Influence of the Polarity of the Electric Field on Electrorheometry

Uniaxial extensional flow is a canonical flow typically used in rheological characterization to provide complementary information to that obtained by imposing simple shear flow. In spite of the importance of having a full rheological characterization of complex fluids, publications on the rheological characterization of mobile liquids under extensional flow have increased significantly only in the last 20 years. In the case of the rheological characterization of electrorheological fluids, the situation is even more dramatic, as the ERFs have been exclusively determined under simple shear flow, where an electrorheological cell is attached to the rotational rheometer generating an electric field perpendicular to the flow direction and that does not allow for inverting the polarity. The very recent work published by Sadek et al., who developed a new electrorheological cell to be used with the commercial Capillary Breakup Extensional Rheometer (CaBER), allows for the very first time performing electrorheometry under extensional flow. By means of the same experimental setup, this study investigates the influence of the polarity of the imposed electric field on the filament thinning process of a Newtonian and an electrorheological fluid. Results show that a polarity against the gravity results in filament thinning processes that live longer or reach a stable configuration at lower intensities of the applied electric field

Structure and genetic diversity in wild and cultivated populations of Zapote mamey (Pouteria sapota, Sapotaceae) from southeastern Mexico: its putative domestication center

Tropical fruit trees are an important component of the human diet; however, little is known about their genetic diversity levels. Zapote mamey (Pouteria sapota) is a tree native to southeastern Mexico and Central America, and Mexico is the leading producer in the world. Studies of the genetic diversity of Zapote mamey have been based on cultivated materials using morphological and biochemical characterization or dominant molecular markers. To gain a deeper understanding about the conservation status of Zapote mamey in its center of origin and domestication, we collected 188 individuals from eight wild and five cultivated populations in southeastern Mexico and characterized them using eight microsatellite loci. STRUCTURE, 3D-PCoA, and neighbor-joining analyses showed three groups in the wild gene pool and one group in the cultivated gene pool. FST values were significant between wild and cultivated gene pools, among the four groups observed and among the 13 populations collected (0.13, 0.25, and 0.36, respectively). Overall, we found low levels of genetic diversity (A = 2.77, HO = 0.29, HE = 0.39), permutation tests did not show significant differences between wild and cultivated gene pools. The Garza–Williamson index showed low values in both gene pools (wild = 0.16, cultivated = 0.11) and the Bottleneck program indicated a decrease in genetic diversity in both gene pools (wild, P = 0.027; cultivated, P = 0.054); both analyses suggest a potential genetic bottleneck within this species. This study can help to generate adequate sampling techniques and to develop effective management strategies for Zapote mamey of southeastern Mexico

Beyond conventional factorization: Non-Hermitian Hamiltonians with radial oscillator spectrum

The eigenvalue problem of the spherically symmetric oscillator Hamiltonian is revisited in the context of canonical raising and lowering operators. The Hamiltonian is then factorized in terms of two not mutually adjoint factorizing operators which, in turn, give rise to a non-Hermitian radial Hamiltonian. The set of eigenvalues of this new Hamiltonian is exactly the same as the energy spectrum of the radial oscillator and the new square-integrable eigenfunctions are complex Darboux-deformations of the associated Laguerre polynomials.Comment: 13 pages, 7 figure

Porous Titanium surfaces to control bacteria growth: mechanical properties and sulfonated polyetheretherketone coating as antibiofounling approaches

Here, titanium porous substrates were fabricated by a space holder technique. The relationship between microstructural characteristics (pore equivalent diameter, mean free-path between pores, roughness and contact surface), mechanical properties (Young’s modulus, yield strength and dynamic micro-hardness) and bacterial behavior are discussed. The bacterial strains evaluated are often found on dental implants: Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa. The colony-forming units increased with the size of the spacer for both types of studied strains. An antibiofouling synthetic coating based on a sulfonated polyetheretherketone polymer revealed an effective chemical surface modification for inhibiting MRSA adhesion and growth. These findings collectively suggest that porous titanium implants designed with a pore size of 100–200 µm can be considered most suitable, assuring the best biomechanical and bifunctional anti-bacterial properties.University of Seville VI Plan Propio de Investigación y Transferencia—US 2018, I.3A

Scalar field in the Bianchi I: Non commutative classical and Quantum Cosmology

Using the ADM formalism in the minisuperspace, we obtain the commutative and noncommutative exact classical solutions and exact wave function to the Wheeler-DeWitt equation with an arbitrary factor ordering, for the anisotropic Bianchi type I cosmological model, coupled to a scalar field, cosmological term and barotropic perfect fluid. We introduce noncommutative scale factors, considering that all minisuperspace variables $\rm q^i$ do not commute, so the symplectic structure was modified. In the classical regime, it is shown that the anisotropic parameter $\rm \beta_{\pm nc}$ and the field $\phi$, for some value in the $\lambda_{eff}$ cosmological term and noncommutative $\theta$ parameter, present a dynamical isotropization up to a critical cosmic time $t_{c}$; after this time, the effects of isotropization in the noncommutative minisuperspace seems to disappear. In the quantum regimen, the probability density presents a new structure that corresponds to the value of the noncommutativity parameter.Comment: 17 pages, 6 figures, Acepted in IJT

Rapid method for radiostrontium determination in milk in emergency situations using PS resin

