Application of classical thermodynamics to the conductivity in non-polar media.

Electrical conductivity in non-polar media is a subject which recently regained interest. If most of experiments and theoretical developments were done more than 50 years ago, new experiments and theories have been recently published. As the electrical conductivity describes, at low field, the equilibrium state of a system, it is natural to apply theories based on equilibrium thermodynamics. In this article, well-established classical thermodynamics and solvations models are applied to recently published data. This enables to get a new insight in intriguing phenomena, such as the linear dependence of the conductivity on the concentration of ionic surfactant and the evaluation of conductivity for the mixture of two miscible fluids, such as alcohol and alcane, which have very different conductivities.

Onsager's reciprocal relations for electroacoustic and sedimentation: Application to (concentrated) colloidal suspensions.

In this article, the relations for electroacoustic phenomena, such as sedimentation potential, sedimentation intensity, colloid vibration potential, colloid vibration intensity/current, or electric sonic amplitude, are given, on the basis of irreversible thermodynamics. This formalism allows in particular to discuss the different expressions for concentrated suspensions found by various authors, which are of great practical interest. It was found that some existing expressions have to be corrected. Relations between the electrophoretic mobilities assessed by the different experiments are derived.

Onsager's reciprocal relations in electrolyte solutions. I. Sedimentation and electroacoustics.

In the framework of irreversible thermodynamics, we show that the sedimentation current in electrolyte solutions is mathematically equivalent to the low frequency limit of the ionic vibration current, appearing in the presence of an acoustic wave. This non-trivial result is obtained thanks to a careful choice of the reference frame used to express the mass fluxes in the context of electroacoustics. Coupled transport phenomena in electrolyte solutions can also be investigated in a mechanical framework, with a set of Newtonian equations for the dynamics of charged solutes. Both in the context of sedimentation and of electroacoustics, we show that the results obtained in the mechanical framework, in the ideal case (i.e., without interactions between ions), do satisfy the Onsager's reciprocal relations. We also derive the general relation between corrective forces accounting for ionic interactions which must be fulfilled so that the Onsager's reciprocal relations are verified. Finally, we show that no additional diffusion term needs to be taken into account in the flux of solutes (far from the walls), even if local concentration gradients exist, contrarily to what was done previously in the literature.

Onsager's reciprocal relations in electrolyte solutions. II. Effect of ionic interactions on electroacoustics.

In electrolyte solutions, an electric potential difference, called the Ionic Vibration Potential (IVP), related to the ionic vibration intensity, is generated by the application of an acoustic wave. Several theories based on a mechanical framework have been proposed over the years to predict the IVP for high ionic strengths, in the case where interactions between ions have to be accounted for. In this paper, it is demonstrated that most of these theories are not consistent with Onsager's reciprocal relations. A new expression for the IVP will be presented that does fulfill the Onsager's reciprocal relations. We obtained this expression by deriving general expressions of the corrective forces describing non-ideal effects in electrolyte solutions.

Reciprocal relations in electroacoustics.

In a colloidal suspension, one can generate sound waves by the application of an alternating electric field (Electrokinetic Sonic Amplitude, i.e., ESA). Another phenomenon is electrophoresis (Electrophoretic Mobility, i.e., EM) where a colloidal particle moves relative to the solvent in an electric field. Vice versa one can generate electric fields or electric currents by sound waves (Colloid Vibration Potential/Current, i.e., CVP/CVI). In 1988 and 1990, O'Brien [J. Fluid Mech. 190, 71-86 (1988) and O'Brien, J. Fluid Mech. 212, 81-93 (1990)] derived a reciprocal relation between the proportionality coefficients of the EM and CVI phenomena. In this paper, we will generalize his proof by constructing the relevant entropy production from which the linear force-flux relations follow. General relations are derived for electrolyte solutions, of which colloidal suspensions are a particular case. The relations between CVI, CVP, EM, and ESA are discussed. O'Brien's reciprocal relation then follows as an Onsager relation. The relation is valid for any applied electric field frequency, particle surface charge and particle concentration (even in the presence of particle-particle interactions) provided the system is isotropic.

Preparation and characterization of inorganic radioactive holmium-166 microspheres for internal radionuclide therapy.

