of weak Fe(II)-Gd(III) ferromagnetic interactions. Single ion zero-field splitting of the iron(II) must be taken into account for satisfactorily fitting the data by exact calculation of the energy levels associated to the spin Hamiltonian through diagonalization of the full matrix for axial symmetry (1, J = 0.50 cm(-1), D = 2.06 cm(-1); 1', J = 0.41 cm(-1), D = 3.22 cm(-1); 2, J = 0.08 cm(-1), D = 4.43 cm(-1)).     

Shear and squeeze rheometry of suspensions of magnetic polymerized chains

We present the first experimental results on the magnetorheology of suspensions of non-Brownian magnetic ellipsoidal particles. These particles are made of spherical iron particles linked by polymers and are called polymerized chains. Steady shear, oscillatory shear, and oscillatory squeeze rheological tests have been performed. The rheological properties of the suspension of polymerized chains have been compared with those of the suspension of spherical iron particles. In shear flow, both suspensions develop nearly the same yield stress, while in squeeze flow, the yield stress is several times higher for the suspension of polymerized chains. We show that the squeezing force of a suspension of spherical particles is an increasing function of the magnetic field intensity at low magnetic fields but decreases dramatically at higher fields. Surprisingly, this phenomenon, attributed to cavitation or air entrainment, does not occur in the suspension of polymerized chains.     

Electrochemical Nanobiosensors as Point-of-Care Testing Solution to Cytokines Measurement Limitations

Most cytokines are present at reduced amounts in body fluids due to their biological features of production, release, and action mechanisms. The required time between sampling and their measurement is critical for diagnosis and treatment. Electrochemical nanobiosensors offer the possibility to be tailor-made and cost affordable, producing direct and rapid readouts with low sample volume, explaining their feasibility in timely measurements and potential in designing unique and multiplexed Point-Of-Care (POC) testing platforms. This review summarizes and discusses the measurement limitations of the standard methods and the recent progress on electrochemical nanobiosensors as a plausible alternative to measuring them.     

Analysis of metals and phosphorus in biodiesel B100 from different feedstock using a Flow Blurring multinebulizer in inductively coupled plasma-optical emission spectrometry

A simple and fast method for determining the content of Na, K, Ca, Mg, P, and 20 heavy metals in biodiesel samples with inductively coupled plasma optical emission spectrometry (ICP OES) using a two-nozzle Flow Blurring^® multinebulizer prototype and on-line internal standard calibration, are proposed. The biodiesel samples were produced from different feedstock such as sunflower, corn, soybean and grape seed oils, via a base catalyst transesterification. The analysis was carried out without any sample pretreatment. The standards and samples were introduced through one of the multinebulizer nozzles, while the aqueous solution containing yttrium as an internal standard was introduced through the second nozzle. Thus, the spectral interferences were compensated and the formation of carbon deposits on the ICP torch was prevented. The determination coefficients (R²) were greater than 0.99 for the studied analytes, in the range 0.21–14.75 mg kg⁻¹. Short-term and long-term precisions were estimated as relative standard deviation. These were acceptable, their values being lower than 10%. The LOQ for major components such as Ca, K, Mg, Na, and P, were within a range between 4.9 ng g⁻¹ for Mg (279.553 nm) and 531.1 ng g⁻¹ for Na (588.995 nm), and for the other 20 minor components they were within a range between 1.1 ng g⁻¹ for Ba (455.403 nm) and 2913.9 ng g⁻¹ for Pb (220.353 nm). Recovery values ranged between 95% and 106%.     

Highly efficient catalytic microengines: template electrosynthesis of polyaniline/platinum microtubes

Highly efficient catalytic microtubular engines are synthesized rapidly and inexpensively using an electrochemical growth of bilayer polyaniline/platinum microtubes within the conically shaped pores of a polycarbonate template membrane. These mass-produced microtubular engines are only 8 μm long, are self-propelled at an ultrafast speed (of over 350 body lengths s(-1)), and can operate in very low levels of the hydrogen peroxide fuel (down to 0.2%). The propulsion characteristics and optimization of these microtubular engines are described, along with their efficient operation in different biological environments which holds great promise for biomedical applications.     

Laser spectroscopy of nuclear reaction products: recent results and future prospects

Laser spectroscopic observations of nuclear reaction products produced with intensities of less than 10⁴ atoms/second are now possible with several different methods. We describe the recoil into gas method which has recently been successful. This method is not Dopplerfree, but can give reasonable spectra if the resolution requirements of the spectra are not too high. It has the great advantage that it very efficiently uses the atoms, and spectra have been observed with primary production rates of less than 10³ atoms/sec. Our recent work has concentrated on developing the recoil into gas method for the refractory element Hf. In order that the atoms could be cycled to produce many fluorescence photons, nitrogen and hydrogen impurity gases were added to the argon buffer gas to quench metastable levels to the ground state. In this way spectra could be obtained with fluxes of 10⁴ atoms/second. Future prospects for trapping radioactive atoms in a magneto-optic trap will be discussed.