[EN] This study describes a new and rapid procedure for radiostrontium determination in milk samples based on the use of plastic scintillation resins (PS resins). The proposed method reduces the time of analysis by at least 2 h by combining separation and measurement preparation into a single step and optimizing the pre-treatment steps. The method is robust and reproducible, with good total recoveries (65% on average) and a relative bias for total radiostrontium activity (Sr-89 + Sr-90) below 7%. The minimum detectable activity for 100 mL of milk sample measured for 60 min is about 0.34 Bq L-1. The proposed method can quantify radiostrontium content in 5 h, which makes it suitable for use in emergency situations.The authors are grateful to the Spanish Ministerio de Economia y Competitividad (MINECO) for financial support, under CTM2014-02020 and the Catalan Agencia de Gestio d'Ajuts Universitaris i de Recerca (AGAUR) for financial support, under 2014-SGR-1277. We should also like to thank the Universitat Politecnica de Valencia for finantial support under the "Programa propio para la Formacion de Personal Investigador (FPI) de la UniversitatPolitecnica de Valencia - Subprograma 100.Sáez-Muñoz, M.; Bagán, H.; Tarancón, A.; García, JF.; Ortiz Moragón, J.; Martorell Alsina, SS. (2018). Rapid method for radiostrontium determination in milk in emergency situations using PS resin. Journal of Radioanalytical and Nuclear Chemistry. 315(3):543-555. https://doi.org/10.1007/s10967-017-5682-3S5435553153International Atomic Energy Agency (2015) The fukushima daiichi accident, technical radiological consequences, vol 4. IAEA, ViennaInternational Atomic Energy Agency (2006) Environmental consequences of the chernobyl accident and their remediation: 20 years of experience, Report of the UN Chernobyl forum expert group “environment”, radiological assessment reports Series No. 8, IAEA, ViennaPovinec PP, Hirose K, Aoyama M (2013) Fukushima accident: radioactivity impact on the environment. Elsevier, ChinaCouncil Regulation (Euratom) 2016/52 of 15 January 2016 laying down maximum permitted levels of radioactive contamination of food and feed following a nuclear accident or any other case of radiological emergency, and repealing regulation (Euratom) No 3954/87 and commission regulations (Euratom) No 944/89 and (Euratom) No 770/90Vajda N, Kim CK (2010) Determination of radiostrontium isotopes: a review of analytical methodology. Appl Radiat Isot 68:2306–2326Brun S, Bessac S, Uridat D, Boursier B (2002) Rapid method for the determination of radiostrontium in milk. J Radioanal Nucl Chem 253(2):191–197Maxwell SL, Culligan BK (2009) Rapid method for determination of radiostrontium in emergency milk samples. J Radioanal Nucl Chem 279(3):757–760Kabai E, Hornung L, Savkin BT, Poppitz-Spuhler A, Hiersche L (2011) Fast method and ultra fast screening for determination of 90Sr in milk and dairy products. Sci Total Environ 410–411:235–240International Atomic Energy Agency (2013) Rapid simultaneous determination of 89Sr and 90Sr in milk: a procedure using cerenkov and scintillation counting, analytical quality in nuclear applications no. IAEA/AQ/27, IAEA, ViennaBagán H, Tarancón A, Rauret G, García JF (2011) Radiostrontium separation and measurement in a single step using plastic scintillators plus selective extractants application to aqueous sample analysis. Anal Chim Acta 686:50–56Barrera J, Tarancón A, Bagán H, García JF (2016) A new plastic scintillation resin for single-step separation, concentration and measurement of technetium-99. Anal Chim Acta 936:259–266Lluch E, Barrera J, Tarancón A, Bagán H, García JF (2016) Analysis of 210Pb in water samples with plastic scintillation resins. Anal Chim Acta 940:38–45Santiago L, Tarancón A, García JF (2016) Influence of preparation parameters on the synthesis of plastic scintillation microspheres and evaluation of sample preparation. Adv Powder Technol 27(4):1309–1317Savitzky A, Golay MJE (1964) Smoothing and differentiation of data by simplified least-squares procedures. Anal Chem 36:1627–1639Currie LA (1968) Limits for qualitative detection and quantitative determination. Application to radiochemistry. Anal Chem 40(3):586–593UNE 34829:1983, Determination of the calcium content of milkISO 12081:2010, IDF 36:2010, Milk—Determination of calcium content—titrimetric methodHeckel A, Vogl K (2009) Rapid method for determination of the activity concentrations of 89Sr and 90Sr. Appl Radiat Isot 67:794–796Kabai E, Savkin B, Mehlsam I, Poppitz-Spuhler A (2017) Combined method for the fast determination of pure beta emitting radioisotopes in food samples. J Radioanal Nucl Chem 311:1401–1408Eikenberg J, Beer H, Rüthi M, Zumsteg I, Vetter A (2005) Precise determination of 89Sr and 90Sr/90Y in various matrices: the LSC 3-window approach. LSC2005 Advances in Liquid Scintillation Spectrometry, Radiocarbon, AZ, pp 237–249Kim CK, Al-Hamwi A, Toervenyi A, Kis-Benedek G, Sansone U (2009) Validation of rapid method for the determination of radiostrontium in milk. Appl Radiat Isot 67:786–79

Generalized Casimir forces in non-equilibrium systems

In the present work we propose a method to determine fluctuation induced forces in non equilibrium systems. These forces are the analogue of the well known Casimir forces, which were originally introduced in Quantum Field theory and later extended to the area of Critical Phenomena. The procedure starts from the observation that many non equilibrium systems exhibit long-range correlations and the associated structure factors diverge in the long wavelength limit. The introduction of external bodies into such systems in general modifies the spectrum of these fluctuations and leads to the appearance of a net force between these bodies. The mechanism is illustrated by means of a simple example: a reaction diffusion equation with random noises.Comment: Submitted to Europhysics Letters. 7 pages, 2 figure