Microspheres with high specific activities of radionuclides are very interesting for internal radiotherapy treatments. This work focuses on the formulation and characterization of inorganic microspheres with a high content of holmium and therefore a high specific radioactivity of holmium-166. Two novel formulations of inorganic microspheres were obtained by dispersing solid holmium acetylacetonate microspheres (Ho2(AcAc)3-ms) in NaH2PO4 or NaOH solutions followed by 2 h incubation at room temperature. By exchange of acetylacetonate with phosphate or hydroxyl ions, holmium phosphate microspheres (HoPO4-ms) and holmium hydroxide microspheres (Ho(OH)3-ms) were formed respectively. The inorganic microspheres had a significantly smaller diameter (28.5 ±â€¯4.4 µm (HoPO4-ms) and 25.1 ±â€¯3.5 µm (Ho(OH)3-ms)) than those of Ho2(AcAc)3-ms (32.6 ±â€¯5.2 µm). The weight percentage of holmium-165 in the microspheres increased significantly from 47% (Ho2(AcAc)3-ms) to 55% (HoPO4-ms) and 73% (Ho(OH)3-ms). After preparation of both HoPO4-ms and Ho(OH)3-ms, the stable holmium-165 isotope was partly converted by neutron activation into radioactive holmium-166 to yield radioactive microspheres. High specific activities were achieved ranging from 21.7 to 59.9 MBq/mg (166HoPO4-ms) and from 28.8 to 79.9 MBq/mg (166Ho(OH)3-ms) depending on the neutron activation time. The structure of both microspheres was preserved up to neutron activations of 6 h in a thermal neutron flux of 4.72 × 1016 n m-2 s-1. After activation, both microspheres revealed excellent stability in administration fluids (saline and phosphate buffer) having less than 0.05% of holmium released after 72 h incubation. Finally, the hemocompatibility of these inorganic microspheres was evaluated and it was shown that the microspheres did cause neither hemolysis nor depletion or inhibition of the coagulation factors of the intrinsic blood coagulation pathway meaning that the microspheres have a good hemocompatibility. Overall, this work shows that radioactive inorganic microspheres with high specific activities of holmium-166 can be prepared which potentially can be used for internal radionuclide therapy.

Application of Classical Thermodynamics to Conductivity in Nonpolar Media: Experimental Confirmation.

We previously proposed ( Gourdin-Bertin , S. and Chassagne , C. J. Chem. Phys. 2016 , 144 ( 24) ) a simple theoretical model to account for the evolution of conductivity with dielectric permittivity in nonpolar media. In this article, we validate the theory experimentally for the case of an ionogenic species kept at a constant chemical potential (i.e., in equilibrium with a nondissolved salt, in contrast to previously published conductivity measurements carried out as a function of various fully dissolved salt concentrations). To our knowledge, it is the first time that this type of experiment has been performed explicitly.

Electrically induced anisotropy in a colloidal dispersion of nanospheres as measured by electric birefringence.

Electrically induced birefringence experiments were performed on dispersions consisting of sulfate latex nanospheres of two different sizes and charges dispersed in an electrolyte solution, at various ionic strengths. The induced birefringence was found to have an important contribution increasing as a quadratic power law of the volume fraction of the spheres. This shows that interparticle interactions play a role in the observed birefringence. The data were analyzed, using a theory from Hafkenscheid and Vlieger [Physica 75 (1974) 57], in terms of the changes of the interparticle separations in the directions parallel and perpendicular to the applied electric field.

The molecular biology of heart failure.

In the mammalian heart, the development of cardiac hypertrophy is a common feature that normally precedes all forms of heart failure. This adaptive process involves molecular changes in the myocardium, including the altered expression of several genes encoding proteins for contraction and relaxation. The expression of myosin heavy chain (MHC) and sarcomeric alpha-actin messenger ribonucleic acid (mRNA) changes qualitatively during cardiac hypertrophy; however, their accumulations are not coordinated. Skeletal alpha-actin transcripts accumulate throughout the ventricles and earlier than beta-MHC transcripts, which accumulate primarily around large coronary vessels. Skeletal alpha-actin transcripts also "hyperaccumulate" relative to cardiac alpha-actin mRNA, whose expression does not change. Expression of MHC isomRNA shows an inverse relation; as beta-MHC accumulates, alpha-MHC decreases in abundance. From nuclear run-on assays, we present evidence that the accumulation of these gene products is at least under partial transcriptional control with developmental growth, suggesting that those changes that occur with hypertrophy and heart failure may be primarily transcriptionally regulated. The expression of the mRNA for the calcium-adenosine triphosphate (Ca(2+)-ATPase) of the sarcoplasmic reticulum changes quantitatively with cardiac hypertrophy without the reexpression of a different isoform. The relative mRNA and protein concentrations for this protein diminish with both cardiac hypertrophy and heart failure, a change that may partially explain the delayed relaxation rates seen in hypertrophied and failing hearts.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of laminin alpha2 chain during normal and pathological growth of myocardium in rat and human.

OBJECTIVES: Fibrosis is a classical feature of cardiac hypertrophy. To date changes within the basal lamina during normal and pathological cardiac growth have been poorly investigated. The goal of the present study was to determine if the expression of the muscle specific subunit of merosin (laminin alpha2 chain) together with that of fibronectin (FN) is modified in the diseased human heart. Laminin alpha2 chain expression was also investigated during physiological and pathological cardiac growth in the rat. METHODS: In ten normal human hearts and ten hearts with idiopathic dilated cardiomyopathy (IDCM), the laminin-alpha2 and FN mRNA levels were quantified by slot-blot using total RNA and the protein distribution was analysed using an immunofluorescence approach. In Wistar rats, laminin alpha2 and FN mRNA expression was analyzed using RNase protection assay (RPA) and slot-blot assays. RESULTS: The amount of laminin alpha2 mRNA did not vary in normal and pathological human hearts whereas it was significantly decreased in renovascular hypertensive rats (-20%) P<0.05 versus normal tissue). The amount of fibronectin mRNA increased in IDMC patients (x2, P<0.05 versus normal tissue), but was unchanged in hypertensive rats. A negative correlation was found between the cardiac laminin-alpha2 level and the age of the patients whatever the cardiac status. During postnatal development in the rat, a similar decrease in cardiac laminin-alpha2 level was observed between 3 and 30 weeks of age. Finally, the immunofluorescent approach failed to detect any alteration in laminin alpha2 distribution within the human myocardium. CONCLUSION: These data indicate that an imbalance between myocyte hypertrophy and the level of laminin-alpha2 might contribute to alterations in sarcolemmal properties, which occur during the development of cardiac hypertrophy and its transition to cardiac failure.

A multicenter study of treatment of primary CNS lymphoma.

OBJECTIVE: To characterize the therapeutic variables correlated to outcome in 370 patients with primary CNS lymphoma. METHODS: Planned treatment was radiotherapy (RT) in 98 patients, chemotherapy (CHT) in 32, RT followed by CHT in 36, and CHT followed by RT in 197 patients. High-dose methotrexate (HD-MTX; 1 to 8 g/m2) was used in 169 patients and intrathecal CHT in 109. RESULTS: One hundred sixteen patients are alive (median follow-up 24 months), with a 2-year overall survival of 37%. Patients treated with CHT followed by RT had improved survival with respect to patients treated with RT alone. Patients receiving HD-MTX-based primary CHT survived longer than those treated with other drugs. HD-MTX associated with other cytostatics, in particular HD-cytarabine, produced better results than HD-MTX alone. No correlation between MTX dose and survival was found. In patients receiving HD-MTX, consolidation RT or intrathecal CHT did not improve survival. Age, performance status, lactate dehydrogenase serum level, CSF protein level, site of disease, and use of HD-MTX were all predictors of survival. CONCLUSIONS: Combination CHT-RT is superior to RT alone. Patients treated with primary CHT containing HD-MTX exhibited improved survival. In these patients, the addition of HD-cytarabine was associated with a better survival, whereas intrathecal CHT was not correlated to outcome. RT may be unnecessary in patients achieving complete remission after receiving HD-MTX-based primary CHT.

Tamoxifen and malignant epithelial-nonepithelial tumours of the endometrium: report of six cases and review of the literature.

AIMS: To review the use of tamoxifen in malignant epithelial-nonepithelial tumours of the endometrium. Tamoxifen has been widely used for almost 20 years as adjuvant therapy for breast cancer. Large clinical trials have pointed out that long-term tamoxifen therapy increases the risk of uterine cancers. These tumours include endometrial carcinomas, stromal sarcomas, leiomyosarcomas as well as malignant mixed (epithelial-nonepithelial) tumours. METHODS: We report here six more cases of malignant epithelial-nonepithelial tumours which, in addition to those reported in the literature, makes a total of 36 presented cases. The pathogenesis of such tumours remains unclear, but it has been claimed that unopposed oestrogenic stimulation due to the agonistic effect of tamoxifen might be involved, as in the case of endometrial carcinomas. Pelvic irradiation has also been incriminated, especiallly in women under 55 years of age. RESULTS: Among 21 endometrial malignant epithelial-nonepithelial tumours associated with tamoxifen, seven occurred in women less than 55 years old. Five of them had previous pelvic irradiation. The data from the literature and from our series suggest that tamoxifen might favour the occurrence of malignant epithelial-nonepithelial tumours in women with breast cancer aged over 55 years, whereas in younger women both pelvic irradiation and tamoxifen might participate.

The interpretation of dielectric spectroscopy measurements on silica and hematite sols.

Experimental data on the dielectric response of silica and hematite sols from the literature are interpreted using an analytical theory developed previously (Chassagne, C., Bedeaux, D., and Koper, G. J. M., J. Phys. Chem B105, 11,743 (2001), and Physica A, to be published). The theory is found to correctly predict both the relaxation frequency and the dielectric permittivity enhancement at low frequencies with only one free parameter. This parameter can be the zeta potential or the Stern layer conductance, in the case that the zeta potential is fixed to agree with the electrophoretic mobility measurements.

[Left ventricular hypertrophy: molecular aspects]. / Hypertrophie ventriculaire gauche: aspects moléculaires.

The expression of genes changes during left ventricular hypertrophy. These changes are known as mechanogenic transduction. With respect to the two main contractile proteins, myosin and actin, this is due to a differential expression of their respective multigenic families. Changes of isoform are uncoordinated in time and space. It is important to recognise that the genes themselves are normal and that it is their regulation which is disturbed. Recent data shows that, under normal conditions, the regulation occurs at the transcription stage. A fuller understanding of these mechanisms is necessary if we are to comprehend the pathogenesis of cardiac hypertrophy and failure.

[Molecular bases of cardiac aging]. / Bases moléculaires du vieillissement cardiaque.

The total volume occupied by myocytes in the heart decreases with age, and this is accompanied by a loss of myocytes, by hypertrophy and, to a lesser extent, by hyperplasia of the remaining myocytes. There are differences between ventricles: the right ventricular myocytes have a greater capacity for replication than those of the left ventricle. The expression of genes coding for the 2 principal contractile proteins (myosin and actin) is modified, and there are strong resemblances between the phenotype of the aged heart and that of an adult heart with haemodynamic overload.

Comparison between the electrokinetic properties of kaolinite and montmorillonite suspensions at different volume fractions.

We have investigated the electrokinetic responses of two different kinds of clay particles, kaolinite and montmorillonite. The dielectric permittivity of kaolinite suspensions is linearly proportional to volume fraction up to volume fractions of 20%, whereas that of montmorillonite is deviating from a linear relationship, for volume fractions below 0.5%. This indicates that the montmorillonite particles experience a particle-particle interaction at these low volume fractions. The complex dipole coefficients of both clays estimated by experimental data are, however, within experimental error in good approximation independent on volume fraction and agree with the theoretical predictions. The relaxation frequency in clay-water system at low ionic strength is almost determined by the relaxation of the double layer for both kaolinite and montmorillonite. For volume fractions larger than 0.5% for montmorillonite, we find that the zeta potential measured by electroacoustic methods starts to depend strongly on volume fraction. It is expected that for these high volume fractions, the dipole coefficients will also become volume-fraction dependent.

Dielectric and electrophoretic response of montmorillonite particles as function of ionic strength.

Montmorillonite is a sheet-like clay mineral. The surface charge of the faces is always negative, whereas the surface charges of the edges depend on pH. In this study, pH is around 6.5 implying that the edges are slightly positive; however, the overall charge of the particle appears to be negative as the surface of the faces is 50 times larger than the edges. In the presence of an applied electric field, montmorillonite particles and their double layer will polarize. This polarization affects the electrokinetic response of the particles. In this article, we investigated the effect of ionic strength on the electrokinetic response of montmorillonite particles using the dielectric spectroscopy and electrophoretic mobility. The experimental dipole coefficient found by dielectric spectroscopy was compared to the semi-analytical formula presented by Chassagne [C. Chassagne, J. Colloid Interface Sci. 326 (2008)]. The amplitude of the dipole coefficient of montmorillonite particles increased and the relaxation frequency shifted to lower frequencies with decreasing ionic strength. This tendency is in qualitative agreement with the theoretical prediction. A better agreement between the experimental and theoretical amplitudes of the dipole coefficient and between the high-frequency experimental and theoretical mobilities was obtained when a Stern layer conductivity is introduced. The same values for the zeta potential and Stern layer conductivities were used in both measurement sets. The relaxation frequencies were not changed by addition of a Stern layer. This discrepancy between experimental and theoretical relaxation frequencies are due to the limitation of the theory that is not valid at low κa, as discussed in the conclusion.

Electrokinetic study of kaolinite suspensions.

In this article a new formula for the electrophoretic mobility of a spheroidal colloid is given. This formula and the formula presented in Chassagne and Bedeaux [C. Chassagne, D. Bedeaux, J. Colloid Interface Sci. 326 (2008) 240-253] for the dipolar coefficient of a spheroidal colloid are intertwined. The combination of electrophoresis and complex conductivity measurements (from which the dipolar coefficient can be derived) allows to assess both the zeta potential and the Stern layer conductance. We will in particular show that the values found for the zeta potential from both techniques are similar in the case of the kaolinite suspension studied. Electrophoretic mobility data are also presented and discussed for a wide range of ionic strengths, different types of salt and various pH. This data has been used in flocculation studies on the same kaolinite samples [F. Mietta, C. Chassagne, J.C. Winterwerp, J. Colloid Interface Sci., accepted for publication, doi:10.1016/j.jcis.2009.03.044].

Shear-induced flocculation of a suspension of kaolinite as function of pH and salt concentration.

The relation between the electrokinetic charge of kaolinite particles and their flocculation behavior has been investigated over a wide range of pH and added salt (for MgCl(2) and NaCl salts). All flocculation experiments have been done with a mixing jar (sediment volume concentration phi=3.84x10(-5)). The electrokinetic charge of particles in different suspensions has been assessed by electrophoresis while laser diffraction has been used to measure the floc size distribution. Mixing jar experiments can be successfully used to investigate the flocculation behavior of kaolinite at shear rates higher than or equal to G=35 s(-1), which is the shear rate used in the experiments. At lower shear rates, the floc size distribution is affected by particle settling. The electrophoretic mobility of kaolinite decreases in absolute value when the pH of the suspension decreases. This is reflected in an increase of both floc size and flocculation rate: the floc size at pH 4 is three times larger than at pH 7 and the flocculation time is one order of magnitude smaller (from 1000 to 100 min). When the ionic strength of the suspension is increased, the electrophoretic mobility and the mean floc size display the same variations. On addition of NaCl (pH 9) both the electrophoretic mobility and the floc size display an optimum around 1 mM of added salt, a feature that has been observed by other authors as well. The equilibrium floc size for a suspension (A) at 1 M of added NaCl and pH 9 is the same as for a suspension (B) at pH 2 with no added salt. However, the time needed to reach the equilibrium for suspension (A) is one order of magnitude larger than for suspension (B). This is due to edge-face Coulombic attraction in suspension (B). The equilibrium floc size obtained by addition of MgCl(2) or sea salt at pH 9 is similar to the size obtained by addition of NaCl. The flocculation rate for a suspension with added MgCl(2) is higher than for suspensions with other added salts.